Molybdenum cofactor deficiency: Identification of a patient with homozygote mutation in the MOCS3 gene.

We describe the clinical presentation and 17 years follow up of a boy, born to consanguineous parents and presenting with intellectual disability (ID), autism, "marfanoid" dysmorphic features, and moderate abnormalities of sulfite metabolism compatible with molybdenum cofactor deficiency, but normal sulfite oxidase activity in cultured skin fibroblasts. Genomic exome analysis revealed a homozygous MOCS3 missense mutation, leading to a p.Ala257Thr substitution in the highly conserved ubiquitin-like-domain of the protein. MOCS3 is the third protein, besides MOCS1 and MOCS2, involved in the biosynthesis of the molybdenum cofactor and has a dual ubiquitin-like function in tRNA thiolation. It is plausible that the phenotype results from deficiency of this dual function, not only from defective synthesis of molybdenum cofactor, which would explain similarities and differences from the MOCS1 and MOCS2-related disorders. This observation should encourage testing of additional ID patients with mild abnormalities of sulfite metabolism for MOCS3 mutations.

Rapid ultraperformance liquid chromatography-tandem mass spectrometry assay for a characteristic glycogen-derived tetrasaccharide in Pompe disease and other glycogen storage diseases.

BACKGROUND: Urinary excretion of the tetrasaccharide 6-α-D-glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). METHODS: Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS: We separated and quantified acarbose, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 µmol/L and the limit of quantification was 2.8 µmol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 µmol/L Glc4), and 10.5% and 16.2% (200 µmol/L Glc4). Glc4 in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M4 was present in 5% of urine samples. Mean Glc4 concentrations per age group in untreated patients with Pompe disease (GSD type II) (n = 66) were significantly higher, ranging from 39.4 to 10.3 mmol/mol creatinine (P < 0.001-0.005). The diagnostic sensitivity of Glc4 for GSD-II was 98.5% and the diagnostic specificity 92%. Urine Glc4 was also increased in GSD-III (8 of 9), GSD-IV (2 of 3) and GSD-IX (6 of 10) patients. CONCLUSIONS: The UPLC-MS/MS assay of Glc4 in urine was discriminative between Glc4 and M4 and confirmed the diagnosis in >98% of GSD-II cases.

Long-term follow-up and treatment in nine boys with X-linked creatine transporter defect.

The creatine transporter (CRTR) defect is a recently discovered cause of X-linked intellectual disability for which treatment options have been explored. Creatine monotherapy has not proved effective, and the effect of treatment with L-arginine is still controversial. Nine boys between 8 months and 10 years old with molecularly confirmed CRTR defect were followed with repeated (1)H-MRS and neuropsychological assessments during 4-6 years of combination treatment with creatine monohydrate, L-arginine, and glycine. Treatment did not lead to a significant increase in cerebral creatine content as observed with H(1)-MRS. After an initial improvement in locomotor and personal-social IQ subscales, no lasting clinical improvement was recorded. Additionally, we noticed an age-related decline in IQ subscales in boys affected with the CRTR defect.

Prenatal screening of sialic acid storage disease and confirmation in cultured fibroblasts by LC-MS/MS.

Sialic acid storage disease (SASD) is an inborn error resulting from defects in the lysosomal membrane protein sialin. The SASD phenotypical spectrum ranges from a severe presentation, infantile sialic acid storage disease (ISSD) which may present as hydrops fetalis, to a relatively mild form, Salla disease. Screening for SASD is performed by determination of free sialic acid (FSA) in urine or amniotic fluid supernatant (AFS). Subsequent diagnosis of SASD is performed by quantification of FSA in cultured fibroblasts and by mutation analysis of the sialin gene, SLC17A5. We describe simple quantitative procedures to determine FSA as well as conjugated sialic acid in AFS, and FSA in cultured fibroblasts, using isotope dilution ((13)C(3)-sialic acid) and multiple reaction monitoring LC-ESI-MS/MS. The whole procedure can be performed in 2-4 h. Reference values in AFS were 0-8.2 µmol/L for 15-25 weeks of gestation and 3.2-12.0 µmol/L for 26-38 weeks of gestation. In AFS samples from five fetuses affected with ISSD FSA was 23.9-58.9 µmol/L demonstrating that this method is able to discriminate ISSD pregnancies from normal ones. The method was also validated for determination of FSA in fibroblast homogenates. FSA in SASD fibroblasts (ISSD; 20-154 nmol/mg protein, intermediate SASD; 12.9-15.1 nmol/mg, Salla disease; 5.9-7.4 nmol/mg) was clearly elevated compared to normal controls (0.3-2.2 nmol/mg). In conclusion, we report simple quantitative procedures to determine FSA in AFS and cultured fibroblasts improving both prenatal diagnostic efficacy for ISSD as well as confirmatory testing in cultured fibroblasts following initial screening in urine or AFS.

