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Molecular Genetics and Metabolism... Dec 2020Peroxisomal D-bifunctional protein (DBP) deficiency is an autosomal recessive disorder historically described as a Zellweger-like syndrome comprising neonatal seizures,...
INTRODUCTION
Peroxisomal D-bifunctional protein (DBP) deficiency is an autosomal recessive disorder historically described as a Zellweger-like syndrome comprising neonatal seizures, retinopathy, hearing loss, dysmorphic features, and other complications. The gene encodes DBP which is essential for oxidation of peroxisomal substrates. We describe 4 patients - 2 unrelated female girls and 2 monozygotic twin sisters - with DBP deficiency and phenotypic diversity.
PATIENT REPORTS
Patient 1 presented neonatally with hypotonia and seizures, and later on developed global developmental delay and regression, sensorineural hearing loss, nystagmus and cortical blindness. The brain MRI demonstrated bilateral peri-sylvian polymicrogyria. Whole exome sequencing revealed 2 mutations in the gene (c.752G>A, p.(Arg251Gln); c.868 + 1delG).Patient 2 presented with hypotonia, motor delay, and sensorineural hearing loss in infancy, considerable developmental regression during her fourth year, nystagmus, and peripheral neuropathy. Brain MRI demonstrated cerebellar atrophy and abnormal basal ganglia and white matter signal, which appeared after the age of two years. Whole exome sequencing revealed 2 mutations in the gene (c.14 T>G, p.(Leu5Arg); c.752G>A, p.(Arg251Gln)).Patients 3 and 4, two female monozygotic twins, presented with hypotonia, developmental delay, and macrocephaly from birth, and later on also sensorineural hearing loss, infantile spasms and hypsarrhythmia, and adrenal insufficiency. Brain MRI demonstrated delayed myelination, and an assay of peroxisomal beta oxidation suggested DBP deficiency. Sequencing of the gene revealed the same 2 mutations as in patient 1.
DISCUSSION
We describe 4 patients with variable and diverse clinical picture of DBP deficiency and particularly emphasize the clinical, biochemical, and neuroimaging characteristics. Interestingly, the clinical phenotype varied even between patients with the exact two mutations in the gene. In addition, in two of the three patients in whom levels of VLCFA including phytanic acid were measured, the levels were within normal limits. This is expanding further the clinical spectrum of this disorder, which should be considered in the differential diagnosis of every patient with hypotonia and developmental delay especially if accompanied by polymicrogyria, seizures, sensorineural hearing loss, or adrenal insufficiency regardless of their VLCFA profile.
PubMed: 32904102
DOI: 10.1016/j.ymgmr.2020.100631 -
EClinicalMedicine Aug 2020Coronavirus disease 2019 (COVID-19) is associated with a high disease burden with 10% of confirmed cases progressing towards critical illness. Nevertheless, the disease...
Prognostic factors associated with mortality risk and disease progression in 639 critically ill patients with COVID-19 in Europe: Initial report of the international RISC-19-ICU prospective observational cohort.
BACKGROUND
Coronavirus disease 2019 (COVID-19) is associated with a high disease burden with 10% of confirmed cases progressing towards critical illness. Nevertheless, the disease course and predictors of mortality in critically ill patients are poorly understood.
METHODS
Following the critical developments in ICUs in regions experiencing early inception of the pandemic, the European-based, international RIsk Stratification in COVID-19 patients in the Intensive Care Unit (RISC-19-ICU) registry was created to provide near real-time assessment of patients developing critical illness due to COVID-19.
