Objective-Experimental studies suggest that adipose inflammation is etiologically linked to obesity-induced systemic disease. Our goal was to characterize the state of inflammation in human fat in relation to vascular function and metabolic parameters in obese individuals. Methods and Results-We collected subcutaneous abdominal fat in 77 obese subjects (BMI Ն30 kg/m 2 ) and quantified adipose macrophage population using targeted immunohistochemistry. Brachial artery vasodilator function was examined using high-resolution vascular ultrasound. In 50 subjects, an inflamed adipose phenotype characterized by tissue macrophage accumulation in crown-like structures was associated with systemic hyperinsulinemia and insulin resistance (HOMA-IR 5.5Ϯ4.5 versus 2.6Ϯ1.9, Pϭ0.002) and impaired endothelium-dependent flow-mediated vasodilation (8.5Ϯ4.4% versus 10.8Ϯ3.8%, PϽ0.05), as compared to subjects with quiescent noninflamed adipose architecture (nϭ27). Macrophage retention in fat was linked to upregulated tissue CD68 and tumor necrosis factor (TNF)-␣ mRNA expression in addition to increased plasma hs-CRP. Conclusions-In a cohort of obese subjects, we demonstrate that proinflammatory changes in adipose tissue are associated with systemic arterial dysfunction and insulin resistance. These findings suggest that adipose inflammation may be linked to vascular injury and increased cardiovascular risk in obese subjects. (Arterioscler Thromb Vasc Biol. 2008;28:1654-1659)Key Words: obesity Ⅲ endothelium Ⅲ inflammation Ⅲ insulin Ⅲ vasculature O besity represents a disease state characterized by chronic subclinical inflammation linked to increased risk of type-2 diabetes and atherosclerosis. 1,2 Although the stimulus or source for persistent immune activation remains unclear, fat tissue is increasingly being recognized as an important hotbed of metabolic activity and a significant source of proatherogenic and proinflammatory adipocytokines that orchestrate metabolic and vascular dysfunction. 3,4 Animal studies suggest that adipose tissue macrophage (ATM) activity is functionally intertwined with systemic disease mechanisms. [5][6][7] The pathogenic link is supported by pharmacogenetic studies demonstrating that attenuation of ATM influx alters cytokine production and improves insulin sensitivity. 8,9 From a clinical perspective, inflammatory changes in fat have not been commonly investigated in human disease nor examined in the context of functional cardiovascular abnormalities.Inflammatory mechanisms are critical to all stages of cardiovascular disease progression and play a causal role in vascular endothelial dysfunction that represents a crucial early event in atherosclerosis and subsequent coronary heart disease (CHD) events. 10,11 These mechanisms are, in part, supported by local and systemic release of inflammatory cytokines that mediate activation of neutrophils, monocytes, and T-cells, promote lipid-laden foam cell accumulation, weaken atherosclerotic plaque stability, and impair nitric oxide (NO)-mediated endothelium-depend...

Inflammation and infiltration of immune cells in white adipose tissue have been implicated in the development of obesity-associated insulin resistance. Likewise, dysregulation of the fuel-sensing enzyme AMP-activated protein kinase (AMPK) has been proposed as a pathogenetic factor for these abnormalities based on both its links to insulin action and its anti-inflammatory effects. In this study, we examined the relationships between AMPK activity, the expression of multiple inflammatory markers in visceral (mesenteric and omental) and abdominal subcutaneous adipose tissue, and whole-body insulin sensitivity in morbidly obese patients (BMI 48 ± 1.9 kg/m2) undergoing gastric bypass surgery. AMPK activity was assessed by western-blots (P-AMPK/T-AMPK) and mRNA levels of various markers of inflammation by qRT-PCR. Patients were stratified as insulin sensitive obese or insulin resistant obese according to their HOMA-IR values. The results indicate that AMPK activity is lower in visceral than in subcutaneous abdominal adipose tissue of these patients and that this is associated with an increased expression of multiple inflammatory genes. They also revealed that AMPK activity is lower in adipose tissue of obese patients who are insulin resistant (HOMA-IR > 2.3) than in BMI-matched insulin sensitive subjects. Furthermore, this difference was evident in all three fat depots. In conclusion, the data suggest that there are close links between reduced AMPK activity and inflammation in white adipose tissue, and whole-body insulin resistance in obese humans. Whether adipose tissue AMPK dysregulation is a causal factor for the development of the inflammation and insulin resistance remains to be determined.

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 yr, BMI 46±11 kg/m2) undergoing bariatric surgery, we intra-operatively 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). Non-endothelium dependent responses to papaverine and nitroprusside were similar. Endothelial nitric oxide synthase (eNOS) inhibition with Nω-nitro-L-arginine methyl ester (L-NAME) 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 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.

