Endocrine Abstracts

The discovery of leptin in 1994 has opened a new era in the study of energy balance control at the molecular level. By informing the brain and other tissues the state of fat stores, leptin plays a key role in the control circuits of both appetite and energy expenditure, thus affecting most if not all of the body’s activities. This discovery in mammals stimulated a great interest in the physiological role and molecular mechanism of leptin in chickens. However, a true chicken leptin ortholog could not be found despite of our finding of the chicken leptin receptor (cLepR). In addition to the inability to detect leptin-like sequences in genomic, transcriptomic and proteomic analyses, also circulating leptin activity could not be detected in chickens, using a bioassay which is based on the cLepR. Moreover, injection of a highly potent leptin receptor antagonist had no effect in chickens. All these observations have now gained a further support by our new finding of a true leptin ortholog in recently deposited genomic sequences of doves (Columba livia) and several other birds. Further study in doves demonstrated expression of leptin mRNA primarily in liver and gonads and also indicated leptin bioactivity in the dove circulation. Therefore, these findings provides a new opportunity for the study of energy balance control by comparing birds that have lost or retained the leptin gene and for understanding the control of energy homeostasis, at an evolutionary perspective.