Left ventricular noncompaction cardiomyopathy and short QT syndrome due to primary carnitine deficiency.

We report the case of a 13-year-old female patient presenting with presyncope and palpitations. Her electrocardiogram revealed an abbreviation of the rate-corrected QT interval with imaging showing significant left ventricular dysfunction. Carnitine levels were measured as part of her diagnostic workup, discovering a rare, reversible cause of short QT syndrome (SQTS) and associated cardiomyopathy-primary carnitine deficiency (PCD) caused by a homozygous mutation in the SLC22A5 gene, leading to an in-frame deletion mutation (NP_003051.1:p.Phe23del) affecting the organic cation transporter 2 (OCTN2) protein. Following the treatment with oral carnitine supplementation, her QT interval returned to within the normal range with significant improvement in left ventricular function.

ETF dehydrogenase advances in molecular genetics and impact on treatment.

Electron transfer flavoprotein dehydrogenase, also called ETF-ubiquinone oxidoreductase (ETF-QO), is a protein localized in the inner membrane of mitochondria, playing a central role in the electron-transfer system. Indeed, ETF-QO mediates electron transport from flavoprotein dehydrogenases to the ubiquinone pool. ETF-QO mutations are often associated with riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency (RR-MADD, OMIM#231680), a multisystem genetic disease characterized by various clinical manifestations with different degrees of severity. In this review, we outline the clinical features correlated with ETF-QO deficiency and the benefits obtained from different treatments, such as riboflavin, L-carnitine and/or coenzyme Q10 supplementation, and a diet poor in fat and protein. Moreover, we provide a detailed summary of molecular and bioinformatic investigations, describing the mutations identified in ETFDH gene and highlighting their predicted impact on enzymatic structure and activity. In addition, we report biochemical and functional analysis, performed in HEK293 cells and patient fibroblasts and muscle cells, to show the relationship between the nature of ETFDH mutations, the variable impairment of enzyme function, and the different degrees of RR-MADD severity. Finally, we describe in detail 5 RR-MADD patients carrying different ETFDH mutations and presenting variable degrees of clinical symptom severity.

Clinical outcomes in a series of 18 patients with long chain fatty acids oxidation disorders treated with triheptanoin for a median duration of 22 months.

INTRODUCTION: Triheptanoin provides long-chain fatty acid oxidation disorder (LC-FAOD) patients with an alternative to medium-even-chain triglycerides therapy. MATERIAL-METHODS: Retrospective analysis of 18 French LC-FAOD patients benefiting from early access to triheptanoin treatment. RESULTS: Eight female and 10 male patients with LC-FAOD (VLCAD, LCHAD, CACT, CPTII and MTP) were treated with triheptanoin for a median duration of 22 months (range: 9-228 months). At last consultation, triheptanoin accounted for 15-35% of their daily caloric intake. In the year following the introduction of triheptanoin, patients reported a reduction of intermittent snacking and nocturnal meals. Three patients, including 1 adult, became free of severe hypoglycaemic events. Ten of 12 paediatric patients and 4 of 6 adult patients reported reduced fatigue with reductions in the number and severity of episodes of myalgia. Of 6 patients, including 1 adult, that had required the use of a wheelchair in the year prior to triheptanoin, all but one no longer required its use. The number of emergency hospitalizations decreased, and none were recorded for paediatric patients during these 12 months. Cumulative annual days of emergency care in the home were reduced from 286 to 51 days in the year before and after initiation, respectively, and 13 patients required no such interventions. Adverse events were limited to digestive issues that dissipated over time. CONCLUSIONS: Our case-series suggests that long-term treatment of LC-FAOD paediatric and adult patients with triheptanoin is safe and leads to marked improvement of symptoms and an improved quality of life.

[Clinical and genetic characteristics of primary carnitine deficiency identified by neonatal screening].

OBJECTIVE: To study the prevalence, clinical and genetic characteristics of primary carnitine deficiency (PCD). METHODS: From January 2013 to December 2017, 720 667 newborns and their mothers were tested for PCD by tandem mass spectrometry. Potential mutations of carnitine transporter gene SLC22A5 among suspected PCD patients were analyzed. Dietary guidance and L-carnitine supplementation were provided to the parents. Growth and intelligence development were surveyed during follow-up. RESULTS: In total 21 neonates and 6 mothers were diagnosed with PCD, which yielded an incidence of 1 in 34 317. Eighteen SLC22A5 mutations were detected, which included 4 novel mutations, namely c.1484T>C, c.394-1G>T, c.431T>C and c.265-266insGGCTCGCCACC. Eighteen patients were found to carry compound heterozygous mutations and 3 have carried homozygous SLC22A5 mutations. Three mothers carried compound heterozygous mutations and 2 carried homozygous mutations. Common mutations included c.1400C>G (42.3%), c.760C>T (11.5%) and c.51C>G (7.7%). During the 8-42 month follow-up, neonates with PCD showed no clinical symptoms but normal growth. Blood level of free carnitine was raised in all mothers after the treatment. CONCLUSION: The incidence of neonatal PCD in Henan is 1 in 34 317, with the most common mutation being c.1400C>G. Above finding has enriched the spectrum of SLC22A5 gene mutations.

