Aerobic Exercise Training Attenuates Obesity-Related Hypogonadism in Male Rats

Introduction: Hypogonadism is associated with obesity and other features of metabolic syndrome in males. Purpose: The purpose of this study was to compare lean and obese male Zucker rats on their reproductive endocrine function in response to aerobic exercise training. Methods: Lean (Fa/Fa) and obese (fa/fa) male Zucker rats at 2 months of age were randomly assigned to a sedentary and an aerobic exercise training group (lean sedentary, n = 7; lean exercise, n = 8; obese sedentary, n = 7; obese exercise, n = 7). The exercise group walked on a rat treadmill, starting at 10 m.min(-1) for 20 min and building up to 20 m.min(-1) for 60 min, five times per week for 8 wk. Serum levels of total and free testosterone and testicular levels of testosterone, as well as epididymal and inguinal adipose tissue monocyte chemotactic protein 1 release levels, were measured. Results: There were significant obesity-by-exercise interactions on serum levels of total and free testosterone and testicular levels of testosterone (all P < 0.05). Compared to lean sedentary rats, obese sedentary rats had lower serum and testicular testosterone levels (0.72- to 0.74-fold, all P < 0.001). There were no group differences between lean sedentary and lean exercise rats on serum and testicular testosterone levels. However, compared to the obese sedentary group, the obese exercise group had higher serum and testicular testosterone levels (1.37- to 1.47-fold, all P < 0.05). In the whole cohort, serum and testicular testosterone levels were inversely related to epididymal adipose tissue monocyte chemotactic protein 1 secretion (r = -0.40 to r = -0.45, all P < 0.05). Conclusions: Our results support that aerobic exercise training could improve severe obesity-related hypogonadism in male Zucker rats. The underlying mechanism needs to be further clarified.