We analyzed non-atherosclerotic repair arteries gathered at coronary by-pass operations from 30 patients with type 2 diabetes, as well as from 30 age- and gender-matched non-diabetic individuals. Quantitative proteome analysis was done by iTRAQ-labelling and LC-MS/MS analysis on individual arterial samples. The amounts of the basement membrane (BM) components, alpha-1- and alpha-2- type IV collagen, gamma-1- and beta-2-laminin were significantly increased in patients with diabetes. Moreover, the expressions of basement membrane components and other vascular proteins were significantly lower among metformin users, as compared to non-users. Patients treated with or without metformin had similar levels of HbA1c, cholesterol and blood pressure. In addition, quantitative histomorphometry showed increased area fractions of collagen-stainable material in tunica intima and media among patients with diabetes.