Effects of growth hormone and pair-feeding on leptin mRNA expression in liver and adipose tissue

Previous research has reported that elevations in circulating growth hormon e (GH) levels in meat-type chickens depresses feed intake (FI) more than 30 %. It is known that the product of the obese gene, leptin, functions to reg ulate Fl and energy expenditure. To investigate the effect of GH on leptin gene expression, broiler chickens were infused with recombinant chicken GH. To separate any secondary effects of a GH-induced reduction in FI on lepti n expression, groups of birds were pair-fed to an average level of voluntar y intake similar to GH-treated birds, but received no GH treatment. GH trea tment induced a dose-dependent increase in liver leptin gene expression, as measured by reverse transcriptase-polymerase chain reaction, whereas lepti n expression in adipose tissue was unchanged. Conversely, in chickens pair- fed (feed-restricted) there was a decrease in leptin gene expression in bot h tissues. These results provide evidence of a direct effect of GH on lepti n gene expression, which is independent of any effects on intake attributab le to GH-treatment, and suggest differential regulation of leptin expressio n between adipose tissue and liver. The results of these experiments provid e the first evidence of a relationship between GH and leptin in domestic bi rds. (C) 1999 Elsevier Science Inc. All rights reserved.