Nuclear receptor related 1 protein (or NURR1) is a protein that is critical to the development and survival of dopamine neurons – the cells in the brain that are affected in Parkinson’s disease.
Given the importance of this protein for the survival of these cells, a lot of research has been conducted on finding activators of NURR1.
In today’s post we will look at this research, discuss the results, and consider issues with regards to using these activators in Parkinson’s disease.
Comet Hale–Bopp. Source: Physics.smu.edu
Back in 1997, 10 days after Comet Hale–Bopp passed perihelion (April 1, 1997 – no joke; perihelion being the the point in the orbit of a comet when it is nearest to the sun) and just two days before golfer Tiger Woods won his first Masters Tournament, some researchers in Stockholm (Sweden) published the results of a study that would have a major impact on our understanding of how to keep dopamine neurons alive.
Dopamine neurons are one group of cells in the brain that are severely affected by Parkinson’s disease. By the time a person begins to exhibit the movement symptoms of the condition, they will have lost 40-60% of the dopamine neurons in a region called the substantia nigra. In the image below, there are two sections of brain – cut on a horizontal plane through the midbrain at the level of the substantia nigra – one displaying a normal compliment of dopamine neurons and the other from a person who passed away with Parkinson’s demonstrating a reduction in this cell population.
The dark pigmented dopamine neurons in the substantia nigra are reduced in the Parkinson’s disease brain (right). Source:Memorangapp
The researchers in Sweden had made an amazing discovery – they had identified a single gene that was critical to the survival of dopamine neurons. When they artificially mutated the section of DNA where this gene lives – an action which resulted in no protein for this gene being produced – they generated genetically engineered mice with no dopamine neurons:
Title: Dopamine neuron agenesis in Nurr1-deficient mice
Authors: Zetterström RH, Solomin L, Jansson L, Hoffer BJ, Olson L, Perlmann T.
Journal: Science. 1997 Apr 11;276(5310):248-50.
The researchers who conducted this study found that the mice with no NURR1 protein exhibited very little movement and did not survive long after birth. And this result was very quickly replicated by other research groups (Click here and here to see examples)
So what was this amazing gene called?
We have previously discussed the powerful antioxidant Resveratrol, and reviewed the research suggesting that it could be beneficial in the context of Parkinson’s disease (Click here to read that post).
I have subsequently been asked by several readers to provide a critique of the Parkinson’s-associated research focused on Resveratrol’s twin sister, Pterostilbene (pronounced ‘Terra-still-bean’).
But quite frankly, I can’t.
Why? Because there is NO peer-reviewed scientific research on Pterostilbene in models of Parkinson’s disease.
In today’s post we will look at what Pterostilbene is, what is known about it, and why we should seriously consider doing some research on this compound (and its cousin Piceatannol) in the context of Parkinson’s disease.
Blue berries are the best natural source of Pterostilbene. Source: Pennington
So this is likely to be the shortest post in SoPD history.
Because there is nothing to talk about.
There is simply no Parkinson’s-related research on the topic of today’s post: Pterostilbene. And that is actually a crying shame, because it is a very interesting compound.
What is Pterostilbene?
Like Resveratrol, Pterostilbene is a stilbenoid.
Stilbenoids are a large class of compounds that share the basic chemical structure of C6-C2-C6:
Resveratrol is a good example of a stilbenoid. Source: Wikipedia
Stilbenoids are phytoalexins (think: plant antibiotics) produced naturally by numerous plants. They are small compounds that become active when the plant is under attack by pathogens, such as bacteria or fungi. Thus, their function is generally considered to part of an anti-microbial/anti-bacterial plant defence system for plants.
The most well-known stilbenoid is resveratrol which grabbed the attention of the research community in a 1997 study when it was found to inhibit tumour growth in particular animal models of cancer:
In October 2015, researchers from Georgetown University announced the results of a small clinical trial that got the Parkinson’s community very excited. The study involved a cancer drug called Nilotinib, and the results were rather spectacular.
What happened next, however, was a bizarre sequence of disagreements over exactly what should happen next and who should be taking the drug forward. This caused delays to subsequent clinical trials and confusion for the entire Parkinson’s community who were so keenly awaiting fresh news about the drug.
Earlier this year, Georgetown University announced their own follow up phase II clinical trial and this week a second phase II clinical trial funded by a group led by the Michael J Fox foundation was initiated.
In todays post we will look at what Nilotinib is, how it apparently works for Parkinson’s disease, what is planned with the new trial, and how it differs from the ongoing Georgetown Phase II trial.
The FDA. Source: Vaporb2b
This week the U.S. Food and Drug Administration (FDA) has given approval for a multi-centre, double-blind, randomised, placebo-controlled Phase IIa clinical trial to be conducted, testing the safety and tolerability of Nilotinib (Tasigna) in Parkinson’s disease.
This is exciting and welcomed news.
What is Nilotinib?
Nilotinib (pronounced ‘nil-ot-in-ib’ and also known by its brand name Tasigna) is a small-molecule tyrosine kinase inhibitor, that has been approved for the treatment of imatinib-resistant chronic myelogenous leukemia (CML).
What does any that mean?
Basically, it is the drug that is used to treat a type of blood cancer (leukemia) when the other drugs have failed. It was approved for treating this cancer by the FDA in 2007.
A new research report looking at the use of cholesterol-reducing drugs and the risk of developing Parkinson’s disease has just been published in the scientific journal Movement disorders.
The results of that study have led to some pretty startling headlines in the media, which have subsequently led to some pretty startled people who are currently taking the medication called statins.
In todays post, we will look at what statins are, what the study found, and discuss what it means for our understanding of Parkinson’s disease.
Cholesterol forming plaques (yellow) in the lining of arteries. Source: Healthguru
Cholesterol gets a lot of bad press.
Whether it’s high and low, the perfect balance of cholesterol in our blood seems to be critical to our overall health and sense of wellbeing. At least that is what we are constantly being told this by media and medical professionals alike.
But ask yourself this: Why? What exactly is cholesterol?
Good question. What is cholesterol?
Cholesterol (from the Greek ‘chole‘- bile and ‘stereos‘ – solid) is a waxy substance that is circulating our bodies. It is generated by the liver, but it is also found in many foods that we eat (for example, meats and egg yolks).
The chemical structure of Cholesterol. Source: Wikipedia
Cholesterol falls into one of three major classes of lipids – those three classes of lipids being Triglycerides, Phospholipids and Steroids (cholesterol is a steroid). Lipids are major components of the cell membranes and thus very important. Given that the name ‘lipids’ comes from the Greek lipos meaning fat, people often think of lipids simply as fats, but fats more accurately fall into just one class of lipids (Triglycerides).
Like many fats though, cholesterol dose not dissolve in water. As a result, it is transported within the blood system encased in a protein structure called a lipoprotein.
The structure of a lipoprotein; the purple C inside represents cholesterol. Source: Wikipedia
Lipoproteins have a very simple classification system based on their density:
- very low density lipoprotein (VLDL)
- low density lipoprotein (LDL)
- intermediate density lipoprotein (IDL)
- high density lipoprotein (HDL).
Now understand that all of these different types of lipoproteins contain cholesterol, but they are carrying it to different locations and this is why some of these are referred to as good and bad.
The first three types of lipoproteins carry newly synthesised cholesterol from the liver to various parts of the body, and thus too much of this activity would be bad as it results in an over supply of cholesterol clogging up different areas, such as the arteries.
LDLs, in particular, carry a lot of cholesterol (with approximately 50% of their contents being cholesterol, compared to only 20-30% in the other lipoproteins), and this is why LDLs are often referred to as ‘bad cholesterol’. High levels of LDLs can result in atherosclerosis (or the build-up of fatty material inside your arteries).
Progressive and painless, atherosclerosis develops as cholesterol silently and slowly accumulates in the wall of the artery, in clumps that are called plaques. White blood cells stream in to digest the LDL cholesterol, but over many years the toxic mess of cholesterol and cells becomes an ever enlarging plaque. If the plaque ever ruptures, it could cause clotting which would lead to a heart attack or stroke.
So yeah, some lipoproteins can be considered bad.
HDLs, on the other hand, collects cholesterol and other lipids from cells around the body and take them back to the liver. And this is why HDLs are sometimes referred to as “good cholesterol” because higher concentrations of HDLs are associated with lower rates of atherosclerosis progression (and hopefully regression).
But why is cholesterol important?
While cholesterol is usually associated with what is floating around in your bloodstream, it is also present (and very necessary) in every cell in your body. It helps to produce cell membranes, hormones, vitamin D, and the bile acids that help you digest fat.
It is particularly important for your brain, which contains approximately 25 percent of the cholesterol in your body. Numerous neurodegenerative conditions are associated with cholesterol disfunction (such as Alzheimer’s disease and Huntington’s disease – Click here for more on this). In addition, low levels of cholesterol is associated with violent behaviour (Click here to read more about this).
Are there any associations between cholesterol and Parkinson’s disease?
The associations between cholesterol and Parkinson’s disease is a topic of much debate. While there have been numerous studies investigating cholesterol levels in blood in people with Parkinson’s disease, the results have not been consistent (Click here for a good review on this topic).
Rather than looking at cholesterol directly, a lot of researchers have chosen to focus on the medication that is used to treat high levels of cholesterol – a class of drugs called statins.
Title: Prospective study of statin use and risk of Parkinson disease.
Authors: Gao X, Simon KC, Schwarzschild MA, Ascherio A.
Journal: Arch Neurol. 2012 Mar;69(3):380-4.
PMID: 22410446 (This article is OPEN ACCESS if you would like to read it)
In this study the researchers conduced a prospective study involving the medical details of 38 192 men and 90 874 women from two huge US databases: the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS).
NHS study was started in 1976 when 121,700 female registered nurses (aged 30 to 55 years) completed a mailed questionnaire. They provided an overview of their medical histories and health-related behaviours. The HPFS study was established in 1986, when 51,529 male health professionals (40 to 75 years) responded to a similar questionnaire. Both the NHS and the HPFS send out follow-up questionnaires every 2 years.
By analysing all of that data, the investigators found 644 cases of Parkinson’s disease (338 women and 306 men). They noticed that the risk of Parkinson’s disease was approximately 25% lower among people currently taking statins when compared to people not using statins. And this association was significant in statin users younger than 60 years of age (P = 0.02).
What are statins?
Also known as HMG-CoA reductase inhibitors, statins are a class of drug that inhibits/blocks an enzyme called 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase.
HMG-CoA reductase is the key enzyme regulating the production of cholesterol from mevalonic acid in the liver. By blocking this process statins help lower the total amount of cholesterol available in your bloodstream.
Statins are used to treat hypercholesterolemia (also called dyslipidemia) which is high levels of cholesterol in the blood. And they are one of the most widely prescribed classes of drugs currently available, with approximately 23 percent of adults in the US report using statin medications (Source).
