Identification of omentin mRNA in human epicardial adipose tissue: comparison to omentin in subcutaneous, internal mammary artery periadventitial and visceral abdominal depots

Objective: The purpose of this study was to determine the relative distribution of omentin and visfatin mRNA in human epicardial, peri-internal mammary, upper thoracic, upper abdominal and leg vein subcutaneous adipose tissue as well as the distribution of omentin in the nonfat cells and adipocytes of human omental adipose tissue. Background: Omentin is found in human omentum but not subcutaneous fat. Omentin and visfatin are considered markers of visceral abdominal fat. Research design and methods: The mRNA content of omentin and visfatin was measured by qRT-PCR analysis of fat samples removed from humans undergoing cardiac or bariatric surgery. Results: Omentin mRNA in internal mammary fat was 3.5%, that in the upper thoracic subcutaneous fat was 4.7% while that in the other subcutaneous fat depots was less than 1% of omentin in epicardial fat. The distribution of visfatin mRNA did not vary between the five depots. Omentin mRNA was preferentially expressed in the nonfat cells of omental adipose tissue since the omentin mRNA content of isolated adipocytes was 9% of that in nonfat cells, and similar results were seen for visfatin. The amount of omentin mRNA in differentiated adipocytes was 0.3% and that of visfatin 4% of that in nonfat cells. The amount of omentin mRNA in preadipocytes was virtually undetectable while that of visfatin was 3% of that in freshly isolated nonfat cells from omental adipose tissue. Conclusion: Omentin mRNA is predominantly found in epicardial and omental human fat whereas visfatin mRNA is found to the same extent in epicardial, subcutaneous and omental fat.