Subcutaneous and visceral adipose tissue: structural and functional differences.

Obesity is a heterogeneous disorder. Obese individuals vary in their body fat distribution, their metabolic profile and degree of associated cardiovascular and metabolic risk. Abdominal obesity carries greater risk of developing diabetes and future cardiovascular events than peripheral or gluteofemoral obesity. There are differences between adipose tissue present in subcutaneous areas (SCAT) and visceral adipose tissue (VAT) present in the abdominal cavity. These include anatomical, cellular, molecular, physiological, clinical and prognostic differences. Anatomically, VAT is present mainly in the mesentery and omentum, and drains directly through the portal circulaion to the liver. VAT compared with SCAT is more cellular, vascular, innervated and contains a larger number of inflammatory and immune cells, lesser preadipocyte differentiating capacity and a greater percentage of large adipocytes. There are more glucocorticoid and androgen receptors in VAT than in SCAT. VAT adipocytes are more metabolically active, more sensitive to lipolysis and more insulin-resistant than SCAT adipocytes. VAT has a greater capacity to generate free fatty acids and to uptake glucose than SCAT and is more sensitive to adrenergic stimulation, while SCAT is more avid in absorption of circulating free fatty acids and triglycerides. VAT carries a greater prediction of mortality than SCAT.