Evaluation of a single dose of intra-testicular insulin treatment in heat-stressed mice model.

Abstract

Insulin plays important role in testicular functions such as germ cell proliferation and steroidogenesis, despite its conventional role as a hypoglycaemic agent. It is also well known that testicular activity is severely get affected by heat stress and heat stress induces testicular pathogenesis. The effect of insulin on heat-induced testicular impairment has not been investigated. Thus, it is hypothesized that insulin might modulate testicular activity in a heat-stressed model. Experimental mice were separated into 4 groups; the first group was the normal control (CN), and the second group was subjected to heat stress (HS) by submerging the lower body part in a thermostatically controlled water bath maintained at 43°C for 15 min. The third and fourth groups were treated with a single dose of intra-testicular insulin (0.6IU/mice) before and after heat stress. Animal tissue samples were collected after 14 days of heat treatment. Insulin treatment did not improve the sperm parameters; however, both insulin pre and post-treatment improved the markers of spermatogenesis such as Johnsen score, germinal epithelium height and the number of stages VII/VIII. The histoarchitecture of testis also showed amelioration from heat-induced pathogenesis in the insulin-treated groups. Insulin treatment has also increased the proliferation of germ cells (increased PCNA and GCN), survival (Bcl2), and decreased apoptosis (active caspase-3). Furthermore, insulin treatment decreased MDA levels, without pronounced effects on the activities of antioxidant enzymes. Heat stress also decreased the circulating testosterone and oestrogen levels, and insulin treatment significantly increased oestrogen levels only. Although testosterone showed an increasing trend, it was insignificant. The expression of aromatase, AR, ER-α, and ER-β was down regulated by heat-stress and insulin treatment up regulated these markers. In conclusion, our results showed the amelioration of heat-induced testicular impairment by pre and post-intra-testicular insulin treatments. Insulin-associated improvements in the pre-and post-treatment groups suggested a preventive mechanism of insulin against heat stress in the testis.