RESUMEN
AIMS: The gold standard clamp measurements for insulin sensitivity (cSI), ß-cell function (cBCF) and disposition index (cDI = cSI*cBCF), are not practical in large-scale studies. We sought to: 1) validate a mathematical model-derived DI from oral glucose tolerance tests (OGTT) with insulin (mDI) and without (mDI-woI) against cDI and oral disposition index (oDI) evaluate the ability of the novel indices to detect prediabetes and type 2 diabetes. METHODS: We carried out a secondary analysis of previously reported cross-sectional observational studies. The Insulin Sensitivity and Secretion mathematical model for glucose-insulin dynamics was applied to five-point and three-point OGTTs synchronized with hyperinsulinemic-euglycemic and hyperglycemic clamps from 130 youth with obesity (68 NGT, 33 IGT, 29 T2D). RESULTS: Model-derived DI correlated well with clamp DI (R = 0.76 (logged)). Between NGT and IGT, mDI and mDI-woI decreased more than oDI and cDI, (60 and 59% vs 29 and 27%), and by receiver operating characteristic (ROC) analysis were superior at detecting IGT than oDI and cDI (AUC 0.88, 0.87 vs 0.68, 0.65), as was mean glucose (AUC 0.87). CONCLUSIONS: mDI-woI is better than oDI or the labor-intensive cDI for detecting dysglycemia in obese youth. Bypassing insulin measurements with mDI-woI from the OGTT provides a cost-effective approach for large-scale epidemiological studies of dysglycemia in youth.
RESUMEN
Efficient and accurate methods to estimate insulin sensitivity (SI) and ß-cell function (BCF) are of great importance for studying the pathogenesis and treatment effectiveness of type 2 diabetes (T2D). Existing methods range in sensitivity, input data, and technical requirements. Oral glucose tolerance tests (OGTTs) are preferred because they are simpler and more physiological than intravenous methods. However, current analytical methods for OGTT-derived SI and BCF also range in complexity; the oral minimal models require mathematical expertise for deconvolution and fitting differential equations, and simple algebraic surrogate indices (e.g., Matsuda index, insulinogenic index) may produce unphysiological values. We developed a new insulin secretion and sensitivity (ISS) model for clinical research that provides precise and accurate estimates of SI and BCF from a standard OGTT, focusing on effectiveness, ease of implementation, and pragmatism. This model was developed by fitting a pair of differential equations to glucose and insulin without need of deconvolution or C-peptide data. This model is derived from a published model for longitudinal simulation of T2D progression that represents glucose-insulin homeostasis, including postchallenge suppression of hepatic glucose production and first- and second-phase insulin secretion. The ISS model was evaluated in three diverse cohorts across the lifespan. The new model had a strong correlation with gold-standard estimates from intravenous glucose tolerance tests and insulin clamps. The ISS model has broad applicability among diverse populations because it balances performance, fidelity, and complexity to provide a reliable phenotype of T2D risk.NEW & NOTEWORTHY The pathogenesis of type 2 diabetes (T2D) is determined by a balance between insulin sensitivity (SI) and ß-cell function (BCF), which can be determined by gold standard direct measurements or estimated by fitting differential equation models to oral glucose tolerance tests (OGTTs). We propose and validate a new differential equation model that is simpler to use than current models and requires less data while maintaining good correlation and agreement with gold standards. Matlab and Python code is freely available.