What is already known
The gut microbiota evolves throughout a person’s life. Infants have a distinct microbiota before weaning, which diversifies with solid food introduction, stabilizes in early adulthood, and declines in diversity after age 65. This evolving microbiota is linked to various conditions across life stages and can affect healthy aging.
What this research adds
The review highlights the factors that influence the gut microbiota and explores its association with health conditions across different life stages. In later years, a varied microbiota may produce anti-inflammatory compounds such as short-chain fatty acids, which have been linked to longevity. These observations hold true across diverse populations, suggesting they may represent hallmarks of healthy aging.
Conclusions
Understanding how gut microbes influence biological processes related to aging may inform interventions aimed at optimizing the microbiota to promote longevity.
The gut microbiota evolves throughout a person’s life. Infants have a distinct microbiota before weaning, which diversifies with solid food introduction, stabilizes in early adulthood, and declines in diversity after age 65. This evolving microbiota is linked to various conditions across life stages and can affect healthy aging.
In a review published in Gut Microbes, Evan Bradley and John Haran at UMass Chan Medical School in Worcester, Massachusetts, highlight the factors that influence the gut microbiota and explore its association with health conditions across different life stages.
The gut microbiota starts to develop before birth through exposure to maternal microbial metabolites. At birth, the mode of delivery can influence the initial transfer of gut microbes from the mother to her baby, with cesarean-born infants having an altered microbiota that has been linked to higher risk of asthma, type 1 diabetes and other autoimmune conditions.
Feeding mode can also shape an infant’s microbiota, with breastfed babies showing higher levels of beneficial bacteria such as Bifidobacterium. The introduction of solid foods and environmental factors such as siblings and pets affect microbiota composition, too. Studies have shown that antibiotic exposure and a poor diet can disrupt microbiota diversity, increasing susceptibility to inflammatory bowel disease.
The adult microbiota is typically stable, but diet and physical activity can alter its composition, with active individuals showing higher diversity and beneficial bacteria. Microbes such as Christensenellaceae and Faecalibacterium prausnitzii have been associated with good health and protection against obesity, type 2 diabetes and other conditions.
Older adults tend to have lower microbiota diversity and higher levels of Bacteroidetes compared to younger individuals. Healthy older adults often maintain a diverse microbiota similar to that of younger people, and microbes such as Akkermansia and Christensenellaceae have been associated with healthy aging.
Microbiota and inflammation
Changes in the aging microbiota affect biological processes through chronic low-level inflammation, which has been linked to cardiovascular disease, metabolic syndrome and chronic kidney disease. Inflammation can also promote the growth of bacteria such as Escherichia and Klebsiella, which may exacerbate inflammation.
Studies have revealed microbial signatures associated with inflammatory molecules and anti-inflammatory metabolites. For example, a decrease in bacteria that produce short-chain fatty acids has been linked to increased gut permeability and inflammation, and the abundance of Akkermansia has been tied to higher levels of inflammatory molecules in the blood.
Microbial metabolism of dietary molecules also affects the risk of developing age-related conditions, with certain metabolites associated with cognitive decline and cardiovascular disease.
Microbiota-gut-brain axis
The microbiota-gut-brain axis, which links the brain and gut bacteria, has been shown to play a role in neurodegenerative disorders. For example, Alzheimer’s disease is associated with differences in gut microbiota composition and infections that may trigger brain inflammation.
The connection between gut microbes and healthy aging suggests that the microbiota may be a target of therapeutic approaches, but clinical trials have yielded mixed results. Dietary interventions as well as probiotics and prebiotics have resulted in positive changes in biomarkers and microbial features, but their effects on conditions such as dementia appear to be limited.
Understanding how gut microbes influence biological processes related to aging may inform interventions aimed at optimizing the microbiota to promote longevity, the authors say.
