Intestinal interoceptive dysfunction drives age-associated cognitive decline

Overview

This study investigates the mechanisms underlying age-associated cognitive decline by examining the relationship between intestinal interoceptive signalling and hippocampal function across the lifespan. The research identifies a microbiota-dependent pathway in which altered bacterial composition during ageing impairs vagal afferent neuron function, reducing interoceptive signal transmission to the brain and subsequently compromising memory encoding in the hippocampus. The work positions peripheral gastrointestinal signals as key mediators of age-related cognitive dysfunction and proposes that targeting this pathway may mitigate memory decline in aged organisms.

Methods and approach

High-resolution mapping of microbiome composition and function was performed across the lifespan of mice. The study employed integrated analyses to identify bacterial taxa and metabolic outputs associated with cognitive decline during ageing. Mechanistic investigations utilized signalling pathway analyses focusing on GPR84-mediated inflammation in peripheral myeloid cells and its consequences for vagal afferent neuron integrity. Functional validation involved assessment of hippocampal neuronal activation patterns and memory encoding capacity. Three intervention strategies were tested in aged mice: bacteriophage-mediated targeting of specific bacterial taxa, GPR84 inhibition, and restoration of vagal neural activity.

Key Findings

Accumulation of medium-chain fatty acid-producing bacteria, particularly Parabacteroides goldsteinii, occurs during ageing and drives GPR84-dependent inflammation in peripheral myeloid cells. This inflammatory state results in functional impairment of vagal afferent neurons, leading to diminished interoceptive signalling to the central nervous system. Consequently, hippocampal neuronal activation patterns are altered and memory encoding capacity is reduced. Pharmacological and biological interventions targeting this pathway—including phage therapy against Parabacteroides, GPR84 antagonism, and enhancement of vagal activity—restored memory function in aged mice, demonstrating the sufficiency of this mechanism for age-associated cognitive decline.

Implications

The findings establish interoceptive dysfunction as a central mechanism in brain ageing, shifting conceptual focus from purely neurointrinsic factors to peripheral signalling pathways as drivers of cognitive decline. The identification of specific bacterial taxa and receptor signalling cascades provides discrete molecular targets for intervention. These results suggest that pharmacological or biological approaches enhancing gut-brain interoceptive communication represent a viable strategy for counteracting age-associated memory decline. The heterogeneous manifestation of cognitive decline across individuals may reflect variation in this microbiota-dependent pathway.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.