Adipose Tissue Endothelium

Adipose tissue can be found throughout the body but is primarily distributed in several subcutaneous and visceral locations or “depots” (1). The general distribution pattern and location of adipose tissue depots and the proportion of total body fat that each depot represents varies widely between species. In humans and swine the subcutaneous depot represents a much larger proportion of total adipose tissue than in rodents. In fact, several distinct layers of subcutaneous adipose tissue are present in humans and swine. Excessive adipose tissue accumulation in humans is often associated with the adverse health consequences of the metabolic syndrome (2). An adipose tissue distribution pattern favoring visceral adipose tissue often is implicated in this syndrome. Adipose tissue can be considered a metabolic buffer by sequestering fatty acids after a meal and releasing them when needed at a later time (3). Adipose tissue blood flow (ATBF) and its regulation is an essential component of the metabolic function of adipose tissue (3). The fact that increased ATBF leads to increased clearance of triglycerides by the tissue illustrates the physiological impact of ATBF (3). Our understanding of the role of adipose tissue as an endocrine organ has evolved rapidly since the discovery of leptin (2). Adipose tissue is an active organ that produces and secretes a variety of factors into the circulation, including leptin and several interleukins (2), which also illustrates the physiological impact of ATBF. In contrast to ATBF, very little is known or published on adipose tissue endothelium per se. Furthermore, the widespread distribution of adipose tissue and the many location- or depot-dependent characteristics (including blood flow) (4) precludes extrapolation of results from one depot to the next.