Effects of leptin administration on the endocrine pancreas and liver in the lizard Podarcis sicula

In this study, we investigated the presence of leptin receptor in pancreatic islets and the effect of exogenous leptin administration in Podarcis sicula on glucose metabolism. Our data show the presence of leptin receptor immunoreactivity in the endocrine pancreas suggesting that leptin may act at a peripheral level as previously postulated in mammals. The effects of short- and long-term and dose–response treatment with supraphysiological concentrations of leptin on circulating levels of insulin, glucagon and glucose in the blood have been evaluated. Taken together, our results indicate that leptin treatment was followed by an increase in insulin, glucagon and glucose in the blood, depending on the dose of leptin. Moreover, leptin treatment brought about a decrease of glycogen and the appearance of tyrosine-phosphorylated proteins in the liver. This study shows that in the lizard P. sicula leptin is involved in glucose metabolism. J. Exp. Zool. 305A, 2006. © 2006 Wiley-Liss, Inc.