The effect of ketone bodies on the carbohydrate metabolism of rat diaphragm

Abstract

The effect of ketone bodies on the in vitro carbohydrate metabolism of rat diaphragm was investigated. Acetoacetate depressed glycogen synthesis in rat diaphragm and slightly increased glucose utilization. These effects were dependent on the relative concentrations of acetoacetate and glucose. Acetoacetate depressed glycogen synthesis in rat-liver slices. As with the rat diaphragm the effect was dependent on the relative concentrations of acetoacetate and glucose. beta-Hydroxybutyrate at a concentration equivalent to that of acetoacetate was without effect on the glycogen synthesis and the glucose utilization of rat diaphragm. Higher concentrations resulted in an increased glycogen synthesis. Addition of beta-hydroxybutyrate to a medium containing acetoacetate cancelled the "acetoacetate effect". Methylene blue, like acetoacetate, caused a decrease in glycogen synthesis and an increase in glucose utilization. No "acetoacetate effect" was found with diaphragms of severely diabetic rats, or of rats fasted for 5-7 days. Addition of beta-hydroxybutyrate caused an increase of glycogen synthesis by the diaphragms of diabetic rats. The oxidation of serum fatty acids by rat diaphragm was markedly depressed by beta-hydroxybutyrate and acetone but only slightly by acetoacetate. The stimulation by insulin of glycogen synthesis from glucose by rat diaphragm was diminished by the addition of acetoacetate. Administration of acetoacetate in vivo depressed glycogen synthesis by the isolated rat diaphragm. The influence of acetoacetate persisted up to 6 hours after injection. Administration of beta-hydroxybutyrate in vivo following acetoacetate cancelled the "acetoacetate effect ".