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Introduction Bacterial translocation and endotoxaemia are important in the pathogenesis of neutrophil dysfunction in cirrhosis. At present, it is not clear whether systemic endotoxaemia occurs as a consequence of a defect at the gut barrier interface or diminished hepatic function and associated portosystemic shunting. Aim The aims of this study were (1) to quantify the degree of portal endotoxaemia and the contribution of the liver in the regulation of systemic endotoxin (ET) levels, (2) to determine intestinal production of cytokines and adhesion molecules and (3) to determine whether the portal and hepatic milieu modulates neutrophil function. Method 12 patients with cirrhosis (54±3.2 yr, Pugh 10.2±1.0, eight male, four female) were studied prior to and 1-h after TIPSS insertion. Blood was sampled from the artery, hepatic vein (HV), portal vein (PV) and its tributaries. PV blood was sampled before insertion of the TIPSS. Endotoxin (ET) (LAL assay), LBP, BPI, IL-6, IL-10, TNFR55, TNFR75, sICAM and sELAM (using ELISA) were measured. Neutrophil respiratory burst and phagocytosis was measured using FACS in neutrophils derived from the HV and PV, prior to and following cross-incubation with PV and HV plasma, respectively. Results TIPSS insertion resulted in a significant increase in arterial ET levels from 0.08±0.02 to 0.19±0.02 EU/ml (p=0.0001). Mean ET levels in the PV and HV pre-TIPSS insertion were 0.22±0.02 and 0.04±0.02 EU/ml respectively. Transintestinal (TI) and transhepatic (TH) ET fractional extraction (FE) rates were 2.7±0.7 and −0.5±0.06, respectively. HV neutrophil resting burst was significantly increased from 52±5.3 to 78±4.5% after incubation with PV plasma (p<0.0001). Conversely PV neutrophil resting burst was significantly reduced from 85±3.5 to 60±5.3% (p<0.0001) after incubation with HV plasma. Positive intestinal FE rates were observed most markedly with BPI, IL-6 and IL-10. Neutrophil phagocytosis was reduced post-TIPSS from 66±7.5 to 42±6.5% (p=0.0004) and resting burst increased from 62±5.6 to 87±2.8% (p=0.0001). Conclusion This study provides direct evidence for portal endotoxaemia in cirrhosis. The data suggest that the liver is responsible for compartmentalising ET and associated neutrophil dysfunction within the portal circulation. Intestinal production of IL-6 and IL-10 was also demonstrated. TIPSS insertion disturbs this compartmentalisation and exposes the systemic circulation to portal endotoxaemia. Strategies to diminish portal endotoxaemia or enhance hepatic ET clearance capacity are important therapeutic targets to minimise neutrophil dysfunction in cirrhosis. [ABSTRACT FROM PUBLISHER]

Background: There is mounting evidence to suggest that high adherence to the Mediterranean diet (MedDiet) may reduce the risk of age-related diseases, including Parkinson's disease (PD). However, evidence for the role of the MedDiet in the relief of motor and non-motor symptoms in patients with PD remains limited and inconclusive. We provide a systematic review of the effects of the MedDiet on the clinical features of PD using data from randomised controlled trials (RCT) and prospective observational studies., Methods: We searched MEDLINE, EMCare, EMBASE, Scopus and PubMed from inception until June 2023. Reference lists and the grey literature were also searched. Human studies with no restriction on language or publication date, examining associations between MedDiet adherence and the symptoms of PD, were included. We employed standard methodological procedures for data extraction and evidence synthesis and used the Quality Criteria Checklist for assessing the studies included., Results: Four studies from three unique cohorts, including two observational studies (n = 1213) and one RCT (n = 70), met the inclusion criteria. Despite the short study duration reported in all included reports, high MedDiet adherence was associated with changes in the gut microbiota (e.g., increased abundance of short-chain fatty acids producers). These outcomes correlated with a significant improvement in several non-motor symptoms including cognitive dysfunction, dyspepsia and constipation. However, there were no significant changes in diarrhoea, gastrointestinal reflux, abdominal pain and motor symptoms., Conclusion: High MedDiet adherence may be associated with significant improvement in global cognition and several gastrointestinal symptoms, possibly associated to changes in gut microbiota composition. Further studies are warranted to clarify potential cause-and-effect relationships and to elucidate MedDiet impact on motor symptoms.