Cardiac function and incidence of unexplained myocardial scarring in patients with primary carnitine deficiency - a cardiac magnetic resonance study.

Primary carnitine deficiency (PCD) not treated with L-Carnitine can lead to sudden cardiac death. To our knowledge, it is unknown if asymptomatic patients treated with L-Carnitine suffer from myocardial scarring and thus be at greater risk of potentially serious arrhythmia. Cardiac evaluation of function and myocardial scarring is non-invasively best supported by cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE). The study included 36 PCD patients, 17 carriers and 17 healthy subjects. A CMR cine stack in the short-axis plane were acquired to evaluate left ventricle (LV) systolic and diastolic function and a similar LGE stack to evaluate myocardial scarring and replacement fibrosis. LV volumes and ejection fraction were not different between PCD patients, carriers and healthy subjects. However, LV mass was higher in PCD patients with the severe homozygous mutation, c.95 A > G (p = 0.037; n = 17). Among homozygous PCD patients there were two cases of unexplained myocardial scarring and this is in contrast to no myocardial scarring in any of the other study participants (p = 0.10). LV mass was increased in PCD patients. L-carnitine supplementation is essential in order to prevent potentially lethal cardiac arrhythmia and serious adverse cardiac remodeling.

Molecular Autopsy Implicates Primary Carnitine Deficiency in Sudden Unexplained Death and Reversible Short QT Syndrome.

We report a case of sudden unexplained death in a young asymptomatic woman in whom postmortem genetic testing after a negative autopsy identified a homozygous pathogenic mutation in SLC22A5 which leads clinically to primary carnitine deficiency (PCD). Her brother was subsequently diagnosed clinically with short QT syndrome, received an implantable defibrillator, and was then found to carry the same pathogenic homozygous mutation and critically low levels of carnitine. His QT interval improved with the use of carnitine supplementation, highlighting the close relationship between electrophysiology and biochemistry, and the importance of postmortem genetic testing in the clinical management of surviving relatives.

A newborn with seizures born to a mother diagnosed with primary carnitine deficiency.

BACKGROUND: Maternofetal carnitine transport through the placenta is the main route of fetal carnitine uptake. Decreased free carnitine levels discovered by newborn screening has identified many asymptomatic adult women with systemic primary carnitine deficiency (PCD). Here, we presented amplitude integrated electroencephalogram (aEEG) and magnetic resonance imaging (MRI) findings from a neonate with epilepsy whose mother was carnitine deficient. CASE PRESENTATION: A one-day-old female newborn was admitted after experiencing seizures for half a day; status epilepticus was found on the continuous normal voltage background pattern with immature sleep-wake cycling during aEEG monitoring. On T1-weighted, T2-weighted, FLAIR, and DWI head MRI, there were various degrees of hyperintense signals and diffusion restrictions in the deep white matter of the right hemisphere. Tandem mass spectrometry discovered carnitine deficiency on the second day, which elevated to normal by the 9th day before L-carnitine supplementation was started. The patient was treated with phenobarbital after admission. No further seizures were noted by day 5. It was confirmed that the patient's mother had a low level of serum-free carnitine. Gene analyses revealed that the newborn had heterozygote mutations on c.1400C > G of the SLC22A5 gene, and her mother had homozygous mutations on c.1400C > G. The patient had a good outcome at the 8-month follow up. CONCLUSIONS: Maternal carnitine deficiency that occurs during the perinatal period may manifest as secondary epilepsy with cerebral injury in neonates. The short-term neurodevelopmental outcomes were good. Early diagnosis of asymptomatic PCD in female patients can provide guidance for future pregnancies.

Primary Carnitine Deficiency - A Rare Treatable Cause of Cardiomyopathy and Massive Hepatomegaly.

