Leptin in lizards: a new metabolic factor?

Leptin is a recently discovered protein implicated in the regulation of food intake, energy expenditure, and whole-body energy balance in rodents and humans. Leptin is indeed characterized by a vast array of functions. Recently, the increasing amount of global research on leptin has shown an unexpected and copious variety of leptin functions, extending from metabolism to reproduction, hematopoiesis, inflammation, and immunological response. The numerous effects of leptin on tissues and endocrine systems have ultimately led to the coordination of whole-body energy metabolism and promoted the expansion of studies on leptin presence and effects in different animal groups, other than humans and rodents. Although studies carried out so far have almost exclusively utilized lizards as animal models, our knowledge in reptiles is still very limited. Such studies provide good evidence for the presence of leptin in target organs such as fat bodies, liver, pancreas, thyroid, stomach, brain, blood, contributing to the definition of a general picture which recalls that of birds and mammals but is also peculiar of these vertebrates. In this review, we summarized the current literature on leptin in lizards and compared it with the recent findings for birds and mammal