Journal of Inherited Metabolic Disease最新文献

Background: Phenylketonuria (PKU) is caused by phenylalanine hydroxylase deficiency. Treatment is primarily a low-Phe diet combined with l-amino acid-based products (l-AA). Protein requirements in adults with PKU have not been directly determined. A formula with glycomacropeptide (GMP) and low phenylalanine is available, yet untested for optimal protein synthesis.

Objectives: To determine the protein requirements in adults with PKU and the bioavailability of GMP-AA in the same patients using the indicator amino acid oxidation (IAAO) technique.

Methods: Each participant was allocated to 7 separate l-AA intakes (range: 0.1-1.8 g/kg/day) in Experiment 1. In Experiment 2, the same patients participated in 4 GMP-AA intakes (range: 0.1-0.9 g/kg/day). The IAAO method with l-[1-¹³C]-lysine as the indicator amino acid and its oxidation to ¹³CO₂ was used as the primary indicator of protein synthesis. Protein requirements were identified with a breakpoint, and bioavailability was determined by comparing ¹³CO₂ slope from GMP-AA versus l-AA.

Results: Six adults with PKU (4 M: 2F) completed a total of 54 study days over the 2 experiments. The estimated average requirement (EAR) for protein was determined to be 1.11 g/kg/day (R² = 0.20). The bioavailability of protein from GMP-AA was determined to be 99.98%, which was high and near to 100% comparable to l-AA; although, the results apply only to the tested GMP-AA blend.

Conclusions: To our knowledge, this is the first study to directly define a quantitative protein requirement and indicates that current PKU protein recommendations for adults with PKU may be underestimated. The bioavailability of protein in the GMP-AA blend was high and optimal for protein synthesis in adults with PKU.

This study describes the neurodevelopmental outcome of children with urea cycle disorders (UCD) and organic acidemias (OA) preliver transplant (LT), 1-year, and 3-years post-LT. We performed a retrospective chart review of children with OA or UCD transplanted between January 2014 and December 2021. Standardized motor and cognitive assessment scores were collected from children who had ≥1 motor/cognitive assessment at any timepoint. Pre-LT brain magnetic resonance imaging (MRI) was graded. Associations between demographic/medical variables and neurodevelopmental outcomes were explored. Twenty-six children (64% male) underwent LT at a median age of 1.4 (interquartile range 0.71, 3.84) years. Fifteen (58%) had a UCD diagnosis, 14 (54%) required dialysis for hyperammonemia, and 10 (42%) had seizures typically around diagnosis. The proportion of children with gross motor scores >1 standard deviation (SD) below the mean increased across timepoints, and ≥50% demonstrated general intellect scores >2 SD below the mean at each timepoint. The following significant associations were noted: UCD diagnoses with lower general intellect scores (p = 0.019); arginosuccinate lyase deficiency diagnosis with lower visual motor scores at 3-years post-LT (p = 0.035); a history of seizures pre-LT with lower general intellect (>2SD below the mean) at 3-years post-LT (p = 0.020); dialysis pre-LT with lower motor scores (>1 SD below the mean) at 1-year post-LT (p = 0.039); pre-emptive LT with higher general intellect scores at 3-years post-LT (p = 0.001). MRI gradings were not associated with developmental scores. In our single centre study, children with UCD or OA had a higher prevalence of developmental impairment post-LT compared to population norms. Earlier screening, pre-emptive transplant, and rehabilitation may optimize long-term outcomes.

Mitochondria are dynamic cellular organelles with complex roles in metabolism and signalling. Primary mitochondrial disorders are a group of approximately 400 monogenic disorders arising from pathogenic genetic variants impacting mitochondrial structure, ultrastructure and/or function. Amongst these disorders, defects of complex lipid biosynthesis, especially of the unique mitochondrial membrane lipid cardiolipin, and membrane biology are an emerging group characterised by clinical heterogeneity, but with recurrent features including cardiomyopathy, encephalopathy, neurodegeneration, neuropathy and 3-methylglutaconic aciduria. This review discusses lipid synthesis in the mitochondrial membrane, the mitochondrial contact site and cristae organising system (MICOS), mitochondrial dynamics and trafficking, and the disorders associated with defects of each of these processes. We highlight overlapping functions of proteins involved in lipid biosynthesis and protein import into the mitochondria, pointing to an overarching coordination and synchronisation of mitochondrial functions. This review also focuses on membrane interactions between mitochondria and other organelles, namely the endoplasmic reticulum, peroxisomes, lysosomes and lipid droplets. We signpost disorders of these membrane interactions that may explain the observation of secondary mitochondrial dysfunction in heterogeneous pathological processes. Disruption of these organellar interactions ultimately impairs cellular homeostasis and organismal health, highlighting the central role of mitochondria in human health and disease.