Quantification of free and total sialic acid excretion by LC-MS/MS.

BACKGROUND: The main purpose for measuring urinary free sialic acid (FSA) is to diagnose sialic acid (SA) storage diseases. Elevated amounts of conjugated sialic acid (CSA) are observed in several diseases indicating the need to quantify CSA as well. A LC-MS/MS method for quantification of FSA and total sialic acid (TSA) in urine is developed and validated. METHODS: FSA is analyzed directly after filtration of urine samples. For determination of TSA an enzymatic (neuraminidase) and a chemical (acid) hydrolysis were compared. 13C3-sialic acid was used as internal standard. LC-MS/MS was performed in negative electrospray ionisation mode with multiple reaction monitoring of transitions m/z 308.2-->87.0 (SA) and m/z 311.2-->90.0 (13C3-SA). CSA was calculated by subtracting FSA from TSA. RESULTS: Limit of detection for FSA and TSA was 0.3 and 1.7 micromol/L, respectively. Limit of quantification for FSA and TSA was 1.0 and 5.0 micromol/L. Intra- and inter-assay variations of FSA were 4.6% and 6.6% (n=10) for FSA and 6.5% and 3.6% (n=10) for TSA. Linearity was tested till 7800 micromol/L (r2=0.9998). Values of SA analyzed after neuraminidase- or acid hydrolysis treatment were comparable. Urine samples from patients with inborn errors of SA (related) metabolism were analyzed and compared with age-related reference values. CONCLUSION: A method has been developed for routine determination of urinary FSA and TSA. The method is rapid, specific, robust and sensitive. Age-related reference values for FSA, TSA and CSA were determined and improved diagnostic efficacy.

Oral versus intravenous administration of lysine: equal effectiveness in reduction of renal uptake of [111In-DTPA]octreotide.

UNLABELLED: During tumor therapy with radiolabeled somatostatin analogs, the kidneys are dose limiting. Renal uptake in patients can effectively be reduced by a 4- to 10-h intravenous infusion of a lysine/arginine solution, thereby increasing the maximum radiation dose to the tumor without renal side effects. Oral administration of amino acids could facilitate this labor-intensive procedure. Therefore, the effects of oral versus intravenous administration of D-lysine were compared in rats injected with [111In-diethylenetriaminepentaacetic acid (DTPA)]octreotide. METHODS: Rats were intravenously injected with 3 MBq/0.5 microg [111In-DTPA]octreotide and also received D-lysine intravenously or orally in various concentrations and following various time schedules. Twenty-four hours after injection, a biodistribution study and renal ex vivo autoradiography were performed. RESULTS: Renal uptake was reduced significantly-up to 40%-in all lysine-treated groups, without affecting the uptake in other organs. CONCLUSION: Renal uptake of this radiolabeled peptide can be reduced up to 40% both by oral and by intravenous administration of lysine in rats.

The live-birth prevalence of mucopolysaccharidoses in Estonia.

Previous studies on the prevalence of mucopolysaccharidoses (MPS) in different populations have shown considerable variations. There are, however, few data with regard to the prevalence of MPSs in Fenno-Ugric populations or in north-eastern Europe, except for a report about Scandinavian countries. A retrospective epidemiological study of MPSs in Estonia was undertaken, and live-birth prevalence of MPS patients born between 1985 and 2006 was estimated. The live-birth prevalence for all MPS subtypes was found to be 4.05 per 100,000 live births, which is consistent with most other European studies. MPS II had the highest calculated incidence, with 2.16 per 100,000 live births (4.2 per 100,000 male live births), forming 53% of all diagnosed MPS cases, and was twice as high as in other studied European populations. The second most common subtype was MPS IIIA, with a live-birth prevalence of 1.62 in 100,000 live births. With 0.27 out of 100,000 live births, MPS VI had the third-highest live-birth prevalence. No cases of MPS I were diagnosed in Estonia, making the prevalence of MPS I in Estonia much lower than in other European populations. MPSs are the third most frequent inborn error of metabolism in Estonia after phenylketonuria and galactosemia.