Background: Multiple diet quality scores have been used to evaluate adherence to specific dietary recommendations or

Background Experimental studies suggest that visceral adiposity and adipose tissue dysfunction play a central role in obesity-related cardiometabolic complications. Impaired angiogenesis in fat has been implicated in the development of adipose tissue hypoxia, capillary rarefaction, inflammation, and metabolic dysregulation, but pathophysiological mechanisms remain unknown. In this study, we examined the role of a novel anti-angiogenic isoform of vascular endothelial growth factor-A (VEGF-A), VEGF-A165b, in human obesity. Methods and Results We biopsied paired subcutaneous and visceral adipose tissue in 40 obese subjects (BMI 45±8 kg/m2, age 45±11 yr) during bariatric surgery and characterized depot-specific adipose tissue angiogenic capacity using an established ex vivo assay. Visceral adipose tissue exhibited significantly blunted angiogenic growth compared to subcutaneous fat (p<0.001) which was associated with marked tissue up-regulation of VEGF-A165b (p=0.004). Extent of VEGF-A165b expression correlated negatively with angiogenic growth (r= -0.6, p=0.006). While recombinant VEGF-A165b significantly impaired angiogenesis, targeted inhibition of VEGF-A165b with neutralizing antibody stimulated fat pad neovascularization and restored VEGF receptor activation. Blood levels of VEGF-A165b were significantly higher in obese subjects compared to lean controls (p=0.02), and surgical weight loss induced a marked decline in serumVEGF-A165b (p=0.003). Conclusions We demonstrate that impaired adipose tissue angiogenesis is associated with over- expression of a novel anti-angiogenic factor VEGF-A165b that may play a pathogenic role in human adiposopathy. Moreover, systemic up-regulation of VEGF-A165b in circulating blood may have wider ranging implications beyond the adipose milieu. VEGF-A165b may represent a novel area of investigation to gain further understanding of mechanisms that modulate cardiometabolic consequences of obesity.

BACKGROUND:A low-grade state of adipose tissue inflammation associated with obesity has been linked to mechanisms of systemic metabolic dysfunction. However, the relation of clinical phenotypes to depot-specific inflammation has not been well examined in human obesity.OBJECTIVE:To characterize the inflammatory status of subcutaneous and visceral fat depots, as assessed by tissue presence of macrophage crown-like structures (CLS) as a hallmark of chronic inflammation, and determine the relation of systemic insulin resistance to inflammatory abnormalities in subcutaneous and visceral fat.METHODS:We collected adipose tissue simultaneously from subcutaneous and visceral (omental and mesenteric) depots in 92 obese participants (age 42±11 years; BMI⩾30 kg m−2) during planned bariatric surgery. Using immunohistochemistry, we categorized individuals as CLS+ or CLS− based on the presence or absence, respectively, of macrophage CLS in subcutaneous (CLSs), omental (CLSo) and mesenteric (CLSm) adipose depots.RESULTS:The majority of participants exhibited adipose tissue inflammation manifest by the presence of CLS (CLS+) in both subcutaneous and intra-abdominal visceral depots. CLS status in subcutaneous fat was highly sensitive and modestly specific for inflammation of visceral fat. In multivariable models, plasma insulin and homeostatis model assessment levels were positively associated with CLS+ status in all depots independent of age, waist circumference, BMI and type 2 diabetes, and worsened with the increasing number of adipose regions involved.CONCLUSIONS:In severely obese participants, systemic insulin resistance is linked to adipose inflammation in both subcutaneous and visceral depots. The findings suggest that examination of subcutaneous regions that are more easily accessible by transcutaneous biopsy may prove useful in clinical studies designed to investigate adipose phenotypes in relation to human disease.

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 ≥10% body weight (age 45 ± 13 years; BMI 48 ± 9 kg/m2) 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/m2) 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/m2 following successful weight intervention and was associated with reduced total and low‐density lipoprotein cholesterol, glucose, hemoglobin A1c, 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.

Objective The purpose of this study was to determine whether obese individuals with reduced adipose tissue inflammation exhibit a more favorable cardiovascular risk profile. Background Obesity is associated with a low-grade state of chronic inflammation that may be causally related to cardiometabolic disease. Methods Using immunohistochemistry, we categorized obese individuals dichotomously as having inflamed fat (n=78) or non-inflamed fat (n=31) based on the presence (+) or absence (-) of macrophage crown-like structures (CLS) in subcutaneous abdominal fat biopsy samples. We compared their metabolic, vascular, and adipose tissue characteristics to lean subjects (n=17). Results Inflamed CLS+ obese individuals displayed higher plasma insulin, HOMA, triglycerides, glucose, blood pressure, hs-CRP, LDL-C, and lower HDL-C and brachial artery flow-mediated dilation (FMD) compared to leans (p<0.05). Adipose mRNA expression of inflammatory genes including CD68, leptin, MMP-9, CD163, and CD8A were significantly greater and VEGF lower in the CLS+ group (p<0.05). In contrast, obese subjects with non-inflamed fat exhibited a mixed clinical phenotype with lower insulin resistance, reduced proatherogenic gene expression, and preserved vascular function as in lean subjects. In multiple linear regression adjusting for age and gender, CLS status (beta = -0.28, p=0.008) and waist circumference (beta = -0.25, p =0.03) were independent predictors of FMD. Conclusion These findings lend support to the novel concept that factors in addition to absolute weight burden, such as qualitative features of adipose tissue, may be important determinants of cardiovascular disease. Therapeutic modulation of the adipose phenotype may represent a target for treatment in obesity.