The mRNA expression of TCA cycle genes in AD patients was systematically revealed by brain and peripheral blood cells transcriptome data, and combined with MMSE, Aβ/Tau correlation analysis to confirm that SUCLA2, MDH1, and PDHB genes may be candidate biomarkers that can effectively track the pathological and clinical manifestations of AD patients (Figure 5A). The gene discussed is MDH1; the disease is Alzheimer disease.