Syndecan-1 in liver pathophysiology.

Syndecan-1 (SDC-1) is a heparan sulfate (HS)/chondroitin sulfate proteoglycan (PG) of the cell surface and the extracellular matrix (ECM), which regulates a broad spectrum of physiological and pathological processes such as cell proliferation, migration, inflammation, matrix remodeling, wound healing, and tumorigenesis. Syndecan-1 represents the major PG of the liver, expressed by hepatocytes and cholangiocytes, and its elevated expression is a characteristic feature of liver diseases. The highest syndecan-1 expression is found in liver cirrhosis and in hepatocellular carcinoma (HCC) developed in cirrhotic livers. In addition, as being a hepatitis C receptor, hepatitis C virus (HCV)-infected livers produce extremely large amounts of syndecan-1. The serum levels of the cleaved (shedded) extracellular domain have clinical significance, as their increased concentration reflects on poor prognosis in cirrhosis as well as in cancer. In vivo experiments confirmed that syndecan-1 protects against early stages of fibrogenesis mainly by enhanced clearance of transforming growth factor ß1 (TGFß1) and thrombospondin-1 (THBS1) via circulation, and against hepatocarcinogenesis by interfering with several signaling pathways and enhancing cell cycle blockade. In addition, syndecan-1 is capable to hinder lipid metabolism and ribosomal biogenesis in induced cancer models. These observations together with its participation in the uptake of viruses (e.g., HCV and SARS-CoV-2) indicate that syndecan-1 is a central player in liver pathologies.

Prognosis and antibody profiles in survivors of critical illness from COVID-19: a prospective multicentre cohort study.

BACKGROUND: There is a need to assess the long-term outcomes of survivors of critical illness from COVID-19. METHODS: Ninety-two survivors of critical illness from COVID-19 from four hospitals in Hubei Province, China participated in this prospective cohort study. Multiple characteristics, including lung function (lung volumes, diffusing capacity for carbon monoxide, chest computed tomography scores, and walking capacity); immune status (SARS-CoV-2-neutralising antibody and all subtypes of immunoglobulin (Ig) G against SARS-CoV-2, immune cells in response to ex vivo antigen peptide stimuli, and lymphocyte count and its subtypes); liver, coagulation, and kidney functions; quality of life; cognitive function; and mental status, were assessed after 3, 6, and 12 months of follow-up. RESULTS: Amongst the 92 enrolled survivors, 72 (78%) patients required mechanical ventilation. At 12 months, the predicted percentage diffusing capacity of lung for carbon monoxide was 82% (inter-quartile range [IQR]: 76-97%) with a residual volume of 77 (64-88)%. Other lung function parameters and the 6-min walk test improved gradually over time and were almost back to normal by 12 months. The titres of IgG and neutralising antibody to COVID-19 remained high at 12 months compared with those of controls who were not infected with COVID-19, although IgG titres decreased significantly from 34.0 (IQR: 23.8-74.3) to 15.0 (5.8-24.3) AU ml-1 (P<0.001), whereas neutralising antibodies decreased from 29.99 (IQR: 19.43-53.93) AU ml-1 at 6 months to 19.75 (13.1-29.8) AU ml-1 (P<0.001) at 12 months. In general, liver, kidney, physical, and mental functions also improved over time. CONCLUSIONS: Survivors of critical illness from COVID-19 show some persistent long-term impairments in lung function. However, a majority of these tests were normal by 12 months. These patients still had detectable levels of neutralising antibodies against SARS-CoV-2 and all types of IgG at 12 months, but the levels had declined over this time period. CLINICAL TRIAL REGISTRATION: None.

The Associations of Lymphocyte Ratio and Neutrophil Ratio on Liver Dysfunction in COVID-19 Patients.