Objective: Targeting bacterial translocation in cirrhosis is limited to antibiotics with risk of antimicrobial resistance. This study explored the therapeutic potential of a non-absorbable, gut-restricted, engineered carbon bead adsorbent, Yaq-001 in models of cirrhosis and acute-on-chronic liver failure (ACLF) and, its safety and tolerability in a clinical trial in cirrhosis., Design: Performance of Yaq-001 was evaluated in vitro . Two-rat models of cirrhosis and ACLF, (4 weeks, bile duct ligation with or without lipopolysaccharide), receiving Yaq-001 for 2 weeks; and two-mouse models of cirrhosis (6-week and 12-week carbon tetrachloride (CCl4)) receiving Yaq-001 for 6 weeks were studied. Organ and immune function, gut permeability, transcriptomics, microbiome composition and metabolomics were analysed. The effect of faecal water on gut permeability from animal models was evaluated on intestinal organoids. A multicentre, double-blind, randomised, placebo-controlled clinical trial in 28 patients with cirrhosis, administered 4 gr/day Yaq-001 for 3 months was performed., Results: Yaq-001 exhibited rapid adsorption kinetics for endotoxin. In vivo , Yaq-001 reduced liver injury, progression of fibrosis, portal hypertension, renal dysfunction and mortality of ACLF animals significantly. Significant impact on severity of endotoxaemia, hyperammonaemia, liver cell death, systemic inflammation and organ transcriptomics with variable modulation of inflammation, cell death and senescence in the liver, kidneys, brain and colon was observed. Yaq-001 reduced gut permeability in the organoids and impacted positively on the microbiome composition and metabolism. Yaq-001 regulated as a device met its primary endpoint of safety and tolerability in the clinical trial., Conclusions: This study provides strong preclinical rationale and safety in patients with cirrhosis to allow clinical translation., Trial Registration Number: NCT03202498., Competing Interests: Competing interests: JMacNaughtan: Shareholder in Yaqrit—no payments received; LM: Yaqrit Employee; KC: Yaqrit consultant; CM: Full-time employee of Yaqrit—salary, Share options in Yaqrit Discovery—no payment received; TA: Full-time employee of Yaqrit—Salary; MK: Full-time employee of Yaqrit—salary, Shares and Share options in Yaqrit Discovery—no payment received; DG: Share options—Yaqrit; AG: Shareholder—Yaqrit; RPM: Shareholder in Yaqrit —No payments received; SShoaie: Co-founder of Gigabiome, Bash Biotech and DAS Microbiome; JMarchesi: JMarchesi has received consultancy fees from EnteroBiotix and Cultech, and speaker fees from Falk Forum; RJ: RJ is the inventor of OPA, which has been patented by UCL and licensed to Mallinckrodt Pharma. He is also the founder of Yaqrit Discovery, Hepyx (spin out companies from University College London), and Cyberliver. He has research collaborations with Yaqrit Discovery. Yaq-001 was licensed by Yaqrit from UCL., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Caudo-rostral migration of pathological forms of α-synuclein from the gut to the brain is proposed as an early feature in Parkinson's disease pathogenesis, but the underlying mechanisms remain unknown. Intestinal epithelial enteroendocrine cells sense and respond to numerous luminal signals, including bacterial factors, and transmit this information to the brain via the enteric nervous system and vagus nerve. There is evidence that gut bacteria composition and their metabolites change in Parkinson's disease patients, and these alterations can trigger α-synuclein pathology in animal models of the disorder. Here, we investigated the effect of toll-like receptor and free fatty acid receptor agonists on the intracellular level of α-synuclein and its release using mouse secretin tumour cell line 1 enteroendocrine cells. Secretin tumour cell line 1 enteroendocrine cells were treated for 24 or 48 h with toll-like receptor agonists (toll-like receptor 4 selective lipopolysaccharide; toll-like receptor 2 selective Pam3CysSerLys4) and the free fatty acid receptor 2/3 agonists butyrate, propionate and acetate. The effect of selective receptor antagonists on the agonists' effects after 24 hours was also investigated. The level of α-synuclein protein was measured in cell lysates and cell culture media by western blot and enzyme-linked immunosorbent assay. The level of α-synuclein and tumour necrosis factor messenger RNA was measured by quantitative reverse transcription real-time polymerase chain reaction. Stimulation of secretin tumour cell line 1 enteroendocrine cells for 24 and 48 hours with toll-like receptor and free fatty acid receptor agonists significantly increased the amount of intracellular α-synuclein and the release of α-synuclein from the cells into the culture medium. Both effects were significantly reduced by antagonists selective for each receptor. Toll-like receptor and free fatty acid receptor agonists also significantly increased tumour necrosis factor transcription, and this was effectively inhibited by corresponding antagonists. Elevated intracellular α-synuclein increases the likelihood of aggregation and conversion to toxic forms. Factors derived from bacteria induce α-synuclein accumulation in secretin tumour cell line 1 enteroendocrine cells. Here, we provide support for a mechanism by which exposure of enteroendocrine cells to specific bacterial factors found in Parkinson's disease gut dysbiosis might facilitate accumulation of α-synuclein pathology in the gut., Competing Interests: The authors report no competing interests or relevant disclosures., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain.)

