ICAM-1 expression in adipose tissue: effects of diet-induced obesity in mice

1 Section of Leukocyte Biology, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, 2 Department of Immunology, Baylor College of Medicine, and 3 Agricultural Research Service, United States Department of Agriculture, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas; and 4 Research Centre for Reproductive Health, School of Pediatrics and Reproductive Health, University of Adelaide, Adelaide, Australia Submitted 10 January 2006 ; accepted in final form 5 June 2006 Obesity has been linked to cardiovascular disease, hypertension, diabetes and the metabolic syndrome, with elevated markers of systemic inflammation. Intercellular adhesion molecule-1 (ICAM-1) is a transmembrane adhesion molecule involved in leukocyte migration to sites of inflammation. In human obesity, elevated expression of the soluble form of ICAM-1 (sICAM-1) is positively correlated with abdominal fat deposition. Increases in adiposity have also been correlated with macrophage infiltration into adipose tissue. Here we investigate adipose tissue production and transcriptional regulation of ICAM-1 in a mouse model of dietary obesity. After feeding mice a high-fat diet, ICAM-1 expression in serum and adipose tissue was analyzed by ELISA, Northern blotting, real-time quantitative PCR, and flow cytometry. After 6 mo on the high-fat diet, sICAM-1 levels significantly correlated with body weight and abdominal fat mass. ICAM-1 mRNA was expressed in adipose tissue of mice, with significantly higher levels in males than females. After only 3 wk, there were adipose tissue-specific increases in mRNAs for ICAM-1, IL-6, and monocyte chemoattractant protein-1 (MCP-1) in male mice. Analysis of the stromal-vascular fraction of male adipose tissue revealed CD11b-negative cells with increased surface ICAM-1 and CD34. We also found two populations of F4/80+, CD11b+, ICAM-1+ cells, one of which also expressed CD14 and CD11c and was increased in response to a high-fat diet. These results indicate that within 3 wk on a high-fat diet, male mice exhibited significant increases in pro-inflammatory factors and immune cell infiltration in adipose tissue that may represent links between obesity and its associated inflammatory complications. sICAM-1; CD11c; CD34; adipocytes; macrophage Address for reprint requests and other correspondence: C. Wayne Smith, Section of Leukocyte Biology, Dept. of Pediatrics, Baylor College of Me