A knock-in rat model unravels acute and chronic renal toxicity in glutaric aciduria type I.

Glutaric aciduria type I (GA-I, OMIM # 231670) is an autosomal recessive inborn error of metabolism caused by deficiency of the mitochondrial enzyme glutaryl-CoA dehydrogenase (GCDH). The principal clinical manifestation in GA-I patients is striatal injury most often triggered by catabolic stress. Early diagnosis by newborn screening programs improved survival and reduced striatal damage in GA-I patients. However, the clinical phenotype is still evolving in the aging patient population. Evaluation of long-term outcome in GA-I patients recently identified glomerular filtration rate (GFR) decline with increasing age. We recently created the first knock-in rat model for GA-I harboring the mutation p.R411W (c.1231 C>T), corresponding to the most frequent GCDH human mutation p.R402W. In this study, we evaluated the effect of an acute metabolic stress in form of high lysine diet (HLD) on young Gcdhki/ki rats. We further studied the chronic effect of GCDH deficiency on kidney function in a longitudinal study on a cohort of Gcdhki/ki rats by repetitive 68Ga-EDTA positron emission tomography (PET) renography, biochemical and histological analyses. In young Gcdhki/ki rats exposed to HLD, we observed a GFR decline and biochemical signs of a tubulopathy. Histological analyses revealed lipophilic vacuoles, thinning of apical brush border membranes and increased numbers of mitochondria in proximal tubular (PT) cells. HLD also altered OXPHOS activities and proteome in kidneys of Gcdhki/ki rats. In the longitudinal cohort, we showed a progressive GFR decline in Gcdhki/ki rats starting at young adult age and a decline of renal clearance. Histopathological analyses in aged Gcdhki/ki rats revealed tubular dilatation, protein accumulation in PT cells and mononuclear infiltrations. These observations confirm that GA-I leads to acute and chronic renal damage. This raises questions on indication for follow-up on kidney function in GA-I patients and possible therapeutic interventions to avoid renal damage.

COVID-19 triggered encephalopathic crisis in a patient with glutaric aciduria type 1.

OBJECTIVES: The impact of coronavirus disease-19 (COVID-19) on metabolic outcome in patients with inborn errors of metabolism has rarely been discussed. Herein, we report a case with an acute encephalopathic crisis at the course of COVID-19 disease as the first sign of glutaric aciduria type 1 (GA-1). CASE PRESENTATION: A 9-month-old patient was admitted with encephalopathy and acute loss of acquired motor skills during the course of COVID-19 disease. She had lethargy, hypotonia, and choreoathetoid movements. In terms of COVID-19 encephalopathy, the reverse transcription-polymerase chain reaction assay test for COVID-19 was negative in cerebral spinal fluid. Brain imaging showed frontotemporal atrophy, bilateral subcortical and periventricular white matter, basal ganglia, and thalamic involvement. Elevated glutarylcarnitine in plasma and urinary excretion of glutaric and 3-OH-glutaric acids was noted. A homozygote mutation in the glutaryl-CoA dehydrogenase gene led to the diagnosis of GA-1. CONCLUSIONS: With this report, neurological damage associated with COVID-19 has been reported in GA-1 patients for the first time in literature.

The biochemical subtype is a predictor for cognitive function in glutaric aciduria type 1: a national prospective follow-up study.

The aim of the study was a systematic evaluation of cognitive development in individuals with glutaric aciduria type 1 (GA1), a rare neurometabolic disorder, identified by newborn screening in Germany. This national, prospective, observational, multi-centre study includes 107 individuals with confirmed GA1 identified by newborn screening between 1999 and 2020 in Germany. Clinical status, development, and IQ were assessed using standardized tests. Impact of interventional and non-interventional parameters on cognitive outcome was evaluated. The majority of tested individuals (n = 72) showed stable IQ values with age (n = 56 with IQ test; median test age 11 years) but a significantly lower performance (median [IQR] IQ 87 [78-98]) than in general population, particularly in individuals with a biochemical high excreter phenotype (84 [75-96]) compared to the low excreter group (98 [92-105]; p = 0.0164). For all patients, IQ results were homogenous on subscale levels. Sex, clinical motor phenotype and quality of metabolic treatment had no impact on cognitive functions. Long-term neurologic outcome in GA1 involves both motor and cognitive functions. The biochemical high excreter phenotype is the major risk factor for cognitive impairment while cognitive functions do not appear to be impacted by current therapy and striatal damage. These findings implicate the necessity of new treatment concepts.

