Pathogenic and Commensal Gut Bacteria Harboring Glycerol/Diol Dehydratase Metabolize Glycerol and Produce DNA-Reactive Acrolein

Abstract

Bacteria harboring glycerol/diol dehydratase (GDH) encoded by the genes pduCDE metabolize glycerol and release acrolein during growth. Acrolein has antimicrobial activity, and exposure of human cells to acrolein gives rise to toxic and mutagenic responses. These biological responses are related to acrolein’s high reactivity as a chemical electrophile that can covalently bind to cellular nucleophiles including DNA and proteins. Various food microbes and gut commensals transform glycerol to acrolein, but there is no direct evidence available for bacterial glycerol metabolism giving rise to DNA adducts. Moreover, it is unknown whether pathogens, such as Salmonella Typhymurium, catalyze this transformation. We assessed, therefore, acrolein formation by four GDH-competent strains of S. Typhymurium grown under either aerobic or anaerobic conditions in the presence of 50 mM glycerol. On the basis of analytical derivatization with a heterocyclic amine, all wild-type strains were observed to produce acrolein, but to different extents, and acrolein production was not detected in fermentations of a pduC-deficient mutant strain. Furthermore, we found that, in the presence of calf thymus DNA, acrolein-DNA adducts were formed as a result of bacterial glycerol metabolism by two strains of Limosilactobacillus reuteri, but not a pduCDE mutant strain. The quantification of the resulting adducts with increasing levels of glycerol up to 600 mM led to the production of up to 1.5 mM acrolein and 3600 acrolein-DNA adducts per 108 nucleosides in a model system. These results suggest that GDH-competent food microbes, gut commensals, and pathogens alike have the capacity to produce acrolein from glycerol. Further, the acrolein production can lead to DNA adduct formation, but requires high glycerol concentrations that are not available in the human gut.

Ethanologenesis from glycerol by the gut acetogen Blautia schinkii

“…This antimicrombial substance is produced by a diol dehydratase, which is encoded within the pdu ‐BMC gene cluster of A. woodii and expressed during growth on glycerol (Trifunovic et al, 2021). Interestingly, production of 3‐hydroxypropionaldehyde from glycerol by the same diol dehydratase is a common feature of many gut bacteria such as Lactobacillus reuteri or Blautia obeum to prevent infections by pathogenic bacteria such as S. enterica (De Weirdt et al, 2012; Ramirez Garcia et al, 2022). In most cases, 3‐HPA is an intermediate, which is further metabolized to 1,3‐propanediol (Engels et al, 2016; Vollenweider & Lacroix, 2004).…”

“…Furthermore, glycerol is used as additive in formulated foods (Zhang et al, 2018). Most of the consumed glycerol will be absorbed by the human intestine, leaving glycerol concentrations between 4 and 10 mM in healthy individuals (Morita et al, 2008; Ramirez Garcia et al, 2022). Due to the glycerol uptake by the microbiome, the actual glycerol concentration might be higher (De Weirdt et al, 2012).…”

Mass Spectrometry Analysis of DNA and Protein Adducts as Biomarkers in Human Exposure to Cigarette Smoking: Acrolein as an Example

“…The heating of lipids and carbohydrates during cooking of food also releases this reactive aldehyde. Acrolein is also generated in the body by endogenous peroxidation of lipids, degradation of carbohydrates and amino acids, metabolism of polyamines, and from glycerol by microbiota. − Exposure to acrolein can lead to pathological conditions in cancers and cardiovascular and neurodegenerative diseases. − In particular, acrolein might play an essential role in smoking-induced lung cancer . Acrolein was recently classified as a “ Group 2A (probably carcinogenic to humans)” carcinogen from “Group 3 carcinogens (not classifiable as to its carcinogenicity to humans)” by the International Agency for Research on Cancer (IARC)…”

Application of the Reuterin System as Food Preservative or Health-Promoting Agent: A Critical Review

“…Acrolein produced by GDH-competent intestinal bacteria by metabolizing glycerol can lead to the formation of the acrolein-DNA adduct, which may induce mutations in a model system containing resting cells of L. reuteri in combination with calf thymus DNA or bovine serum albumin. However, the concentration of glycerol needed to cause the acrolein-DNA adduct-mediated mutation was much higher than the physiological concentration [ 55 ]. Nevertheless, the association between the carcinogenicity of acrolein observed in cytotoxicity assays and human health remains hypothetical, and has not been verified in clinic trials yet [ 56 ].…”