Severe acute respiratory syndrome coronavirus-2 infection and the gut-liver axis

Patients affected by coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, manifest various gastrointestinal and hepatic abnormalities alongside respiratory disorders. The identification of this virus in the feces of more than 50% of infected individuals indicates the possibility of viral shedding and fecal-to-oral transmission. Preliminary reports have also identified alterations in the intestinal microbiota profile in infected individuals. Moreover, COVID-19 patients manifest various degrees of liver injury characterized by alterations in liver enzymes. Digestive symptoms and liver abnormalities correlate with disease severity, the incidence of critical outcomes and patient's recovery. However, the pathogenic mechanisms behind COVID-19-induced abnormalities in the gut-liver axis seem to be multifactorial in origin. This review compiles current knowledge sourced from preclinical and clinical research and summarizes gastrointestinal and hepatic dysfunctions observed following SARS-CoV-2 infection, and also explores the possible mechanisms generating abnormalities in the gut-liver axis. Furthermore, this review sheds light on possible therapeutic targets against these disorders.