Tyrosinemia: a review

An Unusual Presentation of Tyrosinemia Type 1 in a Pediatric Patient: Case Report and Comprehensive Review

Tyrosinemia type 1 often manifests with liver, renal, or peripheral neuropathy disorders. Before therapies like nitisinone, management was limited to dietary modifications and liver transplantation. We present a 19-month-old girl who developed respiratory distress requiring intubation, with abnormal laboratory findings, including liver function tests. Further work-up, including succinylacetone testing, confirmed tyrosinemia. She responded remarkably to nitisinone treatment.

Profiling of Biofluid Metabolites with a Kinetically Differentiated Binary Biosensing Platform

Biofluid metabolites have a crucial linkage with the health of the human body, and developing a universal method for metabolite monitoring is imperative for disease diagnosis and health management. Herein, we report a kinetically differentiated binary biosensing platform that is specifically responsive to NAD(P)H for profiling diverse biofluid metabolites. The kinetically differentiated binary biosensing platform comprises a cyanine derivative dye with fast reaction kinetics and a quinolinium derivative dye with slow reaction kinetics. Compared to the traditional unitary strategy for NAD(P)H detection, the linear range of the binary biosensing platform is widened by up to 20 times. NAD(P)H are ubiquitous cofactors in living systems, and metabolite production generally involves the consumption or generation of NAD(P)H. Thus, biofluid metabolites can be easily quantified by measuring the variation of NAD(P)H concentration during biochemical reactions with the binary biosensing platform. In this study, serum sorbitol, 2-hydroxybutyric acid (2HB), and α-ketoglutarate (AKG) were all quantified by the binary biosensing platform with accuracies higher than 93%. The kinetically differentiated binary biosensing platform can be extended to the analysis of any molecule that can react directly or indirectly with NAD(P)H. In addition, we constructed a paper-based assay with the binary biosensing platform, and the test papers showed good promise in the point-of-care (POC) profiling of biofluid metabolites. This study proposes a simple strategy to expand the calibration range of traditional unitary detection systems and further provides a universal paradigm for high throughput profiling of disease-associated biomolecules, which offers good promise in disease diagnosis and health management.

Diagnosis, treatment, management and monitoring of patients with tyrosinaemia type 1: Consensus group recommendations from the German-speaking countries

Hepatorenal tyrosinaemia (HT1) is an autosomal recessive disorder of tyrosine degradation resulting in hepatic and renal dysfunction, neurological sequelae may occur in some patients. The use of nitisinone (NTBC) has revolutionised treatment and outcome of this disorder. NTBC has to be combined with a low protein diet. While NTBC modulates the disease course in HT1 patients, several issues are open. Optimal dosage, doses per day, therapeutic range of NTBC concentration, mode of protein restriction and biomarkers are not well defined. HCC and neurocognitive deficits are long-term sequelae. Early diagnosis and treatment are essential to minimise the risk for these complications. Clinical guidance for management of HT1-patients is required. Randomised clinical studies are difficult in the presence of therapeutic options. We discussed these issues in a consensus group of 10 paediatricians, 1 adult hepatologist, 1 geneticist, 2 dieticians, 2 newborn screening specialists with experience in HT1, 1 psychologist and 2 representatives of a patient group from the German-speaking countries (DACH). Recommendations were based on scientific literature and expert opinion, also taking into account recent experience with newborn screening. There was strong consensus that newborn screening using succinylacetone (SA) and early treatment are essential for a good outcome. The dose of NTBC should be as low as possible without losing metabolic control. This has to be accompanied by a low protein diet, in some patients a simplified diet without calculation of protein intake. Specific education and psychosocial support are recommended. Indications for liver transplantation were defined. Monitoring shall include clinical findings, levels of SA, tyrosine, phenylalanine and NTBC in (dried) blood.

Optical sensors for transdermal biomarker detection: A review

This review has explored optical sensors and their important role in non-invasive transdermal biomarker detection. While electrochemical sensors have been thoroughly studied for biomarker tracking, optical sensors present a compelling alternative due to their high sensitivity and selectivity, multiplex capabilities, cost-efficiency, and small form factor. This review examines the latest advancements in optical sensing technologies for transdermal biomarker detection, such as colorimetry, fluorescence, surface plasmon resonance (SPR), fiber optics, photonic crystals, and Raman spectroscopy. These technologies have been applied in the analysis of biomarkers present in sweat and skin gases, which are essential for non-invasive health monitoring. Furthermore, the review has discussed the challenges and future perspectives of optical sensors in in transdermal biomarker detection. The analysis of various sensor types and their applications highlights the transformative potential of optical sensors in enhancing disease diagnostics and promoting proactive health management.

Fe Single-Atom and Fe Cluster-Coupled N, S Co-doped Carbon Nanomaterial-Based Flexible Electrochemical Sweat Biosensor for the Real-Time Analysis of Uric Acid and Tyrosine

Fe single-atom and Fe cluster-coupled N, S co-doped carbon nanomaterials (FeSA-FeONC-NSC) were prepared through a two-step high-temperature pyrolysis process using Gelidium corneum enriched with C, Fe, O, N, and S as precursors. The analysis by aberration-corrected scanning transmission electron microscopy and X-ray absorption spectroscopy revealed the presence of single-atom Fe in Fe-N4 coordination structures, along with small clusters as Fe-O-coordinated Fe2O3. Single-atom Fe in the form of Fe2+/Fe3+ provides more electrocatalytic active sites, which synergistically accelerates the charge migration process in the assembly of FeSA-FeONC-NSC with Fe2O3 clusters. The flexible nonenzymatic sensor, based on FeSA-FeONC-NSC and fabricated using a polydimethylsiloxane substrate, exhibited excellent catalytic activity for both uric acid (UA) and tyrosine (Tyr). Low detection limits for UA (0.14 μmol L-1) and Tyr (0.03 μmol L-1) were observed by using chronoamperometry in artificial sweat. The in situ detection of sweat was performed in combination with an integrated circuit board affixed to human skin, and the results were generally consistent with those of the high-performance liquid chromatography method. Therefore, FeSA-FeONC-NSC serves as a good modifier for wearable electrochemical sweat sensor applications.

Female Protection Against Diabetic Kidney Disease Is Regulated by Kidney-Specific AMPK Activity

Reduced kidney AMPK activity is associated with nutrient stress-induced chronic kidney disease (CKD) in male mice. In contrast, female mice resist nutrient stress-induced CKD. The role of kidney AMPK in sex-related organ protection against nutrient stress and metabolite changes was evaluated in diabetic kidney tubule-specific AMPKγ2KO (KTAMPKγ2ΚΟ) male and female mice. In wild-type (WT) males, diabetes increased albuminuria, urinary kidney injury molecule-1, hypertension, kidney p70S6K phosphorylation, and kidney matrix accumulation; these features were not exacerbated with KTAMPKγ2ΚΟ. Whereas WT females had protection against diabetes-induced kidney injury, KTAMPKγ2ΚΟ led to loss of female protection against kidney disease. The hormone 17β-estradiol ameliorated high glucose-induced AMPK inactivation, p70S6K phosphorylation, and matrix protein accumulation in kidney tubule cells. The mechanism for female protection against diabetes-induced kidney injury is likely via an estrogen-AMPK pathway, as inhibition of AMPK led to loss of estrogen protection to glucose-induced mTORC1 activation and matrix production. RNA sequencing and metabolomic analysis identified a decrease in the degradation pathway of phenylalanine and tyrosine resulting in increased urinary phenylalanine and tyrosine levels in females. The metabolite levels correlated with loss of female protection. The findings provide new insights to explain evolutionary advantages to females during states of nutrient challenges.

ARTICLE HIGHLIGHTS

Wearable electrochemical patch based on iron nano-catalysts incorporated laser-induced graphene for sweat metabolites detection

The development of wearable devices shows great application potential in health management. In this work, we propose the fabrication of a novel wearable electrochemical patch and prove its application in sweat metabolites detection. The patch is developed based on iron nano-catalysts incorporated laser-induced graphene (FeNCs/LIG), which is a newly integrated sensing electrode with unique three-dimensional nanostructure and good electrocatalytic activity. It shows desirable sensing performances for sweat metabolites including tyrosine (Tyr) and uric acid (UA) molecules. The detection limit of Tyr and UA can reach 5.11 μM and 1.37 μM, respectively. Besides, density functional theory calculation deeply reveals that the Fe active sites of FeNCs play an important role in molecule adsorption and electron transference, thus promoting sensing performance. To realize wearable application, a dual-channel hydrogel chip is designed and assembled with FeNCs/LIG. The developed patch is successfully utilized to accurately determination of Tyr and UA in sweat. This work is expected to provide a new non-invasive strategy for evaluating amino acid intake and metabolic level.

