Mitochondrial mosaics in the liver of 3 infants with mtDNA defects

<p>Abstract</p> <p>Background</p> <p>In muscle cytochrome oxidase (COX) negative fibers (mitochondrial mosaics) have often been visualized.</p> <p>Methods</p> <p>COX activity staining of liver for light and electron microscopy, muscle stains, blue native gel electrophoresis and activity assays of respiratory chain proteins, their immunolocalisation, mitochondrial and nuclear DNA analysis.</p> <p>Results</p> <p>Three unrelated infants showed a mitochondrial mosaic in the liver after staining for COX activity, i.e. hepatocytes with strongly reactive mitochondria were found adjacent to cells with many negative, or barely reactive, mitochondria. Deficiency was most severe in the patient diagnosed with Pearson syndrome. Ragged-red fibers were absent in muscle biopsies of all patients. Enzyme biochemistry was not diagnostic in muscle, fibroblasts and lymphocytes. Blue native gel electrophoresis of liver tissue, but not of muscle, demonstrated a decreased activity of complex IV; in both muscle and liver subcomplexes of complex V were seen. Immunocytochemistry of complex IV confirmed the mosaic pattern in two livers, but not in fibroblasts. MRI of the brain revealed severe white matter cavitation in the Pearson case, but only slight cortical atrophy in the Alpers-Huttenlocher patient, and a normal image in the 3rd. MtDNA in leucocytes showed a common deletion in 50% of the mtDNA molecules of the Pearson patient. In the patient diagnosed with Alpers-Huttenlocher syndrome, mtDNA was depleted for 60% in muscle. In the 3rd patient muscular and hepatic mtDNA was depleted for more than 70%. Mutations in the nuclear encoded gene of <it>POLG </it>were subsequently found in both the 2nd and 3rd patients.</p> <p>Conclusion</p> <p>Histoenzymatic COX staining of a liver biopsy is fast and yields crucial data about the pathogenesis; it indicates whether mtDNA should be assayed. Each time a mitochondrial disorder is suspected and muscle data are non-diagnostic, a liver biopsy should be recommended. Mosaics are probably more frequent than observed until now. A novel pathogenic mutation in <it>POLG </it>is reported.</p> <p>Tentative explanations for the mitochondrial mosaics are, in one patient, unequal partition of mutated mitochondria during mitoses, and in two others, an interaction between products of several genes required for mtDNA maintenance.</p

Undiagnosed Phenylketonuria Can Exist Everywhere: Results From an International Survey

peer reviewedMany countries do not have a newborn screening (NBS) program, and immigrants from such countries are at risk for late diagnosis of phenylketonuria (PKU). In this international survey, 52 of 259 patients (20%) with late diagnosed PKU were immigrants, and 145 of the 259 (55%) were born before NBS or in a location without NBS. © 2021 The Author

Long-term effects of medical management on growth and weight in individuals with urea cycle disorders

Low protein diet and sodium or glycerol phenylbutyrate, two pillars of recommended long-term therapy of individuals with urea cycle disorders (UCDs), involve the risk of iatrogenic growth failure. Limited evidence-based studies hamper our knowledge on the long-term effects of the proposed medical management in individuals with UCDs. We studied the impact of medical management on growth and weight development in 307 individuals longitudinally followed by the Urea Cycle Disorders Consortium (UCDC) and the European registry and network for Intoxication type Metabolic Diseases (E-IMD). Intrauterine growth of all investigated UCDs and postnatal linear growth of asymptomatic individuals remained unaffected. Symptomatic individuals were at risk of progressive growth retardation independent from the underlying disease and the degree of natural protein restriction. Growth impairment was determined by disease severity and associated with reduced or borderline plasma branched-chain amino acid (BCAA) concentrations. Liver transplantation appeared to have a beneficial effect on growth. Weight development remained unaffected both in asymptomatic and symptomatic individuals. Progressive growth impairment depends on disease severity and plasma BCAA concentrations, but cannot be predicted by the amount of natural protein intake alone. Future clinical trials are necessary to evaluate whether supplementation with BCAAs might improve growth in UCDs

Raising Awareness of False Positive Newborn Screening Results Arising from Pivalate-Containing Creams and Antibiotics in Europe When Screening for Isovaleric Acidaemia

peer reviewe

Neonatal thyroid-stimulating hormone concentrations in Belgium: a useful indicator for detecting mild iodine deficiency?

It has been proposed that neonatal thyroid-stimulating hormone (TSH) concentrations are a good indicator of iodine deficiency in the population. A frequency of neonatal TSH concentrations above 5 mU/L below 3% has been proposed as the threshold indicating iodine sufficiency. The objective of the present study was to evaluate feasibility and usefulness of nation-wide neonatal TSH concentration screening results to assess iodine status in Belgium. All newborns born in Belgium during the period 2009-2011 (n = 377713) were included in the study, except those suffering from congenital hypothyroidism and premature neonates. The frequency of neonatal TSH concentrations above 5 mU/L from 2009 to 2011 in Belgium fluctuated between 2.6 and 3.3% in the centres using the same TSH assay. There was a significant inverse association between neonatal TSH level and birth weight. The longer the duration between birth and screening, the lower the TSH level. Neonatal TSH levels were significantly lower in winter than in spring or autumn and significantly lower in spring and summer than in autumn while significantly higher in spring compared to summer. In conclusion, despite that pregnant women in Belgium are mildly iodine deficient, the frequency of neonatal TSH concentrations above 5 mU/L was very low, suggesting that the neonatal TSH threshold proposed for detecting iodine deficiency needs to be re-evaluated. Although neonatal TSH is useful to detect severe iodine deficiency, it should not be recommended presently for the evaluation of iodine status in mildly iodine deficient regions.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Dihydropyrimidinase deficiency: Phenotype, genotype and structural consequences in 17 patients

AbstractDihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine. To date, only 11 individuals have been reported suffering from a complete DHP deficiency. Here, we report on the clinical, biochemical and molecular findings of 17 newly identified DHP deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological and gastrointestinal abnormalities and markedly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. Analysis of DPYS, encoding DHP, showed nine missense mutations, two nonsense mutations, two deletions and one splice-site mutation. Seventy-one percent of the mutations were located at exons 5–8, representing 41% of the coding sequence. Heterologous expression of 11 mutant enzymes in Escherichia coli showed that all but two missense mutations yielded mutant DHP proteins without significant activity. Only DHP enzymes containing the mutations p.R302Q and p.T343A possessed a residual activity of 3.9% and 49%, respectively. The crystal structure of human DHP indicated that the point mutations p.R490C, p.R302Q and p.V364M affect the oligomerization of the enzyme. In contrast, p.M70T, p.D81G, p.L337P and p.T343A affect regions near the di-zinc centre and the substrate binding site. The p.S379R and p.L7V mutations were likely to cause structural destabilization and protein misfolding. Four mutations were identified in multiple unrelated DHP patients, indicating that DHP deficiency may be more common than anticipated

Efficacy, Safety And Population Pharmacokinetics Of Sapropterin In Pku Patients < 4 Years: Results From The Spark Open-Label, Multicentre, Randomized Phase Iiib Trial

Background: Sapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC 1.14.16.1), was initially approved in Europe only for patients >= 4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan r) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children = 1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7-42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using nonlinear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters. Conclusions: The addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children < 4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients < 4 years with BH4-responsive phenylketonuria.WoSScopu