[Leptin]

Leptin (ob-protein), a previously unknown protein signal, is secreted from adipose tissue, circulates in the blood, probably bound to a family of binding proteins, and acts on central neural networks, that regulate weight and energy homeostasis. Leptin provides a communication link between fat tissue and the brain. Ob protein appears to play a major role in the control of body fat stores through coordinated regulation of feeding behavior, metabolism, autonomic nervous system and body energy balance in rodents, primates and humans. Leptin levels have pulsative and diurnal character. In lean subjects with relatively low adipose tissue, the majority of circulating leptin is in the bound form. On other hand, in obese individuals the majority of leptin circulates in free form presumably bioactive protein, and thus obese subjects are resistant to free leptin. Leptin's resistance is often coupled with insuline resistance postreceptor type. Leptin receptor is product of db genes. Ob-protein receptor belongs to the cytokine superfamily of receptors and has several variants. Leptin-receptor gene is expressed in abundant degree in ovary, uterus, testes, less in hypothalamus, hypophysis, and little in kidney. Leptin stimulates the reproductive endocrine system and may serve as a permissive signal to the reproductive system of normal animals. Ob-gene product, leptin is regulated by feedings patterns and hormones, such as insulin and glucocorticoids. There is assumed that neuropeptide Y (NPY) and melanocyte-stimulating hormone (MSH) and its receptor (MCR) are a critical components of the biological response to leptin levels. MCR in contrast to leptin receptors are coupled with G-transduction system.