Pioglitazone versus metformin in two rat models of glucose intolerance and diabetes

Insulin resistance has been implicated in the pathogenesis of type 2 diabetes. High fat diets cause insulin resistance. Both metformin and pioglitazone are considered "insulin sensitizers" and used as antihyperglycemic agents for type 2 diabetes treatment. The aim of this study is to Compare pioglitazone and metformin effects on carbohydrate metabolism and insulin sensitivity in diabetic and glucose intolerant rats on high fat diet. Male albino rats were randomized to seven groups. The 1st group received high carbohydrate diet (control). The 2nd, 3rd and 4th groups received high sunflower oil diets for 6 weeks and either left untreated, or given pioglitazone or metformin during the last 3 weeks. The 5th, 6th, and 7th groups were made diabetic by STZ injection on day 15 of the 6 weeks-high fat diet regimen. They were either left untreated, or given pioglitazone or metformin during the last 3 weeks. High-fat diet induced glucose intolerance; represented by increase of serum glucose associated with increase in liver glucose-6-phosphatase and decreases in liver glucose-6-phosphate dehydrogenase and glucokinase activities. No significant differences were observed between pioglitazone and metformin. In diabetic rats, both pioglitazone and metformin decreased elevated serum glucose by approximately 30%. Only metformin increased hepatic glycogen, and normalized glucose-6-phosphatase activity. On the other hand, pioglitazone normalized elevated renal glycogen content and increased glucose-6-phosphate dehydrogenase activity. High sunflower oil diet impaired glucose tolerance. Pioglitazone and metformin had comparable effects on estimates of carbohydrate metabolism and insulin sensitivity in high-fat fed rats, but different effects in diabetic rats.