Data on the impact of lymphocytes and neutrophils on the incidence of liver dysfunction in COVID-19 patients are limited. This study aimed to investigate the lateral and longitudinal associations of lymphocyte ratio (LR) and neutrophil ratio (NR) on liver dysfunction in COVID-19 patients. We tested 1,409 blood samples from 245 COVID-19 patients in China between January 2020 and June 2021. The lateral U-shaped relationships, determined by smooth curve fitting and the piecewise-linear mixed-effect model, were observed between LR, NR, and AST and the incidence of AST-linked liver dysfunction, with the threshold cutoffs of 26.1 and 62.0, respectively. Over the 1,409 tests, the LR ≤ 26.1 and NR ≥ 62.0 related to the occurrence of mild liver dysfunction (HR: 1.36; 95% CI: 1.01, 1.82), moderate liver dysfunction (HR: 1.37; 95% CI: 1.01, 1.85), and severe liver dysfunction (HR: 1.72; 95% CI: 1.02, 2.90). For the patients with preexisting AST ≥ 35 U/L, the baseline LR ≤ 26.1 and NR ≥ 62.0 (b.LLCHN) groups had a fully adjusted 8.85-, 7.88-, and 5.97-fold increased risk of mild and moderate liver dysfunction after being hospitalized of 3, 6, and 9 days compared to the baseline LR > 26.1 and NR < 62.0 (b.normal) groups. Severe liver dysfunction only presents significant differences after being adjusted for age, sex, and BMI. Consistently, Kaplan-Meier analyses showed that b.LLCHN reflects a better predictive value for different subsequent magnitude liver dysfunctions after admission of 3 and 6 days. To improve liver function in patients with preexisting AST ≥35 U/L, future management strategies should pay more attention to baseline LR ≤ 26.1 and NR ≥ 62.0 patients.

Correlation Between Clinical and Pathological Findings of Liver Injury in 27 Patients With Lethal COVID-19 Infections in Brazil.

Liver test abnormalities are frequently observed in patients with coronavirus disease 2019 (COVID-19) and are associated with worse prognosis. However, information is limited about pathological changes in the liver in this infection, so the mechanism of liver injury is unclear. Here we describe liver histopathology and clinical correlates of 27 patients who died of COVID-19 in Manaus, Brazil. There was a high prevalence of liver injury (elevated alanine aminotransferase and aspartate aminotransferase in 44% and 48% of patients, respectively) in these patients. Histological analysis showed sinusoidal congestion and ischemic necrosis in more than 85% of the cases, but these appeared to be secondary to systemic rather than intrahepatic thrombotic events, as only 14% and 22% of samples were positive for CD61 (marker of platelet activation) and C4d (activated complement factor), respectively. Furthermore, the extent of these vascular findings did not correlate with the extent of transaminase elevations. Steatosis was present in 63% of patients, and portal inflammation was present in 52%. In most cases, hepatocytes expressed angiotensin-converting enzyme 2 (ACE2), which is responsible for binding and entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), even though this ectoenzyme was minimally expressed on hepatocytes in normal controls. However, SARS-CoV-2 staining was not observed. Most hepatocytes also expressed inositol 1,4,5-triphosphate receptor 3 (ITPR3), a calcium channel that becomes expressed in acute liver injury. Conclusion: The hepatocellular injury that commonly occurs in patients with severe COVID-19 is not due to the vascular events that contribute to pulmonary or cardiac damage. However, new expression of ACE2 and ITPR3 with concomitant inflammation and steatosis suggests that liver injury may result from inflammation, metabolic abnormalities, and perhaps direct viral injury.

Treatments in Covid-19 patients with pre-existing metabolic dysfunction-associated fatty liver disease: A potential threat for drug-induced liver injury?