Patients with fatty acid oxidation disorders (FAODs) experience muscle symptoms due to impaired ATP metabolism and the toxicity of accumulated mitochondrial FAO substrates or intermediates, especially during catabolic states. A major issue is the absence of specific and sensible biomarkers to evaluate metabolic equilibrium. The relationship between cardiac output (Q) and oxygen consumption (VO₂) during incremental exercise (dQ/dVO₂) provides an indirect surrogate of mitochondrial function. A high dQ/dVO₂ slope indicates impaired oxidative phosphorylation in skeletal muscle during exercise. Our study aimed to evaluate dQ/dVO₂ as a potential marker of the severity of FAODs. We retrospectively collected clinical, laboratory parameters and treatment data for FAOD patients over 6 years old, including a disease severity score, plasma acylcarnitines and cardiopulmonary exercise tests with Q measurement via thoracic bioelectrical impedance. FAO flux was measured in whole blood and in myoblasts when available. We included 27 FAOD patients followed from 2015 to 2022, with deficiencies in LCHAD (n = 10), CPT2 (n = 6), VLCAD (n = 7), or MADD (n = 4). CPT2 deficient patients with severe scores had the highest C18:1-, C16-, C18-acylcarnitines, and dQ/dVO₂. In these patients, dQ/dVO₂ was positively correlated with C18:1, C16, and C18 acylcarnitines. In a linear multivariate regression model, dQ/dVO₂ was significantly associated with the severity score (B = 0.831, p = 0.008) and triheptanoin treatment (B = -0.547, p = 0.025). dQ/dVO₂ and plasma long-chain acylcarnitines might be useful to monitor CPT2D, as these parameters associate with our clinical severity score and could reflect altered mitochondrial functions.

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder leading to deleterious brain effects. While animal models suggested that MPS I severely affects white matter (WM), whole-brain diffusion tensor imaging (DTI) analysis was not performed due to MPS-related morphological abnormalities. 3T DTI data from 28 severe (MPS IH, treated with hematopoietic stem cell transplantation-HSCT), 16 attenuated MPS I patients (MPS IA) enrolled under the study protocol NCT01870375, and 27 healthy controls (HC) were analyzed using the free-water correction (FWC) method to resolve macrostructural partial volume effects and unravel differences in DTI metrics accounting for microstructural abnormalities. FWC analysis in MPS IH compared to HC revealed higher free-water fraction (FWF) in all WM regions with increased radial (RD) and mean diffusivity (MD). Higher RD, MD, and FWF in cingulate and FWF in temporal WM were observed in MPS IA relative to HC. FWF and RD in the corpus callosum (CC) were higher in MPS IH than in MPS IA. Reaction time was correlated with fractional anisotropy (FA) in frontal and parietal WM in MPS IH. FA in temporal and central WM correlated with d-prime in MPS IA. The HSCT age was related to FA in parietal WM and FWF in frontal WM in MPS IH. FWC delineated subtype-specific WM microstructural abnormalities linked to myelination that were more extensive in MPS IH than IA, with CC findings being a key differentiator between subtypes. Earlier age at HSCT was related to preserved WM microstructure in the brain of MPS IH patients. Free water-corrected DTI distinguishes severe and attenuated MPS I patients and reveals a relationship between attention, age at HSCT, and white matter microstructure.

