Mutations of GEMIN5 are associated with coenzyme Q10 deficiency: long-term follow-up after treatment.

GEMIN5 exerts key biological functions regulating pre-mRNAs intron removal to generate mature mRNAs. A series of patients were reported harboring mutations in GEMIN5. No treatments are currently available for this disease. We treated two of these patients with oral Coenzyme Q10 (CoQ10), which resulted in neurological improvements, although MRI abnormalities remained. Whole Exome Sequencing demonstrated compound heterozygosity at the GEMIN5 gene in both cases: Case one: p.Lys742* and p.Arg1016Cys; Case two: p.Arg1016Cys and p.Ser411Hisfs*6. Functional studies in fibroblasts revealed a decrease in CoQ10 biosynthesis compared to controls. Supplementation with exogenous CoQ10 restored it to control intracellular CoQ10 levels. Mitochondrial function was compromised, as indicated by the decrease in oxygen consumption, restored by CoQ10 supplementation. Transcriptomic analysis of GEMIN5 patients compared with controls showed general repression of genes involved in CoQ10 biosynthesis. In the rigor mortis defective flies, CoQ10 levels were decreased, and CoQ10 supplementation led to an improvement in the adult climbing assay performance, a reduction in the number of motionless flies, and partial restoration of survival. Overall, we report the association between GEMIN5 dysfunction and CoQ10 deficiency for the first time. This association opens the possibility of oral CoQ10 therapy, which is safe and has no observed side effects after long-term therapy.

L-Serine dietary supplementation is associated with clinical improvement of loss-of-function GRIN2B-related pediatric encephalopathy.

Autosomal dominant mutations in GRIN2B are associated with severe encephalopathy, but little is known about the pathophysiological outcomes and any potential therapeutic interventions. Genetic studies have described the association between de novo mutations of genes encoding the subunits of the N-methyl-d-aspartate receptor (NMDAR) and severe neurological conditions. Here, we evaluated a missense mutation in GRIN2B, causing a proline-to-threonine switch (P553T) in the GluN2B subunit of NMDAR, which was found in a 5-year-old patient with Rett-like syndrome with severe encephalopathy. Structural molecular modeling predicted a reduced pore size of the mutant GluN2B-containing NMDARs. Electrophysiological recordings in a HEK-293T cell line expressing the mutated subunit confirmed this prediction and showed an associated reduced glutamate affinity. Moreover, GluN2B(P553T)-expressing primary murine hippocampal neurons showed decreased spine density, concomitant with reduced NMDA-evoked currents and impaired NMDAR-dependent insertion of the AMPA receptor subunit GluA1 at stimulated synapses. Furthermore, the naturally occurring coagonist d-serine restored function to GluN2B(P553T)-containing NMDARs. l-Serine dietary supplementation of the patient was hence initiated, resulting in the increased abundance of d-serine in the plasma and brain. The patient has shown notable improvements in motor and cognitive performance and communication after 11 and 17 months of l-serine dietary supplementation. Our data suggest that l-serine supplementation might ameliorate GRIN2B-related severe encephalopathy and other neurological conditions caused by glutamatergic signaling deficiency.

Free-thiamine is a potential biomarker of thiamine transporter-2 deficiency: a treatable cause of Leigh syndrome.

Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other causes of Leigh syndrome, early administration of thiamine and biotin has a dramatic and immediate clinical effect. New biochemical markers are needed to aid in early diagnosis and timely therapeutic intervention. Thiamine derivatives were analysed by high performance liquid chromatography in 106 whole blood and 38 cerebrospinal fluid samples from paediatric controls, 16 cerebrospinal fluid samples from patients with Leigh syndrome, six of whom harboured mutations in the SLC19A3 gene, and 49 patients with other neurological disorders. Free-thiamine was remarkably reduced in the cerebrospinal fluid of five SLC19A3 patients before treatment. In contrast, free-thiamine was slightly decreased in 15.2% of patients with other neurological conditions, and above the reference range in one SLC19A3 patient on thiamine supplementation. We also observed a severe deficiency of free-thiamine and low levels of thiamine diphosphate in fibroblasts from SLC19A3 patients. Surprisingly, pyruvate dehydrogenase activity and mitochondrial substrate oxidation rates were within the control range. Thiamine derivatives normalized after the addition of thiamine to the culture medium. In conclusion, we found a profound deficiency of free-thiamine in the CSF and fibroblasts of patients with thiamine transporter-2 deficiency. Thiamine supplementation led to clinical improvement in patients early treated and restored thiamine values in fibroblasts and cerebrospinal fluid.

