Arteriolar function in visceral adipose tissue is impaired in human obesity.

OBJECTIVE: The purpose of this study was to characterize the relationship between adipose tissue phenotype and depot-specific microvascular function in fat. METHODS AND RESULTS: In 30 obese subjects (age 42±11 years, body mass index 46±11 kg/m(2)) undergoing bariatric surgery, we intraoperatively collected visceral and subcutaneous adipose tissue and characterized depot-specific adipose phenotypes. We assessed vasomotor function of the adipose microvasculature using videomicroscopy of small arterioles (75-250 µm) isolated from different fat compartments. Endothelium-dependent, acetylcholine-mediated vasodilation was severely impaired in visceral arterioles, compared to the subcutaneous depot (P<0.001 by ANOVA). Nonendothelium dependent responses to papaverine and nitroprusside were similar. Endothelial nitric oxide synthase inhibition with N(ω)-nitro-l-arginine methyl ester reduced subcutaneous vasodilation but had no effect on severely blunted visceral arteriolar responses. Visceral fat exhibited greater expression of proinflammatory, oxidative stress-related, hypoxia-induced, and proangiogenic genes; increased activated macrophage populations; and had a higher capacity for cytokine production ex vivo. CONCLUSIONS: Our findings provide clinical evidence that the visceral microenvironment may be intrinsically toxic to arterial health providing a potential mechanism by which visceral adiposity burden is linked to atherosclerotic vascular disease. Our findings also support the evolving concept that both adipose tissue quality and quantity may play significant roles in shaping cardiovascular phenotypes in human obesity.

Long-term successful weight loss improves vascular endothelial function in severely obese individuals.

Obesity is associated with increased cardiovascular risk. Although short-term weight loss improves vascular endothelial function, longer term outcomes have not been widely investigated. We examined brachial artery endothelium-dependent vasodilation and metabolic parameters in 29 severely obese subjects who lost > or =10% body weight (age 45 +/- 13 years; BMI 48 +/- 9 kg/m(2)) at baseline and after 12 months of dietary and/or surgical intervention. We compared these parameters to 14 obese individuals (age 49 +/- 11 years; BMI 39 +/- 7 kg/m(2)) who failed to lose weight. For the entire group, mean brachial artery flow-mediated dilation (FMD) was impaired at 6.7 +/- 4.1%. Following sustained weight loss, FMD increased significantly from 6.8 +/- 4.2 to 10.0 +/- 4.7%, but remained blunted in patients without weight decline from 6.5 +/- 4.0 to 5.7 +/- 4.1%, P = 0.013 by ANOVA. Endothelium-independent, nitroglycerin-mediated dilation (NMD) was unaltered. BMI fell by 13 +/- 7 kg/m(2) following successful weight intervention and was associated with reduced total and low-density lipoprotein cholesterol, glucose, hemoglobin A(1c), and high-sensitivity C-reactive protein (CRP). Vascular improvement correlated most strongly with glucose levels (r = -0.51, P = 0.002) and was independent of weight change. In this cohort of severely obese subjects, sustained weight loss at 1 year improved vascular function and metabolic parameters. The findings suggest that reversal of endothelial dysfunction and restoration of arterial homeostasis could potentially reduce cardiovascular risk. The results also demonstrate that metabolic changes in association with weight loss are stronger determinants of vascular phenotype than degree of weight reduction.