Relationship between epicardial adipose tissue adipocyte size and MCP-1 expression

Adipocyte size has been associated to increase in inflammatory cytokines expression that can be related to the cardiovascular risk of obesity. Epicardial adipose tissue (EAT) was discovered to play a key role in cardiovascular diseases by producing several inflammatory adipokines. We sought to study whether EAT and subcutaneous adipose tissue (SAT) mean adipocyte sizes are related to the expression of adipokines in patients with cardiovascular diseases. We collected EAT, SAT and blood samples from 22 patients aged 70.9 (s.d. 10.3) undergoing heart surgery. Monocyte chemoattractant protein (MCP)-1, interleukin (IL)-10 and tumor necrosis factor (TNF)-alpha were analyzed by real time RT-PCR, ELISA or immunohistochemistry. Hematoxylin-eosin staining was used for adipocyte area calculations. Adipocyte size is negatively correlated to MCP-1 expression (r=-0.475; p=0.034) in EAT and positively correlated in SAT (r=0.438; p=0.047). These trends persisted after stratification for sex and coronary artery disease (CAD), but only the relationship between EAT MCP-1 and adipocyte size reached statistical significance in the larger group of men with CAD. We have observed that SAT adipocyte size is correlated to BMI (r=0.601; p=0.003); whereas only a non-statistically significant trend was observed in EAT. IL-10 and TNF-alpha expression were not associated to adipocyte size in EAT nor SAT. Secondarily, we found that EAT IL-10 expression is higher in patients with CAD. These results suggest that adipocyte size is a negative determinant of MCP-1 expression in EAT and a positive determinant in SAT. These data might partly explain the different implications of EAT and SAT in cardiovascular diseases.