Effect of Exercise Training on Adiponectin Receptor Expression and Insulin Resistance in Mice Fed a High Fat Diet

Abstract

Problem statement: Adiponectin is an adipocyte secreted hormones, exerts its effects via the specific receptors. AdipoR1 and adipoR2 and plays a pivotal role in lipid and glucose metabolism. Approach: We investigated the effect of increased physical activities on insulin resistance and if this effect is modulated through adiponectin receptor expression. Results: We also assessed the effect of High Fat Diet (HFD) on adipoRs expression. Mice were subjected to 16 weeks of HFD protocol then to 4, 6 and 8 weeks of exercise training. Following the experimental protocol the fasting plasma glucose, insulin and index of Homeostasis Model Assessment of insulin Resistance (HOMA-R) were evaluated. The mRNA expression of adiponectin receptors genes were also analyzed using reverse transcription RT-PCR. The consumption of high fat diet by the mice for 16 weeks resulted in a significant increase in weight associated with insulin resistance and associated with significant decrease in adiponectin receptors R1 and R2 expression in both liver and skeletal muscle. Exercise training for 4 weeks resulted in a significant improvement in the insulin resistance state, significant increase in expression of AdipoR1 and AdipoR2 in both liver and skeletal muscles. On increasing duration of exercise training for 6 weeks and 8 weeks there was significant improvement in insulin resistance and significant increase in the expression of AdipoR1 in liver, AdipoR1 and AdipoR2 in muscle, whereas liver AdipoR2 expression was significantly decreased. Conclusion/Recommendations: we conclude that the exercise training improves insulin sensitivity and up-regulates mRNA expression of AdipoR1 in both skeletal muscle and liver in mice and AdiopR2 in muscle and this suggests that the insulin sensitizing effect of exercise training may be mediated even partially through increased adiponectin receptor expression and up regulation of adiponectin receptors reaches certain level and increasing the duration of exercise adds no more improvement to insulin sensitivity or adiponectin receptor expression.