Metformin and brown adipose tissue thermogenetic activity in genetically obese Zucker rats

The effect of chronic metformin treatment on brown adipose tissue thermogenetic activity was investigated in young genetically obese Zucker rats. The binding of [3H]GDP to brown adipose tissue mitochondria, expression of uncoupling protein mRNA in brown adipose tissue, weight gains and cumulative food intakes were measured in metformin (320 mg/kg orally for 12 days)-treated obese Zucker rats as well as in pair-fed--and in ad libitum--fed control obese rats. The weight gains were identically reduced in the metformin- and pair-fed control group compared to the ad libitum--fed rats. Metformin also significantly reduced cumulative food intake. The binding of [3H]GDP to brown adipose tissue mitochondria and the expression of uncoupling protein mRNA in brown adipose tissue were not modified by metformin. It is concluded that the weight gain reducing effect of metformin in obese Zucker rats is mainly due to reduced food intake and does not involve an effect of metformin on brown adipose tissue thermogenetic activity.