Identification of genuine/authentic avian leptin : some answers and more questions

Abstract

The dogmatic adherence to “what is good for the goose is good for the gander” appears to pervade avian endocrinology research when it comes to vertebrate evolution of hormones and their physiological roles in birds. There appears to be a general acceptance that specific hormones, their cognate receptors, and their regulatory functions identified in other vertebrates should be present and serve the same function in birds. This has been largely the case for leptin (LEP) originally identified in mammals (1– 5), which has been vigorously sought for more than a decade in birds (6 –10), and also more recently for kisspeptin (11, 12). But should we expect to find the same hormones and functions in birds as occurs in other vertebrates? In order for early reptilian bird ancestors to take to the air, phenomenal evolutionary changes in their physiology were required and presumably drove changes in the use of existing hormones and cognate receptors, their modification, or their abandonment. Yet many scientists take the view that major physiological systems present in tetrapods and fish should be present in birds and serve the same function and use of the same hormone/receptor regulators.