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 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 nonvitellogenic oocytes was higher in the food-deprived goldfish than in fed goldfish, whereas 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 posttranslational modification of ghrelin in the ovary. This study provides novel insight into the integration of metabolic signals with HPO hormones in the female fish.NEW & NOTEWORTHY Food deprivation (FD) seriously interferes with the female reproductive system. Our findings show FD-inhibited growth of developing oocytes along with decrease in hepatosomatic index, and increase in the ovarian goat mRNA encoding the enzyme for the acyl-modification of ghrelin. Sex steroid levels and kiss1, gpr54, and gnrh3 mRNAs remained unchanged, whereas circulating Lh was increased under FD. This study provides novel information to better elucidate integrative physiology of hypothalamus-pituitary-ovary with oocyte growth under FD.