Now, while the study above found an interesting association between statin use and a lower risk of Parkinson’s disease, the other research published on this topic has not been very consistent. In fact, a review in 2009 found a significant associations between statin use and lower risk of Parkinson’s disease was observed in only two out of five prospective studies (Click here to see that review).
New research published this week has attempted to clear up some of that inconsistency, by starting with a huge dataset and digging deep into the numbers.
So what new research has been published?
Title: Statins may facilitate Parkinson’s disease: Insight gained from a large, national claims database
Authors: Liu GD, Sterling NW, Kong L, Lewis MM, Mailman RB, Chen H, Leslie D, Huang X
Journal: Movement Disorder, 2017 Jun;32(6):913-917.
Using the MarketScan Commercial Claims and Encounters database which catalogues the healthcare use and medical expenditures of more than 50 million employees and their family members each year, the researcher behind that study identified 30,343,035 individuals that fit their initial criteria (that being “all individuals in the database who had 1 year or more of continuous enrolment during January 1, 2008, to December 31, 2012, and were 40 years of age or older at any time during their enrolment”). From this group, the researcher found a total of 21,599 individuals who had been diagnosed with Parkinson’s disease.
In their initial analysis, the researchers found that Parkinson’s disease was positively associated with age, male gender, hypertension, coronary artery disease, and usage of cholesterol-lowering drugs (both statins and non-statins). The condition was negatively associated with hyperlipidemia (or high levels of cholesterol). This result suggests not only that people with higher levels of cholesterol have a reduced chance of developing Parkinson’s disease, but taking medication to lower cholesterol levels may actually increase ones risk of developing the condition.
One interesting finding in the data was the effect that different types of statins had on the association.
Statins can be classified into two basic groups: water soluble (or hydrophilic) and lipid soluble (or lipophilic) statins. Hydrophilic molecule have more favourable interactions with water than with oil, and vice versa for lipophilic molecules.
Hydrophilic vs lipophilic molecules. Source: Riken
Water soluble (Hydrophilic) statins include statins such as pravastatin and rosuvastatin; while all other available statins (eg. atorvastatin, cerivastatin, fluvastatin, lovastatin and simvastatin) are lipophilic.
In this new study, the researchers found that the association between statin use and increased risk of developing Parkinson’s disease was more pronounced for lipophilic statins (a statistically significant 58% increase – P < 0.0001), compared to hydrophilic statins (a non-significant 19% increase – P = 0.25). One possible explanation for this difference is that lipophilic statins (like simvastatin and atorvastatin) cross the blood-brain barrier more easily and may have more effect on the brain than hydrophilic ones.
The investigators also found that this association was most robust during the initial phase of statin treatment. That is to say, the researchers observed a 82% in risk of PD within 1 year of having started statin treatment, and only a 37% increase five years after starting statin treatment.; P < 0.0001). Given this finding, the investigators questioned whether statins may be playing a facilitatory role in the development of Parkinson’s disease – for example, statins may be “unmasking” the condition during its earliest stages.
So statins are bad then?
Can I answer this question with a diplomatic “I don’t know”?
It is difficult to really answer that question based on the results of just this one study. This is mostly because this new finding is in complete contrast to a lot of experimental research over the last few years which has shown statins to be neuroprotective in many models of Parkinson’s disease. Studies such as this one:
Title: Simvastatin inhibits the activation of p21ras and prevents the loss of dopaminergic neurons in a mouse model of Parkinson’s disease.
Authors: Ghosh A, Roy A, Matras J, Brahmachari S, Gendelman HE, Pahan K.
Journal: J Neurosci. 2009 Oct 28;29(43):13543-56.
PMID: 19864567 (This study is OPEN ACCESS if you would like to read it)
In this study, the researchers found that two statins (pravastatin and simvastatin – one hydrophilic and one lipophilic, respectively) both exhibited the ability to suppress the response of helper cells in the brain (called microglial) in a neurotoxin model of Parkinson’s disease. This microglial suppression resulted in a significant neuroprotective effect on the dopamine neurons in these animals.
Another study found more Parkinson’s disease relevant effects from statin treatment:
TItle: Lovastatin ameliorates alpha-synuclein accumulation and oxidation in transgenic mouse models of alpha-synucleinopathies.
Authors: Koob AO, Ubhi K, Paulsson JF, Kelly J, Rockenstein E, Mante M, Adame A, Masliah E.
Journal: Exp Neurol. 2010 Feb;221(2):267-74.
PMID: 19944097 (This study is OPEN ACCESS if you would like to read it)
In this study, the researchers treated two different types of genetically engineered mice (both sets of mice produce very high levels of alpha synuclein – the protein closely associated with Parkinson’s disease) with a statin called lovastatin. In both groups of alpha synuclein producing mice, lovastatin treatment resulted in significant reductions in the levels of cholesterol in their blood when compared to the saline-treated control mice. The treated mice also demonstrated a significant reduction in levels of alpha synuclein clustering (or aggregation) in the brain than untreated mice, and this reduction in alpha synuclein accumulation was associated with a lessening of pathological damage in the brain.
So statins may not be all bad?
One thing many of these studies fail to do is differentiate between whether statins are causing the trouble (or benefit) directly or whether simply lowering cholesterol levels is having a negative impact. That is to say, do statins actually do something else? Other than lowering cholesterol levels, are statins having additional activities that could cause good or bad things to happen?
The recently published study we are reviewing in this post suggested that non-statin cholesterol medication is also positively associated with developing Parkinson’s disease. Thus it may be that statins are not bad, but rather the lowering of cholesterol levels that is. This raises the question of whether high levels of cholesterol are delaying the onset of Parkinson’s disease, and one can only wonder what a cholesterol-based process might be able to tell us about the development of Parkinson’s disease.
If the findings of this latest study are convincingly replicated by other groups, however, we may need to reconsider the use of statins not in our day-to-day clinical practice. At the very least, we will need to predetermine which individuals may be more susceptible to developing Parkinson’s disease following the initiation of statin treatment. It would actually be very interesting to go back to the original data set of this new study and investigate what addition medical features were shared between the people that developed Parkinson’s disease after starting statin treatment. For example, were they all glucose intolerant? One would hope that the investigators are currently doing this.
Are Statins currently being tested in the clinic for Parkinson’s disease?
(Oh boy! Tough question) Yes, they are.
There is currently a nation wide study being conducted in the UK called PD STAT.
Is this dangerous given the results of the new research study?
(Oh boy! Even tougher question!)
Again, we are asking this question based on the results of one recent study. Replication with independent databases is required before definitive conclusions can be made.
There have, however, been previous clinical studies of statins in neurodegenerative conditions and these drugs have not exhibited any negative effects (that I am aware of). In fact, a clinical trial for multiple sclerosis published in 2014 indicated some positive results for sufferers taking simvastatin:
Title: Effect of high-dose simvastatin on brain atrophy and disability in secondary progressive multiple sclerosis (MS-STAT): a randomised, placebo-controlled, phase 2 trial.
Authors: Chataway J, Schuerer N, Alsanousi A, Chan D, MacManus D, Hunter K, Anderson V, Bangham CR, Clegg S, Nielsen C, Fox NC, Wilkie D, Nicholas JM, Calder VL, Greenwood J, Frost C, Nicholas R.
Journal: Lancet. 2014 Jun 28;383(9936):2213-21.
PMID: 24655729 (This article is OPEN ACCESS if you would like to read it)
In this double-blind clinical study (meaning that both the investigators and the subjects in the study were unaware of which treatment was being administered), 140 people with multiple sclerosis were randomly assigned to receive either the statin drug simvastatin (70 people; 40 mg per day for the first month and then 80 mg per day for the remainder of 18 months) or a placebo treatment (70 people).
Patients were seen at 1, 6, 12, and 24 months into the study, with telephone follow-up at months 3 and 18. MRI brain scans were also made at the start of the trial, and then again at 12 months and 25 months for comparative sake.
The results of the study indicate that high-dose simvastatin was well tolerated and reduced the rate of whole-brain shrinkage compared with the placebo treatment. The mean annualised shrinkage rate was significantly lower in patients in the simvastatin group. The researchers were very pleased with this result and are looking to conduct a larger phase III clinical trial.
Other studies have not demonstrated beneficial results from statin treatment, but they have also not observed a worsening of the disease conditions:
Title: A randomized, double-blind, placebo-controlled trial of simvastatin to treat Alzheimer disease.
Authors:Sano M, Bell KL, Galasko D, Galvin JE, Thomas RG, van Dyck CH, Aisen PS.
Journal: Neurology. 2011 Aug 9;77(6):556-63.
PMID: 21795660 (This article is OPEN ACCESS if you would like to read it)
In this study, the investigators recruited a total of 406 individuals were mild to moderate Alzheimer’s disease, and they were randomly assigned to two groups: 204 to simvastatin (20 mg/day, for 6 weeks then 40 mg per day for the remainder of 18 months) and 202 to placebo control treatment. While Simvastatin displayed no beneficial effects on the progression of symptoms in treated individuals with mild to moderate Alzheimer’s disease (other than significantly lowering of cholesterol levels), the treatment also exhibited no effect on worsening the disease.
So what does it all mean?
Research investigating cholesterol and its association with Parkinson’s disease has been going on for a long time. This week a research report involving a huge database was published which indicated that using cholesterol reducing medication could significantly increase one’s risk of developing Parkinson’s disease.
These results do not mean that someone being administered statins is automatically going to develop Parkinson’s disease, but – if the results are replicated – it may need to be something that physicians should consider before prescribing this class of drug.
Whether ongoing clinical trials of statins and Parkinson’s disease should be reconsidered is a subject for debate well above my pay grade (and only if the current results are replicated independently). It could be that statin treatment (or lowering of cholesterol) may have an ‘unmasking’ effect in some individuals, but does this mean that any beneficial effects in other individuals should be discounted? If preclinical data is correct, for example, statins may reduce alpha synuclein clustering in some people which could be beneficial in Parkinson’s.
As we have said above, further research is required in this area before definitive conclusions can be made. This is particularly important given the inconsistencies of the previous research results in the statin and Parkinson’s disease field of investigation.
EDITORIAL NOTE: The information provided by the SoPD website is for information and educational purposes only. Under no circumstances should it ever be considered medical or actionable advice. It is provided by research scientists, not medical practitioners. Any actions taken – based on what has been read on the website – are the sole responsibility of the reader. Any actions being contemplated by readers should firstly be discussed with a qualified healthcare professional who is aware of your medical history. While some of the information discussed in this post may cause concern, please speak with your medical physician before attempting any change in an existing treatment regime.
The banner for today’s post was sourced from HarvardHealth
Please excuse our use of UK slang in the title of this post, but a group of Australian researchers have recently discovered something really interesting about Parkinson’s disease.
And being a patriotic kiwi, it takes something REALLY interesting for me to even acknowledge that other South Pacific nation. This new finding, however, could be big.
In today’s post, we will review new research dealing with a protein called SOD1, and discuss what it could mean for the Parkinson’s community.
