Short chain fatty acids and metabolic effects in humans

Abstract Short chain fatty acids are the major end products of dietary fiber degradation by anaerobic bacteria in the large bowel. The principal short chain fatty acids are acetate, propionate and butyrate. They are rapidly absorbed, stimulate salt and water absorption and provide an energy source for the colonic epithelium. Butyrate is mostly utilized as an energetic substrate by the colonocytes. It has been suggested that short chain fatty acids could contribute to the lipidemic and glycemic effects of fiber. In isolated hepatocytes, acetate inhibits glycolysis and stimulates gluconeogenesis while propionate has the opposite effects. Propionate inhibits cholesterol synthesis in vitro. They are very few studies in healthy humans. The acute intake of acetate does not seem to affect metabolism in man. No mention is made of its influence in case of chronic intake. The studies reveal the propionate tendency to reduce glycemia in fasting subjects and to enhance their sensitivity to insulin. The real part played by the short chain fatty acids in the glucose metabolism causes controversy and further investigations into their chronic intake in man are required.