Elevated levels of urine isocitrate, hydroxymethylglutarate, and formiminoglutamate are associated with arterial stiffness in Korean adults.

Recent evidence suggests that cellular perturbations play an important role in the pathogenesis of cardiovascular diseases. Therefore, we analyzed the association between the levels of urinary metabolites and arterial stiffness. Our cross-sectional study included 330 Korean men and women. The brachial-ankle pulse wave velocity was measured as a marker of arterial stiffness. Urinary metabolites were evaluated using a high-performance liquid chromatograph-mass spectrometer. The brachial-ankle pulse wave velocity was found to be positively correlated with L-lactate, citrate, isocitrate, succinate, malate, hydroxymethylglutarate, α-ketoisovalerate, α-keto-ß-methylvalerate, methylmalonate, and formiminoglutamate among men. Whereas, among women, the brachial-ankle pulse wave velocity was positively correlated with cis-aconitate, isocitrate, hydroxymethylglutarate, and formiminoglutamate. In the multivariable regression models adjusted for conventional cardiovascular risk factors, three metabolite concentrations (urine isocitrate, hydroxymethylglutarate, and formiminoglutamate) were independently and positively associated with brachial-ankle pulse wave velocity. Increased urine isocitrate, hydroxymethylglutarate, and formiminoglutamate concentrations were associated with brachial-ankle pulse wave velocity and independent of conventional cardiovascular risk factors. Our findings suggest that metabolic disturbances in cells may be related to arterial stiffness.

Coincidence of 3-methylglutaconic aciduria and duplication 5q - a case report and literature review.

3-methylglutaconic aciduria includes a heterogeneous group of inborn errors of metabolism. The disease may have various clinical presentations, as can duplication 5q. We present the case of a 13-year-old boy with 3-methylglutaconic aciduria and duplication 5q. The main symptoms included myopathy, weakness, spastic paresis intensified mostly in the lower limbs, and intellectual disability. Additional studies showed elevated levels of 3-methylglutaconic acid in urine and ammonia in plasma. A duplication in region 5q23.3q31.1 was found in array-based comparative genomic hybridization. Next-generation sequencing did not reveal any pathological mutation. On the basis of the clinical picture and the results of biochemical and genetic tests 3-methylglutaconic aciduria type IV with duplication 5q was diagnosed.

Microbial and metabolomic profiles in correlation with depression and anxiety co-morbidities in diarrhoea-predominant IBS patients.

BACKGROUND: Psychological co-morbidities in irritable bowel syndrome (IBS) have been widely recognized, whereas less is known regarding the role of gut microbial and host metabolic changes in clinical and psychological symptoms in IBS. RESULTS: A total of 70 diarrhoea-predominant IBS (IBS-D) patients and 46 healthy controls were enrolled in this study. Stool and urine samples were collected from both groups for 16S rRNA gene sequencing and metabolomic analysis. The results showed that fecal microbiota in IBS-D featured depleted Faecalibacterium (adjusted P = 0.034), Eubacterium rectale group (adjusted P = 0.048), Subdoligranulum (adjusted P = 0.041) and increased Prevotella (adjusted P = 0.041). O-ureido-L-serine, 3,4-dihydroxybenzenesulfonic acid and (R)-2-Hydroxyglutarate demonstrated lower urinary concentrations in IBS-D patients. We further built correlation matrices between gut microbe abundance, differentiated metabolite quantities and clinical parameters. Dialister manifested negative association with IBS severity (r = - 0.285, P = 0.017), anxiety (r = - 0.347, P = 0.003) and depression level (r = - 0.308, P = 0.010). Roseburia was negatively associated with IBS severity (r = - 0.298, P = 0.012). Twenty metabolites correlated with anxiety or depression levels, including 3,4-dihydroxymandelaldehyde with SAS (r = - 0.383, P = 0.001), 1-methylxanthine with SDS (r = - 0.347, P = 0.004) and 1D-chiro-inositol with SAS (r = - 0.336, P = 0.005). In analysis of microbe-metabolite relationship, 3,4-dihydroxymandelaldehyde and 1-methylxanthine were negatively correlated with relative abundance of Clostridiumsensu stricto. CONCLUSIONS: Our findings demonstrated altered microbial and metabolomic profiles associated with clinically and psychological symptoms in IBS-D patients, which may provide insights for further investigations.

