The clustering (or aggregation) of the protein, alpha synuclein, is a cardinal feature of the Parkinsonian brain, and it is believed to be associated with the neurodegeneration that characterises the condition.
As a result, many pharmaceutical and biotech companies are focused a great deal of attention on identifying novel compounds that can enter the brain and inhibit alpha synuclein from aggregating. Recently, a collaboration of companies published the results of an amazingly large study highlighting novel inhibitors.
But an interesting aspect of the results was the ‘positive control’ compound they used: Epigallocatechin Gallate (or simply EGCG)
In today’s post, we will review the results of the study, discuss what EGCG is, and look at what is known about this compound in the context of Parkinson’s.
Every now and then, the research report of a huge study comes along.
And by that, I don’t mean that the results have a major impact. Rather, I am referring to the scope and scale of the work effort required to conduct the study. For example, the GIANT study which is looking for genetic variations associated with height (Click here to read a previous SoPD post that briefly touches on that study).
Recently, the report of one huge study was published:
Title: Potent α-Synuclein Aggregation Inhibitors, Identified by High-Throughput Screening, Mainly Target the Monomeric State
Authors: Kurnik M, Sahin C, Andersen CB, Lorenzen N, Giehm L, Mohammad-Beigi H, Jessen CM, Pedersen JS, Christiansen G, Petersen SV, Staal R, Krishnamurthy G, Pitts K, Reinhart PH, Mulder FAA, Mente S, Hirst WD, Otzen DE.
Journal: Cell Chem Biol. 2018 Aug 29. pii: S2451-9456(18)30271-X.
In this study, researchers from Arrhus University, Biogen, Amgen, Genentech, Forma Therapeutics, & Alentis Pharma screened almost 750,000 different compounds for their ability to interact with the Parkinsons-associated protein alpha synuclein.
And before we go any further, just take a moment to fully appreciate the size of that number again:
That is eye watering stuff! That is a “I need to sit down for a moment and let this sink in” kind of number. That is a “Are there that many compounds in all of the known universe?” number.
After reading the number, I was left wondering what each of the scientists involved in this study must have been thinking when the boss first said “Hey guys, let’s screen half a million compounds…. no, wait, better yet, why stop there. Let’s make it 3/4 of a million compounds”
How enthusiastic was the “Yes boss” response, I wonder?
All kidding aside, this is an amazing study (and the actual number of compounds screened was only 746,000).
And the researchers who conducted the study should be congratulated on their achievement, as the results of their study may have a profound impact in the longer-term for the Parkinson’s community – you see, the researchers found 58 compounds that markedly inhibited the aggregation of alpha synuclein, as well as another 100 compounds that actually increased its aggregation. A great deal of research will result from this single, remarkable piece of work.
But of particular interest to us here at the SoPD, was the activity of one of the positive control compounds that the researchers used in some of the tests.
What was the control compound?
In 2006, this research paper was published:
Title: Small molecule inhibitors of alpha-synuclein filament assembly
Authors: Masuda M, Suzuki N, Taniguchi S, Oikawa T, Nonaka T, Iwatsubo T, Hisanaga S, Goedert M, Hasegawa M.
Journal: Biochemistry. 2006 May 16;45(19):6085-94.
In this study, the researchers tested 79 different chemical compounds for their ability to inhibit the aggregation of alpha-synuclein. They found several compounds of interest, but one of them in particular stood out: EGCG.
The researchers found that EGCG robustly blocked the clustering of alpha synuclein.
And it was EGCG that was used as the positive control in the ‘750,000 compound study’ mentioned above.
In fact, when discussing their 58 most potent inhibitors of alpha synclein aggregation, the ‘750,000 compound study’ researchers wrote that they were “comparable with the most promising known fibrillation inhibitors (e.g., baicalein and EGCG) in their ability to suppress” aggregation (We shall be discussing baicalein in a separate up-coming SoPD post – another very interesting compound).
So what is EGCG?
