The purpose of the study was to characterize the action of mesoglycan on vascular endothelium through the non-invasive assessment of vascular reactivity humeral artery by comparing effects of mesoglycan on Flow Mediated Dilatation (FMD) of the humeral artery between a group of patients with metabolic syndrome assuming placebo and a group of patient with metabolic syndrome assuming mesoglycan; firstly after administration of the drug/placebo intramuscularly, and then, in a study of medium-term after oral intake of drug/placebo. The selection of patients with metabolic syndrome is related to the fact that this syndrome is associated with alterations in endothelial function and a high incidence of cardiovascular events. So it is a condition that offers the opportunity to explore the hypothesis that the mesoglycan may have a favorable effect on early vascular alterations that precede clinical events.