The Relationship between Hepatic Lipogenesis and the Hepatic Concentration of some Metabolites in Chicks Fed the Diets Containing Various Levels of Protein and Fat

Abstract

The effects of dietary protein and fat levels on in vivo hepatic lipogenesis and on the hepatic concentration of various metabolites in chicks were investigated. Fatty acid synthesis in liver was depressed by increasing the dietary fat level. Also, the reduction in hepatic lipogenesis was observed when the dietary protein level was increased from 17 to 33%, but no further reduction in lipogenesis occurred in chicks fed the 67% protein diet. The ratio of lactate/pyruvate was calculated in order to estimate the redox state of cell cytoplasm of liver. The ratio was markedly decreased with increasing dietary fat. The ratio was also decreased when the dietary protein level was increased, but no significant difference in the ratio was observed between the chicks fed the 33% protein diet and those fed the 67% protein diet. The hepatic concentration of free CoA in chicks fed the 33% and 67% protein diets and the 11% fat diet was higher than that in chicks fed the 17% protein diet. The concentration of acetyl-CoA was decreased by increasing the dietary protein or fat level, but the reduction was not observed in chicks fed the 67% protein diet. The concentration of long-chain acyl-CoA was increased by feeding the 39% fat diet and the 33% and 67% protein diets to 4.8, 3.3 and 2.3 times the level in chicks fed the 17% protein diet, respectively. The concentration of citrate was markedly decreased by feeding the 67% protein diet, but feeding the 33% protein and the 11% and 39% fat diets had no effect on citrate concentration. Jpn. J. Zootech. Sci., 51 (9): [664][665][666][667][668][669][670][671][672] 1980 Hepatic lipogenesis in chicks is influenced by dietary protein as well as by dietary fat1, 2). An increase in the level of dietary fat or protein depresses fatty acid synthesis in chick liver. LEVEILLE et al.2) reported that the depressing influence of dietary protein on hepatic fatty acid synthesis in chicks was greater than that of dietary fat and suggested that dietary protein and fat depressed fatty acid synthesis through different mechanisms.It was shown in the previous paper3), however, that the hepatic activity of fatty acid synthesis in chicks fed the 67% protein diet for 10 days from hatching time was about 59% of the value observed in chicks fed the 17% protein diet, whereas feeding of 39% fat diet produced only slight lipogenesis. In this experiment, the effects of dietary protein and fat levels on hepatic lipogenesis in chicks were investigated in terms of the redox state in the cytoplasm of liver cell and the concentration of citrate (an activator of lipogenesis), long-chain acyl-CoA (an inhibitor of lipogenesis), and some other metabolites involved in lipogenesis.Jpn. J. Zootech. Sci., 51 (9): 664-672 664 1980