Hippuric acid is partly derived via gut microbial metabolism of polyphenols. Higher amounts can indicate increased bacterial degradation of aromatic compounds.
References
Clarke G, Quilty E, Kennedy PJ, Stanton C, Ross RP, Hill C, et al.. Hippurate as a metabolomic marker of gut microbiome diversity - NCBI. Nature Communications (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651863/Khafipour E, Kittelmann S, Zebeli Q, McAllister TA. Effects of a blend of Saccharomyces cerevisiae-based direct-fed microbials on rumen fermentation, methane emissions, and bacterial community in steers. Journal of Animal Science and Biotechnology (2020). https://jasbsci.biomedcentral.com/articles/10.1186/s40104-019-0419-5Berry D, Gautam D, Huttenhower C. Amino acid auxotrophies in human gut bacteria are linked to higher diversity and altered metabolism. Nature Microbiology (2023). https://www.nature.com/articles/s41396-023-01537-3Wikoff WR, Anfora AT, Liu J, Schultz PG, Lesley SA, Peters EC, et al.. Metabolomics analysis reveals large effects of gut microflora on mammalian physiology. Proceedings of the National Academy of Sciences (2009). https://www.pnas.org/doi/10.1073/pnas.0812874106Collino S, Binda S, Ciccacci M, Di Cagno R, Ercolini D, Gobbetti M. Disentangling the Complexity of Nutrition, Frailty and Gut Microbial Dysbiosis in the Elderly. Nutrients (2023). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10005077/
Indoleacetic acid is a metabolite produced from bacterial breakdown of tryptophan. Elevated levels can reflect increased bacterial load or imbalanced gut microbiome.
References
Pieter C. Dorrestein, J. Christopher Hamilton, and Eric W. Triplett. Indole-3-acetic acid in microbial and microorganism-plant signaling literature. FEMS Microbiology Reviews (2007). https://academic.oup.com/femsre/article/31/4/425/2399113Sasitorn Bunsangiam, Nattawut Thongpae, Sasitorn Limtong, and Wiyong Sirisansaneeyakul. Large scale production of indole-3-acetic acid and evaluation of the inhibitory effect of indole-3-acetic acid on weed growth. Scientific Reports (2021). https://doi.org/10.1038/s41598-021-92305-wShih-Feng Fu, Jyuan-Yu Wei, Hung-Wei Chen, Yen-Yu Liu, Hsueh-Yu Lu, and Jui-Yu Chou. Indole-3-acetic acid: A widespread physiological code in interactions of fungi with other organisms. PLOS ONE (2016). https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147590
Indolepropionic acid is formed by bacterial action on tryptophan in the intestines. High amounts suggest greater bacterial metabolism and potential gut flora imbalances.
References
Ratika Sehgal, Vanessa D. de Mello, Ville Männistö, Jaana Lindström, Jaakko Tuomilehto, Jussi Pihlajamäki. Indolepropionic Acid, a Gut Bacteria-Produced Tryptophan Metabolite and the Risk of Type 2 Diabetes and Non-Alcoholic Fatty Liver Disease. Nutrients (2022). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9653718/Xiaoxiang Ma, Xiangyu Zhang, Xiangyu Zhang, Xiangyu Zhang, Xiangyu Zhang. Extensive Summary of the Important Roles of Indole Propionic Acid, a Gut Microbial Metabolite in Host Health and Disease. Frontiers in Microbiology (2022). https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.575586/full
Indoxyl sulfate is derived from bacterial fermentation of tryptophan and is a uremic toxin. Increased levels are associated with an altered gut microbiome composition.
References
Correspondence: ude.drofnats@hcirist; Tel.: +1-650-493-5000 (ext. 68321);. Indoxyl Sulfate—Review of Toxicity and Therapeutic Strategies. Clinical Journal of the American Society of Nephrology (2016). https://cjasn.asnjournals.org/content/11/11/1965J. J. Cochain, A. Delanghe, J. Depauw, et al.. Indoxyl sulfate, a gut microbiome-derived uremic toxin, is associated with cardiovascular disease in patients with chronic kidney disease. Scientific Reports (2021). https://doi.org/10.1038/s41598-021-99845-1Y. Wang, Y. Zhang, J. Zhang, et al.. Targeting the gut microbial metabolic pathway with small molecules: A promising strategy to control host uremic toxin production. Biochemical and Biophysical Research Communications (2020). https://doi.org/10.1016/j.bbrc.2020.09.121
p-Cresol sulfate is generated by intestinal bacteria from tyrosine. Elevated concentrations are linked to dysbiosis and overgrowth of certain bacterial species.