The Antioxidants Glutathione, Ascorbic Acid and Uric Acid Maintain Butyrate Production by Human Gut Clostridia in The Presence of Oxygen In Vitro

Matthieu Million,Gregory Dubourg,Eric Chabriere,Saber Khelaifia,Nicholas Armstrong,Jean-Christophe Lagier,Magali Richez,Elodie Guilhot,Didier Raoult

doi:10.1038/s41598-020-64834-3

Abstract

Uncontrolled oxidative stress, reported in Salmonella and HIV infections, colorectal cancer or severe acute malnutrition, has been associated with anaerobic gut microbiome alteration, impaired butyrate production, mucosal immunity dysregulation and disruption of host-bacterial mutualism. However, the role of major antioxidant molecules in the human body, such as glutathione, ascorbic acid and uric acid, has been neglected in this context. Here, we performed an in vitro metabolomics study of the 3 most odorous anaerobic microbes isolated from the human gut in our laboratory (Clostridium sporogenes, Clostridium subterminale and Romboutsia lituseburensis) when grown in anaerobiosis or in aerobiosis with these 3 antioxidant molecules via gas and liquid chromatography-mass spectrometry (GC/MS and LC/MS). There was no growth or volatile organic compound production in aerobic cultures without the 3 antioxidant molecules. In anaerobiosis, the major metabolic products of the bacteria were thiols, alcohols and short-chain fatty acid esters. The production of alkanes, cycloheptatriene and, paradoxically, increased butyrate production, was observed in the cultures grown in aerobiosis with the 3 antioxidant molecules. The qualitative shift suggests specific molecular mechanisms that remain to be elucidated. The increased production of butyrate, but also isobutyrate and isovalerate in vitro suggests that these 3 antioxidant molecules contributed to the maintenance and active resilience of host-bacterial mutualism against mucosal oxygen and uncontrolled oxidative stress in vivo.

Highlights

On the other hand, we have recently identified a link between redox state and the microbiome[10]
The 3 bacterial strains did not survive, and there was no production of Volatile organic compounds (VOC) or short-chain fatty acid (SCFA) by the bacteria in aerobiosis without the 3 antioxidant molecules
We compared the amount and profile of VOCs, SCFAs and polar metabolites of cultures grown in anaerobiosis and in aerobiosis with ascorbate, glutathione and uric acid

Summary

Introduction

We have recently identified a link between redox state and the microbiome[10]. There is a link between redox potential, oxidative stress and human microbiota according to the oxygen tolerance of www.nature.com/scientificreports each species and the abundance of antioxidants in the environment. In children with severe acute malnutrition, we have shown a major depletion of anaerobic microbes (intolerant to reactive oxidative species)[13], consistent with the collapse of fecal butyrate in those who die[14]. This led us to rediscover that antioxidants allow for most anaerobes, including methanogenic archaea, to thrive in an oxidative (aerobic) environment[15,16,17,18,19,20]. Butyrate production by the bacteria was increased in aerobiosis with medium supplemented with uric acid, ascorbate, and glutathione, suggesting a critical role of these antioxidant molecules in the maintenance of butyrate production at the gut microbial-mucosal interface

Methods

Results

Conclusion