The number of dark pigmented dopamine cells in the substantia nigra are reduced in the Parkinson’s disease brain (right). Source: Adaptd from Memorangapp
Every Parkinson’s-associated website and every Parkinson’s disease researchers will tell you exactly the same thing when describing the two cardinal features in the brain of a person who died with Parkinson’s disease:
- The loss of certain types of cells (such as the dopamine producing cells of the substantia nigra region of the brain – see the image above)
- The clustering (or aggregation) of a protein called Alpha synuclein in tightly packed, circular deposits, called Lewy bodies (see image below).
A Lewy body inside a cell. Source: Adapted from Neuropathology-web
The clustered alpha synuclein protein, however, is not limited to just the Lewy bodies. In the affected areas of the brain, aggregated alpha synuclein can be seen in the branches of cells – see the image below where alpha synuclein has been stained brown on a section of brain from a person with Parkinson’s disease.
Examples of Lewy neurites (indicated by arrows). Source: Wikimedia
Now, one of the problems with our understanding of Parkinson’s disease is disparity between the widespread presence of clustered alpha synuclein and very selective pattern of cell loss. Alpha synuclein aggregation can be seen distributed widely around the affected areas of the brain, but the cell loss will be limited to specific populations of cells.
If the disease is killing a particular population of cells, why is alpha synuclein clustering so wide spread?
So why is there a difference?
We don’t know.
It could be that the cells that die have a lower threshold for alpha synuclein toxicity (we discussed this is a previous post – click here?).
But this question regarding the difference between these two features has left many researchers wondering if there may be some other protein or agent that is actually killing off the cells and then disappearing quickly, leaving poor old alpha synuclein looking rather guilty.
Poor little Mr “A Synuclein” got the blame, but his older brother actually did it! Source: Youtube
And this is a very serious discussion point.
This year of 2017 represents the 200th anniversary of James Parkinson’s first description of Parkinson’s disease, but it also represents the 20th anniversary since the association between alpha synuclein and PD was first established. We have produced almost 7,000 research reports on the topic of alpha synuclein and PD during that time, and we currently have ongoing clinical trials targetting alpha synuclein.
But what if our basic premise – that alpha synuclein is the bad guy – is actually wrong?
Is there any evidence to suggest this?
We are just speculating here, but yes there is.
For example, in a study of 904 brains, alpha synuclein deposits were observed in 11.3% of the brains (or 106 cases), but of those cases only 32 had been diagnosed with a neurodegenerative disorder (Click here to read more on this). The remaining 74 cases had demonstrated none of the clinical features of Parkinson’s disease.
So what else could be causing the cell death?
Well, this week some scientists from sunny Sydney (Australia) reported a protein that could fit the bill.
Sydney. Source: Vagabond
The interesting part of their finding is that the protein is also associated with another neurodegenerative condition: Amyotrophic lateral sclerosis.
Remind me again, what is Amyotrophic lateral sclerosis?
Parkinson’s disease and Amyotrophic lateral sclerosis (ALS) are the second and third most common adult-onset neurodegenerative conditions (respectively) after Alzheimer’s disease. We recently discussed ALS in a previous post (Click here to read that post).
ALS, also known as Lou Gehrig’s disease and motor neuron disease, is a neurodegenerative condition in which the neurons that control voluntary muscle movement die. The condition affects 2 people in every 100,000 each year, and those individuals have an average survival time of two to four years.
You may have heard of ALS due to it’s association with the internet ‘Ice bucket challenge‘ craze that went viral in 2014-15.
The Ice bucket challenge. Source: Forbes
What is the protein associated with ALS?
In 1993, scientists discovered that mutations in the gene called SOD1 were associated with familial forms of ALS (Click here to read more about this). We now know that mutations in the SOD1 gene are associated with around 20% of familial cases of ALS and 5% of sporadic ALS.
The SOD1 gene produces an enzyme called Cu-Zn superoxide dismutase.
This enzyme is a very powerful antioxidant that protects the body from damage caused by toxic free radical generated in the mitochondria.
SOD1 protein structure. Source: Wikipedia
One important note here regarding ALS: the genetic mutations in the SOD1 gene do not cause ALS by affecting SOD1’s antioxidant properties (Click here to read more about this). Rather, researchers believe that the cell death seen in SOD1-associated forms of ALS is the consequences of some kind of toxic effect caused by the mutant protein.
So what did the Aussie researchers find about SOD1 in Parkinson’s disease?
This week, the Aussie researchers published this research report:
Title: Amyotrophic lateral sclerosis-like superoxide dismutase 1 proteinopathy is associated withneuronal loss in Parkinson’s disease brain.
Authors: Trist BG, Davies KM, Cottam V, Genoud S, Ortega R, Roudeau S, Carmona A, De Silva K, Wasinger V, Lewis SJG, Sachdev P, Smith B, Troakes C, Vance C, Shaw C, Al-Sarraj S, Ball HJ, Halliday GM, Hare DJ, Double KL.
Journal: Acta Neuropathol. 2017 May 19. doi: 10.1007/s00401-017-1726-6.
Given that oxidative stress is a major feature of Parkinson’s disease, the Aussie researchers wanted to investigate the role of the anti-oxidant enzyme, SOD1 in this condition. And what they found surprised them.
Heck, it surprised us!
Two areas affected by Parkinson’s disease – the substantia nigra (where the dopamine neurons reside; SNc in the image below) and the locus coeruleus (an area in the brain stem that is involved with physiological responses to stress; LC in the image below) – exhibited little or no SOD1 protein in the control brains.
But in the Parkinsonian brains, there was a great deal of SOD1 protein (see image below).
SO1 staining in PD brain and Control brains. Source: Springer
In the image above, you can see yellowish-brown stained patches in both the PD and control images. This a chemical called neuromelanin and it can be used to identify the dopamine-producing cells in the SNc and LC. The grey staining in the PD images (top) are cells that contain SOD1. Note the lack of SOD1 (grey staining) in the control images (bottom).
Approximately 90% of Lewy bodies in the Parkinson’s affected brains contained SOD1 protein. The investigators did report that the levels of SOD1 protein varied between Lewy bodies. But the clustered (or ‘aggregated’) SOD1 protein was not just present with alpha synuclein, often it was found by itself in the degenerating regions.
The researchers occasional saw SOD1 aggregation in regions of age-matched control brains, and they concluded that a very low level of SOD1 must be inherent to the normal ageing process.
But the density of SOD1 clustering was (on average) 8x higher in the SNc and 4x higher in the LC in the Parkinsonian brain compared to age-matched controls. In addition, the SOD1 clustering was significantly greater in these regions than all of the non-degenerating regions of the same Parkinson’s disease brains.
The investigators concluded that these data suggest an association between SOD1 aggregation and neuronal loss in Parkinson’s disease. Importantly, the presence of SOD1 aggregations “closely reflected the regional pattern of neuronal loss”.
They also demonstrated that the SOD1 protein in the Parkinsonian brain was not folded correctly, a similar characteristic to alpha synuclein. A protein must fold properly to be able to do it’s assigned jobs. By not folding into the correct configuration, the SOD1 protein could not do it’s various functions – and the investigators observed a 66% reduction in SOD1 specific activity in the SNc of the Parkinson’s disease brains.
Interestingly, when the researchers looked at the SNc and LC of brains from people with ALS, they identified SOD1 aggregates matching the SOD1 clusters they had seen in these regions of the Parkinson’s disease brain.
Is this the first time SOD1 has been associated with Parkinson’s disease?
No, but it is the first major analysis of postmortem Parkinsonian brains. SOD1 protein in Lewy bodies has been reported before:
Title: Cu/Zn superoxide dismutase-like immunoreactivity is present in Lewy bodies from Parkinson disease: a light and electron microscopic immunocytochemical study
Authors: Nishiyama K, Murayama S, Shimizu J, Ohya Y, Kwak S, Asayama K, Kanazawa I.
Journal: Acta Neuropathol. 1995;89(6):471-4.
The investigators behind this study reported SOD1 protein was present in Lewy bodies, in the substantia nigra and locus coeruleus of brains from five people with Parkinson’s disease. Interestingly, they showed that SOD1 is present in the periphery of the Lewy body, similar to alpha synuclein. Both of these protein are present on the outside of the Lewy body, as opposed to another Parkinson’s associated protein, Ubiquitin, which is mainly present in the centre (or the core) of Lewy bodies (see image below).
A more recent study also demonstrated SOD1 protein in the Parkinsonian brain, including direct interaction between SOD1 and alpha synuclein:
Title: α-synuclein interacts with SOD1 and promotes its oligomerization
Authors: Helferich AM, Ruf WP, Grozdanov V, Freischmidt A, Feiler MS, Zondler L, Ludolph AC, McLean PJ, Weishaupt JH, Danzer KM.
Journal: Mol Neurodegener. 2015 Dec 8;10:66.
PMID: 26643113 (This article is OPEN ACCESS if you would like to read it)
These researchers found that alpha synuclein and SOD1 interact directly, and they noted that Parkinson’s disease related mutations in alpha synuclein (A30P, A53T) and ALS associated mutation in SOD1 (G85R, G93A) modify the binding of the two proteins to each other. They also reported that alpha synuclein accelerates SOD1 aggregation in cell culture. This same group of researchers published another research report last year in which they noted that aggregated alpha synuclein increases SOD1 clustering in a mouse model of ALS (Click here for more on this).
Are there any genetic mutations in the SOD1 gene that are associated with Parkinson’s disease?
Two studies have addressed this question:
Title: Sequence of the superoxide dismutase 1 (SOD 1) gene in familial Parkinson’s disease.
Authors: Bandmann O, Davis MB, Marsden CD, Harding AE.
Journal: J Neurol Neurosurg Psychiatry. 1995 Jul;59(1):90-1.
PMID: 7608718 (This article is OPEN ACCESS if you would like to read it)
And then in 2001, a second analysis:
Title: Genetic polymorphisms of superoxide dismutase in Parkinson’s disease.
Authors: Farin FM, Hitosis Y, Hallagan SE, Kushleika J, Woods JS, Janssen PS, Smith-Weller T, Franklin GM, Swanson PD, Checkoway H.
Journal: Mov Disord. 2001 Jul;16(4):705-7.
Both studies found no genetic variations in the SOD1 gene that were more frequent in the Parkinson’s affected community than the general population. So, no, there are no SOD1 genetic mutations that are associated with Parkinson’s disease.
Are there any treatments targeting SOD1 that could be tested in Parkinson’s disease?
Great question. Yes there are. And they have already been tested in models of PD:
Title: The hypoxia imaging agent CuII(atsm) is neuroprotective and improves motor and cognitive functions in multiple animal models of Parkinson’s disease.
