Vasilatos-Younken, Regina - PENNSYLVANIA STATE UNIV
Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 2, 1999
Publication Date: N/A
Interpretive Summary: The regulation of food intake in poultry is poorly understood. Among the problems associated with changes in feed intake in birds are obesity in broiler breeders, and conversely, anorexia in turkey poults. Previous studies in chickens have shown that growth hormone depresses food intake. Recently, a hormone termed leptin, produced by the liver and adipose tissue has been shown to regulate food intake and energy expenditure. This study was conducted to define the effect of growth hormone on leptin gene expression. In addition, the effect of pair-feeding on leptin was assessed in chicks. It was determined that growth hormone increased leptin gene expression while pair feeding decreased gene expression. The results of this study demonstrate that growth hormone is an important regulator of leptin secretion.
Previous research has reported that elevations in circulating growth hormone (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 regulate FI and energy expenditure. To investigate the effect of GH on leptin gene expression, broiler chickens were infused with recombinant cGH. To separate any secondary effects of a GH-induced reduction in FI on leptin expression, groups of birds were pair-fed to an average level of voluntary intake similar to GH-treated birds, but received no GH-treatment. GH treatment induced a dose-dependent increased in liver leptin gene expression, as measured by RT-PCR, whereas leptin expression in adipose tissue was unchanged. Conversely, in chickens pair-fed (feed-restricted) there was a decrease in leptin gene expression in both tissues. These results provide evidence of a direct effect of GH on leptin gene expression, which is independent of any effects on intake due to GH-treatment and suggest differential regulation of leptin expression between adipose and liver tissues. The results of these experiments provide the first evidence of a relationship between GH and leptin in domestic birds.