A novel exopolysaccharide from Lactiplantibacillus plantarum H6 improves cholesterol metabolism via Muribaculum-mediated activation of the enterohepatic FXR-FGF15 axis.

EPS-D1 is a novel exopolysaccharide with a molecular weight of 15.003 kDa composed primarily of mannose and glucose with a highly branched structure.

• EPS-D1 was isolated and characterized from Lactiplantibacillus plantarum H6.
• Monosaccharide composition consists primarily of mannose (46.10%) and glucose (33.98%).
• EPS-D1 features a branching degree of 29.5%, indicating a highly branched structure.

Administration of EPS-D1 significantly reduced serum lipid levels in high-cholesterol diet mice.

• Serum total cholesterol (TC) was reduced by 40.31% in high-cholesterol diet (HCD) mice.
• Serum triglycerides (TG) were reduced by 37.55% in HCD mice.
• Serum low-density lipoprotein cholesterol (LDL-C) was reduced by 43.15% in HCD mice.
• EPS-D1 administration also improved hepatic steatosis and reduced markers of liver injury.

Muribaculum was identified as the key commensal bacterium enriched by EPS-D1 treatment.

• Muribaculum enrichment was identified through 16S rRNA sequencing.
• Fecal microbiota transplantation (FMT) was used to confirm that Muribaculum was the key mediator of EPS-D1's cholesterol-lowering effects.
• Direct administration of Muribaculum intestinale replicated the cholesterol-lowering effects observed with EPS-D1.

Direct administration of Muribaculum intestinale decreased ileal and fecal cholesterol levels substantially.

• M. intestinale administration decreased ileal cholesterol levels by 74.79%.
• M. intestinale administration decreased fecal cholesterol levels by 53.16%.
• These effects replicated the cholesterol-lowering properties observed with EPS-D1 treatment.

Both EPS-D1 and M. intestinale activated the enterohepatic FXR-FGF15 axis to modulate cholesterol metabolism.

• Activation of the FXR-FGF15 axis resulted in upregulation of hepatic cholesterol 7α-hydroxylase (CYP7A1) expression, promoting bile acid synthesis.
• Activation of the FXR-FGF15 axis resulted in downregulation of ileal ASBT and NPC1L1, thereby inhibiting cholesterol absorption.
• Both EPS-D1 and M. intestinale independently activated this enterohepatic signaling axis.

M. intestinale increased intestinal short-chain fatty acids and modulated the bile acid pool composition.

• M. intestinale increased intestinal short-chain fatty acids (SCFAs) by 37.88%.
• The increases were particularly noted for acetic acid and caproic acid.
• M. intestinale also modulated the composition of the bile acid pool.
• These metabolic changes are proposed as part of the mechanism by which M. intestinale mediates cholesterol-lowering effects.

Hypercholesterolemia treatments such as statins are limited by hepatotoxicity and patient intolerance, motivating investigation of probiotic-based approaches.

• Hypercholesterolemia is described as a major risk factor for atherosclerotic cardiovascular disease.
• Current therapeutic options including statins are limited by hepatotoxicity and patient intolerance.
• Probiotics and their metabolites show promise in modulating cholesterol metabolism through the gut-liver axis.
• The specific commensal bacteria and molecular mechanisms underlying probiotic effects on cholesterol remained poorly understood prior to this study.