Gene expression profiling of human adipose tissue of obese subjects in relation to bariatric surgery

In human obesity, the stroma vascular fraction (SVF) of white adipose tissue (WAT) is enriched in macrophages. These cells may contribute to low-grade inflammation and to its metabolic complications. Little is known about the effect of weight loss on macrophages and genes involved in macrophage attraction. We examined subcutaneous WAT (scWAT) of 7 lean and 17 morbidly obese subjects before and 3 months after bypass surgery. Immunomorphological changes of the number of scWAT-infiltrating macrophages were evaluated, along with concomitant changes in expression of SVF-overexpressed genes. The number of scWAT-infiltrating macrophages before surgery was higher in obese than in lean subjects (HAM56+/CD68+; 22.6 +/- 4.3 vs. 1.4 +/- 0.6%, P < 0.001). Typical "crowns" of macrophages were observed around adipocytes. Drastic weight loss resulted in a significant decrease in macrophage number (-11.63 +/- 2.3%, P < 0.001), and remaining macrophages stained positive for the anti-inflammatory protein interleukin 10. Genes involved in macrophage attraction (monocyte chemotactic protein [MCP]-1, plasminogen activator urokinase receptor [PLAUR], and colony-stimulating factor [CSF]-3) and hypoxia (hypoxia-inducible factor-1alpha [HIF-1alpha]), expression of which increases in obesity and decreases after surgery, were predominantly expressed in the SVF. We show that improvement of the inflammatory profile after weight loss is related to a reduced number of macrophages in scWAT. MCP-1, PLAUR, CSF-3, and HIF-1alpha may play roles in the attraction of macrophages in scWAT. Keywords: disease state analysis Seventeen Caucasian morbidly obese women undergoing laparoscopic Roux-en-Y bypass were enrolled at Hôtel Dieu Hospital, Paris, France. ScWAT biopsies were performed by a surgeon after local anesthesia (1% xylocaine) of the periumbilical area. A portion of each scWAT biopsy was immediately frozen for RNA extraction and analysis. To study the effects of weight loss on scWAT gene expression, we processed 10 high-quality RNAs from scWAT biopsies collected before/after bypass by microarray technique. Total RNA was prepared using the RNeasy total RNA Mini kit (Qiagen). RNA concentration and integrity were assessed using the Agilent 2100 Bioanalyzer (Agilent Technologies, Massy, France). For microarray experiments, 1 µg of total RNA from each total RNA sample preparation was amplified by MessageAmp RNA Kit (Ambion, Austin, TX, USA) and 3 µg of amplified RNA was labeled with cyanin dyes (Cy) using the CyScribe First-Strand cDNA labeling kit (Amersham Biosciences, Orsay, France). (available at http://cmgm.stanford.edu/pbrown/protocols/index). aRNA extracted from each scWAT sample before surgery was labeled with Cy3 dye, while the aRNA from each scWAT sample obtained 3 months after surgery was labeled with Cy5 dye. Several quality cross-checks (for total RNA quality, aRNA quality, dye incorporation efficiency, etc.) and microarray "dye swap" experiments were performed. The labeled cDNA mixtures were hybridized according to the protocol described at http://cmgm.stanford.edu/pbrown/protocols/index