The effects of age, apolipoprotein E phenotype and gender on the concentration of amyloid-β (Aβ) 40, Aβ42, apolipoprotein E and transthyretin in human cerebrospinal fluid

Objective: To test whether the concentrations of amyloid-β (Aβ)40, Aβ42, apolipoprotein E (apoE) and transthyretin in the CSF of normal individuals, are linked to three factors which modulate the risk of Alzheimer’s disease (AD): chronological age, gender, and the presence of the apoE4 allele. Methods and results: Proteins were measured by enzyme-linked immunosorbent assays except for transthyretin, which was assayed by radial immunodiffusion. The apoE phenotype was determined by isoelectric focusing. While the CSF levels of Aβ42, apoE, and transthyretin are reported to be reduced in AD, we found no relationship between age, gender, or apoE phenotype and the level of any of these proteins in the CSF of nondemented individuals. The concentration of Aβ40 was not modulated by gender or apoE phenotype, but did decline significantly with age. Conclusion: These results indicate that the changes observed in the CSF of AD patients are specific to the disease itself rather than the known risk factors.