Diet-dependent effects of insulin infusion on the hepatic lipoprotein receptors and the key enzymes of bile acid synthesis in the hamster

The effects of an induced hyperinsulinemia on both the cholesterol and bile acid metabolisms were analyzed in the hamster. The role of dietary sucrose as modulator of these effects was evaluated by feeding the animals with tw o semi-synthetic diets containing a low (SD, 20%) and a high (LD, 62.5%) su crose proportion. Hamsters fed under basal nutritional conditions (chow die t, CD) were also used. LD enabled the consequences of an insulin infusion o n cholesterol gallstone formation to be evaluated. Subcutaneous osmotic pum ps were implanted in all the animals and delivered either 3 IU/day of insul in (insulin groups: CDI, SDI, LDI) or saline (control groups: CDC, SDC, LDC ). Several parameters bound to lipid metabolism were measured. The plasma c holesterol concentration remained constant in all the insulin treated group s compared to the controls. Phospholipid and triglyceride concentrations de creased in both the plasma and liver in the CDI and SDI groups. A lower SR- BI mass (around 50%) was found in the liver of CDI and SDI hamsters with co ncomitant higher hydroxy-methyl-glutaryl coenzyme A reductase activity. The LDL-receptor mass and cholesterol 7 alpha -hydroxylase activity in the LDI group were both decreased (-47%, -71% respectively). No variations in the cholesterol gallstone incidence were observed. In conclusion, chronic insul in infusion in growing hamsters induced similar effects on cholesterol meta bolism in the CD and SD groups but different ones, between diets containing a low (SD) and a high (LD) sucrose proportion. The distribution of triglyc erides and phospholipids in the plasma, liver and bile was also affected by the insulin infusion. (C) 2001 Elsevier Science Inc. All rights reserved.