Andersen ES, et al. - Researchers ascertained the association between plasma dipeptidyl-peptidase 4 (DPP-4) activity and its protection of glucagon-like peptide-1 (GLP-1) using the DPP-4 inhibitor sitagliptin. Results revealed that plasma DPP-4 activity decreased compared to baseline (placebo) with increasing doses of sitagliptin reaching a maximal inhibition with the 100 mg dose. The consequences of this study demonstrated that the sitagliptin dose of 100 mg was sufficient to inhibit both plasma and membrane-bound DPP-4 activity, probably also leading to complete protection of endogenous GLP-1 in patients with type 2 diabetes (T2D).