[Adipose tissue: an innervated endocrine gland].

Until recently, adipose tissue was considered to function as a passive store of triglycerides and therefore of calories. Fascinating research over the past ten years has altered this traditional perspective. Adipose tissue has been shown to produce hormones. Leptin was discovered in 1994; one of its main functions is to adapt the organism to starvation. Sympathetic nerve fibres were shown to innervate adipose tissue and to facilitate lipolysis leading to the release of glycerol and free fatty acids. In addition, parasympathetic innervation of adipose tissue was recently demonstrated, with anabolic effects. Different sets of autonomic neurons in the brain stem appear to innervate either the abdominal or the subcutaneous fat compartment. This may be the anatomical substrate for the hitherto unexplained regulation of body fat distribution (subcutaneous versus intra-abdominal). Moreover, fat distribution under physiological conditions (sex steroids, glucocorticoids) and pathological conditions (e.g., AIDS lipodystrophy, Cushing syndrome) might be mediated via the central nervous system. The developments in this research area have the potential to increase our insights into the pathogenesis of metabolic disorders such as hypertriglyceridaemia and type-2 diabetes mellitus.