High-dose cysteine administration does not increase synthesis of the antioxidant glutathione preterm infants.

OBJECTIVE: Our aim was to evaluate whether administration of additional cysteine is safe and stimulates glutathione synthesis in preterm infants in early life. METHODS: We conducted a prospective, randomized, clinical trial with infants with birth weights of <1500 g (N = 20). The infants were assigned randomly to receive either a standard dose (45 mg/kg per day) or a high dose (81 mg/kg per day) of cysteine. Intakes of other amino acids were similar, providing a total protein intake of 2.4 g/kg per day in both groups. We recorded base requirements in the first 6 days of life. On postnatal day 2, we conducted a stable isotope study to determine glutathione concentrations and synthesis rates in erythrocytes. RESULTS: Base requirements were higher in the high-dose cysteine group on days 3, 4, and 5. Despite an 80% increase in cysteine intake, plasma cystine concentrations did not increase. Glutathione concentrations and synthesis rates did not increase with additional cysteine administration. CONCLUSIONS: Administration of a high dose of cysteine (81 mg/kg per day) to preterm infants seems clinically safe but does not stimulate glutathione synthesis, compared with a lower dose (45 mg/kg per day). Further research is required to determine whether there is significant benefit associated with cysteine supplementation.

Prenatal diagnosis of citrullinemia and argininosuccinic aciduria: evidence for a transmission ratio distortion in citrullinemia.

BACKGROUND: In the course of 25 years, we have experienced a high rate of affected fetuses in the prenatal diagnosis of citrullinemia. METHODS AND RESULTS: Ninety-one pregnancies at 1 in 4 risk were tested; 36 were diagnosed as affected (39.5%; P = 0.0015). The high rate of positive diagnoses was found both after chorionic villus sampling (24/68 = 35.3%) and amniocentesis (12/23 = 52.2%) despite the completely different and independent techniques used. Using exactly the same (indirect) enzyme assay for argininosuccinic aciduria on chorionic villi and a similar method on amniotic fluid, the expected rate of affected fetuses was found: 13/53 = 24.5%. Technical and genetic causes for the unexpected results were excluded by confirmatory studies performed on independent fetal material, which was available for 27 of the 36 fetuses affected with citrullinemia. Biochemical confirmation was obtained in the 27 cases, whereas in 18 fetuses homozygosity or compound heterozygosity for disease-causing mutations were retrospectively demonstrated in the stored fetal cells. CONCLUSION: The results suggest the occurrence of preferential transmission of the mutant allele. An explanation for this phenomenon may be found in a protective role of argininosuccinic acid synthetase deficiency in mutant sperm cells against the possibly detrimental or apoptotic effect of nitric oxide produced normally from arginine by nitric oxide synthase.

Amino acid administration to premature infants directly after birth.

OBJECTIVES: To test the hypothesis that the administration of 2.4 g amino acids (AA)/(kg.d) to very low birth weight infants is safe and results in a positive nitrogen balance. STUDY DESIGN: We conducted a randomized, clinical trial. Preterm infants with birth weights <1500 g received either glucose and 2.4 g AA/(kg.d) from birth onward (n=66) or solely glucose during the first day with a stepwise increase in AA intake to 2.4 g AA/(kg.d) on day 3 (n=69). Blood gas analysis was performed daily during the first 6 postnatal days; blood urea nitrogen levels were determined on days 2, 4, and 6; AA plasma concentrations and nitrogen balances were determined on days 2 and 4. Student t tests, Mann-Whitney tests, and chi2 tests were performed to compare groups. RESULTS: Infants supplemented with AA had no major adverse side effects. Their blood urea nitrogen levels were higher, nitrogen balance turned positive upon AA administration, and more AA concentrations were within reference ranges. CONCLUSIONS: High-dose AA administration to very low birth weight infants can be introduced safely from birth onward and results in an anabolic state.

