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Aim: Irisin is first discovered as a potential mediator of obesity related energy homeostasis. Recent studies indicate that irisin is associated with endothelial dysfunction and atherosclerosis in patients with type 2 diabetes. Our objective was to examine the relationship between irisin and urinary albumin excretion in patients with type 2 diabetes. Methods: 100 newly diagnosed patients with type 2 diabetes and 100 healthy subjects were selected. Serum irisin levels were measured by ELISA, and urine albumin was measured by radioimmunoassay. High resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia (flow-mediated arterial dilation, FMD) and after sublingual glyceryltrinitrate. Results: Patients with type 2 diabetes presented decreased irisin levels when compared to controls (14.12 ± 3.93 versus 28.98 ± 2.56 ng/ml, P = 0.015).Serum irisin levels in the microalbuminuric and macroalbuminuria subgroup were 9.89 ± 1.56 ng/ml and 5.67 ± 1.89 ng/ml, respectively, which were significantly lower than those in the normoalbuminuria (15.97 ± 3.12 ng/ml). In comparison to microalbuminuric subgroup, macroalbuminuria subgroup had lower levels of irisin. By dividing the distribution of serum irisin levels into quartiles, FMD was increased gradually with the increase of serum irisin levels (P < 0.001). Multiple stepwise linear regression analysis showed that FMD (β = 0.75, P = 0.002), 2-hBG (β = -0.25, P = 0.038) and UAE (β = -0.87, P = 0.008) were significantly associated with irisin. Pearson's correlation analyses showed a negative correlation between irisin and logUAE (r = -0.57) and between FMD and logUAE (r = -0.47), and positive correlations between irisin and FMD (r = 0.51). Conclusions: Decreased plasma levels of irisin seem to be associated with UAE and FMD in patients with type 2 diabetes. [ABSTRACT FROM AUTHOR]