Research Review

As we age, our intestinal microbiomes become less complex. The assumption is that something about getting older affects almost all bodily functions, and the gut is no exception. 

British researchers from Norwich University wanted to see if manipulating the intestinal microbiota influences the development of conditions associated with aging—particularly inflammation affecting the brain and retina. They hypothesized that the microbiome composition isn’t a passive consequence of aging but rather the cause of some of its significant features. 

The researchers tested their hypothesis with an experiment that exchanged the intestinal microbiota of mice through fecal transplants at various ages—young (3 months), old (18 months), and older (24 months).  Next, the researchers sequenced the DNA of the transplanted feces to ensure that it resembled the original products. Finally, they used protein studies, microscopic analysis, and mouse behavioural testing to observe the effects of age and the fecal transfer on the brain and retina.

The results showed microbiota composition could successfully be “swapped” between young and aged. Also, the transfer of aged microbiota into young mice sped up age-associated inflammation of the central nervous system and retina, resulting in the loss of key functional proteins in the brain and eye.  Conversely, these damaging effects were reversed by exchanging the young microbiota with the old. 

These findings confirmed the hypothesis that the aging gut microbiota drives detrimental changes in the gut-brain and gut–retina axes. The results suggest modulating the aging microbiota might prevent inflammation-related tissue decline in later life. 

However,  the old mice who received young feces didn’t improve their ability to navigate a maze (the behavioural test), but the young mice who received old feces did more poorly. While impossible to prove from this study, one explanation could be that we can’t easily reverse fixed structural changes associated with age-related inflammation (called inflammageing) with a fresh metabolic profile. 

We are all aging (believe it or not), and presumably, our intestinal microbiomes are aging with us. If our microbiomes are not just the consequence of aging but rather contribute to chronic disease predisposition, it is reasonable to assume that something can be done about it. Like shoes, one size won’t likely fit all. Because each of us is unique, we all may need different microbiome “tune-ups” at one point. i-Forget is the first step on a discovery journey which may make simple microbiome interventions commonplace. 

Reference:

Parker, A., Romano, S., Ansorge, R. et al. Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain. Microbiome 10, 68 (2022). https://doi.org/10.1186/s40168-022-01243-w (Accessed: November 18, 2024)