Association Serum S100B Protein in Alzheimer’s Disease: A Case Control Study from South India

Background: Recent evidence points to a possible link between the inflammatory modulatory protein S100B protein and the pathogenesis of Alzheimer’s disease (AD). Objective: To investigate the elevated levels of serum S100B protein among AD in a South Indian cohort and its correlation with severity of cognitive impairment. Methods: A cross-sectional study was conducted with 100 AD patients and 100 age and sex matched healthy controls. Diagnosis of AD was made by a qualified neurologist using NINCDS ADRDA criteria. Measurement of serum S100B protein was performed using solid phase sandwich ELISA method in both cases and controls. Results: Significantly higher prevalence of elevated serum S100B protein 44(44%) (p<0.0001), hypertension 52(52%) (p=0.02), diabetes mellitus 58(58%) (p=0.002), thyroid dysfunction 28(28%) (p=0.009), positive CRP 46(46%) (p<0.0001) and lower mean Mini-Mental State Examination (MMSE) values 20.4±5.1 (p<0.0001) were seen in AD patients compared to controls. Elevated S100B protein levels were significantly associated with Clinical dementia rating (CDR) score 2(34%) (p=0,05) and score 3 (61.3%) (p=0.03) compared to normal levels. After multivariable logistic regression analysis positive C-Reactive Protein (odds: 3.2; 95%CI: 2.8-9.8)(p=0.001), elevated S100B protein (odds: 9.0;95%CI:2.2-35.8) and diabetes mellitus (odd:1.2;95%CI:1.0-4.9)(p<0.0001), were significantly associated with AD. Conclusion: In our study, we established an independent association of elevated serum S100B protein levels with AD. Elevated S100B protein levels higher in CDR score 3.