Association of Clusterin (CLU) Gene Polymorphism, Rs11136000, with Alzheimer's Disease and Diabetes in the Turkish Population

Purpose: Alzheimer's disease (AD), the most common form of dementia, is characterized by abnormal protein storage in the brain and primarily causes a progressive loss of memory and all other cognitive functions. According to the World Health Organization (WHO) report, AD is steadily increasing among people 65 years of age and over. Genome wide association studies have shown that various gene polymorphisms are highly associated with the occurrence of AD. Among them, clusterin (CLU) gene polymorphism was identified as one of the highest genetic risks in late-onset AD. Our aim was to investigate the relation of CLU rs11136000 and AD and its potential use as a biomarker for AD susceptibility in the Turkish population. Methods: 50 samples obtained from AD patients and 55 samples obtained from a control group were used for the presented study. Genomic DNA was isolated from peripheral blood by SDS/proteinase K treatment followed by phenol-chloroform extraction and ethanol precipitation. Presence of the CLU rs11136000 polymorphism was investigated by PCR-RFLP and selected samples were confirmed by DNA sequencing. Chi-square test was used for statistical analysis. Results: In the Turkish population, the CLU rs11136000 polymorphism did not show a significant association with AD as compared with the control group (p>0.05). Polymorphic CLU-C allele of AD patients showed an increased association with diabetes (p=0.015) as compared with CLU-T allele of AD patients, whereas in the control group the CLU-C allele did not show a significant association with diabetes (p=0.332). Conclusion: Individuals with diabetes and polymorphic CLU-C allele may have a higher susceptibility to develop AD later in life.