Obese patients who often present metabolic dysfunction-associated fatty liver disease (MAFLD) are at risk of severe presentation of coronavirus disease 2019 (COVID-19). These patients are more likely to be hospitalized and receive antiviral agents and other drugs required to treat acute respiratory distress syndrome and systemic inflammation, combat bacterial and fungal superinfections and reverse multi-organ failure. Among these pharmaceuticals, antiretrovirals such as lopinavir/ritonavir and remdesivir, antibiotics and antifungal agents can induce drug-induced liver injury (DILI), whose mechanisms are not always understood. In the present article, we hypothesize that obese COVID-19 patients with MAFLD might be at higher risk for DILI than non-infected healthy individuals or MAFLD patients. These patients present several concomitant factors, which individually can favour DILI: polypharmacy, systemic inflammation at risk of cytokine storm, fatty liver and sometimes nonalcoholic steatohepatitis (NASH) as well as insulin resistance and other diseases linked to obesity. Hence, in obese COVID-19 patients, some drugs might cause more severe (and/or more frequent) DILI, while others might trigger the transition of fatty liver to NASH, or worsen pre-existing steatosis, necroinflammation and fibrosis. We also present the main mechanisms whereby drugs can be more hepatotoxic in MAFLD including impaired activity of xenobiotic-metabolizing enzymes, mitochondrial dysfunction, altered lipid homeostasis and oxidative stress. Although comprehensive investigations are needed to confirm our hypothesis, we believe that the current epidemic of obesity and related metabolic diseases has extensively contributed to increase the number of cases of DILI in COVID-19 patients, which may have participated in presentation severity and death.

Predictors of mortality in patients with coronavirus disease 2019: a systematic review and meta-analysis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is associated with a high mortality rate, especially in patients with severe illness. We conducted a systematic review and meta-analysis to assess the potential predictors of mortality in patients with COVID-19. METHODS: PubMed, EMBASE, the Cochrane Library, and three electronic Chinese databases were searched from December 1, 2019 to April 29, 2020. Eligible studies reporting potential predictors of mortality in patients with COVID-19 were identified. Unadjusted prognostic effect estimates were pooled using the random-effects model if data from at least two studies were available. Adjusted prognostic effect estimates were presented by qualitative analysis. RESULTS: Thirty-six observational studies were identified, of which 27 were included in the meta-analysis. A total of 106 potential risk factors were tested, and the following important predictors were associated with mortality: advanced age, male sex, current smoking status, preexisting comorbidities (especially chronic kidney, respiratory, and cardio-cerebrovascular diseases), symptoms of dyspnea, complications during hospitalization, corticosteroid therapy and a severe condition. Additionally, a series of abnormal laboratory biomarkers of hematologic parameters, hepatorenal function, inflammation, coagulation, and cardiovascular injury were also associated with fatal outcome. CONCLUSION: We identified predictors of mortality in patients with COVID-19. These findings could help healthcare providers take appropriate measures and improve clinical outcomes in such patients.

Infections at the nexus of metabolic-associated fatty liver disease.

Metabolic-associated fatty liver disease (MAFLD) is a chronic liver disease that affects about a quarter of the world population. MAFLD encompasses different disease stadia ranging from isolated liver steatosis to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma. Although MAFLD is considered as the hepatic manifestation of the metabolic syndrome, multiple concomitant disease-potentiating factors can accelerate disease progression. Among these risk factors are diet, lifestyle, genetic traits, intake of steatogenic drugs, male gender and particular infections. Although infections often outweigh the development of fatty liver disease, pre-existing MAFLD could be triggered to progress towards more severe disease stadia. These combined disease cases might be underreported because of the high prevalence of both MAFLD and infectious diseases that can promote or exacerbate fatty liver disease development. In this review, we portray the molecular and cellular mechanisms by which the most relevant viral, bacterial and parasitic infections influence the progression of fatty liver disease and steatohepatitis. We focus in particular on how infectious diseases, including coronavirus disease-19, hepatitis C, acquired immunodeficiency syndrome, peptic ulcer and periodontitis, exacerbate MAFLD. We specifically underscore the synergistic effects of these infections with other MAFLD-promoting factors.

Differential association between inflammatory cytokines and multiorgan dysfunction in COVID-19 patients with obesity.

