Association between the preoperative fasting and postprandial C-peptide AUC with resolution of type 2 diabetes 6 months following bariatric surgery.

Background And Aims: Bariatric surgery results in the remission of type 2 diabetes mellitus (T2DM) in morbidly obese subjects. The aim of the study was to investigate the predictive value of both static and dynamic measures of C-peptide in relation to T2DM resolution 6 months after bariatric surgery regardless of the operation type.

Methods And Results: A non-randomized prospective study of 24 participants with T2DM undergoing bariatric surgery. Measurements of fasting and 2-hour plasma glucose, insulin, C-peptide and measures of insulin sensitivity were recorded temporally during an oral glucose tolerance test pre-operatively and 6 months post-operatively. A responder was defined with a fasting glucose <5.6 mmol/L and HbA1c <6.0% postoperatively. Within the sample there were 11 responders and 13 non-responders at 6 months. There was a significant difference in the duration of diabetes between the groups. Fasting C-peptide (P≤0.05) and 2-hour C-peptide (P≤0.05) were higher in responders compared to non-responders. Significantly higher C-peptide levels were observed preoperatively at all time points for responders, with significantly higher area under the curve (AUC0-60 and AUC0-120). Using the lower quartiles for C-peptide levels, both fasting C-peptide (>2.5 ng/mL [0.83 nmol/L]) and 2-hour C-peptide (>5.2 ng/mL [1.73 nmol/L]) had a sensitivity and negative predictive value of 100% to predict T2DM remission. Logistic regression showed that C-peptide, duration of diabetes and BMI were associated with response. The area under the ROC curve was 0.94 and a regression model predicted diabetes remission with a sensitivity of 85.7% and a specificity of 88.9%.

Conclusions: This study demonstrated that static (fasting) and dynamic (AUC, 2-hour) C-peptide measurements predict T2DM resolution 6 months following bariatric surgery. This work provides insight into C-peptide dynamics as a predictor of response to bariatric surgery.