We compared the gene expression of inflammatory and other proteins by real-time quantitative
polymerase chain reaction in epicardial, substernal (mediastinal) and subcutaneous
sternal, upper abdominal, and leg fat from coronary bypass patients and omental (visceral)
fat from extremely obese women undergoing bariatric surgery. We hypothesized that
(1) epicardial fat would exhibit higher expression of inflammatory messenger RNAs
(mRNAs) than substernal and subcutaneous fat and (2) epicardial mRNAs would be similar
to those in omental fat. Epicardial fat was clearly different from substernal fat
because there was a far higher expression of haptoglobin, prostaglandin D(2) synthase,
nerve growth factor beta, the soluble vascular endothelial growth factor receptor
(FLT1), and alpha1 glycoprotein but not of inflammatory adipokines such as monocyte
chemoattractant protein-1, interleukin (IL)-8, IL-1beta, tumor necrosis factor alpha,
serum amyloid A, plasminogen activator inhibitor-1, or adiponectin despite underlying
coronary atherosclerosis. However, the latter inflammatory adipokines as well as most
other mRNAs were overexpressed in epicardial fat as compared with the subcutaneous
depots except for IL-8, fatty acid binding protein 4, the angiotensin II receptor
1, IL-6, and superoxide dismutase-2. Relative to omental fat, about one third of the
genes were expressed at the same levels, whereas monocyte chemoattractant protein-1,
cyclooxygenase-2, plasminogen activator inhibitor-1, IL-1beta, and IL-6 were expressed
at far lower levels in epicardial fat. In conclusion, epicardial fat does not appear
to be a potentially more important source of inflammatory adipokines than substernal
mediastinal fat. Furthermore, the expression of inflammatory cytokines such as IL-6
and IL-1beta is actually higher in omental fat from obese women without coronary atherosclerosis.
The data do not support the hypothesis that most of the inflammatory adipokines are
expressed at high levels in epicardial fat of humans.
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