CXCL12 and type 2 diabetes mellitus: The involvement of DPP-4 in metabolism of endogenous SDF-1α is compatible with the finding that the truncated metabolite, SDF-1α 3-67, was present in wild-type mice, but not in animals lacking DPP-4 (62), with this observation being extended in subsequent studies in mice and Rhesus monkeys (63) and in patients with T2DM (64) showing that levels of SDF-1α 3-67 were reduced while those of the intact 1-67 form increased concomitantly when DPP-4 activity was inhibited.