Effect of Treadmill Running on Apelin and APJ Expression in Adipose Tissue and Skeletal Muscle in Rats Fed a High-fat Diet

Abstract Apelin, an adipokine and also a myokine, is involved in glucose homeostasis. In this study we investigated the effect of insulin resistance and exercise on the regulation of apelin and APJ in adipose tissue and skeletal muscle. After 20 weeks of a high-fat diet (HFD), rats showed severe insulin resistance, with increased fasting blood sugar and plasma insulin and impaired glucose tolerance. Plasma apelin immunoreactivity as well as apelin and APJ expression in adipose tissue and gastrocnemius muscle were significantly increased, with no difference in soleus muscle. Treadmill running completely ameliorated the HFD-induced insulin resistance, decreased plasma apelin level, and downregulated apelin and APJ expression in adipose tissue. However, apelin and APJ expression was upregulated in soleus and gastrocnemius muscle with treadmill training and a HFD. Exercise had a tissue-dependent effect on apelin and APJ expression in rats fed a HFD.