Our gut is home to billions of bacteria, collectively known as the gut microbiome. While it's safe to say that these living organisms are important to us, it is still not known what a healthy gut microbiome should look like and how it changes over time.
The results of the new work, available at BioRxiv.org, complement a host of other studies that suggest that the human gut may serve as a biological clock that can accurately determine biological age.
We know that the human gut adapts and changes in several stages, but researchers have not yet been able to determine whether the gut microbiome of the average adult progresses or remains unchanged throughout life. It would certainly make sense if the aging process led to gradual changes in the gut, but until now, any age predictions based on this information have been rather unclear. For example, the previous model was only 10-15 percent better at determining the age of the intestinal flora than a completely random guess. The new method is much more accurate, scientists say.
To find out how the microbiome changes over time, researchers at InSilico Medicine studied 3,663 gut bacteria samples from 1,165 healthy people between the ages of 20 and 90. About a third of the data came from the age group from 20 to 39 years old, a third from the age group from 40 to 59 years old, and another third from the age group from 60 to 90 years old. The team applied a neural network on 90 percent of this data to see if this type of machine learning could ultimately predict the donor's age. Upon completion of training, the algorithm was tested. When the program was asked to predict the ages of the remaining 10 percent, it was able to pinpoint someone's age with a margin of error of only four years. In addition, of the 95 species studied, the algorithm also identified 39 intestinal bacteria species that were most important in predicting age.
Oddly enough, a person's age was not related to the amount of harmful or beneficial bacteria present in the intestines. For example, campylobacteriosis, a gastrointestinal infection commonly caused by C. jejuni, is known to be more likely to affect children, while older adults are more likely to have this problem.
“Older people are less likely to have these bacteria because they are more likely to retain the memory of previous exposure to C. jejuni - either in their immune system or in their microbiota - and can effectively prevent its spread. Meanwhile, young people have not yet developed a means of countering C. Jejuni, so it is more common at this age,”the authors explain in their article.
Further research on certain 39 types of bacteria is needed to better understand the aging process in humans and its relationship to the gut microbiome, the researchers said. The authors hope that if their method is validated, it could help create a more accurate picture of a person's true biological age during their lifetime, possibly leading to advances in personalized medicine.