Dietary and Gonadal Hormone Effects on Lipid Metabolism in the Rat.

Hepatic cholesterol, triglyceride, and phospholipid concentrations, plasma cholesterol levels, cholesterol biosynthesis, and fatty acid patterns in plasma lipids and liver lipid fractions, have been studied in intact, gonadectomized, and hormone-treated gonadectomized male and female rats fed a fat-free diet, a control diet containing fat, and a diet containing cholesterol, to determine relationships between diet, sex hormones, and lipid metabolism. Both estradiol benzoate and testosterone propionate affected lipid metabolism; in general, the estrogenic influence was more pronounced and more predictable. The greatest effects were found in animals fed the essential fatty acid-deficient diet (a sex difference in susceptibility to essential fatty acid deficiency has previously been reported). It is concluded that the effect of estrogenic deficiency on lipid metabolism includes: (a) decreased hepatic cholesterol biosynthesis ; ( b ) increased hepatic sterol ester and decreased phospholipid concentration ; (c) increased depletion of unsaturated fatty acid in plasma and liver during essential fatty acid deficiency; and ( d ) increase in severity of essential fatty acid deficiency symptoms, using as criteria the ratios of trienoic to tetraenoic fatty acids in plasma and liver lipids.