Pyridoxal Phosphate Supplementation in Neuropediatric Disorders.

Pyridoxal phosphate (PLP) is the active form of vitamin B6 and a cofactor in many enzyme reactions including neurotransmitter metabolism. PLP metabolism disturbances may mostly lead to refractory seizures. In this report, we review the main pathophysiological factors related with PLP deficiency and our experience in PLP treatment in pediatric patients with low-normal cerebrospinal fluid PLP values who presented epilepsy. Only one case had a definite diagnosis (Phelan-McDermid syndrome). The results of extensive metabolic workups and targeted genetic studies were normal for all patients. In 5 cases, the response to PLP supplementation (10-30mg/kg/d) was initially positive. PLP adverse reactions were noticed in 4 patients and PLP was discontinued; however, one of the most noticeable symptoms was an asymptomatic increase in liver enzymes. These negative results with PLP supplementation are worth reporting, to improve the information we use to treat our patients.

Clinical, etiological and therapeutic aspects of cerebral folate deficiency.

Cerebral folate deficiency is defined as any neurological condition associated with low cerebrospinal fluid folate concentrations. It is becoming increasingly associated with several neurological diseases, either genetic or environmental. Treatment of cerebral folate deficiency by folate supplementation is generally effective, improving the neurological outcome of some patients. However, to treat cerebral folate deficiency, the proper choice of one of the available folate forms is essential. The distinct brain folate metabolism features compared with peripheral folate metabolic pathways strongly suggest the investigation of different folate forms, such as the biologically active folinic acid and 5-methyltetrahydrofolate, since they are efficiently transported to the brain. Regarding the oral doses of the different folate forms, despite the fact that there are some recommendations, there is no general consensus. Further investigation and designing clinical trials are advisable to elucidate these aspects.

Follow-up of folinic acid supplementation for patients with cerebral folate deficiency and Kearns-Sayre syndrome.

BACKGROUND: Kearns-Sayre syndrome (KSS) is a mitochondrial DNA deletion syndrome that presents with profound cerebral folate deficiency and other features. Preliminary data support the notion that folinic acid therapy might be useful in the treatment of KSS patients. Our aim was to assess the clinical and neuroimaging outcomes of KSS patients receiving folinic acid therapy. PATIENTS: We recruited eight patients with diagnoses of KSS. Four cases were treated at 12 de Octubre Hospital, and the other two cases were treated at Sant Joan de Déu Hospital. Two patients refused to participate in the treatment protocol. METHODS: Clinical, biochemical and neuroimaging data (magnetic resonance imaging or computed tomography scan) were collected in baseline conditions and at different time points after the initiation of therapy. Cerebrospinal fluid 5-methyltetrahydrofolate levels were analysed with HPLC and fluorescence detection. Large-scale mitochondrial DNA deletions were analysed by Southern blot. TREATMENT PROTOCOL: The follow-up periods ranged from one to eight years. Cases 1-4 received oral folinic acid at a dose of 1 mg/kg/day, and cases 6 and 8 received 3 mg/kg/day. RESULTS: No adverse effects of folinic acid treatment were observed. Cerebral 5-methyltetrahydrofolate deficiencies were observed in all cases in the baseline conditions. Moreover, all three patients who accepted lumbar puncture after folinic acid therapy exhibited complete recoveries of their decreased basal cerebrospinal fluid 5-methyltetrahydrofolate levels to normal values. Two cases neurologically improved after folinic therapy. Disease worsened in the other patients. Post-treatment neuroimaging was performed for the 6 cases that received folinic acid therapy. One patient exhibited improvements in white matter abnormalities. The remaining patients displayed progressions in subcortical cerebral white matter, the cerebellum and cerebral atrophy. CONCLUSIONS: Four patients exhibited clinical and radiological progression of the disease following folinic acid treatment. Only one patient who was treated in an early stage of the disease exhibited both neurological and radiological improvements following elevated doses of folinic acid, and an additional patient experienced neurological improvement. Early treatment with high-dose folinic acid therapy seems to be advisable for the treatment of KSS. TRIAL REGISTRATION: Eudrac T2007-00-6748-23.

