Circulating dickkopf-1 in diabetes mellitus: association with platelet activation and effects of improved metabolic control and low-dose aspirin.

BACKGROUND: Dickkopf-1 (DKK-1) is a major regulator of the Wnt signaling pathway, involved in inflammation, atherogenesis, and the regulation of glucose metabolism. Because platelets are major contributors to circulating levels of DKK-1 in other clinical settings, we aimed at characterizing the platelet contribution to DKK-1 in type 2 diabetes mellitus (T2DM) and evaluating associations of DKK-1 with glucose metabolism, platelet activation, and endothelial dysfunction. METHODS AND RESULTS: A cross-sectional comparison of DKK-1, soluble CD40L (sCD40L; reflecting platelet-mediated inflammation), asymmetric dimethylarginine (ADMA; marker of endothelial dysfunction), and urinary 11-dehydro-thromboxane B2 (in vivo marker of platelet activation) was performed among 214 diabetic patients (90 receiving aspirin at 100 mg/day) and 30 healthy controls. Plasma DKK-1 levels were markedly higher in patients with T2DM than in healthy patients (P<0.0001). DKK-1 levels were significantly lower in diabetic patients receiving compared with those not on aspirin treatment (P=0.008); in the latter, DKK-1 was significantly correlated with 11-dehydro-thromboxane B2, ADMA, and CD40L (ρ=0.303. P<0.0001, ρ=0.45. P<0.0001, and ρ=0.37, P<0.0001, respectively) but not with glycemic control or DM duration. Among patients not receiving aspirin, improvement of metabolic control in a subgroup of newly diagnosed patients treated with acarbose for 20 weeks and in a group treated with rosiglitazone for 24 weeks was associated with concurrent significant reductions in DKK-1 (P=0.005 and P=0.004) and 11-dehydro-thromboxane B2 (P=0.005 and P=0.004). CONCLUSIONS: Circulating DKK-1 is increased in T2DM and associated with endothelial dysfunction and platelet activation. Plasma DKK-1 levels are reduced with improvement of glycemic control and low-dose aspirin treatment.