TRMU deficiency: A broad clinical spectrum responsive to cysteine supplementation.

TRMU is a nuclear gene crucial for mitochondrial DNA translation by encoding tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase, which thiolates mitochondrial tRNA. Biallelic pathogenic variants in TRMU are associated with transient infantile liver failure. Other less common presentations such as Leigh syndrome, myopathy, and cardiomyopathy have been reported. Recent studies suggested that provision of exogenous L-cysteine or N-acetylcysteine may ameliorate the effects of disease-causing variants and improve the natural history of the disease. Here, we report six infants with biallelic TRMU variants, including four previously unpublished patients, all treated with exogenous cysteine. We highlight the first report of an affected patient undergoing orthotopic liver transplantation, the long-term effects of cysteine supplementation, and the ability of the initial presentation to mimic multiple inborn errors of metabolism. We propose that TRMU deficiency should be suspected in all children presenting with persistent lactic acidosis and hypoglycemia, and that combined N-acetylcysteine and L-cysteine supplementation should be considered prior to molecular diagnosis, as this is a low-risk approach that may increase survival and mitigate the severity of the disease course.

Impaired Redox and Protein Homeostasis as Risk Factors and Therapeutic Targets in Toxin-Induced Biliary Atresia.

BACKGROUND & AIMS: Extrahepatic biliary atresia (BA) is a pediatric liver disease with no approved medical therapy. Recent studies using human samples and experimental modeling suggest that glutathione redox metabolism and heterogeneity play a role in disease pathogenesis. We sought to dissect the mechanistic basis of liver redox variation and explore how other stress responses affect cholangiocyte injury in BA. METHODS: We performed quantitative in situ hepatic glutathione redox mapping in zebrafish larvae carrying targeted mutations in glutathione metabolism genes and correlated these findings with sensitivity to the plant-derived BA-linked toxin biliatresone. We also determined whether genetic disruption of HSP90 protein quality control pathway genes implicated in human BA altered biliatresone toxicity in zebrafish and human cholangiocytes. An in vivo screening of a known drug library was performed to identify novel modifiers of cholangiocyte injury in the zebrafish experimental BA model, with subsequent validation. RESULTS: Glutathione metabolism gene mutations caused regionally distinct changes in the redox potential of cholangiocytes that differentially sensitized them to biliatresone. Disruption of human BA-implicated HSP90 pathway genes sensitized zebrafish and human cholangiocytes to biliatresone-induced injury independent of glutathione. Phosphodiesterase-5 inhibitors and other cyclic guanosine monophosphate signaling activators worked synergistically with the glutathione precursor N-acetylcysteine in preventing biliatresone-induced injury in zebrafish and human cholangiocytes. Phosphodiesterase-5 inhibitors enhanced proteasomal degradation and required intact HSP90 chaperone. CONCLUSION: Regional variation in glutathione metabolism underlies sensitivity to the biliary toxin biliatresone and may account for the reported association between BA transplant-free survival and glutathione metabolism gene expression. Human BA can be causatively linked to genetic modulation of protein quality control. Combined treatment with N-acetylcysteine and cyclic guanosine monophosphate signaling enhancers warrants further investigation as therapy for BA.

Analysis of surgical interruption of the enterohepatic circulation as a treatment for pediatric cholestasis.

To evaluate the efficacy of nontransplant surgery for pediatric cholestasis, 58 clinically diagnosed children, including 20 with Alagille syndrome (ALGS), 16 with familial intrahepatic cholestasis-1 (FIC1), 18 with bile salt export pump (BSEP) disease, and 4 others with low γ-glutamyl transpeptidase disease (levels <100 U/L), were identified across 14 Childhood Liver Disease Research Network (ChiLDReN) centers. Data were collected retrospectively from individuals who collectively had 39 partial external biliary diversions (PEBDs), 11 ileal exclusions (IEs), and seven gallbladder-to-colon (GBC) diversions. Serum total bilirubin decreased after PEBD in FIC1 (8.1 ± 4.0 vs. 2.9 ± 4.1 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.02), but not in ALGS or BSEP. Total serum cholesterol decreased after PEBD in ALGS patients (695 ± 465 vs. 457 ± 319 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.0001). Alanine aminotransferase levels increased in ALGS after PEBD (182 ± 70 vs. 260 ± 73 IU/L, preoperatively vs. 24 months; P = 0.03), but not in FIC1 or BSEP. ALGS, FIC1, and BSEP patients experienced less severely scored pruritus after PEBD (ALGS, 100% vs. 9% severe; FIC1, 64% vs. 10%; BSEP, 50% vs. 20%, preoperatively vs. >24 months postoperatively, respectively; P < 0.001). ALGS patients experienced a trend toward greater freedom from xanthomata after PEBD. There was a trend toward decreased pruritus in FIC1 after IE and GBC. Vitamin K supplementation increased in ALGS after PEBD (33% vs. 77%; P = 0.03). Overall, there were 15 major complications after surgery. Twelve patients (3 ALGS, 3 FIC1, and 6 BSEP) subsequently underwent liver transplantation. CONCLUSION: This was a multicenter analysis of nontransplant surgical approaches to intrahepatic cholestasis. Approaches vary, are well tolerated, and generally, although not uniformly, result in improvement of pruritus and cholestasis. (Hepatology 2017;65:1645-1654).

