Why does increased microbial fermentation in the human colon shift toward butyrate?

Harry J. Flint; Petra Louis; Sylvia H. Duncan; Harry J. Flint; Petra Louis; Sylvia H. Duncan

doi:10.3934/microbiol.2024016

AIMS Microbiology

2024, Volume 10, Issue 2: 311-319. doi: 10.3934/microbiol.2024016

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Commentary

Why does increased microbial fermentation in the human colon shift toward butyrate?

Rowett Institute, University of Aberdeen, Foresterhill, Aberdeen, UK AB25 2ZD

Received: 05 March 2024 Revised: 15 April 2024 Accepted: 25 April 2024 Published: 06 May 2024

The microbial community of the human large intestine mainly ferments dietary fiber to short chain fatty acids (SCFAs), which are efficiently absorbed by the host. The three major SCFAs (acetate, propionate, and butyrate) have different fates within the body and different effects on health. A recent analysis of 10 human volunteer studies established that the proportions of these SCFA in fecal samples significantly shifted towards butyrate as the overall concentration of SCFA increased. Butyrate plays a key role in gut health and is preferentially utilized as an energy source by the colonic epithelium. Here we discuss possible mechanisms that underlie this ‘butyrate shift’; these include the selection for butyrate-producing bacteria within the microbiota by certain types of fiber, and the possibility of additional butyrate formation from lactate and acetate by metabolite cross-feeding. However, a crucial factor appears to be the pH in the proximal colon, which decreases as the SCFA concentrations increase. A mildly acidic pH has been shown to have an important impact on microbial competition and on the stoichiometry of butyrate production. Understanding these complex interactions has been greatly aided by the refinement of theoretical models of the colonic microbiota that assume a small number (10) of microbial functional groups (MFGs).
- fermentation,
- human colon,
- butyrate,
- carbohydrate fiber,
- short chain fatty acids,
- theoretical modelling,
- colonic pH,
- health
Citation: Harry J. Flint, Petra Louis, Sylvia H. Duncan. Why does increased microbial fermentation in the human colon shift toward butyrate?[J]. AIMS Microbiology, 2024, 10(2): 311-319. doi: 10.3934/microbiol.2024016

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Abstract

The microbial community of the human large intestine mainly ferments dietary fiber to short chain fatty acids (SCFAs), which are efficiently absorbed by the host. The three major SCFAs (acetate, propionate, and butyrate) have different fates within the body and different effects on health. A recent analysis of 10 human volunteer studies established that the proportions of these SCFA in fecal samples significantly shifted towards butyrate as the overall concentration of SCFA increased. Butyrate plays a key role in gut health and is preferentially utilized as an energy source by the colonic epithelium. Here we discuss possible mechanisms that underlie this ‘butyrate shift’; these include the selection for butyrate-producing bacteria within the microbiota by certain types of fiber, and the possibility of additional butyrate formation from lactate and acetate by metabolite cross-feeding. However, a crucial factor appears to be the pH in the proximal colon, which decreases as the SCFA concentrations increase. A mildly acidic pH has been shown to have an important impact on microbial competition and on the stoichiometry of butyrate production. Understanding these complex interactions has been greatly aided by the refinement of theoretical models of the colonic microbiota that assume a small number (10) of microbial functional groups (MFGs).

Acknowledgments

The authors acknowledge support from the Scottish Government Food Land and People programme.

References

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