Overexpression of the Renin-Angiotensin System in Human Visceral Adipose Tissue in Normal and Overweight Subjects

To evaluate the expression of the renin-angiotensin system (RAS) genes in visceral (VAT) and subcutaneous adipose tissue (SAT) in normotensive subjects with different body mass index (BMI). Adipose tissue was obtained from 22 normotensive (12 normal weight and 10 overweight) patients during surgery for colecystectomy. Angiotensinogen (AGT), angiotensin II receptor type 1 (AT1), angiotensin converting enzyme (ACE) mRNA, and protein levels were measured by reverse transcriptase-polymerase chain reaction and Western blot analysis, respectively. The AGT mRNA and AT1 receptor mRNA levels were significantly higher in VAT than in SAT; AGT mRNA levels were higher, although not significantly, in overweight subjects in both SAT and VAT. There was no significant difference in ACE gene expression in the two tissues, and no expression of angiotensin II receptor type 2 (AT2). Finally, we failed to find mRNA for the renin gene in adipose tissue. The presence of AGT and ATI receptor in SAT and VAT was confirmed by Western blot analysis. Our study demonstrates the presence--and different levels of expression--of the various components of the RAS system (AGT, ATI, and ACE) in human SAT and VAT, and highlights the different role and regulation of the system in the two tissues. Its high expression in VAT suggests that its regulation and function are involved in all conditions where visceral adiposity is present.