COVID-19 in normal, diseased and transplanted liver

Abstract

Starting from December 2019 the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has extended in the entire world giving origin to a pandemic. Although the respiratory system is the main apparatus involved by the infection, several other organs may suffer coronavirus disease 2019 (COVID-19)-related injuries. The human tissues expressing angiotensin-converting enzyme 2 (ACE2) are all possible targets of viral damage. In fact myocarditis, meningo-encephalitis, acute kidney injury and other complications have been described with regard to SARS-CoV-2 infection. The liver has a central role in the body homeostasis contributing to detoxification, catabolism and also synthesis of important factor such as plasma proteins. ACE2 is significantly expressed just by cholangiocytes within the liver, however transaminases are increased in more than one third of COVID-19 patients, at hospital admission. The reasons for liver impairment in the course of this infection are not completely clear at present and multiple factors such as: Direct viral effect, release of cytokines, ischemic damage, use of hepatotoxic drugs, sepsis, and others, may contribute to damage. While COVID-19 seems to elicit just a transient alteration of liver function tests in subjects with normal hepatic function, of concern, more severe sequelae are frequently observed in patients with a reduced hepatic reserve. In this review we report data regarding SARS-CoV-2 infection in subjects with normal or diseased liver. In addition the risks of COVID-19 in immunosuppressed patients (either transplanted or suffering for autoimmune liver diseases) are also described.

Keywords: Angiotensin-converting enzyme 2; COVID-19; Cirrhosis; Liver; Liver transplant; Non-alcoholic fatty-liver-disease.

Figure 1

Organs of human body (different from lung and liver) in which angiotensin-converting enzyme 2 was detected, the main site of expression and the possible coronavirus disease 2019 related symptoms/complications are reported in the corresponding columns. COVID-19: Coronavirus disease 2019; ACE2: Angiotensin-converting enzyme 2.

Figure 2

The putative mechanisms inducing liver injury in the course of coronavirus disease 2019 are reported in the left side of the figure (? = controversial data on the specific mechanism). The right part describes the possible outcome according to patient baseline liver condition. NAFLD: Non-alcoholic fatty-liver-disease; COVID-19: Coronavirus disease 2019.