Functional effects of visfatin in isolated rat mesenteric small resistance arteries.

A new adipocytokine, visfatin is expressed in perivascular adipose tissue (PVAT) and exerts effects on vascular system in addition to its relationship with various pathological conditions. The present study aimed to investigate the functional effects of visfatin and the possible underlying mechanism(s) of the effects of visfatin in isolated rat mesenteric small resistance arteries. The study was conducted in small resistance arterial rings isolated from rat mesenteric vascular beds. While visfatin incubation did not produce significant alterations in contractile responses of mesenteric arterial rings to noradrenaline, relaxation responses to acetylcholine but not to sodium nitroprusside (SNP) were significantly reduced in endothelium-intact rings. The inhibitory effect of visfatin on responses to acetylcholine was not observed in endothelium-denuded preparations. Incubation of tissues with nicotinamide phosphoribosyl transferase (NAMPT) inhibitor FK866 or superoxide dismutase (SOD) reversed the inhibitory effects of visfatin on relaxation responses to acetylcholine. Co-incubation of visfatin with Nω-nitro-L-arginine methylester (L-NAME) did not produce a significant alteration in vascular responses to acetylcholine compared to L-NAME incubation alone. Mesenteric PVAT visfatin levels were significantly higher than and correlated positively with plasma visfatin levels. The results of our study indicated that visfatin-induced reductions in endothelium-dependent relaxations of rat isolated small resistance arteries are mediated by oxygen free radicals and a reduction in nitric oxide (NO) bioavailability. It was suggested that increment in systemic and/or local visfatin levels due to various pathologies including obesity and excessive weight gain may play a substantial role in initiation and/or propagation of vascular dysfunctions.