Apolipoprotein E genotype modulates effects of vitamin B12 and homocysteine on grey matter volume in Alzheimer's disease

The aim of the present study was to investigate whether the effects of vitamin B12 and homocysteine on brain volume are influenced by apolipoprotein E (APOE) genotype. We examined the effects in each subgroup (APOE ε4 carriers and non-carriers) of Alzheimer's disease (AD) patients and healthy normal controls.Forty participants with AD and 20 healthy normal controls were recruited from memory impairment clinics at Pusan National University Hospital in Korea. All participants were APOE genotyped and underwent magnetic resonance imaging, including 3-D volumetric images for grey matter (GM) volume. A multiple regression model integrated into statistical parametric mapping was used to see if there was any correlation between vitamin B12 or homocysteine and GM volume in each subgroup (APOE ε4 carriers and non-carriers) of AD patients and healthy normal controls.There was a significant positive correlation between serum concentrations of vitamin B12 and regional GM volume in APOE ε4 carriers with AD but not in non-carriers. We also found that there was a significant negative correlation between serum concentrations of homocysteine and regional GM volume in APOE ε4 non-carriers with AD but not in carriers (P0.001, uncorrected for multiple comparisons; extent threshold = 100 voxel).The present findings suggest that the effects of vitamin B12 and homocysteine on GM volume might be influenced by APOE genotype.