Recent attention has highlighted the importance of oral microbiota in human health and disease, e.g., in Parkinson's disease, notably using shotgun metagenomics. One key aspect for efficient shotgun metagenomic analysis relies on optimal microbial sampling and DNA extraction, generally implementing commercial solutions developed to improve sample collection and preservation, and provide high DNA quality and quantity for downstream analysis. As metagenomic studies are today performed on a large number of samples, the next evolution to increase study throughput is with DNA extraction automation. In this study, we proposed a semi-automated DNA extraction protocol for human salivary samples collected with a commercial kit, and compared the outcomes with the DNA extraction recommended by the manufacturer. While similar DNA yields were observed between the protocols, our semi-automated DNA protocol generated significantly higher DNA fragment sizes. Moreover, we showed that the oral microbiome composition was equivalent between DNA extraction methods, even at the species level. This study demonstrates that our semi-automated protocol is suitable for shotgun metagenomic analysis, while allowing for improved sample treatment logistics with reduced technical variability and without compromising the structure of the oral microbiome.

This review will focus on how bile acids are being used in clinical trials to treat neurological diseases due to their central involvement with the gut-liver-brain axis and their physiological and pathophysiological roles in both normal brain function and multiple neurological diseases. The synthesis of primary and secondary bile acids species and how the regulation of the bile acid pool may differ between the gut and brain is discussed. The expression of several bile acid receptors in brain and their currently known functions along with the tools available to manipulate them pharmacologically are examined, together with discussion of the interaction of bile acids with the gut microbiome and their lesser-known effects upon brain glucose and lipid metabolism. How dysregulation of the gut microbiome, aging and sex differences may lead to disruption of bile acid signalling and possible causal roles in a number of neurological disorders are also considered. Finally, we discuss how pharmacological treatments targeting bile acid receptors are currently being tested in an array of clinical trials for several different neurodegenerative diseases., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Cachexia occurs in late stages of liver cirrhosis, and a low-fat mass is potentially associated with poor outcome. This study compared different computed tomography (CT)-derived fat parameters with respect to its prognostic impact on the development of complications and death before and after liver transplantation. Between 2001 and 2014, 612 patients with liver cirrhosis without hepatocellular carcinoma listed for liver transplantation met the inclusion criteria, including abdominal CT scan (±200 days to listing). A total of 109 patients without cirrhosis served as controls. The subcutaneous fat index (SCFI), the paraspinal muscle fat index, and the visceral fat index were assessed at L3/L4 level and normalized to the height (cm 2 /m 2 ). Data were collected and analyzed retrospectively. Low SCFI was associated with a higher rate of ascites and increased C-reactive protein levels (p < 0.001). In addition, multivariate Cox regression analysis adjusting for sex, age, body mass index (BMI), and Model for End-Stage Liver Disease showed that decreasing SCFI was also associated with an increased risk of cirrhosis-related complications (p = 0.003) and death on the transplant wait list (p = 0.013). Increased paraspinal and visceral fat were not only positively correlated with creatinine levels (p < 0.001), BMI, and metabolic comorbidities (all p < 0.001) before transplantation, but also predictive for 1-year mortality after transplantation. Conclusion: The distribution of body fat is a major determinant for complications and outcome in cirrhosis before and after liver transplantation., (© 2022 The Authors. Hepatology Communications published by Wiley Periodicals LLC on behalf of American Association for the Study of Liver Diseases.)