Biochemical parameters to assess choroid plexus dysfunction in Kearns-Sayre syndrome patients.

Our aim was to assess biochemical parameters to detect choroid plexus dysfunction in Kearns-Sayre syndrome (KSS) patients. We studied CSF from 7 patients with KSS including total proteins, 5-methyltetrahydrofolate, homovanillic acid (HVA) and Selenium (Se) concentrations. High Se values, increased HVA and total protein concentrations and decreased 5-MTHF values were observed in all cases. This pattern seems very specific to KSS since it was only detected in 7 patients out of 1850 CSF samples analysed, and may represent a good biochemical model for evaluating choroid plexus dysfunction. The accumulated Se in CSF might have deleterious consequences such as toxicity effects.

Cerebral folate deficiency syndromes in childhood: clinical, analytical, and etiologic aspects.

BACKGROUND: Cerebral folate deficiency may be amenable to therapeutic supplementation. Diverse metabolic pathways and unrelated processes can lead to cerebrospinal fluid 5-methyltetrahydrofolate (5-MTHF) depletion, the hallmark of cerebral folate deficiency. OBJECTIVE: To analyze cerebral folate abundance in a large prospective series of children diagnosed with any neurologic disorder for which a diagnostic lumbar puncture was indicated. DESIGN: We studied the spectrum and frequency of disorders associated with cerebral folate deficiency by measuring cerebrospinal fluid 5-MTHF, biogenic amines, and pterins. Direct sequencing of the FOLR1 transporter gene was also performed in some patients. SETTING: Academic pediatric medical center. PARTICIPANTS: We studied 134 individuals free of neurometabolic disease and 584 patients with any of several diseases of the central nervous system. RESULTS: Of 584 patients, 71 (12%) exhibited 5-MTHF deficiency. Mild to moderate deficiency (n = 63; range, 19-63 nmol/L) was associated with perinatal asphyxia, central nervous system infection, or diseases of probable genetic origin (inborn errors of metabolism, white matter disorders, Rett syndrome, or epileptic encephalopathies). Severe 5-MTHF depletion (n = 8; range, 0.6-13 nmol/L) was detected in severe MTHF reductase deficiency, Kearns-Sayre syndrome, biotin-responsive striatal necrosis, acute necrotizing encephalitis of Hurst, and FOLR1 defect. A strong correlation was observed between cerebrospinal fluid and plasma folate levels in cerebral folate deficiency. CONCLUSIONS: Of the 2 main forms of cerebral folate deficiency identified, mild to moderate 5-MTHF deficiency was most commonly associated with disorders bearing no primary relation to folate metabolism, whereas profound 5-MTHF depletion was associated with specific mitochondrial disorders, metabolic and transporter defects, or cerebral degenerations. The results suggest that 5-MTHF can serve either as the hallmark of inborn disorders of folate transport and metabolism or, more frequently, as an indicator of neurologic dysfunction.

The monitoring of trace elements in blood samples from patients with inborn errors of metabolism.

Patients having inborn errors of intermediary metabolism (IEMs) may have element deficiencies related to dietary treatment. Our objective was to study several elements [cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), manganese (Mn), molybdenum (Mo) and magnesium (Mg)] in patients with IEMs with and without dietary treatment and to compare these results with those established in a healthy paediatric population. We studied 72 patients with IEMs (age range 2 months-44 years; median 10.5 years), with and without protein-restricted dietary treatment. Control values were established in 92 subjects (age range 1 day-42 years; median 6.5 years). Dietary treatment consisted of a natural protein-restricted diet supplemented with a special formula, depending on the specific metabolic defect. Samples were analysed with an Agilent 7500ce-ICP mass spectrometer. Significant differences were observed when we compared patients under dietary treatment and control values for Se and Co (P < 0.0001). No differences were observed for the other elements when the different groups were compared, except for Co (IEM patients without dietary treatment vs control group; P = 0.003). For Se and cobalamin, the daily intake of our patients (Se 48 ± 16 µg/day; cobalamin 3.5 µg/day) was slightly higher than the recommended daily averages (RDAs) (40 µg/day and 1.8 µg/day, respectively). We concluded that IEM patients under dietary treatment showed significantly lower selenium values in spite of correct supplementation, reinforcing the idea that these patients should be regularly monitored, at least for this element. Further investigations seem advisable about Se and Co availability in special diets.