FINDINGS
As of April 22, 2020, 639 critically ill patients with confirmed SARS-CoV-2 infection were included in the RISC-19-ICU registry. Of these, 398 had deceased or been discharged from the ICU. ICU-mortality was 24%, median length of stay 12 (IQR, 5-21) days. ARDS was diagnosed in 74%, with a minimum P/F-ratio of 110 (IQR, 80-148). Prone positioning, ECCO2R, or ECMO were applied in 57%. Off-label therapies were prescribed in 265 (67%) patients, and 89% of all bloodstream infections were observed in this subgroup ( = 66; RR=3·2, 95% CI [1·7-6·0]). While PCT and IL-6 levels remained similar in ICU survivors and non-survivors throughout the ICU stay ( = 0·35, 0·34), CRP, creatinine, troponin, d-dimer, lactate, neutrophil count, P/F-ratio diverged within the first seven days (<0·01). On a multivariable Cox proportional-hazard regression model at admission, creatinine, d-dimer, lactate, potassium, P/F-ratio, alveolar-arterial gradient, and ischemic heart disease were independently associated with ICU-mortality.
INTERPRETATION
The European RISC-19-ICU cohort demonstrates a moderate mortality of 24% in critically ill patients with COVID-19. Despite high ARDS severity, mechanical ventilation incidence was low and associated with more rescue therapies. In contrast to risk factors in hospitalized patients reported in other studies, the main mortality predictors in these critically ill patients were markers of oxygenation deficit, renal and microvascular dysfunction, and coagulatory activation. Elevated risk of bloodstream infections underscores the need to exercise caution with off-label therapies.
PubMed: 32838231
DOI: 10.1016/j.eclinm.2020.100449 -
Molecular Genetics and Metabolism 2020Sjögren-Larsson syndrome (SLS) is an inherited metabolic disease characterized by ichthyosis, spasticity, intellectual disability and deficient oxidation and...
Sjögren-Larsson syndrome (SLS) is an inherited metabolic disease characterized by ichthyosis, spasticity, intellectual disability and deficient oxidation and accumulation of of fatty aldehydes and alcohols. We investigated whether excess fatty alcohols in SLS are diverted into biosynthesis of ether glycerolipids (eGLs) by measuring the 1-O-alkylglycerol (AG) backbone of eGLs in stratum corneum, plasma and red blood cells (RBCs). In all tissues, saturated and monounsaturated AGs were detected. In stratum corneum from SLS patients, saturated AGs (C15-C20) were increased 97-fold (range: 86- to 169-fold) compared to controls. AGs were largely (67 ± 9%) derived from neutral esterified eGLs (i.e. alkyl-diacylglyerol) and free non-esterified AGs (28 ± 10%), but very little from plasmalogens (3 ± 5%). Plasma from SLS patients had 2-fold more C18:0-AG (p < 0.005) and 40% less C16:1-AG (p < 0.01) than controls but the total concentration of AGs was not increased, and the AG profile in RBCs from SLS subjects was normal. All AGs were profoundly reduced in plasma and RBCs from patients with Zellweger spectrum disorder, who have impaired eGL (i.e. plasmalogen) synthesis. The striking accumulation of AGs in stratum corneum of SLS patients constitutes a novel lipid biomarker for this disease, and may contribute to the pathogenesis of the ichthyosis. Measurement of AGs is a simple and convenient method to assess global synthesis of eGLs and potentially identify patients with defects in their metabolism.
Topics: Aldehydes; Cells, Cultured; Epidermis; Ethers; Fatty Acids; Fatty Alcohols; Female; Fibroblasts; Humans; Ichthyosis; Intellectual Disability; Lipid Metabolism; Male; Muscle Spasticity; Oxidation-Reduction; Sjogren-Larsson Syndrome
PubMed: 32800643
DOI: 10.1016/j.ymgme.2020.08.002 -
Frontiers in Cell and Developmental... 2020Ketohexokinase (KHK) is the first and rate-limiting enzyme of fructose metabolism. Expression of the two alternatively spliced KHK isoforms, KHK-A and KHK-C, is...