Sarcopenia, characterized by a loss of muscle strength, quantity/quality, and physical performance is associated with increased mortality and poor clinical outcomes in concomitant presentation with liver cirrhosis (LC). A number of mechanisms are involved in sarcopenia development in LC, many of which are secondary to liver dysfunction and/or iatrogenic involvement in treating LC. Sarcopenia severity in this population appears to be affected by patient gender, as well as the primary aetiology of LC (alcohol, non-alcoholic fatty liver disease etc.) with patient demographics shifting in recent years. Clinical detection of sarcopenia in this population may involve a combination of assessment tools, in addition to measuring muscle mass and strength separately. Muscle mass may be assessed using radiography, bioelectric impedance, ultrasound, or anthropometrics. Hand-grip strength, on the other hand, may be a useful tool for evaluating muscle strength. The role of malnutrition in sarcopenia is also a relevant factor, and screening tools such as MELD and SARC-F may be clinically useful tools for more complete diagnosis of sarcopenia in these patients. Myostatin and titin-N may represent potential diagnostic biomarkers. Lastly, physical activity and nutrition remain key elements of treatment. Further research is being conducted regarding the role of resistance vs aerobic exercise as well as the function of complementary nutrition. Continued study into the role of nutrition, physical activity and other complementary therapies will be important future endeavours in the treatment of sarcopenia in LC., (Copyright © 2022. Published by Elsevier Inc.)

Objective: Catheter/cannula-bloodstream infection (CBI) has been proposed as a marker of the quality of care provided to patients receiving parenteral nutrition (PN). However, surveillance criteria for CBI are variable, inconsistent, and sometimes confusing and impractical. Surveillance criteria were developed to simply and accurately demonstrate the presence or absence of CBI. The aim of this study was to establish a simple and valid surveillance tool, with consideration of changes in vital signs, to identify CBI in patients receiving PN., Methods: Adult (≥18 y) inpatients prescribed PN at a single large teaching hospital were recruited between October 11, 2017 and November 16, 2018. Common clinical and laboratory criteria, including blood culture, associated with 100 consecutive PN episodes associated with suspected CBI were examined for potential predictive markers of CBI. Using binary logistic regression, criteria were incorporated into an instrument that was validated against a reference classification of CBI established by an expert multidisciplinary group., Results: The reference classification comprised 12 PN episodes with CBI and 88 without. Abnormal vital signs did not significantly predict CBI, but resolution of fever (≥38°C) and low systolic blood pressure (<100 mm Hg) in response to a specific treatment for CBI (line removal/antibiotics) did. Two other criteria were also significant predictors: positive blood culture; and absence of an alternative source that could explain the septic episode other than the catheter/cannula supplying PN. These two criteria together with a positive response to treatment (temperature and/or blood pressure, incorporated into a single binary variable), resulted in 100% correct CBI classification (100% sensitivity, 100% specificity, and 1.000 area under the curve in receiver operating characteristic analysis). All criteria could be retrospectively extracted from the medical records of all PN episodes., Conclusion: A CBI tool shows promise as a surveillance instrument for benchmarking and interinstitutional comparisons of the care received by hospitalized patients given PN., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Acute-on-chronic liver failure (ACLF) is characterized predominantly by non-apoptotic forms of hepatocyte cell death. Necroptosis is a form of programmed lytic cell death in which receptor interacting protein kinase (RIPK) 1, RIPK3 and phosphorylated mixed lineage kinase domain-like (pMLKL) are key components. This study was performed to determine the role of RIPK1 mediated cell death in ACLF. RIPK3 plasma levels and hepatic expression of RIPK1, RIPK3, and pMLKL were measured in healthy