The general aim of the project is to study the cellular and molecular regulation of human adipose tissue HSL in physiology and pathology (obesity, metabolic syndrome), in relationship with the "in vivo" control of lipolysis. This will be achieved using "in vivo" and "in vitro" approaches. In the first part, lipolysis (in the basal state and its response to insulin catecholamines) and therefore HSL activity will be studied by microdialysis of abdominal and gluteal sub-cutaneous adipose tissue. For "in vitro" studies, isolated adipocytes will be obtained from biopsies of sub-cutaneous human adipose tissue from patients and control subjects. HSL response to insulin and A or B adrenergic agents will be measured and the expression of HSL will be determined. Moreover, we shall analyze sequences coding for HSL structure and study the regulation of its expression, looking for point mutations which could explain the effects in HSL function.