In the search for eternal youth, poo transplants may seem like an unlikely way to reverse the aging process.
However, scientists at the Quadram Institute and the University of East Anglia have provided evidence, from research in mice, that transplanting fecal microbiota from young into old mice can reverse hallmarks of aging in the gut, eyes, and brain.
In
the reverse experiment, microbes from aged mice induced inflammation in
the brain of young recipients and depleted a key protein required for
normal vision.
These
findings show that gut microbes play a role in the regulating some of
the detrimental effects of aging and open up the possibility of gut
microbe-based therapies to combat decline in later life.
Prof
Simon Carding, from UEA's Norwich Medical School and head of the Gut
Microbes and Health Research Program at the Quadram Institute, said:
"This ground-breaking study provides tantalizing evidence for the direct
involvement of gut microbes in aging and the functional decline of
brain function and vision and offers a potential solution in the form of
gut microbe replacement therapy."
It has been known for some time that the population of microbes that we carry around in our gut, collectively called the gut microbiota,
is linked to health. Most diseases are associated with changes in the
types and behavior of bacteria, viruses, fungi and other microbes in an
individual's gut.
Some
of these changes in microbiota composition happen as we age, adversely
affecting metabolism and immunity, and this has been associated with
age-related disorders including inflammatory bowel diseases, along with
cardiovascular, autoimmune, metabolic and neurodegenerative disorders.
To
better understand the effects of these changes in the microbiota in old
age, scientists from the Quadram Institute transferred the gut microbes from
aged mice into healthy young mice, and vice versa. They then looked at
how this affected inflammatory hallmarks of aging in the gut, brain and
eye, which suffer from declining function in later life.
The study, published in the journal Microbiome,
found that the microbiota from old donors led to loss of integrity of
the lining of the gut, allowing bacterial products to cross into the
circulation, which results in triggering the immune system and inflammation in the brain and eyes.
Age-related
chronic inflammation, known as inflammaging, has been associated with
the activation of specific immune cells found in brain. These cells were
also over-activated in the young mice who received aged microbiome
transplants.
In
the eye, the team also found specific proteins associated with retinal
degeneration were elevated in the young mice receiving microbiota from
old donors.
In
old mice, these detrimental changes in the gut, eye and brain could be
reversed by transplanting the gut microbiota from young mice.
In
ongoing studies, the team are now working to understand how long these
positive effects can last, and to identify the beneficial components of
the young donor microbiota and how they impact on organs distant from
the gut.
The
microbiota of young mice, and the old mice who received young
microbiota transplants were enriched in beneficial bacteria that have
previously been associated with good health in both mice and humans.
The
researchers have also analyzed the products which these bacteria
produce by breaking down elements of our diet. This has uncovered
significant shifts in particular lipids (fats) and vitamin metabolism,
which may be linked to the changes seen in inflammatory cells in the eye
and brain.
Similar
pathways exist in humans, and the human gut microbiota also changes
significantly in later life, but the researchers caution about
extrapolating their results directly to humans until similar studies in
elderly humans can be performed.
A
new facility for Microbiota Replacement Therapy (MRT), also known as
Fecal Microbiota Transplantation (FMT) is being built in the Quadram
Institute that will facilitate such trials, as well as other trials for
microbiota-related conditions.
Lead
author of the study, Dr. Aimee Parker from the Quadram Institute said:
"We were excited to find that by changing the gut microbiota of elderly
individuals, we could rescue indicators of age-associated decline
commonly seen in degenerative conditions of the eye and brain.
"Our
results provide more evidence of the important links between microbes
in the gut and healthy aging of tissues and organs around the body. We
hope that our findings will contribute ultimately to understanding how
we can manipulate our diet and our gut bacteria to maximize good health
in later life."
"Fecal
microbiota transfer between young and aged mice reverses hallmarks of
the aging gut, eye, and brain" is published in the journal Microbiome.
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