3-Hydroxyisobutyric acid dehydrogenase deficiency: Expanding the clinical spectrum and quantitation of D- and L-3-Hydroxyisobutyric acid by an LC-MS/MS method.

A deficiency of 3-hydroxyisobutyric acid dehydrogenase (HIBADH) has been recently identified as a cause of primary 3-hydroxyisobutyric aciduria in two siblings; the only previously recognized primary cause had been a deficiency of methylmalonic semialdehyde dehydrogenase, the enzyme that is immediately downstream of HIBADH in the valine catabolic pathway and is encoded by the ALDH6A1 gene. Here we report on three additional patients from two unrelated families who present with marked and persistent elevations of urine L-3-hydroxyisobutyric acid (L-3HIBA) and a range of clinical findings. Molecular genetic analyses revealed novel, homozygous variants in the HIBADH gene that are private within each family.

Phenotype and pathology of the dilated cardiomyopathy with ataxia syndrome in children.

The dilated cardiomyopathy with ataxia syndrome (DCMA) is an autosomal recessive mitochondrial disease caused by mutations in the DnaJ heat shock protein family (Hsp40) member C19 (DNAJC19) gene. DCMA or 3-methylglutaconic aciduria type V is globally rare, but the largest number of patients in the world is found in the Hutterite population of southern Alberta in Canada. We provide an update on phenotypic findings, natural history, pathological findings, and our clinical experience.

SS-31 Peptide Reverses the Mitochondrial Fragmentation Present in Fibroblasts From Patients With DCMA, a Mitochondrial Cardiomyopathy.

We used patient dermal fibroblasts to characterize the mitochondrial abnormalities associated with the dilated cardiomyopathy with ataxia syndrome (DCMA) and to study the effect of the mitochondrially-targeted peptide SS-31 as a potential novel therapeutic. DCMA is a rare and understudied autosomal recessive disorder thought to be related to Barth syndrome but caused by mutations in , a protein of unknown function localized to the mitochondria. The clinical disease is characterized by 3-methylglutaconic aciduria, dilated cardiomyopathy, abnormal neurological development, and other heterogeneous features.

Transiently elevated plasma methionine, -adenosylmethionine and -adenosylhomocysteine: Unreported laboratory findings in a patient with NGLY1 deficiency, a congenital disorder of deglycosylation.

We report on a 5-year-old female born to consanguineous parents, ascertained at the age of 23 months for an elevated plasma methionine level, a mildly abnormal total plasma homocysteine (tHcy), and elevated aminotransferases. She had global developmental delay, microcephaly, dysmorphic facial features, hypotonia, nystagmus and tremor in her upper extremities. Metabolic investigations demonstrated elevations in plasma methionine, plasma -adenosylmethionine (SAM) and plasma -adenosylhomocysteine (SAH), with normal urine adenosine levels.

Characterization of the C584R variant in the mtDNA depletion syndrome gene FBXL4, reveals a novel role for FBXL4 as a regulator of mitochondrial fusion.

Mutations in FBXL4 (F-Box and Leucine rich repeat protein 4), a nuclear-encoded mitochondrial protein with an unknown function, cause mitochondrial DNA depletion syndrome. We report two siblings, from consanguineous parents, harbouring a previously uncharacterized homozygous variant in FBXL4 (c.1750 T > C; p.

D-2-hydroxyglutaric aciduria in a patient with speech delay due to a novel homozygous deletion in the gene.

D-2-hydroxyglutaric aciduria is a rare neurometabolic condition with a variable clinical spectrum. Here we report on a patient with speech delay, ascertained for an elevated urine 2-hydroxyglutaric acid levels, and found to have a novel pathogenic homozygous deletion in (NG_012012.1(NM_152783.

Hybrid gel electrophoresis using skin fibroblasts to aid in diagnosing mitochondrial disease.

Objective: We developed a novel, hybrid method combining both blue-native (BN-PAGE) and clear-native (CN-PAGE) polyacrylamide gel electrophoresis, termed BCN-PAGE, to perform in-gel activity stains on the mitochondrial electron transport chain (ETC) complexes in skin fibroblasts.

Methods: Four patients aged 46-65 years were seen in the Metabolic Clinic at Alberta Children's Hospital and investigated for mitochondrial disease and had BN-PAGE or CN-PAGE on skeletal muscle that showed incomplete assembly of complex V (CV) in each patient. Long-range PCR performed on muscle-extracted DNA identified 4 unique mitochondrial DNA (mtDNA) deletions spanning the gene of CV.

Pivotal role of inter-organ aspartate metabolism for treatment of mitochondrial aspartate-glutamate carrier 2 (citrin) deficiency, based on the mouse model.

