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A study published in Cell, by researchers from Washington Medical School in St Louis, claims to have found a compound that binds to a specific protein in the liver and helps to metabolise glucose and fat. This compound is also a component of lecithin, a food emulsifier, which may mean that in future lecithin will have a role to play in the control of blood fats and associated disease prevention.
A protein found in the nucleus of cells, peroxisome proliferator-activated receptor – alpha (PPAR-á) is known to regulate the metabolism of fat and glucose in the liver. Fibrate drugs, aimed at lowering cholesterol and triglycerides and elevating high density lipids in the blood, work by activating PPAR-á. The authors of this study, Lodhi et al, indicate that whilst fibrates activate this protein, a naturally occurring substance that does the same has not previously been identified.
Lecithin is found in many foods including egg whites, grain, fish, legumes, yeast and peanuts although most of that used commercially is derived from soya beans. Due to its ability to act as an emulsifier and to alter food taste and texture it is a common additive in a number of foods including margarine, mayonnaise and chocolate.
Lodhi et al created a strain of mice that could not make fatty acid synthase (FAS), an enzyme that converts sugars in food to fatty acids in the liver. It was discovered that these mice were just like animals which were not able to make PPAR-á. The mice had lower fasting insulin levels and were prone to develop fatty liver disease. The researchers found that when given fibrate drugs which activated the protein PPAR-á, the lipid levels in the mice returned to normal. On this basis, the scientists hypothesised that fatty acid synthase was also involved in the activation of PPAR-á. Lodhi et al then used mass spectrometry and gene expression studies to isolate the compound that activated PPAR-á in the liver. This compound, a phosphatidylcholine, is also a component of lecithin. According to the authors of the study, FAS had not previously been associated with the ability to activate PPAR-á due to the relative distance between the two proteins. PPAR-á is a nuclear receptor and therefore present in the nucleus of the cell. FAS however, is found in the cell cytoplasm. Clay Semenkovich, senior investigator on the study is quoted in Science Daily as saying that the “neighbourhoods” where these two proteins are located are not very close together. The synthase is way out in the cytoplasm – that is like being in the suburbs – whilst the PPAR-á lives right in the middle of the city. He said that since they are worlds apart, it is amazing that the two are linked. Semenkovich also notes that it is fortunate that such a common compound as lecithin can bind to a key drug target like PPAR-á and that this information could be used to make better drugs or to develop nutraceuticals. In future it may be possible to use products containing lecithin to control blood fat levels and to reduce the risk of diabetes, high blood pressure and cardiovascular disease using foods rather than medications.
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