Detection of Mitochondrial‐Derived Peptide Humanin in Semen and Reproductive Tract of Caprine Along With Its Relation to Seasonality

Humanin is the first short peptide in a speculated group of peptides produced by mitochondria that possess potent cytoprotective properties against various forms of stress. Despite being a prevalent peptide in testes and spermatozoa, there has been no report on the identification or quantification of humanin in buck sperm cells or the reproductive tract. This study aimed to establish the presence of humanin in the epididymis, testes and semen of Sirohi and Barbari bucks, whereas also assessing its seasonal expression, as goats are reported to be seasonal breeders in India. A total of 12 bucks were selected, and an indirect immunofluorescence test was conducted to detect humanin using a commercially available anti‐humanin antibody. Immunofluorescence examination of the male reproductive tract revealed the presence of green fluorescence, indicating humanin, in the elongated spermatids of the caput epididymis and the interstitial space of the testicles. In ejaculated spermatozoa, humanin was localised in the neck and acrosomal regions. Humanin was also observed in the upper middle region of ejaculated spermatozoa. However, during the rainy season, humanin expression was stronger or brighter, and throughout the summer and winter, there was little fluorescence. The rainy season was also markedly associated with increased levels of sperm concentration, progressive motility and mitochondrial membrane potential in semen. However, superoxide dismutase activity and lipid peroxidation levels also exhibited substantial seasonal variation.