An engineered Escherichia coli Nissle strain prevents lethal liver injury in a mouse model of tyrosinemia type 1

BACKGROUND & AIMS

Hereditary tyrosinemia type 1 (HT1) results from the loss of fumarylacetoacetate hydrolase (FAH) activity and can lead to lethal liver injury. Therapeutic options for HT1 remain limited. In this study, we aimed to construct an engineered bacterium capable of reprogramming host metabolism and thereby provide a potential alternative approach for the treatment of HT1.

METHODS

Escherichia coli Nissle 1917 (EcN) was engineered to express genes involved in tyrosine metabolism in the anoxic conditions that are characteristic of the intestine (EcN-HT). Bodyweight, survival rate, plasma (tyrosine/liver function), H&E staining and RNA sequencing were used to assess its ability to degrade tyrosine and protect against lethal liver injury in Fah-knockout (KO) mice, a well-accepted model of HT1.

RESULTS

EcN-HT consumed tyrosine and produced L-DOPA (levodopa) in an in vitro system. Importantly, in Fah-KO mice, the oral administration of EcN-HT enhanced tyrosine degradation, reduced the accumulation of toxic metabolites, and protected against lethal liver injury. RNA sequencing analysis revealed that EcN-HT rescued the global gene expression pattern in the livers of Fah-KO mice, particularly of genes involved in metabolic signaling and liver homeostasis. Moreover, EcN-HT treatment was found to be safe and well-tolerated in the mouse intestine.

CONCLUSIONS

This is the first report of an engineered live bacterium that can degrade tyrosine and alleviate lethal liver injury in mice with HT1. EcN-HT represents a novel engineered probiotic with the potential to treat this condition.

IMPACT AND IMPLICATIONS

Patients with hereditary tyrosinemia type 1 (HT1) are characterized by an inability to metabolize tyrosine normally and suffer from liver failure, renal dysfunction, neurological impairments, and cancer. Given the overlap and complementarity between the host and microbial metabolic pathways, the gut microbiome provides a potential chance to regulate host metabolism through degradation of tyrosine and reduction of byproducts that might be toxic. Herein, we demonstrated that an engineered live bacterium, EcN-HT, could enhance tyrosine breakdown, reduce the accumulation of toxic tyrosine byproducts, and protect against lethal liver injury in Fah-knockout mice. These findings suggested that engineered live biotherapeutics that can degrade tyrosine in the gut may represent a viable and safe strategy for the prevention of lethal liver injury in HT1 as well as the mitigation of its associated pathologies.

Identification of CD8+ T-cell exhaustion signatures for prognosis in HBV-related hepatocellular carcinoma patients by integrated analysis of single-cell and bulk RNA-sequencing

BACKGROUND

HBV infection is the leading risk factor for HCC. HBV infection has been confirmed to be associated with the exhaustion status of CD8+ T cells and immunotherapeutic efficacy in HCC. In this study, we aimed to investigate the prognostic value of the CD8+ T-cell exhaustion signature and immunotherapy response in patients with HBV-related HCC.

METHODS

We identified different clusters of HBV-related HCC cells by single-cell RNA sequencing (scRNA-seq) and identified CD8+ T-cell exhaustion-related genes (TERGs) by pseudotime analysis. We conducted differential expression analysis and LASSO Cox regression to detect genes and construct a CD8+ T-cell exhaustion index (TEI). We next combined the TEI with other clinicopathological factors to design a prognostic nomogram for HCC patients. We also analysed the difference in the TEI between the non-responder and responder groups during anti-PD-L1 therapy. In addition, we investigated how HBV induces CD8+ T lymphocyte exhaustion through the inhibition of tyrosine metabolism in HCC using gene set enrichment analysis and RT‒qPCR.

RESULTS

A CD8+ T-cell exhaustion index (TEI) was established with 5 TERGs (EEF1E1, GAGE1, CHORDC1, IKBIP and MAGOH). An AFP level > 500 ng, vascular invasion, histologic grade (G3-G4), advanced TNM stage and poor five-year prognosis were related to a higher TEI score, while HBV infection was related to a lower TEI score. Among those receiving anti-PD-L1 therapy, responders had lower TEIs than non-responders did. The TEI also serves as an independent prognostic factor for HCC, and the nomogram incorporating the TEI, TNM stage, and vascular invasion exhibited excellent predictive value for the prognosis in HCC patients. RT‒qPCR revealed that among the tyrosine metabolism-associated genes, TAT (tyrosine aminotransferase) and HGD (homogentisate 1,2 dioxygenase) were expressed at lower levels in HBV-HCC than in non-HBV HCC.

CONCLUSION

Generally, we established a novel TEI model by comprehensively analysing the progression of CD8+ T-cell exhaustion, which shows promise for predicting the clinical prognosis and potential immunotherapeutic efficacy in HBV-related HCC patients.

A wearable sensor based on multifunctional conductive hydrogel for simultaneous accurate pH and tyrosine monitoring in sweat

Flexible and wearable sweat sensors have drawn extensive attention by virtue of their continuous and real-time monitoring of molecular level information. However, current sweat-based sensors still pose several challenges, such as low accuracy for analytes detection, susceptibility to microorganism and poor mechanical performance. Herein, we demonstrated a noninvasive wearable sweat sensing patch composed of an electrochemical sensing system, and a pilocarpine-based iontophoretic system to stimulate sweat secretion. The electrochemical sensor based on tannic acid-Ag-carbon nanotube-polyaniline (TA-Ag-CNT-PANI) composite hydrogel was designed for on-body detection of pH and tyrosine (Tyr), a disease marker associated with multiple disorders, such as tyrosinemia and bulimia nervosa. The wearable sweat sensor can not only monitor the pH and Tyr in sweat simultaneously, but also further calibrate Tyr detection results with the measured pH value, so as to eliminate the effect of Tyr response variance at different pH and enhance the accuracy of the sensor. Furthermore, the presence of tannic acid chelated-Ag nanoparticles (TA-Ag NPs) and carbon nanotubes (CNTs) significantly improved the conductivity and flexibility of the hydrogel and endowed the composite hydrogel with antibacterial capability. Of note, the constructed wearable sensor was capable of monitoring Tyr with enhanced accuracy in various sweats.

Skin-Interfaced Wearable Sweat Sensors for Precision Medicine

Wearable sensors hold great potential in empowering personalized health monitoring, predictive analytics, and timely intervention toward personalized healthcare. Advances in flexible electronics, materials science, and electrochemistry have spurred the development of wearable sweat sensors that enable the continuous and noninvasive screening of analytes indicative of health status. Existing major challenges in wearable sensors include: improving the sweat extraction and sweat sensing capabilities, improving the form factor of the wearable device for minimal discomfort and reliable measurements when worn, and understanding the clinical value of sweat analytes toward biomarker discovery. This review provides a comprehensive review of wearable sweat sensors and outlines state-of-the-art technologies and research that strive to bridge these gaps. The physiology of sweat, materials, biosensing mechanisms and advances, and approaches for sweat induction and sampling are introduced. Additionally, design considerations for the system-level development of wearable sweat sensing devices, spanning from strategies for prolonged sweat extraction to efficient powering of wearables, are discussed. Furthermore, the applications, data analytics, commercialization efforts, challenges, and prospects of wearable sweat sensors for precision medicine are discussed.

