Cited by 319Pharmacogenetics and Drug MetabolismGut microbiota and healthDrug Transport and Resistance Mechanisms

The DOI matches its Crossref record; 320 of the 323 references it cites were found in a registry or an index; 3 of the 203 sources its claims cite were checked for support.

Gut Reactions: Breaking Down Xenobiotic–Microbiome Interactions

Open access

Abstract

The microbiome plays a key role in health and disease, and there has been considerable interest in therapeutic targeting of the microbiome as well as mining this rich resource in drug discovery efforts. However, a growing body of evidence suggests that the gut microbiota can itself influence the actions of a range of xenobiotics, in both beneficial and potentially harmful ways. Traditionally, clinical studies evaluating the pharmacokinetics of new drugs have mostly ignored the important direct and indirect effects of the gut microbiome on drug metabolism and efficacy. Despite some important observations from xenobiotic metabolism in general, there is only an incomplete understanding of the scope of influence of the microbiome specifically on drug metabolism and absorption, and how this might influence systemic concentrations of parent compounds and toxic metabolites. The significance of both microbial metabolism of xenobiotics and the impact of the gut microbiome on host hepatic enzyme systems is nonetheless gaining traction and presents a further challenge in drug discovery efforts, with implications for improving treatment outcomes or counteracting adverse drug reactions. Microbial factors must now be considered when determining drug pharmacokinetics and the impact that an evolving and dynamic microbiome could have in this regard. In this review, we aim to integrate the contribution of the gut microbiome in health and disease to xenobiotic metabolism focusing on therapeutic interventions, pharmacological drug action, and chemical biotransformations that collectively will have implications for the future practice of precision medicine.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This narrative review argues that the gut microbiome exerts both direct (microbial biotransformation) and indirect (regulation of host hepatic enzymes) effects on xenobiotic metabolism, with consequences for drug activation, inactivation, toxicity, and therapeutic response. It calls for incorporating microbial factors into pharmacokinetic/pharmacodynamic profiling and precision medicine.

Key findings

  • Direct microbial biotransformation can activate prodrugs (e.g., sulfasalazine to 5-ASA by azoreductases), reactivate drugs (irinotecan to cytotoxic SN-38 via β-glucuronidases, causing GI side effects), or inactivate drugs (digoxin reduction contingent on specific *Eggerthella lenta* strains and inhibited by dietary arginine).
  • The gut microbiome indirectly regulates host hepatic drug-processing genes: germ-free mice show markedly reduced hepatic Cyp3a11 mRNA/protein (the mouse homolog of human CYP3A4, which metabolizes >60% of drugs), while Cyp1a2 and Cyp4a14 are substantially increased; effects are enzyme-specific and depend on age and sex, with the largest effects in male mice at 90 days.
  • A screen of >1000 marketed drugs against individual gut bacteria found that 24% of drugs with human targets inhibited growth of at least one bacterial strain in vitro; metformin, methotrexate, olanzapine, risperidone, PPIs, opioids, and NSAIDs are cited as altering microbiome composition/diversity.
  • Microbial metabolism of dietary choline and carnitine produces TMA, which host hepatic processing converts to TMAO, associated with atherosclerosis; choline TMA-lyase was present in only 26% of individuals in one cited study.

Methods

  • Narrative review integrating existing literature on gut microbiome–xenobiotic interactions; no primary data are generated.
  • Covers microbiome composition in health/disease, biochemistry of microbial xenobiotic metabolism, factors influencing its rate/extent, evolutionary perspectives, stress-related disorders, reciprocal drug–microbiome effects, experimental approaches (germ-free and antibiotic-depleted animals, monoassociation, *C. elegans*, in vitro batch/fermentation systems, fecalase/cecalase assays, functional metagenomics, in silico/PBPK modeling, organ-on-a-chip, organoids), and microbiome-based therapeutics.
  • Synthesizes findings into tables of microbial enzymes/biotransformations (Table 1), microbial regulation of host hepatic CYPs (Table 2), clinical specialties and pharmacomicrobiomics (Table 3), and outstanding questions (Table 4).

Limitations

  • Stated in the paper: overreliance on fecal samples means the microbiota of more proximal regions (especially the small intestine) is poorly understood; the small intestine has higher xenobiotic exposure but lower microbial density, and its contribution is understudied.
  • Stated in the paper: germ-free and antibiotic-depleted rodent models have intrinsic gastrointestinal and microbial differences from humans, and germ-free animals show physiologic/morphologic differences relevant to xenobiotic metabolism; the extent to which inducibility of microbial enzymes generalizes is unclear.
  • Evident from the text: because members of the bacterial ecosystem may exhibit functional redundancy and pleiotropy, the link between microbiota composition ("structure begets function") and xenobiotic metabolism is difficult to gauge; the paper also notes that actual metabolic activity may diverge from functional potential, and that many enzyme–species assignments remain unknown.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1124/pr.118.015768

Cites

320 of 320 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

160 Not checked yet · 23 No basis given · 17 Own interpretation · 1 Supported · 1 Partly supported · 1 Not supported · accuracy not yet measured

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Show all 138 claims

  • It may state two separate claims as one. 48
  • Probably not a substantial claim. 23
65 of 65
  • The paper relies on this without support.

