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World J Gastroenterol. Jan 14, 2023; 29(2): 367-377
Published online Jan 14, 2023. doi: 10.3748/wjg.v29.i2.367
Non-alcoholic fatty liver disease and COVID-19: Harmless companions or disease intensifier?
Christoph G Dietrich, Andreas Geier, Uta Merle
Christoph G Dietrich, Gastro-Praxis Wiesbaden, Leberzentrum Wiesbaden, Wiesbaden 65189, Germany
Andreas Geier, Division of Hepatology, Department of Medicine II, University Hospital Wuerzburg, Wuerzburg 97080, Germany
Uta Merle, Department of Gastroenterology and Hepatology, University Hospital Heidelberg, Heidelberg 69120, Germany
Author contributions: Dietrich CG developed the concept of the review; and all authors contributed to literature searching and writing the manuscript.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Christoph G Dietrich, MD, PhD, Consultant Physician-Scientist, Gastro-Praxis Wiesbaden, Leberzentrum Wiesbaden, Langenbeckplatz 2, Wiesbaden 65189, Germany. christoph.g.dietrich@gmail.com
Received: October 1, 2022
Peer-review started: October 1, 2022
First decision: November 5, 2022
Revised: November 9, 2022
Accepted: December 21, 2022
Article in press: December 21, 2022
Published online: January 14, 2023
Processing time: 96 Days and 17.9 Hours
Abstract

The pandemics of coronavirus disease 2019 (COVID-19) and non-alcoholic fatty liver disease (NAFLD) coexist. Elevated liver function tests are frequent in COVID-19 and may influence liver damage in NAFLD, while preexisting liver damage from NAFLD may influence the course of COVID-19. However, the prognostic relevance of this interaction, though, is unclear. Obesity is a risk factor for the presence of NAFLD as well as a severe course of COVID-19. Cohort studies reveal conflicting results regarding the influence of NAFLD presence on COVID-19 illness severity. Striking molecular similarities of cytokine pathways in both diseases, including postacute sequelae of COVID-19, suggest common pathways for chronic low-activity inflammation. This review will summarize existing data regarding the interaction of both diseases and discuss possible mechanisms of the influence of one disease on the other.

Keywords: COVID-19; Postacute sequelae of COVID-19; Non-alcoholic fatty liver disease; Non-alcoholic steatohepatitis; Inflammation; Fatty liver

Core Tip: The “colliding” pandemics of coronavirus disease 2019 (COVID-19) and non-alcoholic fatty liver disease (NAFLD) influence each other in several ways. Molecular similarities of cytokine pathways in both diseases including postacute sequelae of COVID-19 (PASC) may be responsible for amplification of chronic low-active inflammation. While there are conflicting data regarding the clinical influence of NAFLD on acute COVID-19 and vice versa, further research is necessary to study the long-term influence of COVID-19 hygienic measures and PASC on NAFLD.