Microbiota and Aging. A Review and Commentary

Although there is a consensus that the dominant species that make up the adult microbiota remains unchanged in elderly people, it has been reported that there are significant alterations in the proportion and composition of the different taxa, leading to reduced microbiota diversity, as well as an increase of enteropathogens that may lead to chronic inflammation. The ageing of mucosal immune and motor systems also contributes to these changes. As the individual ages, there is a loss in the number of Peyer's patches, an altered local capacity of T and B cell functions as well as chronic macrophage activation. Also, environment, diet, place of residence and biogeography are regulatory factors of the microbiota. Communication in the gut-brain-axis is regulated by many intermediaries including diverse metabolites of the microbiota. Microbial changes have been observed in several geriatric diseases, like Parkinson's and Alzheimer's. In addition, evidence has shown that individuals with high frailty scores had a significant reduction on lactobacilli species when compared to non-frail individuals. Oral microbiota may be also especially important because of the opportunities for access to the brain through the olfactory nerve at the roof of the nose or through the abundant innervations of the oral cavity by the trigeminal and other cranial nerves. Also, there are an increasing number of reports that have suggested potential mechanisms by which the microbiota promote human health span and aging. The study of the microbiota represents an important advance in the understanding of the aging process.