COVID-19 and liver disease: mechanistic and clinical perspectives

Our understanding of the hepatic consequences of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its resultant coronavirus disease 2019 (COVID-19) has evolved rapidly since the onset of the pandemic. In this Review, we discuss the hepatotropism of SARS-CoV-2, including the differential expression of viral receptors on liver cell types, and we describe the liver histology features present in patients with COVID-19. We also provide an overview of the pattern and relevance of abnormal liver biochemistry during COVID-19 and present the possible underlying direct and indirect mechanisms for liver injury. Furthermore, large international cohorts have been able to characterize the disease course of COVID-19 in patients with pre-existing chronic liver disease. Patients with cirrhosis have particularly high rates of hepatic decompensation and death following SARS-CoV-2 infection and we outline hypotheses to explain these findings, including the possible role of cirrhosis-associated immune dysfunction. This finding contrasts with outcome data in pharmacologically immunosuppressed patients after liver transplantation who seem to have comparatively better outcomes from COVID-19 than those with advanced liver disease. Finally, we discuss the approach to SARS-CoV-2 vaccination in patients with cirrhosis and after liver transplantation and predict how changes in social behaviours and clinical care pathways during the pandemic might lead to increased liver disease incidence and severity. © 2021, Springer Nature Limited

RAMP2 influences glucagon receptor pharmacology via trafficking and signaling

Endogenous satiety hormones provide an attractive target for obesity drugs. Glucagon causes weight loss by reducing food intake and increasing energy expenditure. To further understand the cellular mechanisms by which glucagon and related ligands activate the glucagon receptor (GCGR), we investigated the interaction of the GCGR with receptor activity modifying protein (RAMP)2, a member of the family of receptor activity modifying proteins. We used a combination of competition binding experiments, cell surface enzyme-linked immunosorbent assay, functional assays assessing the Gαs and Gαq pathways and β-arrestin recruitment, and small interfering RNA knockdown to examine the effect of RAMP2 on the GCGR. Ligands tested were glucagon; glucagonlike peptide-1 (GLP-1); oxyntomodulin; and analog G(X), a GLP-1/glucagon coagonist developed in-house. Confocal microscopy was used to assess whether RAMP2 affects the subcellular distribution of GCGR. Here we demonstrate that coexpression of RAMP2 and the GCGR results in reduced cell surface expression of the GCGR. This was confirmed by confocal microscopy, which demonstrated that RAMP2 colocalizes with the GCGR and causes significant GCGR cellular redistribution. Furthermore, the presence of RAMP2 influences signaling through the Gαs and Gαq pathways, as well as recruitment of β-arrestin. This work suggests that RAMP2 may modify the agonist activity and trafficking of the GCGR, with potential relevance to production of new peptide analogs with selective agonist activities

Regional variation in characteristics of patients with decompensated cirrhosis admitted to hospitals in the UK

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Determining risk factors for mortality in liver transplant patients with COVID-19

We read with great interest the Correspondence from Bhoori and colleagues1 describing the effect of coronavirus disease 2019 (COVID-19) on their centre's adult liver transplant population.1 Within their cohort of over 150 transplant recipients, the authors identified six patients with COVID-19, including three resulting deaths. Each of those who died was transplanted over 10 years previously and were older than 65 years, male, overweight, and had hypertension and diabetes. The authors speculated as to whether these characteristics might be major risk factors for mortality

Adopting a Citizen Science Approach in Translational Experimental Medicine Research in Non-Alcoholic Fatty Liver Disease: A Study Protocol

