Bacteria keep us healthy – but could they keep us young? | Horizon: the magazine of research and innovation of the EU

This is part of an area of ​​research that examines the link between intestinal bacteria and aging to help people live healthier lives with seniors. The proportion of the EU population aged 80 or over is expected to more than double between 2017 and 2080, with people aged 65 and over rising from 20 to almost 30%.

However, the link between microbiota composition in the gut, brain function and aging is unclear – the causes and effects are difficult to establish.

Dr. Damien Rei, a postdoctoral researcher in neurodegenerative and psychiatric diseases at the Institut Pasteur in France, decided to examine the different types of microbiome that appear in increasingly younger and older mice, in order to better understand what could also happen in humans.

He found that when he was transferring intestinal bacteria in elderly mice to young adult mice, there was a powerful effect on the reduction of learning and memory. And when the opposite was done, with older mice receiving the microbiota from younger mice, their cognitive abilities returned to normal. The oldest mice were about one and a half years old, which is about 60 years old and up.

"Although they were older animals, their learning abilities were almost identical to those of adult mice after the transfer of the microbiota," said Dr. Rei, adding that this indicates strong communication between the intestines and the brain. "When I saw the data, I could not believe it, I had to repeat the experience at least twice."

Moreover, by seeing what was happening in the neuronal communication pathways between the intestine and the brain when the aged microbiota was transferred to the youngest mice, they were then able to manipulate these pathways. By doing this, he says that they could block or mimic the effects of the old microbiota.

Dr. Rei's study, a Microbiota and Aging project, has not yet been published, but he hopes this can be done by the end of the summer. . He is also interested in the gut microbiota in the elderly and with Alzheimer's disease, but says it is too early to reveal more details about this research.

Translating

However, Dr. Rei pointed out that it was very difficult to translate the results in mice into people, not only because of important ethical barriers, but also differences in physiology. "The immune system of a mouse is very different from that of a human. The gut microbiota is also very different, because mice eat things very different from what we do, "he said.

Research is still a long way from actually using this type of research to combat neurodegenerative diseases such as Alzheimer's disease, says Dr. Rei. Indeed, he says, there is no convincing evidence for the moment that one should look at the gut microbiota. But he thinks that the mouse study opens the door for further investigation into the mechanisms behind age-related changes.

"The mice data really was the first springboard and allowed us to understand the potential for manipulation of the gut microbiota," said Dr. Rei.

According to Dr. Thorsten Brach, a postdoctoral researcher at the University of Copenhagen in Denmark, it is not easy to pin down the link between intestinal bacteria and aging.

"We know that aging is a multifactorial process and that it is difficult, especially with respect to the microbiome, to separate the effects of aging from all other aspects," he said.

He worked on a project called Gut-InflammAge, which focused on the link between intestinal microbes, inflammation and aging, led by Associate Professor Manimozhiyan Arumugam.

As part of their work, the team investigated the effects of mild and periodic dietary restriction in mice to examine the potential impact of a healthy, aging diet involving fasting. Unexpectedly, the low-calorie mice accumulated more body fat – which the researchers assumed had eaten too much between these periods – but also observed a slight rejuvenation of their blood profile which brought them closer to that of the younger mice.

The researchers observed a difference between the composition of the microbiota in the different groups, but in the study, the differences found were not large enough to suggest a more healthy variability from one individual to another. Therefore, the study confirms that diet and lifestyle are more important than age and gender to shape the microbiota, said the researchers, although Professor Arumugam said it would be more revealing to track changes in the microbiome of individuals over time.

Studies to date indicate that much remains to be done to provide a clear picture of the link between the microbiota and the aging process. Professor Arumugam also pointed out that microbiome analysis is lagging technologically in relation to genetic research, since the causes and effects of the disease are more difficult to establish than genes.

But research is gradually improving our understanding. Professor Arumugam stated that, although his team's study did not result in a "breakthrough", it provided a better understanding of this area and raised questions from previous assumptions.

And research in this field could ultimately change our vision of aging, says Dr. Rei, considering it as more fluid than just "one-way without going back, except in movies like Benjamin Button".

The research in this article was funded by the EU. If you liked this article, consider sharing it on social networks.