    Clinical studies evaluating the pharmacokinetics of new drugs have mostly ignored the important direct and indirect effects of the gut microbiome on drug metabolism and efficacy.

    “Traditionally, clinical studies evaluating the pharmacokinetics of new drugs have mostly ignored the important direct and indirect effects of the gut microbiome on drug metabolism and efficacy.”
  • The paper relies on this without support.

    There is only an incomplete understanding of the scope of influence of the microbiome specifically on drug metabolism and absorption, and how this might influence systemic concentrations of parent compounds and toxic metabolites.

    “Despite some important observations from xenobiotic metabolism in general, there is only an incomplete understanding of the scope of influence of the microbiome specifically on drug metabolism and absorption, and how this might influence systemic concentrations of parent compounds and toxic metabolites.”
  • The authors state this as an assumption.

    The majority of orally administered drugs are normally absorbed in the upper small intestine, assuming that the drug is highly soluble and highly permeable in this region.

    “The majority of orally administered drugs are normally absorbed in the upper small intestine, the prime absorptive region of the intestine, assuming that the drug is highly soluble and highly permeable in this region.”
  • The paper relies on this without support.

    The small-intestinal microbiota is less well studied due in part to the difficulty in obtaining relevant samples.

    “However, this needs to be considered in context of the less well studied smallintestinal microbiota, due in part to the difficulty in obtaining relevant samples.”
  • The paper relies on this without support.

    There remains no consensus on the actual membership of the core taxa present in the gut microbiome, and different sequencing and analysis approaches will give different results.

    “It should be noted that there remains to be a consensus on actual membership of the core taxa present in the gut microbiome, and different sequencing and analysis approaches will give different results.”
  • The paper relies on this without support.

    The contribution of modified release formulations to bioavailability is rarely appraised.

    “this is a feature rarely appraised for its contribution to bioavailability.”
  • The paper relies on this without support.

    Knowledge of interindividual variation of the gut microbiome during health and disease at the taxonomic level is more advanced than the grasp of the functional implications of these compositional differences.

    “our knowledge of interindividual variation of the gut microbiome during health and disease at the taxonomic level is more advanced than our grasp of the functional implications, if any, of these compositional differences.”
  • The paper relies on this without support.

    The functional implications of disease-associated gut microbiome alterations are not currently clear for microbial xenobiotic metabolism.

    “the functional implications of these gut microbiome alterations are not currently clear for microbial xenobiotic metabolism.”
  • The paper relies on this without support.

    Bacterial genes encoding porphyranases, agarases, and associated proteins transferred from marine red algae to bacteria residing in the gastrointestinal tract of Japanese individuals as a consequence of their seaweed consumption.

    “transfer of bacterial genes encoding porphyranases, agarases, and associated proteins from marine red algae to bacteria residing in the gastrointestinal tract of Japanese individuals as a consequence of their seaweed consumption.”
  • The paper relies on this without support.

    The majority of orally administered drugs are normally absorbed in the upper small intestine.

    “The majority of orally administered drugs are normally absorbed in the upper small intestine assuming that the drug is highly soluble and highly permeable in this region.”
  • The authors state this as an assumption.

    Orally administered drugs are highly soluble and highly permeable in the upper small intestine.

    “The majority of orally administered drugs are normally absorbed in the upper small intestine assuming that the drug is highly soluble and highly permeable in this region.”
11 of 11

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Metadata

Authors
Clarke, G., Sandhu, K. V., Griffin, B. T., Dinan, T. G., Cryan, J. F., & Hyland, N. P.
Affiliations
University College Cork (IE)
Venue
Pharmacological Reviews
Publisher
Elsevier BV
Published
2019-04
Volume
71
Issue
2
Pages
198-224
ISSN
0031-6997 (ISSN-L)
OpenAlex
W2925298688
Cited by
319
References
323
Citations by year
2026: 34 · 2025: 26 · 2024: 42 · 2023: 43 · 2022: 42 · 2021: 56 · 2020: 60 · 2019: 16
FWCI
6.91
Type
journal article
Language
en
Open access
Locations
  • Pharmacological Reviews (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Cork Open Research Archive (University College Cork, Ireland) (publishedVersion, cc-by)
  • Arrow@dit (Dublin Institute of Technology) (submittedVersion, cc-by)
  • Cork Open Research Archive (University College Cork, Ireland) (submittedVersion, cc-by)
Funders
Science Foundation Ireland (SFI/12/RC/, 12/RC/2273, 12/RC/, SFI/12/RC/2273.)
Topics
  • Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmacogenetics and Drug Metabolism
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Gut microbiota and health
  • Health Sciences › Medicine › Oncology › Drug Transport and Resistance Mechanisms
Keywords
gut microbiota, xenobiotic metabolism, drug metabolism, pharmacokinetics, microbiome-targeted therapy, drug discovery, drug absorption, microbial metabolites, adverse drug reactions, precision medicine
MeSH terms
Gastrointestinal Microbiome, Animals, Humans, Xenobiotics, Drug Discovery, Precision Medicine, Microbiota, Drug-Related Side Effects and Adverse Reactions

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