INFLUENCE OF PROTEIN LIPID RATIO OF DIET ON CHOLESTEROL-SYNTHESIS ANDESTERIFICATION IN EEL LIVER

The effect of protein/lipid ratio of diets on hepatic cholesterol has been studied in European eel and correlated with changes in the main e nzymes responsible for cholesterol metabolism. The growth rates of ani mals were similar when dietary lipid level was 12%. However, a 25% pro tein/20% fat (25/20) diet produced a decrease in the weight gain when compared with that observed after feeding a 30/20 diet. At low fat lev el (12%), the decrease in dietary protein produced a little but signif icant increase in total cholesterol, mainly due to the esterified form . On the contrary, a 25/20 diet produced a lower cholesterol accumulat ion than that a 30/20 diet. These results suggest that a minimal prote in level was required for an optimal utilization of dietary fat for ch olesterol deposition in liver. No significant differences were found i n 3-hydroxy-3-methylglutaryl-CoA reductase, mevalonate kinase, mevalon ate 5-phosphate kinase and mevalonate 5-pyrophosphate decarboxylase wh en compared the effect of 40/12 and 30/12 diets as well as that of 30/ 20 and 25/20 diets, suggesting that differences in hepatic cholesterol content were not due to differences in cholesterol synthesis but in t he transport to the liver. Changes in the esterified cholesterol were parallel to those found in acyl-CoA : cholesterol acyltransferase, cor roborating the main role of this enzyme in the regulation of hepatic c holesterol esterification.