Effect of apolipoprotein E genotype on magnetic resonance spectrum in amnestic mild cognitive impairment and Alzheimer's disease patients

Abstract

Objective: To explore the relationship between apolipoprotein E (ApoE) gene polymorphism and hydrogen proton magnetic resonance spectroscopy ((1)H-MRS) in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment(aMCI). Methods: The cognitive function of 35 AD patients (AD group), 35 aMCI patients (aMCI group) and 36 normal controls (NC group) were evaluated by neuropsychological scales, including Mini-mental State Examination (MMSE) and Cambridge Cognitive Examination-Chinese version (CAMCOG-C). The genotypes of ApoE were analyzed by high-resolution melting assay. Brain regional metabolites were measured via (1)H-MRS technique with the regions of interest (ROIs) located in the left frontal lobe and left hippocampus. Results: The CAMCOG-C (NC group 94.00 (8.50);aMCI group 86.00(8.00);AD group 61.00(18.0)) and MMSE (NC group 29.00 (2.00);aMCI group 26.00(2.00);AD group 13.00(9.5)) scores in AD and aMCI group were significantly lower in comparison with that in NC group (P<0.05). There was multi-domain cognitive impairment both in AD and aMCI. The CAMCOG-C (ε4 carriers 76.00(28.00);no-ε4 carriers 89.00 (17.00)) and MMSE (ε4 carriers 23.00(16.00);no-ε4 carriers (27.00 (6.00))scores in ε4 carriers were significantly lower than those in no-ε4 carriers (P<0.05). The AD and aMCI groups showed decreased NAA/Cr ratio in the left hippocampus as well as elevated Cho/Cr ratio and MI/Cr in the left frontal lobe compared to the NC group (P<0.05). This change was even more pronounced in AD group when compared to aMCI group. The NAA/Cr ratio and Cho/Cr ratio in the left hippocampus in ε4 carriers were lower, the MI/Cr ratio in left frontal lobe in ε4 carriers was higher (P<0.05). Conclusions: ApoE gene polymorphism affects the alteration of (1)H-MRS in AD and aMCI patients. The combination of ApoE gene polymorphism and (1)H-MRS may be more useful to differentiate and diagnose AD and aMCI early.