Effect of Short-Chain Fatty Acids on Plasma Insulin in Ruminant and Nonruminant Species

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Abstract
Regulation of plasma insulin levels in the sheep, cow, rat, rabbit and pig was investigated utilizing a double antibody radioimmunoassay. In the sheep, infusion of the rumen metabolites, propionate and butyrate, increased plasma insulin levels approximately 4-fold and 14-fold, respectively, without affecting plasma glucose. All fatty acids containing 3-8 C atoms stimulated insulin production, valerate being the most effective. Acetate, acetoacetate and beta-hydroxybutyrate had no effect on plasma insulin. Infusion of glucose was much less effective than propionate, butyrate or valerate and there was no correlation between fasting glucose levels and fasting plasma insulin. Infusion of propionate into rats, rabbits or pigs had no effect on the plasma insulin, whereas both propionate and butyrate provoked a rise in plasma insulin in the cow. Propionate and butyrate are stimulators of insulin secretion in the sheep and cow but not of nonruminant species.