Ketohexokinase (KHK) is the first and rate-limiting enzyme of fructose metabolism. Expression of the two alternatively spliced KHK isoforms, KHK-A and KHK-C, is tissue-specific and KHK-C is predominantly expressed in liver, kidney and intestine and responsible for the fructose-catabolizing function. While KHK isoform choice has been linked to the development of disorders such as obesity, diabetes, cardiovascular disease and cancer, little is known about the regulation of total KHK expression. In the present study, we investigated how hypoxic signaling influences fructose metabolism in the liver. Hypoxia or von Hippel-Lindau (VHL) tumor suppressor loss leads to the stabilization of hypoxia-inducible factors alpha (HIF-1α and HIF-2α) and the activation of their signaling to mediate adaptive responses. By studying liver-specific , /, and / knockout mice, we found that KHK expression is suppressed by HIF-2α (encoded by ) but not by HIF-1α signaling on mRNA and protein levels. Reduced KHK levels were accompanied by downregulation of aldolase B (ALDOB) in the livers of and knockout mice, further indicating inhibited fructose metabolism. HIF-1α and HIF-2α have both overlapping and distinct target genes but are differentially regulated depending on the cell type and physiologic or pathologic conditions. HIF-2α activation augments peroxisome degradation in mammalian cells by pexophagy and thereby changes lipid composition reminiscent of peroxisomal disorders. We further demonstrated that fructose metabolism is negatively regulated by peroxisome-deficiency in a knockout Zellweger mouse model, which lacks functional peroxisomes and is characterized by widespread metabolic dysfunction. Repression of fructolytic genes in knockout mice appeared to be independent of PPARα signaling and nutritional status. Interestingly, our results demonstrate that both HIF-2α and peroxisome-deficiency result in downregulation of independent of splicing as both isoforms, as well as , are significantly downregulated. Hence, our study offers new and unexpected insights into the general regulation of KHK, and therefore fructolysis. We revealed a novel regulatory function of HIF-2α, suggesting that HIF-1α and HIF-2α have tissue-specific opposing roles in the regulation of expression, isoform choice and fructolysis. In addition, we discovered a previously unknown function of peroxisomes in the regulation of fructose metabolism.
PubMed: 32733884
DOI: 10.3389/fcell.2020.00566 -
Biochimica Et Biophysica Acta.... Nov 2020Zellweger spectrum disorders (ZSD) are inborn errors of metabolism caused by mutations in PEX genes that lead to peroxisomal biogenesis disorder (PBD). No validated...
Zellweger spectrum disorders (ZSD) are inborn errors of metabolism caused by mutations in PEX genes that lead to peroxisomal biogenesis disorder (PBD). No validated treatment is able to modify the dismal progression of the disease. ZSD mouse models used to develop therapeutic approaches are limited by poor survival and breeding restrictions. To overcome these limitations, we backcrossed the hypomorphic Pex1 p.G844D allele to NMRI background. NMRI mouse breeding restored an autosomal recessive Mendelian inheritance pattern and delivered twice larger litters. Mice were longitudinally phenotyped up to 6 months of age to make this model suitable for therapeutic interventions. ZSD mice exhibited growth retardation and relative hepatomegaly associated to progressive hepatocyte hypertrophy. Biochemical studies associated with RNA sequencing deciphered ZSD liver glycogen metabolism alterations. Affected fibroblasts displayed classical immunofluorescence pattern and biochemical alterations associated with PBD. Plasma and liver showed very long-chain fatty acids, specific oxysterols and C bile acids intermediates elevation in ZSD mice along with a specific urine organic acid profile. With ageing, C fatty acid and phytanic acid levels tended to normalize in ZSD mice, as described in patients reaching adulthood. In conclusion, our mouse model recapitulates a mild ZSD phenotype and is suitable for liver-targeted therapies evaluation.
