D-lactic acidosis: an unusual cause of encephalopathy in a patient with short bowel syndrome.

A 24-year-old woman with a short bowel syndrome following post-ischemic small bowel resection, developed several episodes of lethargy, echolalia and ataxia. D-lactic acidosis was identified as the cause of neurological disturbances. This infrequent disorder can be precipitated by intake of a large amount of sugars, in patients with short bowel syndrome. It should be suspected in the presence of metabolic acidosis with increased anion gap and a normal level of L-lactic acid. The diagnosis relies on the specific dosage of D-lactic stereoisomer. Proper management involves rehydration, diet adaptation and oral administration of poorly absorbed antibiotics in order to modify the colonic flora responsible for D-lactic production.

L-2-hydroxyglutaric aciduria, a defect of metabolite repair.

L-2-hydroxyglutaric aciduria is a metabolic disorder in which L-2-hydroxyglutarate accumulates as a result of a deficiency in FAD-linked L-2-hydroxyglutarate dehydrogenase, a mitochondrial enzyme converting L-2-hydroxyglutarate to alpha-ketoglutarate. The origin of the L-2-hydroxyglutarate, which accumulates in this disorder, is presently unknown. The oxidation-reduction potential of the 2-hydroxyglutarate/alpha-ketoglutarate couple is such that L-2-hydroxyglutarate could potentially be produced through the reduction of alpha-ketoglutarate by a NAD- or NADP-linked oxidoreductase. In fractions of rat liver cytosolic extracts that had been chromatographed on an anion exchanger we detected an enzyme reducing alpha-ketoglutarate in the presence of NADH. This enzyme co-purified with cytosolic L-malate dehydrogenase (cMDH) upon further chromatography on Blue Sepharose. Mitochondrial fractions also contained an NADH-linked, 'alpha-ketoglutarate reductase', which similarly co-purified with mitochondrial L-malate dehydrogenase (mMDH). Purified mMDH catalysed the reduction of alpha-ketoglutarate to L-2-hydroxyglutarate with a catalytic efficiency that was about 10(7)-fold lower than that observed with oxaloacetate. For the cytosolic enzyme, this ratio amounted to 10(8), indicating that this enzyme is more specific. Both cMDH and mMDH are highly active in tissues and alpha-ketoglutarate is much more abundant than oxaloacetate and more concentrated in mitochondria than in the cytosol. As a result of this, the weak activity of mMDH on alpha-ketoglutarate is sufficient to account for the amount of L-2-hydroxyglutarate that is excreted by patients deficient in FAD-linked L-2-hydroxyglutarate dehydrogenase. The latter enzyme appears, therefore, to be responsible for a 'metabolite repair' phenomenon and to belong to the expanding class of 'house-cleaning' enzymes.

L-2-Hydroxyglutaric aciduria: clinical, genetic, and brain MRI characteristics in two adult sisters.

L-2-Hydroxyglutaric (L-2-HG) aciduria is a rare inherited metabolic disease usually observed in children. Patients present a very slowly progressive deterioration with cerebellar ataxia, mild or severe mental retardation, and various other clinical signs including extrapyramidal and pyramidal symptoms, and seizures. The disease is characterized by increased levels of L-2-HG in body fluids such as urine and cerebrospinal fluid. We report on two sisters from consanguineous parents, in whom L-2-HG aciduria was diagnosed at an adult age. Although magnetic resonance imaging and spectroscopic findings were severely abnormal in both, they experienced a different clinical course. The older sister presented with severe mental retardation, recurrent epileptic seizures, and progressive deterioration in her ability to walk and to talk; she is now confined to a wheelchair with severe speech deficit. In contrast, the younger sister only had a few epileptic seizures in childhood and moderate mental retardation, is still able to walk, and performs manual work, and has a social life in a specialized institution for moderately mentally handicapped persons. For the two patients, a complete deletion of exon 9 was demonstrated in a gene located on chromosome 14q22.1, which most probably encodes for L-2-hydroxyglutarate dehydrogenase. The pathological findings observed in this metabolic disorder could therefore be related to a toxic effect of L-2-hydroxyglutarate on the central nervous system, although the presence of other toxic metabolites cannot be excluded.