Previous studies using citrin/mitochondrial glycerol-3-phosphate (G3P) dehydrogenase (mGPD) double-knockout mice have demonstrated that increased dietary protein reduces the extent of carbohydrate-induced hyperammonemia observed in these mice. This study aimed to further elucidate the mechanisms of this effect. Specific amino acids were initially found to decrease hepatic G3P, or increase aspartate or citrulline levels, in mGPD-knockout mice administered ethanol.

is a mitochondrial disease gene causing skeletal dysplasia, cataracts, and white matter changes.

Exome sequencing of two sisters with congenital cataracts, short stature, and white matter changes identified compound heterozygous variants in the gene, encoding the phosphatidylserine decarboxylase enzyme that converts phosphatidylserine to phosphatidylethanolamine (PE) in the inner mitochondrial membrane (IMM). Decreased conversion of phosphatidylserine to PE in patient fibroblasts is consistent with impaired phosphatidylserine decarboxylase (PISD) enzyme activity. Meanwhile, as evidence for mitochondrial dysfunction, patient fibroblasts exhibited more fragmented mitochondrial networks, enlarged lysosomes, decreased maximal oxygen consumption rates, and increased sensitivity to 2-deoxyglucose.

The relationship between d-beta-hydroxybutyrate blood concentrations and seizure control in children treated with the ketogenic diet for medically intractable epilepsy.

Objective: The ketogenic diet (KD) is a proven treatment for drug-resistant (DR) seizures in children and adolescents. However, the relationship between seizure control and the most commonly measured metabolite of the diet, the ketone body d-beta-hydroxybutyrate (D-BHB), is controversial. This study was performed to clarify the relationship because specific ketone bodies may be useful as biomarkers of diet efficacy.

ALG9-CDG: New clinical case and review of the literature.

Congenital disorders of glycosylation (CDG) are a group of metabolic diseases resulting from defects in glycan synthesis or processing. The number of subgroups and their phenotypic spectrums continue to expand with most related to deficiencies of N-glycosylation. ALG9-CDG (previously CDG-IL) is the result of a mutation in .

A New Patient With Intermediate Severe Salla Disease With Hypomyelination: A Literature Review for Salla Disease.

Background: Likely pathogenic variants in SLC17A5 results in allelic disorders of free sialic acid metabolism including (1) infantile free sialic acid storage disease with severe global developmental delay, coarse facial features, hepatosplenomegaly, and cardiomegaly; (2) intermediate severe Salla disease with moderate to severe global developmental delay, hypotonia, and hypomyelination with or without coarse facial features, and (3) Salla disease with normal appearance, mild cognitive dysfunction, and spasticity.

Patient Description: This five-year-old girl presented with infantile-onset severe global developmental delay, truncal hypotonia, and generalized dystonia following normal development during her first six months of life. Brain magnetic resonance imaging showed marked hypomyelination and a thin corpus callosum at age 19 months, both unchanged on follow-up at age 28 months.

Oral aversion to dietary sugar, ethanol and glycerol correlates with alterations in specific hepatic metabolites in a mouse model of human citrin deficiency.

Mice carrying simultaneous homozygous mutations in the genes encoding citrin, the mitochondrial aspartate-glutamate carrier 2 (AGC2) protein, and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD), are a phenotypically representative model of human citrin (a.k.a.

Genetic control of obesity, glucose homeostasis, dyslipidemia and fatty liver in a mouse model of diet-induced metabolic syndrome.

Background/objectives: Both genetic and dietary factors contribute to the metabolic syndrome (MetS) in humans and animal models. Characterizing their individual roles as well as relationships among these factors is critical for understanding MetS pathogenesis and developing effective therapies. By studying phenotypic responsiveness to high-risk versus control diet in two inbred mouse strains and their derivatives, we estimated the relative contributions of diet and genetic background to MetS, characterized strain-specific combinations of MetS conditions, and tested genetic and phenotypic complexity on a single substituted chromosome.

Mechanism for increased hepatic glycerol synthesis in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double-knockout mouse: Urine glycerol and glycerol 3-phosphate as potential diagnostic markers of human citrin deficiency.

The mitochondrial aspartate-glutamate carrier isoform 2 (citrin) and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) double-knockout mouse has been a useful model of human citrin deficiency. One of the most prominent findings has been markedly increased hepatic glycerol 3-phosphate (G3P) following oral administration of a sucrose solution. We aimed to investigate whether this change is detectable outside of the liver, and to explore the mechanism underlying the increased hepatic G3P in these mice.

A novel genetic locus linked to pro-inflammatory cytokines after virulent H5N1 virus infection in mice.

Background: Genetic variation in the human population is a key determinant of influenza disease severity. A single nucleotide polymorphism in the antiviral gene IFITM3 was linked to outcomes during the 2009 H1N1 pandemic. To identify variant host genes associated with increased virus replication and severe disease, we performed a quantitative trait locus analysis on pro-inflammatory cytokine production 48 hours after intranasal infection with highly pathogenic H5N1 influenza virus.

