SUIT, secretory units of islets in transplantation: An index for therapeutic management of islet transplanted patients and its application to type 2 diabetes

Evaluation of a patient's pancreatic β-cell function is important in both diagnosis and treatment of diabetes. We sought to determine β-cell function with a single sampling of blood. Examination of fasting blood glucose (F-BG, mM) and C-peptide (F-CPR, nM) levels in seven post-islet-transplanted states of four patients revealed a linear relationship between F-BG and F-CPR. Assuming that normal subjects aged <40 years have 100% pancreatic β-cell function, we developed the secretory units of islets in transplantation (SUIT) as an index of β-cell function by the formula: 250 × F-CPR/(F-BG − 3.43). The SUIT index was correlated with the stimulated C-peptide levels not only in islet-transplanted patients (R2 = 0.68, P < 0.05) but also in type 2 patients (R2 = 0.34, P < 0.001). Since the SUIT index can be calculated from data obtained at a single fasting blood sampling and predict the pancreatic β-cell function, the formula may be a useful tool in clinical management of diabetes.