C-peptide is a surrogate of the pancreatic beta cell mass. However, the clinical significance of C-peptide in a diabetic patient after bariatric surgery has not been studied clearly.From February 2005 to January 2009, a total of 205 (124 females and 81 males) consecutive morbidly obese patients with type 2 diabetes mellitus (T2DM) enrolled in a surgically supervised weight loss program with at least 1 year follow-up were examined. Among them, 147 patients (71.7%) received gastric bypass procedures, while the other 58 patients (28.3%) received restrictive-type procedures.The mean C-peptide before the surgery was 5.3 ± 3.5 ng/ml. One hundred nineteen patients (58.0%) had an elevated C-peptide (4 ng/ml), while 2 patients (1.0%) had a low C-peptide (1.0 ng/ml). Multivariate analysis confirmed that waist circumference, triglycerides, and HbA1c were the independent predictors for the elevation of C-peptide. It was observed that the mean C-peptide levels decreased to 1.7 ± 0.9 ng/ml 1 year after bariatric surgery with a mean reduction of 64.1%. One year after surgery, 160 patients (78.0%) out of a total of 205 patients had a remission of their T2DM. Patients in the bypass group had a higher diabetes remission rate (91.2%; 134 out of 147) in comparison to patients in the restrictive group (44.8%; 26 out of 58, p 0.001). The diabetes remission rates for those with preoperative C-peptide3, 3-6, and 6 ng/ml were 26 out of 47 (55.3%), 87 out of 108 (82.0%), and 47 out of 52 (90.3%), p 0.001, respectively.Baseline C-peptide is commonly elevated in morbidly obese patients with T2DM. There was a marked reduction in C-peptide after a significant weight reduction 1 year after surgery with a T2DM remission rate of 78.0%. Thus, bariatric surgery is recommended for obesity-related T2DM patients with elevated C-peptide.
