[Archives of Pediatrics 2003: continuity and changes].
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Biomedical subjects
Publications and source records attributed to M Odièvre.
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A North African boy, the son of consanguineous parents, presented at 8 years of age with hypophosphataemic rickets due to De Toni-Debré-Fanconi syndrome. Hepatomegaly and abnormalities of carbohydrate metabolism were suggestive of Fanconi-Bickel syndrome. This was confirmed by the detection of a mutation within GLUT2, the gene encoding the liver-type facilitative glucose transporter. The study of the respiratory chain revealed a deficiency of complexes I, III and IV in muscle. Mechanisms responsible for an impairment ofmitochondrial function, which we interpret as a secondary phenomenon, are discussed.
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Bromocriptine combined with galactose restriction in the matenal diet seems to be partially effective in decreasing endogenous lactose and galactose synthesis, monitored in a pregnant woman heterozygous for galactosaemia at risk of producing a homozygous infant.
Forty-eight patients with glycogen storage disease type Ia (GSD Ia) were studied. Using a combination of single-strand conformation polymorphism (SSCP) analysis, restriction enzyme digestion and direct sequencing, we were able to identify 93/96 mutant alleles, comprising 23 different mutations in the glucose-6-phosphatase gene (G6PC). Among these, 7 are novel mutations of G6PC: M5R, T111I, A241T, C270R, F322L, and two deletions, 793delG and 872delC, resulting in the same mutation at the amino acid level, fs300Ter (300X).
UNLABELLED: Recent studies have shown a high prevalence of calcium and vitamin D deficiencies in adolescents. The aim of this present study was to follow the changes in calcium status and 25 hydroxyvitamin D (25[OH]D) and parathyroid hormone (iPTH) levels during winter in preadolescents and adolescents from four university hospitals in northern France. SUBJECTS AND METHODS: Two groups of teenagers and adolescents (range: 10-15 years) were followed from October 1996 to June 1997. They were given either 100,000 IU of vitamin D (treated group n = 33) or a placebo (control group n = 35) in October, January and April. Serum calcium, phosphate, 25(OH)D and iPTH levels were measured at inclusion and every three months thereafter. RESULTS: At inclusion, plasma or serum 25(OH)D levels were < or = 10 ng/mL in 16 subjects and < 6 ng/mL in six. In control children, no significant change in 25(OH)D occurred during the study, while plasma or serum iPTH levels increased to 34 +/- 11 pg/mL. In the treated groups, 25(OH)D levels remained > 20 ng/mL in every subject; no hypercalcemia was observed; and the mean plasma or serum iPTH level was 25 +/- 14 pg/mL at the end of the study. CONCLUSION: Teenagers presented with a high prevalence of biological vitamin D deficiency at the end of summer. The increase of iPTH during winter in the unsupplemented group suggests that this has secondary consequences on their calcium homeostasis unless they are supplemented with vitamin D. We advocate a sufficient calcium supply and a 100,000 IU vitamin D supplement given two or three times during winter to preadolescents and adolescents living in northern France.
In patients with glycogen storage disease type Ia (glucose-6-phosphatase deficiency), serum triglyceride concentrations are markedly raised, whereas phospholipids and cholesterol levels are only moderately elevated. In addition, both VLDL and LDL lipoprotein fractions are raised. Despite these abnormalities, endothelial vascular dysfunction and atherosclerosis seem to be rare in such patients. In view of the crucial role of apolipoprotein E (apoE) in lipid metabolism, we studied both apoE polymorphism (40 patients) and serum concentration (20 patients) in patients with glycogen storage disease type Ia. The distribution of each allele at the apoE locus was similar to that reported in the general population, whereas serum apoE concentrations were raised in our patients. Raised apoE levels in the serum could play an important role in counterbalancing the at-risk-for-atherosclerosis lipid profile of patients with glycogen storage disease type Ia. Moreover, E3 and E4 polymorphisms, predominant in our patients, have a high triglyceride binding capacity and are thus able to increase triglyceride clearance. However, the origin of raised concentrations of apoE is not completely clear though, bearing in mind previous reports regarding serum protein concentrations in such patients, increased hepatic synthesis is likely.
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Methionine synthase reductase (EC 2.1.1.135) is a flavoprotein essential for maintenance of methionine synthase in an active state. We characterized the human gene for methionine synthase reductase (MTRR). The gene is approximately 34kb and comprises 15 exons, varying in size from 43 to 1213bp, and 14 introns whose sizes vary from 108bp to 5kb. The positions of several junctions are conserved between the MTRR gene and the C. elegans ortholog, as well as with the rat cytochrome P450 reductase gene. A 1.3kb CpG island encompasses the 5'-flanking region and exon 1 and extends into intron 1. A short region including the transcription start site is sufficient to confer promoter activity, with a better outcome when accompanied by intron 1. The promoter region contains putative binding sites for Sp1, AP-1, AP-2 as well as CAAT motifs, but no consensus TATA box. Primer extension analysis revealed a single major transcription start site, located 137bp upstream of the previously reported initiator ATG. An alternative splicing event involving a portion of exon 1 predicts that translation can potentially be initiated at two different ATG codons. The gene was physically assigned to a narrow area between markers WI1755 and D5S1957.
An 18-month-old girl presented with macrocytic megaloblastic anaemia followed by haemolytic uraemic syndrome. Metabolic investigations led to the identification of an inborn error of cobalamin metabolism consisting of defective methylcobalamin biosynthesis, probably cobalamin G, since methionine synthase activity was decreased under standard reducing conditions. Despite treatment, pulmonary hypertension progressively developed and responded to oxygen therapy. Renal involvement evolved to terminal failure and haemodialysis, while pulmonary hypertension was controlled by oxygen therapy. Such clinical manifestations have never been reported in association with a defect of methylcobalamin and thus of methionine biosynthesis. A congenital abnormality of cobalamin metabolism was suspected then confirmed in the presence of typical haematological features associated with unusual clinical manifestations such as progressive renal failure and pulmonary hypertension.
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Jaundice associated with hypertrophic pyloric stenosis was recognised in three patients; previous reports have suggested that this is a possible early manifestation of Gilbert syndrome. Most patients with Gilbert syndrome are homozygous for a (TA)(7)TAA polymorphism in the gene promoter coding for bilirubin glucuronosyltransferase. Two of the reported patients were homozygous for the (TA)(7)TAA polymorphism whereas the third was heterozygous for the same polymorphism. Furthermore, no other factors contributing to jaundice in the three patients were found. These results suggest that jaundice associated with hypertrophic pyloric stenosis is due to molecular defects within the gene promoter.
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Glycogen storage disease type Ia (GSD Ia) is an autosomal recessive condition, caused by a deficiency of hepatic glucose-6-phosphatase (G6Pase) activity. In a consanguineous family originating from northern Africa whose first daughter was affected with GSD Ia, we were able to identify the disease-causing mutation, a cytosine to thymine substitution at nucleotide 326 in exon 2 of the G6Pase gene (R83C). This mutation causes the disappearance of an HgaI site, and is thus easily detectable by restriction enzyme digestion. Both parents were heterozygous for this mutation. During the third pregnancy, fetal genomic DNA was extracted from a chorionic villus biopsy sampled at the 24th week of gestation. Exons 2 of the G6Pase gene were amplified by the polymerase chain reaction followed by HgaI digestion. Fetal DNA analysis indicated that the fetus had received both normal G6Pase alleles. This result was confirmed after birth. DNA analysis is the only reliable method for prenatal diagnosis of GSD Ia.