Systemic primary carnitine deficiency (CDSP) is a rare autosomal recessive disorder caused by a defect in plasma membrane uptake of carnitine due to SLC22A5 gene mutations. A nine-mo-old boy presented with hypertrophic cardiomyopathy, massive hepatomegaly and jaundice. Metabolic testing revealed very low free carnitine levels. Genetic analysis using Sanger sequencing method revealed compound heterozygous mutations in SLC22A5 gene, c. 1354 G > A (p. Glu452Lys, previously reported) and c.231_234del (novel frame-shift). Oral carnitine supplementation resulted in improved clinical outcome with ejection fraction to 75 % and normalization of liver size and enzymes after 3 mo.

Dilated Cardiomyopathy as the Only Clinical Manifestation of Carnitine Transporter Deficiency.

The authors present a case of carnitine transporter deficiency, which was unmasked after an episode of respiratory distress resistant to treatment with bronchodilators. Chest radiograph showed cardiomegaly; electrocardiogram showed left ventricular hypertrophy and echocardiography revealed dilated cardiomyopathy. Heart failure therapy was initiated and metabolic screening was requested, as family history was indicative of inborn errors of metabolism. Very low levels of free carnitine and carnitine esters in blood were found and genetic testing confirmed the diagnosis of carnitine transporter deficiency. After oral supplementation with L-carnitine, symptoms gradually ameliorated and heart function had fully recovered. Sequence analysis in the SLC22A5 gene revealed the missense mutation c.1319C > T (p.Th440Met) in homozygous state. Homozygous c.1319C > T (p.Th440Met) mutation has not been associated with a pure cardiac phenotype before.

Carnitine deficiency induces a short QT syndrome.

BACKGROUND: Short QT syndrome is associated with an increased risk of cardiac arrhythmias and unexpected sudden death. Until now, only mutations in genes encoding the cardiac potassium and calcium channels have been implicated in early T-wave repolarization. OBJECTIVE: The purpose of this study was to confirm a relationship between a short QT syndrome and carnitine deficiency. METHODS: We report 3 patients affected by primary systemic carnitine deficiency and an associated short QT syndrome. Ventricular fibrillation during early adulthood was the initial symptom in 1 case. To confirm the relationship between carnitine, short QT syndrome, and arrhythmias, we used a mouse model of carnitine deficiency induced by long-term subcutaneous perfusion of MET88. RESULTS: MET88-treated mice developed cardiac hypertrophy associated with a remodeling of the mitochondrial network. The continuous monitoring of electrocardiograms confirmed a shortening of the QT interval, which was negatively correlated with the plasma carnitine concentration. As in humans, such alterations coincided with the genesis of ventricular premature beats and ventricular tachycardia and fibrillation. CONCLUSION: Altogether, these results suggest that long-chain fatty acid metabolism influence the morphology and the electrical function of the heart.

Long-chain Acylcarnitines Reduce Lung Function by Inhibiting Pulmonary Surfactant.

The role of mitochondrial energy metabolism in maintaining lung function is not understood. We previously observed reduced lung function in mice lacking the fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD). Here, we demonstrate that long-chain acylcarnitines, a class of lipids secreted by mitochondria when metabolism is inhibited, accumulate at the air-fluid interface in LCAD(-/-) lungs. Acylcarnitine accumulation is exacerbated by stress such as influenza infection or by dietary supplementation with l-carnitine. Long-chain acylcarnitines co-localize with pulmonary surfactant, a unique film of phospholipids and proteins that reduces surface tension and prevents alveolar collapse during breathing. In vitro, the long-chain species palmitoylcarnitine directly inhibits the surface adsorption of pulmonary surfactant as well as its ability to reduce surface tension. Treatment of LCAD(-/-) mice with mildronate, a drug that inhibits carnitine synthesis, eliminates acylcarnitines and improves lung function. Finally, acylcarnitines are detectable in normal human lavage fluid. Thus, long-chain acylcarnitines may represent a risk factor for lung injury in humans with dysfunctional fatty acid oxidation.

Primary systemic carnitine deficiency: a Turkish case with a novel homozygous SLC22A5 mutation and 14 years follow-up.

Systemic primary carnitine deficiency is an autosomal recessive disorder caused by the deficiency of carnitine transporter. Main features are cardiomyopathy, myopathy and hypoglycemic encephalopathy. We report a Turkish case with a novel SLC22A5 gene mutation presented with a pure cardiac phenotype. During the 14-year follow-up study, cardiac functions were remained within a normal range with oral L-carnitine supplementation.

Improvement of regressive autism symptoms in a child with TMLHE deficiency following carnitine supplementation.