Orthotopic liver transplantation from a living-related donor in an infant with a peroxisome biogenesis defect of the infantile Refsum disease type.

Peroxisomal biogenesis defects include a number of severe neurodevelopmental disorders, among which infantile Refsum disease (IRD) occupies the mildest end of the spectrum. Although high docosahexaenoic acid (DHA) and low phytanic acid diets can correct some of the biochemical defects, they have not consistently altered the progressive course of the disease. We carried out orthotopic liver transplantation (OLT) in a mildly symptomatic 6-month-old infant who was a sibling of a severely neurologically impaired older sister. After transplantation the clinical course of this young child appeared much improved by comparison to her older sister. She walked alone at 4 years, had acceptable social interaction and had a noticeable recovery of audition. After transplantation her biochemical parameters were significantly improved: phytanic acid and very long-chain fatty acid (VLCFA) serum concentrations decreased. Abnormal bile acids disappeared from plasma. Although the OLT did not result in a cure of the disorder, the clinical and biochemical results suggest that OLT should be considered in mildly symptomatic patients.

Adenylosuccinate lyase deficiency: study of physiopathologic mechanism(s).

Nucleotide concentrations were normal in adenylosuccinate lyase-deficient fibroblasts, and the succinylpurines were not toxic for cultured neuronal cells.

Adenylosuccinate lyase deficiency--first British case.

A deficiency of adenylosuccinate lyase (ASDL) is characterised by the accumulation of SAICAriboside (SAICAr) and succinyladenosine (S-Ado) in body fluids. The severity of the clinical presentation correlates with a low S-Ado/SAICAr ratio in body fluids. We report the first British case of ADSL deficiency. The patient presented at 14 days with a progressive neonatal encephalopathy and seizures. There was marked axial and peripheral hypotonia. Brain MRI showed widespread white matter changes. She died at 4 weeks of age. Concentrations of SAICAr and SAdo were markedly elevated in urine, plasma and CSF and the SAdo/SAICAr ratio was low, consistent with the severe phenotype. The patient was compound heterozygous for 2 novel ADSL mutations; c.9 G>C (A3P) and c.572 C>T (R190X).

Mutation of a nuclear respiratory factor 2 binding site in the 5' untranslated region of the ADSL gene in three patients with adenylosuccinate lyase deficiency.

Adenylosuccinate lyase (ADSL; also called "adenylosuccinase") catalyzes two steps in the synthesis of purine nucleotides: (1) the conversion of succinylaminoimidazolecarboxamide ribotide into aminoimidazolecarboxamide ribotide and (2) the conversion of adenylosuccinate into adenosine monophosphate. ADSL deficiency, a recessively inherited disorder, causes variable-but most often severe-mental retardation, frequently accompanied by epilepsy and/or autism. It is characterized by the accumulation, in body fluids, of succinylaminoimidazolecarboxamide riboside and succinyladenosine, the dephosphorylated derivatives of the two substrates of the enzyme. Analysis of the ADSL gene of three unrelated patients with ADSL deficiency, in whom one of the ADSL alleles displayed a normal coding sequence, revealed a -49T-->C mutation in the 5' untranslated region of this allele. Measurements of the amount of mRNA transcribed from the latter allele showed that it was reduced to approximately 33% of that transcribed from the alleles mutated in their coding sequence. Further investigations showed that the -49T-->C mutation provokes a reduction to 25% of wild-type control of promoter function, as evaluated by luciferase activity and mRNA level in transfection experiments. The mutation also affects the binding of nuclear respiratory factor 2 (NRF-2), a known activator of transcription, as assessed by gel-shift studies. Our findings indicate that a mutation of a regulatory region of the ADSL gene might be an unusually frequent cause of ADSL deficiency, and they suggest a role for NRF-2 in the gene regulation of the purine biosynthetic pathway.

Niemann-Pick disease type B: an unusual clinical presentation with multiple vertebral fractures.

