Angiotensin II Type 1 Receptor Antagonist Azilsartan Restores Vascular Reactivity Through a Perivascular Adipose Tissue-Independent Mechanism in Rats with Metabolic Syndrome.

Perivascular adipose tissues (PVAT) are involved in the regulation of vascular tone. In mesenteric arteries, the compensatory vasodilatory effects of PVAT appear when vascular relaxation is impaired and disappear at around 23 weeks of age in SHRSP.Z-Leprfa/IzmDmcr (SHRSP.ZF) rats with metabolic syndrome (MetS). The renin-angiotensin system is involved in the development of endothelium and vascular dysfunction. Therefore, we investigated whether azilsartan, a potent angiotensin II type 1 (AT1) receptor antagonist, can protect against the deterioration of the PVAT compensatory vasodilator function that occurs with aging in MetS. Two age groups of SHRSP.ZF rats (13 and 20 weeks of age) were administered azilsartan or vehicle through oral gavage once daily for 10 weeks. The vasodilation response of the isolated superior-mesenteric arteries upon addition of endothelium-dependent and -independent agonists was determined in the presence or absence of PVAT using organ bath methods. In vivo treatment with azilsartan improved the acetylcholine-induced vasodilation in mesenteric arteries with and without PVAT at both time-points. The mRNA levels of AT1 receptor and AT1 receptor-associated protein were unchanged in PVAT upon azilsartan treatment. Furthermore, in vitro treatment with azilsartan (0.1 and 0.3 μM for 30 min) did not affect the compensatory effect of PVAT on vasodilation in response to acetylcholine in SHRSP.ZF rat mesenteric arteries. Our results provide evidence supporting the use of azilsartan for the long-term protection against vascular dysfunctions in MetS. Azilsartan did not improve the dysfunction of PVAT-mediated modulation of vascular tone during MetS. The protective effect of azilsartan is mediated by restoring the endothelium- and vascular smooth muscle-mediated mechanisms.