Similarly, the CP serum concentrations reached their peak levels at 30 min after the start of the OGTT in the NGT group, at 120 min in the T2DM group and after 60 min in the IGR group (Fig. 1b), with the areas under the curves (AUC0–180) being 1593, 2015 and 1083 in the NTG, IGR and T2DM groups, respectively. Here, CP is linked to type 2 diabetes mellitus.