Disorders of carnitine biosynthesis have recently been associated with neurodevelopmental syndromes such as autism spectrum disorder (ASD). A 4-year-old male with autism and two episodes of neurodevelopmental regression was identified to have a mutation in the TMLHE gene, which encodes the first enzyme in the carnitine biosynthesis pathway, and concurrent carnitine deficiency. Following carnitine supplementation, the patient's regression ended, and the boy started gaining developmental milestones. This case report suggests that deficits in carnitine biosynthesis may be responsible for some cases of regression in individuals with ASD, and that testing for the respective biochemical pathway should be considered. Furthermore, this case suggests that carnitine supplementation may be useful in treating (and potentially preventing) regressive episodes in patients with carnitine deficiency. Further work to better define the role of disorders of carnitine biosynthesis in autism spectrum disorder is warranted.

Metabolic characterization of hepatocellular carcinoma using nontargeted tissue metabolomics.

Hepatocellular carcinoma has a poor prognosis due to its rapid development and early metastasis. In this report, we characterized the metabolic features of hepatocellular carcinoma using a nontargeted metabolic profiling strategy based on liquid chromatography-mass spectrometry. Fifty pairs of liver cancer samples and matched normal tissues were collected from patients having hepatocellular carcinoma, including tumor tissues, adjacent noncancerous tissues, and distal noncancerous tissues, and 105 metabolites were filtered and identified from the tissue metabolome. The principal metabolic alternations in HCC tumors included elevated glycolysis, gluconeogenesis, and ß-oxidation with reduced tricarboxylic acid cycle and Δ-12 desaturase. Furthermore, increased levels of glutathione and other antioxidative molecules, together with decreased levels of inflammatory-related polyunsaturated fatty acids and phospholipase A2, were observed. Differential metabolite levels in tissues were tested in 298 serum specimens from patients with chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Betaine and propionylcarnitine were confirmed to confer good diagnostic potential to distinguish hepatocellular carcinoma from chronic hepatitis and cirrhosis. External validation of cirrhosis and hepatocellular carcinoma serum specimens further showed that this combination biomarker is useful for diagnosis of hepatocellular carcinoma with a supplementary role to α-fetoprotein.

SLC22A5 mutations in a patient with systemic primary carnitine deficiency: the first Korean case confirmed by biochemical and molecular investigation.

Systemic primary carnitine deficiency (CDSP) is a rare autosomal recessive disorder that presents episodic periods of hypoketotic hypoglycemia. The main symptoms of CDSP are skeletal and cardiac myopathy. CDSP is caused by a defect in plasma membrane uptake of carnitine, ultimately caused by the SLC22A5 gene. We report the case of a Korean patient with CDSP. He had an abnormal free carnitine level of 5.56 µmol/L (reference range, RR 10.4~87.1 µmol/L) and a palmitoylcarnitine level of 0.27 µmol/L (RR 0.5~9.7 µmol/L) in a newborn screening test. The patient showed an ammonia level of 129.4 ug/dL (RR, 25~65 ug/dL), a lactate level of 4.5 mmol/L (RR, 0.5-2.2 mmol/L), and a free carnitine level of 10.3 µmol/L (RR, 36-74 µmol/L) in blood. After PCR-sequencing analysis of the SLC22A5 gene, the patient was found to be a compound heterozygote for c.506G>A (p.R169Q) and c.1400C>G (p.S467C) mutations. These missense mutations are reported previously. The patient was started on L-carnitine supplement after CDSP diagnosis. The patient was treated with L-carnitine to reach a normal free carnitine level and has remained asymptomatic up to the current age of 21 months. The plasma free carnitine level normalized to 66.6 µmol/L at 4 weeks after treatment. To the best of our knowledge, this is the first report of a CDSP patient confirmed by molecular genetic investigation.

[Primary carnitine deficiency in 17 patients: diagnosis, treatment and follow up].

