Ectopic Fat Depots and Cardiovascular Disease

Obesity is increasingly recognized as a heterogeneous condition with variable cardiovascular risk in the setting of similar levels of body mass index. Ectopic fat depots may contribute to obesity-mediated vascular disease and explain part of this risk differential. This review will explore the current understanding of the biology of ectopic adipose tissue storage, its quantification and classification, and existing research supporting an association between ectopic fat and cardiovascular disease.Obesity is associated with significant cardiovascular morbidity and mortality, and is recognized as a major public health concern.1,2 Although useful clinically and in epidemiologic studies, the classification of obesity using body mass index (BMI) does not fully encompass the complex biology of excess adiposity. Excess body fat is now recognized as a heterogeneous condition in which individuals with similar levels of BMI may have distinct metabolic and cardiovascular disease risk.2 Variation in body fat distribution provides 1 potential explanation for some of the risk differential that persists after accounting for BMI and standard risk factors.3 The study of ectopic adipose tissue depots, which surround organs and blood vessels, focuses on the quantification of these different fat depots and their potential systemic and local consequences.Waist circumference was one of the earliest means of quantifying body fat distribution, and some clinical guidelines have recommended measurement of waist circumference to provide additional information regarding cardiovascular risk.4 However, waist circumference consists of both subcutaneous adipose (SAT) (classically nonectopic) and visceral adipose tissue (VAT) (classically ectopic). This is important because VAT is associated with more adverse levels of metabolic risk factors compared with SAT.5 In addition, seminal work in mice has shown that transplantation of SAT, but not VAT, to an intra-abdominal site resulted in beneficial effects on metabolism.6 Taken together, these findings suggest that information about …