Authors: Hung LW, Villemagne VL, Cheng L, Sherratt NA, Ayton S, White AR, Crouch PJ, Lim S, Leong SL, Wilkins S, George J, Roberts BR, Pham CL, Liu X, Chiu FC, Shackleford DM, Powell AK, Masters CL, Bush AI, O’Keefe G, Culvenor JG, Cappai R, Cherny RA, Donnelly PS, Hill AF, Finkelstein DI, Barnham KJ.
Title: J Exp Med. 2012 Apr 9;209(4):837-54.
PMID: 22473957 (This article is OPEN ACCESS if you would like to read it)
CuII(atsm) is a drug that is currently under clinical investigation as a brain imaging agent for detecting hypoxia (damage caused by lack of oxygen – Click here to read more about this).
The researchers conducting this study, however, were interested in this compound for other reasons: CuII(atsm) is also a highly effective scavenger of a chemical called ONOO, which can be very toxic. CuII(atsm) not only inhibits this toxicity, but it also blocks the clustering of alpha synuclein. And given that CuII(atsm) is capable of crossing the blood–brain barrier, these investigators wanted to assess the drug for its ability to rescue model of Parkinson’s disease.
And guess what? It did!
And not just in one model of Parkinson’s disease, but FOUR!
The investigators even waited three days after giving the neurotoxins to the mice before giving the CuII(atsm) drug, and it still demonstrated neuroprotection. It also improved the behavioural features of these models of Parkinson’s disease.
Is CuII(atsm) being tested for anything else in Clinical trials?
Yes, there is a clinical trial ongoing for ALS in Australia.
The Phase I study, being run by Collaborative Medicinal Development Pty Limited, is a dose escalating study of Cu(II)ATSM to determine if this drug is safe for use in ALS (Click here for more on this study).
Cu(II)ATSM is an orally administered drug that inhibits the activity of misfolded SOD1 protein. It has been shown to paradoxically increase mutant SOD1 protein in a mouse model of ALS, but it also provides neuroprotection and improves the outcome for these mice (Click here to read more on this).
If this trial is successful, it would be interesting to test this drug on a cohort of people with Parkinson’s disease. Determining which subgroup of the Parkinson’s affected community would most benefit from this treatment is still to be determined. There is some evidence published last year that suggests people with genetic mutations in the Parkinson’s associated gene PARK2 could benefit from the approach (Click here to read more on this). More research, however, is needed in this area.
So what does it all mean?
Right, so summing up, a group of Australian researchers have reported that the ALS associated protein SOD1 is closely associated with the cell death that we observe in the brains of people with Parkinson’s disease.
They suggest that this could highlight a common mechanisms of toxic SOD1 aggregation in both Parkinson’s disease and ALS. Individuals within the Parkinson’s affected community do not appear to have any genetic mutations in the SOD1 gene, which makes this finding is very interesting.
What remains to be determined is whether SOD1 aggregation is a “primary pathological event”, or if it is secondary to some other disease causing agent. We are also waiting to see if a clinical trial targeting SOD1 in ALS is successful. If it is, there may be good reasons for targeting SOD1 as a novel treatment for Parkinson’s disease.
The banner for today’s post was sourced from Pinterest
Being a proud kiwi, I am happy to highlight and support any research coming out of New Zealand.
Recently a new commentary has been published suggesting that living in the NZ city of Rotorua (‘Roto-Vegas‘ to the locals) may decrease the risk of developing Parkinson’s disease.
In today’s post, we will review the research behind the idea and discuss what it could mean for people with neurodegenerative conditions, like Parkinson’s disease.
The geothermal wonderlands of Rotorua. Source: Audleytravel
Rotorua is a small city in the central eastern area of the North Island of New Zealand (Aotearoa in the indigenous Māori language).
The name Rotorua comes from the Māori language (‘roto’ meaning lake and rua meaning ‘two’). The full Māori name for the spot is actually Te Rotorua-nui-a-Kahumatamomoe. The early Māori chief and explorer Ihenga named it after his uncle Kahumatamomoe. But given that it was the second major lake found in Aotearoa (after lake Taupo in the centre of the North Island), the name that stuck was Rotorua or ‘Second lake’.
Maori culture. Source: TamakiMaoriVillage
Similar to lake Taupo, Rotorua is a caldera resulting from an ancient volcanic eruption (approximately 240,000 years ago). The lake that now fills it is about 22 km (14 mi) in diameter.
Lake Rotorua. Source: Teara
The volcano may have disappeared, but the surrounding region is still full of geothermal activity (bubbling mud pools and geysers), providing the region with abundant renewable power and making the city a very popular tourist destination.
Tourist playing with mud. Source: Rotoruanz
Before visiting the city, however, travellers should be warned that Rotorua’s other nicknames include “Sulphur City” and “Rotten-rua”, because of the smell that results from the geothermal activity.
And speaking from personal experience, the “rotten eggs” smell is prevalent.
Interesting, but what has this got to do with the science of Parkinson’s disease?
Well, the rotten egg smell is the result of hydrogen sulfide emissions, and recently it has been suggested that this pungent gas may be having positive benefits on people, particularly with regards to Parkinson’s disease.
This idea has been proposed by Dr Yusuf Cakmak at the University of Otago in a recent commentary:
Title: Rotorua, hydrogen sulphide and Parkinson’s disease-A possible beneficial link?
Author: Cakmak Y.
Journal: N Z Med J. 2017 May 12;130(1455):123-125.
In his write up, Dr Cakmak points towards two studies that have been conducted on people from Rotorua. The first focused on examining whether there was any association between asthma and chronic obstructive pulmonary disease and exposure to hydrogen sulfide in Rotorua. By examining air samples and 1,204 participants, the investigators of that study no association (the report of that study is OPEN ACCESS and can be found by clicking here).
The second study is the more interesting of the pair:
Title: Chronic ambient hydrogen sulfide exposure and cognitive function.
Authors: Reed BR, Crane J, Garrett N, Woods DL, Bates MN.
Journal: Neurotoxicol Teratol. 2014 Mar-Apr;42:68-76.
PMID: 24548790 (This article is OPEN ACCESS if you would like to read it)
In this study, the investigators recruited 1,637 adults (aged 18-65 years) from Rotorua. They conducted neuropsychological tests on the subjects, measuring visual and verbal episodic memory, attention, fine motor skills, psychomotor speed and mood. The average amount of time the participants had lived in the Rotorua region was 18 years (ranging from 3-64 years). The researchers also made measurements of hydrogen sulfide levels at the participants homes and work sites.
While the researchers found no association between hydrogen sulfide exposure and cognitive ability, they did notice something interesting in the measures of fine motor skills: individuals exposed to higher levels of hydrogen sulfide displayed faster motor response times on tasks like finger tapping. Finger tapping speed is an important part of Parkinson’s Motor Rating Scale examination tests.
The investigators behind the study concluded that the levels of hydrogen sulfide in Rotorua do not have any detrimental effect on the individuals living in the area,
Dr Cakmak, however, wondered whether “relatively high, but safe, hydrogen sulfide levels in Rotorua could help protect the degradation of dopaminergic neurons associated with Parkinson’s Disease?” (based on the better performance on the motor response time).
Hang on a second, what exactly is hydrogen sulfide?
Hydrogen sulfide (chemical symbol: H2S) is a colourless gas. Its production often results from the the breaking down of organic material in the absence of oxygen, such as in sewers (this process is called anaerobic digestion. It also occurs in volcanic and geothermal conditions.
H2S. Source: Wikipedia
About 15 years ago, it was found in various organs in the body and termed a gasotransmitter. A gasotransmitter is a molecule that can be used to transmit chemical signals from one cell to another, which results in certain physiological reactions (oxygen, for example, is a gasotransmitter).
Hydrogen sulfide is now known to be cardioprotective (protection of the heart), and many years of research have demonstrated beneficial aspects of using it in therapy, such as vasodilation and lowering blood pressure, increasing levels of antioxidants, inhibiting inflammation, and activation of anti-apoptotic (anti-cell death) pathways. For a good review of hydrogen sulfide’s cardioprotective properties – click here.
The demonstration of the protective properties of hydrogen sulfide in other bodily organs have led neuroscientists to start investigating whether these same benefits could be utilised in treating disorders of the brain.
And the good news is: hydrogen sulfide can have positive benefits in the brain – Click here for a good review of the brain-related research.
Has other research been conducted on hydrogen sulfide regarding Parkinson’s disease?
Yes. And here is where the story starts to get really interesting.
Then hydrogen sulfide was tested in rodent models of Parkinson’s disease:
Title: Neuroprotective effects of hydrogen sulfide on Parkinson’s disease rat models.
Authors: Hu LF, Lu M, Tiong CX, Dawe GS, Hu G, Bian JS.
Journal: Aging Cell. 2010 Apr;9(2):135-46.
PMID: 20041858 (This article is OPEN ACCESS if you would like to read it)
In this study, the researchers firstly looked at what happens to hydrogen sulfide in the brains of rodent models of Parkinson’s disease. When rats were injected with a neurotoxin (6-OHDA) that kills dopamine neurons, the investigators found a significant drop in the level of hydrogen sulfide in the region where the dopamine cells reside (called the substantia nigra – an area of the brain severely affected in Parkinson’s disease).
Next the researchers gave some rodents the neurotoxin, waited three weeks and then began administering sodium hydrosulfide – which is a hydrogen sulfide donor – every day for a further 3 weeks. They found that this treatment significantly reduced the dopamine cell loss, motor problems and inflammation in the sodium hydrosulfide treated animals. Interestingly, they saw the same neuroprotective effect when they repeated the study with a different neurotoxin (Rotenone). The investigators concluded that hydrogen sulfide “has potential therapeutic value for treatment of Parkinson’s disease”.
And this first study was followed up one year later by a study investigating inhaled hydrogen sulfide:
Title: Inhaled hydrogen sulfide prevents neurodegeneration and movement disorder in a mouse model of Parkinson’s disease.
Authors: Kida K, Yamada M, Tokuda K, Marutani E, Kakinohana M, Kaneki M, Ichinose F.
Journal: Antioxid Redox Signal. 2011 Jul 15;15(2):343-52.
PMID: 21050138 (This article is OPEN ACCESS if you would like to read it)
In this study, the investigators gave mice a neurotoxin (MPTP) and then had them breathe air with or without hydrogen sulfide (40 ppm) for 8 hours per day for one week. The mice that inhaled hydrogen sulfide displayed near normal levels of motor behaviour performance and significantly reduced levels of neurodegeneration (dopamine cell loss).
Inhalation of hydrogen sulfide also prevented the MPTP-induced activation of the brain’s helper cells (microglia and astrocytes) and increased levels of detoxification enzymes and antioxidant proteins (including heme oxygenase-1 and glutamate-cysteine ligase). Curiously, hydrogen sulfide inhalation did not significantly affect levels of reduced glutathione (we will come back to this in an upcoming post).
These first two preclinical results have been replicated many times now confirming the initial findings (Click here, here, here and here for examples). The researchers of the second ‘inhalation’ study concluded the study by suggesting that the potential therapeutic effects of hydrogen sulfide inhalation now needed to be examined in more disease relevant models of Parkinson’s disease.
