Structure-function relationship of Konjac glucomannan with varying acetylation degrees in modulating gut microbiota and alleviating prediabetes.

Acetylation and deacetylation of KGM altered the degree of substitution (DS) while preserving the KGM backbone, accompanied by changes in molecular weight and viscosity.

• Structural characterisation confirmed that chemical modifications changed DS without disrupting the core glucomannan backbone structure.
• Both acetylation and deacetylation processes resulted in changes to molecular weight and viscosity of the resulting AcKGM variants.
• Multiple AcKGM preparations with varying DS were successfully generated for comparative experiments.

In vitro fermentation of AcKGM using feces from prediabetic individuals enriched Bacteroides uniformis and Bacteroides coprocola, with enrichment positively correlating with DS.

• In vitro fermentation experiments were conducted using faecal samples from prediabetic individuals.
• Both B. uniformis and B. coprocola were enriched across AcKGM variants with different DS levels.
• The degree of enrichment of these two Bacteroides species showed a positive correlation with the acetylation degree (DS) of AcKGM.

Mono-culture assays demonstrated preferential utilization of highly acetylated AcKGM by both Bacteroides uniformis and Bacteroides coprocola.

• Pure culture experiments were conducted with B. uniformis and B. coprocola grown on AcKGM variants.
• Both species showed preferential growth or substrate utilization when provided with higher DS AcKGM.
• These findings were consistent with the in vitro fermentation results showing DS-dependent enrichment.

AcKGM improved glucose and lipid metabolism, suppressed inflammation, and ameliorated hepatosteatosis in prediabetic animals in a DS-dependent manner.

• Prediabetic animal experiments were conducted to assess anti-prediabetic efficacy of AcKGM variants.
• Beneficial effects on glucose metabolism, lipid metabolism, inflammatory markers, and liver fat accumulation (hepatosteatosis) were all observed.
• The magnitude of improvement across all these metabolic parameters was dependent on the degree of acetylation substitution (DS).
• Higher DS AcKGM produced greater improvements in these metabolic outcomes compared to lower DS variants.

The metabolic benefits of AcKGM in prediabetic animals were associated with DS-dependent enrichment of Bacteroides uniformis and upregulation of beneficial faecal metabolites including D-pantothenic acid.

• Higher DS AcKGM produced greater enrichment of B. uniformis in the animal gut microbiota.
• Faecal metabolite profiling identified D-pantothenic acid as one of the upregulated beneficial metabolites associated with AcKGM treatment.
• The upregulation of beneficial faecal metabolites also showed a DS-dependent pattern.
• These associations provide mechanistic links between AcKGM structure, gut microbiota modulation, and metabolic improvement.