Cobalamin C (Cbl-C) defect causes methylmalonic acidemia, homocystinuria, intellectual disability and visual impairment, despite treatment adherence. While international guidelines recommend parenteral hydroxocobalamin (OH-Cbl) as effective treatment, dose adjustments remain unclear. We assessed OH-Cbl therapy impact on biochemical, neurocognitive and visual outcomes in early-onset Cbl-C patients treated with different OH-Cbl doses over 3 years. Group A (n = 5), diagnosed via newborn screening (NBS), received high-dose OH-Cbl (median 0.55 mg/kg/day); Group B1 (n = 3), NBS-diagnosed, received low-dose OH-Cbl (median 0.09 mg/kg/day); Group B2 (n = 12), diagnosed on clinical bases, received low-dose OH-Cbl (median 0.06 mg/kg/day). Biochemical analyses revealed better values of homocysteine, methionine and methylmalonic acid in Group A compared to Group B1 (p < 0.01, p < 0.05 and p < 0.01, respectively) and B2 (p < 0.001, p < 0.01 and p < 0.001, respectively). Neurodevelopmental assessment showed better outcome in Group A compared to low-dose treated Groups B1 and B2, especially in Developmental Quotient, Hearing and Speech and Performance subscales without significant differences between Group B2 and Group B1. Maculopathy was detected in 100%, 66% and 83% of patients in the three groups, respectively. This study showed that "high-dose" OH-Cbl treatment in NBS-diagnosed children with severe early-onset Cbl-C defect led to a significant improvement in the metabolic profile and in neurocognitive outcome, compared to age-matched patients treated with a "low-dose" regimen. Effects on maculopathy seem unaffected by OH-Cbl dosage. Our findings, although observed in a limited number of patients, may contribute to improve the long-term outcome of Cbl-C patients.

Glyoxylate is a toxic metabolite because of its rapid conversion into oxalate, as catalyzed by the ubiquitous enzyme lactate dehydrogenase. This requires the presence of efficient glyoxylate detoxification systems in multiple subcellular compartments, as glyoxylate is produced in peroxisomes, mitochondria, and the cytosol. Alanine glyoxylate aminotransferase (AGT) and glyoxylate reductase/hydroxypyruvate reductase (GRHPR) are the key enzymes involved in glyoxylate detoxification. Bi-allelic mutations in the genes coding for these enzymes cause primary hyperoxaluria type 1 (PH1) and 2 (PH2), respectively. Glyoxylate is derived from various sources, including 4-hydroxyproline, which is degraded in mitochondria, generating pyruvate and glyoxylate, as catalyzed by the mitochondrial enzyme 4-hydroxy-2-oxoglutarate aldolase (HOGA); however, counterintuitively, a defect in HOGA1 is the molecular basis of primary hyperoxaluria type 3 (PH3). Irrespective of its underlying cause, hyperoxaluria in humans leads to nephrocalcinosis, recurrent urolithiasis, and kidney damage, which may culminate in kidney failure requiring combined liver-kidney transplantation in severely affected patients. In the past few years, therapeutic options, especially for primary hyperoxaluria type 1 (PH1), have greatly been improved thanks to the introduction of two RNAi-based therapies that inhibit either the production of glycolate oxidase (lumasiran) or lactate dehydrogenase (nedosiran). While lumasiran only targets PH1 patients, nedosiran was specifically developed to target all three subtypes of PH. Inspired by the findings reported in the literature that nedosiran effectively reduced urinary oxalate excretion in PH1 patients but not in PH2 or PH3 patients, we have now revisited glyoxylate metabolism in humans and performed a thorough literature study which revealed that glyoxylate/oxalate metabolism is not confined to the liver but instead involves multiple different organs. This new view on glyoxylate/oxalate metabolism in humans may well explain the disappointing results of nedosiran in PH2 and PH3, and provides new clues for the future generation of new therapeutic strategies for PH2 and PH3.