volunteers, stable patients with cirrhosis, and in hospitalized cirrhotic patients with acutely decompensated cirrhosis, with and without ACLF (AD). The role of necroptosis in ACLF was studied in two animal models of ACLF using inhibitors of RIPK1, necrostatin-1 (NEC-1) and SML2100 (RIPA56). Plasma RIPK3 levels predicted the risk of 28- and 90-day mortality (AUROC, 0.653 (95%CI 0.530-0.776), 0.696 (95%CI 0.593-0.799)] and also the progression of patients from no ACLF to ACLF [0.744 (95%CI 0.593-0.895)] and the results were validated in a 2 nd patient cohort. This pattern was replicated in a rodent model of ACLF that was induced by administration of lipopolysaccharide (LPS) to bile-duct ligated rats and carbon tetrachloride-induced fibrosis mice administered galactosamine (CCL 4 /GalN). Suppression of caspase-8 activity in ACLF rodent model was observed suggesting a switch from caspase-dependent cell death to necroptosis. NEC-1 treatment prior to administration of LPS significantly reduced the severity of ACLF manifested by reduced liver, kidney, and brain injury mirrored by reduced hepatic and renal cell death. Similar hepato-protective effects were observed with RIPA56 in a murine model of ACLF induced by CCL 4 /GalN. These data demonstrate for the first time the importance of RIPK1 mediated cell death in human and rodent ACLF. Inhibition of RIPK1 is a potential novel therapeutic approach to prevent progression of susceptible patients from no ACLF to ACLF., (© 2021. The Author(s).)

Gastrointestinal disorders are one of the most significant non-motor problems affecting people with Parkinson disease (PD). Pathogenetically, the gastrointestinal tract has been proposed to be the initial site of pathological changes in PD. Intestinal inflammation and alterations in the gut microbiota may contribute to initiation and progression of pathology in PD. However, the mechanisms underlying this "gut-brain" axis in PD remain unclear. PD patients can display a large variety of gastrointestinal symptoms, leading to reduced quality of life and psychological distress. Gastrointestinal disorders can also limit patients' response to medications, and consequently negatively impact on neurological outcomes. Despite an increasing research focus, gastrointestinal disorders in PD remain poorly understood and their clinical management often suboptimal. This review summarises our understanding of the relevance of the "gut-brain" axis to the pathogenesis of PD, discusses the impact of gastrointestinal disorders in patients with PD, and provides clinicians with practical guidance to their management.

Background & Aims: Acute-on-chronic liver failure (ACLF) is characterised by organ failure(s), high short-term mortality, and, pathophysiologically, deranged inflammatory responses. The extracellular matrix (ECM) is critically involved in regulating the inflammatory response. This study aimed to determine alterations in biomarkers of ECM turnover in ACLF and their association with inflammation, organ failures, and mortality., Methods: We studied 283 patients with cirrhosis admitted for acute decompensation (AD) with or without ACLF, 64 patients with stable cirrhosis, and 30 healthy controls. A validation cohort (25 ACLF, 9 healthy controls) was included. Plasma PRO-C3, PRO-C4, PRO-C5, PRO-C6, and PRO-C8 ( i.e. collagen type III-VI and VIII formation ) and C4M and C6M ( i.e. collagen type IV and VI degradation ) were measured. Immunohistochemistry of PRO-C6 was performed on liver biopsies (AD [n = 7], ACLF [n = 5]). A competing-risk regression analysis was performed to explore the prognostic value of biomarkers of ECM turnover with 28- and 90-day mortality., Results: PRO-C3 and PRO-C6 were increased in ACLF compared to AD ( p  = 0.089 and p <0.001, respectively), whereas collagen degradation markers C4M and C6M were similar. Both PRO-C3 and PRO-C6 were strongly associated with liver function and inflammatory markers. Only PRO-C6 was associated with extrahepatic organ failures and 28- and 90-day mortality (hazard ratio [HR; on log-scale] 6.168, 95% CI 2.366-16.080, p <0.001, and 3.495, 95% CI 1.509-8.093, p  = 0.003, respectively). These findings were consistent in the validation cohort. High PRO-C6 expression was observed in liver biopsies of patients with ACLF., Conclusions: This study shows, for the first time, evidence