To investigate the mechanisms underlying the SARS-CoV-2 infection severity observed in patients with obesity, we performed a prospective study of 51 patients evaluating the impact of multiple immune parameters during 2 weeks after admission, on vital organs' functions according to body mass index (BMI) categories. High-dimensional flow cytometric characterization of immune cell subsets was performed at admission, 30 systemic cytokines/chemokines levels were sequentially measured, thirteen endothelial markers were determined at admission and at the zenith of the cytokines. Computed tomography scans on admission were quantified for lung damage and hepatic steatosis (n = 23). Abnormal BMI (> 25) observed in 72.6% of patients, was associated with a higher rate of intensive care unit hospitalization (p = 0.044). SARS-CoV-2 RNAaemia, peripheral immune cell subsets and cytokines/chemokines were similar among BMI groups. A significant association between inflammatory cytokines and liver, renal, and endothelial dysfunctions was observed only in patients with obesity (BMI > 30). In contrast, early signs of lung damage (ground-glass opacity) correlated with Th1/M1/inflammatory cytokines only in normal weight patients. Later lesions of pulmonary consolidation correlated with BMI but were independent of cytokine levels. Our study reveals distinct physiopathological mechanisms associated with SARS-CoV-2 infection in patients with obesity that may have important clinical implications.

Hepatic Manifestations of Nonhepatotropic Infectious Agents Including Severe Acute Respiratory Syndrome Coronavirus-2, Adenovirus, Herpes Simplex Virus, and Coxiella burnetii.

Nonhepatotropic viruses such as adenovirus, herpes simplex virus, flaviviruses, filoviruses, and human herpes virus, and bacteria such as Coxiella burnetii, can cause liver injury mimicking acute hepatitis. Most of these organisms cause a self-limited infection. However, in immunocompromised patients, they can cause severe hepatitis or in some cases fulminant hepatic failure requiring an urgent liver transplant. Hepatic dysfunction is also commonly seen in patients with severe acute respiratory syndrome coronavirus-2 infection. Patients with preexisting liver diseases are likely at risk for severe coronavirus disease 2019 (COVID-19) and may be associated with poor outcomes.

Elevated serum ferritin level effectively discriminates severity illness and liver injury of coronavirus disease 2019 pneumonia.

AIM: Ferritin is a hepatic protein that plays vital roles in diagnosing and predicting diseases, but its potential in coronavirus disease 2019 (COVID-19) remains unknown. METHOD: We collected clinical records from 79 COVID-19 patients at Wuhan Union hospital (China). Spearman's correlation analysis, receiver operating characteristic (ROC) curve and Kaplan-Meier survival curves were employed. RESULTS: Patients with elevated ferritin levels had a higher incidence of severity illness (50.0 vs 2.9%) and liver injury (52.3 vs 20.0%) when compared with patients with normal ferritin levels (p < 0.05). Ferritin could effectively identify the severity of illness (ROC area 0.873) and liver injury (ROC area 0.752). The elevated ferritin group showed longer viral clearance time (median 16 vs 6 days, p < 0.001) and in-hospital length (median 18 vs 10 days, p < 0.001). CONCLUSIONS: It suggests that ferritin could act as an easy-to-use tool to identify liver injury and severity illness and predict the prognosis of COVID-19 patients. Intensive surveillance is necessary for patients with abnormal ferritin levels.

Clinical epidemiological analyses of overweight/obesity and abnormal liver function contributing to prolonged hospitalization in patients infected with COVID-19.

BACKGROUND/OBJECTIVES: During the 2019 coronavirus disease (COVID-19) outbreak, obesity may contribute to COVID-19 transmission and deterioration. In addition, many patients with COVID-19 infection have suffered liver damage which might contribute to a worse prognosis. We conducted a clinical epidemiological analysis to investigate the association of overweight/obesity and abnormal liver function (ALF) with hospitalized duration in patients infected with COVID-19. SUBJECTS/METHODS: Fifty-eight patients with diagnosed COVID-19 (22 women & 36 men; average age: 49.2 ± 13.1 yr) were included, and their clinical data were collected at The Second Affiliated and Yuying Children's Hospital of Wenzhou Medical University, Zhejiang. Overweight/obesity was determined as body mass index (BMI) ≥24 kg/m2, ALF was determined as alanine aminotransferase >40 U/L, and prolonged hospitalization was lasting more than the median value of the hospitalized days (19 days) in this population. RESULTS: The proportions of prolonged hospitalization were elevated in patients with overweight/obesity and ALF compared with those without overweight/obesity (62.1% versus 26.1%, P = 0.010) and those without ALF (70.6% versus 41.5%, P = 0.043). Kaplan-Meier analysis showed that the hospitalized duration was increased from the patients with neither overweight/obesity nor ALF to those with either overweight/obesity or ALF, and to those with both of overweight/obesity and ALF (mean with 95% confidence interval: 16.4 [14.5-18.3] versus 25.3 [21.6-29.1] versus 28.3 [24.6-32.0], P for trend = 0.001). Being discharged from hospital in time was inversely and independently associated with BMI (hazard ratio [HR] = 0.75, 95% CI: 0.63-0.90, P for trend = 0.002) and ALT (HR = 0.95, 95% CI: 0.92-0.99, P for trend = 0.007). CONCLUSIONS: Present findings suggested that overweight/obesity and/or ALF contributed to predicting a probability of prolonged hospitalization in patients with COVID-19 infection, to whom extra attentions and precautions should be paid during clinical treatments.