Glutamine supplementation of parenteral nutrition does not improve intestinal permeability, nitrogen balance, or outcome in newborns and infants undergoing digestive-tract surgery: results from a double-blind, randomized, controlled trial.

OBJECTIVE: To assess the effect of isocaloric isonitrogenous parenteral glutamine supplementation on intestinal permeability and nitrogen loss in newborns and infants after major digestive-tract surgery. SUMMARY BACKGROUND DATA: Glutamine supplementation in critically ill and surgical adults may normalize intestinal permeability, attenuate nitrogen loss, improve survival, and lower the incidence of nosocomial infections. Previous studies in critically ill children were limited to very-low-birthweight infants and had equivocal results. METHODS: Eighty newborns and infants were included in a double-blind, randomized trial comparing standard parenteral nutrition (sPN; n = 39) to glutamine-supplemented parenteral nutrition (GlnPN; glutamine target intake, 0.4 g kg day; n = 41), starting on day 2 after major digestive-tract surgery. Primary endpoints were intestinal permeability, as assessed by the urinary excretion ratio of lactulose and rhamnose (weeks 1 through 4); nitrogen balance (days 4 through 6), and urinary 3-methylhistidine excretion (day 5). Secondary endpoints were mortality, length of stay in the ICU and the hospital, number of septic episodes, and usage of antibiotics and ICU resources. RESULTS: Glutamine intake plateaued at 90% of the target on day 4. No differences were found between patients assigned sPN and patients assigned GlnPN regarding any of the endpoints. Glutamine supplementation was not associated with adverse effects. CONCLUSIONS: In newborns and infants after major digestive-tract surgery, we did not identify beneficial effects of isonitrogenous, isocaloric glutamine supplementation of parenteral nutrition. Glutamine supplementation in these patients therefore is not warranted until further research proves otherwise.

Quantification of free sialic acid in urine by HPLC-electrospray tandem mass spectrometry: a tool for the diagnosis of sialic acid storage disease.

BACKGROUND: Sialic acid storage diseases (SSDs) are severe autosomal recessive neurodegenerative disorders caused by a transport defect across the lysosomal membrane, which leads to accumulation of sialic acid in tissues, fibroblasts, and urine. Defective free sialic acid transport can be established by quantification of free sialic acid in urine. METHODS: Urine sample size was adjusted to the equivalent of 100 nmol of creatinine. After addition of 2-keto-3-deoxy-d-glycero-d-galactonononic acid as internal standard, samples were diluted with water to an end volume of 250 microL. We used 10 microL for HPLC-tandem mass spectrometric analysis in the negative electrospray ionization mode, monitoring transitions m/z 308.3-->m/z 86.9 (sialic acid) and m/z 267.2-->m/z 86.9 (internal standard). The overall method was validated and studied for ion suppression, interfering compounds, and pH effects. Samples from controls (n = 72) and SSD patients (n = 3) were analyzed. RESULTS: The limit of detection was 3 micromol/L. Intraassay imprecision (CV; n = 10) was 6%, 3%, and 2% at 30, 130, and 1000 mmol/mol creatinine, respectively; corresponding interassay CV (n = 10) were 5%, 5%, and 2%. Recovery was 109% (100-1000 mmol/mol creatinine). The mean (SD) [range] excretion rates (mmol/mol creatinine) were 31.3 (16.6) [0.7-56.9] at 0-1 year (n = 20), 21.2 (9.8) [6.3-38.3] at 1-3 years (n = 15), 14.4 (8.2) [1.7-32.9] at 3-10 years (n = 25), and 4.6 (2.6) [0-9.8] above age 10 years (n = 12). SSD patients 1.2, 3.9, and 12 years of age had concentrations of 111.5, 54.2, and 36.1 mmol/mol creatinine, respectively. CONCLUSIONS: The HPLC-tandem MS method for free sialic acid in urine is more rapid, accurate, sensitive, selective, and robust than earlier methods and may serve as a candidate reference method for free sialic acid in diagnosis of SSD.