OCA2 and Alzheimer disease: According to the detection of serum SIRT1, IL-6, T-tau, P-tau-181, and Aβ1-42 proteins, the results showed that in the NC, MCI, and AD groups, the serum SIRT1 protein levels were down-regulated successively, and they were (2.90±2.01), (1.29±0.21), and (1.06±0.471) ng/μL, respectively.