Mixed-meal tolerance test to assess residual beta-cell secretion: Beyond the area-under-curve of plasma C-peptide concentration

Abstract

Aims: Residual beta-cell secretion in type 1 diabetes is commonly assessed by area-under-curve of plasma C-peptide concentration (AUC Cpep ) following mixed-meal tolerance test (MMTT). We aimed to investigate alternative measures of beta-cell responsiveness. Methods: We analyzed data from 32 youth (age 7 to 17 years) undergoing MMTT within 6 months of type 1 diabetes diagnosis. We related AUC Cpep with (a) validated mechanistic index of postprandial beta-cell responsiveness M I accounting for glucose level during MMTT, and (b) pragmatic marker calculated as baseline plasma C-peptide concentration corrected for baseline plasma glucose concentration. Results: Postprandial responsiveness M I was correlated with age and BMI SDS (R s = 0.66 and 0.44, P < 0.01 and P < 0.05) and was more correlated with glycated hemoglobin than AUC Cpep (R s = 0.79, P = 0.04). The pragmatic marker was highly correlated with AUC Cpep (R s = 0.94, P < 0.01). Conclusions: Postprandial responsiveness M I may be more relevant to glucose control than AUC Cpep . Baseline C-peptide corrected for baseline glucose appears to be a suitable surrogate of AUC Cpep if MMTT is not performed.