Development and validation of a gas chromatography–mass spectrometry method to analyze octanoate enrichments at low concentrations in human plasma

A new method for accurately analyzing octanoate enrichment in plasma was developed and validated. Samples were derivatized directly in plasma by transesterification with isobutanol and were analyzed by gas chromatography–mass spectrometry (GC-MS). This method was developed to analyze the precursor enrichment in a stable isotope tracer protocol. Glyceryl tri[1,2,3,4- 13C 4] octanoate, a stable isotope-labeled medium-chain triglyceride (MCT), was orally administered in combination with (1) exclusively MCT or (2) a combination of protein, carbohydrates, and MCT to investigate the metabolic route of oral MCT under various conditions. Accurate analysis of octanoate enrichment in plasma at concentrations as low as 0.43 μM (lower limit of quantification, LLOQ) was performed. This is an improvement of about twenty times for the LLOQ for analysis of the enrichment of octanoate when compared with the gold-standard method for fatty acid analysis (methyl esterification). Moreover, we found that‚ with this gold-standard method, study samples were easily contaminated with (unlabeled) octanoate from other sources, leading to biased, incorrect results. The precision and linearity obtained using the new method were good (coefficient of variation intraday 0.99). The sensitivity was sufficient for analyzing samples obtained using the stable isotope protocol. This new method is more sensitive than methyl esterification and it minimizes the risk of contamination. [Figure not available: see fulltext.

Prediction of phenotypic severity in mucopolysaccharidosis type IIIA

Mucopolysaccharidosis IIIA or Sanfilippo disease type A is a progressive neurodegenerative disorder presenting in early childhood, caused by an inherited deficiency of the lysosomal hydrolase sulfamidase. New missense mutations, for which genotype-phenotype correlations are currently unknown, are frequently reported, hampering early prediction of phenotypic severity and efficacy assessment of new disease-modifying treatments. We aimed to design a method to determine phenotypic severity early in the disease course. Fifty-three patients were included for whom skin fibroblasts and data on disease course and mutation analysis were available. Patients were phenotypically characterized on clinical data as rapidly progressing or slowly progressing. Sulfamidase activity was measured in fibroblasts cultured at 37 °C and at 30 °C. Sulfamidase activity in fibroblasts from patients homozygous or compound heterozygous for a combination of known severe mutations remained below the limit of quantification under both culture conditions. In contrast, sulfamidase activity in fibroblasts from patients homozygous or compound heterozygous for a known mild mutation increased above the limit of quantification when cultured at 30 °C. With division on the basis of the patients' phenotype, fibroblasts from slowly progressing patients could be separated from rapidly progressing patients by increase in sulfamidase activity when cultured at 30 °C (p  < 0.001, sensitivity = 96%, specificity = 93%). Phenotypic severity strongly correlates with the potential to increase sulfamidase activity in fibroblasts cultured at 30 °C, allowing reliable distinction between patients with rapidly progressing or slowly progressing phenotypes. This method may provide an essential tool for assessment of treatment effects and for health care and life planning decisions. Ann Neurol 2017;82:686-69

Zorgpad VLCAD deficientie voor behandelaren

Voor u hebt u het zorgpad voor VLCAD-deficiëntie. Dit zorgpad is bedoeld voor meerdere gebruikers: Voor de patiënt: Verduidelijking van het ziekte- en zorgproces. Ondersteuning in het contact met zorgverzekeraars en hulpverleners. Voor de arts: Ondersteuning van de behandeling door expert opinions en/of wetenschappelijk onderzoek. Eenduidig verzamelen van informatie over ziektebeloop, complicaties en behandelingen. Betere afspraken binnen de beroepsgroep over de benodigdheden voor optimale zorg. Voor de zorgverzekeraar: Professionalisering van het zorgproces door consensus tussen behandelaren. Het zorgpad is ontwikkeld door een team van artsen die gespecialiseerd zijn in metabole ziekten, in samenwerking met andere deskundigen op het gebied van VLCAD-deficiëntie (VLCADD) en de patiëntenvereniging. Het geeft de consensus weer die is bereikt tussen de kinderartsen metabole ziekten en de internisten metabole ziekten. In dit zorgpad wordt de beste medische zorg zoveel mogelijk gebaseerd op de meest recente gegevens uit wetenschappelijk onderzoek, in combinatie met de ervaringen van een groep experts. Voor de gegeven adviezen is waar mogelijk een ‘level of evidence’ aangegeven. De levels variëren van niveau 1, het hoogste level, tot niveau 4. Het zorgtraject wordt weergegeven in een stroomschema. Hierna wordt de begeleiding voor kinderen en voor volwassenen beschreven. Het is belangrijk te realiseren dat dit een algemene richtlijn is: er kunnen goede redenen zijn om hier bij individuele patiënten van af te wijken. Ook kunnen er tussen de Nederlandse Universitair Medische Centra (UMC’s) met een afdeling voor Metabole Ziekten kleine verschillen bestaan over de precieze invulling of toepassing van dit zorgpad