The chemical structure of EGCG. Source: GooglePatents
Epigallocatechin Gallate (or EGCG) is a powerful catechin.
What is a catechin?
Catechins are a group of compounds that are found in tea, fruit, chocolate and wine. They belong to a family of nutrients called flavonoids (a large class of plant pigments), and have been linked to a variety of health benefits.
Importantly, catechins (particularly EGCG) are potent antioxidants.
And what are antioxidants?
Antioxidants are substances which limit oxidation.
And yes, I know what you are going to ask next: What is oxidation?
Oxidation is the loss of electrons from a molecule, which in turn destabilises that particular molecule. Think of iron rusting. Rust is the oxidation of iron – in the presence of oxygen and water, iron molecules will lose electrons over time. Given enough time, this results in the complete break down of objects made of iron.
Rusting iron. Source: Thoughtco
The exact same thing happens in biology. Molecules in your body are constantly going through a similar process of oxidation – losing electrons 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 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 situation can cause terrible damage, ultimately killing the cell itself.
Antioxidants are the good guys in this situation.
They are molecules that neutralise 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.
How free radicals and antioxidants work. Source: h2miraclewater
So EGCG has antioxidant properties?
Exactly. And in addition to that, as we mentioned above, EGCG was also a potent inhibitor of aggregating alpha synuclein.
What is meant by ‘aggregating alpha synuclein’?
In the Parkinsonian brain, a protein called alpha synuclein clumps (or aggregates) together, which is believed to lead to the appearance of Lewy bodies.
What are Lewy bodies?
Lewy bodies are dense circular clusters of alpha synuclein protein (and other proteins) that are found in specific regions of the brain in people with Parkinson’s (Click here for more on Lewy bodies).
A cartoon of a neuron, with the Lewy body indicated within the cell body. Source: Alzheimer’s news
The aggregated alpha synuclein protein, however, is not limited to just the Lewy bodies. In the affected areas of the Parkinsonian brain, aggregated alpha synuclein can be seen in the branches (or neurites; see black arrow in the image below) of cells. In the image below, alpha synuclein has been stained brown on a section of brain from a person with Parkinson’s.
Examples of Lewy neurites (stained in brown; indicated by arrows). Source: Wikimedia
When alpha synuclein protein is produced by a cell, it normally referred as a ‘natively unfolded protein’, in that is does not really have a defined structure. When it is first produced, alpha synuclein will look something like this:
Alpha synuclein. Source: Wikipedia
In this form, alpha synuclein is considered a monomer – which is a single molecule that can bind to other molecules. When it does bind to other alpha synuclein proteins, they form an oligomer (a collection of a certain number of monomers in a specific structure). In Parkinson’s, alpha synuclein also binds (or aggregates) to form what are called ‘fibrils’.
Microscopic images of Monomers, oligomers and fibrils. Source: Brain
And it is believed that the oligomer and fibril forms of alpha synuclein protein give rise to the aggregations of protein that go on to form the Lewy bodies we mentioned above:
Parkinson’s associated alpha synuclein. Source: Nature
Now, given this process – and its association with a neurodegenerative condition like Parkinson’s – you will appreciate that a lot of effort is being put into reducing this aggregation of alpha synuclein protein. It is hoped that by limiting this activity, we may be able to slow or stop completely the progression of the condition.
Hence, the ‘750,000 compound study’ mentioned at the top of this post (in which 5 biotech companies participated).
So EGCG is an antioxidant that also inhibits alpha synuclein aggregation?
Exactly: In addition to having antioxidant properties, EGCG is also remarkably good at blocking the production of alpha synuclein aggregates.
And there have been many studies that have demonstrated this effect:
Title: EGCG redirects amyloidogenic polypeptides into unstructured, off-pathway oligomers.
Authors: Ehrnhoefer DE, Bieschke J, Boeddrich A, Herbst M, Masino L, Lurz R, Engemann S, Pastore A, Wanker EE
Journal: Nat Struct Mol Biol. 2008 Jun; 15(6):558-66.