We report here a unique case of a 55-year-old woman presenting with a clinical picture of Parkinson disease, severe back pain, splenomegaly, and pronounced dyspnea. Radiographic examination of the spine showed multiple vertebral fractures. Niemann-Pick disease type B was diagnosed by findings of lipid-loaded histiocytes and a strongly reduced sphingomyelinase enzyme activity. She was homozygous for the deletion of codon 608 (delR608), which encodes an arginine residue in the Acid Sphingomyelinase gene. To investigate the cause of the unusual vertebral fractures, we screened for polymorphisms previously described as possibly associated with increased risk for osteoporosis and fractures. Our patient was heterozygous for the polymorphisms of the vitamin D receptor gene, the estrogen receptor gene, and the collagen 1A1gene. Increased physical activity after Parkinson treatment, a genetic predisposition, together with worsening disease due to interfering medications could explain the dramatic presentation of this patient. She was treated with cholesterol lowering drugs such as statins to decrease sphingomyelin synthesis, avoidance of drugs that inhibit sphingomyelinase, and bisphosphonates. No new fractures have occurred, but the interstitial lung disease has progressed.

Molecular analysis of the mevalonate kinase gene in a cohort of patients with the hyper-igd and periodic fever syndrome: its application as a diagnostic tool.

BACKGROUND: The hyper-IgD and periodic fever syndrome (HIDS) is characterized by recurrent attacks of fever, abdominal distress, and arthralgia and is caused by mevalonate kinase mutations. OBJECTIVE: To ascertain the role of mevalonate kinase and the usefulness of molecular diagnosis in HIDS. DESIGN: Cross-sectional study. SETTING: The international Nijmegen HIDS registry. PATIENTS: 54 patients from 41 families who met the clinical criteria for HIDS. MEASUREMENTS: Clinical symptoms and signs, immunoglobulin concentration, leukocyte count, erythrocyte sedimentation rate, mutation analysis, and mevalonate kinase enzyme activity assay. RESULTS: There were two groups of patients: 41 patients with mevalonate kinase mutations (classic-type HIDS) and 13 patients without mutations (variant-type HIDS). Patients with classic-type HIDS had a lower mevalonate kinase enzyme activity, a higher IgD level, and more additional symptoms with attacks. The IgD level did not correlate with disease severity, mevalonate kinase enzyme activity, or genotype. CONCLUSION: Genetic heterogeneity exists among patients with a clinical diagnosis of HIDS.

Molecular analysis of MVK mutations and enzymatic activity in hyper-IgD and periodic fever syndrome.

Hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS) is an autosomal recessive inflammatory disorder characterised by recurrent episode of fever associated with lymphadenopathy, abdominal distress, joint involvement and skin lesions. We recently demonstrated that mutations in the mevalonate kinase gene (MVK) are associated with HIDS. Direct DNA sequencing was done to screen the entire coding region of MVK in 25 unrelated patients with HIDS. Mutations were detected in the coding region of the gene including 11 missense mutations, one deletion, the absence of expression of one allele, as well as three novel polymorphisms. Seven of these mutations are novel. The large majority of the patients were compound heterozygotes for two mutations. Of these, V377I (G-->A) is the most common mutation occurring in 20 unrelated patients and was found to be associated with I268T in six patients. Mutations were associated with a decrease of mevalonate kinase (MK) (ATP:mevalonate 5-phosphotransferase, EC 2.7.I.36) enzymatic activity but not as profound as in mevalonic aciduria, a syndrome also caused by a deficient activity of MK. In HIDS the mutations are located all along the protein which is different from mevalonic aciduria where MK mutations are mainly clustered to a same region of the protein. On the basis of this study, we propose that the diagnostic screen of MVK in HIDS should be first directed on V377I and I268T mutations. Three patients are also described to illustrate the genotypic and phenotypic overlap with mevalonic aciduria.

Phosphorylation and activation of heart PFK-2 by AMPK has a role in the stimulation of glycolysis during ischaemia.

