Circulating thrombomodulin and hematological alterations in type 2 diabetic patients with retinopathy

To clarify the relationship between circulating thrombomodulin (TM) and endothelial cell damage in diabetes mellitus, plasma levels of TM were quantitated by an enzyme linked immunoabsorbant assay (ELISA) in 164 type 2 diabetes mellitus and 72 normal control subjects, and these levels were compared with those of von Willebrand factor antigen (vWf: Ag), thrombin antithrombin III complexes (TAT), plasmin-alpha2-plasmin inhibitor complexes (PIC), fibrinogen, D-dimer, urinary albumin excretion rate (AER), intima-media thickness (IMT) and plaque score of the common carotid artery assessed with high resolution B-mode ultrasonography. Plasma levels of TM, vWf: Ag, TAT, PIC, AER, IMT and plaque score were significantly increased in the diabetic patients compared to the normal control subjects. Plasma TM levels showed significant correlation with vWf: Ag (r=0.350, p<0.0001), TAT (r = 0.334, p < 0.0001), PIC (r = 0.450, p < 0.0001), AER (r = 0.334, p < 0.0001), IMT (r = 0.181, P<0.01), plaque score (r=0.385, p<0.0001). Among four groups of diabetic patients, divided based on their severity of diabetic retinopathy, there were no significant differences in age, sex, systolic and diastolic blood pressure levels, HbA,1c, or plasma lipid levels, although the plasma levels of TM, vWf: Ag, TAT, PIC, AER, IMT and the plaque score in the patients with proliferative retinopathy were significantly higher than those of the healthy controls and patients with simple retinopathy. Among the 43 normoalbuminuric patients without intima-media thickness or thickened plaque (AER<30 mg/g Creatinine, IMT<1.0 mm, plaque score = 0), plasma levels of TM, vWf: Ag, TAT, PIC were significantly higher in those patients with retinopathy than in those without retinopathy. Multivariate analysis showed TM, TAT and PIC levels to be independent predictors of diabetic retinopathy. In conclusion, circulating TM reflects endothelial cell damage in patients with diabetic retinopathy, and hypercoagulability might play an important role in endothelial cell damage.