Can intestinal bacteria fight old age?

Over the decades, Science has established links between the gut microbiota and old age. A recent study reveals microbiome transplants in mice. The goal ? Mitigate the effects of age on the brain.

The microbiota linked to cognitive decline

Ilya Ilyich Metchnikov (1845-1916) was a zoologist, bacteriologist and immunologist during the Russian Empire. In 1895, he had suggested that some populations in Eastern Europe were living longer for a particular reason. These feed on a large amount of fermented foods, including lactic acid bacteria. This is therefore a theory associating intestinal microbes with healthy aging.

Largely ignored for decades, this idea gradually resurfaced. Today, Science recognizes the importance of the gut microbiota in the regulation of health and disease. Studies have shown that the diversity of bacteria can have health consequences as we age. Others believe that age implies changes in the microbiota and the immune system. In other words, the microbiota could be associated with cognitive decline.

Some studies even assume that a diet specific to the billions of microbes present in our intestines could reduce the effects of aging in the brain. A study led by neurologist John Cryan of University College Cork and published in the journal Nature Aging on August 9, 2021 goes one step further.

Roles of the gut microbiota.
Credit: Salsero35 / Wikipedia

Human microbiota transplants?

John Cryan’s team says they transplanted the microbiome of young mice into older specimens. By examining these, the researchers found that it was possible to reverse many of the effects of old age on learning, as well as memory. The results show that the chemicals present in the hippocampus were closer than those in young mice after transplantation. In conclusion, the microbiome is essential for the health of the brain, especially when the subject has reached a certain age.

This last study therefore seems to validate the principles of Ilya Ilitch Metchnikov. He thought that staying young went through the protection of intestinal bacteria. However, since the tests have been carried out in mice, can the theory in question really apply to humans? Further studies obviously need to be carried out, particularly with regard to the ability of intestinal bacteria to combat certain characteristics of cerebral aging.

Finally, this type of work does not allow us to hope for faecal transplants in humans to rejuvenate the brain. On the other hand, research could lead to the development of food (or bacterial) treatments for the microbiota. The goal? To promote the optimization of intestinal health and immunity in order to keep a brain in good shape.

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