Zorgpad LCHADD en MTP deficientie

Voor u hebt u het zorgpad voor LCHAD- en MTP-deficiëntie. Dit zorgpad is bedoeld voor meerdere gebruikers: Voor de patiënt: Verduidelijking van het ziekte- en zorgproces. Ondersteuning in het contact met zorgverzekeraars en hulpverleners. Voor de arts: Ondersteuning van de behandeling door expert opinions en/of wetenschappelijk onderzoek. Eenduidig verzamelen van informatie over ziektebeloop, complicaties en behandelingen. Betere afspraken binnen de beroepsgroep over de benodigdheden voor optimale zorg. Voor de zorgverzekeraar: Professionalisering van het zorgproces door consensus tussen behandelaren. Het zorgpad is ontwikkeld door een team van artsen die gespecialiseerd zijn in metabole ziekten, in samenwerking met de andere deskundigen op het gebied van LCHAD- en MTP-deficiëntie (LCHADD/MTPD) en de patiëntenvereniging. Het geeft de consensus weer die is bereikt tussen de kinderartsen metabole ziekten en de internisten metabole ziekten. In dit zorgpad wordt de beste medische zorg zoveel mogelijk gebaseerd op de meest recente gegevens uit wetenschappelijk onderzoek, in combinatie met de ervaringen van een groep experts. Voor de gegeven adviezen is waar mogelijk een ‘level of evidence’ aangegeven. De levels variëren van niveau 1, het hoogste level, tot niveau 4. Het zorgtraject wordt weergegeven in een stroomschema. Hierna wordt de begeleiding voor kinderen en voor volwassenen beschreven. Het is belangrijk te realiseren dat dit een algemene richtlijn is: er kunnen goede redenen zijn om hier bij individuele patiënten van af te wijken. Ook kunnen er tussen de Nederlandse Universitair Medische Centra (UMC’s) met een afdeling voor Metabole Ziekten kleine verschillen bestaan over de precieze invulling of toepassing van dit zorgpad

Disorders of mitochondrial long-chain fatty acid oxidation and the carnitine shuttle

Mitochondrial fatty acid oxidation is an essential pathway for energy production, especially during prolonged fasting and sub-maximal exercise. Long-chain fatty acids are the most abundant fatty acids in the human diet and in body stores, and more than 15 enzymes are involved in long-chain fatty acid oxidation. Pathogenic mutations in genes encoding these enzymes result in a long-chain fatty acid oxidation disorder in which the energy homeostasis is compromised and long-chain acylcarnitines accumulate. Symptoms arise or exacerbate during catabolic situations, such as fasting, illness and (endurance) exercise. The clinical spectrum is very heterogeneous, ranging from hypoketotic hypoglycemia, liver dysfunction, rhabdomyolysis, cardiomyopathy and early demise. With the introduction of several of the long-chain fatty acid oxidation disorders (lcFAOD) in newborn screening panels, also asymptomatic individuals with a lcFAOD are identified. However, despite early diagnosis and dietary therapy, a significant number of patients still develop symptoms emphasizing the need for individualized treatment strategies. This review aims to function as a comprehensive reference for clinical and laboratory findings for clinicians who are confronted with pediatric and adult patients with a possible diagnosis of a lcFAOD

Subclinical effects of long-chain fatty acid β-oxidation deficiency on the adult heart: A case-control magnetic resonance study

Cardiomyopathy can be a severe complication in patients with long-chain fatty acid β-oxidation disorders (LCFAOD), particularly during episodes of metabolic derangement. It is unknown whether latent cardiac abnormalities exist in adult patients. To investigate cardiac involvement in LCFAOD, we used proton magnetic resonance imaging (MRI) and spectroscopy (1H-MRS) to quantify heart function, myocardial tissue characteristics, and myocardial lipid content in 14 adult patients (two with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD); four with carnitine palmitoyltransferase II deficiency (CPT2D); and eight with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD)) and 14 gender-, age-, and BMI-matched control subjects. Examinations included cine MRI, MR tagging, native myocardial T1 and T2 mapping, and localized 1H-MRS at 3 Tesla. Left ventricular (LV) myocardial mass (P =.011) and the LV myocardial mass-to-volume ratio (P =.008) were higher in patients, while ejection fraction (EF) was normal (P =.397). LV torsion was higher in patients (P =.026), whereas circumferential shortening was similar compared with controls (P =.875). LV hypertrophy was accompanied by high myocardial T1 values (indicative of diffuse fibrosis) in two patients, and additionally a low EF in one case. Myocardial lipid content was similar in patients and controls. We identified subclinical morphological and functional differences between the hearts of LCFAOD patients and matched control subjects using state-of-the-art MR methods. Our results suggest a chronic cardiac disease phenotype and hypertrophic LV remodeling of the heart in LCFAOD, potentially triggered by a mild, but chronic, energy deficiency, rather than by lipotoxic effects of accumulating lipid metabolites

Prediction of VLCAD deficiency phenotype by a metabolic fingerprint in newborn screening bloodspots.

