Gut Bacteria Profile Remains Stable With Healthy Aging

Liam Davenport

October 25, 2017

Very healthy centenarians have a gut microbiome almost identical to that seen in people aged 30 years of age, suggesting that healthy aging could be related to maintaining a healthy intestinal environment, say Canadian and Chinese researchers.

The study of over 1000 very healthy Chinese individuals showed that the microbial environment in the gut was strikingly similar in infancy, in adulthood, and in old age, with the microbiota essentially unchanged after 30 years of age.

The research was published online recently in the journal mSphere by Gaorui Bian of Tianyi Health Sciences Institute, Zhenjiang, Jiangsu, China, and colleagues.

"The main conclusion is that if you are ridiculously healthy and 90 years old, your gut microbiota is not that different from a healthy 30-year-old in the same population," second author Greg Gloor, PhD, a professor at the Schulich School of Medicine & Dentistry, Western University, London, Ontario, commented in a press release.

He added: "This demonstrates that maintaining diversity of your gut as you age is a biomarker of healthy aging, just like low-cholesterol is a biomarker of a healthy circulatory system."

What Comes First: Health or Healthy Gut Microbiota?

Coauthor Gregor Reid, PhD, also a professor at Western's Schulich School of Medicine & Dentistry, said that by examining the gut microbiota of healthy people, the team hopes that they can provide a baseline so that clinicians know what they "are striving for when people get sick."

Another aim of the study was to "bring novel microbiome diagnostic systems to populations, then use food and probiotics to try to improve biomarkers of health."

Dr Reid said: "It raises the question: if you can stay active and eat well, will you age better, or is healthy aging predicated by the bacteria in your gut?"

It is generally accepted that the diversity of the gut microbiome declines with increasing age. However, contradictory findings have been reported, and it is noteworthy that the comparison groups and how the aged population has been defined have varied between studies.

Building on previous research indicating that the species-level compositional profile of the microbiota could discriminate between individuals based on their ethnicities, geography, and lifestyles (ISME J. 2015;9:1979–1990), the researchers conducted a large-scale gene sequencing analysis of microbiota composition.

They collected fecal samples from 1095 Chinese individuals aged between 3 and 100 years, of whom 533 were female and 212 were young soldiers, and performed DNA isolation and sequencing on the samples.

All the participants were defined as being very healthy, in that they were nonsmokers and nondrinkers, had a stable mood and no diseases, took no prescription medications, had taken no antibiotics in the past 3 months, and had no personal or family disease history.

For those aged ≤ 31 years, individuals were included if, in addition to the above criteria, their parents and grandparents were all alive or had passed away after 80 years of age.

More Variance in Gut Microbiota in 19- to 24-Year-Olds and in Males vs Females

"Our analysis showed several surprising results compared with other cohorts," the researchers say.

One of these was the fact that the gut microbiota of persons in their 20s was distinct from those of other age cohorts, and this was true across a range of 19- to 24-year-olds, including the samples obtained from the young soldiers.

"This suggests that a change in lifestyle (eg, leaving home for university or jobs) or physiology (eg, levels of sex steroid hormones) in the postteen years is an important determinant of the observed gut microbiota," they note.

But there were few interindividual differences between the ages of 30 and > 100 years, and the overall microbiota composition of the healthy aged group was therefore similar "to that of people decades younger."

Looking at individual species, the researchers found that bacteria from the Bifidobacterium genus were relatively enriched in the youngest groups and relatively depleted in the oldest groups.

This contrasted with the results for the Dorea, Clostridium insertae sedis (IS) and sensu strictu 1 (SS1), Marvinbryantia, and, to a lesser extent, Prevotella genera, which were relatively enriched in samples from older individuals.

Overall, there were seven distinct bacterial clusters, which varied in abundance across different age groups.

The researchers also found that there was more variance in gut microbiota in males than in females, with the principal component of the gut microbiota explaining 11.3% of the variance in female-only samples but 19.4% of the variance in males.

The team concludes: "The results suggest that if you live to be 100 and in perfect health in China, your microbiota will likely appear to be relatively similar to that from a person in their mid-30s."

"Whether this is cause or effect is unknown, but it suggests that resetting an elderly microbiota to that of a 30-year-old might help promote health, if the microbiota is outside the norm."

The collection, sequencing, and initial analysis were supported by grants from the following: Zhenjiang Tianyi Biotech, Human Microbiome Project; International Science and Technology Cooperation Program and Jinshan Excellence Projects; and Social Development of Science and Technology Support Projects and Science and Technology Assistance Projects. Development of the compositional data analysis approach was supported by a NSERC Discovery grant to Dr Gloor. Dr Bian is employed by Tianyi Health Sciences Institute (THSI), a private, not-for-profit entity. Dr Gloor and Dr Reid are members of the scientific advisory board of THSI. Disclosures for the coauthors are listed in the paper.

mSphere. 2017;2:e00327-17. Article

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