Similarities in Pathobiology of Alzheimer’s Disease and Type 2 Diabetes Mellitus: A Proof of Concept by a Case Study

Abstract Background Alzheimer’s disease (AD) is the leading cause of dementia worldwide. Developing countries will have >3 times the prevalence of the developed countries by the year 2050. Our previous studies with a Pakistani population have suggested that type 2 diabetes mellitus (T2DM) is strongly associated with impaired cognitive functioning, and genetic pathways showed strong resemblance to known AD patterns. The present case studies investigated two important pathways, i.e., Amyloid Precursor Protein (APP) processing and Lipid Metabolism, using gene expression profiling arrays to compare and contrast AD and T2DM patients from Pakistan. Method We performed high‐throughput qRT‐PCR with preconfigured a TaqMan Low Density Profiling Array specific to Human Alzheimer’s Disease (ABI, CAT # 441887) to measure the altered gene expressions and their corresponding pathways (Ingenuity Pathway Analysis, IPA®). Both the T2DM (n = 2; M/F each) and AD (n = 2, M/F each) patients (cases) were recruited from outpatient departments of a regional hospital, and were compared with their respective matched, healthy controls. Result Overall, we observed a differential gene expression profile in AD and T2DM participants compared to controls. CYP46A1, MAPT, CAPNS1, GAL, AGER, CAPN1, PSENEN, ST6GAL1, GRIN2B, GRIN2C, GRIN2A, and GAP43 was downregulated in both T2DM and AD patients. ACHE, CHRM3, GRIN2C and GAP43 significantly (p value <0.05) downregulated in all T2DM patients. CDC2, UCHL1, CTSG, CASP3, IDE, NAE1, CDK5R1, IL6, APBB2, GLS are the top 10 common genes that were upregulated in both AD and T2DM groups. The IPA analysis revealed important Canonical Pathways, that included, viz., Amyloid Processing, Neuroinflammation Signaling, ErB4 Signaling, nNOs Signaling. Molecular Mechanisms of Cancer. The top disease and biofunctions included Metabolic Disease, Neurological disease, Organismal Injury and Abnormalities, Psychological Disorders, Cardiovascular Disease, with the top upstream regulators PHLPP2, IL33, APP, CRP, TAC1. Conclusion The differential gene expression patterns and associated disease pathways from this pilot study suggest that specific genes and pathways were common to both diseases and may suggest common underlying processes and causes. Information from such biochemical and genetic studies will be crucial to the development of therapeutic targets to treat AD.