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. 2009 Mar;58(3):718-25.
doi: 10.2337/db08-1098. Epub 2008 Dec 15.

Reduced adipose tissue oxygenation in human obesity: evidence for rarefaction, macrophage chemotaxis, and inflammation without an angiogenic response

Magdalena Pasarica  1 , Olga R Sereda, Leanne M Redman, Diana C Albarado, David T Hymel, Laura E Roan, Jennifer C Rood, David H Burk, Steven R Smith
Affiliations

Reduced adipose tissue oxygenation in human obesity: evidence for rarefaction, macrophage chemotaxis, and inflammation without an angiogenic response

Magdalena Pasarica et al. Diabetes. 2009 Mar.

Abstract

Objective: Based on rodent studies, we examined the hypothesis that increased adipose tissue (AT) mass in obesity without an adequate support of vascularization might lead to hypoxia, macrophage infiltration, and inflammation.

Research design and methods: Oxygen partial pressure (AT pO2) and AT temperature in abdominal AT (9 lean and 12 overweight/obese men and women) was measured by direct insertion of a polarographic Clark electrode. Body composition was measured by dual-energy X-ray absorptiometry, and insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Abdominal subcutaneous tissue was used for staining, quantitative RT-PCR, and chemokine secretion assay.

Results: AT pO2 was lower in overweight/obese subjects than lean subjects (47 +/- 10.6 vs. 55 +/- 9.1 mmHg); however, this level of pO2 did not activate the classic hypoxia targets (pyruvate dehydrogenase kinase and vascular endothelial growth factor [VEGF]). AT pO2 was negatively correlated with percent body fat (R = -0.50, P < 0.05). Compared with lean subjects, overweight/obese subjects had 44% lower capillary density and 58% lower VEGF, suggesting AT rarefaction (capillary drop out). This might be due to lower peroxisome proliferator-activated receptor gamma1 and higher collagen VI mRNA expression, which correlated with AT pO2 (P < 0.05). Of clinical importance, AT pO2 negatively correlated with CD68 mRNA and macrophage inflammatory protein 1alpha secretion (R = -0.58, R = -0.79, P < 0.05), suggesting that lower AT pO2 could drive AT inflammation in obesity.

Conclusions: Adipose tissue rarefaction might lie upstream of both low AT pO2 and inflammation in obesity. These results suggest novel approaches to treat the dysfunctional AT found in obesity.

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Figures

FIG. 1.
FIG. 1.
AT pO2 and AT temperature are inversely correlated with percent body fat. AT pO2, measured by direct insertion of a micro Clark-type electrode into abdominal subcutaneous AT, was lower in overweight/obese group (O/O) compared with lean subjects (A) and inversely correlated with percent body fat (B). AT temperature measured by a thermocouple inserted into the abdominal AT was inversely correlated with percent body fat (C). Males are represented by squares and females by circles, filled with different colors as follows: white for lean, gray for O/O without type 2 diabetes, and black for O/O with type 2 diabetes.
FIG. 2.
FIG. 2.
Vascularization of AT. Representative AT sections from lean (A) and O/O (B) subjects stained with UEA lectin (orange) to label capillaries and with GS lectin (green) to label the adipocyte plasmalemma. Capillary density (C) was measured and averaged across 6–10 histological sections for each subject and VEGF mRNA expression measured by quantitative RT-PCR (D); both were lower in O/O versus lean subjects. VEGF mRNA was positively correlated with capillary density (E) and PPARγ1 mRNA (G) and inversely with percent body fat (F). H: Collagen VI (COL6) mRNA was negatively correlated with AT pO2. Males are represented by squares and females by circles, filled with different colors as follows: white for lean, gray for O/O without type 2 diabetes, and black for O/O with type 2 diabetes. (Please see http://dx.doi.org/10.2337/db08-1098 for a high-quality digital representation of this figure.)
FIG. 3.
FIG. 3.
Hypoxia and AT inflammation. AT pO2 was inversely correlated with the inflammation markers CD68 mRNA (A) and MAC 2/CD163 mRNA (B), with the chemokine MIP1α mRNA expression (C) and MIP1α secretion into culture media ex vivo (D). Previous studies in our lab demonstrated a strong correlation between MAC2/CD163 and CD68 mRNA and macrophage infiltration by macrophage staining in AT sections by immunohistochemistry (R2 = 0.77, P < 0.001) (B. Kozak, J. Gimble, S.R. Smith, unpublished data). Males are represented by squares and females by circles, filled with different colors as follows: white for lean, gray for O/O without type 2 diabetes, and black for O/O with type 2 diabetes.
See this image and copyright information in PMC

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