Clofibrate improves glucose tolerance in fat-fed rats but decreases hepatic glucose consumption capacity

High-fat (HF) diets cause glucose intolerance. Fibrates improve glucose tolerance. We have tried to obtain information on possible hepatic mechanisms contributing to this effect.

Rats were fed a HF diet, isocaloric with the control diet, for 3 weeks without or with clofibrate. Several parameters related to liver glucose and glycogen metabolism were measured.

Clofibrate prevented the induction of glucose intolerance by 3 weeks HF feeding. Improved glucose tolerance by clofibrate was not due to increases in glucose phosphorylation or glycolysis in the liver, since both the HF diet and clofibrate suppressed glucokinase and pyruvate kinase activities with no effect on glucose 6-phosphatase. Clofibrate decreased glycogen storage in both control and HF rats. Clofibrate, with and without HF feeding, inhibited weight gain during the experimental period. Body temperature was significantly elevated by clofibrate, indicative of an increased basal metabolic rate. The capacity of liver mitochondria to oxidize long-chain fatty acids increased by clofibrate treatment. Mitochondria did not show uncoupling.

Clofibrate does not improve glucose tolerance by improving hepatic glucose or glycogen metabolism. Peripheral glucose oxidation may be facilitated by increased energy dissipation.