Homocysteine, apolipoproteine E and methylenetetrahydrofolate reductase in Alzheimer's disease and mild cognitive impairment

• <i>Background:</i> Alzheimer’s disease (AD) is the most common dementia disorder in elderly people. Currently, the only known genetic factor associated with the development of sporadic AD is the apolipoprotein E (ApoE) 4 allele. There is a need to identify other environmental and genetic risk factors that could modulate the risk of developing sporadic AD. <i>Objective:</i> To analyse the correlation between the ApoE and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and plasma homocysteine levels and vitamins (B₁₂ and folic acid) concentrations in serum from patients with AD and mild cognitive impairment (MCI) as compared with control group. <i>Methods:</i> The study was carried out in 99 AD patients, 98 subjects with MCI and 100 healthy subjects. Diagnosis of probable AD was made according to the NINCDS-ADRDA and DSM-IV criteria. The following factors were analysed: age, gender, duration of disease, concentration of plasma total homocysteine, folic acid and vitamin B₁₂ in the serum and the polymorphism of MTHRF and ApoE genes. The results obtained were analysed by multivariate analysis of regression. <i>Results:</i> We found that plasma total homocysteine is increased in AD patients (p < 0.0001) and depended on the MTHFR T/T genotype in the presence of low folate levels (p < 0.05). The increased frequency of ApoE4 allele in the AD population was independent of homocysteine, folic acid and vitamin B₁₂ levels and MTHFR status. <i>Conclusions:</i> We conclude that the concentration of plasma total homocysteine is increased in AD patients. This may be associated with the T/T genotype in the MTHFR gene; however, the distribution of the MTHRF C677T polymorphism in the Polish population does not differ in AD and controls.

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