Sodium oligomannate disrupts the adherence of Ribhigh bacteria to gut epithelia to block SAA-triggered Th1 inflammation in 5XFAD transgenic mouse

Sodium oligomannate (GV-971), an oligosaccharide drug approved in China for treating mild-to-moderate Alzheimer's disease (AD), was previously found to recondition the gut microbiota and limit altered peripheral Th1 immunity in AD transgenic mice. As a follow-up study, we here provide advances by pinpointing a Lactobacillus murinus strain that highly expressed a gene encoding a putative adhesin containing Rib repeats (Ribhigh-L.m.) that was particularly enriched in 5XFAD transgenic mice. Mechanistically, Ribhigh-L.m. adherence to the gut epithelia upregulated fecal metabolites, among which lactate ranked as the top candidate. Lactate stimulated the epithelial production of serum amyloid A (SAA) in gut via GPR81-NFκB axis, contributing to peripheral Th1 activation. Moreover, GV-971 disrupted the adherence of Ribhigh-L.m. to gut epithelia via directly binding to Rib, leading to the reduced SAA and alleviated Th1-skewed inflammation. These findings were replicated in early-staged AD patients. Together, we gained further insights between gut bacteria and AD progression and the mechanism of GV-971 in treating AD. Intrabacterial whole RNA sequencing from each purified lactobacillus murinus bacteria strains isolated from the fecal samples of 41-week-age WT and Tg mice in 5XFAD Alzheimer's disease models