Relationships between the Concentration of Liver Metabolites and Ketogenesis in Chickens Fed “Carbohydrate-free” Diets

Abstract

The effects on ketogenesis of feeding growing chickens diets in which all nonprotein calories were supplied by either soybean oil or soybean oil fatty acids were studied. A glucose reference diet was fed for comparison. Concentrations of several metabolites in liver, frozen in situ with the freeze-clamp technique, showed a general increase in those compounds associated with ketogenesis, and a general decrease in precursors of glucose, including citrate, when the “carbohydrate-free” diets were fed. Deletion of dietary carbohydrate decreased the NAD/NADH ratio in liver but oxaloacetate content was not decreased proportionately. In the absence of any significant dietary effect on the specific activity of the acetoacetate synthesis system, citrate synthase or citrate-cleavage enzyme, it is proposed that the utilization of acetyl-CoA shifts from the normal oxidative pathway to ketogenesis when the “carbohydrate-free” diets were fed, because acetyl-CoA is transported out of the mitochondria to the cytoplasm, where acetoacetate synthesis occurs in chicken liver.