The growth of developing oocytes and hypothalamus—pituitary—ovary functions in goldfish under absolute food deprivation

Food deprivation (FD) seriously affects puberty onset and oogenesis in the female fishes. It has been suggested that meal-responsive peptides interact with hypothalamus-pituitary-ovary (HPO) functions; however, current knowledge regarding the integration of metabolism with reproduction remains inconclusive. In the present study, we investigated the effects of 7 days absolute FD on the reproductive system of adult female goldfish ( Carassius auratus). The number of non-vitellogenic oocytes was higher in the food-deprived goldfish than those of fed goldfish, while the number of vitellogenic oocytes was lower ( P < 0.05). However, FD had no effects on gonadosomatic index, ovarian reserve, oocyte diameter at different growth stages, and circulating levels of 17-β estradiol and testosterone. Analysis of hypothalamus-pituitary hormones revealed no significant changes in kiss1, gprg54, or gnrh3 mRNA levels in the food-deprived goldfish, whereas circulating luteinizing hormone (Lh) level was increased (P < 0.05). These findings suggest that the FD–induced increase in Lh level was not mediated by activation of the Kiss-Gnrh system. Ovarian transcript of ghrelin O-acyltransferase ( goat) mRNA—which encodes the enzyme that octanoylates ghrelin—was also increased in the food-deprived goldfish, along with decreases in hepatosomatic and viscerosomatic indices. Taken together, our results show that FD inhibits the growth of developing oocytes along with enhancement of post-translational modification of ghrelin in the ovary. This study provides novel insight into the integration of metabolic signals with HPO hormones in the female fish.