Leptin expression in mandarin fish Siniperca chuatsi (Basilewsky): Regulation by postprandial and short-term fasting treatment.

Most fish species possess duplicate leptin genes (LEP). Mandarin fish (Siniperca chuatsi) leptin A gene (sLEP-A) have been cloned in the previous study. In the present study, we cloned and characterized leptin B gene (sLEP-B) in mandarin fish, including a 471bp open reading frame (ORF) encoding a 158-amino acid protein. The three-dimensional (3D) structural model of sLEP-B protein showed a highly conserved of tertiary structure similar to that of other vertebrates. Genomic sequencing results indicated that sLEP-B possessed only one intron. This is the first report of the loss of an intron in LEP-B in Perciformes. The different distribution patterns of sLEPs suggest different physiological roles of these two genes. The presence of HNF3β, a liver-enriched transcription factor, only in sLEP-A indicated abundant expression and metabolic function of sLEP-A in the liver. In an in vivo experiment, the expressions of brain sLEP-A and sLEP-B were observed to increase after a meal. During the short-term fasting, the expressions of sLEPs in mandarin fish brain were decreased significantly. A persistent and significant increase in hepatic sLEP-A expression supported a relationship between leptin and food intake in mandarin fish. These results suggest that sLEP-A plays an important role in the regulation of energy homeostasis in this carnivorous fish, and sLEP-B is probably a specialized gene responsible for the central nervous system (CNS) control of energy regulation.