Hepatic Injury in Patients With COVID-19.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has infected over 2 million people worldwide over the course of just several months. Various studies have highlighted that patients infected with COVID-19 may develop various degrees of liver injury. Here, we discuss the impact of underlying liver disease and manifestations of hepatic injury with COVID-19. We also review mechanisms of hepatic injury. METHODS: We searched the database PubMed for all studies focused on hepatic injury in COVID-19. RESULTS: We identified 13 studies that assessed the impact of underlying liver disease in patients infected with COVID-19 (N=3046). Underlying liver disease was one of the most common known comorbid categories in patients infected with COVID-19. Overall, 25% of the patients identified from the 13 studies had hepatic injury. Twenty-one percent and 24% had elevated alanine transaminase and aspartate transaminase values, respectively. Nine percent of the patients had elevated total bilirubin values. Ten of the 13 studies assessed COVID-19 acuity with severity of hepatic injury. In 9 of the 10 studies, clinical outcomes were worse with hepatic injury. CONCLUSIONS: Liver injury is highly prevalent in patients that present with COVID-19. Since the liver is one of the most affected organs outside of the respiratory system in COVID-19, more intensive surveillance is warranted for severe cases, particularly among those with pre-existing advanced liver disease.

Clinical Features of Patients Infected With Coronavirus Disease 2019 With Elevated Liver Biochemistries: A Multicenter, Retrospective Study.

BACKGROUND AND AIMS: In December 2019, an outbreak of coronavirus disease 2019 (COVID-19) emerged in Wuhan, China. Although it has been reported that some patients with COVID-19 showed elevated liver biochemistries, there are few studies regarding the clinical features and prognosis of these patients. APPROACH AND RESULTS: In this multicenter, retrospective study, we collected data on laboratory-confirmed patients with COVID-19 from three hospitals in Wuhan, China, who died or were discharged between February 1, 2020, and February 20, 2020. Data on demographics, comorbidities, clinical symptoms, laboratory examinations on admission, complications, treatment, and outcome were collected. A total of 482 patients were enrolled in this study. Of those, 142 (29.5%) patients showed abnormal liver biochemistries on admission, and patients with elevated alanine aminotransferase, aspartate aminotransferase (AST), and total bilirubin (TBIL) accounted for 67.6%, 69.0%, and 16.2%, respectively. Those with abnormal liver biochemistries showed higher percentages of severe cases and comorbidities and were more likely to have dyspnea, chest distress or pain, and increased hemoglobin (Hb) on admission. Higher rates of complications and mortality and worse recovery when discharged were observed in patients with abnormal AST or TBIL. Multivariable regression analysis showed that chest distress or pain (odds ratio [OR], 1.765; P = 0.018), dyspnea (OR, 2.495; P = 0.001), elevated C-reactive protein level (OR, 1.007; P = 0.008), elevated white blood count (OR, 1.139; P = 0.013), and elevated Hb concentration (OR, 1.024; P = 0.001) were independent factors associated with elevated liver biochemistries in patients with COVID-19. CONCLUSIONS: Elevated liver biochemistries were common in patients with COVID-19. Patients with hypoxia or severe inflammation are more likely to experience increased liver biochemistries on admission. Those with abnormal AST or TBIL on admission are more likely to suffer from severe complications and death.

