Relation of plasma homocysteine to plasma amyloid beta levels

Abstract

Background: Elevated plasma homocysteine and amyloid beta (Abeta) have been associated with Alzheimer's disease (AD). We investigated the cross-sectional association between these biomarkers.

Methods: We used linear regression to relate plasma homocysteine and Abeta adjusting for age, gender, creatinine, APOE-epsilon4, and ethnic group in 327 persons aged 78 +/- 6.6 years.

Results: Plasma homocysteine correlated with age, serum creatinine, plasma Abeta40 and Abeta42, and was inversely correlated with serum vitamin B12, and folate. Abeta42, but not Abeta40, was related to later development of dementia. Homocysteine was related to higher Abeta40 levels (coefficient = 2.0; P < 0.0001) and this association was attenuated after adjustment for creatinine (coefficient = 1.0; P < 0.0001). The crude association between homocysteine and Abeta42 was weaker (coefficient = 0.5; P = 0.01) and became non-significant after adjustment for creatinine (coefficient = 0.4; P = 0.06). These associations were unrelated to ethnicity, the presence of APOE-epsilon4 or dementia. Analyses by quartiles of homocysteine showed that these association were driven primarily by the fourth quartile.

Conclusions: Plasma homocysteine is directly related to Abeta40. The association with Abeta42 is not significant. These results seem to indicate that homocysteine is related to aging but not specifically to AD.