Total serum bilirubin predicts fat-soluble vitamin deficiency better than serum bile acids in infants with biliary atresia.

OBJECTIVE: Fat-soluble vitamin (FSV) deficiency is a well-recognized consequence of cholestatic liver disease and reduced intestinal intraluminal bile acid. We hypothesized that serum bile acid (SBA) would predict biochemical FSV deficiency better than serum total bilirubin (TB) level in infants with biliary atresia. METHODS: Infants enrolled in the Trial of Corticosteroid Therapy in Infants with Biliary Atresia after hepatoportoenterostomy were the subjects of this investigation. Infants received standardized FSV supplementation and monitoring of TB, SBA, and vitamin levels at 1, 3, and 6 months. A logistic regression model was used with the binary indicator variable insufficient/sufficient as the outcome variable. Linear and nonparametric correlations were made between specific vitamin measurement levels and either TB or SBA. RESULTS: The degree of correlation for any particular vitamin at a specific time point was higher with TB than with SBA (higher for TB in 31 circumstances vs 3 circumstances for SBA). Receiver operating characteristic curve shows that TB performed better than SBA (area under the curve 0.998 vs 0.821). Including both TB and SBA did not perform better than TB alone (area under the curve 0.998). CONCLUSIONS: We found that TB was a better predictor of FSV deficiency than SBA in infants with biliary atresia. The role of SBA as a surrogate marker of FSV deficiency in other cholestatic liver diseases, such as progressive familial intrahepatic cholestasis, α-1-antitrypsin deficiency, and Alagille syndrome in which the pathophysiology is dominated by intrahepatic cholestasis, warrants further study.

Use of corticosteroids after hepatoportoenterostomy for bile drainage in infants with biliary atresia: the START randomized clinical trial.

IMPORTANCE: Biliary atresia is the most common cause of end-stage liver disease in children. Controversy exists as to whether use of steroids after hepatoportoenterostomy improves clinical outcome. OBJECTIVE: To determine whether the addition of high-dose corticosteroids after hepatoportoenterostomy is superior to surgery alone in improving biliary drainage and survival with the native liver. DESIGN, SETTING, AND PATIENTS: The multicenter, double-blind Steroids in Biliary Atresia Randomized Trial (START) was conducted in 140 infants (mean age, 2.3 months) between September 2005 and February 2011 in the United States; follow-up ended in January 2013. INTERVENTIONS: Participants were randomized to receive intravenous methylprednisolone (4 mg/kg/d for 2 weeks) and oral prednisolone (2 mg/kg/d for 2 weeks) followed by a tapering protocol for 9 weeks (n = 70) or placebo (n = 70) initiated within 72 hours of hepatoportoenterostomy. MAIN OUTCOMES AND MEASURES: The primary end point (powered to detect a 25% absolute treatment difference) was the percentage of participants with a serum total bilirubin level of less than 1.5 mg/dL with his/her native liver at 6 months posthepatoportoenterostomy. Secondary outcomes included survival with native liver at 24 months of age and serious adverse events. RESULTS: The proportion of participants with improved bile drainage was not statistically significantly improved by steroids at 6 months posthepatoportoenterostomy (58.6% [41/70] of steroids group vs 48.6% [34/70] of placebo group; adjusted relative risk, 1.14 [95% CI, 0.83 to 1.57]; P = .43). The adjusted absolute risk difference was 8.7% (95% CI, -10.4% to 27.7%). Transplant-free survival was 58.7% in the steroids group vs 59.4% in the placebo group (adjusted hazard ratio, 1.0 [95% CI, 0.6 to 1.8]; P = .99) at 24 months of age. The percentage of participants with serious adverse events was 81.4% [57/70] of the steroids group and 80.0% [56/70] of the placebo group (P > .99); however, participants receiving steroids had an earlier time of onset of their first serious adverse event by 30 days posthepatoportoenterostomy (37.2% [95% CI, 26.9% to 50.0%] of steroids group vs 19.0% [95% CI, 11.5% to 30.4%] of placebo group; P = .008). CONCLUSIONS AND RELEVANCE: Among infants with biliary atresia who have undergone hepatoportoenterostomy, high-dose steroid therapy following surgery did not result in statistically significant treatment differences in bile drainage at 6 months, although a small clinical benefit could not be excluded. Steroid treatment was associated with earlier onset of serious adverse events in children with biliary atresia. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00294684.