Uncoupling of Endothelial Nitric Oxide Synthase in Perivascular Adipose Tissue of Diet-Induced Obese Mice

Abstract

induced obesity, namely uncoupling of the endothelial nitric oxide (NO) synthase (eNOS) in PVAT. Materials and MethodsMaterials and Methods are available in the online-only Data Supplement.© 2015 American Heart Association, Inc. Objective-The present study was conducted to investigate the contribution of perivascular adipose tissue (PVAT) to vascular dysfunction in a mouse model of diet-induced obesity. Approach and Results-Obesity was induced in male C57BL/6J mice with a high-fat diet for 20 weeks, and vascular function was studied with myograph. In PVAT-free aortas isolated from obese mice, the endothelium-dependent, nitric oxide-mediated vasodilator response to acetylcholine remained normal. In contrast, a clear reduction in the vasodilator response to acetylcholine was observed in aortas from obese mice when PVAT was left in place. Adipocytes in PVAT were clearly positive in endothelial nitric oxide synthase (eNOS) staining, and PVAT nitric oxide production was significantly reduced in obese mice. High-fat diet had no effect on eNOS expression but led to eNOS uncoupling, evidenced by diminished superoxide production in PVAT after eNOS inhibition. As mechanisms for eNOS uncoupling, arginase induction and l-arginine deficiency were observed in PVAT. Obesity-induced vascular dysfunction could be reversed by ex vivo l-arginine treatment and arginase inhibition. Conclusions-Diet-induced obesity leads to Results Role of PVAT in Vascular Dysfunction in Diet-Induced Obese MiceMale C57BL/6J mice were fed with either HFD or normal control diet (NCD) for 20 weeks starting at the age of 8 weeks.The HFD-treated mice developed obesity (Table). Vasodilator response to acetylcholine was studied using aortas with or without PVAT in a wire myograph system. In aortas without PVAT, no significant differences in endothelium-dependent, NO-mediated vasodilator response to acetylcholine were found between NCD and HFD groups ( Figure 1A). In contrast, a clear reduction in the vasodilator response to acetylcholine was observed in the aorta of obese animals compared with lean controls when PVAT was left intact ( Figure 1B). The acetylcholine-induced vasodilation in the mouse aorta was NO-dependent because it could be completely blocked by the NO synthase inhibitor N G -nitro-l-arginine methyl ester (l-NAME; Figure 1C). In endothelium-denuded aortic rings from control mice, acetylcholine induced a significant vasodilation if PVAT was left intact ( Figure I in the online-only Data Supplement). The PVAT-mediated vasodilation was preventable with l-NAME, indicating that PVAT-derived NO contributes to acetylcholine-induced vasodilation under normal conditions. Reduced NO Production in PVAT of Diet-Induced Obese MiceTo directly access NO production from PVAT, time-lapse fluorescence imaging was performed with aorta sections prepared from NCD or HFD-fed mice stained with the fluorescent NO probe 4,5-diaminofluorescein diacetate. As shown in Figure 1D, basal NO production could be detected in PVAT. The PVAT NO production was enhanced by ace...

Obesity-Related Perivascular Adipose Tissue Damage Is Reversed by Sustained Weight Loss in the Rat

“…The reasons for this are unclear, but increased levels of reactive oxygen species have been reported to lead to the uncoupling of eNOS resulting in the formation of perioxynitrite rather than NO. 31,48 This is supported by previous data from our laboratory showing free radical scavengers can rescue PVAT anticontractile function in human obesity 10 and the recent work of Xia et al 42 showing eNOS uncoupling within aortic PVAT from high-fat fed mice.…”

“…Moreover, a recent study reported increased macrophage infiltration in the aortic PVAT of obese mice when identified using either CD68 or F4/80. 42 Eosinophils play a role in sustaining anti-inflammatory M2 macrophages within the adipose tissue, 43 and recent studies within our laboratory have shown a loss of PVAT anticontractile effect in ΔdbGATA-F2 mice, which are deficient in eosinophils. 44 We show a reduction in the number of eosinophils within PVAT in diet-induced obesity and an inverse correlation with body weight, consistent with reports in perigonadal adipose tissue from obese mice.…”

Endothelial Functions

“…34 Second, diet-induced obesity caused eNOS uncoupling in PVAT by arginase-induced L-arginine deficiency. 35 Of note, obesity-induced loss of anticontractile effect of PVAT was reversed by calorie restriction. 36 Taken together, these new lines of evidence represent the therapeutic potential of targeting PVAT in the treatment of cardiovascular disease associated with vascular dysfunction.…”

Remote Effects of Transplanted Perivascular Adipose Tissue on Endothelial Function and Atherosclerosis

“…However, mounting evidence suggests that in disease states, PVAT contributes to endothelial dysfunction, neointimal formation, atherosclerosis, and other cardiovascular diseases, including abdominal aortic aneurysms, aortic stiffness, and vasculitis [4–12]. Mechanistically, these effects have been linked to local inflammation, oxidative stress, and decreased nitric oxide (NO) release from endothelium along with uncoupling of endothelial NO synthase (eNOS) in PVAT [13, 14]. …”