INS and type 2 diabetes mellitus: GLP-1 participates in the stimulation of postprandial insulin release in lean subjects [20], but this incretin response is impaired among subsets of populations of patients with T2D, with some meta-analyses finding an unaltered GLP-1 release [27] and other studies revealing reduced [28] or even increased [29] concentrations of GLP-1 in patients with T2D.