Why carry out this study?

Previous studies reported that β-cell function markers, such as fasting and meal-induced C-peptide levels, might be useful in estimating the efficacy of glucagon-like peptide-1 receptor agonists.

However, the following questions remain unanswered: Are these markers confounded by baseline glycemic control, and if so, what is the least confounded marker? What is the association between that marker and glycemic response to dulaglutide, a widely used glucagon-like peptide-1 receptor agonists?

We aimed to (i) investigate the confounding effect of baseline glycemic control on the β-cell function markers to determine the least confounded marker and (ii) investigate whether the β-cell function markers are associated with HbA1c-lowering effects of dulaglutide, exploring a suitable marker of glycemic response to dulaglutide.

What was learned from this study?

Meal-induced C-peptide levels (PCPR and ΔCPR) were significantly affected by baseline glycemic control, whereas fasting C-peptide (FCPR) was not, suggesting that FCPR was the marker least confounded by baseline glycemic control.

FCPR, PCPR, and ΔCPR were significantly associated with glycemic response to dulaglutide. Furthermore, FCPR was a significant predictor for achieving a reduction in HbA1c of at least 1%, suggesting its utility as a marker for glycemic response to dulaglutide in clinical settings.