Hereditary Tyrosinemia Type 1 Mice under Continuous Nitisinone Treatment Display Remnants of an Uncorrected Liver Disease Phenotype

Hereditary tyrosinemia type 1 (HT1) is a genetic disorder of the tyrosine degradation pathway (TIMD) with unmet therapeutic needs. HT1 patients are unable to fully break down the amino acid tyrosine due to a deficient fumarylacetoacetate hydrolase (FAH) enzyme and, therefore, accumulate toxic tyrosine intermediates. If left untreated, they experience hepatic failure with comorbidities involving the renal and neurological system and the development of hepatocellular carcinoma (HCC). Nitisinone (NTBC), a potent inhibitor of the 4-hydroxyphenylpyruvate dioxygenase (HPD) enzyme, rescues HT1 patients from severe illness and death. However, despite its demonstrated benefits, HT1 patients under continuous NTBC therapy are at risk to develop HCC and adverse reactions in the eye, blood and lymphatic system, the mechanism of which is poorly understood. Moreover, NTBC does not restore the enzymatic defects inflicted by the disease nor does it cure HT1. Here, the changes in molecular pathways associated to the development and progression of HT1-driven liver disease that remains uncorrected under NTBC therapy were investigated using whole transcriptome analyses on the livers of Fah- and Hgd-deficient mice under continuous NTBC therapy and after seven days of NTBC therapy discontinuation. Alkaptonuria (AKU) was used as a tyrosine-inherited metabolic disorder reference disease with non-hepatic manifestations. The differentially expressed genes were enriched in toxicological gene classes related to liver disease, liver damage, liver regeneration and liver cancer, in particular HCC. Most importantly, a set of 25 genes related to liver disease and HCC development was identified that was differentially regulated in HT1 vs. AKU mouse livers under NTBC therapy. Some of those were further modulated upon NTBC therapy discontinuation in HT1 but not in AKU livers. Altogether, our data indicate that NTBC therapy does not completely resolves HT1-driven liver disease and supports the sustained risk to develop HCC over time as different HCC markers, including Moxd1, Saa, Mt, Dbp and Cxcl1, were significantly increased under NTBC.

Understanding metabolic alterations after SARS-CoV-2 infection: insights from the patients' oral microenvironmental metabolites

BACKGROUND

Coronavirus disease 2019 is a type of acute infectious pneumonia and frequently confused with influenza since the initial symptoms. When the virus colonized the patient's mouth, it will cause changes of the oral microenvironment. However, few studies on the alterations of metabolism of the oral microenvironment affected by SARS-CoV-2 infection have been reported. In this study, we explored metabolic alterations of oral microenvironment after SARS-CoV-2 infection.

METHODS

Untargeted metabolomics (UPLC-MS) was used to investigate the metabolic changes between oral secretion samples of 25 COVID-19 and 30 control participants. To obtain the specific metabolic changes of COVID-19, we selected 25 influenza patients to exclude the metabolic changes caused by the stress response of the immune system to the virus. Multivariate analysis (PCA and PLS-DA plots) and univariate analysis (students' t-test) were used to compare the differences between COVID-19 patients and the controls. Online hiplot tool was used to perform heatmap analysis. Metabolic pathway analysis was conducted by using the MetaboAnalyst 5.0 web application.

RESULTS

PLS-DA plots showed significant separation of COVID-19 patients and the controls. A total of 45 differential metabolites between COVID-19 and control group were identified. Among them, 35 metabolites were defined as SARS-CoV-2 specific differential metabolites. Especially, the levels of cis-5,8,11,14,17-eicosapentaenoic acid and hexanoic acid changed dramatically based on the FC values. Pathway enrichment found the most significant pathways were tyrosine-related metabolism. Further, we found 10 differential metabolites caused by the virus indicating the body's metabolism changes after viral stimulation. Moreover, adenine and adenosine were defined as influenza virus-specific differential metabolites.

CONCLUSIONS

This study revealed that 35 metabolites and tyrosine-related metabolism pathways were significantly changed after SARS-CoV-2 infection. The metabolic alterations of oral microenvironment in COVID-19 provided new insights into its molecular mechanisms for research and prognostic treatment.

Wearable and flexible electrochemical sensors for sweat analysis: a review

Flexible wearable sweat sensors allow continuous, real-time, noninvasive detection of sweat analytes, provide insight into human physiology at the molecular level, and have received significant attention for their promising applications in personalized health monitoring. Electrochemical sensors are the best choice for wearable sweat sensors due to their high performance, low cost, miniaturization, and wide applicability. Recent developments in soft microfluidics, multiplexed biosensing, energy harvesting devices, and materials have advanced the compatibility of wearable electrochemical sweat-sensing platforms. In this review, we summarize the potential of sweat for medical detection and methods for sweat stimulation and collection. This paper provides an overview of the components of wearable sweat sensors and recent developments in materials and power supply technologies and highlights some typical sensing platforms for different types of analytes. Finally, the paper ends with a discussion of the challenges and a view of the prospective development of this exciting field.

Metabolomics of a neonatal cohort from the Alliance for Maternal and Newborn Health Improvement biorepository: Effect of preanalytical variables on reference intervals

BACKGROUND

The study was conducted to determine reference interval (RI) and evaluate the effect of preanalytical variables on Dried blood spot (DBS)-amino acids, acylcarnitines and succinylacetone of neonates.

METHODOLOGY

DBS samples were collected within 48-72 hours of life. Samples were analyzed for biochemical markers on tandem mass spectrometer at the University of Iowa. Comparison of RI across various categorical variables were performed.

RESULTS

A total of 610 reference samples were selected based on exclusion criteria; 53.2% being females. Mean gestational age (GA) of mothers at the time of delivery was 38.7±1.6 weeks; 24.5% neonates were of low birth weight and 14.3% were preterm. Out of the total 610 neonates, 23.1% were small for GA. Reference intervals were generated for eleven amino acids, thirty-two acylcarnitines and succinylacetone concentrations. Markers were evaluated with respect to the influence of gender, GA, weight and time of sampling and statistically significant minimal differences were observed for some biomarkers.

CONCLUSION

RI for amino acids, succinylacetone and acylcarnitine on DBS has been established for healthy neonates, which could be of use in the clinical practice. Clinically significant effect of GA, weight, gender and time of sampling on these markers were not identified.

The mutation spectrum and ethnic distribution of non-hepatorenal tyrosinemia (types II, III)

BACKGROUND

Different types of non-hepatorenal tyrosinemia are among the rare forms of tyrosinemia. Tyrosinemia type II and III are autosomal recessive disorders caused by pathogenic variants in the tyrosine aminotransferase (TAT), and 4-hydroxyphenyl-pyruvate dioxygenas (HPPD) genes, respectively. There are still unclarified aspects in their clinical presentations, mutational spectrum, and genotype-phenotype correlation.

MAIN BODY

In this study, we evaluated the spectrum of TAT and HHPD gene mutations in patients with tyrosinemia type II and III. Moreover, biochemical and clinical findings are evaluated to establish a genotype-phenotype relationship in the above-mentioned patients. Thirty-three TAT variants have been reported in 42 families, consisting of 21 missense variants, 5 frameshift variants, 4 nonsense variants, 2 variants that primarily cause splicing site, and 1 skipping complete exon (large deletion). The most common variant is p.Arg57Ter, causing a splicing defect, and resulting in premature termination of translation, which was found in 10 patients from 3 families. In HPPD gene, eleven variants in 16 patients have been reported including 7 missense variants, 2 nonsense variants, 1 splice defect, and 1 frameshift variant so far. All variants are unique, except for p.Tyr160Cys, which is a missense variant found in two different patients. Regarding genotype-phenotype correlations, in 90% of tyrosinemia type II patients, positive clinical and biochemical correlations with a detected variant are observed. In HPPD gene, due to the small number of patients, it is not possible to make a definite conclusion.

CONCLUSION

This is the first large review of variants in TAT and HPPD, highlighting the wide spectrum of disease-causing mutations. Such information is beneficial for the establishment of a privileged mutation screening process in a specific region or ethnic group.

Identification and functional characterization of a novel homozygous intronic variant in the fumarylacetoacetate hydrolase gene in a Chinese patient with tyrosinemia type 1

BACKGROUND

Hereditary tyrosinemia type 1 (HT1; OMIM# 276700) is a genetic metabolism disorder caused by disease-causing variants in the fumarylacetoacetate hydrolase (FAH) gene encoding the last enzyme of the tyrosine catabolic pathway. Herein, we describe the clinical features and genetic characteristics of HT1 in a five years and seven months old Chinese patient.

METHODS

After clinical diagnosis of the proband with HT1, genetic testing was performed by Sanger sequencing of the FAH gene in all family members. Functional analysis of the disease-causing variant was performed by cDNA sequencing to understand the effect of the variant on FAH transcript. To further predict the variant effect, we used Human Splicing Finder (HSF) and PyMol in silico analysis.