of severe net interstitial collagen deposition in ACLF and makes the novel observation of the association between PRO-C6 and (extrahepatic) organ failures and mortality. Further studies are needed to define the pathogenic significance of these observations., Lay Summary: This study describes a disrupted turnover of collagen type III and VI in Acute-on-chronic liver failure (ACLF). Plasma biomarkers of these collagens (PRO-C3 and PRO-C6) are associated with the severity of liver dysfunction and inflammation. PRO-C6, also known as the hormone endotrophin, has also been found to be associated with multi-organ failure and prognosis in acute decompensation and ACLF., Competing Interests: AJCK has none to declare. SG has none to declare. EA has none to declare. ID is a full-time employee at Takeda Pharmaceuticals International Co. IL is a full-time employee at Nordic Bioscience. AH has none to declare. SHN is a full-time employee at Nordic Bioscience. MJN is a full-time employee at Nordic Bioscience. HG received an investigator-initiated research grant from Intercept and research grants from AbbVie, ADS AIPHIA Development Services AG (Switzerland), ARLA Food for Health, and the NOVO Nordisk Foundation. HG is on an advisory board at Ipsen. ÀA has none to declare. DY is a full-time employee at Takeda Pharmaceuticals International Co. JM is a co-founder of Yaqrit Ltd. RPM has research collaboration with Yaqrit Ltd., of which he is a co-founder. He also has research collaborations with UCL spin-out Hepyx Ltd. and with Cyberliver Limited. He also has provided a consultancy role to Inventiva Pharmaceuticals. SM has none to declare. FA has none to declare. RM has none to declare. VA is a member of the Yaqrit Scientific Advisory Board. In 2016–2020, PA was on the Biovie Advisory Board and filed a patent application; in 2014–2020, he was invited as a speaker by and received a travel grant from CSL Behring; and in 2018–2019, he was on the Advisory Board at Ferring. DJL is a full-time employee and stockholder at Nordic Bioscience. WT is a full-time employee at Takeda Pharmaceuticals International Co. MAK is a full-time employee and stockholder at Nordic Bioscience. RJ has research collaborations with Yaqrit and Takeda. RJ is the inventor of OPA, which has been patented by the University College London and licensed to Mallinckrodt Pharma. He is also a founder of Yaqrit Ltd., a spinout company from the University College London. He has also co-founded Hepyx Ltd. and Cyberliver Ltd. Please refer to the accompanying ICMJE disclosure forms for further details., (© 2021 The Author(s).)

Cirrhosis - the common end-stage of chronic liver disease - is associated with a cascade of events, of which intestinal bacterial overgrowth and dysbiosis are central. Bacterial toxins entering the portal or systemic circulation can directly cause hepatocyte death, while dysbiosis also affects gut barrier function and increases bacterial translocation, leading to infections, systemic inflammation and vasodilation, which contribute to acute decompensation and organ failure. Acute decompensation and its severe forms, pre-acute-on-chronic liver failure (ACLF) and ACLF, are characterised by sudden organ dysfunction (and failure) and high short-term mortality. Patients with pre-ACLF and ACLF present with high-grade systemic inflammation, usually precipitated by proven bacterial infection and/or severe alcoholic hepatitis. However, no precipitant is identified in 30% of these patients, in whom bacterial translocation from the gut microbiota is assumed to be responsible for systemic inflammation and decompensation. Different microbiota profiles may influence the rate of decompensation and thereby outcome in these patients. Thus, targeting the microbiota is a promising strategy for the prevention and treatment of acute decompensation, pre-ACLF and ACLF. Approaches include the use of antibiotics such as rifaximin, faecal microbial transplantation and enterosorbents (e.g. Yaq-001), which bind microbial factors without exerting a direct effect on bacterial growth kinetics. This review focuses on the role of microbiota in decompensation and strategies targeting microbiota to prevent acute decompensation., Competing Interests: Conflict of interest J.T. has received speaking and/or consulting fees from