GLP1R and type 2 diabetes mellitus: In addition, the lack of acute effect on insulin secretion in our study may be due to the decreased sensitivity of the beta cells to incretin hormones in T2D, as shown by Højberg et al.57 In that study, no increase in insulin release following intravenous infusion of GLP-1 and GIP (resulting in physiological plasma concentrations), respectively, was observed.