Meeting Abstract
92.7 Wednesday, Jan. 7 Cloning and regulation of hepatic leptin mRNA expression by nutritional status in hybrid striped bass (Genus Morone) WON, E.T.*; BALTZEGAR, D.A.; PICHA, M.E.; BORSKI, R.J.; North Carolina State University; North Carolina State University; North Carolina State University; North Carolina State University etwon@ncsu.edu
Leptin is an anorexigenic peptide hormone that regulates energy homeostasis. In mammals it is produced predominantly by white adipose tissue and circulates in proportion to energy reserves. Teleost leptin has been characterized in a few fish species, but its regulation is not well understood, particularly in response to nutritional status. We cloned a putative leptin in striped bass (Morone saxatilis). Striped bass and the commercially valuable hybrid striped bass (HSB, M. chrysops X M. saxatilis) leptin coding sequence showed only 65% homology with pufferfish, 52% with rainbow trout and 46% with mouse. PCR showed that leptin mRNA was exclusively expressed in the liver, and not adipose or other tissues. We then evaluated whether the metabolic status of HSB might alter leptin gene expression. Juvenile HSB (100 g) subjected to three weeks of food deprivation had significantly lower levels of hepatic leptin mRNA expression than fed controls, as measured by quantitative PCR. In a separate experiment HSB were initially subjected to 3 weeks feed deprivation followed by 3 weeks of refeeding. Fasting for 3 weeks again reduced leptin mRNA levels relative to fed controls. Leptin mRNA levels then increased upon refeeding, albeit levels were not completely restored to those seen in control fish fed throughout the study. This study represents the first characterization of leptin in a Perciforme, the largest Order of fish. We show that the liver predominantly produces leptin and that leptin gene expression changes with feeding state, decreasing under catabolic states. These results are consistent with a potential role for leptin as a regulator of energy reserves in teleosts.
