THE EFFECT OF PIOGLITAZONE ON GLUCOSE-METABOLISM AND INSULIN UPTAKE IN THE PERFUSED LIVER AND HINDQUARTER OF HIGH-FRUCTOSE-FED RATS

To investigate the effect of pioglitazone, a thiazolidinedione oral an tidiabetic agent, on the glucose and insulin metabolism in insulin res istance, a perfusion study of the liver and hindquarter was performed in high-fructose-fed rats. Male Wistar albino rats were assigned rando mly to one of the following diets for 2 weeks: (1) normal chow (contro l group), (2) a diet high in fructose (fructose group), or (3) a high- fructose diet plus pioglitazone (pioglitazone intake of similar or equ al to 10 mg/kg body weight; pioglitazone group). The elevated levels o f plasma insulin, triglyceride, and free fatty acids (FFA) in the fruc tose group were normalized by pioglitazone administration. In the perf used liver, the glucagon-induced increment in the glucose output of th e fructose (57.1 +/- 9.1 mu mol/g liver/20 min) and pioglitazone (44.7 +/- 10.1 mu mol/g liver/20 min) groups was significantly (P < .01) hi gher than that in the control group (27.6 +/- 5.7 mu mol/g liver/20 mi n). The level in the pioglitazone group was significantly (P < .05) lo wer than that in the fructose group. In the presence of 100 or 500 mu U/mL insulin, the insulin-mediated decrement in the glucagon-induced g lucose output of the fructose group (29.8 +/- 7.8 or 38.9 +/- 9.3 mu m ol/g liver/20 min) was significantly (P < .05) lower than that in the control (45.8 +/- 14.2 or 54.5 +/- 8.5 mu mol/g liver/20 min) and piog litazone (44.4 +/- 9.2 or 56.2 +/- 10.8 mu mol/g liver/20 min) groups, respectively. In the perfused hindquarter, glucose uptake in the fruc tose group (8.2 +/- 2.0 mu mol/g muscle/30 min) was significantly (P < .05) lower than that in the control (12.1 +/- 2.3 mu mol/g muscle/30 min) and pioglitazone (11.8 +/- 3.1 mu mol/g muscle/30 min) groups. In the presence of 100 or 500 mu U/mL insulin, glucose uptake in the fru ctose group (12.0 +/- 5.2 or 17.4 +/- 3.0 mu mol/g muscle/30 min) was significantly (P < .05) lower than that in the control (20.2 +/- 2.4 o r 23.0 +/- 3.1 mu mol/g muscle/30 min) and pioglitazone (17.8 +/- 2.4 or 20.7 +/- 2.0 mu mol/g muscle/30 min) groups, respectively. Insulin uptake by the liver and hindquarter was not significantly different in the control, fructose, and pioglitazone groups. These results indicat e that pioglitazone improves the increased glucagon-induced hepatic gl ucose output and decreases insulin-induced muscular glucose uptake wit hout altering insulin uptake in high-fructose-fed insulin-resistant ra ts. Copyright (C) 1998 by W.B. Saunders Company.