Hypotensive effects of omentin-1 related to increased adiponectin and decreased interleukin-6 in intra-thoracic pericardial adipose tissue

Background: Omentin is an adipokine expressed in visceral adipose tissue (VAT). In vitro studies demonstrated that omentin induces vasorelaxation in isolated rat mesenteric arteries, and in vivo studies showed inhibition of agonist-induced increases in blood pressure, possibly mediated by nitric oxide (NO)-dependent mechanisms. Methods: We investigated, in normotensive rats, the effects of subacute omentin-1 administration [8 mu g/kg, intraperitoneally (ip), once daily for 14 days] on cardiac activity, blood pressure, plasma concentration of L-citrulline (as a marker of NO production from L-arginine), and the gene expression of adiponectin, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in intra-thoracic pericardial adipose tissue (PAT). Electrocardiography (ECG), heart rate (HR), mean blood pressure (MBP), pulse pressure (PP) were monitored before and after treatment with omentin-1 or vehicle. Results: With respect to baseline and vehicle, we found a significant decrease of MBP (p < 0.005) and PP (p < 0.05) after treatment with omentin-1, while ECG and HR were not modified. Omentin-1 significantly increased L-citrulline levels in plasma (p < 0.05), and the gene expression of adiponectin in PAT (p < 0.05). On the other hand, we found decreased gene expression of IL-6 (p < 0.005), while TNF-alpha mRNA in PAT was not affected. Conclusion: We conclude that the hypotensive effects of omentin-1 could be driven by stimulated production of NO in the vascular system, possibly related to increased adiponectin and decreased IL-6 mRNA in PAT. (C) 2014 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. Z o.o. All rights reserved.