High-fat Diet and Age Disrupt a Muribaculaceae-associated SCFA Network Linked to Gut Barrier and Cognitive Deficits.

Both diet and aging shape the gut microbiota, yet how their combined remodeling propagates across microbial function to host barrier and brain outcomes remains poorly understood. Despite abundant links between Short-chain fatty acids (SCFAs) and intestinal health, integrative studies that connect community ecology with SCFA linked metabolism, epithelial signaling, systemic inflammation, behavior, and test causal reversibility are limited. In this study, we assessed gut microbiota and function alongside host tissues and behavior. In mice fed a high-fat diet (HFD), particularly in the 12-month-old cohort, we observed hippocampal-dependent cognitive and locomotor deficits (longer escape latency, fewer platform crossings, reduced target-quadrant time; lower distance, speed and center time), accompanied by systemic inflammation, with serum lipopolysaccharide (LPS) and cytokines (IL-6 and TNF-α) elevated and associated with adiposity. We then profiled the gut microbiota and its functions alongside host tissues and behavior, finding that HFD and age reduced α-diversity and shifted β-diversity, with a selective depletion of Muribaculaceae and depressed SCFA-linked pathways. Muribaculaceae abundance positively correlated with predicted SCFA-related pathways, while qRT-PCR of microbial fermentation genes supported concurrent functional alterations. In the colon, ELISA-measured butyrate level, SCFA receptors Ffar2, Ffar3 and tight-junction genes Tjp1 and Ocln were downregulated, with ZO-1 and occludin mislocalization, while serum LPS and inflammatory cytokines increased and associated with adiposity. Notably, an intervention arm showed that sodium butyrate supplementation attenuated cytokinemia, restored Ffar2, Ffar3 and tight-junction expression, improved ZO-1 and occludin integrity, and rescued behavioral performance. Collectively, these findings support an association between Muribaculaceae depletion, reduced SCFA-related functional signatures, impaired barrier associated markers, systemic inflammation, and behavioral deficits under HFD and age-associated conditions. In an intervention setting, butyrate supplementation partially ameliorated inflammatory and barrier-related readouts and improved behavioral performance.