Figure 1.

White adipose tissue regulates whole-body metabolism. The adipocyte is not only a storage depot but has many other functions including 1) as an endocrine gland, secreting many hormones, cytokines, and vasoactive substances; 2) having a role in energy balance, by secreting hormones such as leptin and also by browning and beiging and the futile cycles that burn energy; and 3) as a metabolic tissue that performs lipogenesis, lipolysis, and metabolism of branched-chain amino acids and other molecules. Adipose inflammation, characterized by immune cell infiltration and cytokine secretion, occurs in the setting of obesity and insulin resistance. All of these processes contribute to regulation of insulin sensitivity, insulin secretion, food intake and energy expenditure, and ultimately body weight. PAI, plasminogen activator inhibitor.