The Endocrine Function of Adipose Tissue

White adipose tissue secretes adipokines that regulate numerous biological processes by autocrine, paracrine, and endocrine mechanisms. Adipokines are essential in the balance between appetite and satiety, regulation of body fat stores and energy expenditure, glucose tolerance, insulin release and sensitivity, cell growth, inflammation, oxidative stress, angiogenesis, and atherosclerosis. Cytokines are secreted directly from adipocytes, but also from other stromal cells in the adipose depot and primarily play a role in immune regulation. Among adipokines, leptin, resistin, and visfatin were described as markers that are positively related to body weight, fat mass, insulin resistance, and exhibit pro-inflammatory properties. Opposite to the proinflammatory cytokines, adipose tissue can secrete a series of anti-inflammatory adipokines, including adiponectin, apelin, vaspin, and omentin, which play crucial protective roles in inflammation states, insulin resistance, and atherosclerosis. In obese person dysregulation of adipokines secretion, in addition to upregulated inflammatory response, contributes to obesity-induced insulin resistance and systemic low-grade inflammation. Brown adipose tissue (BAT) might also have a secretory role, secreting “brownkines” that act in a paracrine or autocrine manner. Most of these factors promote hypertrophy and hyperplasia of BAT, vascularization, innervation and blood flow, processes that are all associated with BAT recruitment when thermogenic activity is enhanced.

Keywords: Adiponectin, Apelin, Adipsin, Brown adipose tissue, Inflammation, Leptin, Omentin, Resistin, Visfatin, Vaspin, White adipose tissue.