DPP4 and diabetes mellitus: In a retrospective cohort study with more than 100,000 patients with diabetes, individuals treated with dipeptidyl peptidase 4 (DPP4) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists alone or in combination had a significantly lower risk of developing PD compared to patients with diabetes treated with other antidiabetics than DPP4 inhibitors, GLP-1 agonists or glitazones [54].