René Fahrner

The Liver May Act as a Firewall Mediating Mutualism Between the Host and Its Gut Commensal Microbiota

The liver forms a firewall that protects against vascular-borne gut microbes and is commonly impaired in liver disease. Breaching Barriers Premature death from chronic liver disease is a rising global trend. Opportunistic bacterial infections caused by beneficial microbes that have breached the gut and its immune barrier often lead to death in liver cirrhosis patients. Balmer et al. now show that the liver forms a second vascular barrier for eliminating commensal bacteria that have escaped from the gut. In animal models of liver disease and gut dysfunction and in patients with nonalcoholic steatohepatitis, the liver is unable to capture escaped gut commensal bacteria, which then leak into the systemic circulation, resulting in a robust host nonmucosal immune response and the breakdown of mutualism between the host and its gut microbiota. Mutualism breakdown is an important complication of liver disease. A prerequisite for establishment of mutualism between the host and the microbial community that inhabits the large intestine is the stringent mucosal compartmentalization of microorganisms. Microbe-loaded dendritic cells trafficking through lymphatics are arrested at the mesenteric lymph nodes, which constitute the firewall of the intestinal lymphatic circulation. We show in different mouse models that the liver, which receives the intestinal venous blood circulation, forms a vascular firewall that captures gut commensal bacteria entering the bloodstream during intestinal pathology. Phagocytic Kupffer cells in the liver of mice clear commensals from the systemic vasculature independently of the spleen through the liver’s own arterial supply. Damage to the liver firewall in mice impairs functional clearance of commensals from blood, despite heightened innate immunity, resulting in spontaneous priming of nonmucosal immune responses through increased systemic exposure to gut commensals. Systemic immune responses consistent with increased extraintestinal commensal exposure were found in humans with liver disease (nonalcoholic steatohepatitis). The liver may act as a functional vascular firewall that clears commensals that have penetrated either intestinal or systemic vascular circuits.

The prognostic value of pre-operative and post-operative B-type natriuretic peptides in patients undergoing noncardiac surgery: B-type natriuretic peptide and N-terminal fragment of pro-B-type natriuretic peptide: A systematic review and individual patient data meta-analysis

OBJECTIVES The objective of this study was to determine whether measuring post-operative B-type natriuretic peptides (NPs) (i.e., B-type natriuretic peptide [BNP] and N-terminal fragment of proBNP [NT-proBNP]) enhances risk stratification in adult patients undergoing noncardiac surgery, in whom a pre-operative NP has been measured. BACKGROUND Pre-operative NP concentrations are powerful independent predictors of perioperative cardiovascular complications, but recent studies have reported that elevated post-operative NP concentrations are independently associated with these complications. It is not clear whether there is value in measuring post-operative NP when a pre-operative measurement has been done. METHODS We conducted a systematic review and individual patient data meta-analysis to determine whether the addition of post-operative NP levels enhanced the prediction of the composite of death and nonfatal myocardial infarction at 30 and ≥180 days after surgery. RESULTS Eighteen eligible studies provided individual patient data (n = 2,179). Adding post-operative NP to a risk prediction model containing pre-operative NP improved model fit and risk classification at both 30 days (corrected quasi-likelihood under the independence model criterion: 1,280 to 1,204; net reclassification index: 20%; p < 0.001) and ≥180 days (corrected quasi-likelihood under the independence model criterion: 1,320 to 1,300; net reclassification index: 11%; p = 0.003). Elevated post-operative NP was the strongest independent predictor of the primary outcome at 30 days (odds ratio: 3.7; 95% confidence interval: 2.2 to 6.2; p < 0.001) and ≥180 days (odds ratio: 2.2; 95% confidence interval: 1.9 to 2.7; p < 0.001) after surgery. CONCLUSIONS Additional post-operative NP measurement enhanced risk stratification for the composite outcomes of death or nonfatal myocardial infarction at 30 days and ≥180 days after noncardiac surgery compared with a pre-operative NP measurement alone.

Postoperative B-type Natriuretic Peptide for Prediction of Major Cardiac Events in Patients Undergoing Noncardiac Surgery: Systematic Review and Individual Patient Meta-analysis.

