High resolution mouse study shows a gut microbe can promote memory loss

Amazing stuff!

"... In a study published today in Nature, scientists show how a bacterium that is particularly common in older animals can drive memory loss. This microbe makes compounds that impair signaling along neurons connecting the gut with the brain, dampening activity in brain regions associated with learning and memory, the team found. ...

Research on the so-called gut-brain axis has exploded in recent decades. Multiple studies have identified differences in microbiome composition between healthy people and those with cognitive disorders such as Alzheimer’s disease. This kind of research can’t establish cause and effect, though, and the literature is rife with conflicting results. ..."

From the abstract:

"Ageing is accompanied by declining memory function, with extremely heterogeneous manifestation in the human population.

Brain-extrinsic factors influencing cognitive decline, such as gastrointestinal signals, have emerged as attractive targets for peripheral interventions, but the underlying mechanisms remain largely unclear.

Here, by charting a high-resolution map of microbiome ageing and its functional consequences throughout the lifespan of mice, we identify a mechanism by which inhibition of gut–brain signalling during ageing results in impaired neuronal activation in the hippocampus and loss of memory encoding. Specifically, accumulation of gut bacteria that produce medium-chain fatty acids, such as Parabacteroides goldsteinii, can drive peripheral myeloid cell inflammation through GPR84 signalling. As a result, the function of vagal afferent neurons is impaired, the interoceptive signal received by the brain is weakened and hippocampal function declines.

We leverage this pathway to define interventions that enhance memory in aged mice, such as phage targeting of Parabacteroides, GPR84 inhibition and restoration of vagal activity. These findings indicate a key role for interoceptive dysfunction in brain ageing and suggest that interoceptomimetics that stimulate gut–brain communication may counteract age-associated cognitive decline."

‘Tour de force’ mouse study shows a gut microbe can promote memory loss | Science | AAAS "Research suggests the microbiome may contribute to cognitive decline—but its relevance in humans is unclear"

Intestinal interoceptive dysfunction drives age-associated cognitive decline (open access)

Fig. 1: Microbiome impact on age-associated cognitive decline.