DPP4 and diabetes mellitus: Previous studies in rodents have shown that molecules, including angiotensin II (AngII), dipeptidyl peptidase-4 (DPP4), and semaphorin3E, are suppressed with vaccines targeting these molecules, thus ameliorating the pathogenesis of hypertension or diabetes (Nakagami et al, 2013; Pang et al, 2014; Yoshida et al, 2019).