Background:It is unclear whether postoperative B-type natriuretic peptides (i.e., BNP and N-terminal proBNP) can predict cardiovascular complications in noncardiac surgery. Methods:The authors undertook a systematic review and individual patient data meta-analysis to determine whether postoperative BNPs predict postoperative cardiovascular complications at 30 and 180 days or more. Results:The authors identified 18 eligible studies (n = 2,051). For the primary outcome of 30-day mortality or nonfatal myocardial infarction, BNP of 245 pg/ml had an area under the curve of 0.71 (95% CI, 0.64–0.78), and N-terminal proBNP of 718 pg/ml had an area under the curve of 0.80 (95% CI, 0.77–0.84). These thresholds independently predicted 30-day mortality or nonfatal myocardial infarction (adjusted odds ratio [AOR] 4.5; 95% CI, 2.74–7.4; P < 0.001), mortality (AOR, 4.2; 95% CI, 2.29–7.69; P < 0.001), cardiac mortality (AOR, 9.4; 95% CI, 0.32–254.34; P < 0.001), and cardiac failure (AOR, 18.5; 95% CI, 4.55–75.29; P < 0.001). For greater than or equal to 180-day outcomes, natriuretic peptides independently predicted mortality or nonfatal myocardial infarction (AOR, 3.3; 95% CI, 2.58–4.3; P < 0.001), mortality (AOR, 2.2; 95% CI, 1.67–86; P < 0.001), cardiac mortality (AOR, 2.1; 95% CI, 0.05–1,385.17; P < 0.001), and cardiac failure (AOR, 3.5; 95% CI, 1.0–9.34; P = 0.022). Patients with BNP values of 0–250, greater than 250–400, and greater than 400 pg/ml suffered the primary outcome at a rate of 6.6, 15.7, and 29.5%, respectively. Patients with N-terminal proBNP values of 0–300, greater than 300–900, and greater than 900 pg/ml suffered the primary outcome at a rate of 1.8, 8.7, and 27%, respectively. Conclusions:Increased postoperative BNPs are independently associated with adverse cardiac events after noncardiac surgery.

Promotion of liver regeneration by natural killer cells in a murine model is dependent on extracellular adenosine triphosphate phosphohydrolysis

Nucleotides, such as adenosine triphosphate (ATP), are released by cellular injury, bind to purinergic receptors expressed on hepatic parenchymal and nonparenchymal cells, and modulate cellular crosstalk. Liver resection and resulting cellular stress initiate such purinergic signaling responses between hepatocytes and innate immune cells, which regulate and ultimately drive liver regeneration. We studied a murine model of partial hepatectomy using immunodeficient mice to determine the effects of natural killer (NK) cell‐mediated purinergic signaling on liver regeneration. We noted first that liver NK cells undergo phenotypic changes post‐partial hepatectomy (PH) in vivo, including increased cytotoxicity and more immature phenotype manifested by alterations in the expression of CD107a, CD27, CD11b, and CD16. Hepatocellular proliferation is significantly decreased in Rag2/common gamma‐null mice (lacking T, B, and NK cells) when compared to wildtype and Rag1‐null mice (lacking T and B cells but retaining NK cells). Extracellular ATP levels are elevated post‐PH and NK cell cytotoxicity is substantively increased in vivo in response to hydrolysis of extracellular ATP levels by apyrase (soluble NTPDase). Moreover, liver regeneration is significantly increased by the scavenging of extracellular ATP in wildtype mice and in Rag2/common gamma‐null mice after adoptive transfer of NK cells. Blockade of NKG2D‐dependent interactions significantly decreased hepatocellular proliferation. In vitro, NK cell cytotoxicity is inhibited by extracellular ATP in a manner dependent on P2Y1, P2Y2, and P2X3 receptor activation. Conclusion: We propose that hepatic NK cells are activated and cytotoxic post‐PH and support hepatocellular proliferation. NK cell cytotoxicity is, however, attenuated by hepatic release of extracellular ATP by way of the activation of specific P2 receptors. Clearance of extracellular ATP elevates NK cell cytotoxicity and boosts liver regeneration. (HEPATOLOGY 2013)

Elevated liver regeneration in response to pharmacological reduction of elevated portal venous pressure by terlipressin after partial hepatectomy.