Purpose: Newborns who test positive for very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) in newborn screening may have a severe phenotype with early onset of life-threatening symptoms but may also have an attenuated phenotype and never become symptomatic. The objective of this study is to investigate whether metabolomic profiles in dried bloodspots (DBS) of newborns allow early phenotypic prediction, permitting tailored treatment and follow-up. Methods: A metabolic fingerprint was generated by direct infusion high resolution mass spectrometry in DBS of VLCADD patients (n = 15) and matched controls. Multivariate analysis of the metabolomic profiles was applied to differentiate subgroups. Results: Concentration of six acylcarnitine species differed significantly between patients and controls. The concentration of C18:2- and C20:0-carnitine, 13,14-dihydroretinol and deoxycytidine monophosphate allowed separation between mild and severe patients. Two patients who could not be prognosticated on early clinical symptoms, were correctly fitted for severity in the score plot based on the untargeted metabolomics. Conclusion: Distinctive metabolomic profiles in DBS of newborns with VLCADD may allow phenotypic prognostication. The full potential of this approach as well as the underlying biochemical mechanisms need further investigation

Electrophysiological Abnormalities in VLCAD Deficient hiPSC-Cardiomyocytes Do not Improve with Carnitine Supplementation

Patients with a deficiency in very long-chain acyl-CoA dehydrogenase (VLCAD), an enzyme that is involved in the mitochondrial beta-oxidation of long-chain fatty acids, are at risk for developing cardiac arrhythmias. In human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), VLCAD deficiency (VLCADD) results in a series of abnormalities, including: 1) accumulation of long-chain acylcarnitines, 2) action potential shortening, 3) higher systolic and diastolic intracellular Ca2+ concentrations, and 4) development of delayed afterdepolarizations. In the fatty acid oxidation process, carnitine is required for bidirectional transport of acyl groups across the mitochondrial membrane. Supplementation has been suggested as potential therapeutic approach in VLCADD, but its benefits are debated. Here, we studied the effects of carnitine supplementation on the long-chain acylcarnitine levels and performed electrophysiological analyses in VLCADD patient-derived hiPSC-CMs with a ACADVL gene mutation (p.Val283Ala/p.Glu381del). Under standard culture conditions, VLCADD hiPSC-CMs showed high concentrations of long-chain acylcarnitines, short action potentials, and high delayed afterdepolarizations occurrence. Incubation of the hiPSC-CMs with 400 µM L-carnitine for 48 h led to increased long-chain acylcarnitine levels both in medium and cells. In addition, carnitine supplementation neither restored abnormal action potential parameters nor the increased occurrence of delayed afterdepolarizations in VLCADD hiPSC-CMs. We conclude that long-chain acylcarnitine accumulation and electrophysiological abnormalities in VLCADD hiPSC-CMs are not normalized by carnitine supplementation, indicating that this treatment is unlikely to be beneficial against cardiac arrhythmias in VLCADD patients

Exploring the metabolic fate of medium-chain triglycerides in healthy individuals using a stable isotope tracer

Background & aims: Medium chain triglyceride (MCT) supplementation is often recommended as treatment for patients with long-chain fatty acid β-oxidation (lcFAO) disorders, since they can be utilized as an energy source without the use of the defective enzyme. However, studies in mice and preterm infants suggest that not all medium-chain fatty acids (MCFA) are oxidized and may undergo elongation to long-chain fatty acids (LCFA). In this single blinded study, we explored the metabolic fates of MCT in healthy individuals using a 13C-labeled MCT tracer. Method: Three healthy males in rest received on two test days a primed continuous infusion of glyceryl tri[1,2,3,4–13C4]-octanoate with either an isocaloric supplementation of 1) exclusively MCT (MCT-only) or 2) a mixture of MCT, proteins and carbohydrates (MCT-mix). Gas chromatography - combustion - isotope ratio mass spectrometry (GC-C-IRMS) was used to determine 13C-enrichment of long-chain fatty acids in plasma and of 13CO2 in exhaled air. Results: When provided as single energy source, an estimated 42% of administered MCT was converted to CO2. In combination with carbohydrates and proteins in the diet, oxidation of MCT was higher (62%). In both diets <1% of 13C-label was incorporated in LCFA in plasma, indicating that administered MCT underwent chain-elongation to LCT. Conclusions: Although the relative MCT oxidation rate was higher when combined with carbohydrates and protein, quantitatively more MCT was oxidized when given an isocaloric meal with solely MCT. As these results were obtained in the resting state opposed to during exercise, it is too early to give a recommendation concerning the use of MCT in lcFAO disorders. The data show that in resting healthy individuals only a very small part of the MCT is traced back as LCFA in plasma, suggesting that MCT treatment does not result in a large LCFA burden, however further research on storage of MCT in tissues is warranted. Registration: The study was registered in the Nederlands Trialregister. Protocol ID: Trial NL7417 (NTR7650)