Researchers, publishing in Journal of Biological Chemistry, looked at a compound that is found in green tea and looked, in vitro, at its effects on amyloid fibrils, which are associated with atherosclerotic plaques.
Dr Paul Kroon, Research Leader (Polyphenols and Health), Quadram Institute Bioscience, said:
“This is an interesting report showing that in laboratory experiments, the tea polyphenol epigallocatechin gallate can change the structure of amyloid fibrils that that are formed from a protein called ApoA-1 in the presence of another component in blood, heparin. Normal ApoA-1 amyloid fibrils are associated with increasing amounts of atherosclerotic plaque and decreased plaque stability, i.e. they are more likely to rupture and cause a heart attack or stroke. The authors show that in the presence of epigallocatechin gallate, the structure of the fibrils that form are altered and they are no longer toxic. However, the concentrations required for this effect to be demonstrated in the lab are much higher than can be achieved by people drinking green tea or taking green tea capsules safely. Indeed, there are a number of potentially beneficial activities of epigallocatechin gallate that have been shown in the laboratory, but these effects could not be demonstrated in humans because the compound is poorly absorbed and quite unstable in the body. Although the authors recognise this and argue that it may be possible to produce a similar compound that is more bioavailable and stable and able to reach the concentrations required, this is likely to be extremely challenging because the gallate ester part of the molecule that is required for it to be effective is also responsible for its instability and poor bioavailability.”
Prof Tim Chico, Professor of Cardiovascular Medicine and Honorary Consultant Cardiologist at the University of Sheffield, said:
“This is a very preliminary biochemical study. It found that a compound found in green tea (called EGCG) helps to break up proteins that are found in some diseased blood vessels, which is interesting. However, it is far too early to suggest that this will lead to new treatments. The researchers have not yet looked at whether EGCG makes any difference to any form of disease in animals or humans, and there was some suggestion that high concentrations of EGCG might reduce survival of important human cells.
“It is important therefore that the (slightly exaggerated) press release does not raise false expectations about the implications of this discovery for patients. There are thousands of researchers working across the globe using many different approaches to try to tackle heart disease, and people should be encouraged that we are making great progress. However, adopting a healthy active lifestyle, eating a balanced diet, not smoking, and maintaining a healthy weight remain the best ways to reduce our risk of heart disease.
“Should you drink green tea? Yes, if you like it but not because of this research.”
Dr Amitava Banerjee, Senior Clinical Lecturer in Clinical Data Science at University College London, said:
“Green tea consumption has been associated with reduced mortality from cardiovascular disease (e.g. heart attacks and strokes) in a large meta-analysis (pooling of data from existing studies) (1). The possible mechanism of action of green tea is not fully known. The major cause of cardiovascular disease is atherosclerosis, the “furring up” of arteries with fatty deposits. A protein called apolipoprotein A-1 (apoA-1) can form amyloid deposits in atherosclerosis, and also in Alzheimer’s disease. In this study, in vitro experiments showed that epigallocatechin-3-gallate (EGCG), found in green tea, bound to amyloid fibres of apoA-1, perhaps making these fibres less damaging to blood vessels.
“This is a laboratory, in vitro study under controlled experimental conditions, and does not prove that the same happens in vivo. The effect of EGCG will only be significant if it has an impact on “hard outcomes” such as reducing the rate of heart attack or death, which needs to be tested in clinical trials. In short, these are preliminary findings, which may lead to development of new drugs for the treatment of atherosclerosis. Before we advocate large-scale consumption of green tea, we need far more compelling evidence at population level. There are already many well-established ways to prevent (e.g. stopping smoking, increasing physical activity, improving diet) and treat (e.g. aspirin, statins) atherosclerosis, which are still under-used. As a cardiologist, I will continue to focus on these approaches.”
* ‘Epigallocatechin-3-gallate remodels apolipoprotein A-I amyloid fibrils into soluble oligomers in the presence of heparin’ by David Townsend et al. was published in Journal of Biological Chemistry on Friday 1st June.
Dr Amitava Banerjee: No conflicts of interest
Prof Tim Chico: No conflicts of interest