Abstract
Recently, gradual decline in human sperm production has become a serious worldwide concern because it leads to increased rates of infertility. Endocrine disrupters, lifestyle changes, and varicocele, all of which elevate testicular temperature, are thought to be the main causes of this decline. The present study aimed to determine whether the dietary phytochemicals Angelica keiskei (Ashitaba) powder (57.5 mg/kg) and its functional component, xanthoangelol (3 mg/kg), can prevent heat stress-induced impairment in sperm density and quality in mice. Sperm parameters were analyzed 28 days after mice exposure to heat. Supplementation with Ashitaba powder completely prevented heat-induced impairment in sperm parameters, including densities of motile sperms and progressive sperms (> 25 μm/sec), and amplitude of lateral head displacement. Xanthoangelol did not exert a complete protective effect; nevertheless, it significantly prevented heat stress-induced reduction in most parameters. Both Ashitaba powder and xanthoangelol elevated the expression of the widely expressed heat shock proteins (HSPs) Hspa1a and Hsp40 and the antioxidant enzyme glutathione synthase in non-stressed testes. Ashitaba powder significantly prevented heat stress-induced reduction in the expression of Hspa1l and Hspa2, which are highly expressed in the testes and critical for fertility. Our results showed that Ashitaba powder and xanthoangelol protected testicular cells from heat stress, probably by elevating the levels of antioxidant enzymes and HSPs. Supplementation with dietary functional phytochemicals may help prevent heat stress-induced male infertility.