INFLUENCE OF SEXUAL STEROID HORMONES ON NUCB1, NUCB2, GHRELIN AND RELATED GENES IN GOLDFISH

UNNIAPPAN S; BERTUCCI JI; CANOSA LF

Ottawa

Congreso; NASCE Meeting; 2015

North America Society of Comparative Endocrinologiest

Nesfatin-1(encoded by nucleobindin2/NUCB2 gene) is an appetite inhibitory peptide, whileghrelin is an appetite- stimulatory hormone in goldfish. Both peptides are mealresponsive, and are involved in the regulation of reproduction in fish.However, the regulation of these peptides in vivo is poorly understood. Consideringthe abundant expression of these peptides in the gonads of goldfish, and itsreproductive functions, we hypothesized that sex steroids regulate both ghrelinand nesfatin-1. The aim of the present study was to characterize the effects ofestradiol (E2) and testosterone (T) on the expression mRNAs encoding NUCB2/nesfatin-1,ghrelin, ghrelin receptor and ghrelin O-acyl transferase (GOAT), the enzymethat acylates ghrelin in goldfish (Carassius auratus). First, adose-response assay was performed in which fish were intraperitoneally (ip)implanted with pellets containing 25, 50 and 100 μg/g body weight (BW) of E2 orT.After2.5 and 5 days, serum samples were collected, and E2 and T levels weredetermined by immunoassays. Observations from this first experiment allowed usto determine the appropriate steroid hormone doses (100 μg/g BW) andimplantation period (2.5 days) that achieves the highest E2 or T serum levels.In a second experiment, fish were ip implanted with pellets containing 100 μg/gBW of E2, T or without hormone (control). After 2.5 days, gene expression ingut, forebrain, hindbrain, hypothalamus and pituitary was measured usingreal-time qPCR. NUCB2/nesfatin-1 mRNA expression was increased in the forebrainfor T group and reduced in the gut and pituitary under both treatments. Ghrelinand GOAT expression was upregulated in the gut by both E2 and T treatments,while the same effect was observed for GHSR in the pituitary. Both treatmentsalso led to a reduction in ghrelin mRNA levels in the hypothalamus. Theseresults show, for the first time in fish, a modulation of NUCB2/nesfatin-1 andghrelin by sex steroid hormones. The interaction between sex steroids and genesimplicated in food intake regulation provides a possible explanation forseasonal changes in the endogenous metabolic hormone milieu in goldfish.