as a common factor of both type 2 diabetes mellitus (T2dM) and acute coronary syndrome (acS), circulating microparticles (MPs) may provide a link between these two diseases. The present study compared the content and function of MPs from patients with acS with or without T2dM. MPs from healthy subjects (n=20), patients with acS (n=24), patients with T2dM (n=20) and patients with combined acS and T2dM (n=24) were obtained. after incubating rat thoracic tissue with MPs, the effect of MPs on endothelial-dependent vasodilatation, expression of caveolin-1 and endothelial nitric oxide synthase (eNOS), phosphorylation of enoS at the S1177 and T495 sites and its association with heat shock protein 90 (Hsp90), and the generation of no and superoxide anion (o 2˙-) were determined. MP concentrations were higher in patients with T2dM and patients with acS with or without T2dM than in healthy subjects. Moreover, MPs from patients with T2dM or acS led to impairment in endothelial-dependent vasodilatation, decreased expression of no, as well as enoS and its phosphorylation at Ser1177 and association with Hsp90, but increased enoS phosphorylation at T495, caveolin-1 expression and o 2˙-generation. These effects were strengthened by MPs from patients with acS combined with T2dM. T2dM not only increased MP content but also resulted in greater vascular impairment effects in acS. These results may provide novel insight into the treatment of patients with acS and T2dM.