An Aging Microbiome, Cognitive Decline and the Promise of Fecal Transplant

This is definitely the biggest biome buzz of the week:

An international team of researchers just published a study on aging and the microbiome.  Some articles covering it are calling it the fountain of youth:  fecal transplant is showing promise for treating cognitive decline due to aging.  I’ve talked many times on this blog about how we know that the gut flora plays a role in aging.  See here and here as just two examples of many.  We know that aging leads to a “…loss of functional capacity in several body systems…and is often associated with a decline in psychological well-being and cognitive function.”[i]  Because of the bidirectional communication between the gut and the brain, it’s believed that as the gut bacteria age, they adversely affect the central nervous system.

Even a “modest” alteration in the composition of the gut microbiota via dietary alterations or antibiotics is known to cause changes in mouse brain chemistry and function.  Continually mounting research shows that the bacterial microbiome affects the development of the central nervous system, as well as is ongoing function, learning, and memory.  Too boot, you all know how alterations to the microbiome are now associated with the development of neurodegenerative diseases including Alzheimer’s, depression, autism, Parkinson’s and multiple sclerosis.

Says one of the lead researchers in this study, “”Aging is an inevitable process that starts immediately after birth and ultimately leads to physical health problems as well as a decline in psychological well-being and cognitive function.  Research has shown that the aging process may be linked with age-related changes in our gut microbiota.”[ii]

The researchers performed fecal transplants from old mice to young adult ones and then assessed anxiety, exploratory behavior and memory in the young mice.  The first two categories remained unaffected, as did locomotor activity; however, spatial learning and memory were noticeably affected.  These changes paralleled changed in the expression of particular proteins that are associated with neurotransmission and synaptic plasticity (learning), and changes to the cells in the hippocampus, which is the part of the brain responsible for learning and memory.  In other words, the young mice began to act like old mice in terms of their cognitive function.

Changes to the microbiomes of the young mice included, for example, lower levels of Lachnospiraceae and Ruminococcaceae that are producers of short chain fatty acids (SCFA) and lower levels of SCFAs were indeed found in the treated young mice.  A decrease in Ruminococcaceae has already been associated with Alzheimer’s disease.

Unfortunately,  in this particular experiment, they did not do the reverse:  transfer feces from the young mice to the older one to see if cognitive decline could be reversed.  Says another one of the researchers involve, “While it remains to be seen whether transplantation from very young donors can restore cognitive function in aged recipients, the findings demonstrate that age-related shifts in the gut microbiome can alter components of the central nervous system.”

They conclude, that their experiment, “…provides a solid support to the hypothesis  that microbe-based approaches that aim to restore a  young-like microbiota might improve cognitive function  and in so doing the quality of life of the elderly, an ever increasing  demographic segment of modern societies.”  I can’t imagine it will take many more years before tailored probiotics become available – ones for athletic performance, ones to treat specific diseases, one to reverse aging, and more become available.  As we are all getting older, that’s a pretty appealing thought!

Here’s a link to a video summary of this research:  https://youtu.be/bMaF-k99Kvk

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[i] Alfonsina D’Amato, Lorenzo Di Cesare Mannelli, Elena Lucarini, Angela L. Man, Gwenaelle Le Gall, Jacopo J. V. Branca, Carla Ghelardini, Amedeo Amedei, Eugenio Bertelli, Mari Regoli, Alessandra Pacini, Giulia Luciani, Pasquale Gallina, Annalisa Altera, Arjan Narbad, Massimo Gulisano, Lesley Hoyles, David Vauzour, Claudio Nicoletti. Faecal microbiota transplant from aged donor mice affects spatial learning and memory via modulating hippocampal synaptic plasticity- and neurotransmission-related proteins in young recipients. Microbiome, 2020; 8 (1) DOI: 10.1186/s40168-020-00914-w

[ii] https://www.sciencedaily.com/releases/2020/10/2010020910