Perivascular adipose tissue mediated aortic reactivity data: Female lean and obese Zucker rats

Female prediabetic rats are protected from vascular dysfunction: the role of nitroso and sulfide signaling

BACKGROUND

The activity of perivascular adipose tissue (PVAT), a specific deposit of adipose tissue surrounding blood vessels, could contribute to sex differences in vascular tone control, particularly in dyslipidemic disorders; however, the mutual associations remain unclear. This study aimed to evaluate the relationships among sex, PVAT and vascular function in Wistar and hereditary hypertriglyceridemic (HTG) rats. Vasoactive responses of the isolated thoracic aorta with preserved or removed PVAT were compared in adult male and female Wistar and HTG rats, and the roles of nitric oxide (NO), hydrogen sulfide (H2S), cyclooxygenase (COX) and inflammatory signaling in vascular function were monitored in females.

RESULTS

HTG rats were hypertensive, but females less than males. Increased 2-h glycemia was observed in HTG rats regardless of sex; however, HTG females exhibited better glucose utilization than males did. Females, independent of strain, had better preserved endothelial function than males did. PVAT inhibited endothelium-dependent relaxation in all the rats except HTG females. In HTG males, pathologically increased aortic contractility was noted; however, in HTG females, the contractile responses were lower, thus approaching physiological levels despite the pro-contractile action of COX products. In HTG females, NO contributed to endothelial function to a lesser extent than it did in controls, but the presence of PVAT eliminated this difference, which corresponded with increased NO synthase activity. Although increased protein expression of several proinflammatory factors (TNFα, IL-6, iNOS, and NfκB) was confirmed in the aortic and PVAT tissue of HTG females, the protein expression of factors regulating the adhesion and infiltration of monocytes (ICAM-1 and MCP-1) was decreased in PVAT. Moreover, in HTG females, unlike in controls, H2S produced by PVAT did not inhibit endothelial relaxation, and regardless of PVAT, endogenous H2S had beneficial anticontractile effects, which were associated with increased protein expression of H2S-producing enzymes in both aortic and PVAT tissues.

CONCLUSIONS

Despite increased inflammation and the pathological impact of cyclooxygenase signaling in female HTG rats, protective vasoactive mechanisms associated with milder hypertension and improved endothelial function and contractility linked to PVAT activity were triggered. Sulfide and nitroso signaling represent important compensatory vasoactive mechanisms against hypertriglyceridemia-associated metabolic disorders and may be promising therapeutic targets in prediabetic females.

Perivascular Adipose Tissue Compensation for Endothelial Dysfunction in the Superior Mesenteric Artery of Female SHRSP.Z-<i>Lepr</i>^<i>fa</i>/IzmDmcr Rats

Regulation of arterial tone by perivascular adipose tissue (PVAT) differs between sexes. In male SHRSP.Z-<i>Lepr</i>^<i>fa</i>/IzmDmcr rats (SHRSP.ZF), PVAT exerts a compensatory relaxation effect for the loss of endothelium-mediated vasorelaxation, which occurs during the early stages of metabolic syndrome. However, this effect deteriorates by 23 weeks of age. Here, therefore, we compared the effects of PVAT in female and male SHRSP.ZF. Acetylcholine-induced relaxation in superior mesenteric artery without PVAT did not differ between 23-week-old females and males. However, the presence of PVAT enhanced relaxation in 23-week-old females, but not in males. The mRNA levels of angiotensin II type 1 receptor (AT1R) in PVAT did not differ between sexes, but AT1R-associated protein (ATRAP) and apelin levels were higher in females than in males. We observed a positive relationship between differences in artery relaxation with and without PVAT and ATRAP or apelin mRNA levels. In 30-week-old females, PVAT-enhanced relaxation disappeared, and mRNA levels of AT1R increased, while apelin levels decreased compared to 23-week-old females. These results demonstrated that in SHRSP.ZF, PVAT compensation for endothelium dysfunction extended to older ages in females than in males. Apelin and AT1R/ATRAP expression in PVAT may be predictors of favorable effects.