RESULTS

We identified a novel previously undescribed intronic variant in the FAH gene (c.914-1G>A). It was detected in a child who was homozygous for the variant and had the clinical presentation of HT1. cDNA sequencing showed that this splice-junction variant affected the transcription of FAH by formation of two different transcripts. Our observations and laboratory experiments were in line with in silico methods.

CONCLUSIONS

Our study provides new insight into the HT1 variant spectrum and a better understanding of this disease in the Chinese population. This will be useful for molecular diagnosis in our country in cases where premarital screening, prenatal diagnosis and preimplantation genetic diagnosis are planned.

In vivo quantitative photoacoustic evaluation of the liver and kidney pathology in tyrosinemia

Hereditary tyrosinemia type Ⅰ (HT1) is a severe autosomal recessive inherited metabolic disease, which can result in severe damage of liver and kidney. Photoacoustic imaging (PAI) uses pulsed laser light to induce ultrasonic signals to facilitate the visualization of lesions that are strongly related to disease progression. In this study, the structural and functional changes of liver and kidney in HT1 was investigated by cross-scale PAI. The results showed that the hepatic lobule and renal tubule were severely damaged during HT1 progression. The hemoglobin content, vessel density, and liver function reserve were decreased. The metabolic half-life of indocyanine green declined from 59.8 s in health to 262.6 s in the advanced stage. Blood oxygen saturation was much lower than that in health. This study highlights the potential of PAI for in vivo evaluation of the liver and kidney lesions in HT1.

Protocols of Investigation of Neonatal Cholestasis-A Critical Appraisal

Neonatal cholestasis (NC) starts during the first three months of life and comprises extrahepatic and intrahepatic groups of diseases, some of which have high morbimortality rates if not timely identified and treated. Prolonged jaundice, clay-colored or acholic stools, and choluria in an infant indicate the urgent need to investigate the presence of NC, and thenceforth the differential diagnosis of extra- and intrahepatic causes of NC. The differential diagnosis of NC is a laborious process demanding the accurate exclusion of a wide range of diseases, through the skillful use and interpretation of several diagnostic tests. A wise integration of clinical-laboratory, histopathological, molecular, and genetic evaluations is imperative, employing extensive knowledge about each evaluated disease as well as the pitfalls of each diagnostic test. Here, we review the difficulties involved in correctly diagnosing the cause of cholestasis in an affected infant.

Toxic Metabolites and Inborn Errors of Amino Acid Metabolism: What One Informs about the Other

In inborn errors of metabolism, such as amino acid breakdown disorders, loss of function mutations in metabolic enzymes within the catabolism pathway lead to an accumulation of the catabolic intermediate that is the substrate of the mutated enzyme. In patients of such disorders, dietarily restricting the amino acid(s) to prevent the formation of these catabolic intermediates has a therapeutic or even entirely preventative effect. This demonstrates that the pathology is due to a toxic accumulation of enzyme substrates rather than the loss of downstream products. Here, we provide an overview of amino acid metabolic disorders from the perspective of the ‘toxic metabolites’ themselves, including their mechanism of toxicity and whether they are involved in the pathology of other disease contexts as well. In the research literature, there is often evidence that such metabolites play a contributing role in multiple other nonhereditary (and more common) disease conditions, and these studies can provide important mechanistic insights into understanding the metabolite-induced pathology of the inborn disorder. Furthermore, therapeutic strategies developed for the inborn disorder may be applicable to these nonhereditary disease conditions, as they involve the same toxic metabolite. We provide an in-depth illustration of this cross-informing concept in two metabolic disorders, methylmalonic acidemia and hyperammonemia, where the pathological metabolites methylmalonic acid and ammonia are implicated in other disease contexts, such as aging, neurodegeneration, and cancer, and thus there are opportunities to apply mechanistic or therapeutic insights from one disease context towards the other. Additionally, we expand our scope to other metabolic disorders, such as homocystinuria and nonketotic hyperglycinemia, to propose how these concepts can be applied broadly across different inborn errors of metabolism and various nonhereditary disease conditions.

Novel Cranial Imaging Findings and a Splice-Site Variant in a Patient with Tyrosinemia Type III, and a Summary of Published Cases

Tyrosinemia type III is an extremely rare autosomal recessive disease, with only 19 patients yet reported. It is caused by a deficiency of the 4-hydroxyphenylpyruvate dioxygenase enzyme, resulting from biallelic mutations in the HPD gene. Although the clinical spectrum of the disease is not fully known, most patients present with neurodevelopmental symptoms. We report on a 20-month-old patient who was investigated due to developmental delay and dysmorphic features. The girl had a novel splice-site mutation in the HPD gene and ventriculomegaly in cranial imaging, which was not previously associated with tyrosinemia type III. Our patient had mild subjective improvement in social skills and language development after dietary therapy was started and her tyrosine levels decreased. We also summarize clinical, biochemical, and genetic findings of previously published patients with biallelic HPD mutations.

Coordinated Cross-Talk Between the Myc and Mlx Networks in Liver Regeneration and Neoplasia

BACKGROUND & AIMS

The c-Myc (Myc) Basic helix-loop-helix leucine zipper (bHLH-ZIP) transcription factor is deregulated in most cancers. In association with Max, Myc controls target genes that supervise metabolism, ribosome biogenesis, translation, and proliferation. This Myc network crosstalks with the Mlx network, which consists of the Myc-like proteins MondoA and ChREBP, and Max-like Mlx. Together, this extended Myc network regulates both common and distinct gene targets. Here, we studied the consequence of Myc and/or Mlx ablation in the liver, particularly those pertaining to hepatocyte proliferation, metabolism, and spontaneous tumorigenesis.

METHODS

We examined the ability of hepatocytes lacking Mlx (MlxKO) or Myc+Mlx (double KO [DKO]) to repopulate the liver over an extended period of time in a murine model of type I tyrosinemia. We also compared this and other relevant behaviors, phenotypes, and transcriptomes of the livers with those from previously characterized MycKO, ChrebpKO, and MycKO × ChrebpKO mice.

RESULTS

Hepatocyte regenerative potential deteriorated as the Extended Myc Network was progressively dismantled. Genes and pathways dysregulated in MlxKO and DKO hepatocytes included those pertaining to translation, mitochondrial function, and hepatic steatosis resembling nonalcoholic fatty liver disease. The Myc and Mlx Networks were shown to crosstalk, with the latter playing a disproportionate role in target gene regulation. All cohorts also developed steatosis and molecular evidence of early steatohepatitis. Finally, MlxKO and DKO mice showed extensive hepatic adenomatosis.

CONCLUSIONS

In addition to showing cooperation between the Myc and Mlx Networks, this study showed the latter to be more important in maintaining proliferative, metabolic, and translational homeostasis, while concurrently serving as a suppressor of benign tumorigenesis. GEO accession numbers: GSE181371, GSE130178, and GSE114634.

Clinical and genetic characteristics of two patients with tyrosinemia type 1 in Slovenia – A novel fumarylacetoacetate hydrolase (FAH) intronic disease-causing variant

Tyrosinemia type 1 (HT1) is an inborn error of tyrosine catabolism that leads to severe liver, kidney, and neurological dysfunction. Newborn screening (NBS) can enable a timely diagnosis and early initiation of treatment.

We presented the follow up of the only two Slovenian patients diagnosed with HT1. Metabolic control was monitored by measuring tyrosine, phenylalanine and succinylacetone from dried blood spots (DBSs). Retrograde screening of HT1 was performed from DBSs taken at birth using tandem mass spectrometry.

First patient was diagnosed at the age of 6 months in the asymptomatic phase due to an abnormal liver echogenicity, the other presented at 2.5 months with an acute liver failure and needed a liver transplantation. The first was a compound heterozygote for a novel FAH intronic variant c.607-21A>G and c.192G>T whereas the second was homozygous for c.192G>T. At the non-transplanted patient, 66% of tyrosine and 79% of phenylalanine measurements were in strict reference ranges of 200–400 μmol/L and >30 μmol/L, respectively, which resulted in a favorable cognitive outcome at 3.6 years. On retrograde screening, both patients had elevated SA levels; on the other hand, tyrosine was elevated only at one.

