Comparison of Islet Function in People With Different Glucose Metabolic States

Type 2 Diabetes Mellitus (T2DM) is closely associated with impaired islet β-cell function. Multiple indicators can be used to evaluate islet function and insulin resistance. The aim of this study is to establish a β-cell function assessment model based on oral glucose tolerance test (OGTT) indices, providing a reference for the early diagnosis and treatment of diabetes.

In this study, 30 Normal Glucose Tolerance (NGT), 43 Impaired Glucose Regulation (IGR), and 42 T2DM subjects were enrolled. The levels of blood glucose, insulin, c-peptide, and proinsulin were measured during OGTT. Insulinogenic index (IGI), C-Peptide generation Index (CPI), and proinsulinogenic index (PNI) were calculated. Fasting-state ratios, including c-peptide to glucose (CP/I), proinsulin to insulin (PI/I), and proinsulin to c-peptide (PI/CP), were calculated. The area under the curve (AUC) was analyzed for these indices and their corresponding ratios. ROC curve analysis was performed to evaluate the diagnostic value of these indicators for glucose metabolism disorders and β-cell function.

In the fasting state, CP/I gradually increased, while IGI and PNI gradually decreased from the NGT group to the IGR and T2DM groups. For diagnosing IGR, the AUCs of CP/I, IGI, and PNI were 0.8101, 0.762, and 0.7605; for T2DM, they were 0.8746, 0.9651, and 0.8451; and for distinguishing IGR from T2DM, they were 0.7054, 0.8200, and 0.6833, respectively.

Different indicators have different diagnostic capabilities for IGR and T2DM. The comparison of various indicators reveals pancreatic islet function across different glucose-metabolizing populations.

CP/I, IGI, and PNI were more sensitive in reflecting impaired glucose tolerance. CP/I can reflect insulin clearance capacity, and IGI can reflect β-cell dysfunction.