Epidemiological and clinical characteristics of 70 cases of coronavirus disease and concomitant hepatitis B virus infection: A multicentre descriptive study.

The interaction between existing chronic liver diseases caused by hepatitis B virus (HBV) infection and COVID-19 has not been studied. We analysed 70 COVID-19 cases combined with HBV infection (CHI) to determine the epidemiological, clinical characteristics, treatment and outcome. We investigated clinical presentation, imaging and laboratory parameters of COVID-19 patients of seven hospitals from Jan 20 to March 20, 2020. Multivariate analysis was used to analyse risk factors for progression of patients with COVID-19 combined with HBV infection. Compared with COVID-19 without HBV infection (WHI) group, patients with dual infection had a higher proportion of severe/critically ill disease (32.86% vs. 15.27%, P = .000), higher levels of alanine aminotransferase (ALT), aspartate transaminase (AST) and activated partial thromboplastin (APTT) [50(28-69)vs 21(14-30), P = .000; 40(25-54) vs 23(18-30), P = .000; 34.0(27.2-38.7) vs 37.2(31.1-41.4), P = .031]. The utilization rates of Arbidol and immunoglobulin were significantly higher than those in the co-infected group [48.57% vs. 35.64%, P < .05; 21.43% vs. 8.18%, P < .001], while the utilization rate of chloroquine phosphate was lower (1.43% vs 14.00%, P < .05) in the co-infected patients group. Age and c-reactive protein (CRP) level were independent risk factors for recovery of patients with COVID-19 combined with HBV infection. The original characteristics of COVID-19 cases combined with HBV infection were higher rate of liver injury, coagulation disorders, severe/critical tendency and increased susceptibility. The elderly and patients with higher level of CRP were more likely to experience a severe outcome of COVID-19.

Hematological changes in patients with COVID­19 (Review).

In December 2019, an emergence of pneumonia was detected in patients infected with a novel coronavirus (CoV) in Wuhan (Hubei, China). The International Committee on Taxonomy of Viruses named the virus severe acute respiratory syndrome­CoV­2 and the disease CoV disease­19 (COVID­19). Patients with COVID­19 present with symptoms associated with respiratory system dysfunction and hematological changes, including lymphopenia, thrombocytopenia and coagulation disorders. However, to the best of our knowledge, the pathogenesis of COVID­19 remains unclear. Therefore, understanding the mechanisms underlying the hematological changes that manifest during COVID­19 may aid in the development of treatments and may improve patient prognosis.

Hepatic Predictors of Mortality in Severe Acute Respiratory Syndrome Coronavirus 2: Role of Initial Aspartate Aminotransferase/Alanine Aminotransferase and Preexisting Cirrhosis.

The novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is the causative agent of coronavirus disease 2019 (COVID-19). The presenting symptoms of this virus are variable, and there is an increasing body of literature on risk factors for mortality. The aim of this study was to evaluate the effect of initial aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and preexisting liver disease, including cirrhosis, in a cohort of patients admitted with COVID-19 infection at a tertiary care hospital network in the Bronx, New York. We reviewed 3,352 patients who had a positive SARS-CoV2 nasal swab, were over 18 years of age, and had an associated inpatient admission and discharge (or death) to the Montefiore Medical Center from February 28, 2020, to May 22, 2020. Of these, 39/86 (45%) patients died when the initial ALT was >5 times the upper limit of normal (ULN); 115/230 (50%) patients died when the initial AST was >3 times the ULN. The mortality of patients without preexisting liver disease was 26.6% compared to a mortality rate of 29.5% in patients with liver disease. Subgroup analysis showed a mortality of 36.1% in the patients with cirrhosis. Cirrhosis conferred a hazard ratio for mortality of 1.67 (95% confidence interval, 1.09, 2.55; P = 0.019). The baseline Model for End-Stage Liver Disease score was not prognostic in the cirrhosis cohort. There was no statistical difference between mortality in patients with a history of compensated or decompensated cirrhosis. The most common cause of death in the cirrhosis cohort was respiratory failure. Conclusion: COVID-19 hepatitis may lead to poor outcomes in patients who are hospitalized for the disease. Patients with cirrhosis are at a higher risk of COVID-19-related mortality.

