Under the Surface of Subcutaneous Adipose Tissue Biology

The global obesity epidemic enhanced contemporary interest in adipose tissue biology. Two structurally and functionally distinct depots, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT), are spread throughout the body. Their distribution was recognized to be a major determinant of metabolic risk. Unlike VAT, SAT showed some protective endocrine and inflammatory features that might explain the occurrence of obese but metabolically healthy persons. The unique developmental gene expression signature, angiogenesis, and adipogenic potential of SAT determines its growth ability under the positive energy balance. The overflow hypothesis suggested that when SAT is unable to expand sufficiently, fat overflows towards metabolically adverse ectopic depots. Besides white adipose tissue, recent studies found important brown adipose tissue activity responsible for thermogenesis and energy dissipation in adults as well. SAT is prone to "browning" - the appearance of particular beige adipocytes that contribute to its favorable metabolic effects. Morbid obesity, aging, hormonal status, nutrition, low physical activity, and other environmental factors impair SAT relative resistance to dysfunctional changes and promote development of metabolic disorders. The popular approach considering SAT mainly as the subject of cosmetic procedures for improving the appearance of body contours should be avoided. Complex heterogeneity of obesity revealed that a tissue of an extreme plasticity and rich interactions with vital functions of the body lies under the surface. Therapeutic manipulations to preserve and enhance healthier fat in order to correct obesity-related metabolic disorders seem to be a relevant but still unexplored opportunity.