We showed that non-coding regions should be analyzed when clinical and biochemical markers are characteristic of HT1. DBSs represent a convenient sample type for frequent amino acid monitoring. Retrograde diagnosis of HT1 was possible after more than three years of birth with SA as a primary marker, complemented by tyrosine.

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Non-coding region variants of FAH gene can result in a symptomatic HT1.

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Retrograde screening for HT1 is technically possible even three years after birth.

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DBS are convenient for monitoring HT1 patients and are family-friendly.

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Regular monitoring in HT1 patients can result in a favorable cognitive outcome.

An Endoscope-like SERS Probe Based on the Focusing Effect of Silica Nanospheres for Tyrosine and Urea Detection in Sweat

In this work, we developed a new type of SERS probe, which was composed of glass-SiO2-Au@MBN@Ag nanoparticles (NPs) three-dimensional Surface-enhanced Raman spectroscopy (SERS) substrate. When the laser passed through the quartz glass sheet, on the one hand, the SiO2 NPs supporting the Au@MBN@Ag NPs increase the roughness of the substrate surface, resulting in a large number of hot spots among nanoparticles. On the other hand, based on the focusing effect of silicon dioxide nanospheres, the laser can better focus on the surface of nanoparticles in the inverted SERS probe, thus showing better SERS enhancement. Furthermore, the Au@MBN@Ag NPs core-shell structure was used with 4-mercaptobenzoonitrile (MBN) as an internal standard molecule, and the quantitative determination of tyrosine and urea was realized by internal standard correction method. The standard working curves of the two had good linear correlation with R2 above 0.9555. The detection limits of tyrosine and urea were in the range of 2.85 × 10-10 M~7.54 × 10-6 M, which confirms that this design can be used for quantitative and specific detection of biological molecules, demonstrating great practical significance for the research of diseases such as skin lesions and endocrine disorders.

ADHD symptoms in neurometabolic diseases: Underlying mechanisms and clinical implications

Neurometabolic diseases (NMDs) are typically caused by genetic abnormalities affecting enzyme functions, which in turn interfere with normal development and activity of the nervous system. Although the individual disorders are rare, NMDs are collectively relatively common and often lead to lifelong difficulties and high societal costs. Neuropsychiatric manifestations, including ADHD symptoms, are prominent in many NMDs, also when the primary biochemical defect originates in cells and tissues outside the nervous system. ADHD symptoms have been described in phenylketonuria, tyrosinemias, alkaptonuria, succinic semialdehyde dehydrogenase deficiency, X-linked ichthyosis, maple syrup urine disease, and several mitochondrial disorders, but are probably present in many other NMDs and may pose diagnostic and therapeutic challenges. Here we review current literature linking NMDs with ADHD symptoms. We cite emerging evidence that many NMDs converge on common neurochemical mechanisms that interfere with monoamine neurotransmitter synthesis, transport, metabolism, or receptor functions, mechanisms that are also considered central in ADHD pathophysiology and treatment. Finally, we discuss the therapeutic implications of these findings and propose a path forward to increase our understanding of these relationships.

Non-mental diseases associated with ADHD across the lifespan: Fidgety Philipp and Pippi Longstocking at risk of multimorbidity?

Several non-mental diseases seem to be associated with an increased risk of ADHD and ADHD seems to be associated with increased risk for non-mental diseases. The underlying trajectories leading to such brain-body co-occurrences are often unclear - are there direct causal relationships from one disorder to the other, or does the sharing of genetic and/or environmental risk factors lead to their occurring together more frequently or both? Our goal with this narrative review was to provide a conceptual synthesis of the associations between ADHD and non-mental disease across the lifespan. We discuss potential shared pathologic mechanisms, genetic background and treatments in co-occurring diseases. For those co-occurrences for which published studies with sufficient sample sizes exist, meta-analyses have been published by others and we discuss those in detail. We conclude that non-mental diseases are common in ADHD and vice versa and add to the disease burden of the patient across the lifespan. Insufficient attention to such co-occurring conditions may result in missed diagnoses and suboptimal treatment in the affected individuals.

Loss of tyrosine catabolic enzyme HPD promotes glutamine anaplerosis through mTOR signaling in liver cancer

The liver plays central roles in coordinating different metabolic processes, such as the catabolism of amino acids. In this study, we identify a loss of tyrosine catabolism and a concomitant increase in serum tyrosine levels during liver cancer development. Liver cells with disordered tyrosine catabolism, as exemplified by the suppression of a tyrosine catabolic enzyme 4-hydroxyphenylpyruvate dioxygenase (HPD), display augmented tumorigenic and proliferative potentials. Metabolomics profiling and isotope tracing reveal the metabolic reliance of HPD-silenced cells on glutamine, coupled with increased tricarboxylic acid cycle metabolites and their associated amino acid pools. Mechanistically, HPD silencing reduces ketone bodies, which regulate the proliferative and metabolic phenotypes via the AMPK/mTOR/p70S6 kinase pathway and mTOR-dependent glutaminase (GLS) activation. Collectively, our results demonstrate a metabolic link between tyrosine and glutamine metabolism, which could be exploited as a potentially promising anticancer therapy for liver cancer.

Pediatric metabolic liver diseases: Evolving role of liver transplantation

Metabolic liver diseases (MLD) are the second most common indication for liver transplantation (LT) in children. This is based on the fact that the majority of enzymes involved in various metabolic pathways are present within the liver and LT can cure or at least control the disease manifestation. LT is also performed in metabolic disorders for end-stage liver disease, its sequelae including hepatocellular cancer. It is also performed for preventing metabolic crisis', arresting progression of neurological dysfunction with a potential to reverse symptoms in some cases and for preventing damage to end organs like kidneys as in the case of primary hyperoxalosis and methyl malonic acidemia. Pathological findings in explant liver with patients with metabolic disease include unremarkable liver to steatosis, cholestasis, inflammation, variable amount of fibrosis, and cirrhosis. The outcome of LT in metabolic disorders is excellent except for patients with mitochondrial disorders where significant extrahepatic involvement leads to poor outcomes and hence considered a contraindication for LT. A major advantage of LT is that in the post-operative period most patients can discontinue the special formula which they were having prior to the transplant and this increases their well-being and improves growth parameters. Auxiliary partial orthotopic LT has been described for patients with noncirrhotic MLD where a segmental graft is implanted in an orthotopic position after partial resection of the native liver. The retained native liver can be the potential target for future gene therapy when it becomes a clinical reality.

Demographics, in-hospital analysis, and prevalence of 33 rare diseases with effective treatment in Shanghai

BACKGROUND

Rare diseases are ailments which impose a heavy burden on individual patients and global society as a whole. The rare disease management landscape is not a smooth one-a rare disease is quite often hard to diagnose, treat, and investigate. In China, the country's rapid economic rise and development has brought an increased focus on rare diseases. At present, there is a growing focus placed on the importance and public health priority of rare diseases and on improving awareness, definitions, and treatments.

METHODS

In this work we utilized clinical data from the Shanghai HIE System to characterize the status of 33 rare diseases with effective treatment in Shanghai for the time period of 2013-2016.

RESULTS AND CONCLUSION

First, we describe the total number of patients, year-to-year change in new patients with diagnosis in one of the target diseases and the distribution of gender and age for the top six (by patient number) diseases of the set of 33 rare diseases. Second, we describe the hospitalization burden in terms of in-hospital ratio, length of stay, and medical expenses during hospitalization. Finally, rare disease period prevalence is calculated for the rare diseases set.

Therapeutic Targeting of Fumaryl Acetoacetate Hydrolase in Hereditary Tyrosinemia Type I

Fumarylacetoacetate hydrolase (FAH) is the fifth enzyme in the tyrosine catabolism pathway. A deficiency in human FAH leads to hereditary tyrosinemia type I (HT1), an autosomal recessive disorder that results in the accumulation of toxic metabolites such as succinylacetone, maleylacetoacetate, and fumarylacetoacetate in the liver and kidney, among other tissues. The disease is severe and, when untreated, it can lead to death. A low tyrosine diet combined with the herbicidal nitisinone constitutes the only available therapy, but this treatment is not devoid of secondary effects and long-term complications. In this study, we targeted FAH for the first-time to discover new chemical modulators that act as pharmacological chaperones, directly associating with this enzyme. After screening several thousand compounds and subsequent chemical redesign, we found a set of reversible inhibitors that associate with FAH close to the active site and stabilize the (active) dimeric species, as demonstrated by NMR spectroscopy. Importantly, the inhibitors are also able to partially restore the normal phenotype in a newly developed cellular model of HT1.