OBJECTIVE: Many children were found to have low free carnitine level in blood by tandem mass spectrometry technology. In some of the cases the problems occurred secondary to malnutrition, organic acidemia and other fatty acid oxidation metabolic diseases, and some of cases had primary carnitine deficiency (PCD). In the present article, we discuss the diagnosis of PCD and evaluate the efficacy of carnitine in the treatment of PCD. METHOD: We measured the free carnitine (C0) and acylcarnitine levels in the blood of 270 000 neonates from newborns screening program and 12 000 children with suspected clinical inherited metabolic diseases by tandem mass spectrometry. The mutations of carnitine transporter protein were tested to the children with low C0 level and the diagnosis was made. The children with PCD were treated with 100 - 300 mg/kg of carnitine. RESULT: Seventeen children were diagnosed with PCD, 6 from newborn screening program and 11 from clinical patients. Mutations were found in all of them. The average C0 level [(2.9 ± 2.0) µmol/L] in patients was lower than the reference value (10 µmol/L), along with decreased level of different acylcarnitines. The clinical manifestations were diverse. For the 6 patients from newborn screening, 4 were asymptomatic, 1 showed hypoglycaemia and 1 showed movement intolerance from 2 years of age. For the 11 clinical patients, 8 showed hepatomegaly, 7 showed myasthenia, 6 showed cardiomyopathy, 1 showed chronic abdominal pain, and 1 showed restlessness and learning difficulty. Among these patients, 14 cases were treated with carnitine. Their clinical symptoms disappeared 1 to 3 months later. The C0 level in the blood rose to normal, with the average from (4.0 ± 2.7) µmol/L to (20.6 ± 8.3) µmol/L (P < 0.01). However, the level was still lower than the average level of healthy children [(27.1 ± 4.5) µmol/L, P < 0.01]. CONCLUSION: Seventeen patients were diagnosed with PCD by the test levels of free carnitine and acylcarnitines in blood with tandem mass spectrometry, and gene mutation test. Large dose of carnitine had a good effect in treatment of the PCD patients.

Lipid storage myopathy.

Lipid storage myopathy (LSM) is pathologically characterized by prominent lipid accumulation in muscle fibers due to lipid dysmetabolism. Although extensive molecular studies have been performed, there are only four types of genetically diagnosable LSMs: primary carnitine deficiency (PCD), multiple acyl-coenzyme A dehydrogenase deficiency (MADD), neutral lipid storage disease with ichthyosis, and neutral lipid storage disease with myopathy. Making an accurate diagnosis, by specific laboratory tests including genetic analyses, is important for LSM as some of the patients are treatable: individuals with PCD show dramatic improvement with high-dose oral L-carnitine supplementation and increasing evidence indicates that MADD due to ETFDH mutations is riboflavin responsive.

Substrate discrimination by ergothioneine transporter SLC22A4 and carnitine transporter SLC22A5: gain-of-function by interchange of selected amino acids.

ETT (originally designated as OCTN1; human gene symbol SLC22A4) and CTT (OCTN2; SLC22A5) are highly specific transporters of ergothioneine and carnitine, respectively. Despite a high degree of sequence homology, both carriers discriminate precisely between substrates: ETT does not transport carnitine, and CTT does not transport ergothioneine. Our aim was to turn ETT into a transporter for carnitine and CTT into a transporter for ergothioneine by a limited number of point mutations. From a multiple alignment of several mammalian amino acid sequences, those positions were selected for conversion that were momentously different between ETT and CTT from human but conserved among all orthologues. Mutants were expressed in 293 cells and assayed for transport of ergothioneine and carnitine. Several ETT mutants clearly catalyzed transport of carnitine, up to 35% relative to wild-type CTT. Amazingly, complementary substitutions in CTT did not provoke transport activity for ergothioneine. In similar contrast, carnitine transport by CTT mutants was abolished by very few substitutions, whereas ergothioneine transport by ETT mutants was maintained even with the construct most active in carnitine transport. To explain these results, we propose that ETT and CTT use dissimilar pathways for conformational change, in addition to incongruent substrate binding sites. In other words, carnitine is excluded from ETT by binding, and ergothioneine is excluded from CTT by turnover movement. Our data indicate amino acids critical for substrate discrimination not only in transmembrane segments 5, 7, 8, and 10, but also in segments 9 and 12 which were hitherto considered as unimportant.

Identification and characterization of an ATP binding cassette L-carnitine transporter in Listeria monocytogenes.

We identified an operon in Listeria monocytogenes EGD with high levels of sequence similarity to the operons encoding the OpuC and OpuB compatible solute transporters from Bacillus subtilis, which are members of the ATP binding cassette (ABC) substrate binding protein-dependent transporter superfamily. The operon, designated opuC, consists of four genes which are predicted to encode an ATP binding protein (OpuCA), an extracellular substrate binding protein (OpuCC), and two membrane-associated proteins presumed to form the permease (OpuCB and OpuCD). The operon is preceded by a potential SigB-dependent promoter. An opuC-defective mutant was generated by the insertional inactivation of the opuCA gene. The mutant was impaired for growth at high osmolarity in brain heart infusion broth and failed to grow in a defined medium. Supplementation of the defined medium with peptone restored the growth of the mutant in this medium. The mutant was found to accumulate the compatible solutes glycine betaine and choline to same extent as the parent strain but was defective in the uptake of L-carnitine. We conclude that the opuC operon in L. monocytogenes encodes an ABC compatible solute transporter which is capable of transporting L-carnitine and which plays an important role in osmoregulation in this pathogen.