A high-fat diet has a tissue-specific effect on adiponectin. and related enzyme expression

Objective: This study was designed to test whether adiponectin plays a role in diet-induced obesity and insulin resistance and acts as a mediator to induce or inhibit specific metabolic pathways involved in lipid metabolism Research Methods and Procedures: Forty C57BL/6J male mice were fed either a high-fat (HF) or control diet for 4 months, and adiponectin, its receptors, and enzyme expression in liver and muscle tissue were measured. Results: Mice fed the HF diet exhibited significantly greater weight gain, abnormal oral glucose tolerance test curves, and elevated homeostasis model assessment of insulin resistance (5.3 +/- 0.89 vs. 2.8 +/- 0.39). A significant reduction of adiponectin RNA expression (51%) and protein levels (15%) was observed in the adipose tissue of HF animals; however, serum adiponectin levels did not differ between groups (7.12 +/- 0.34 mu g/mL vs. 6.44 +/- 0.38 mu g/mL). Expression of hepatic mRNA of AdipoR1 and AdipoR2 was reduced by 15% and 25%, respectively, in animals fed the HF diet. In contrast, receptor mRNA expression of AdipoR1 and AdipoR2 increased by 25% and 30%, respectively, in muscle tissue. No effect was found on hepatic adenosine monophosphate-activated protein kinase expression; however, a significant reduction of phosphoadenosine monophosphate kinase levels in muscles was observed. Hepatic acetyl-coenzyrne A carboxylase was similar between groups, but in muscles, the inactive form phosphoacetylcoenzyme A carboxylase was significantly reduced (p < 0.05). Discussion: The HF diet led to decreased insulin sensitivity accompanied by impaired activity of adiponectin-related enzymes in skele'tal muscles but not in the liver. These results suggest that the HF diet has a tissue-specific effect on adiponectin and associated enzyme expression.