RESUMEN
PURPOSE: Abnormal glucagon concentrations are a feature of prediabetes but it is uncertain if α-cell dysfunction contributes to a longitudinal decline in ß-cell function. We therefore sought to determine if a decline in ß-cell function is associated with a higher nadir glucagon in the postprandial period or with higher fasting glucagon. METHODS: This was a longitudinal study in which 73 non-diabetic subjects were studied on 2 occasions 6.6⯱â¯0.3â¯years apart using a 2-hour, 7-sample oral glucose tolerance test. Disposition Index (DI) was calculated using the oral minimal model applied to the measurements of glucose, insulin, C-peptide concentrations during the studies. We subsequently examined the relationship of glucagon concentrations at baseline with change in DI (used as a measure of ß-cell function) after adjusting for changes in weight and the baseline value of DI. RESULTS: After adjusting for covariates, nadir postprandial glucagon concentrations were not associated with changes in ß-cell function as quantified by DI. On the other hand, fasting glucagon concentrations during the baseline study were inversely correlated with longitudinal changes in DI. CONCLUSIONS: Defects in α-cell function, manifest as elevated fasting glucagon, are associated with a subsequent decline in ß-cell function. It remains to be ascertained if abnormal α-cell function contributes directly to loss of ß-cell secretory capacity in the pathogenesis of type 2 diabetes.