- John Crayon
- Conversation *
In 1895, on his 50th birthday, Eli Metnikov became increasingly concerned about old age.
As a result, the Nobel Prize-winning Russian scientist and co-founder of immunology shifted his focus from immunology to gerontology — the term.
He was fascinated by the role of intestinal bacteria in health and disease – suggesting that people in Eastern Europe lived longer by consuming various fermented foods containing lactic acid bacteria.
Although popular at the time, this theory of linking intestinal microbiota to healthy aging was ignored by scientists until relatively recently.
We now recognize the importance of the trillions of bacteria known as intestinal microbiota or microbiota playing a role in the control of health and disease.
For nearly a decade, evidence has been accumulating that the structure of the microbiome changes with age.
In 2012, in a research conducted by my colleagues at the University College Cork in Ireland, the diversity of microbiomes was linked to health problems, including the weakness of old age.
We still do not know much about the effect of microbiome on brain aging.
In 2017, we re-examined Metnikoff’s ideas, which were placed in the context of brain aging, and showed that aging causes changes in the microbiota and immune system, which are associated with cognitive decline and anxiety.
However, this study, like many others in this field, showed only a link between aging and these factors. It did not prove that one was responsible for the other.
In a subsequent study, we went one step further with a microbiotic-rich diet containing prebiotic insulin (a prebiotic given by beneficial bacteria in the gut) to reduce the effects of aging on the brains of middle-aged mice.
However, it is not yet clear whether microbiota itself causes brain aging to slow down.
In our latest study, we showed that taking microbioma from young mice and transplanting it into older mice could reverse many of the effects of aging on learning, memory, and immune deficiencies.
With a mice, we showed that transplanting fecal microbiota from young to older mice can cause older mice to quickly find a hidden platform.
Aging is associated with increased inflammation in all body systems, including the brain.
It is clear that immune processes play an important role in the aging of the brain, with more emphasis on the role of a particular immune cell, the microglia.
Ironically, by the end of the nineteenth century, it was the same cell that Mechnikov had visualized under a microscope, albeit in other tissues.
We now know that the activation of these cells is under the constant control of the intestinal microbiome.
Therefore, the next part of the puzzle was to see whether the adverse effects of aging on the immune system could be reversed by transplanting microbiota from mice to the elderly. In fact, most of the inflammation is reduced.
Finally, we showed that the chemicals in the brain area involved in the study and memory (hippocampus) were similar to those in young mice after microbiot transplantation.
Our results clearly show that microbiome is important for a healthy brain in old age.
Was it too early for Mechnikov to leave immunology to understand the secrets of old age?
In fact, the relative contribution of immune changes seen in mice receiving young microbiota to the overall regenerative effects deserves further study.
But two important questions remain. What are the exact mechanisms for playing? Can we humans translate these remarkable discoveries?
Rats are not human
Working in controlled conditions is very different from looking at humans, as in the case of mice with well-defined genetics, diet, and microbiome. We must be careful not to misinterpret these findings.
We do not recommend stool replacement for people who want to revitalize the brain.
Instead, these studies point to the future with a focus on microbiotic-targeted diets or bacterial-based therapies that promote better intestinal health and immunity to maintain brain youth and health. In fact, these tricks would be even more delicious nectar.
Mechnikov’s general principles seem to be correct: the protection of intestinal microbes may be the secret of the source of youth. With the advancement of health, longevity has increased significantly.
While we may not be able to prevent it over time, we can develop therapies that protect our brain from degeneration – and we have an unch ham that the microbiome can be a way out.
However, it still takes a lot of work to better understand how gut microbes can “rewind” certain features of the aging brain.
* John Crayon is Vice President of Research and Innovation at University College Cork, Ireland.
This article was originally published by the academic news site The Dialogue and republished here under a Creative Commons license. Read the original version here (In English).
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