Butanediol and lipid metabolism

Young growing rats, chicks and pigs were fed diets containing graded levels of 1,3-butanediol (BD). Replacement of up to 20% of the dietary carbohydrate energy with BD did not affect body weight gain or food efficiency in these species. Blood beta-hydroxybutyrate levels were markedly elevated when BD was added to the diet. Plasma triglyceride response varied with species. In the rat, plasma triglyceride levels were decreased when BD was added to a high-carbohydrate diet. Plasma triglyceride levels were increased when BD-containing diets were fed to pigs and unchanged when chicks consumed diets containing BD. The hepatic lactate:pyruvate ratio was increased in rats fed BD and decreased in chicks fed BD. Hepatic long-chain acyl CoA levels were increased in rats, but not in chicks, fed BD. Addition of BD to a high-carbohydrate diet markedly decreased the rate of fatty acid synthesis, as measured in vitro or in vivo, in rat liver but not in rat or pig adipose tissue. Hepatic fatty acid synthesis in the chick was not affected by replacement of up to 18% of the dietary carbohydrate with BD. We propose that the hepatic conversion of BD to beta-hydroxybutyrate in the rat shifts the cytoplasmic redox state, reduces the glycolytic rate, and reduces substrate availability for fatty acid synthesis. Further, the concomitant shift in the mitochondrial redox state allows long-chain acyl CoA levels to increase. The overall effect is a decrease in the rate of fatty acid synthesis in livers of rats fed BD.