And this is exactly what researchers did next:
Title: Sulfhydration mediates neuroprotective actions of parkin.
Authors: Vandiver MS, Paul BD, Xu R, Karuppagounder S, Rao F, Snowman AM, Ko HS, Lee YI, Dawson VL, Dawson TM, Sen N, Snyder SH.
Journal: Nat Commun. 2013;4:1626. doi: 10.1038/ncomms2623.
PMID: 23535647 (This article is OPEN ACCESS if you would like to read it)
The researchers conducting this study were interested in the interaction of hydrogen sulfide with the Parkinson’s disease-associated protein Parkin (also known as PARK2). They found that hydrogen sulfide actively modified parkin protein – a process called sulfhydration – and that this enhances the protein’s level of activity.
They also noted that the level of Parkin sulfhydration in the brains of patients with Parkinson’s disease is markedly reduced (a 60% reduction). These finding imply that drugs that increase levels of hydrogen sulfide in the brain may be therapeutic.
Interestingly, cells with genetic mutations in another Parkinson’s disease related gene, DJ-1, also produce less hydrogen sulfide (click here to read more about this).
Has anyone ever looked at hydrogen sulfide and alpha synuclein?
Not that we are aware of.
Alpha synuclein is the Parkinson’s disease associated protein that clusters in the Parkinsonian brain and forms Lewy bodies.
But researchers have looked at hydrogen sulfide and amyloid formation:
Title: Hydrogen sulfide inhibits amyloid formation
Authors: Rosario-Alomar MF, Quiñones-Ruiz T, Kurouski D, Sereda V, Ferreira EB, Jesús-Kim LD, Hernández-Rivera S, Zagorevski DV, López-Garriga J, Lednev IK.
Journal: J Phys Chem B. 2015 Jan 29;119(4):1265-74.
PMID: 25545790 (This article is OPEN ACCESS if you would like to read it)
Amyloid formations are large clusters of misfolded proteins that are associated with neurodegenerative conditions, like Alzheimer’s disease and Parkinson’s disease. The researchers who conducted this study were interested in the behaviour of these misfolded protein in the presence of hydrogen sulfide. What they found was rather remarkable: the addition of hydrogen sulfide completely inhibited the formation amyloid fibrils (amyloid fibril plaques are found in brains of people with Alzheimer’s disease).
If the addition of hydrogen sulfide can reduce the level of clustered proteins in a model of Alzheimer’s disease, it would be interesting to see what it would do to alpha synuclein.
NOTE: Hydrogen sulfide levels are also reduced in the brains of people with Alzheimer’s disease (click here to read more on this topic)
Has hydrogen sulfide ever been tested in the clinic?
There are currently 17 clinical trials investigating hydrogen sulfide in various conditions (not Parkinson’s disease though).
So where can I get me some of that hydrogen sulfide?
Ok, so here is where we come in with the health warning section.
You see, hydrogen sulfide is a very dangerous gas. It is really not to be played with.
The gas is both corrosive and flammable. More importantly, at high concentrations, hydrogen sulfide gas can be fatal almost immediately (>1000 parts per milllion – source: OSHA). And the gas only exhibits the “rotten eggs” smell at low concentrations. At higher concentrations it becomes undetectable due to olfactory paralysis (luckily for the folks in Rotorua, the levels of hydrogen sulfide gas there are between 20-25 parts per billion).
Thus, we do not recommend readers to rush out and load up on hydrogen sulfide gas.
There are many foods that contain hydrogen sulfide.
For example, garlic is very rich in hydrogen sulfide. Another rich source is cooked beef, which has about 0.6mg of hydrogen sulfide per pound – cooked lamb has closer to 0.9 milligrams per pound. Heated dairy products, such as skim milk, can have approximately 3 milligrams of hydrogen sulfide per gallon, and cream has slightly more than double that amount.
Any significant change in diet by a person with Parkinson’s disease should firstly be discussed with a trained medical physician as we can not be sure what impact such a change would have on individualised treatment regimes.
What does it all mean?
Summing up: It would be interesting to look at the frequency of Parkinson’s disease in geothermal region of the world (the population of Rotorua is too small for such an analysis – 80,000 people).
Researchers believe that components of the gas emissions from these geothermal areas may be neuroprotective. Of particular interest is the gas hydrogen sulfide. At high levels, it is a very dangerous gas. At lower levels, however, researchers have shown that hydrogen sulfide has many beneficial properties, including in models of neurodegenerative conditions. These findings have led many to propose testing hydrogen sulfide in clinical trials for conditions like Parkinson’s disease.
Dr Cakmak, who we mentioned near the top of this post, goes one step further. He hypothesises that hydrogen sulfide may actually be one of the active components in the neuroprotective affect of both coffee and smoking – and with good reason. It was recently demonstrated that the certain gut bacteria, such as Prevotella, are decreased in people with Parkinson’s disease (see our post on this topic by clicking here). The consumption of coffee has been shown to help improve the Prevotella population in the gut, which may in term increase the levels of Prevotella-derived hydrogen sulfide. Similarly smokers have a decreased risk of developing Parkinson’s disease and hydrogen sulfide is a component of cigarette smoke.
All of these ideas still needs to be further tested, but we are curious to see where this research could lead. An inhaled neuroprotective treatment for Parkinson’s disease may have benefits for other neurodegenerative conditions.
Oh, and if anyone is interested, we are happy to put readers in contact with real estate agents in sunny ‘Rotten-rua’, New Zealand. The locals say that you gradually get used to the smell.
EDITOR’S NOTE: Under absolutely no circumstances should anyone reading this material consider it medical advice. The material provided here is for educational purposes only. Before considering or attempting any change in your treatment regime, PLEASE consult with your doctor or neurologist. While some of the drugs/molecules discussed on this website are clinically available, they may have serious side effects. We therefore urge caution and professional consultation before any attempt to alter a treatment regime. SoPD can not be held responsible for any actions taken based on the information provided here.
The banner for today’s post was sourced from Trover
The Federal Drug Administration (FDA) in the USA has approved the first drug in 22 years for treating the neurodegenerative condition of Amyotrophic lateral sclerosis (ALS).
The drug is called Edaravone, and it is only the second drug approved for ALS.
In today’s post we’ll discuss what this announcement could mean for Parkinson’s disease.
Lou Gehrig. Source: NBC
In 1969, Henry Louis “Lou” Gehrig was voted the greatest first baseman of all time by the Baseball Writers’ Association. He played 17 seasons with the New York Yankees, having signed with his hometown team in 1923.
For 56 years, he held the record for the most consecutive games played (2,130), and he was only prevented from continuing that streak when he voluntarily took himself out of the team lineup on the 2nd May, 1939, after his ability to play became hampered by the disease that now often bears his name. A little more than a month later he retired, and a little less than two years later he passed away.
Amyotrophic lateral sclerosis (or ALS), also known as Lou Gehrig’s disease and motor neuron disease, is a neurodegenerative condition in which the neurons that control voluntary muscle movement die. The condition affects 2 people in every 100,000 each year, and those individuals have an average survival time of two to four years.
ALS in a nutshell. Source: Walkforals
In addition to Lou Gehrig, you may have heard of ALS via the ‘Ice bucket challenge‘ (see image in the banner of this post). In August 2014, an online video challenge went viral.
By July 2015, the ice bucket campaign had raised an amazing $115 million for the ALS Association.
Another reason you may have heard of ALS is that theoretical physicist, Prof Stephen Hawking also has the condition:
He was diagnosed with in a very rare early-onset, slow-progressing form of ALS in 1963 (at age 21) that has gradually left him wheel chair bound.
This is very interesting, but what does it have to do with Parkinson’s disease?
Individuals affected by ALS are generally treated with a drug called Riluzole (brand names Rilutek or Teglutik). Approved in December of 1995 by the FDA, this drug increases survival by approximately two to three months.
Until this last week, Riluzole was the only drug approved for the treatment of ALS.
So what happened this week?
On the 5th May, the FDA announced that they had approved a second drug for the treatment of ALS (Click here for the press release).
It is called Edaravone.
What is Edaravone?
Edaravone is a free radical scavenger – a potent antioxidant – that is marketed as a neurovascular protective agent in Japan by Mitsubishi Tanabe Pharma Corporation.
An antioxidant is simply a molecule that prevents the oxidation of other molecules.
Molecules in your body often go through a process called oxidation – losing an electron and becoming unstable. This chemical reaction leads to the production of what we call free radicals, which can then go on to damage cells.
What is a free radical?
A free radical is simply an unstable molecule – unstable because they are missing electrons. They react quickly with other molecules, trying to capture the needed electron to re-gain stability. Free radicals will literally attack the nearest stable molecule, stealing an electron. This leads to the “attacked” molecule becoming a free radical itself, and thus a chain reaction is started. Inside a living cell this can cause terrible damage, ultimately killing the cell.
Antioxidants are thus the good guys in this situation. They are molecules that neutralize free radicals by donating one of their own electrons. The antioxidant don’t become free radicals by donating an electron because by their very nature they are stable with or without that extra electron.
Thus when we say ‘Edaravone is a free radical scavenger’, we mean it’s really good at scavenging all those unstable molecules and stabilising them.
It is an intravenous drug (injected into the body via a vein) and administrated for 14 days followed by 14 days drug holiday.
So, again what has this got to do with Parkinson’s disease?
Well, it is easier to start a clinical trial of a drug if it is already approved for another disease.
And the good news is: Edaravone has been shown to be neuroprotective in several models of Parkinson’s disease.
In this post, we’ll lay out some of the previous research and try to make an argument justifying the clinical testing of Edaravone in Parkinson’s disease
Ok, so what research has been done so far in models of Parkinson’s disease?
The first study to show neuroprotection in a model of Parkinson’s disease was published in 2008:
Title: Role of reactive nitrogen and reactive oxygen species against MPTP neurotoxicity in mice.
Authors: Yokoyama H, Takagi S, Watanabe Y, Kato H, Araki T.
Journal: J Neural Transm (Vienna). 2008 Jun;115(6):831-42.
In this first study, the investigators assessed the neuroprotective properties of several drugs in a mouse model of Parkinson’s disease. The drugs included Edaravone (described above), minocycline (antibiotic discussed in a previous post), 7-nitroindazole (neuronal nitric oxide synthase inhibitor), fluvastatin and pitavastatin (both members of the statin drug class).
With regards to Edaravone, the news was not great: the investigators found that Edaravone (up to 30mg/kg) treatment 30 minutes before administering a neurotoxin (MPTP) and then again 90 minutes afterwards had no effect on the survival of the dopamine neurons (compared to a control treatment).
Not a good start for making a case for clinical trials!
This research report, however, was quickly followed by another from an independent group in Japan:
Title: Neuroprotective effects of edaravone-administration on 6-OHDA-treated dopaminergic neurons.
