Effects of benfluorex on serum triacylglycerols and insulin sensitivity in the corpulent rat.

The JCR:LA-cp rat is obese, insulin resistant, and hyperlipidemic, and the males develop atherosclerosis and ischemic myocardial disease. Benfluorex at 35-40 mg.kg-1 body weight was administered in the food from 10 to 14 weeks of age and resulted in an initial 50% decrease in food consumption. Body weights of male and female rats initially decreased by about 7% and thereafter remained relatively constant, whereas control animals gained about 28% in weight over the treatment period. Pair-fed rats showed body weights virtually identical with those of benfluorex-treated animals. Benfluorex treatment and pair feeding decreased serum triacylglycerol concentrations by about 50%; there was a preferential loss of triacylglycerols containing longer chain fatty acids in the males, whereas this selectivity was not seen in the females. Hyperinsulinemic euglycemic insulin clamp studies were performed using [1-3H]glucose, a tracer that allows for the measurement of total glucose turnover, including hepatic uptake and release. In male cp/cp rats, hyperinsulinemia does not stimulate total glucose turnover, reflecting the very severe insulin resistance, and neither benfluorex treatment nor pair feeding increased total glucose turnover. Hyperinsulinemia in male cp/cp rats decreases hepatic glucose output, and benfluorex treatment or pair feeding reduced this insulin-mediated diversion of glucose to hepatic lipid synthesis. Hyperinsulinemia increases total glucose turnover in female cp/cp rats, and this was not increased further by benfluorex treatment or pair feeding. These effects emphasize the sex-specific differences in metabolic response of the rats to hyperinsulinemia and benfluorex treatment. Benfluorex ameliorates the obesity-insulin resistance-hyperlipidemia syndrome in this experimental model mainly by decreasing hyperphagia, with an accompanying improvement in hepatic glucose metabolism and a related reduction in hypertriglyceridemia.