Molecular characterization of melanin-concentrating hormone (MCH) in Schizothorax prenanti: cloning, tissue distribution and role in food intake regulation.

Melanin-concentrating hormone (MCH) is a crucial neuropeptide involved in various biological functions in both mammals and fish. In this study, the full-length MCH cDNA was obtained from Schizothorax prenanti by rapid amplification of cDNA ends polymerase chain reaction. The full-length MCH cDNA contained 589 nucleotides including an open reading frame of 375 nucleotides encoding 256 amino acids. MCH mRNA was highly expressed in the brain by real-time quantitative PCR analysis. Within the brain, expression of MCH mRNA was preponderantly detected in the hypothalamus. In addition, the MCH mRNA expression in the S. prenanti hypothalamus of fed group was significantly decreased compared with the fasted group at 1 and 3 h post-feeding, respectively. Furthermore, the MCH gene expression presented significant increase in the hypothalamus of fasted group compared with the fed group during long-term fasting. After re-feeding, there was a dramatic decrease in MCH mRNA expression in the hypothalamus of S. prenanti. The results indicate that the expression of MCH is affected by feeding status. Taken together, our results suggest that MCH may be involved in food intake regulation in S. prenanti.

Molecular and physiological evidences for the role in appetite regulation of apelin and its receptor APJ in Ya-fish (Schizothorax prenanti).

Apelin is a recently discovered peptide produced by several tissues with diverse physiological actions mediated by its receptor APJ. In order to better understand the role of apelin in the regulation of appetite in fish, we cloned the cDNAs encoding apelin and APJ, and investigated their mRNA distributions in Ya-fish (Schizothorax prenanti) tissues. We also assessed the effects of different nutritional status on apelin and APJ mRNAs abundance. Apelin and APJ mRNAs were ubiquitously expressed in all tissues tested, relatively high expression levels were detected in the heart, spleen, hypothalamus and kidney. Short-term fasting significant increased APJ mRNA expression, but no significant difference between fasted fish and fed control on 5- and 7-day. Meanwhile, apelin mRNA expression consistently increased during the 7-day food deprivation. In order to further characterize apelin in fish, we performed intraperitoneal (i.p.) injection of apelin-13 and examined food intake of the injected fish. Apelin injected at a dose of 100 ng/g body weight induced a significant increase in food intake compared to saline injected fish. Our results suggest that apelin acts as an orexigenic factor in Ya-fish. Their widespread distributions also suggest that apelin and APJ might play multiple physiological regulating roles in fish.

Molecular characterization and tissue expression of peptide YY in Schizothorax prenanti: effects of periprandial changes and fasting on expression in the hypothalamus.

Peptide YY (PYY) is a potent anorectic neuropeptide implicated in feeding regulation in mammals. However, the involvement of PYY in the feeding behavior of teleosts has not been well understood. In this study, we employed molecular, real-time quantitative PCR and physiological studies to characterize the structure, distribution, and appetite regulatory effects of PYY in Schizothorax prenanti (S. prenanti). A very high conservation in PYY sequences was found in teleosts. PYY is widely expressed, with the highest levels of expression in telencephalon, medulla oblongata, pituitary and hypothalamus of S. prenanti. The PYY mRNA expression in the hypothalamus was highly elevated after a meal, suggesting a satiety signal role for PYY in S. prenanti. In addition, PYY gene expression in the hypothalamus was decreased after fasting and increased sharply after refeeding, which suggested that PYY might be involved in the central regulation of appetite in S. prenanti. Overall, our result provides basis for further investigation into the regulation of feeding in S. prenanti.

Molecular characterization, tissue distribution and feeding related changes of NUCB2A/nesfatin-1 in Ya-fish (Schizothorax prenanti).

The protein nucleobindin-2 (NUCB2) was identified over a decade ago and recently raised great interest as its derived peptide nesfatin-1 was shown to reduce food intake and body weight in rodents. However, the involvement of NUCB2 in feeding behavior has not well been studied in fish. In the present study, we characterized the structure, distribution, and meal responsive of NUCB2A/nesfatin-1 in Ya-fish (Schizothorax prenanti) for the first time. The full length cDNA of Ya-fish was 2140base pair (bp), which encoded a polypeptide of 487 amino acid residues including a 23 amino acid signal peptide. A high conservation in NUCB2 sequences was found in vertebrates, however the proposed propeptide cleavage site (Arg-Arg) conserved among other species is not present in Ya-fish NUCB2A sequence. Tissue distribution analysis revealed that Ya-fish NUCB2A mRNA was ubiquitously expressed in all test tissues, and abundant expression was detected in several regions including the hypothalamus, hepatopancreas, ovary and intestines. NUCB2A mRNA expression respond to feeding status change may vary and be tissue specific. NUCB2A mRNA levels significantly increased (P<0.05) in the hypothalamus and intestines after feeding and substantially decreased (P<0.01) during a week food deprivation in the hypothalamus. Meanwhile, NUCB2A mRNA in the hepatopancreas was significantly elevated (P<0.001) during food deprivation, and a similar increase was also found after short-time fasting. This points toward a potential hepatopancreas specific local role for NUCB2A in the regulation of metabolism during food deprivation. Collectively, these results provide the molecular and functional evidence to support potential anorectic and metabolic roles for NUCB2A in Ya-fish.