Delayed appearance of 3-methylglutaconic aciduria in neonates with early onset metabolic cardiomyopathies: A potential pitfall for the diagnosis.

Infantile onset cardiomyopathies are highly heterogeneous with several phenocopies compared with adult cardiomyopathies. Multidisciplinary management is essential in determining the underlying etiology in children's cardiomyopathy. Elevated urinary excretion of 3-methylglutaconic acid (3-MGA) is a useful tool in identifying the etiology in some metabolic cardiomyopathy. Here, we report the delayed appearance of 3-MGA-uria, between 6 and 18 months in three patients (out of 100 childhood onset cardiomyopathy) with neonatal onset cardiomyopathy, secondary to TMEM70 mutations and TAZ mutations (Barth syndrome), in whom extensive metabolic investigations, performed in the first weeks of life, did not display 3-MGA-uria. Serial retrospective evaluations showed full characteristic features of TMEM70 and TAZ mutations (Barth syndrome) in these three patients, including a clearly abnormal monolysocardiolipin/cardiolipin ratio in the two Barth syndrome patients. Serially repeated metabolic investigations finally discovered the 3-MGA-uria biomarker in all three patients between the age of 6 and 18 months. Our observation provides novel insights into the temporal appearance of 3-MGA-uria in TMEM70 and TAZ mutations (Barth syndrome) and focus the importance of multidisciplinary management and careful evaluation of family history and red flag signs for phenocopies in infantile onset cardiomyopathies.

Severe clinical manifestation of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency associated with two novel mutations: a case report.

BACKGROUND: Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHS) deficiency is an autosomal recessive inborn error of metabolism, which will give rise to failure of ketogenesis in liver during illness or fasting. It is a very rare disease with only a few patients reported worldwide, most of which had a good prognosis after proper therapies. CASE PRESENTATION: We report a 9-month-old boy with mHS deficiency presenting with unusually severe and persistent acidosis after diarrhea and reduced oral food intake. The metabolic acidosis persisted even after supplementation with sugar and alkaline solution. Blood purification and assisted respiration alleviated symptoms, but a second onset induced by respiratory infection several days later led to multiple organ failure and death. Urine organic acid analysis during the acute episode revealed a complex pattern of ketogenic dicarboxylic and 3-hydroxydicarboxylic aciduria with prominent elevation of glutaric acid and adipic acid, which seem to be specific to mHS deficiency. Plasma acylcarnitine analysis revealed elevated 3-hydroxybutyrylcarnitine and acetylcarnitine. This is the first report of elevated 3-hydroxybutyrylcarnitine in mHS deficiency. Whole exome sequencing revealed a novel compound heterozygous mutation in HMGCS2 (c.100C > T and c.1465delA). CONCLUSION: This severe case suggests the need for patients with mHS deficiency to avoid recurrent illness because it can induce severe metabolic crisis, possibly leading to death. Such patients may also require special treatment, such as blood purification. Urine organic acid profile during the acute episode may give a hint to the disease.

Novel homozygous OPA3 mutation in an Afghani family with 3-methylglutaconic aciduria type III and optic atrophy.

