The Syrian golden hamster strain LPN: a useful animal model for human cholelithiasis.

The purpose of this study was to specify the main mechanisms at the origin of gallstone formation in very young (5-week old) or young adult (9-week old) LPN hamsters fed a sucrose-rich (normal lipid) lithogenic diet for one and four weeks, respectively. It was also to compare these mechanisms in the two strains of hamsters (LPN and Janvier) or when an anti-lithiasic diet was given by substituting 10% of the sucrose by beta cyclodextrin. The LPN strain of hamsters showed a very high incidence of cholesterol gallstones (73%) after receiving the lithogenic diet.

Hamsters predisposed to sucrose-induced cholesterol gallstones (LPN strain) are more resistant to excess dietary cholesterol than hamsters that are not sensitive to cholelithiasis induction.

We compared the effects of cholesterol feeding in male hamsters from two strains with different propensities to sucrose-induced cholelithiasis; Laboratoire de Physiologie de la Nutrition (LPN) hamsters are predisposed to developing biliary cholesterol gallstones, whereas Janvier (JAN) hamsters are not. When fed a basal control diet, LPN hamsters had a lower cholesterolemia (-21%, P = 0.01) than JAN hamsters, and a higher activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase in liver (+148%, P = 0.

Cholesterol, bile acid, and lipoprotein metabolism in two strains of hamster, one resistant, the other sensitive (LPN) to sucrose-induced cholelithiasis.

A comprehensive study of cholesterol, bile acid, and lipoprotein metabolism was undertaken in two strains of hamster that differed markedly in their response to a sucrose-rich/low fat diet. Under basal conditions, hamsters from the LPN strain differed from Janvier hamsters by a lower cholesterolemia, a higher postprandial insulinemia, a more active cholesterogenesis in both liver [3- to 4-fold higher 3-hydroxy 3-methylglutaryl coenzyme A reductase (HMG-CoAR) activity and mRNA] and small intestine, and a lower hepatic acyl-coenzyme A:cholesterol acyltransferase activity. Cholesterol saturation indices in the gallbladder bile were similar for both strains, but the lipid concentration was 2-fold higher in LPN than in Janvier hamsters.

Molecular basis of insulin action.

Considerable progress has been made in our understanding of the molecular mechanisms of insulin action. The insulin receptor is a membrane receptor possessing tyrosine kinase activity. The binding of insulin to its receptor induces autophosphorylation of the receptor on tyrosine residues and thereby stimulates its tyrosine kinase activity towards intracellular substrates such as Shc or IRS1.

Rat uncoupling protein 2 (UCP2): expression in obese ventromedial hypothalamus (VMH)-lesioned animals.

Background: The family of uncoupling proteins is thought to play an important role in the regulation of energy metabolism by uncoupling the respiratory chain reactions from ATP synthesis. The recently discovered uncoupling protein 2 (UCP2) is upregulated in genetically obese rodent models and during long term high fat feeding.

Aim: We have examined the UCP2 mRNA levels in liver, heart and white adipose tissue (WAT) of obese ventromedial hypothalamus (VMH)-lesioned rats, during the dynamic and the early stage of the static phase of obesity, before the appearance of most of the metabolic perturbations associated with long term established obesity.

Increased mitogen-activated protein kinase expression and activity in white adipose tissue of ventromedial hypothalamus-lesioned rats.

Ventromedial hypothalamus lesions in rats induce hyperphagia and hyperinsulinaemia associated with a rapid growth of white adipose tissue resulting in massive obesity. It has been shown previously that at an early stage after the lesion, during the dynamic phase of obesity, the white adipose tissue is hyper-responsive to insulin. In the present work, we show that the effects of insulin on the autophosphorylation of the insulin receptor and on its tyrosine-kinase activity towards endogenous substrates are similar in intact adipocytes of control and ventromedial hypothalamus lesioned rats.