Ferrannini and colleagues reported that GLP-1 secretion quickly reached the maximum level of GLP-1total in healthy Caucasians in a range of 25–30 pmol/L within 30 min after 75-g glucose oral mixed meal, compared with a Cmax of 10–12 pmol/L for T2D subjects with obesity11, although it was reported that the GLP-1 and GIP secretion in the GCK-MODY patients was not impaired in these subjects with non-obesity31,34. Here, GIP is linked to type 2 diabetes mellitus.