ApoE ε4 and IL-6-174G/C Polymorphism may Lead to Early Onset of Alzheimer's Disease with Atypical Presentation

Abstract

Background: Alzheimer's disease (AD) is the most common cause of dementia. Although genetic mutations are known in rare familial form, exact cause of neurodegeneration in sporadic AD is still unknown. While ApoE ε4 and IL-6 C-174G/C patterns have been found to increase the risk of AD in Caucasians, the results are inconsistent in other ethnic groups. Objective: The aim of this study was to evaluate the effect of ApoE and IL-6-174G/C polymorphisms among patients of AD in the Eastern part of India. Materials and Methods: Consecutive patients of probable AD diagnosed as per National Institute on Aging-Alzheimer's Association (NIA-AA) criteria with age, gender, and education-matched healthy controls were recruited between December 2015 and September 2018. Patients were clinically evaluated and along with controls were genotyped for ApoE and IL-6-174G/C polymorphisms by the polymerase chain reaction method. Results: A total 115 patients and 162 controls showed a similar pattern of ApoE and IL-6-174G/C polymorphism pattern. While ε3ε3 and GG patterns were the commonest, followed by ε3ε4 and GC pattern in ApoE and IL-6 respectively, the effect of ApoE ε4 and IL-6-174 C allele on AD symptoms could not be established. However, patients with onset before 50 years were found to have significantly higher proportion of ApoE ε4 and C allele of IL-6-174 in comparison to patients with onset above 50. These young patients were also having more atypical presentation than their older counterpart. Conclusion: Our study revealed a novel role of both ApoE ε4 and C allele of IL-6-174 together in developing early onset AD with more atypical clinical features.