The gene for leptin (LEP) is mapped to the human chromosome 7q32.1. The encoded protein is a non-glycosylated polypeptide, primarily produced and secreted by the mature adipocytes. Leptin is expressed in white adipose tissue, fetal tissues, skeletal muscle, chondrocytes, gastric chief cells, the placenta, ovary, and many immune cells. It is absent or expressed at extremely low levels in other adult tissues. Human leptin is 85% identical to mouse leptin and 84% identical to rat leptin, while mouse and rat exhibit 96% identity in their leptin molecules.
Leptin is a hormone secreted by adipocytes and regulates energy homeostasis, inflammation and neuroendocrine processes, synaptic formation and memory condensation. The physiological effects of leptin are mediated by leptin receptors, ObR and LepR. Leptin is the key regulator of obesity and acts directly on neuronal networks to regulate feeding, metabolism and gastric mobility. The pathways that mediate the effect of leptin are Janus kinase (JAK)/signal transducer and activator of transcription (STAT), phosphoinositide 3-kinase (PI3K) and c-Jun N-terminal kinase (JNK).