In this study, the researchers found that EGCG efficiently inhibits the formation of both alpha synuclein and Alzheimer’s associated beta amyloid fibrils. And it did this by directly binding to the native unfolded forms of the protein and prevented their conversion into the toxic forms of aggregates.
And other studies have reported even more impressive results:
Title: EGCG remodels mature alpha-synuclein and amyloid-beta fibrils and reduces cellular toxicity
Authors: Bieschke J, Russ J, Friedrich RP, Ehrnhoefer DE, Wobst H, Neugebauer K, Wanker EE.
Journal: Proc Natl Acad Sci U S A. 2010 Apr 27;107(17):7710-5. doi: 10.1073/pnas.0910723107.
PMID: 20385841 (This article is OPEN ACCESS if you would like to read it)
In this study, the researchers found that EGCG has the ability to not only block the formation of of alpha synuclein fibrils and stabilize monomers of alpha synuclein, but it can also bind to alpha synuclein fibrils and restructure them into the safe/non-toxic forms of aggregates.
And more recently, other researchers have extended these results:
Title: EGCG-mediated Protection of the Membrane Disruption and Cytotoxicity Caused by the ‘Active Oligomer’ of α-Synuclein.
Authors: Yang JE, Rhoo KY, Lee S, Lee JT, Park JH, Bhak G, Paik SR.
Journal: Sci Rep. 2017 Dec 20;7(1):17945.
PMID: 29263416 (This report is OPEN ACCESS if you would like to read it)
In this study, the researchers reported that EGCG facilitates the formation of a non-toxic oligomer form of alpha synuclein, and protects cells from the membrane disrupting toxic form of aggregated alpha synuclein.
And just when it sounds like EGCG is the perfect compound for Parkinson’s, another very recent study reports that EGCG also modulates the response of peripheral immune cells in a model of Parkinson’s:
Title: (-)-Epigallocatechin-3-gallate modulates peripheral immunity in the MPTP-induced mouse model of Parkinson’s disease.
Authors: Zhou T, Zhu M, Liang Z.
Journal: Mol Med Rep. 2018 Apr;17(4):4883-4888.
PMID: 29363729 (This report is OPEN ACCESS if you would like to read it)
In this study the researchers used a neurotoxic mouse model of Parkinson’s (MPTP) to assess the neuroprotective potential of EGCG. They found that EGCG not only protected dopamine producing cells (the cells most affected by Parkinson’s), but also reduced the levels of inflammatory factors (such as tumor necrosis factor-α and interleukin-6) in the peripheral blood of the mice.
There is a lot of evidence accumulating that EGCG is a really interesting compound for Parkinson’s (and that is the third use of the word ‘interesting’ in this post if you are keeping count, Chris).
Has EGCG been tested in the clinic for Parkinson’s?
Yes, it has.
The efficacy and safety of EGCG was tested in 480 de novo (recently diagnosed) people with Parkinson’s in China in a study supported by the Michael J Fox foundation (Click here to learn more about the details of that trial). The study was started in 2007, and the participants were to be treated for 1 year with one of three different doses of EGCG or a placebo treatment.
The results of this trial have not been published, but the Michael J Fox Foundation have a short summary on their website which reads:
To evaluate the safety, tolerability and efficacy of green tea polyphenols (GTPs) in slowing disease progression in patients with early PD, the team carried out a multi-center, double-blind, randomized, placebo-controlled, delayed-start study in 32 Chinese Parkinson Study Group (CPSG) sites. Study enrollees were 410 untreated PD patients with disease duration of less than five years and Hoehn & Yahr stage below 3 who were not heavy tea drinkers. Participants were randomized to one of three doses of GTP (0.4, 0.8 or 1.2 grams daily given in two equal oral doses) or matching placebo. After six months, placebo was switched to 1.2 grams daily of GTP. All patients were treated for 12 months.
