Background Adiponectin is an adipokine with insulin-sensitising and anti-atherogenic properties.The aim of this study was to investigate whether low adiponectin levels predict the impairment of endothelial function in newly diagnosed type 2 diabetic patients in an 8-year prospective study.Methods In the prospective study,we enrolled 133 newly diagnosed type 2 diabetic patients without subclinical atherosclerosis and gave them intensive therapy; the mean treatment period was 8 years.Intensive treatment was a stepwise implementation of behavior modification and pharmacological therapy targeting hyperglycaemia,hypertension,dyslipidaemia and obesity.We measured baseline circulating adiponectin with an enzyme-linked immunosorbent assay,endothelium-dependent and -independent vasodilation by high-resolution vascular ultrasound.At year 8,102 patients were reexamined for endothelium-dependent and -independent vasodilation.Results Sex-adjusted adiponectin level was positively correlated with endothelium-independent vasodilation both at baseline (r＝0.150,P＝0.043) and at year 8 (r＝0.339,P＝0.001),whereas no association was found between adiponectin and endothelium-dependent vasodilation.In a stepwise multivariate linear regression model,adiponectin was an independent predictor for impaired endothelium-independent vasodilation at year 8 (P＝0.001).Conclusions Plasma adiponectin concentration was associated with endothelium-independent vasodilation and hypoadiponectinemia predicted the impairment of endothelium-independent vasodilation in newly diagnosed type 2 diabetic patients under multifactorial intervention.These data support the causative link of impairment of endothelium-independent vasodilation with hypoadiponectinemia.