Dioscorea esculenta ‐induced increase in muscle sex steroid hormones is associated with enhanced insulin sensitivity in a type 2 diabetes rat model

The effects of chronic Dioscorea esculenta administration and exercise training on muscle sex steroid hormone levels and insulin resistance in type 2 diabetes rats was assessed. Twenty-week-old male Otsuka Long Evans Tokushima Fatty (OLETF) rats were assigned randomly to the control, D. esculenta treatment, D. esculenta with 5α-reductase inhibitor treatment, or the exercise training groups (running at 25 m/min for 1 h, 5 d/wk; n = 10 each group). Eight weeks of D. esculenta treatment or exercise training significantly attenuated the increase in plasma insulin and fasting glucose levels. Plasma and muscle concentrations of dehydroepiandrosterone and 5α-dihydrotestosterone (DHT) and the expression of 5α-reductase increased significantly in the D. esculenta-treated and exercise training groups, and both treatments led to the upregulation of glucose transporter-4 translocation with concomitant increases in PKB and PKC-ζ/λ phosphorylation. Furthermore, the glucose metabolic clearance rate, which represents insulin sensitivity, increased significantly in both the D. esculenta-treated and exercise training groups. These effects were suppressed by administration of the DHT synthetic inhibitor. Together, these findings suggest that the D. esculenta-induced increase in muscle sex steroid hormone levels helps decrease insulin resistance in type 2 diabetes.-Sato, K., Fujita, S., Iemitsu, M. Dioscorea esculenta-induced increase in muscle sex steroid hormones is associated with enhanced insulin sensitivity in a type 2 diabetes rat model.