Background Liver regeneration is of crucial importance for patients undergoing living liver transplantations or extended liver resections and can be associated with elevated portal venous pressure, impaired hepatic regeneration, and postoperative morbidity. The aim of this study was to assess whether reduction of portal venous pressure by terlipressin improves postoperative liver regeneration in normal and steatotic livers after partial hepatectomy in a rodent model. Methods Portal venous pressure was assessed after minor (30%), standard (60%), or extended (80%) partial hepatectomy (PH) in mice with and without liver steatosis. Liver regeneration was assessed by BrdU incorporation and Ki-67 immunostaining. Results Portal venous pressure was significantly elevated post-PH in mice with normal and steatotic livers compared to sham-operated mice. Reduction of elevated portal pressure after 80% PH by terlipressin was associated with an increase of hepatocellular proliferation. In steatotic livers, animals treated with terlipressin had an increase in liver regeneration after 30% PH and increased survival after 60% PH. Mechanistically, terlipressin alleviated IL-6 mRNA expression following PH and down-regulated p21 and GADD45 mRNA suggesting a reduction of cell cycle inhibition and cellular stress. Conclusions Reduction of elevated portal pressure post-PH by the use of terlipressin improves liver regeneration after PH in lean and steatotic mouse livers.

Metabolomic markers for intestinal ischemia in a mouse model

BACKGROUND Diagnosis of intestinal ischemia remains a clinical challenge. The aim of the present study was to use a metabolomic protocol to identify upregulated and downregulated small molecules (M(r) < 500) in the serum of mice with intestinal ischemia. Such molecules could have clinical utility when evaluated as biomarkers in human studies. METHODS A mouse model for intestinal ischemia was established and validated using histology and serum tumor necrosis factor α concentrations. A second mouse model of peritoneal sepsis was used as a positive control. Serial serum samples were collected from these and from sham-operated animals. Sera were analyzed by gas chromatography-mass spectrometry for 40 small molecules as their trimethylsilyl and O-methyloxime derivatives. Peak areas were normalized against an internal standard and resultant peak area ratios subjected to multivariate data analysis using unsupervised principal components analysis and supervised orthogonal projection to latent structures-discriminant analysis. Upregulated and downregulated serum molecules were identified from their correlation to the orthogonal projection to latent structures-discriminant analysis model. RESULTS Three highly significantly upregulated (fold-change) serum molecules in intestinal ischemia were inorganic phosphate (2.4), urea (4.3), and threonic acid (2.9). Five highly significantly downregulated (fold-change) serum molecules were stearic acid (1.7), arabinose (2.7), xylose (1.6), glucose (1.4), and ribose (2.2). Lactic acid remained unchanged in intestinal ischemia. CONCLUSIONS Distinct molecular changes are reported here for the first time in intestinal ischemia. They reveal impairments of gut microbiota metabolism, intestinal absorption, and renal function, together with increased oxidative stress. In contrast to other reports, lactic acid was not significantly changed. These molecular signatures may now be evaluated in clinical studies.

The Use of Preoperative B-Type Natriuretic Peptide as a Predictor of Atrial Fibrillation After Thoracic Surgery: Systematic Review and Meta-Analysis

OBJECTIVE To determine whether elevated preoperative B-type natriuretic peptide (NP) measurements are an independent predictor of atrial fibrillation (AF) in patients having thoracic surgery. DESIGN Systematic review and meta-analysis. SETTING In-hospital and 30 days after thoracic surgery. PARTICIPANTS The 742 patients who participated in the 5 observational studies. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS EMBASE, OVID Health Star, Ovid Medline, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and ProQuest Dissertations and Theses A&I databases were searched for all studies of noncardiac thoracic surgery patients in whom a preoperative NP was measured up to 1 month before surgery, and that measured the incidence of postoperative AF. Studies were included regardless of their language, sample size, publication status, or study design. Study quality was evaluated using the Newcastle Ottowa Scale. The combined incidence of postoperative AF was 14.5% (n=108/742), and the NP thresholds used to predict AF varied among studies. An elevated preoperative NP measurement was associated with an OR of 3.13 (95% CI 1.38-7.12; I2=87%) for postoperative AF, with the sensitivity analysis reporting an OR of 9.51 (95% CI 4.66-19.40; I2=0). CONCLUSION Patients with an elevated preoperative NP measurement are at an increased risk of postoperative AF. There may be value in incorporating NP measurement into existing AF risk prediction models.