Purpose: To describe and distinguish clinical phenotypes with the overlapping feature of optic atrophy caused by distinct mutations in the same gene, OPA3. We report 3 affected siblings in a consanguineous family harboring a novel OPA3 mutation causing 3-methylglutaconic aciduria type III with optic atrophy.Methods: Retrospective case series.Results: Three siblings (2 male, 1 female) among 6 children in a consanguineous Afghani family developed decreased vision from early childhood. Both parents and all extended family members were unaffected. All 3 affected siblings suffered from severe visual impairment ranging from visual acuities of 20/150 to counting fingers. All had spastic lower extremity weakness and ataxia. Two of the three affected siblings also had a history of seizures, and the female sibling had limited cognition with diffuse atrophic changes on brain MRI. Two of the three individuals also had migraine-like headaches. Urine organic acid analysis revealed mildly elevated 3-methylglutaconic acid for the male siblings. Whole exome sequencing and subsequent PCR confirmation revealed a novel variant in OPA3 (intron1, c.142 + 2_142 + 3dupTG), affecting the consensus sequence of the splice site, for which all 3 clinically affected siblings were homozygous.Discussion: Mutations in OPA3 can cause optic atrophy in a dominant pattern of inheritance associated with cataract or in a recessive pattern associated with spastic paresis and ataxia. The novel recessive mutation and clinical presentations described herein further support how different mutation types affecting OPA3 can produce distinct clinical phenotypes and underscore the critical and susceptible role of mitochondrial health in optic nerve function.

Quantitation of plasma and urine 3-hydroxyglutaric acid, after separation from 2-hydroxyglutaric acid and other compounds of similar ion transition, by liquid chromatography-tandem mass spectrometry for the confirmation of glutaric aciduria type 1.

BACKGROUND: Glutaric aciduria type 1, a deficiency of glutaryl-CoA dehydrogenase, causes an accumulation of neurotoxic metabolites glutaric acid and 3-hydroxyglutaric acid (3-HGA). Testing of these analytes is routinely done by GC-MS but seldom account for interference from isomers or compounds with similar ion transitions. We developed a liquid chromatography tandem mass spectrometry method that accurately measures 3-HGA in urine and plasma specimens, while utilizing similar reagents and instrumentation used for the routine performance of amino acid and acylcarnitine analysis in determining the diagnosis of several metabolic disorders. METHOD: Plasma and urine samples were added aliquots of the deuterated 3-HGA internal standard and acetonitrile. The protein-free supernatant was brought to dryness, and the residue derivatized using 3 M HCL in 1-butanol with heating. The dried derivative was then reconstituted in 50% methanol-water solution and aliquot transferred to an HPLC vial for analysis by LC-MS/MS. Separation was performed using a C8 HPLC column under flow gradient conditions of 0.2% formic acid in water and methanol, respectively. Ionization was by ESI and detection of selected precursor-product ion transitions by multiple reaction monitoring (MRM) in positive mode. RESULTS: The butyl-ester derivative of 3-HGA eluted at 7.82 min while 2-hydroxyglutaric acid (2-HGA) eluted at 8.21 min. This was equivalent to a separation factor of 1.05 and a resolution of 1.03, respectively. The 3-HGA calibration curve was linear over the range 6.20-319 ng mL-1 (r2 = 0.9996), and the reportable range determined by the linearity was found to be 1.54-384 ng mL-1. The calculated limits of detection and quantitation were 0.348 and 1.56 ng mL-1, respectively. Intra- and Inter-assay %CVs for quality control plasma and urine samples ranged from 2 to 18%, with recoveries of 66-115%. The method correlated to the gold standard GC-MS method for both serum (r2 ≥ 0.996) and urine analysis (r2 ≥ 0.949). The concentration of 3-HGA in normal, non-GA1 individuals was ≤25.2 ng mL-1 (in plasma) and ≤ 35.0 µmol mmol-1 of creatinine (in urine). CONCLUSIONS: This LC-MS/MS method accurately quantified plasma and urine 3-HGA concentration after successful resolution from 2-HGA and other compounds with similar ion transitions. This method is suitable for confirmatory testing of 3-HGA, as a follow-up to an abnormal newborn screen test result, with concern for GA type 1.

A novel compound heterozygous mutation of the L2HGDH gene in a Chinese boy with L-2-hydroxyglutaric aciduria: case report and literature review.