The change in total UPDRS score from randomization to six months was significantly improved in GTP-treated groups as compared to the placebo group, but this was not observed at 12 months. In the delayed-start group, the change in UPDRS from six months (the start of active GTP) to 12 months was significantly improved. Insomnia was slightly increased in GTP-treated patients, but there were no other significant differences in adverse effects. GTP is well tolerated and appears to provide, at least, a mild symptomatic benefit in early untreated PD. (Source)
There is also a clinical trial just being completed, which is testing EGCG in multiple system atrophy (or MSA a condition very similar to Parkinson’s – Click here to read a previous SoPD post on MSA).
This more recent trial is called the PROMESA study:
Title: The PROMESA-protocol: progression rate of multiple system atrophy under EGCG supplementation as anti-aggregation-approach.
Authors: Levin J, Maaß S, Schuberth M, Respondek G, Paul F, Mansmann U, Oertel WH, Lorenzl S, Krismer F, Seppi K, Poewe W, Wenning G; PROMESA study group, Giese A, Bötzel K, Höglinger G.
Journal: J Neural Transm (Vienna). 2016 Apr;123(4):439-45.
In this study, 92 individuals with MSA have been randomly assigned to either the treatment group (EGCG) or the control group (Placebo – click here to read more about the details of the study). The study has evaluated the safety, tolerability and a potential disease-modifying effect of EGCG in the participants. We are currently awaiting the publication of those results (expect a follow up post when those results get published).
And as far as I’m aware, these are the only clinical studies of EGCG in the context of Parkinson’s (and again, I’m happy to be corrected here).
Why aren’t there more clinical studies of this compound?
Quite simply: It’s not patented.
There’s no protective advantage for any biotech firm/pharmaceutical company to try and take this compound through the expensive clinical trial process.
But numerous clinical studies for various medical conditions have suggested that EGCG is well tolerated. Oral administration of EGCG is rapidly absorbed through the gut (Source), and it can cross the protective blood–brain barrier (Source), so it is a shame that more research is not being done with this compound.
What is the best source of EGCG?
There are solid supplements of EGCG available, but these have recently been called into question.
The European Food Safety Authority (EFSA – the agency of the European Union that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain) has recently warned that food supplement doses of EGCG at 800 mg or more per day may be associated with signs of liver damage.
They are quick to reassure that this is only related to food supplements. Liquid infusions of EGCG appear to be safe (Click here to read more about this).
Liquid infusions of EGCG?
So Green tea is the best ‘liquid infusion’ source of EGCG.
Green tea. Source: BBC
But there is a great deal of variability in the amounts of EGCG across the different brands of green tea.
Consumerlab (which provides independent test results, reviews, ratings and comparisons of vitamins, supplements, herb and nutrition products) recently conducted an analysis of EGCG levels in different brands of green tea, and their results suggested that Teavana‘s Gyokuro green tea contains 250mg of catechins (1/3 of which is EGCG), as well as high levels of caffeine.
Remarkably, even some plain, old supermarket brands of green tea (such as ‘Lipton green tea bags’) also contain good levels of EGCG.
But be warned! According to the report, a lot of green tea products contain little – if any – EGCG, such as Diet Snapple Green tea. So caveat emptor.
What is the best way to prepare green tea to maximise the EGCG content?
To maximize EGCG content i your cuppa, one is advised to pour boiling water (not just hot water) over green tea leaves or tea bag, and let it sit for at least 10 minutes.
Are there other natural sources of EGCG?
Strawberries, raspberries, blackberries, plums, peaches, kiwi, and avocado all contain small amounts of EGCG, but green tea appears to be the best source.
So what does it all mean?
Quite simply, it means that I’m off to brew a pot of de-caffeinated green tea (most of the few side effects associated with green tea relate to caffeine), while we wait for the results of the PROMESA clinical study.
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. Dietary changes can impact the effectiveness of treatments. PLEASE speak with your medical physician before attempting any change in an existing treatment regime.
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