Topics: ATPases Associated with Diverse Cellular Activities; Alleles; Animals; Bile Acids and Salts; Cell Membrane; Female; Glucose-6-Phosphatase; Hepatocytes; Longitudinal Studies; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Oxysterols; RNA-Seq; Zellweger Syndrome
PubMed: 32693164
DOI: 10.1016/j.bbadis.2020.165900 -
Prenatal Diagnosis Sep 2020Conventional genetic tests (quantitative fluorescent-PCR [QF-PCR] and single nucleotide polymorphism-array) only diagnose ~40% of fetuses showing ultrasound...
OBJECTIVE
Conventional genetic tests (quantitative fluorescent-PCR [QF-PCR] and single nucleotide polymorphism-array) only diagnose ~40% of fetuses showing ultrasound abnormalities. Rapid exome sequencing (rES) may improve this diagnostic yield, but includes challenges such as uncertainties in fetal phenotyping, variant interpretation, incidental unsolicited findings, and rapid turnaround times. In this study, we implemented rES in prenatal care to increase diagnostic yield.
METHODS
We prospectively studied 55 fetuses. Inclusion criteria were: (a) two or more independent major fetal anomalies, (b) hydrops fetalis or bilateral renal cysts alone, or (c) one major fetal anomaly and a first-degree relative with the same anomaly. In addition to conventional genetic tests, we performed trio rES analysis using a custom virtual gene panel of ~3850 Online Mendelian Inheritance in Man (OMIM) genes.
RESULTS
We established a genetic rES-based diagnosis in 8 out of 23 fetuses (35%) without QF-PCR or array abnormalities. Diagnoses included MIRAGE (SAMD9), Zellweger (PEX1), Walker-Warburg (POMGNT1), Noonan (PTNP11), Kabuki (KMT2D), and CHARGE (CHD7) syndrome and two cases of Osteogenesis Imperfecta type 2 (COL1A1). In six cases, rES diagnosis aided perinatal management. The median turnaround time was 14 (range 8-20) days.
CONCLUSION
Implementing rES as a routine test in the prenatal setting is challenging but technically feasible, with a promising diagnostic yield and significant clinical relevance.
Topics: Abnormalities, Multiple; Adult; Diagnostic Tests, Routine; Feasibility Studies; Female; Fetus; Genetic Testing; Humans; Infant, Newborn; Male; Netherlands; Polymerase Chain Reaction; Polymorphism, Single Nucleotide; Predictive Value of Tests; Pregnancy; Pregnancy Outcome; Prenatal Diagnosis; Prospective Studies; Ultrasonography, Prenatal; Exome Sequencing
PubMed: 32627857
DOI: 10.1002/pd.5781 -
Molecular Genetics and Metabolism... Sep 2020Peroxisomal biogenesis disorders (PBD) are rare autosomal recessive disorders with various degrees of severity caused by hypomorphic mutations in 13 different peroxin...
Peroxisomal biogenesis disorders (PBD) are rare autosomal recessive disorders with various degrees of severity caused by hypomorphic mutations in 13 different peroxin (PEX) genes. In this study, we report the clinical and molecular characterization of a 9-years-old female presenting an apparently isolated pre-lingual sensorineural hearing loss (SNHL) and early onset Retinitis Pigmentosa (RP) that may clinically overlap with Usher syndrome. Genetic testing by clinical exome sequencing identified two variants in : the missense variant c.274G > C; p.(Val92Leu) that was already reported in a PBD patient, and the variant c.2140_2145dup; p.(Ser714_Gln715dup) which is a novel, non-frameshift variant, absent in control databases. On the basis of the molecular analysis, a thorough clinical examination revealed nail and dental abnormalities, a mild cognitive impairment, learning disabilities and poor feeding, apart from the retinal and audiological features initially identified. The clinical and molecular findings led us to the diagnosis of a mild form of PBD. This study further emphasizes that mild forms of PBD can be a differential diagnosis of Usher syndrome and suggests that patients with mild cognitive impairment associated to visual and hearing loss should perform a comprehensive mutation screening that includes genes.
