title: Shared genetic etiology underlying Alzheimer's disease and type 2 diabetes.
abstract: Epidemiological evidence supports the observation that subjects with type 2 diabetes (T2D) are at higher risk to develop Alzheimer's disease (AD). However, whether and how these two conditions are causally linked is unknown. Possible mechanisms include shared genetic risk factors, which were investigated in this study based on recent genome wide association study (GWAS) findings. In order to achieve our goal, we retrieved single nucleotide polymorphisms (SNPs) associated with T2D and AD from large-scale GWAS meta-analysis consortia and tested for overlap among the T2D- and AD-associated SNPs at various p-value thresholds. We then explored the function of the shared T2D/AD GWAS SNPs by leveraging expressional quantitative trait loci, pathways, gene ontology data, and co-expression networks. We found 927 SNPs associated with both AD and T2D with p-value ≤0.01, an overlap significantly larger than random chance (overlapping p-value of 6.93E-28). Among these, 395 of the shared GWAS SNPs have the same risk allele for AD and T2D, suggesting common pathogenic mechanisms underlying the development of both AD and T2D. Genes influenced by shared T2D/AD SNPs with the same risk allele were first identified using a SNP annotation variation (ANNOVAR) software, followed by using Association Protein-Protein Link Evaluator (DAPPLE) software to identify additional proteins that are known to physically interact with the ANNOVAR gene annotations. We found that gene annotations from ANNOVAR and DAPPLE significantly enriched specific KEGG pathways pertaining to immune responses, cell signaling and neuronal plasticity, cellular processes in which abnormalities are known to contribute to both T2D and AD pathogenesis. Thus, our observation suggests that among T2D subjects with common genetic predispositions (e.g., SNPs with consistent risk alleles for T2D and AD), dysregulation of these pathogenic pathways could contribute to the elevated risks for AD in subjects. Interestingly, we found that 532 of the shared T2D/AD GWAS SNPs had divergent risk alleles in the two diseases. For individual shared T2D/AD SNPs with divergent alleles, one of the allelic forms may contribute to one of the diseases (e.g., T2D), but not necessarily to the other (e.g., AD), or vice versa. Collectively, our GWAS studies tentatively support the epidemiological observation of disease concordance between T2D and AD. Moreover, the studies provide the much needed information for the design of future novel therapeutic approaches, for a subpopulation of T2D subjects with genetic disposition to AD, that could benefit T2D and reduce the risk for subsequent development of AD.
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Hao
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Antonio Fabio
authors.initials: AF
authors.lastname: Di Narzo
authors.affiliation: Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Lap
authors.initials: L
authors.lastname: Ho
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; College of Computer Science and Technology, Huaqiao University, No.668 Jimei Avenue, Xiamen 361021, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Luo
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Chen
authors.affiliation: AccuraScience, LLC, 5721 Merle Hay Road, Johnston, IA, USA.
authors.forename: Tongbin
authors.initials: T
authors.lastname: Li
authors.affiliation: Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Dubner
authors.affiliation: Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA; Geriatric Research, Education and Clinical Center (GRECC), James J. Peters Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, USA. Electronic address: giulio.pasinetti@mssm.edu.
authors.forename: Giulio Maria
authors.initials: GM
authors.lastname: Pasinetti
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D020022:Genetic Predisposition to Disease; D055106:Genome-Wide Association Study; D006801:Humans; D020641:Polymorphism, Single Nucleotide
keywords: Alzheimer's disease; GWAS; Pathway; Shared genomic component; Type 2 diabetes; eQTLs