Higher total faecal short chain fatty concentrations correlate with increasing proportions of butyrate and decreasing proportions of branched chain fatty acids across multiple human studies

Karen Scott* (Corresponding Author), Maria LaBouyer, Grietje Holtrop, Graham Horgan, Silvia Gratz, Alvaro Belenguer, Nicola Smith, Alan Walker, Sylvia Duncan, Alexandra Johnstone, Petra Louis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Metabolites produced by microbial fermentation in the human intestine, especially short-chain fatty acids (SCFAs), are known to play important roles in colonic and systemic health. Our aim here was to advance our understanding of how and why their concentrations and proportions vary between individuals. We have analysed faecal concentrations of microbial fermentation acids from 10 human volunteer studies, involving 163 subjects, conducted at the Rowett Institute, Aberdeen, UK over a 7-year period. In baseline samples, the % butyrate was significantly higher, whilst % iso-butyrate and % iso-valerate were significantly lower, with increasing total SCFA concentration. The decreasing proportions of iso-butyrate and iso-valerate, derived from amino acid fermentation, suggest that fibre intake was mainly responsible for increased SCFA concentrations. We propose that the increase in % butyrate among faecal SCFA is largely driven by a decrease in colonic pH resulting from higher SCFA concentrations. Consistent with this, both total SCFA and % butyrate increased significantly with decreasing pH across five studies for which faecal pH measurements were available. Colonic pH influences butyrate production through altering the stoichiometry of butyrate formation by butyrate-producing species, resulting in increased acetate uptake and butyrate formation, and facilitating increased relative abundance of butyrate-producing species (notably Roseburia and Eubacterium rectale).
Original languageEnglish
Article numbere2
Number of pages14
JournalGut Microbiome
Volume3
Early online date30 Mar 2022
DOIs
Publication statusPublished - 30 Mar 2022

Keywords

  • Short chain fatty acids
  • butyrate
  • branched chain fatty acids
  • human gut microbiota
  • faecal pH

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