RESUMO
Previous studies in dementia epidemiology have reported higher Alzheimer's disease rates in African-Americans when compared with White Americans. To determine whether genetically determined African ancestry is associated with neuropathological changes commonly associated with dementia, we analyzed a population-based brain bank in the highly admixed city of São Paulo, Brazil. African ancestry was estimated through the use of previously described ancestry-informative markers. Risk of presence of neuritic plaques, neurofibrillary tangles, small vessel disease, brain infarcts and Lewy bodies in subjects with significant African ancestry versus those without was determined. Results were adjusted for multiple environmental risk factors, demographic variables and apolipoprotein E genotype. African ancestry was inversely correlated with neuritic plaques (P=0.03). Subjects with significant African ancestry (n=112, 55.4%) showed lower prevalence of neuritic plaques in the univariate analysis (odds ratio (OR) 0.72, 95% confidence interval (CI) 0.55-0.95, P=0.01) and when adjusted for age, sex, APOE genotype and environmental risk factors (OR 0.43, 95% CI 0.21-0.89, P=0.02). There were no significant differences for the presence of other neuropathological alterations. We show for the first time, using genetically determined ancestry, that African ancestry may be highly protective of Alzheimer's disease neuropathology, functioning through either genetic variants or unknown environmental factors. Epidemiological studies correlating African-American race/ethnicity with increased Alzheimer's disease rates should not be interpreted as surrogates of genetic ancestry or considered to represent African-derived populations from the developing nations such as Brazil.
Assuntos
Doença de Alzheimer , População Negra/genética , Doenças do Sistema Nervoso/etiologia , Doenças do Sistema Nervoso/genética , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/complicações , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Apolipoproteínas E/genética , Infarto Encefálico/etiologia , Infarto Encefálico/genética , Brasil/epidemiologia , Brasil/etnologia , Feminino , Interação Gene-Ambiente , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Emaranhados Neurofibrilares/patologia , Razão de Chances , Placa Amiloide/patologia , Estudos Retrospectivos , Fatores de Risco , Estatísticas não ParamétricasRESUMO
As expected by its global prevalence, the most frequently isolated species of yeast from vaginal swabs obtained from patients in Africa was Candida albicans, which accounted for 53 of 85 (62.4%) of the isolates from women in Madagascar and 35 of 54 (64.8%) of the culture-positive women in Angola. However, 40% of the Madagascan and 23% of the isolates from Angola, as well as two isolates obtained from one German patient, were not able to utilize the amino sugars glucosamine and N-acetylglucosamine as the sole carbon source. These isolates were able to form germ tubes but did not form chlamydospores. The correct identification as C. albicans was made possible only by using a PCR-based method of DNA fingerprinting. Only minor phenotypic and genotypic variation was observed among these strains. Whether they represent a distinct clone that is found mainly in Africa is not clear. The relevance of the amino sugar catabolic pathway in C. albicans is discussed in view of these results.