A reliable serum C-peptide index for the selection of an insulin regimen to achieve good glycemic control in obese patients with type 2 diabetes: an analysis from a short-term study with intensive insulin therapy

Insulin regimens achieving favorable glycemic control in patients with type 2 diabetes are expected to closely relate to residual insulin secretory ability. We herein attempted to identify a reliable C-peptide immunoreactivity (CPR) index as an insulin secretory marker that would contribute to the selection of an appropriate insulin regimen for patients with type 2 diabetes. We near-normalized blood glucose in 246 obese patients with type 2 diabetes using our protocol (which included short-term intensive insulin therapy, IIT), and administered an oral hypoglycemic agent (OHA). Based on responsiveness to OHA, patients were classified into three therapy groups: non-insulin therapy ( n = 78), basal-insulin supported oral therapy (BOT) ( n = 109), and multiple daily insulin injection (MDI) therapy ( n = 59). Glucagon-loading CPR increment (ΔCPR), fasting CPR (FCPR), CPR2h after breakfast (CPR2h), ratio of FCPR to fasting plasma glucose (CPI), CPI2h after breakfast (CPI2h), and secretory unit of islets in transplantation (SUIT) were assessed with receiver operating characteristic (ROC) and multiple logistic analyses to discriminate the MDI group from the other therapy groups. ROC analysis revealed that CPR2h had the greatest area under the curve and specificity. Multiple logistic analysis identified CPR2h and CPI2h as the most significant explanatory variables for identifying patients assigned to the MDI group. A postprandial serum CPR marker such as CPR2h or CPI2h was shown to be the best index for predicting an appropriate insulin regimen to achieve good glycemic control in obese patients with type 2 diabetes.