ACE2: from protection of liver disease to propagation of COVID-19.

Twenty years ago, the discovery of angiotensin-converting enzyme 2 (ACE2) was an important breakthrough dramatically enhancing our understanding of the renin-angiotensin system (RAS). The classical RAS is driven by its key enzyme ACE and is pivotal in the regulation of blood pressure and fluid homeostasis. More recently, it has been recognised that the protective RAS regulated by ACE2 counterbalances many of the deleterious effects of the classical RAS. Studies in murine models demonstrated that manipulating the protective RAS can dramatically alter many diseases including liver disease. Liver-specific overexpression of ACE2 in mice with liver fibrosis has proved to be highly effective in antagonising liver injury and fibrosis progression. Importantly, despite its highly protective role in disease pathogenesis, ACE2 is hijacked by SARS-CoV-2 as a cellular receptor to gain entry to alveolar epithelial cells, causing COVID-19, a severe respiratory disease in humans. COVID-19 is frequently life-threatening especially in elderly or people with other medical conditions. As an unprecedented number of COVID-19 patients have been affected globally, there is an urgent need to discover novel therapeutics targeting the interaction between the SARS-CoV-2 spike protein and ACE2. Understanding the role of ACE2 in physiology, pathobiology and as a cellular receptor for SARS-CoV-2 infection provides insight into potential new therapeutic strategies aiming to prevent SARS-CoV-2 infection related tissue injury. This review outlines the role of the RAS with a strong focus on ACE2-driven protective RAS in liver disease and provides therapeutic approaches to develop strategies to prevent SARS-CoV-2 infection in humans.

Impact of liver injury on the severity of COVID-19: a systematic review with meta-analysis.

BACKGROUND AND AIMS: SARS-CoV-2 is mainly a respiratory virus that has relevant systemic effects. We assessed the impact of baseline liver function (aspartate aminotransferase [AST], alanine aminotransferase [ALT], bilirubin) on COVID-19-related outcomes, including mortality, intensive care unit (ICU) admissions, and non-fatal severe complications. METHODS: after a systematic review of the relevant studies the odds ratio (OR), mean difference, sensitivity, specificity, and both positive and negative likelihood ratios were calculated for the prediction of relevant COVID-19 outcomes by performing a meta-analysis using fixed and random effects models. A Fagan nomogram was used to assess clinical usefulness. Heterogeneity was explored by sensitivity analysis and univariate meta-regression. RESULTS: twenty-six studies were included (22 studies and 5,271 patients for AST, 20 studies and 5,440 subjects for ALT, and nine studies and 3,542 patients for bilirubin). The outcomes assessed by these studies were: survival (n = 8), ICU admission (n = 4), and non-fatal severe complications (n = 16). AST > upper limit of normal (ULN) (OR: 3.10 [95 % CI, 2.61-3.68]), ALT > ULN (OR: 2.15 [95 % CI, 1.43-3.23]), and bilirubin > ULN (OR: 2.78 [95 % CI, 1.88-4.13]) were associated with an increased prevalence of severe complications with a specificity of 78 %, 77 %, and 94 %, respectively. The mean difference between mild and severe COVID-19 was 10.7 U/l (95 % CI, 5.8-15.6) for AST, 8 U/l (95 % CI, 1.0-15) for ALT, and 0.3 mg/dl (95 % CI, 0.16-0.45) for bilirubin. CONCLUSIONS: patients showing liver injury had a significantly higher risk of developing severe COVID-19 as compared to those with normal liver function tests at admission. We should include the assessment of AST, ALT, and total bilirubin (TB) routinely in the workup of patients affected by SARS-CoV-2 in order to predict those at risk of developing COVID-19-related outcomes.