Leptin

Leptin is a multifunctional adipocyte-derived hormone that plays a central role in energy homeostasis, appetite, food intake, energy expenditure, and body weight regulation through leptin receptor-mediated signaling in the brain and peripheral tissues. Its actions involve several signaling pathways, including JAK/STAT, PI3K, MAPK, and AMPK. Beyond energy regulation, leptin contributes to brain and neuroendocrine functions, glucose and lipid metabolism, insulin sensitivity, reproduction, immune regulation, and skeletal homeostasis. It influences bone remodeling, osteoblast and chondrocyte function, and cartilage metabolism, highlighting the close interaction between adipose tissue and other physiological systems. Dysregulated leptin signaling, particularly leptin resistance, is strongly associated with obesity and metabolic disturbances. Overall, knowledge of leptin physiology and its diverse biological functions provides an essential basis for examining the consequences of impaired leptin signaling in metabolic and other chronic disorders.