Potential contribution of the Alzheimer's disease risk locus BIN1 to episodic memory performance in cognitively normal Type 2 diabetes elderly

In recent years, several promising susceptibility loci for late-onset Alzheimer's disease (AD) were discovered, by implementing genome-wide association studies (GWAS) approach. Recent GWAS meta-analysis has demonstrated the association of 19 loci (in addition to the APOE locus) with AD in the European ancestry population at genome-wide significance level. Since Type 2 Diabetes (T2D) is a substantial risk factor for cognitive decline and dementia, the 19 single nucleotide polymorphisms (SNPs) that represent the 19 AD loci were studied for association with performance in episodic memory, a primary cognitive domain affected by AD, in a sample of 848 cognitively normal elderly Israeli Jewish T2D patients. We found a suggestive association of SNP rs6733839, located near the bridging integrator 1 (BIN1) gene, with this phenotype. Controlling for demographic (age, sex, education, disease duration and ancestry) covariates, carriers of two copies of the AD risk allele T (TT genotype) performed significantly worse (p=0.00576; p=0.00127 among Ashkenazi origin sub-sample) in episodic memory compared to carriers of the C allele (CT+CC genotypes). When including additional potential covariates (clinical and APOE genotype), results remained significant (p=0.00769; p=0.00148 among Ashkenazi). Interestingly, as validated in multiple large studies, BIN1 is one of the most established AD risk loci, with a high odds ratio. Although preliminary and require further replications, our findings support a contribution of BIN1 to individual differences in episodic memory performance among T2D patients.