BACKGROUND: The role of protein phosphorylation in the Pasteur effect--the phenomenon whereby anaerobic conditions stimulate glycolysis--has not been addressed. The AMP-activated protein kinase (AMPK) is activated when the oxygen supply is restricted. AMPK acts as an energy-state sensor and inhibits key biosynthetic pathways, thus conserving ATP. Here, we studied whether AMPK is involved in the Pasteur effect in the heart by phosphorylating and activating 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of fructose 2,6-bisphosphate, a potent stimulator of glycolysis. RESULTS: Heart PFK-2 was phosphorylated on Ser466 and activated by AMPK in vitro. In perfused rat hearts, anaerobic conditions or inhibitors of oxidative phosphorylation (oligomycin and antimycin) induced AMPK activation, which correlated with PFK-2 activation and with an increase in fructose 2,6-bisphosphate concentration. Moreover, in cultured cells transfected with heart PFK-2, oligomycin treatment resulted in a parallel activation of endogenous AMPK and PFK-2. In these cells, the activation of PFK-2 was due to the phosphorylation of Ser466. A dominant-negative construct of AMPK abolished the activation of endogenous and cotransfected AMPK, and prevented both the activation and phosphorylation of transfected PFK-2 by oligomycin. CONCLUSIONS: AMPK phosphorylates and activates heart PFK-2 in vitro and in intact cells. AMPK-mediated PFK-2 activation is likely to be involved in the stimulation of heart glycolysis during ischaemia.

Clinical, biochemical and molecular genetic correlations in adenylosuccinate lyase deficiency.

Adenylosuccinate lyase (ADSL) deficiency (MIM 103050) is an autosomal recessive inborn error of purine synthesis characterized by the accumulation in body fluids of succinylaminoimidazolecarboxamide (SAICA) riboside and succinyladenosine (S-Ado), the dephosphorylated derivatives of the two substrates of the enzyme. Because ADSL-deficient patients display widely variable degrees of psychomotor retardation, we have expressed eight mutated ADSL enzymes as thioredoxin fusions and compared their properties with the clinical and biochemical characteristics of 10 patients. Three expressed mutated ADSL enzymes (M26L, R426H and T450S) were thermolabile, four (A2V, R141W, R303C and S395R) were thermostable and one (del206-218), was inactive. Thermolabile mutations decreased activities with SAICA ribotide (SAICAR) and adenylosuccinate (S-AMP) in parallel, or more with SAICAR than with S-AMP. Patients homozygous for one of these mutations, R426H, displayed similarly decreased ADSL activities in their fibroblasts, S-Ado:SAICA riboside ratios of approximately 1 in their cerebrospinal fluid and were profoundly retarded. With the exception of A2V, thermostable mutations decreased activity with S-AMP to a much more marked extent than with SAICAR. Two unrelated patients homozygous for one of the thermostable mutations, R303C, also displayed a much more marked decrease in the activity of fibroblast ADSL with S-AMP than with SAICAR, had S-Ado:SAICA riboside ratios between 3 and 4 in their cerebrospinal fluid and were mildly retarded. These results suggest that, in some cases, the genetic lesion of ADSL determines the ratio of its activities with S-AMP versus SAICAR, which in turn defines the S-Ado:SAICA riboside ratio and the patients' mental status.

Identification of undescribed medium-chain acylcarnitines present in urine of patients with propionic and methylmalonic acidemias.

In urine of patients with propionyl-CoA carboxylase deficiency or with methylmalonic acidemia, carnitine esters of 2-methyl-branched fatty acids of all chain lengths between 4 and 9 atoms of carbon were identified during the acute phase of the diseases. The chemical structure of these compounds was obtained by gas chromatography-mass spectrometry analysis of their fatty acid moieties in their free and picolinyl ester forms. We suggest mechanisms for the biosynthesis of these branched fatty acids, and their accumulation in urine during episodes of caloric imbalance.

Prenatal diagnosis in adenylosuccinate lyase deficiency.

