We then found that circulating CILP-2 levels had a progressive increase from normal to IGT (a pre-diabetic status) and then to diabetes, which was correlated positively with WHR, triglyceride, FBG, 2-h blood glucose after glucose overload (2h-BG), HbA1c, FIns, 2h-Ins, and HOMA-IR but negatively with HDL-C. CILP-2 expression was increased in the liver and muscle but decreased in adipose tissues of obese mice or T2DM patients.