National trends and outcomes of genetically inherited non-alcoholic chronic liver disease in the USA: estimates from the National Inpatient Sample (NIS) database

Background

Medical literature on the prevalence of genetic liver disease is lacking. In this study, we investigated the in-hospital healthcare and economic burden from genetic causes of non-alcoholic chronic liver disease (NACLD) and non-alcoholic liver cirrhosis (NALC) in the USA.

Methods

Data were abstracted from the National Inpatient Sample database between 2002 and 2014 using ICD9 codes for patients discharged with NACLD and NALC secondary to genetic diseases including alpha-1 antitrypsin deficiency (A1ATd), cystic fibrosis (CF), Wilson disease (WD), hereditary hemochromatosis (HHC), glycogen storage disease, and disorders of aromatic amino-acid metabolism (DAAAM).

Results

Throughout the study period, there were 19,332 discharges for NACLD associated with the six genetic diseases including 14,368 for NALC. There were $1.09 billion in hospital charges, 790 in-hospital deaths, and 955 liver transplants performed. Overall, A1ATd was associated with 8,983 (62.52%) hospitalizations for NALC followed by WD, CF, and HHC. The highest in-hospital mortality was seen with HHC. The greatest frequency of liver transplants was seen with DAAAM.

Conclusion

The number of hospitalizations for genetic liver diseases continues to increase. With increased funding and directed research efforts, we can aim to improve medical treatments and the quality of life for patients at risk for liver deterioration.

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part II: effects of supplementation with methionine or taurine on growth, feed utilization, and health

Fishmeal has long been a staple protein feedstuff for fish, but its global shortage and high price have prompted its replacement with alternative sustainable sources. In this experiment involving largemouth bass (a carnivorous fish), a new mixture of feedstuffs (45% poultry byproduct meal, 30% soybean meal, 15% blood meal, and 10% krill shrimp meal) was added to low (14.5%) fishmeal diets along with 0.0%, 0.5% taurine, 0.5% methionine, or 0.5% taurine plus 0.5% methionine (dry matter basis). The positive control diet [65.3% fishmeal (46% crude protein on dry matter basis)] and all low-fishmeal diets contained 40% true protein and 10% lipids. There were 3 tanks per treatment group (20 fish/tank). Fish with the mean initial body weight of 16.6 g were fed to satiety twice daily. Compared with the unsupplemented low-fishmeal group, supplementing either 0.5% methionine or 0.5% methionine plus 0.5% taurine to the low-fishmeal diet improved (P < 0.05) the growth, feed utilization, retention of dietary protein and lipids, and health of largemouth bass, reduced (P < 0.05) the occurrence of black skin syndrome from ~ 40 to ~ 10%. Histological sections of tissues from the fish with black skin syndrome showed retina degeneration, liver damage, and enteritis in the intestine. Compared with methionine supplementation, supplementing 0.5% taurine alone to the low-fishmeal diet did not affect the growth or feed efficiency of fish and had less beneficial effects (P < 0.05) on ameliorating the black skin syndrome. These results indicated that: (a) the basal low-fishmeal diet was inadequate in methionine or taurine; and (b) dietary supplementation with methionine was an effective method to improve the growth performance, feed efficiency, and health of largemouth bass. Further studies are warranted to understand the pathogenesis of the black skin syndrome in largemouth bass.

Hereditary Tyrosinemia Compounded With Hyperinsulinemic Hypoglycemia: Challenging Diagnosis of a Rare Case

Hereditary tyrosinemia type 1 (HT-1) is a rare autosomal recessive disorder caused by a deficiency in the enzyme fumarylacetoacetate hydrolase (FAH), which catalyzes the final step in the tyrosine degradation pathway. Hereditary tyrosinemia is a heterogeneous disease with a wide spectrum of clinical manifestations involving hepatic, renal, or nervous systems. It has grave consequences if left untreated. Some of the late complications of hereditary tyrosinemia include cirrhosis, liver nodules, hepatocellular carcinoma, hypophosphatemic rickets, nephrocalcinosis, glomerulosclerosis, and chronic renal failure. Rarely, infants with hereditary tyrosinemia may present with persistent hypoglycemia, which may be a result of acute liver failure or hyperinsulinism. Hyperinsulinemic hypoglycemia (HH), caused by dysregulation of insulin secretion from pancreatic β-cells, leads to insulin driven glucose entry into the tissues and inhibits glycolysis, gluconeogenesis, fatty acid release, and ketone body synthesis. Hyperinsulinemic hypoglycemia can cause severe, persistent hypoketotic hypoglycemia. Diagnosing tyrosinemia type 1 can be a challenge as it is a heterogeneous disorder with a wide variety of clinical manifestations and complications. We herein report a rare case of a three-day-old male neonate with HT-1 compounded with HH.

High-throughput assessment of mutations generated by genome editing in induced pluripotent stem cells by high-resolution melting analysis

BACKGROUND AND AIMS

Genome editing of induced pluripotent stem cells (iPSCs) holds great potential for both disease modeling and regenerative medicine. Although clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 provides an efficient and precise genome editing tool, iPSCs are especially difficult to transfect, resulting in a small percentage of cells carrying the desired correction. A high-throughput method to identify edited clones is required to reduce the time and costs of such an approach.

METHODS

Here we assess high-resolution melting analysis (HRMA), a simple and efficient real-time polymerase chain reaction-based method, and compare it with more commonly used assays.

RESULTS AND CONCLUSIONS

Our data show that HRMA is a robust and highly sensitive method, allowing the cost-effective and time-saving screening of genome-edited iPSCs. Samples can be prepared directly from 96-well microtiter plates for high-throughput analysis, and amplicons can be further analyzed with downstream techniques for further confirmation, if needed.

TYROSINEMIA TYPE III: A CASE REPORT OF SIBLINGS AND LITERATURE REVIEW

Objective:

Tyrosinemia type III (HT III) is the rarest form of tyrosinemia, and the full clinical spectrum of this disorder is still unknown. The neurological involvement varies, including intellectual impairment and attention deficit disorder with hyperactivity (ADHD). We report the case of two siblings diagnosed with HT III at different ages.

Case description:

The index case was diagnosed by newborn screening for endocrine and metabolic disorders, starting a low-protein diet immediately, with a consistent decrease in tyrosine levels. By the age of three, the child displayed a hyperactive behavior, starting treatment for ADHD two years later. At seven years of age, he shows a slight improvement in terms of behavior and attention span and has a cognitive performance slightly lower than his peers, despite maintaining acceptable tyrosine levels. His sister, who had a history of ADHD since age five, was diagnosed with HT III after family screening at the age of eight. Despite initiating a dietetic treatment, her behavior did not improve, and she has a mild intellectual impairment.

Comments:

This is the first case report describing siblings with HT III who underwent nutritional treatment with a low-protein diet in different phases of life, with a better neurological and behavioral evaluation in the patient who started treatment earlier.

Role of the N-terminus in human 4-hydroxyphenylpyruvate dioxygenase activity

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a key enzyme in tyrosine catabolism, catalysing the oxidation of 4-hydroxyphenylpyruvate to homogentisate. Genetic deficiency of this enzyme causes type III tyrosinaemia. The enzyme comprises two barrel-shaped domains formed by the N- and C-termini, with the active site located in the C-terminus. This study investigated the role of the N-terminus, located at the domain interface, in HPPD activity. We observed that the kcat/Km decreased ∼8-fold compared with wild type upon removal of the 12 N-terminal residues (ΔR13). Interestingly, the wild-type level of activity was retained in a mutant missing the 17 N-terminal residues, with a kcat/Km 11-fold higher than that of the ΔR13 mutant; however, the structural stability of this mutant was lower than that of wild type. A 2-fold decrease in catalytic efficiency was observed for the K10A and E12A mutants, indicating synergism between these residues in the enzyme catalytic function. A molecular dynamics simulation showed large RMS fluctuations in ΔR13 suggesting that conformational flexibility at the domain interface leads to lower activity in this mutant. These results demonstrate that the N-terminus maintains the stability of the domain interface to allow for catalysis at the active site of HPPD.

