On the other hand, research on DPP-4 inhibitors also demonstrated its neuroprotective effects via SIRT1 activation in diabetes, improving angiogenesis, mitochondrial function, and NO bioavailability while suppressing oxidative stress, abnormal proliferation, and migration of BMECs under HG, ischemia, and even psychological stress [80,92,205]. The gene discussed is SIRT1; the disease is diabetes mellitus.