OBJECTIVE: L-2-hydroxyglutaric aciduria is a genetic metabolic disorder. Its clinical features include elevated levels of hydroxyglutaric acid in body fluids and abnormal magnetic resonance imaging (MRI) in the subcortical white matter, which are affected by the accumulation of L-2-hydroxyglutaric acid. METHOD: A boy with psychomotor retardation and progressive ataxia accompanied by abnormal brain MRI findings was tested using whole-exome sequencing. RESULTS: Next-generation sequencing (NGS) revealed two novel compound heterozygous frameshift mutations, c.407 del A (p.K136SfsTer3) and c.699_c700 ins A (p.D234RfsTer42), in the L-2-hydroxyglutarate dehydrogenase (L2HGDH) gene, leading to premature termination codons and truncated FAD/NAD(P)-binding domain of L2HGDH protein. Further laboratory testing revealed an increase in the 2-hydroxyglutaric acid level in the urine. CONCLUSION: The results suggested that NGS could provide clues for identifying patients with abnormal neuroradiological findings in the subcortical white matter.

The urinary organic acids profile in single large-scale mitochondrial DNA deletion disorders.

Single large-scale mitochondrial DNA deletions disorders are classified into three main phenotypes with frequent clinical overlap: Pearson marrow-pancreas syndrome (PMS), Kearns-Sayre syndrome (KSS) and chronic progressive external ophtalmoplegia (PEO). So far, only few anecdotal studies have reported on the urinary organic acids profile in this disease class. In this single-center retrospective study, we performed quantitative evaluation of urinary organic acids in a series of 15 pediatric patients, 7 with PMS and 8 with KSS. PMS patients showed an organic acids profile almost constantly altered, whereas KSS patients frequently presented with normal profiles. Lactate, 3-hydroxybutyrate, 3-hydroxyisobutyrate, fumarate, pyruvate, 2-hydroxybutyrate, 2-ethyl-3-hydroxypropionate, and 3-methylglutaconate represented the most frequent metabolites observed in PMS urine. We also found novel metabolites, 3-methylglutarate, tiglylglycine and 2-methyl-2,3-dihydroxybutyrate, so far never reported in this disease. Interestingly, patients with a disease onset as PMS evolving overtime into KSS phenotype, presented persistent and more pronounced alterations of organic acid signature than in patients with a pure KSS phenotype. Our study shows that the quantitative analysis of urinary organic acid profile represents a helpful tool for the diagnosis of PMS and for the differential diagnosis with other inherited diseases causing abnormal organic acidurias.

Systematic assessment of urinary hydroxy-oxo-glutarate for diagnosis and follow-up of primary hyperoxaluria type III.

BACKGROUND: There are currently three distinct autosomal recessive inherited types of primary hyperoxaluria (PH: PHI, PHII, and PHIII), all characterized by the endogenous overproduction of oxalate. The PH type is difficult to differentiate by clinical features alone. In addition to universal general characteristics to all hyperoxaluria subtypes, specific urinary metabolites can be detected: glycolate in PHI, L-glyceric acid in PHII, and hydroxy-oxo-glutarate (HOG) in PHIII. PHIII is considered to be the most benign form and is characterized by severe recurrent urolithiasis in early life, followed by clinical remission in many, but not all patients. We examined urinary HOG (UHOG) excretion as a diagnostic marker and its correlation to progression of the clinical course of PHIII. METHODS: UHOG was analyzed by combined ion chromatography/mass spectrometry (IC/MS) in urine samples from 30 PHIII and 68 PHI/II patients and 79 non-PH hyperoxaluria patients. RESULTS: Mean UHOG excretion was significantly higher in patients with PHIII than in those with PHI/II and in non-PH patients(51.6 vs. 6.61 vs. 8.36 µmol/1.73 m2/24 h, respectively; p<0.01). CONCLUSIONS: Significantly elevated UHOG excretion was exclusively seen in PHIII patients and showed a 100 % consensus with the results of hydroxy-oxo-glutarate aldolase (HOGA1) mutational analysis in newly diagnosed patients. However, UHOG excretion did not correlate with clinical course on follow-up and could not be used to discriminate between active stone formers and patients with a clinically uneventful follow-up.

Selective screening of glutaric acid acidurias by capillary electrophoresis-mass spectrometry.

