Resistance exercise-induced increase in muscle 5α-dihydrotestosterone contributes to the activation of muscle Akt/mTOR/p70S6K- and Akt/AS160/GLUT4-signaling pathways in type 2 diabetic rats.

Effects of increase in muscle 5α-dihydrotestosterone (DHT) levels caused by resistance exercise on regulation of mammalian target of rapamycin (mTOR)- and glucose transporter 4 (GLUT4)-signaling pathways in type 2 diabetic rats were assessed. Twenty-week-old type 2 diabetic rats were randomly divided into the resting control, immediately, 1 hour, or 3 hours after resistance exercise, with or without the pretreatment of 5α-reductase inhibitor. Immediately or 1 hour after exercise, levels of 5α-reductase and DHT as well as phosphorylation levels of AMP-activated protein kinase (AMPK), TBC1 domain family member 1 (TBC1D1), and protein kinase B (Akt) in muscle were significantly elevated. Phosphorylation of muscle Akt substrate of 160 kDa (AS160) and translocation levels of GLUT4 at 1 and 3 hours after resistance exercise were significantly elevated. Additionally, resistance exercise significantly activated the phosphorylation of muscle mTOR immediately, and at 1 and 3 hours and of p70 ribosomal S6 kinase (p70S6K) at 1 and 3 hours. However, pretreatment with the 5α-reductase inhibitor significantly attenuated the exercise-induced activation of Akt/mTOR/p70S6K and Akt/AS160/GLUT4 signaling, but did not affect AMPK/TBC1D1/GLUT4 signaling. These findings suggest that resistance exercise-induced increase in muscle DHT synthesis may contribute to activation of Akt/mTOR/p70S6K- and Akt/AS160/GLUT4 signaling pathways in type 2 diabetic rats.