Effect of Nicotinic Acid on Adipose Tissue Inflammation in Obese Subjects

24 male obese insulin resistant subjects will receive nicotinic acid or placebo for 16 weeks. The last 8 weeks, the subjects will follow a training program calculated to optimize use of lipid. Insulin sensitivity and glucose tolerance will be assessed using, respectively, fasting-based estimates of insulin sensitivity (plasma and muscle) and oral glucose tolerance test. Plasma parameters of adipokines and, inflammatory and metabolic parameters will be determined. As an index of AT inflammation, the percentage and the phenotype of macrophages will be determined using flow cytometry of cells of the stromavascular fraction of subcutaneous AT. Macrophage infiltration will be investigated by light microscopy. The characterization of the inflammatory profile of AT will be completed by measurements of the expression of genes that are either specific markers of human AT macrophages or inflammatory and anti-inflammatory adipokines. This combination of approaches has never been carried out during a pharmacological intervention in humans. The following points will be addressed: * determine the influence of lipolysis on AT inflammation, specifically on macrophage activation and adipokine production. * examine the causal relationship between adipocyte FA metabolism, AT inflammation and insulin sensitivity. * establish whether the beneficial effect of antilipolytic drugs may be attributable at least in part to a decrease in AT inflammation.