Effects of supplementation on food intake, body weight and hepatic metabolites in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double-knockout mouse model of human citrin deficiency.

The C57BL/6:Slc23a13(-/-);Gpd2(-/-) double-knockout (a.k.a.

Metabolomic analysis reveals hepatic metabolite perturbations in citrin/mitochondrial glycerol-3-phosphate dehydrogenase double-knockout mice, a model of human citrin deficiency.

The citrin/mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) double-knockout mouse displays phenotypic attributes of both neonatal intrahepatic cholestasis and adult-onset type II citrullinemia, making it a suitable model of human citrin deficiency. In the present study, we investigated metabolic disturbances in the livers of wild-type, citrin (Ctrn) knockout, mGPD knockout, and Ctrn/mGPD double-knockout mice following oral sucrose versus saline administration using metabolomic approaches. By using gas chromatography/mass spectrometry and capillary electrophoresis/mass spectrometry, we found three general groupings of metabolite changes in the livers of the double-knockout mice following sucrose administration that were subsequently confirmed using liquid chromatography/mass spectrometry or enzymatic methods: a marked increase of hepatic glycerol 3-phosphate, a generalized decrease of hepatic tricarboxylic acid cycle intermediates, and alterations of hepatic amino acid levels related to the urea cycle or lysine catabolism including marked increases in citrulline and lysine.

Analyzing complex traits with congenic strains.

Congenic strains continue to be a fundamental resource for dissecting the genetic basis of complex traits. Traditionally, genetic variants (QTLs) that account for phenotypic variation in a panel of congenic strains are sought first by comparing phenotypes for each strain to the host (reference) strain, and then by examining the results to identify a common chromosome segment that provides the best match between genotype and phenotype across the panel. However, this "common-segment" method has significant limitations, including the subjective nature of the genetic model and an inability to deal formally with strain phenotypes that do not fit the model.

Genetic resistance to diet-induced obesity in chromosome substitution strains of mice.

Discovery of genes that confer resistance to diseases such as diet-induced obesity could have tremendous therapeutic impact. We previously demonstrated that the C57BL/6J-Chr(A/J)/NaJ panel of chromosome substitution strains (CSSs) is a unique model for studying resistance to diet-induced obesity. In the present study, three replicate CSS surveys showed remarkable consistency, with 13 A/J-derived chromosomes reproducibly conferring resistance to high-fat-diet-induced obesity.

Baseline characteristics of patients enrolled in the Canadian Fabry Disease Initiative.

The Canadian Fabry Disease Initiative [CFDI] is a longitudinal study evaluating all Canadians diagnosed with Fabry disease [FD]. The study has 3 cohorts: Cohort 1A which includes 81 subjects who were on enzyme replacement therapy [ERT] prior to October 2006, Cohort 1B which has ongoing enrolment of subjects newly started on ERT who are randomized to agalsidase alfa or agalsidase beta, and Cohort 1C where subjects who do not meet nationally accepted Canadian criteria for ERT are followed to assess the natural history of disease complications. The study currently enrols 244 patients [95 males and 149 females] with a mean age of 41.

Genetic factors for resistance to diet-induced obesity and associated metabolic traits on mouse chromosome 17.

Obesity is associated with increased susceptibility to dyslipidemia, insulin resistance, and hypertension, a combination of traits that comprise the traditional definition of the metabolic syndrome. Recent evidence suggests that obesity is also associated with the development of nonalcoholic fatty liver disease (NAFLD). Despite the high prevalence of obesity and its related conditions, their etiologies and pathophysiology remains unknown.

Genetic architecture of complex traits: large phenotypic effects and pervasive epistasis.

The genetic architecture of complex traits underlying physiology and disease in most organisms remains elusive. We still know little about the number of genes that underlie these traits, the magnitude of their effects, or the extent to which they interact. Chromosome substitution strains (CSSs) enable statistically powerful studies based on testing engineered inbred strains that have single, unique, and nonoverlapping genetic differences, thereby providing measures of phenotypic effects that are attributable to individual chromosomes.

Citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice recapitulate features of human citrin deficiency.

Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human citrin deficiency.

Mice with a deletion in the gene for CCAAT/enhancer-binding protein beta are protected against diet-induced obesity.

The CCAAT/enhancer-binding protein beta (C/EBPbeta) is required for adipocyte differentiation and maturation. We have studied the role of the transcription factor, C/EBPbeta, in the development of diet-induced obesity. Mice with a deletion in the gene for C/EBPbeta (C/EBPbeta(-/-)) and wild-type mice were fed a high-fat diet (60% fat) for 12 weeks.