RESUMO
The relationship between major depression (MD) and dementia in the elderly is still not clear, but it is certain that the immune system and in particular, pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, play a key role in the mechanisms underlying the two neuro-psychiatric disorders. In our experience, the -308(G/A) single nucleotide polymorphism (SNP) in the TNF-alpha gene is associated with earlier age at onset in patients affected by Alzheimer's disease (AD). The aim of this study was to investigate the association between the -308(G/A) SNP and late-life MD in elderly people without dementia. Blood samples were obtained from 50 subjects, after screening with the geriatric depression scale (GDS>or=15) and mini-mental state examination (MMSE>or=24). The -308 (G/A) SNP was genotyped by SSP-PCR amplification. Two-hundred-fourty age-matched healthy volunteers were taken as the control group. We identified different genotype and allele distributions of the SNP in old depressed patients and healthy controls (HC). Our results evidenced a significantly higher percentage of the GG genotype in depressed subjects (84.0% vs. 68.3%; p=0.007) and consequently of the G allele (92.0% vs. 81.9%; p=0.05). The presence of the GG genotype raised the risk of developing MD (odds ratio=OR=2.433, confidence interval=Cl=1.09-5.43). Our findings suggested that the investigated TNF-alpha SNP may: (1) affect MD susceptibility; (2) be involved both in AD and MD development, but probably with a distinct role in the two pathologies.