Adenylosuccinate lyase deficiency, an autosomal recessive inborn error of purine synthesis, provokes accumulation in body fluids of succinylaminoimidazolecarboxamide riboside and succinyladenosine, the dephosphorylated derivatives of the two substrates of the enzyme. Most patients display severe psychomotor retardation, often accompanied by epilepsy and/or autistic features, although some are only mildly retarded. About 20 mutations are known. Prenatal diagnosis was performed twice on chorion villi of the mother of a previously diagnosed patient with a C5T mutation (exon 1) on the maternal allele, and a C1185A mutation (exon 11) on the paternal allele. Both suppress a Fnu4HI restriction site. In a first fetus, incubation of PCR products generated from genomic DNA of exon 1 with Fnu4HI yielded a 113 bp fragment from a control and the father's gene, and both a 113 bp and 170 bp fragment from the mother, affected sibling and fetus. Incubation of PCR products of exons 11-12 with Fnu4HI yielded a 550 bp fragment from a control and the mother's gene, and a 550 bp and 600 bp fragment from the father, affected sibling and fetus. Assay of adenylosuccinate lyase on the aborted fetal liver confirmed the enzyme deficiency. A second fetus displayed only the maternal mutation.

Identification of new medium-chain acylcarnitines present in urine of a patient with medium-chain acyl-CoA dehydrogenase deficiency.

Previously undescribed medium-chain acylcarnitines were identified in a urine sample from a patient with medium-chain acyl-CoA dehydrogenase deficiency. These are the 4-methylvaleryl, 4- and 5-methylhexanoyl, 6-methylheptanoyl-, 6-methyloctanoyl-, 4,5-dimethylhexanoyl- and 4,7-decadienoylcarnitines. Their chemical structures were obtained by gas chromatographymass spectrometry analysis of their fatty acid moieties as picolinyl esters.

Mutation analysis in adenylosuccinate lyase deficiency: eight novel mutations in the re-evaluated full ADSL coding sequence.

The deficiency of adenylosuccinate lyase (ADSL, also termed adenylosuccinase) is an autosomal recessive disorder characterized by the accumulation in body fluids of succinylaminoimidazole-carboxamide riboside (SAICA-riboside) and succinyladenosine (S-Ado). Most ADSL-deficient children display marked psychomotor delay, often accompanied by epilepsy or autistic features, or both, although some patients may be less profoundly retarded. Occasionally, growth retardation and muscular wasting are also present. Up to now, nine missense mutations of the ADSL gene had been reported in six apparently unrelated sibships. In the present study of 10 additional patients with ADSL deficiency, nine point mutations, among which seven unreported missense mutations, and the first splicing error reported in this disorder, have been identified. These mutations have been characterized, taking into account the finding that the cDNA of human ADSL is 75 nucleotides longer at its 5'-end, and encodes a protein of 484 rather than 459 amino acids as previously reported. Five apparently unrelated patients were found to carry a R426H mutation. With the exceptions of the latter mutation, of a R190Q mutation that had been reported previously, and of a K246E mutation that was found in two unrelated patients, all other mutations were found only in a single family.

Adenylosuccinase deficiency: possibly underdiagnosed encephalopathy with variable clinical features.

Adenylosuccinase deficiency is an autosomal recessive inherited defect of purine synthesis. In enzyme deficient patients, two normally undetectable compounds, succinylaminoimidazole carboxamide riboside and succinyladenosine, accumulate in urine, cerebrospinal fluid and, to a minor extent, in plasma. Analysing 150 highly selected urine specimens from patients with unidentified neurogenerative disorders we discovered the first two German cases of adenylosuccinase deficiency. The deficiency causes moderate to severe mental retardation, often accompanied by epileptic seizures and/or autistic features, and is occasionally associated with growth retardation and muscular hypotonia. Of the two German cases we present here, one patient fits into the clinical picture outlined by previous reports. The other patient, however, shows a pattern of symptoms so far undescribed: severe early infantile epileptic encephalopathy with reduced myelination. On mutation analysis this patient is the first to reveal a 39 base pair deletion in the adenylosuccinase gene in contrast to the point mutations detected in previous cases. Adenylosuccinase deficiency may be an underdiagnosed metabolic disorder with variable expression. This should be taken into consideration in patients with unclassified neurological conditions.