Abstract

Endocrine systems are well known as primary regulators of growth in vertebrates. Neuropeptide Y (NPY), a 36-amino acid peptide, regulates a variety of physiological functions. Among the brain orexigenic signaling molecules, NPY is the most powerful central enhancer of appetite and has a key role to stimulate food intake in vertebrates. Expression of NPY is mostly distributed in the central nervous system. Examination of the role of dietary conditions in regulating endocrine activity in fish may provide practical information on the physiological consequences of alterations in diet composition and dietary conditions and evolution of the regulation of hormone production in vertebrates. In the present study, we analyzed the effect of diet composition on NPY gene expression in the brain of gilthead sea bream (Sparus aurata). During 37 days two groups of fish were fed ad libitum with either a high protein/low carbohydrate (HLL) or a low protein/high carbohydrate (LLH) diet. Another group of fish was submitted to starvation for the same time period. A 68 bp nucleotide fragment corresponding to S. aurata NPY mRNA was isolated by RT-PCR using primers designed from conserved regions for NPY in other vertebrates, and total RNA isolated from brain of S. aurata. Oligonucleotides designed from the 68 bp sequence of S. aurata NPY were used for subsequent quantitative real-time RT-PCR assays performed on RNA isolated from brain samples of the experimental fish. Starvation increased NPY mRNA levels in brain samples compared to fed fish. Among fed fish, those supplied with HLL diet exhibited the lowest NPY expression levels. Our findings suggest that starvation and low efficient diets promote an increase in NPY expression in the brain of S. aurata.