Human exposure to bacteria is associated with dementia risk – and particularly to Alzheimer’s dementia, that is, for young people, with the disease among the most common causes of Alzheimer’s disease, accounting for up to one in three cases. The study, published back in March in PLoS Medicine, was led by Salk Professor Carolyn Stewart.
The study analyzed the genetic information from 7,558 people who participated in a long-term study called the Aging Brain Project. They were followed for 8 years. The participants were predominantly Caucasian and middle aged with a median age of 71 years.
In the analysis, total DNA methylation was measured at baseline and one-year follow-up. Researchers also directly measured the relative abundance of blood bacteria in the participants, as well as metabolite profiling, in order to measure the composition of the familial germline (which is, DNA methylation) as well as the genetic ancestry of each participant.
Researchers found that DNA methylation level was significantly associated with the amount of Alzheimer’s disease identification/diagnosis composite, which comprised almost 9% of the total genome DNA methylation. The ratio of the gene expression values associated with Alzheimer’s disease gene activity was also significantly associated. DNA methylation also correlated with the total Alzheimer’s disease RNA level during both the baseline and one-year follow-up periods, but did not significantly correlate with RNA levels or gene expression of Alzheimer’s disease DNA or proteins – Alzheimer’s disease biomarkers.
Lisa Shapiro, lead author and medical student in the aging brain research group at Salk, reports that testing of blood samples may aid the development of predictive biomarkers that could trigger detection of Alzheimer’s disease in affected people. “DNA methylation is thought to represent a potential biomarker for Alzheimer’s disease that can predict outcome of enzyme 1 (AN2) processing in patients, in a non-methylated brain blood sample,” she says, adding that further investigation is needed in more detail.
In the meantime, Dendritic System Specificity, presumed due to DNA methylation, was connected to Alzheimer’s disease biomarkers. “ADHD may involve different brain regions, including cognition, than Alzheimer’s disease, and our results show a number of associations between AD/ADL1 methylation and Alzheimer’s disease biomarkers,” the scientists say. “It is possible that recognition of Alzheimer’s disease brain tissues due to genetic alteration presents a uniquely powerful method for identifying Alzheimer’s disease biomarkers in early symptomatic individuals and can be considered an important clinical concept to guide future prevention work in clinical populations.”