Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1998
Publication Date: N/A
Technical Abstract: Leptin, the polypeptide hormone encoded by the obese gene, is secreted by adipose tissue and has been shown to induce satiety and increase energy expenditure in mammals. In this study we have confirmed the presence of a leptin homolog in broiler chickens by amplification of both genomic DNA and MRNA isolated from liver and adipose tissues. The presence of leptin mRNA in the liver correlates with its function as the primary site of lipogenesis in birds. We have also investigated the effects of treatment with either insulin or dexamethasone on leptin expression, which has been previously shown to induce leptin production by mammalian adipocytes of total RNA isolated from tissue. Broiler chickens, 12 weeks of age, were treated with either porcine insulin or dexamethasone by daily IM injection. After 4 days of treatment the birds were sacrificed and total RNA isolated from liver and adipose tissues. Comparison of the RT-PCR products from treated birds to that of non-injected controls indicated a substantial induction of leptin mRNA production by insulin (3.1-fold) and dexamethasone (2.3-fold) in the liver. There appears to be no similar induction of leptin expression in chicken adipose tissue by either hormone. Similar experiments in mammals have shown induction of leptin in adipose tissue from 2 to 3-fold. The localization of leptin expression and tissue specific effects of insulin and dexamethasone treatment on leptin expression observed in chickens is likely due to the differing physiology of mammalian and avian lipid metabolism. Similar mechanisms demonstrated in mammals of appetite and energy expenditure regulation by leptin may exist in birds and be of significant economic importance to the poultry industry.