Chronic intake of Dioscorea esculenta suppresses testicular atrophy, enhances the ability of protection from inflammation in type 2 diabetes rats

Dioscorea esculenta increases sex steroid hormones in obesity and type 2 diabetes that impairs steroidogenesis. However, the effects of chronic D. esculenta intake on testicular sex steroid hormone concentrations and testicular function especially protection from oxidative stress and inflammation is still unclear. The study assessed the effects of chronic D. esculenta intake and exercise training on testicular function in rats with type 2 diabetes. Twenty-week-old Otsuka Long-Evans Tokushima Fatty rats were randomly assigned to the control, exercise training (running at 25 m/min for 1 h, 5 days/week), and D. esculenta intake (0.3 % with normal feed) groups (n = 8 per group). Long-Evans Tokushima Otsuka rats served as the healthy controls (n = 7). Eight weeks of D. esculenta intake or exercise training significantly increased plasma concentrations of dehydroepiandrosterone (DHEA), free testosterone and 5α-dihydrotestosterone (DHT). No significant increases were observed in DHEA, testosterone, and DHT concentrations in the testis. Androgen receptor (AR) expression was significantly increased by D. esculenta intake and exercise training. The expression of cathepsin L, which is involved in sperm modification, did not significantly change, whereas the expression of glutathione peroxidase 4 (GPx4), which protects sperms from oxidative stress, significantly increased in the D. esculenta group. Additionally, metabolic clearance rate (MCR), an index of insulin resistance, significantly correlated with testicular weight and GPx4 expression. These results suggest that improvement in MCR through D. esculenta intake suppresses testicular atrophy and enhances the ability of protection from oxidative stress and inflammation in rats with type 2 diabetes.