Leptin in Teleost Fishes: An Argument for Comparative Study

Copeland, Donald L.; Duff, R. Joel; Liu, Qin; Prokop, Jeremy W.; Londraville, Richard L.

doi:10.3389/fphys.2011.00026

Cited by 97 publications

(72 citation statements)

References 145 publications

(167 reference statements)

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“…Leptin has been shown to have pleiotropic effects in regulating appetite, fat metabolism, growth, reproduction, body temperature, bone remodeling, immune function, stress, inflammatory responsiveness, hematopoiesis and angiogenesis (Steppan et al 2000;Dagogo-Jack et al 2005;Swoap 2008;Friedman 2009;Lafrance et al 2010;Copeland et al 2011). Notably, because of the tremendous differences in gene sequence, studies of leptin in fish lag behind studies in mammals significantly (Copeland et al 2011). Our group has performed in-depth research on leptin in grass carp, including gene cloning and the role of leptin on food intake and fat metabolism (Li et al 2010;Lu et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Effects of glucose, insulin and triiodothyroxine on leptin and leptin receptor expression and the effects of leptin on activities of enzymes related to glucose metabolism in grass carp (Ctenopharyngodon idella) hepatocytes

Zhou

Yuan

et al. 2015

Fish Physiol Biochem

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Leptin is an important regulator of appetite and energy expenditure in mammals, but its role in fish metabolism control is poorly understood. Our previous studies demonstrated that leptin has an effect on the regulation of food intake and energy expenditure as well as lipid metabolism (stimulation of lipolysis and inhibition of adipogenesis) in the grass carp Ctenopharyngodon idella. To further investigate the role of leptin in fish, the effects of glucose, insulin and triiodothyroxine (T3) on the expression levels of leptin and leptin receptor (Lepr) and the effects of leptin on the activities of critical glucose metabolism enzymes in grass carp hepatocytes were evaluated in the present study. Our data indicated that leptin gene expression was induced by glucose in a dose-dependent manner, while Lepr gene expression exhibited a biphasic change. A high dose of insulin (100 ng/mL) significantly up-regulated the expression of leptin and Lepr. Leptin expression was markedly up-regulated by a low concentration of T3 but inhibited by a high concentration of T3. T3 up-regulated Lepr expression in a dose-dependent manner. Together, these data suggest that leptin had a close relationship with three factors (glucose, insulin and T3) and might participate in the regulation of glucose metabolism in grass carp. In addition, we also found that leptin affected the activities of key enzymes that are involved in glucose metabolism, which might be mediated by insulin receptor substrate-phosphoinositol 3-kinase signaling.

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Section: Discussionmentioning

confidence: 99%

Effects of glucose, insulin and triiodothyroxine on leptin and leptin receptor expression and the effects of leptin on activities of enzymes related to glucose metabolism in grass carp (Ctenopharyngodon idella) hepatocytes

Zhou

Yuan

et al. 2015

Fish Physiol Biochem

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“…However, there is no clear evidence that this hormone induces lipolysis in fishes (Li et al 2010, Copeland et al 2011). We found little or no effects on lipid catabolism in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Newly developed recombinant tilapia leptin A (rtLepA) has been evaluated along with commercially prepared human leptin (recombinant human leptin (rhLep)) to assess potential differences in metabolic effect. Despite considerable divergence in peptide sequence (w13% identity), the tertiary structures of human and fish leptins appear quite similar (Huising et al 2006, Copeland et al 2011, and mammalian forms have been commonly used to evaluate the function of leptin in teleost fishes (de Pedro et al 2006, Won et al 2012see Won & Borski (2013) for review). This study directly contrasts the effects of recombinant tilapia and human leptins, where many but not all responses appear to be conserved.…”

Section: Introductionmentioning

confidence: 99%

Role for leptin in promoting glucose mobilization during acute hyperosmotic stress in teleost fishes

Baltzegar

Reading

Douros

et al. 2013

Journal of Endocrinology

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Osmoregulation is critical for survival in all vertebrates, yet the endocrine regulation of this metabolically expensive process is not fully understood. Specifically, the function of leptin in the regulation of energy expenditure in fishes, and among ectotherms, in general, remains unresolved. In this study, we examined the effects of acute salinity transfer (72 h) and the effects of leptin and cortisol on plasma metabolites and hepatic energy reserves in the euryhaline fish, the tilapia (Oreochromis mossambicus). Transfer to 2/3 seawater (23 ppt) significantly increased plasma glucose, amino acid, and lactate levels relative to those in the control fish. Plasma glucose levels were positively correlated with amino acid levels (R 2 Z0.614), but not with lactate levels. The mRNA expression of liver leptin A (lepa), leptin receptor (lepr), and hormone-sensitive and lipoprotein lipases (hsl and lpl) as well as triglyceride content increased during salinity transfer, but plasma free fatty acid and triglyceride levels remained unchanged. Both leptin and cortisol significantly increased plasma glucose levels in vivo, but only leptin decreased liver glycogen levels. Leptin decreased the expression of liver hsl and lpl mRNAs, whereas cortisol significantly increased the expression of these lipases. These findings suggest that hepatic glucose mobilization into the blood following an acute salinity challenge involves both glycogenolysis, induced by leptin, and subsequent gluconeogenesis of free amino acids. This is the first study to report that teleost leptin A has actions that are functionally distinct from those described in mammals acting as a potent hyperglycemic factor during osmotic stress, possibly in synergism with cortisol. These results suggest that the function of leptin may have diverged during the evolution of vertebrates, possibly reflecting differences in metabolic regulation between poikilotherms and homeotherms.

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“…47 We strongly adhere to a comparative approach because of the 48 diverse and versatile models provided by ectotherms, including 49 teleosts, as they are less stringent in their metabolic homeostasis 50 (Copeland et al, 2011;Denver et al, 2011;Londraville et al, 2014). 51 Moreover, by studying teleostean fishes, the first true vertebrates on earth, one could gain insight in more 'original' functions of leptin, 53 and indeed in recent years a rather different leptin physiology has 54 emerged in teleostean fishes compared to mammals.…”

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confidence: 98%