Effect of dietary excess leucine on the levels of branched chain alpha-keto acids and ketone bodies in blood and the liver of rats.

Male rats were fed either a 10% casein diet or a 10% casein diet supplemented with 5% leucine, and the levels of alpha-ketoisocaproic acid and ketone bodies were analyzed in blood and the liver. alpha-Ketoisocaproic acid in plasma increased significantly on the 1st day of feeding the leucine-supplemented diet and was maintained on the high level during the experimental period of 7 days. Other branched chain alpha-keto acids tended to decrease in plasma. beta-Hydroxybutyric acid in blood doubled its amount on the 1st day on the high leucine diet and was maintained high during the experimental period. The sum of acetoacetic acid and beta-hydroxybutyric acid in blood was kept on a level twice as high as that of the control group. Ketone bodies in the liver were similarly increased and the sum of acetoacetic acid and beta-hydroxybutyric acid in the liver corresponded to the level found inhibitory to NAD biosynthesis in in vitro system [YAMADA, O., et al.: Int. J. Vit. Nutr. Res. 53, 184 (1983)].