Living-donor liver transplantation for children with tyrosinemia type I

OBJECTIVE

To evaluate the efficacy of living-donor liver transplantation (LDLT) in children with tyrosinemia type I.

METHODS

Altogether 10 patients diagnosed with tyrosinemia type I underwent LDLT between June 2013 and April 2019. Cirrhosis was the indication for LDLT in all 10 patients, and hepatocellular carcinoma (HCC) was suspected in nine. Patients' outcomes, including liver function, restoration of metabolism, quality of life and physical development, were analyzed after LDLT.

RESULTS

All recipients were alive with a normal liver function after a median follow-up period of 49 months. Pathological examinations detected HCC in one patient, dysplasia in five and cirrhosis in all. Nine patients were found to have elevated alpha-fetoprotein level, and their median alpha-fetoprotein level dropped from 2520 ng/mL to a normal level after LDLT, with no recurrence of HCC detected during the follow-up. Tyrosine metabolism was restored to its normal level with normalized plasma tyrosine and succinylacetone concentrations. Moreover, urinary succinylacetone excretion decreased significantly during the follow up. LDLT improved patients' renal tubular function, as evidenced by the normalized plasma phosphate concentration and improved glomerular filtration rate. Severe rickets symptoms, including spontaneous fractures and bone pain, were also ameliorated. Improved motor function was reported by all patients' parents during the follow-up. Dietary restriction was no longer required, which was associated with a favorable catch-up in growth and improved quality of life. Complete resolution of hypertrophic cardiomyopathy was observed one year after LDLT in one patient.

CONCLUSION

LDLT is an effective treatment for patients with end-stage liver disease resulting from tyrosinemia type I.

Long-Term Outcomes and Practical Considerations in the Pharmacological Management of Tyrosinemia Type 1

Tyrosinemia type 1 (TT1) is a rare metabolic disease caused by a defect in tyrosine catabolism. TT1 is clinically characterized by acute liver failure, development of hepatocellular carcinoma, renal and neurological problems, and consequently an extremely poor outcome. This review showed that the introduction of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) in 1992 has revolutionized the outcome of TT1 patients, especially when started pre-clinically. If started early, NTBC can prevent liver failure, renal problems, and neurological attacks and decrease the risk for hepatocellular carcinoma. NTBC has been shown to be safe and well tolerated, although the long-term effectiveness of treatment with NTBC needs to be awaited. The high tyrosine concentrations caused by treatment with NTBC could result in ophthalmological and skin problems and requires life-long dietary restriction of tyrosine and its precursor phenylalanine, which could be strenuous to adhere to. In addition, neurocognitive problems have been reported since the introduction of NTBC, with hypothesized but as yet unproven pathophysiological mechanisms. Further research should be done to investigate the possible relationship between important clinical outcomes and blood concentrations of biochemical parameters such as phenylalanine, tyrosine, succinylacetone, and NTBC, and to develop clear guidelines for treatment and follow-up with reliable measurements. This all in order to ultimately improve the combined NTBC and dietary treatment and limit possible complications such as hepatocellular carcinoma development, neurocognitive problems, and impaired quality of life.

Dysregulated Choline, Methionine, and Aromatic Amino Acid Metabolism in Patients with Wilson Disease: Exploratory Metabolomic Profiling and Implications for Hepatic and Neurologic Phenotypes

Wilson disease (WD) is a genetic copper overload condition characterized by hepatic and neuropsychiatric symptoms with a not well-understood pathogenesis. Dysregulated methionine cycle is reported in animal models of WD, though not verified in humans. Choline is essential for lipid and methionine metabolism. Defects in neurotransmitters as acetylcholine, and biogenic amines are reported in WD; however, less is known about their circulating precursors. We aimed to study choline, methionine, aromatic amino acids, and phospholipids in serum of WD subjects. Hydrophilic interaction chromatography-quadrupole time-of-flight mass spectrometry was employed to profile serum of WD subjects categorized as hepatic, neurologic, and pre-clinical. Hepatic transcript levels of genes related to choline and methionine metabolism were verified in the Jackson Laboratory toxic milk mouse model of WD (tx-j). Compared to healthy subjects, choline, methionine, ornithine, proline, phenylalanine, tyrosine, and histidine were significantly elevated in WD, with marked alterations in phosphatidylcholines and reductions in sphingosine-1-phosphate, sphingomyelins, and acylcarnitines. In tx-j mice, choline, methionine, and phosphatidylcholine were similarly dysregulated. Elevated choline is a hallmark dysregulation in WD interconnected with alterations in methionine and phospholipid metabolism, which are relevant to hepatic steatosis. The elevated phenylalanine, tyrosine, and histidine carry implications for neurologic manifestations and are worth further investigation.

The Dynamic Chromatin Architecture of the Regenerating Liver

BACKGROUND & AIMS

The adult liver is the main detoxification organ and routinely is exposed to environmental insults but retains the ability to restore its mass and function upon tissue damage. However, extensive injury can lead to liver failure, and chronic injury causes fibrosis, cirrhosis, and hepatocellular carcinoma. Currently, the transcriptional regulation of organ repair in the adult liver is incompletely understood.

METHODS

We isolated nuclei from quiescent as well as repopulating hepatocytes in a mouse model of hereditary tyrosinemia, which recapitulates the injury and repopulation seen in toxic liver injury in human beings. We then performed the assay for transposase accessible chromatin with high-throughput sequencing specifically in repopulating hepatocytes to identify differentially accessible chromatin regions and nucleosome positioning. In addition, we used motif analysis to predict differential transcription factor occupancy and validated the in silico results with chromatin immunoprecipitation followed by sequencing for hepatocyte nuclear factor 4α (HNF4α) and CCCTC-binding factor (CTCF).

RESULTS

Chromatin accessibility in repopulating hepatocytes was increased in the regulatory regions of genes promoting proliferation and decreased in the regulatory regions of genes involved in metabolism. The epigenetic changes at promoters and liver enhancers correspond with the regulation of gene expression, with enhancers of many liver function genes showing a less accessible state during the regenerative process. Moreover, increased CTCF occupancy at promoters and decreased HNF4α binding at enhancers implicate these factors as key drivers of the transcriptomic changes in replicating hepatocytes that enable liver repopulation.

CONCLUSIONS

Our analysis of hepatocyte-specific epigenomic changes during liver repopulation identified CTCF and HNF4α as key regulators of hepatocyte proliferation and regulation of metabolic programs. Thus, liver repopulation in the setting of toxic injury makes use of both general transcription factors (CTCF) for promoter activation, and reduced binding by a hepatocyte-enriched factor (HNF4α) to temporarily limit enhancer activity. All sequencing data in this study were deposited to the Gene Expression Omnibus database and can be downloaded with accession number GSE109466.

Tissue-specific FAH deficiency alters sleep-wake patterns and results in chronic tyrosinemia in mice

Fumarylacetoacetate hydrolase (FAH) is the last enzyme in tyrosine catabolism, and mutations in the FAH gene are associated with hereditary tyrosinemia type I (HT1 or TYRSN1) in humans. In a behavioral screen of N-ethyl-N-nitrosourea mutagenized mice we identified a mutant line which we named "swingshift" (swst, MGI:3611216) with a nonsynonymous point mutation (N68S) in Fah that caused age-dependent disruption of sleep-wake patterns. Mice homozygous for the mutation had an earlier onset of activity (several hours before lights off) and a reduction in total activity and body weight when compared with wild-type or heterozygous mice. Despite abnormal behavioral entrainment to light-dark cycles, there were no differences in the period or phase of the central clock in mutant mice, indicating a defect downstream of the suprachiasmatic nucleus. Interestingly, these behavioral phenotypes became milder as the mice grew older and were completely rescued by the administration of NTBC [2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione], an inhibitor of 4-hydroxyphenylpyruvate dioxygenase, which is upstream of FAH. Mechanistically, the swst mutation had no effect on the enzymatic activity of FAH, but rather promoted the degradation of the mutant protein. This led to reduced FAH protein levels and enzymatic activity in the liver and kidney (but not the brain or fibroblasts) of homozygous mice. In addition, plasma tyrosine-but not methionine, phenylalanine, or succinylacetone-increased in homozygous mice, suggesting that swst mutants provide a model of mild, chronic HT1.