Authors: Yuan WJ, Yasuhara T, Shingo T, Muraoka K, Agari T, Kameda M, Uozumi T, Tajiri N, Morimoto T, Jing M, Baba T, Wang F, Leung H, Matsui T, Miyoshi Y, Date I.
Journal: BMC Neurosci. 2008 Aug 1;9:75.
PMID: 18671880 (This article is OPEN ACCESS if you would like to read it)
These researchers did find a neuroprotective effect using Edaravone (both in cell culture and in a rodent model of Parkinson’s disease), but they used a much higher dose than the previous study (up to 250 mg/kg in this study). This increase in dose resulted in a graded increase in neuroprotection – interestingly, these researchers also found that 30mg/kg of Edaravone had limited neuroprotective effects, while 250mg/kg exhibited robust dopamine cell survival and rescued the behavioural/motor features of the model even when given 24 hours after the neurotoxin.
The investigators concluded that “Edaravone might be a hopeful therapeutic option for PD, although several critical issues remain to be solved, including high therapeutic dosage of Edaravone for the safe clinical application in the future”
This results was followed by several additional studies investigating edaravone in models of Parkinson’s disease (Click here, here and here to read more on this). Of particular interest in all of those follow up studies was a report in which Edaravone treatment resulted in neuroprotective in genetic model of Parkinson’s disease:
Title: Edaravone prevents neurotoxicity of mutant L166P DJ-1 in Parkinson’s disease.
Authors: Li B, Yu D, Xu Z.
Journal: J Mol Neurosci. 2013 Oct;51(2):539-49.
DJ-1 is a gene that has been associated Parkinson’s disease since 2003. The gene is sometimes referred to as PARK7 (there are now more than 20 Parkinson’s associated genomic regions, which each have a number and are referred to as the PARK genes). Genetic mutations in the DJ-1 gene can result in an autosomal recessive (meaning two copies of the mutated gene are required), early-onset form of Parkinson disease. For a very good review of DJ-1 in the context of Parkinson’s disease, please click here.
The exact function of DJ-1 is not well understood, though it does appear to play a role in helping cells deal with ‘oxidative stress’ – the over-production of those free radicals we were talking about above. Now given that edaravone is a potent antioxidant (reversing the effects of oxidative stress), the researchers conducting this study decided to test Edaravone in cells with genetic mutations in the DJ-1 gene.
Their results indicated that Edaravone was able to significantly reduce oxidative stress in the cells and improve the functioning of the mitochondria – the power stations in each cell, where cells derive their energy. Furthermore, Edaravone was found to reduce the amount of cell death in the DJ-1 mutant cells.
More recently, researchers have begun digging deeper into the mechanisms involved in the neuroprotective effects of Edaravone:
Title: Edaravone leads to proteome changes indicative of neuronal cell protection in response to oxidative stress.
Authors: Jami MS, Salehi-Najafabadi Z, Ahmadinejad F, Hoedt E, Chaleshtori MH, Ghatrehsamani M, Neubert TA, Larsen JP, Møller SG.
Journal: Neurochem Int. 2015 Nov;90:134-41.
PMID: 26232623 (This article is OPEN ACCESS if you would like to read it)
The investigators who conducted this report began by performing a comparative two-dimensional gel electrophoresis analyses of cells exposed to oxidative stress with and without treatment of Edaravone.
Um, what is “comparative two-dimensional gel electrophoresis analyses”?
Two-dimensional gel electrophoresis analyses allows researchers to determine particular proteins within a given solution. Mixtures of proteins are injected into a slab of gel and they are then separated according to two properties (mass and acidity) across two dimensions (left-right side of the gel and top-bottom of the gel).
A two-dimensional gel electrophoresis result may look something like this:
Two-dimensional gel electrophoresis. Source: Nature
As you can see, individual proteins have been pointed out on the image of this slab of gel.
In comparative two-dimensional gel electrophoresis, two samples of solution are analysed by comparing two slabs of gel that have been injected with protein mix solution from two groups of cells treated exactly the same except for one variable. Each solution gets its own slab of gel, and the differences between the gel product will highlight which proteins are present in one condition versus the other (based on the variable being tested).
In this experiment, the variable was Edaravone.
And when the researchers compared the proteins of Edaravone treated cells with those of cells not treated with Edaravone, they found that the neuroprotective effect of Edaravone was being caused by an increase in a protein called Peroxiredoxin-2.
Now this was a really interesting finding.
You see, Peroxiredoxin proteins are a family (there are 6 members) of antioxidant enzymes. And of particular interest with regards to Parkinson’s disease is the close relationship between DJ-1 (the Parkinson’s associated protein discussed above) and peroxiredoxin proteins (Click here, here, here and here to read more about this).
In addition, there are also 169 research reports dealing with the peroxiredoxin proteins and Parkinson’s disease (Click here to see a list of those reports).
So, what do you think about a clinical trial for Edaravone in Parkinson’s disease?
Are you convinced?
Regardless, it an interesting drug huh?
Are there any downsides to the drug?
One slight issue with the drug is that it is injected via a vein. Alternative systems of delivery, however, are being explored.A biotech company in the Netherlands, called Treeway is developing an oral formulation of edaravone (called TW001) and is currently in clinical development.
Edaravone was first approved for clinical use in Japan on May 23, 2001. With almost 17 years of Edaravone clinical use, a few adverse events including acute renal failure have been noted, thus precautions should be taken with individuals who have a history of renal problems. The most common side effects associated with the drug, however, are: fatigue, nausea, and some mild anxiety.
Click here for a good overview of the clinical history of Edaravone.
So what does it all mean?
The announcement from the FDA this week regarding the approval of Edaravone as a new treatment for ALS represents a small victory for the ALS community, but it may also have a significant impact on other neurodegenerative conditions, such as Parkinson’s disease.
Edaravone is a potent antioxidant agent, which has been shown to have neuroprotective effects in various models of Parkinson’s disease and other neurodegenerative conditions. It could be interesting to now test the drug clinically for Parkinson’s disease. Many of the preclinical research reports indicate that the earlier Edaravone treatment starts, the better the outcomes, so any initial clinical trials should focus on recently diagnosed subjects (perhaps even those with DJ-1 mutations).
The take home message of this post is: given that Edaravone has now been approved for clinical use by the FDA, it may be advantageous for the Parkinson’s community to have a good look at whether this drug could be repurposed for Parkinson’s disease.
It’s just a thought.
The banner for today’s post was sourced from Forbes
Exciting news this week from the world of neurodegenerative research. Researchers have identified two clinically available drugs that display neuroprotective properties.
The drugs – Dibenzoylmethane and Trazodone – are currently used to treat cancer and depression, respectively.
In this post, we will review the research and discuss what it could mean for folks with Parkinson’s disease.
Old drugs – new tricks? Source: Repurposingdrugs101
As you may have heard from media reports (for examples, click here, here and here), researchers have identified two clinically available drugs that may help in the fight against neurodegenerative conditions, like Parkinson’s disease.
The re-purposing of clinically available drugs is the focus of much attention within the Parkinson’s community as it represents a means of bringing treatments to the clinic faster. The traditional lengthy clinical trial process that is required in the development of new medications means getting a new drug to market for neurodegeneration can take up to 15 years, as the trials run over several years each (and there are three phases to pass through).
Shortening the wait. Source: Austinpublishing
In an age of smart phones and instant gratification, who has that kind of patience? ( #Wewontwait ).
Thus, re-purposing of available drugs represents a more rapid means of bringing new treatments/therapies to the Parkinson’s community.
So what is the new research all about?
This is Professor Giovanna Mallucci.
Prof Giovanna Mallucci. Source: MRC
Her area of research interest is understanding mechanisms of neurodegeneration, with a particular focus on prion and Alzheimer’s disease.
A few years ago, her group published this report:
Title: Sustained translational repression by eIF2α-P mediates prion neurodegeneration.
Authors: Moreno JA, Radford H, Peretti D, Steinert JR, Verity N, Martin MG, Halliday M, Morgan J, Dinsdale D, Ortori CA, Barrett DA, Tsaytler P, Bertolotti A, Willis AE, Bushell M, Mallucci GR.
Journal: Nature. 2012 May 6;485(7399):507-11.
PMID: 22622579 (This article is OPEN ACCESS if you would like to read it)
In this study, Prof Mallucci’s group were interested in the biological events that were occurring in the brain following infection of mice with prion disease – another neurodegenerative condition. They found that a sudden loss of protein associated with the connections between neurons (those connections being called synapses) occurred at 9 weeks post infection. This led them to investigate the production of protein and they found that an increase in the levels of phosphorylation of a protein called eIF2alpha was associated with the reduction in protein synthesis occurring at 9 weeks post infection.
What is Phosphorylation?
Phosphorylation of a protein is basically the process of turning it on or off – making it active or inactive – for a particular function.
Phosphorylation of a kinase protein. Source: Nature
And what is eIF2alpha?
Eukaryotic Translation Initiation Factor 2 Alpha is (as the label on the can suggests) a translation initiation factor. This means that this particular protein functions in the early steps of the production of protein. That is to say, eIF2alpha has important roles in the first steps – the initiation – of making other proteins.
eIF2alpha’s role in neurodegeneration. Source: Frontiers
The increased phosphorylation of eIF2alpha results in the inactivation of eIF2alpha and therefore the transient shutdown of protein production.
This shutdown in protein production can serve as an important ‘checkpoint’ when a cell is stressed. By blocking general protein production, a damaged or stressed cell can have the opportunity to either recuperate or be eliminated (if the damage is beyond repair).
The shutdown can also be caused by the unfolded protein response (or UPR). The unfolded protein response is a protective mechanism triggered by rising levels of misfolded proteins.
What are misfolded proteins?
When proteins are being produced, they need to be folded into the correct shape to do their job. Things can turn ugly very quickly for a cell if protein are being misfolded or only partially folded.
Two proteins. Guess which is the misfolded protein. Source: Biogeekery
In fact, misfolded proteins are suspected of being responsible for many of the neurodegenerative conditions we know of (including Parkinson’s, Alzheimer’s, etc). Thus the unfolded protein response gives a cell time to stop protein production, degrade & dispose of any misfolded proteins, and then re-activate proteins involved with increasing the production again.
And Prof Mallucci’s group found an increase in the phosphorylation of eIF2alpha?
Yes. At 9 weeks post infection with prions, there is a decrease in the proteins required for maintaining the connections between neurons and an increase in the phosphorylation of eIF2alpha.
The interesting thing is that the researchers found that levels of phosphorylated eIF2alpha increased throughout the course of study.
So, the researchers asked themselves if promoting a recovery in protein production in the cells in neuroprotective. To test this they used a protein called GADD34, which is a specific eIF2alpha phosphatase (a phosphatase is a protein that dephosphates a protein). By introducing a lot of GADD34 in the cells, the researchers were able to re-activate eIF2alpha, rescue the connectivity between neurons and protect the cells from dying.
A cool trick, huh?