PubMed: 32596134
DOI: 10.1016/j.ymgmr.2020.100615 -
The European Respiratory Journal Oct 2020Major epidemics, including some that qualify as pandemics, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), HIV, influenza A... (Review)
Review
Epidemic and pandemic viral infections: impact on tuberculosis and the lung: A consensus by the World Association for Infectious Diseases and Immunological Disorders (WAidid), Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases...
Major epidemics, including some that qualify as pandemics, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), HIV, influenza A (H1N1)pdm/09 and most recently COVID-19, affect the lung. Tuberculosis (TB) remains the top infectious disease killer, but apart from syndemic TB/HIV little is known regarding the interaction of viral epidemics and pandemics with TB. The aim of this consensus-based document is to describe the effects of viral infections resulting in epidemics and pandemics that affect the lung (MERS, SARS, HIV, influenza A (H1N1)pdm/09 and COVID-19) and their interactions with TB. A search of the scientific literature was performed. A writing committee of international experts including the European Centre for Disease Prevention and Control Public Health Emergency (ECDC PHE) team, the World Association for Infectious Diseases and Immunological Disorders (WAidid), the Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Mycobacterial Infections (ESGMYC) was established. Consensus was achieved after multiple rounds of revisions between the writing committee and a larger expert group. A Delphi process involving the core group of authors (excluding the ECDC PHE team) identified the areas requiring review/consensus, followed by a second round to refine the definitive consensus elements. The epidemiology and immunology of these viral infections and their interactions with TB are discussed with implications for diagnosis, treatment and prevention of airborne infections (infection control, viral containment and workplace safety). This consensus document represents a rapid and comprehensive summary on what is known on the topic.
Topics: BCG Vaccine; Betacoronavirus; COVID-19; Coronavirus Infections; Epidemics; HIV Infections; Humans; Influenza A Virus, H1N1 Subtype; Influenza, Human; Lung; Middle East Respiratory Syndrome Coronavirus; Pandemics; Pneumonia, Viral; Public Health; Respiratory Tract Infections; SARS-CoV-2; Severe Acute Respiratory Syndrome; Tuberculosis; Virus Diseases
PubMed: 32586885
DOI: 10.1183/13993003.01727-2020 -
Molecular Genetics and Metabolism... Jun 2020
PubMed: 32373468
DOI: 10.1016/j.ymgmr.2020.100590 -
The EMBO Journal Jun 2020Primary cilia are antenna-like organelles on the surface of most mammalian cells that receive sonic hedgehog (Shh) signaling in embryogenesis and carcinogenesis....
Primary cilia are antenna-like organelles on the surface of most mammalian cells that receive sonic hedgehog (Shh) signaling in embryogenesis and carcinogenesis. Cellular cholesterol functions as a direct activator of a seven-transmembrane oncoprotein called Smoothened (Smo) and thereby induces Smo accumulation on the ciliary membrane where it transduces the Shh signal. However, how cholesterol is supplied to the ciliary membrane remains unclear. Here, we report that peroxisomes are essential for the transport of cholesterol into the ciliary membrane. Zellweger syndrome (ZS) is a peroxisome-deficient hereditary disorder with several ciliopathy-related features and cells from these patients showed a reduced cholesterol level in the ciliary membrane. Reverse genetics approaches revealed that the GTP exchange factor Rabin8, the Rab GTPase Rab10, and the microtubule minus-end-directed kinesin KIFC3 form a peroxisome-associated complex to control the movement of peroxisomes along microtubules, enabling communication between peroxisomes and ciliary pocket membranes. Our findings suggest that insufficient ciliary cholesterol levels may underlie ciliopathies.
Topics: Cells, Cultured; Cholesterol; Cilia; Germinal Center Kinases; Humans; Kinesins; Microtubules; Smoothened Receptor; Zellweger Syndrome; rab GTP-Binding Proteins
PubMed: 32368833
DOI: 10.15252/embj.2019103499