Gene structure, recombinant expression and functional characterization of grass carp leptin.
Leptin is an important hormone for the regulation of food intake, energy expenditure and reproduction in mammals, but information regarding its role in teleosts remains scant. In the present study, the gene structures of grass carp (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) leptins were characterized. Recombinant grass carp leptin (rgc-LEP) was expressed in Escherichia coli and purified, and identified by mass spectrometric analysis. A strong anorexic effect on food intake was observed in grass carp on the first day after intraperitoneal (IP) injection of rgc-LEP, but not during the following days. Body weight of the leptin group (LEP group) and the pair-fed group (PF group) showed no difference throughout the experimental period. The acute and chronic effects on the expression of key genes correlating to food intake, energy expenditure, lipid metabolism and digestion were further characterized by real-time PCR. Accordingly, the mRNA levels of neuropeptide Y (NPY), Stearoyl-CoA desaturase 1 (SCD1) and lipoprotein lipase (LPL) were significantly reduced whereas the mRNA levels of uncoupling protein 2 (UCP2), bile salt-activated lipase (BSAL) and fatty acid elongase (ELO) were significantly elevated on the first day after injection. No effect on the expression of these genes (except LPL) was observed on day 13. In contrast to the down-regulation by exogenous leptin in mammals, the mRNA level of grass carp leptin was elevated 5.76-fold on the first day after rgc-LEP treatment. Our results suggest that leptin has an acute effect on the regulation of food intake, energy expenditure and lipid metabolism in grass carp, but the effect can be rapidly counteracted through mechanisms that are currently unknown.
College of Life Science and Technology, Jinan University, Guangzhou 510632, China.
Guan-Gui
GG
Li
Xu-Fang
XF
Liang
Qiuling
Q
Xie
Guangzhao
G
Li
Ying
Y
Yu
Kaaseng
K
Lai
D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002347:Carps; D004435:Eating / Q000187:drug effects / Q000235:genetics; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D000081031:Fatty Acid Elongases; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D007473:Ion Channels / Q000235:genetics; D020738:Leptin / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D050356:Lipid Metabolism / Q000187:drug effects / Q000235:genetics; D008071:Lipoprotein Lipase / Q000235:genetics; D024101:Mitochondrial Proteins / Q000235:genetics; D009478:Neuropeptide Y / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013230:Stearoyl-CoA Desaturase / Q000235:genetics; D002787:Sterol Esterase / Q000235:genetics; D000071246:Uncoupling Protein 2
D029941:Fish Proteins; D007473:Ion Channels; D020738:Leptin; D024101:Mitochondrial Proteins; D009478:Neuropeptide Y; D011994:Recombinant Proteins; D000071246:Uncoupling Protein 2; D013230:Stearoyl-CoA Desaturase; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases; C054784:bile salt-stimulated lipase; D002787:Sterol Esterase; D008071:Lipoprotein Lipase