A sensitive and selective method for the separation and quantification of the three organic acids 3-hydroxy-3-methylglutaric acid, 3-methylglutaric acid, and glutaric acid in human urine samples by CE with mass spectrometry detection has been developed. This methodology is faster, simpler and less time-consuming, than other methodologies previously described, and requires of reduced amounts of reagents as well. Samples are first filtered and then diluted in water. For the electrophoretic separation, a 20mM ammonium acetate and 10% methanol solution at pH 9.1 was selected as the running electrolyte. With 5-s hydrodynamic injection, detection limits ranging from 15.5 to 39.3µM and linear responses ranging from the LOQ calculated for each analyte to more than 400µM were obtained for the analysis of the different organic acids in less than 13min. Remarkable selectivity is achieved by mass spectrometry detection using 0.25% of formic acid in 50% v/v 2-propanol-water solution as sheath liquid, and enough sensitivity without interferences from the matrices was obtained as well. This methodology has revealed as an efficient approach to help the 3-hydroxy-3-methylglutaric aciduria diagnoses in order to discard or confirm the occurrence of the disease as of the presence or absence of the expected increased levels of these analytes in samples of potential patients.

3-Methylglutaconic aciduria, a frequent but underrecognized finding in carbamoyl phosphate synthetase I deficiency.

The urea cycle disorder carbamoyl phosphate synthetase I deficiency is an important differential diagnosis in the encephalopathic neonate. This intoxication type inborn error of metabolism often leads to neonatal death or severe and irreversible damage of the central nervous system, even despite appropriate treatment. Timely diagnosis is crucial, but can be difficult on routine metabolite level. Here, we report ten neonates from eight families (finally) diagnosed with CPS1 deficiency at three tertiary metabolic centres. In seven of them the laboratory findings were dominated by significantly elevated urinary 3-methylglutaconic acid levels which complicated the diagnostic process. Our findings are both important for the differential diagnosis of patients with urea cycle disorders and also broaden the differential diagnosis of hyperammonemia associated with 3-methylglutaconic aciduria, which was earlier only reported in TMEM70 and SERAC1 defect.

In-vivo brain H1-MR-Spectroscopy identification and quantification of 2-hydroxyglutarate in L-2-Hydroxyglutaric aciduria.

UNLABELLED: L-2-Hydroxyglutaric aciduria (L2HGA) is an extremely rare hereditary neurometabolic disease, characterized by increased L-2-hydroxyglutarate (L2HG) levels in the brain and biological fluids. 24-h urine 2HG level remains the biochemical hallmark for the diagnosis of L2HGA, whereas it is unknown the feasibility to measure in vivo the intracerebral levels of 2HG by using magnetic resonance spectroscopy (MRS). PATIENTS AND METHODS: We used at 3T H(1)-MRS Single-Voxel (SV) PRESS sequences tailored to detect 2HG, in three adult patients with the diagnosis of L2HGA and in healthy controls. We also used mass spectrometric methods to measure the levels of 2HG in plasma and serum. RESULTS: 2HG peak was detected and quantified in the white matter (WM) of the three L2HGA patients, while it was absent in controls. All patients showed also high levels of 2HG in plasma and serum. CONCLUSIONS: Brain 2HG detected by MRS may play a role in the diagnosis and follow-up of L2HGA, besides circulating plasma/serum 2HG levels by mass spectrometric assays, although studies on a large cohort of patients are required to confirm these observations.

Enantioseparation of d,l-2-hydroxyglutaric acid by capillary electrophoresis with tandem mass spectrometry-Fast and efficient tool for d- and l-2-hydroxyglutaracidurias diagnosis.

A novel capillary electrophoresis-tandem mass spectrometry method for the enantioseparation and identification of 2-hydroxyglutaric acid enantiomers without derivatization for clinical purposes was described. Vancomycin chloride was used as an efficient chiral selector for the discrimination of 2-hydroxyglutaric acid enantiomers by capillary electrophoresis employed complete capillary filling method. The obtained resolution was 2.05. Hyphenation of CE with tandem mass spectrometry allows a reliable identification of separated enantiomers as well as their quantification. The method was validated and applied for the separation, identification and determination of 2-hydroxyglutaric enantiomers in urine samples obtained from healthy patients and two urine samples obtained from child patients suffering from high urine excretion of 2-hydroxyglutaric acid. Abnormal excretion of d-hydroxyglutaric acid was found in both child urine samples (104.5±2.1 and 2200.0±12.6mmol/mol of creatinine, respectively). The limits of detection for d- and l-hydroxyglutaric acid were 31 and 38nmol/L, respectively.