HPD degradation regulated by the TTC36-STK33-PELI1 signaling axis induces tyrosinemia and neurological damage

Decreased expression of 4-hydroxyphenylpyruvic acid dioxygenase (HPD), a key enzyme for tyrosine metabolism, is a cause of human tyrosinemia. However, the regulation of HPD expression remains largely unknown. Here, we demonstrate that molecular chaperone TTC36, which is highly expressed in liver, is associated with HPD and reduces the binding of protein kinase STK33 to HPD, thereby inhibiting STK33-mediated HPD T382 phosphorylation. The reduction of HPD T382 phosphorylation results in impaired recruitment of FHA domain-containing PELI1 and PELI1-mediated HPD polyubiquitylation and degradation. Conversely, deficiency or depletion of TTC36 results in enhanced STK33-mediated HPD T382 phosphorylation and binding of PELI1 to HPD and subsequent PELI1-mediated HPD downregulation. Ttc36^−/− mice have reduced HPD expression in the liver and exhibit tyrosinemia, damage to hippocampal neurons, and deficits of learning and memory. These findings reveal a previously unknown regulation of HPD expression and highlight the physiological significance of TTC36-STK33-PELI1-regulated HPD expression in tyrosinemia and tyrosinemia-associated neurological disorders.

Decreased expression of 4-hydroxyphenylpyruvic acid dioxygenase (HPD) has been linked to tyrosinemia, yet the mechanism underlying the regulation of HPD expression is largely unknown. Here the authors demonstrate that molecular chaperone TTC36, which is highly expressed in liver, is associated with HPD and reduces the binding of protein kinase STK33 to HPD, thereby inhibiting STK33-mediated HPD T382 phosphorylation.

Evolution of tyrosinemia type 1 disease in patients treated with nitisinone in Spain

Treatment with nitisinone (NTBC) has brought about a drastic improvement in the treatment and prognosis of hereditary tyrosinemia type I (HT1). We conducted a retrospective observational multicentric study in Spanish HT1 patients treated with NTBC to assess clinical and biochemical long-term evolution.We evaluated 52 patients, 7 adults and 45 children, treated with NTBC considering: age at diagnosis, diagnosis by clinical symptoms, or by newborn screening (NBS); phenotype (acute/subacute/chronic), mutational analysis; symptoms at diagnosis and clinical course; biochemical markers; doses of NTBC; treatment adherence; anthropometric evolution; and neurocognitive outcome.The average follow-up period was 6.1 ± 4.9 and 10.6 ± 5.4 years in patients with early and late diagnosis respectively. All patients received NTBC from diagnosis with an average dose of 0.82 mg/kg/d. All NBS-patients (n = 8) were asymptomatic at diagnosis except 1 case with acute liver failure, and all remain free of liver and renal disease in follow-up. Liver and renal affectation was markedly more frequent at diagnosis in patients with late diagnosis (P < .001 and .03, respectively), with ulterior positive hepatic and renal course in 86.4% and 93.2% of no-NBS patients, although 1 patient with good metabolic control developed hepatocarcinoma.Despite a satisfactory global nutritional evolution, 46.1% of patients showed overweight/obesity. Interestingly lower body mass index was observed in patients with good dietary adherence (20.40 ± 4.43 vs 24.30 ± 6.10; P = .08) and those with good pharmacological adherence (21.19 ± 4.68 vs 28.58 ± 213.79).intellectual quotient was ≥85 in all NBS- and 68.75% of late diagnosis cases evaluated, 15% of which need pedagogical support, and 6.8% (3/44) showed school failure.Among the 12 variants identified in fumarylacetoacetate hydrolase gene, 1 of them novel (H63D), the most prevalent in Spanish population is c.554-1 G>T.After NTBC treatment a reduction in tyrosine and alpha-fetoprotein levels was observed in all the study groups, significant for alpha-fetoprotein in no NBS-group (P = .03), especially in subacute/chronic forms (P = .018).This series confirms that NTBC treatment had clearly improved the prognosis and quality of life of HT1 patients, but it also shows frequent cognitive dysfunctions and learning difficulties in medium-term follow-up, and, in a novel way, a high percentage of overweight/obesity.

Hereditary tyrosinemia type I-associated mutations in fumarylacetoacetate hydrolase reduce the enzyme stability and increase its aggregation rate

More than 100 mutations in the gene encoding fumarylacetoacetate hydrolase (FAH) cause hereditary tyrosinemia type I (HT1), a metabolic disorder characterized by elevated blood levels of tyrosine. Some of these mutations are known to decrease FAH catalytic activity, but the mechanisms of FAH mutation–induced pathogenicity remain poorly understood. Here, using diffusion ordered NMR spectroscopy, cryo-EM, and CD analyses, along with site-directed mutagenesis, enzymatic assays, and molecular dynamics simulations, we investigated the putative role of thermodynamic and kinetic stability in WT FAH and a representative set of 19 missense mutations identified in individuals with HT1. We found that at physiological temperatures and concentrations, WT FAH is in equilibrium between a catalytically active dimer and a monomeric species, with the latter being inactive and prone to oligomerization and aggregation. We also found that the majority of the deleterious mutations reduce the kinetic stability of the enzyme and always accelerate the FAH aggregation pathway. Depending mainly on the position of the amino acid in the structure, pathogenic mutations either reduced the dimer population or decreased the energy barrier that separates the monomer from the aggregate. The mechanistic insights reported here pave the way for the development of pharmacological chaperones that target FAH to tackle the severe disease HT1.

Crystal Structure of 4-Hydroxyphenylpyruvate Dioxygenase in Complex with Substrate Reveals a New Starting Point for Herbicide Discovery

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a promising target for drug and pesticide discovery. The unknown binding mode of substrate is still a big challenge for the understanding of enzymatic reaction mechanism and novel HPPD inhibitor design. Herein, we determined the first crystal structure of Arabidopsis thaliana HPPD (AtHPPD) in complex with its natural substrate (HPPA) at a resolution of 2.80 Å. Then, combination of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations confirmed that HPPA takes keto rather than enol form inside the HPPD active pocket. Subsequent site-directed mutagenesis and kinetic analysis further showed that residues (Phe424, Asn423, Glu394, Gln307, Asn282, and Ser267) played important roles in substrate binding and catalytic cycle. Structural comparison between HPPA-AtHPPD and holo-AtHPPD revealed that Gln293 underwent a remarkable rotation upon the HPPA binding and formed H-bond network of Ser267-Asn282-Gln307-Gln293, resulting in the transformation of HPPD from an inactive state to active state. Finally, taking the conformation change of Gln293 as a target, we proposed a new strategy of blocking the transformation of HPPD from inactive state to active state to design a novel inhibitor with K_i value of 24.10 nM towards AtHPPD. The inhibitor has entered into industry development as the first selective herbicide used for the weed control in sorghum field. The crystal structure of AtHPPD in complex with the inhibitor (2.40 Å) confirmed the rationality of the design strategy. We believe that the present work provides a new starting point for the understanding of enzymatic reaction mechanism and the design of next generation HPPD inhibitors.

Presence of three mutations in the fumarylacetoacetate hydrolase gene in a patient with atypical symptoms of hereditary tyrosinemia type I

Hereditary tyrosinemia type 1 (HT1), the most severe disease of the tyrosine catabolic pathway, is caused by a deficiency of fumarylacetoacetate hydrolase (FAH). More than 90 disease-causing variants have been identified in the fah gene. We investigated the molecular defect in a patient who presented atypical symptoms for the disease. No immunoreactive FAH was found in the liver and RNA analysis by RT-PCR suggested the presence of splicing mutations. Indeed, the patient was revealed to be a compound heterozygote for IVS6-1 g- > t and two new variants, namely p.V259L and p.G398E. Using splicing minigene constructs transfected in HeLa cells, the c.775G > C variant (p.V259L) was shown to affect partially exon 9 splicing thereby allowing the production of some full-length double-mutant FAH transcripts. The p.G398E variant had a major impact on enzyme activity, which was worsened by the p.V259L variant. Surprisingly, the double mutant protein was expressed to similar level as the wild-type protein upon transfection in HeLa cells but was absent in the patient liver extract, suggesting a higher propensity to be degraded in the hepatocellular context.