Gametogenic and steroidogenic action of kisspeptin-10 in the Asian catfish, Clarias batrachus: Putative underlying mechanistic cascade

Unlike mammals, two kisspeptins genes encoding, kiss1 and kiss2 are detected in fishes with highly varied and contradictory difference in their reproductive activities. The present study was undertaken to examine the direct action of kisspeptin-10 and its role in gonadal activities in the gonadally quiescent Asian catfish using native mammalian kisspeptin decapeptide (KP-10) involving in vivo and in vitro approaches. The in vivo KP-10 treatment caused precocious onset of gametogenesis and its rapid progression, as was evident from the appearance of advanced stages of ovarian follicles in ovary, and advanced germ cells (spermatocytes/ spermatids) in the testis of the treated Clarias batrachus in comparison to the control gonads. It also elevated the steroid levels in gonads of the catfish in vivo and in vitro conditions. Simultaneously, it increased the expressions of key steroidogenic enzymes like 3 beta-HSD, 17 beta-HSD, and StAR protein, responsible for transfer of cholesterol from outer to inner membrane of the mitochondria of steroidogenic cells. Concurrently, it augmented the activities of 3 beta-HSD and 17 beta-HSD in the ovarian explants. The expressions of MAPK component (pERK1/2 and ERK1/2) were also upregulated by KP-10 in gonadal explants. Thus, the data suggest that kisspeptin-10 stimulates gametogenesis by enhancing gonadal steroid production. The study also describes the putative mechanistic cascade of steroidogenic actions of kisspeptin-10 in the catfish so much so in teleost fish. The study also suggests that, kisspeptin may act locally to regulate gonadal activities in an autocrine/paracine manner, independent of known extra-gonadal factors in the catfish.

Automated summary

The study shows that kisspeptin-10 stimulates gametogenesis in catfish by enhancing gonadal steroid production. It describes the cascade of steroidogenic actions of kisspeptin-10 in the catfish and suggests that kisspeptin may act locally to regulate gonadal activities in an autocrine/paracrine manner independently of known extra-gonadal factors.