['Resistin could be the linkage between the adipose tissue and the insulin resistance. In humans, the role of resistin on metabolic and vascular homeostasis is not well defined. The aim of this study was to investigate the possible association between resistin expression and insulin resistance.', 'We evaluated the relationship between monocyte expression of mRNA and anthropometric and metabolic parameters of insulin resistance. We focused on the potential role of resistin on endothelial function. Thirty-nine patients with metabolic syndrome (MS) and clinically free from cardiovascular disease, and 15 healthy subjects were included in this study. All subjects underwent clinical examination, assessment of haematochemical parameters, bioimpedentiometry, measurement of monocyte resistin mRNA and of brachial-artery flow-mediated vasodilation (FMV). Patients with MS showed higher levels of interleukin-6 (IL; 2.1 +/- 1.2 vs. 1.2 +/- 0.9 pg/mL, P < 0.05) and reduced FMV (5.4 +/- 3.9 vs. 8.3 +/- 3.1%, P < 0.05). The subjects were divided into two groups: (i) subjects with high expression mRNA resistin levels and (ii) subjects with low or not detectable; Group 1 was younger (50 +/- 13 vs. 59 +/- 11 years, P = 0.01), showed higher IL-6 values (2.3 +/- 1.2 vs. 1.6 +/- 1.2, P = 0.03) and lower values of FMV (4.3 +/- 2.8 vs. 7.4 +/- 3.9%, P = 0.003). With univariate analysis monocyte mRNA showed a significant positive correlation with waist circumference (r = 0.27, P < 0.05) and IL-6 (r = 0.26, P < 0.05) and a negative correlation with FMV (r = -0.38, P < 0.005). With multivariate regression analysis brachial-artery diameter, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, IL-6 and RNAm resistin expression were independent predictors of reduced FMV.'] Is endothelial dysfunction in vivo related to monocyte resistin mRNA expression?