Mechanism of liver lipid accumulation in low protein diet feeding. III. Triglyceride release and fatty acid oxidation by the perfused liver of rats fed a low protein diet.

Abstract

Livers of growing rats fed a 5 or 20 protein calories percent (PC%) diet containing purified whole egg protein for three weeks were perfused in situ and the release of triglycerides (TG) and the oxidation of fatty acid by the liver alone were estimated by infusing palmitic acid-1-14C to the perfusion medium. The release of TG from the liver of the 5 PC% group was significantly lower in both unfractionated perfusate plasma and perfusate plasma very low density lipoprotein (VLDL) than that of the 20 PC% group, whereas the content of liver TG of the 5 PC% group was higher than that of the 20 PC% group. Significantly lower radioactivity appeared in TG of both unfractionated perfusate plasma and perfusate plasma VLDL of the 5 PC% group than that of the 20 PC% group, while total radioactivity of liver TG was higher in the 5 PC% group than in the 20 PC% group. The 14CO2 production in the perfused liver of the 5 PC% group increased gradually with time rather than decreased in comparison with that of the 20 PC% group. These findings suggest that a major factor responsible for the liver lipid accumulation in rats fed the low protein diet is not an impaired fatty acid oxidation in the liver but an impaired secretion of TG from the liver.