Gore, Bayer, Alexion, MSD, Gilead, Intercept, Norgine, Grifols, Versantis, and Martin Pharmaceutical. J.M. is a co-founder of Yaqrit Limited and has received speaker fees from Norgine and Yakult Europe. B.S. has been consulting for Ferring Research Institute, Intercept Pharmaceuticals, HOST Therabiomics, Mabwell Therapeutics and Patara Pharmaceuticals. B.S.’s institution UC San Diego has received grant support from BiomX, NGM Biopharmaceuticals, CymaBay Therapeutics, Synlogic Operating Company and Axial Biotherapeutics. D.L.S. has been consulting for Norgine, Kaleido Biosciences, Shionogi and Mallinckrodt Pharmaceuticals and has undertaken paid lectures for Norgine, Alfa Sigma and Falk Pharma. D.L.S’s institution King’s College London has received grant support from Norgine. J.S.B. has been an advisor to Valeant, Norgine, Kaleido and Takeda and his institution has received support from Bausch Health, Kaleido, Grifols and Mallinckrodt pharmaceuticals. Please refer to the accompanying ICMJE disclosure forms for further details., (Copyright © 2020 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

The coronavirus (COVID-19) pandemic has disrupted clinical trials globally, with unique implications for research into the human gut microbiome. In this mini-review, we explore the direct and indirect influences of the pandemic on the gut microbiome and how these can affect research and clinical trials. We explore the direct bidirectional relationships between the COVID-19 virus and the gut and lung microbiomes. We then consider the significant indirect effects of the pandemic, such as repeated lockdowns, increased hand hygiene, and changes to mood and diet, that could all lead to longstanding changes to the gut microbiome at an individual and a population level. Together, these changes may affect long term microbiome research, both in observational as well as in population studies, requiring urgent attention. Finally, we explore the unique implications for clinical trials using faecal microbiota transplants (FMT), which are increasingly investigated as potential treatments for a range of diseases. The pandemic introduces new barriers to participation in trials, while the direct and indirect effects laid out above can present a confounding factor. This affects recruitment and sample size, as well as study design and statistical analyses. Therefore, the potential impact of the pandemic on gut microbiome research is significant and needs to be specifically addressed by the research community and funders., Competing Interests: JMc holds shares in and is an employee of EnteroBiotix Limited. He is a named inventor on patents relating to the gut microbiome. JMa holds shares in Yaqrit Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Burchill, Lymberopoulos, Menozzi, Budhdeo, McIlroy, Macnaughtan and Sharma.)

(1) Background: Intestinal failure-associated liver disease (IFALD) in adults is characterized by steatosis with variable progression to fibrosis/cirrhosis. Reference standard liver biopsy is not feasible for all patients, but non-invasive serological and quantitative MRI markers for diagnosis/monitoring have not been previously validated. Here, we examine the potential of serum scores and feasibility of quantitative MRI used in non-IFALD liver diseases for the diagnosis of IFALD steatosis; (2) Methods: Clinical and biochemical parameters were used to calculate serum scores in patients on home parenteral nutrition (HPN) with/without IFALD steatosis. A sub-group underwent multiparameter quantitative MRI measurements of liver fat fraction, iron content, tissue T1, liver blood flow and small bowel motility; (3) Results: Compared to non-IFALD ( n = 12), patients with IFALD steatosis ( n = 8) demonstrated serum score elevations in Enhanced Liver Fibrosis ( p = 0.032), Aspartate transaminase-to-Platelet Ratio Index ( p < 0.001), Fibrosis-4 Index ( p = 0.010), Forns Index ( p = 0.001), Gamma-glutamyl transferase-to-Platelet Ratio Index ( p = 0.002) and Fibrosis Index ( p = 0.001). Quantitative MRI scanning was feasible in all 10 sub-group patients. Median liver fat fraction was higher in IFALD steatosis patients (10.9% vs 2.1%, p = 0.032); other parameter differences were non-significant; (4) Conclusion: Serum scores used for non-IFALD liver diseases may be useful in IFALD steatosis. Multiparameter MRI is feasible in patients on HPN.