Microbial Fermentation of Dietary Protein: An Important Factor in Diet⁻Microbe⁻Host Interaction.

Natalie Diether,Benjamin Willing

doi:10.3390/microorganisms7010019

Natalie Diether, Benjamin Willing

Open Access

https://doi.org/10.3390/microorganisms7010019

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Journal: Microorganisms	Publication Date: Jan 13, 2019
Citations: 297	License type: CC BY 4.0

Affiliation: University of Alberta

Abstract

Protein fermentation by gut microbiota contributes significantly to the metabolite pool in the large intestine and may contribute to host amino acid balance. However, we have a limited understanding of the role that proteolytic metabolites have, both in the gut and in systemic circulation. A review of recent studies paired with findings from previous culture-based experiments suggests an important role for microbial protein fermentation in altering the gut microbiota and generating a diverse range of bioactive molecules which exert wide-ranging host effects. These metabolic products have been shown to increase inflammatory response, tissue permeability, and colitis severity in the gut. They are also implicated in the development of metabolic disease, including obesity, diabetes, and non-alcoholic fatty liver disease (NAFLD). Specific products of proteolytic fermentation such as hydrogen sulfide, ammonia, and p-Cresol may also contribute to the development of colorectal cancer. These findings are in conflict with other studies showing that tryptophan metabolites may improve gut barrier function and attenuate severity in a multiple sclerosis model. Further research examining proteolytic fermentation in the gut may be key to our understanding of how microbial and host metabolism interact affecting health.

Highlights

The gut microbiome is composed of a diverse range of species, the majority of which have a mutualistic relationship with the host, and, with 100 times more genes, perform metabolic functions greatly beyond those encoded in the host genome [1]
Much less is known about the role that proteolytic fermentation by gut microbes plays in host health and metabolism
This suggests that in pathological conditions where E. coli or Klebsiella are highly abundant in the gut, amino acids may become less available to the host, while protein fermentation by-products may contribute to disease pathology through increased inflammation

Summary

Introduction

The gut microbiome is composed of a diverse range of species, the majority of which have a mutualistic relationship with the host, and, with 100 times more genes, perform metabolic functions greatly beyond those encoded in the host genome [1]. It is clear that long-term dietary patterns, such as increased consumption of protein or decreased consumption of fiber, can shift the composition of the microbiota, changing which taxa and fermentation pathways are most abundant [5]. These system-level shifts in composition and metabolism hint at the complexity of metabolic interactions occurring in the gut microbial ecosystem, but more information is needed on the processes underlying these changes. This review will focus on the compartment-specific effects of proteolytic fermentation in different segments of the intestine along with metabolites such as ammonia, p-cresol, and amines that may shape health

Proteolytic Fermentation Involves Many Metabolic Pathways

Many Microbial Species Contribute to Proteolytic Fermentation

Diet Affects Proteolytic Fermentation

Findings

Discussion