This report established the importance of eIF2alpha in the early stages of neurodegeneration, and Prof Mallucci and her group next decided to conduct a massive screening study of currently available medications to see which could be used to target eIF2alpha levels.
And that research gave rise to the report that caused so much excitement this week. This report here:
Title: Repurposed drugs targeting eIF2α-P-mediated translational repression prevent neurodegeneration in mice
Authors: Halliday M, Radford H, Zents KAM, Molloy C, Moreno JA, Verity NC, Smith E, Ortori CA, Barrett DA, Bushell M, Mallucci GR.
Journal: Brain, 2017 Epub early online publication
PMID: N/A (This article is OPEN ACCESS if you would like to read it)
The investigators began by testing 1,040 compounds (that represent many of the clinically available drugs we have) on tiny microscopic worms (called C.elegans). These worms represent a useful experimental model for screening drugs as many aspects of biology can be examined. These worms were exposed to both a chemical (called tunicamycin, which induces the unfolded protein response we were talking about above) and one of the 1040 compounds.
Of the 1040 compounds tested, the investigators selected the 20 that provided the best protection to the worms. They next analysed those top 20 compounds for their ability to reduce levels of phosphorylated eIF2alpha in cells. Cells were engineered to produce a bioluminescent signal when eIF2alpha was phosphorylated. The researchers used a potent blocker of the unfolded protein response (called GSK2606414) and a drug called ISRIB (which is an experimental drug which reverses the effects of eIF2alpha phosphorylation) as controls for the experiment.
Their results were interesting:
The results of the top 20 drugs screened. Source: Brain
As you can see from the graph above, there were five compounds (highlighted with ***) that provided a similar level of reduction as the ISRIB (control) drug:
- Azadirachtin – which is the active ingredient in many pesticides.
- Dibenzoylmethane – a cancer treatment.
- Proguanil – a medication used to treat and prevent malaria.
- Trazodone – an antidepressant used to treat depression and anxiety disorders.
- Trifluoperazine – an antipsychotic of the phenothiazine chemical class.
The investigators decided not to further investigate Azadirachtin as it is a pesticide and displays a poor ability to penetrant the blood-brain-barrier – the protective layer surrounding the brain. They also rejected Proguanil because while it is safe to use in humans, it is toxic in mice. This detail limited the amount of preclinical testing for neurodegeneration that the researchers could do. And finally Trifluoperazine was eliminated as it should not be used in the elderly populations (apparently it ‘increases the risk of death’!), which obviously limited it’s further utility given that age is a major determinant of neurodegeneration.
This selection process left the researchers with Dibenzoylmethane and Trazodone.
The researchers found that both of these drugs can cross the blood-brain-barrier and were able to prevent neurodegeneration and rescue behavioural deficits in prion-infected mice. And they observed no toxic effects of these treatments in other organs (such as the pancreas). The drugs restore correct protein production and increased the survival of the prion-infected mice.
Taking the study one step further, Prof Mallucci and her group asked if the drugs could be effective in a model of another neurodegenerative condition, such as Alzheimer’s disease. To investigated this, they treated rTg4510 mice with both of the drugs. rTg4510 mice produce a lot of a human protein (called tau) that has a particular mutation (known as P301L), which results in the onset of Alzheimer’s like pathology at an early age. The rTg4510 mice received either trazodone or Dibenzoylmethane on a daily basis from 4 months of age and were examined at 8 months of age. The researchers found significantly less cell loss and shrinkage in the brains of the mice treated with one of the two drugs when compared to rTg4510 mice that received no treatment.
The researchers concluded that “these compounds therefore represent potential new disease-modifying treatments for dementia. Trazodone in particular, a licensed drug, should now be tested in clinical trials in patients”.
As Professor Mallucci suggested to the press: “We know that trazodone is safe to use in humans, so a clinical trial is now possible to test whether the protective effects of the drug we see on brain cells in mice with neurodegeneration also applies to people in the early stages of Alzheimer’s disease and other dementias. We could know in 2-3 years whether this approach can slow down disease progression, which would be a very exciting first step in treating these disorders. Interestingly, trazodone has been used to treat the symptoms of patients in later stages of dementia, so we know it is safe for this group. We now need to find out whether giving the drug to patients at an early stage could help arrest or slow down the disease through its effects on this pathway.”
This is great for Alzheimer’s disease, but what about Parkinson’s?
Well, the researchers did not test the drugs in models of Parkinson’s disease. But we can assume that several research groups are going to be testing this drug in the near future… if they aren’t already!
But have increased levels of eIF2alpha been seen in Parkinson’s disease?
Great question. And the answer is: Yes.
Title: Activation of the unfolded protein response in Parkinson’s disease.
Authors: Hoozemans JJ, van Haastert ES, Eikelenboom P, de Vos RA, Rozemuller JM, Scheper W.
Journal: Biochem Biophys Res Commun. 2007 Mar 16;354(3):707-11.
In this study the investigators analysed the levels of Unfolded Protein Response activation in the postmortem brains of people who passed away with or without Parkinson’s disease. Specifically, they focused their analysis on the substantia nigra (the region where the dopamine neurons reside and which is most severely affected in Parkinson’s).
The researchers found that both eIF2alpha and a protein called PERK (also known as protein kinase-like ER kinase – which phosphalates eIF2alpha) are present in the dopamine neurons in the substantia nigra of brains from people with Parkinson’s disease, but not in healthy control brains. And as the graph below shows, the investigators noted that there was a trend towards the levels of these proteins peaking within the first five years after diagnosis.
eIF2alpha & PERK levels in the brain. Source: ScienceDirect
Similar postmortem analysis studies have also highlighted the increased levels of Unfolded Protein Response activation in the Parkinsonian brain (Click here to read more on this).
The increase in Unfolded Protein Response activation could be a common feature across different neurodegenerative conditions, suggesting that trazodone and dibenzoylmethane could be used widely to slow the progress of various conditions.
Another connection to Parkinson’s disease is the finding that high levels of the Parkinson’s associated protein alpha synuclein can cause the Unfolded Protein Response:
Title: Induction of the unfolded protein response by α-synuclein in experimental models of Parkinson’s disease.
Authors: Bellucci A, Navarria L, Zaltieri M, Falarti E, Bodei S, Sigala S, Battistin L, Spillantini M, Missale C, Spano P.
Journal: J Neurochem. 2011 Feb;116(4):588-605.
PMID: 21166675 (This article is OPEN ACCESS if you would like to read it)
The researchers in this study found that introducing large amounts of alpha synuclein into cell cultures results in the initiation of the unfolded protein response. They also observed this phenomenon in genetically engineered mice that produce large amounts of alpha synuclein.
Thus, there is some evidence for eIF2alpha and unfolded protein response-related activities in Parkinson’s disease
So is there are evidence that Dibenzoylmethane might be neuroprotective for Parkinson’s disease?
Yes there is (sort of):
Title: A dibenzoylmethane derivative protects dopaminergic neurons against both oxidative stress and endoplasmic reticulum stress.
Authors: Takano K, Kitao Y, Tabata Y, Miura H, Sato K, Takuma K, Yamada K, Hibino S, Choshi T, Iinuma M, Suzuki H, Murakami R, Yamada M, Ogawa S, Hori O.
Journal: Am J Physiol Cell Physiol. 2007 Dec;293(6):C1884-94. Epub 2007 Oct 3.
PMID: 17913843 (This article is OPEN ACCESS if you would like to read it)
The investigators of this study found a derivative of dibenzoylmethane which they called 14-26 (chemical name 2,2′-dimethoxydibenzoylmethane) displayed neuroprotective functions both in cell culture and animal models of Parkinson’s disease. The researchers did not look at the unfolded protein response or eIF2alpha and PERK levels, nor did they determine if dibenzoylmethane itself exhibits neuroprotective properties.
This may now need to be re-addressed.
And is there any evidence trazodone having neuroprotective effects in other neurodegenerative conditions?
For a review of the neuroprotective effects of trazodone (and other anti-psychotic/anti-depressant drugs) in Huntington’s Disease – Click here.
This sounds very positive for Parkinson’s disease then, no?
Weeeeeell, there is a word of caution to be thrown in here:
There have been reports in the past of trazodone causing motor-related issues in the elderly. Such as this one:
Title: Can trazodone induce parkinsonism?
Authors: Albanese A, Rossi P, Altavista MC.
Journal: Clin Neuropharmacol. 1988 Apr;11(2):180-2.
This report was a single case study of a 74 year old lady who developed depression after losing her sister with whom she lived. She was prescribed trazodone, which was effective in improving her mood. Just several months later, however, she began presenting Parkinsonian symptoms.
Firstly the onset of a resting tremor in the left arm, then a slowing of movement and a masking of the face. The attending physician withdrew the trazodone treatment and within two months the symptoms began to disappear, with no symptoms apparent 12 months later.
And unfortunately this is not an isolated case – other periodic reports of trazodone-induced motor issues have been reported (Click here and here for examples). And this is really strange as Trazodone apparently has no dopaminergic activity that we are aware of. It is a serotonin antagonist and reuptake inhibitor (SARI); it should not affect the re-uptake of norepinephrine or dopamine within the brain.
Thus, we may need to proceed with caution with the use of Trazodone for Parkinson’s disease.
So what does it all mean?
The repurposing of old drugs to treat alternative conditions is a very good idea. It means that we can test treatments that we usually know a great deal about (with regards to human usage) on diseases that they were not initially designed for, in a rapid manner.
Recently, scientists have identified two clinically available drugs that have displayed neuroprotection in two different models of neurodegeneration. Without doubt there will now be follow up investigations, before rapid efforts are made to set up clinical trials to test the efficacy of these drugs in humans suffering from dementia.
Whether these two treatments are useful for Parkinson’s disease still needs to be determined. There is evidence supporting the idea that they may well be, but caution should always be taken in how we proceed. This does not mean that other clinically available drugs can not be tested for Parkinson’s disease, however, and there are numerous clinical trials currently underway testing several of them (Click here to read more on this).
We’ll let you know when we hear anything about these efforts.
EDITOR’S NOTE: Under absolutely no circumstances should anyone reading this material consider it medical advice. The material provided here is for educational purposes only. Before considering or attempting any change in your treatment regime, PLEASE consult with your doctor or neurologist. While some of the drugs discussed on this website are clinically available, they may have serious side effects. We urge caution and professional consultation before altering any treatment regime. SoPD can not be held responsible for any actions taken based on the information provided here.
The banner for today’s post was sourced from Linkedin
Last week a research report was published in the prestigious journal Science Translational Medicine (that means that it’s potentially really important stuff). The study involved a new drug that is being clinically tested for diabetes.
In last week’s study, however, the new drug demonstrated very positive effects in Parkinson’s disease.
In today’s post we will review the new study and discuss what it means for Parkinson’s.
Diabetic checking blood sugar levels. Source: Gigaom
FACT: One in every 19 people on this planet have diabetes (Source: DiabetesUK).
