key: cord-0858392-pcmnbdjj authors: Archer, Douglas L.; Kramer, Dean C. title: The Use of Microbial Accessible and Fermentable Carbohydrates and/or Butyrate as Supportive Treatment for Patients With Coronavirus SARS-CoV-2 Infection date: 2020-06-05 journal: Front Med (Lausanne) DOI: 10.3389/fmed.2020.00292 sha: 45a0df3f4dcabd3d442a11db3c8c29246e7beab3 doc_id: 858392 cord_uid: pcmnbdjj nan In addition to symptoms of fever, cough, and dyspnea, SARS-CoV-2 infection has been reported to also produce gastrointestinal symptoms. These symptoms can include anorexia, nausea, vomiting, and diarrhea. They are not unexpected symptoms, since enterocytes express the ACE2 receptor, and other requisite enzymes for SARS-CoV-2 uptake and replication (1) . Viral infection leading to enterocyte death would predictably cause both malabsorption and increased G.I. permeability (2) . Up to 50% of coronavirus cases reported from China had G.I. related symptoms (3), with recent corroboration in the United States (4) . After exposure to SARS-CoV-2, the estimated lag before onset of symptoms averages about 5 days. With limited oral intake following the onset of symptoms due to anorexia and other GI perturbations, there is marked alteration in intestinal microbial composition (dysbiosis) resulting in both macro and micronutrient deficiencies (5) . The alterations include a decrease in carbohydrate fermentation and precipitous decline in production of short chain fatty acids, most notably butyrate. Butyrate represents a well-characterized short chain fatty acid and functions as a key modulator of the immune system both in the intestinal tract (6) as well as in the lungs (7) , and is instrumental in maintaining the physical integrity and balanced permeability of the gut mucosal lining (8) . Deficiency of short chain fatty acids negatively impacts energy balance resulting in failure of the intestinal epithelial barrier and associated immune defenses. With increased intestinal damage and permeability, pathogenic microbes, their components, and other foreign antigens may enter the body unimpeded. It is, therefore, not surprising that damage to distant organs appears in the heart, liver, kidney, and brain as epithelial barriers collapse and inflammation processes intensify. Additionally, with lack of nutrients, short chain fatty acids are no longer available to stimulate bone marrow hematopoeisis which is felt to be a critical part of the gut-bone marrow-lung axis. Airway inflammation (7), the hallmark of acute respiratory distress syndrome (ARDS), proceeds unchecked frequently leading to death. The short chain fatty acid butyrate benefits patients with established allergic lung inflammation (9) . Specifically, butyrate has been shown to affect eosinophil trafficking and is able to "blunt migration into the lung, to reduce airway eosinophilia, and to ameliorate impaired lung function" (9) . Under siege by SARS-CoV-2, and perhaps due to over-stimulation of the gut associated lymphoid tissue, host defenses launch a counterattack releasing massive amounts of cytokines, resulting in a "cytokine storm" (10) . The cytokine storm attempts to destroy the infecting virus, but, in the process, collateral damage to nearby tissue occurs as well. With SARS-CoV-2 this is particularly true in lung tissue (11) . Given that the G.I. tract is the body's largest immunologic organ, it may be, in part, the genesis of the cytokine storm. The inflammation accompanying SARS-CoV-2 infection is reflected by high blood levels of C-reactive protein, TNF-alpha, and several interleukins, most notably proinflammatory IL-6 (12). Elevated IL-6 in severe Covid-19 patients is a predictor of higher mortality rates (13) . Some successes have been reported after treatment of Covid-19 patients with anti-inflammatory agents such as prednisone, and other anti-inflammatory drugs, including the IL-6 antagonist Tocilizumab (12) . Butyrate has definitively been found to lower IL-6 levels in both animal and human studies (14, 15) . Conceptually, providing the necessary substrate for the continued production of short chain fatty acids using supplements offers an appealing approach to minimizing the damage caused by SARS-CoV-2. Fructooligosaccharides, arabinoxylose, galactooligosaccharides, and gum guar represent but a few of the readily available carbohydrates capable of fermentation and production of short chain fatty acids. Gastric infusion of short chain fatty acids has been shown in the experimental animal to improve intestinal barrier function (16) . The effect of short chain fatty acids, especially butyrate, on gastrointestinal function in animals has been extensively studied with mixed findings, although recent modifications of formulations that modify the release profile have shown superior results (17) . Supplementing SARS-CoV-2 infected patients who are capable of tolerating oral intake with microbial accessible and fermentable carbohydrates could serve as a helpful adjunct in treating SARS-CoV-2 infection. For those patients unable to take food supplements or liquids by mouth, or who display symptoms of gastric upset or dysbiosis, nasogastric gavage of a butyrate solution or rectal administration of butyrate by enema could be considered. The use of butyrate enemas has been reported for multiple conditions including ulcerative colitis, diversion colitis, radiation proctitis, and pouchitis. Studies have yielded varying results making interpretation difficult [reviewed in Hamer et al. (18) , Luceri et al. (19) ]. The studies reported suffer from the lack of a standard protocol such as varying enema volumes, concentrations of butyrate, and frequency of administration. The proposed use of butyrate by enema would accomplish two things: • Direct application of butyrate to the site of the intestinal tract, terminal ileum and right colon that contains one of the highest concentrations of SARS-CoV-2 receptors, and • Increase butyrate absorption for systemic distribution since the colon is the primary site for both production and absorption of butyrate. Butyrate therapy has been demonstrated safe when administered by enema (18), per os (20), or intravenously (21) . More research into these potential adjunct therapies should be encouraged. Digestive system is a potential route of COVID-19: an analysis of single-cell coexpression pattern of key proteins in viral entry process COVID-19: gastrointestinal manifestations and potential fecal-oral transmission Digestive involvement in SARS-CoV-2 infection: a retrospective multi-center study High prevalence of concurrent gastrointestinal manifestations in patients with SARS-CoV-2: early experience from california The malnutritional status of the host as virulence factor for SARS-CoV-2 Butyrate: a double-edged sword for health? Microbes, metabolites, and the gut-lung axis Impact of diet-modulated butyrate production on intestinal barrier function and inflammation Butyrate ameliorates allergic airway inflammation by limiting eosinophil trafficking and survival COVID-19: consider cytokine storm syndromes and immunosuppression The landscape of lung bronchoalveolar immune cells in COVID-19 revealed by single-cell RNA sequencing. medRxiv The use of antiinflammatory drugs in the treatment of people with severe coronavirus disease 2019 (COVID-19): the experience of clinical immunologists from China Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study Beneficial effects of butyrate in intestinal injury Short-chain fatty acids suppress lipopolysaccharide-induced production of nitric oxide and proinflammatory cytokines through inhibition of NF-κB pathway in RAW264.7 cells Gastric infusion of short-chain fatty acids can improve intestinal barrier function in weaned piglets Effect of in feed administration of different butyrate formulations on Salmonella Enteritidis colonization and cecal microbiota in broilers Review article: the role of butyrate on colonic function Effect of butyrate enemas on gene expression profiles and endoscopic/histopathological scores of diverted colorectal mucosa: a randomized trial Clinical and pharmacologic study of tributyrin: an oral butyrate prodrug Clinical pharmacology of sodium butyrate in patients with acute leukemia The authors DK and DA contributed equally to this work and approved it for publication. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.Copyright © 2020 Archer and Kramer. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.