Effect of dietary cholesterol on activity and mRNA levels of hepatic lipase in rat

VLDL metabolism in rats is affected by the concentration and source of dietary protein

The present study was designed to determine if changes in dietary protein level and source are related to changes in VLDL lipid concentrations and VLDL binding by hepatic membranes and isolated hepatocytes. Male Wistar rats were fed cholesterol-free diets containing 10, 20 or 30 g/100 g casein or highly purified soybean protein for 4 wk. Hepatic, plasma and VLDL lipids, VLDL apo B-100 and VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were determined. Increasing casein or soybean protein level (from 10 to 30 g/100 g) in the diet increased VLDL apo B-100, indicating an increase in the number of VLDL particles. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane increased when the protein level increased from 10 to 20 g/100 g in the diet and decreased with 30 g/100 g protein, regardless of protein type. The dietary protein source did not affect plasma total cholesterol concentrations at any protein level. Feeding 20 g/100 g soybean protein compared with casein lowered plasma triglyceride concentrations and VLDL number as measured by decreased VLDL-protein, -phospholipid, -triglyceride, -cholesterol and -apo B-100. VLDL uptake by isolated hepatocytes and VLDL binding to hepatic membrane were higher in rats fed soybean protein than those fed casein. The higher VLDL uptake could be responsible for the hypotriglyceridemia in rats fed soybean protein.

A cholesterol-rich diet causes a greater hypercholesterolemic response in pregnant than in nonpregnant rats and does not modify fetal lipoprotein profile

To determine whether pregnancy modifies the hyperlipidemic response to a cholesterol-rich diet, pregnant and virgin rats were fed a semisynthetic diet supplemented (CRD) or not (CD) with 2% cholesterol and 1% cholic acid and studied at d 20 of treatment and/or gestation. Plasma triglycerides, free fatty acids and glycerol and liver triglycerides were greater in pregnant than in virgin rats fed CRD. The increase in both plasma and liver cholesterol caused by CRD did not differ in the two groups. In rats fed CD, hepatic lipase activity in liver was lower in pregnant than in virgin rats, while in those fed CRD, virgin rats had lower activity than those fed CD. Plasma VLDL-triglycerides were higher and LDL-triglycerides lower in pregnant than in virgin rats fed CD. Among those fed CRD, pregnant rats had a higher triglyceride concentration in VLDL and HDL than virgin rats. Cholesterol concentration was higher in VLDL and IDL and lower in HDL in both groups fed CRD than in those fed CD, while cholesterol level in LDL was higher only in pregnant rats fed CRD than in those fed CD. Whereas placental cholesterol concentration was higher in pregnant rats fed CRD than CD, maternal CRD intake did not modify fetal plasma lipoprotein concentrations, fetal body weight or litter size, indicating a lack of cholesterol transfer by the rat placenta. Results therefore show a greater responsiveness to CRD in pregnant than in virgin rats, and we propose that CRD promotes greater liver VLDL-production and lower LDL removal in pregnant than in virgin rats.