Citizen science approaches are widely and successfully used in biological, environmental, and ecological sciences; however, they are rarely applied in other domains, such as translational health research, notably in the field of liver disease and metabolism. We have designed a study that aims to explore the application of the citizen science approach in a translational experimental medicine study on non-alcoholic fatty liver disease (NAFLD) and a 12-week lifestyle and weight loss program. In this methodological paper, we describe the process of involving citizen scientists in the study. We will recruit a convenience sample of 31 participants (with and without NAFLD) and a half-dozen citizen scientists (members of the public). Citizen scientists will work alongside clinical and non-clinical researchers in a translational experimental medicine study on NAFLD. Citizen scientists will be involved in the co-design and/or review of data collection tools (e.g., semi-structured open-ended questionnaire surveys and semi-structured wellbeing diaries completed by the participants), co-analysis of data on participants’ experiences and motivations, co-drafts of research findings and papers, and suggestions for policy recommendations. Citizen scientists will be trained in the research tasks they will undertake, and will be either co-authors or their names will be mentioned in the acknowledgements in research paper(s) based on the level of research contributions. Lessons learned from implementing citizen science in this study will help to reveal the advantages, limitations, and implications of involving citizen scientists in the translational medicine research. Knowing citizen scientists’ motivations, expectations, training needs, and overall experience of involvement in this study could provide insights, which could inform the planning and conduct of future translational research studies. Involving citizen scientists in translational medicine research is an important step in extending research opportunities for members of the public; however, there may be methodological challenges, which may be identified and resolved by more research studies

SARS-CoV-2 Infections Among Patients With Liver Disease and Liver Transplantation Who Received COVID-19 Vaccination.

Many safe and effective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations dramatically reduce risks of coronavirus disease 2019 (COVID-19) complications and deaths. We aimed to describe cases of SARS-CoV-2 infection among patients with chronic liver disease (CLD) and liver transplant (LT) recipients with at least one prior COVID-19 vaccine dose. The SECURE-Liver and COVID-Hep international reporting registries were used to identify laboratory-confirmed COVID-19 in CLD and LT patients who received a COVID-19 vaccination. Of the 342 cases of lab-confirmed SARS-CoV-2 infections in the era after vaccine licensing, 40 patients (21 with CLD and 19 with LT) had at least one prior COVID-19 vaccination, including 12 who were fully vaccinated (≥2 weeks after second dose). Of the 21 patients with CLD (90% with cirrhosis), 7 (33%) were hospitalized, 1 (5%) was admitted to the intensive care unit (ICU), and 0 died. In the LT cohort (n = 19), there were 6 hospitalizations (32%), including 3 (16%) resulting in mechanical ventilation and 2 (11%) resulting in death. All three cases of severe COVID-19 occurred in patients who had a single vaccine dose within the last 1-2 weeks. In contemporary patients with CLD, rates of symptomatic infection, hospitalization, ICU admission, invasive ventilation, and death were numerically higher in unvaccinated individuals. Conclusion: This case series demonstrates the potential for COVID-19 infections among patients with CLD and LT recipients who had received the COVID-19 vaccination. Vaccination against SARS-CoV-2 appears to result in favorable outcomes as attested by the absence of mechanical ventilation, ICU, or death among fully vaccinated patients

PYY plays a key role in the resolution of diabetes following bariatric surgery in humans.

BACKGROUND: Bariatric surgery leads to early and long-lasting remission of type 2 diabetes (T2D). However, the mechanisms behind this phenomenon remain unclear. Among several factors, gut hormones are thought to be crucial mediators of this effect. Unlike GLP-1, the role of the hormone peptide tyrosine tyrosine (PYY) in bariatric surgery in humans has been limited to appetite regulation and its impact on pancreatic islet secretory function and glucose metabolism remains under-studied. METHODS: Changes in PYY concentrations were examined in obese patients after bariatric surgery and compared to healthy controls. Human pancreatic islet function was tested upon treatment with sera from patients before and after the surgery, in presence or absence of PYY. Alterations in intra-islet PYY release and insulin secretion were analysed after stimulation with short chain fatty acids (SCFAs), bile acids and the cytokine IL-22. FINDINGS: We demonstrate that PYY is a key effector of the early recovery of impaired glucose-mediated insulin and glucagon secretion in bariatric surgery. We establish that the short chain fatty acid propionate and bile acids, which are elevated after surgery, can trigger PYY release not only from enteroendocrine cells but also from human pancreatic islets. In addition, we identify IL-22 as a new factor which is modulated by bariatric surgery in humans and which directly regulates PYY expression and release. INTERPRETATION: This study shows that some major metabolic benefits of bariatric surgery can be emulated ex vivo. Our findings are expected to have a direct impact on the development of new non-surgical therapy for T2D correction