Pegunigalsidase alfa, a PEGylated α-galactosidase A enzyme replacement therapy (ERT) for Fabry disease, has a longer plasma half-life than other ERTs administered intravenously every 2 weeks (E2W). BRIGHT (NCT03180840) was a phase III, open-label study in adults with Fabry disease, previously treated with agalsidase alfa or beta E2W for ≥3 years, who switched to 2 mg/kg pegunigalsidase alfa every 4 weeks (E4W) for 52 weeks. Primary objective assessed safety, including number of treatment-emergent adverse events (TEAEs). Thirty patients were enrolled (24 males); 23 previously received agalsidase beta. Pegunigalsidase alfa plasma concentrations remained above the lower limit of quantification throughout the 4-week dosing interval. Thirty-three of 182 TEAEs (in 9 patients) were considered treatment-related; all were mild/moderate. No patients developed de novo anti-drug antibodies (ADAs). In the efficacy analysis (n = 29), median (inter-quartile range) eGFR change from baseline over 52 weeks was -1.9 (-5.9; 1.8) mL/min/1.73 m² (n = 28; males [n = 22]: -2.4 [-5.2; 3.2]; females [n = 6]: -0.7 [-9.2; 2.0]). Overall, median eGFR slope was -1.9 (-8.3; 1.9) mL/min/1.73 m²/year (ADA-negative [n = 20]: -1.2 [-6.4; 2.6]; ADA-positive [n = 9]: -8.4 [-11.6; -1.0]). Lyso-Gb3 concentrations were low and stable in females, with a slight increase in males (9/24 ADA-positive). The BRIGHT study results suggest that 2 mg/kg pegunigalsidase alfa E4W is tolerated well in stable adult patients with Fabry disease. Due to the low number of patients in this study, more research is needed to demonstrate the effects of pegunigalsidase alfa given E4W. Further evidence, outside of this clinical trial, should be factored in for physicians to prolong the biweekly ERT intervals to E4W. TAKE-HOME MESSAGE: Treatment with 2 mg/kg pegunigalsidase alfa every 4 weeks could offer a new treatment option for patients with Fabry disease.

Mucopolysaccharidosis II (MPS II, Hunter syndrome) is a rare, X-linked lysosomal storage disease caused by reduced activity of iduronate-2-sulfatase (I2S), with subsequent cellular accumulation of the glycosaminoglycans (GAGs), heparan sulfate, and dermatan sulfate (DS). DS is a major component of the extracellular matrix of heart valves, which can be affected in MPS II. We investigated the natural history of valve disease in MPS II and the impact of long-term intravenous enzyme replacement therapy (ERT) with recombinant I2S (idursulfase). In total, 604 cardiac examinations were assessed from serial follow-up of 80 male patients (49 neuronopathic). Valve disease was classified according to standard practice from hemodynamic features evident from echocardiography. The natural history group comprised 48 patients (up to 14.8 years of follow-up; median, 2.6 years; 24 patients started ERT during the study); 56 patients were treated (up to 14.2 years of follow-up; median, 6.2 years). Lifetime GAG burden (calculated from urinary GAG measurements) correlated significantly with the degree of valve disease. Onset of moderate-to-severe valve disease was significantly delayed in treated (median age at onset, 29.1 ± 2 [95% CI: 25.2-32.9] years; Kaplan-Meier estimation) versus untreated patients (17.6 ± 1 [95% Cl: 15.8-19.4] years; p < 0.0001). Cox regression modeling found that long-term ERT reduced the probability of developing severe valve disease (χ², 32.736; significant after 5 years of ERT). Overall, this study found that valve disease severity in MPS II correlates with GAG burden and that progression is delayed by long-term ERT.

Phenylketonuria is a rare inherited disorder that disrupts the metabolism of phenylalanine (Phe) to tyrosine by phenylalanine hydroxylase (PAH). Sapropterin dihydrochloride (Kuvan®) is approved for use in Europe to reduce blood Phe levels and improve Phe tolerance in sapropterin-responsive individuals. KAMPER (NCT01016392) is an observational, multinational registry assessing long-term safety and efficacy of sapropterin. Five hundred and seventy-six participants with PAH deficiency were enrolled from nine European countries (69 sites; December 2009-May 2016). Participants were aged <4 years (n = 11), 4 to <12 years (n = 329), 12 to <18 years (n = 141), and ≥18 years (n = 95) at enrolment. Overall, 401 (69.6%) participants experienced a total of 1960 adverse events; 61 events in 42 participants were serious, and two were considered sapropterin-related by the investigator. Mean (standard deviation) actual dietary Phe intake increased from baseline across all age groups: 957 (799) mg/day to a maximum of 1959 (1121) mg/day over a total study period of 11 years. Most participants exhibited an increase in Phe tolerance while blood Phe levels remained in the target range for their age (120-360 μmol/L for <12 years; 120-600 μmol/L for ≥12 years). Most participants exhibited normal growth for height, weight, and body mass index. No additional safety concerns were identified. As an observational study, limitations include variability in routine care practices and inconsistent availability of data. Long-term sapropterin use demonstrates a favourable safety profile in real-world settings and increases Phe tolerance in participants with PAH deficiency while maintaining blood Phe levels in the target ranges.