Differential Associations of APOEɛ2 and APOEɛ4 Genotypes with Cerebrospinal Fluid Biomarkers of Alzheimer's Disease in Individuals Without Dementia.

BACKGROUND: The APOE genotype has emerged as the major genetic factor for AD but differs among different alleles. OBJECTIVE: To investigate the discrepant effects of APOE genotype on AD cerebrospinal fluid (CSF) biomarkers. METHODS: A total of 989 non-demented ADNI participants were included. The associations of APOEɛ2 and APOEɛ4 with CSF biomarkers were investigated using linear regression models. Interaction and subgroup analyses were used to investigate the effects of sex and age on these associations. Furthermore, we used mediation analyses to assess whether Aß mediated the associations between APOE genotypes and tau. RESULTS: APOEɛ2 carriers only showed higher Aß levels (ß [95% CI] = 0.07 [0.01, 0.13], p = 0.026). Conversely, APOEɛ4 carriers exhibited lower Aß concentration (ß [95% CI] = -0.27 [-0.31, -0.24], p < 0.001), higher t-Tau (ß [95% CI] = 0.25 [0.08, 0.18], p < 0.001) and higher p-Tau (ß [95% CI] = 0.31 [0.25, 0.37], p < 0.001). Subgroup analysis showed that APOE ɛ2 was significantly positively associated with Aß only in females (ß [95% CI] = 0.12 [0.04, 0.21], p = 0.005) and older people (ß [95% CI] = 0.06 [0.001, 0.12], p = 0.048). But the effects of APOE ɛ4 were independent of gender and age. Besides, the associations of APOE ɛ4 with t-Tau and p-Tau were both mediated by baseline Aß. CONCLUSIONS: Our data suggested that APOEɛ2 could promote Aß clearance, while the process could be modified by sex and age. However, APOEɛ4 might cause the accumulation of Aß and tau pathology independent of sex and age.