Tumor necrosis factor-related apoptosis-inducing ligand on NK cells protects from hepatic ischemia-reperfusion injury.

Background Ischemia-reperfusion injury (IRI) significantly contributes to graft dysfunction after liver transplantation. Natural killer (NK) cells are crucial innate effector cells in the liver and express tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a potent inducer of hepatocyte cell death. Here, we investigated if TRAIL expression on NK cells contributes to hepatic IRI. Methods The outcome after partial hepatic IRI was assessed in TRAIL-null mice and contrasted to C57BL/6J wild-type mice and after NK cell adoptive transfer in RAG2/common gamma-null mice that lack T, B, and NK cells. Liver IRI was assessed by histological analysis, alanine aminotransferase, hepatic neutrophil activation by myeloperoxidase activity, and cytokine secretion at specific time points. NK cell cytotoxicity and differentiation were assessed in vivo and in vitro. Results Twenty-four hours after reperfusion, TRAIL-null mice exhibited significantly higher serum transaminases, histological signs of necrosis, neutrophil infiltration, and serum levels of interleukin-6 compared to wild-type animals. Adoptive transfer of TRAIL-null NK cells into immunodeficient RAG2/common gamma-null mice was associated with significantly elevated liver damage compared to transfer of wild-type NK cells. In TRAIL-null mice, NK cells exhibit higher cytotoxicity and decreased differentiation compared to wild-type mice. In vitro, cytotoxicity against YAC-1 and secretion of interferon gamma by TRAIL-null NK cells were significantly increased compared to wild-type controls. Conclusions These experiments reveal that expression of TRAIL on NK cells is protective in a murine model of hepatic IRI through modulation of NK cell cytotoxicity and NK cell differentiation.

Total Thyroidectomy for Amiodarone-induced Thyrotoxicosis in the Hyperthyroid State

Amiodarone is a potent antiarrhythmic agent, indicated for the treatment of refractory arrhythmias, which may lead to thyrotoxicosis. In these patients, thyroidectomy is a valid therapeutic option. Antithyroid therapy in the immediate preoperative setting and the subsequently accepted minimal delay until thyroidectomy have not been clearly defined yet. The aim of the present study was to show, that total thyroidectomy under general anaesthesia in patients with amiodarone-induced thyrotoxicosis (AIT) is safe without necessarily obtaining an euthyroid state preoperatively.We conducted a retrospective cohort study of prospectively gathered data on 11 patients undergoing total thyroidectomy under general anaesthesia between January 2008 and December 2013 for AIT at our University Hospital.All patients were preoperatively treated with carbimazole, steroids and β-receptor antagonists. Additionally, 3 patients received potassium perchlorate and in one patient carbimazole was changed to propylthiouracil. Plasmapheresis was performed in 3 patients. Only one patient was euthyroid at the time of operation. There were no significant intra- and postoperative complications, especially no signs of thyroid storm. One patient could postoperatively be removed from the cardiac transplant waiting list due to improved cardiac function.Improvements in the interdisciplinary surgical management for AIT between cardiologists, endocrinologists, anaesthetists and endocrine surgeons provide the basis of safe total thyroidectomy under general anaesthesia in hyperthyroid state. Early surgery without long delay for medical antithyroid treatment (with its potential negative side effects) is recommended.

Nuclear Factor I-C acts as a regulator of hepatocyte proliferation at the onset of liver regeneration.

Knockout studies of the murine Nuclear Factor I‐C (NFI‐C) transcription factor revealed abnormal skin wound healing and growth of its appendages, suggesting a role in controlling cell proliferation in adult regenerative processes. Liver regeneration following partial hepatectomy (PH) is a well‐established regenerative model whereby changes elicited in hepatocytes lead to their rapid and phased proliferation. Although NFI‐C is highly expressed in the liver, no hepatic function was yet established for this transcription factor. This study aimed to determine whether NFI‐C may play a role in hepatocyte proliferation and liver regeneration.