The microbiome is the organisms living in the gut, these can be good and bad. Typically the gut contains mostly healthy bacteria and immune cells which help to ward off infections and diseases. Although the gut is known to be a vital component of the body’s immune system, its importance in the aging process is more unclear. Recently, researchers at the Institute for Systems Biology have shown that the microbiome continues to evolve, but only among healthy people.
“Prior results in microbiome-aging research appear inconsistent, with some reports showing a decline in core gut genera in centenarian populations, while others show relative stability of the microbiome up until the onset of aging-related declines in health,” says co-author Dr. Sean Gibbons. “Our work, which is the first to incorporate a detailed analysis of health and survival, may resolve these inconsistencies. Specifically, we show two distinct aging trajectories. One, a decline in core microbes and an accompanying rise in uniqueness in healthier individuals, consistent with prior results in community-dwelling centenarians, and two, the maintenance of core microbes in less healthy individuals.”
In this study, the gut microbiome of 9,000 people between the ages of 18-101 years old was analyzed, in particular tracking the survival rates for a cohort of 900 participants ages 78-98 years old. Results showed that the microbiome became increasingly unique with age, and core bacteria Bacteroides common to all humans started to decline in mid to late adulthood.
“Interestingly, this uniqueness pattern appears to start in mid-life — 40 to 50 years old — and is associated with a clear blood metabolomic signature, suggesting that these microbiome changes may not simply be diagnostic of healthy aging, but that they may also contribute directly to health as we age,” says study co-author Dr. Tomasz Wilmanski. “For example, indoles are known to reduce inflammation in the gut, and chronic inflammation is thought to be a major driver in the progression of aging-related morbidities.”
A healthy microbiome was found to continue to share common traits despite its increasing uniqueness, and those with unique gut patterns also had different metabolites in their blood plasma, including tryptophan-derived indole which has been shown to extend longevity in animal studies. Phenylacetylglutamine metabolites had previously been found in large quantities in the blood of centenarians, but this unique transformation only took place among healthy individuals, according to the researchers.
“This uniqueness signature can predict patient survival in the latest decades of life,” says Dr. Tomasz Wilmanski. “Healthy individuals around 80 years of age showed continued microbial drift toward a unique compositional state, but this drift was absent in less healthy individuals.”
“This is exciting work that we think will have major clinical implications for monitoring and modifying gut microbiome health throughout a person’s life,” co-author Dr. Nathan Price adds.
