Controversies in the Mechanism of Total Parenteral Nutrition Induced Pathology

Over 30,000 patients are permanently dependent on Total Parenteral Nutrition (TPN) for survival with several folds higher requiring TPN for a prolonged duration. Unfortunately, it can cause potentially fatal complications. TPN infusion results in impairment of gut mucosal integrity, enhanced inflammation, increased cytokine expression and trans-mucosal bacterial permeation. It also causes endotoxin associated down regulation of bile acid transporters and Parenteral Nutrition Associated Liver Disease (PNALD), which includes steatosis, disrupted glucose metabolism, disrupted lipid metabolism, cholestasis and liver failure. Despite multiple theories, its etiology and pathophysiology remains elusive and is likely multifactorial. An important cause for TPN related pathologies appears to be a disruption in the normal enterohepatic circulation due to a lack of feeding during such therapy. This is further validated by the fact that in clinical settings, once cholestasis sets in, its reversal occurs when a patient is receiving a major portion of calories enterally. There are several other postulated mechanisms including gut bacterial permeation predisposing to endotoxin associated down regulation of bile acid transporters. An additional potential mechanism includes toxicity of the TPN solution itself, such as lipid mediated hepatic toxicity. Prematurity, leading to a poor development of bile acid regulating nuclear receptors and transporters has also been implicated as a causative factor. This review presents the current controversies and research into mechanisms of TPN associated injury

Hepatic-targeted RNA interference provides robust and persistent knockdown of alpha-1 antitrypsin levels in ZZ patients.

BACKGROUND & AIMS:Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder causing pulmonary and liver disease. The PiZ mutation in AAT (SERPINA1) results in mis-folded AAT protein (Z-AAT) accumulating in hepatocytes, leading to fibrosis and cirrhosis. RNAi-based therapeutics silencing production of hepatic Z-AAT might benefit patients with AATD-associated liver disease. This study evaluated an RNAi therapeutic to silence production of AAT. METHODS:Part A of this double-blind first-in-human study randomized 54 healthy volunteers (HVs) into single dose cohorts (two placebo: four active), receiving escalating doses of the investigational agent ARC-AAT from 0.38 to 8.0 mg/kg or placebo. Part B randomized 11 patients with PiZZ (homozygous for Z-AAT) genotype AATD, who received up to 4.0 mg/kg of ARC-AAT or placebo. Patients with baseline FibroScan® >11 kPa or forced expiratory volume in one second (FEV1) <60% were excluded. Assessments included safety, pharmacokinetics, and change in serum AAT concentrations. RESULTS:A total of 36 HVs received ARC-AAT and 18 received placebo (part A). Seven PiZZ individuals received ARC-AAT and four received placebo (part B). A dose response in serum AAT reduction was observed at doses ≥4 mg/kg with similar relative reductions in PiZZ patients and HVs at 4 mg/kg and a maximum reduction of 76.1% (HVs) vs. 78.8% (PiZZ) at this dose. The time it took for serum AAT to return to baseline was similar for HV and PiZZ. There were no notable differences between HV and PiZZ safety parameters. The study was terminated early because of toxicity findings related to the delivery vehicle (ARC-EX1) seen in a non-human primate study. CONCLUSION:PiZZ patients and HVs responded similarly to ARC-AAT. Deep and durable knockdown of hepatic AAT production based on observed reduction in serum AAT concentrations was demonstrated. LAY SUMMARY:Accumulation of abnormal proteins in the livers of patients with alpha-1 antitrypsin deficiency may lead to decreased liver function and potentially liver failure. Therapeutics targeting the production of these abnormal proteins may be used to prevent or treat liver disease in patients with alpha-1 antitrypsin deficiency. CLINICAL TRIAL REGISTRATION NUMBER:NCT02363946

Longitudinal Outcomes in Young Patients with Alpha-1-Antitrypsin Deficiency with Native Liver Reveal that Neonatal Cholestasis is a Poor Predictor of Future Portal Hypertension

ObjectivesTo identify predictors of portal hypertension, liver transplantation, and death in North American youth with alpha-1-antitrypsin (AAT) deficiency, and compare with patients with AAT deficiency elsewhere.Study designThe Childhood Liver Disease Research Network Longitudinal Observational Study of Genetic Causes of Intrahepatic Cholestasis is a prospective, cohort study of pediatric cholestatic liver diseases, including AAT deficiency, enrolling PIZZ and PISZ subjects 0-25 years of age seen since November 2007 at 17 tertiary care centers in the US and Canada. Data from standard-of-care baseline and annual follow-up visits were recorded from medical records, history, physical examination, and laboratory studies. Participants with portal hypertension were identified based on data collected.ResultsWe enrolled 350 participants (60% male) with a native liver; 278 (79%) entered the cohort without portal hypertension and 18 developed portal hypertension during follow-up. Thirty participants required liver transplantation; 2 patients died during 1077 person-years of follow-up. There was no difference in participants with or without preceding neonatal cholestasis progressing to transplantation or death during the study (12% vs 7%; P = .09), or in experiencing portal hypertension (28% vs 21%; P = .16); the hazard ratio for neonatal cholestasis leading to portal hypertension was P = .04. Development of portal hypertension was associated with a reduced height Z-score.ConclusionsPortal hypertension in youth with AAT deficiency impacts growth measures. Progression to liver transplantation is slow and death is rare, but the risk of complications and severe liver disease progression persists throughout childhood. A history of neonatal cholestasis is a weak predictor of severe disease

Serum biomarkers correlated with liver stiffness assessed in a multicenter study of pediatric cholestatic liver disease

Background and aimsDetailed investigation of the biological pathways leading to hepatic fibrosis and identification of liver fibrosis biomarkers may facilitate early interventions for pediatric cholestasis.Approach and resultsA targeted enzyme-linked immunosorbent assay-based panel of nine biomarkers (lysyl oxidase, tissue inhibitor matrix metalloproteinase (MMP) 1, connective tissue growth factor [CTGF], IL-8, endoglin, periostin, Mac-2-binding protein, MMP-3, and MMP-7) was examined in children with biliary atresia (BA; n = 187), alpha-1 antitrypsin deficiency (A1AT; n = 78), and Alagille syndrome (ALGS; n = 65) and correlated with liver stiffness (LSM) and biochemical measures of liver disease. Median age and LSM were 9 years and 9.5 kPa. After adjusting for covariates, there were positive correlations among LSM and endoglin ( p = 0.04) and IL-8 ( p < 0.001) and MMP-7 ( p < 0.001) in participants with BA. The best prediction model for LSM in BA using clinical and lab measurements had an R2 = 0.437; adding IL-8 and MMP-7 improved R2 to 0.523 and 0.526 (both p < 0.0001). In participants with A1AT, CTGF and LSM were negatively correlated ( p = 0.004); adding CTGF to an LSM prediction model improved R2 from 0.524 to 0.577 ( p = 0.0033). Biomarkers did not correlate with LSM in ALGS. A significant number of biomarker/lab correlations were found in participants with BA but not those with A1AT or ALGS.ConclusionsEndoglin, IL-8, and MMP-7 significantly correlate with increased LSM in children with BA, whereas CTGF inversely correlates with LSM in participants with A1AT; these biomarkers appear to enhance prediction of LSM beyond clinical tests. Future disease-specific investigations of change in these biomarkers over time and as predictors of clinical outcomes will be important