Circulating free fatty acids represent additional TLR4 ligands during dyslipidemia caused by the consumption of Western type diet and the data presented here demonstrates more than additive effect of LPS and oleic acid on macrophage activation suggesting that this diet contributes to low grade chronic inflammation by first increasing the release of gut-derived LPS into circulation that can prime the macrophages and secondly by increasing the circulating free fatty acids that can further exacerbate this inflammatory response. This evidence concerns the gene TLR4 and metabolic syndrome.