Effects of dietary oat bran and diabetes on plasma and caecal volatile fatty acids in the rat

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Diets high in plant fibre, particularly viscous gums, are of potential benefit in the control of diabetes in man. This study compares the effects of oat bran, one such fibre preparation, with purified cellulose on volatile fatty acid metabolism in rats fed a high carbohydrate diet. Concentrations of total volatile fatty acids were significantly higher both in hepatic portal venous plasma and caecal contents of rats fed oat bran. Major differences were also found in the relative contributions of individual acids with proportionately less acetate and more propionate and butyrate in these animals compared with rats fed cellulose. In rats fed a standard laboratory diet, diabetes induced by streptozotocin produced a sustained increase in caecal and hepatic portal venous concentrations of acetate, propionate and butyrate. Because of the high simple carbohydrate content of the experimental diet, the tolerance of diabetic rats for the bran and cellulose diets was poor and no differences in VFA metabolism were observed after 24 hr of diabetes. It is concluded that volatile fatty acid concentrations were in proportion to the probable digestibility of the source of dietary fibre and are significant metabolic fuels liable to altered metabolism by insulin insufficiency.