It is expected to affect one person in every 10 by 2040.
Diabetes (or ‘Diabetes mellitus’) is basically a group of metabolic diseases that share a common feature: high blood sugar (glucose) levels for a prolonged period. There are three types of diabetes:
- Type 1, which involves the pancreas being unable to generate enough insulin. This is usually an early onset condition (during childhood) and is controlled with daily injections of insulin.
- Type 2, which begins with cells failing to respond to insulin. This is a late/adult onset version of diabetes that is caused by excess weight and lack of exercise.
- Type 3, occurs during 2-10% of all pregnancies, and is transient except in 5-10% of cases.
In all three cases inulin plays an important role.
What is insulin?
Insulin is a chemical (actually a hormone) that our body makes, which allows us to use sugar (‘glucose’) from the food that you eat.
Glucose is a great source of energy. After eating food, our body releases insulin which then attaches to cells and signals to those cells to absorb the sugar from our bloodstream. Without insulin, our cells have a hard time absorbing glucose. Think of insulin as a “key” which unlocks cells to allow sugar to enter the cell.
What does diabetes have to do with Parkinson’s disease?
So here’s the thing: 10–30% of people with Parkinson’s disease are glucose intolerant (some figures suggest the percentage may be as high as 50%).
We do not know.
Obviously, however, this ratio is well in excess of the 6% prevalence rate in the general public (Source:DiabetesUK). We have discussed the curious relationship between diabetes and Parkinson’s disease in a previous post (click here to read it).
And the relationship between Parkinson’s disease and diabetes is not a one way street: A recent analysis of 7 large population studies found that people with diabetes are almost 40% more likely to develop Parkinson’s disease that non-diabetic people (Click here for more on this).
EDITORIAL NOTE HERE: We would like to point out that just because a person may have diabetes, it does not necessarily mean that they will go on to develop Parkinson’s disease. There is simply a raised risk of developing the latter condition. It is good to be aware of these things, but please do not panic.
We have no idea why there is an association between diabetes and Parkinson’s disease, but each month new pieces of research are published that support the connection between Parkinson’s and diabetes, and this all provides encouraging support for an ongoing clinical trial (which we will discuss below).
So what research has been done?
Well, just this year alone there have been some interesting studies reported. The first piece of research deals with a drug that is used for treating type-2 diabetes:
Title: Metformin Prevents Nigrostriatal Dopamine Degeneration Independent of AMPK Activation in Dopamine Neurons.
Author: Bayliss JA, Lemus MB, Santos VV, Deo M, Davies JS, Kemp BE, Elsworth JD, Andrews ZB.
Journal: PLoS One. 2016 Jul 28;11(7):e0159381.
PMID: 27467571 (This article is OPEN ACCESS if you would like to read it)
Metformin (also known as Glucophage) has been one of the most frequently prescribed drugs for the treatment of type 2 diabetes since 1958 in the UK and 1995 in the USA. The mechanism by which Metformin works is not entirely clear, but it does appear to increase the body’s ability to recognise insulin.
Metformin treatment has previously been found to be neuroprotective. The researchers in this study wanted to determine if a protein called ‘AMPK’ was involved in that neuroprotective effect. They generated cells that do not contain AMPK and grew dopamine neurons – the brain cells badly affected by Parkinson’s disease.
In both cell cultures and in mice, the researchers found that Metformin was neuroprotective both in normal conditions and in the absence of AMPK. The study could not explain how the neuroprotective potential of Metformin was working, but it adds to the accumulating pile of evidence that some diabetes treatments may be having very positive effects in Parkinson’s disease.
A second piece of research from early this year goes even further:
Title: Reduced incidence of Parkinson’s disease after dipeptidyl peptidase-4 inhibitors-A nationwide case-control study.
Authors: Svenningsson P, Wirdefeldt K, Yin L, Fang F, Markaki I, Efendic S, Ludvigsson JF.
Journal: Movement Disorders 2016 Jul 19.
Using the Swedish Patient Register, the researchers of this study identified 980 people with Parkinson’s disease who were also diagnosed with type 2 diabetes between July 1, 2008, and December 31, 2010. For comparative sake, they selected 5 controls (non-Parkinsonian) with type 2 diabetes (n = 4,900) for each of their Parkinsonian+diabetic subjects. Their analysis found a significant decrease in the incidence of Parkinson’s disease among individuals with a history of DPP-4 inhibitor intake.
DPP-4 inhibitors work by blocking the action of DPP-4, which is an enzyme that destroys the hormone incretin. Incretin helps the body produce more insulin only when it is needed and reduce the amount of glucose being produced by the liver when it is not needed. By blocking DPP-4, we are increasing the production of insulin.
Authors concluded that ‘clinical trials with DPP-4 inhibitors may be worthwhile’ in people with Parkinson’s disease.
So what was published last week?
Metabolic Solutions Development is a Kalamazoo (Michigan)-based company that is developing a new drug (MSDC-0160) to treat type 2 diabetes. Last week, Prof Patrik Brundin and colleagues from the Van Andel Institute in Grand Rapids published a research report that suggested MSDC-0160 may have very beneficial effects in Parkinson’s disease:
Title: Mitochondrial pyruvate carrier regulates autophagy, inflammation, and neurodegeneration in experimental models of Parkinson’s disease.
Authors: Ghosh A, Tyson T, George S, Hildebrandt EN, Steiner JA, Madaj Z, Schulz E, Machiela E, McDonald WG, Escobar Galvis ML, Kordower JH, Van Raamsdonk JM, Colca JR, Brundin P.
Journal: Sci Transl Med. 2016 Dec 7;8(368):368ra174.
The drug from Kalamazoo, MSDC-0160, functions by reducing the activity of a recently identified protein that carries pyruvate into mitochondria.
What does this mean?
Pyruvate is a very important molecule in our body. The body can make glucose from pyruvate through a process called gluconeogenesis, which simply means production of new glucose. Thus, pyruvate is essential in providing cells with fuel to create energy (for more on pyruvate, click here for a good review article).
Pyruvate is carried into the power house of the cell – the mitochondria – by a protein called mitochondrial pyruvate carrier (MPC). The drug from Kalamazoo, MSDC-0160, is a blocker of MOC. It reduces the activity of MPC.
MPC also has other functions. It is known to be a key controller of certain cellular processes that influences mammalian target of rapamycin (mTOR) activation. mTOR responds to signals to nutrients, growth factors, and cellular energy status and controls the cells response. For example, insulin can signal to mTOR the status of glucose levels in the body. mTOR also deals with infectious or cellular stress-causing agents, thus it could be involved in a cells response to conditions like Parkinson’s disease.
Things that activate mTOR. Source: Selfhacked
Given the interaction with mTOR, the researchers in Michigan hypothesised that MSDC-0160 might reduce the neurodegeneration of dopaminergic neurons in animal models of Parkinson’s disease.
And this is exactly what they found.
The researchers reported that MSDC-0160 protected dopamine neurons in a mouse model of Parkinson’s disease. It also protected human midbrain dopamine neurons grown in cell culture when they were exposed to a toxic chemical. In addition, it demonstrated neuroprotective effects in a worm (called Caenorhabditis elegans) that produces a lot of the parkinson’s related protein alpha synuclein. MSDC-0160 even slowed the cell loss observed in a genetically engineered mouse that exhibits a slow loss of dopamine neurons. Basically, treatment with MSDC-0160 protected the cells from whatever the researcher threw at them.
How did it do this?
The researchers found that MSDC-0160 was reducing mTOR activity and also initiating a process called autophagy (which is the garbage disposal system of the cell). By kick starting the rubbish removal system, the cells were healthier. In addition, treatment with MSDC-0160 resulted in less inflammation – or activation of the immune system – in the brain.
Sounds very interesting. When do clinical trials start?
We’re not sure. They will most likely be in the planning stages though. If MSDC-0160 is approved for diabetes, it will be easier to have it approved for Parkinson’s disease as well.
Other diabetes drugs, however, are currently being tested in clinical trials for Parkinson’s disease. Of particular interest is Exenatide, which is just finishing a placebo-controlled, double blind phase 2 clinical trial. We are expecting the results for that trial early next year. Previous clinical studies suggested very positive results for Exenatide:
Title: Exenatide and the treatment of patients with Parkinson’s disease.
Authors: Aviles-Olmos I, Dickson J, Kefalopoulou Z, Djamshidian A, Ell P, Soderlund T, Whitton P, Wyse R, Isaacs T, Lees A, Limousin P, Foltynie T.
Journal: J Clin Invest. 2013 Jun;123(6):2730-6.
PMID: 23728174 (This study is OPEN ACCESS if you would like to read it)
The researchers running this clinical study gave Exenatide to a group of 21 patients with moderate Parkinson’s disease and evaluated their progress over a 14 month period (comparing them to 24 control subjects with Parkinson’s disease). Exenatide was well tolerated by the participants, although there was some weight loss reported amongst many of the subjects (one subject could not complete the study due to weight loss). Importantly, Exenatide-treated patients demonstrated improvements in their clinician assessed PD ratings, while the control patients continued to decline. Interestingly, in a two year follow up study – which was conducted 12 months after the patients stopped receiving Exenatide – the researchers found that patients previously exposed to Exenatide demonstrated a significant improvement (based on a blind assessment) in their motor features when compared to the control subjects involved in the study.
Exenatide. Source: Diatribe
The results of that initial clinical study were intriguing and exciting, but it is important to remember that the study was open-label: the subjects knew that they were receiving the drug. This means that we can not discount the placebo effect causing some of the beneficial effects reported.
And Exenatide is not the only diabetes drug being tested
Pioglitazone is another licensed diabetes drug that is now being tested in Parkinson’s disease. It reduces insulin resistance by increasing the sensitivity of cells to insulin. Pioglitazone has been shown to offer protection in animal models of Parkinson’s disease (click here and here for more on this). And the drug is currently being tested in a clinical trial.
So what does it all mean?
People with diabetes appear to be more vulnerable than the general population to developing Parkinson’s disease, and many people with Parkinson’s disease have glucose processing issues. It would be very interesting to better understand the link between Parkinson’s disease and diabetes. Why is it that so many people with Parkinson’s disease are glucose intolerant? And why do so many people with diabetes go on to develop Parkinson’s? Answering either of these questions might provide further insight into how both conditions function. And given that drugs associated with one appear to help with the other only strengthens the curious association.
As mentioned above, 2017 will bring the results of Exenatide clinical trial, upon which a lot of hope is riding. If it provides positive benefits, then we will finally have a treatment that can slow the progression of the disease. In addition, we will be able to delve more deeply into how Exenatide is causing it’s effect. Positive outcomes for Exenatide will also open the flood gates for many of the other clinically approved diabetes medications which could be trialled on people with Parkinson’s disease.
So despite how you may be feeling about 2017 (based on the events of 2016), we here at the SoPD believe that there is a lot to look forward to in the new year.
The banner for today’s post was sourced from Diabetes60systems