Improving biological relevancy of transcriptional biomarkers experiments by applying the MIQE guidelines to pre-clinical and clinical trials.

The "Minimum Information for the Publication of qPCR Experiments" (MIQE [3]) guidelines are very much targeted at basic research experiments and have to our knowledge not been applied to qPCR assays carried out in the context of clinical trials. This report details the use of the MIQE qPCR app for iPhone (App Store, Apple) to assess the MIQE compliance of one clinical and five pre-clinical trials. This resulted in the need to include 14 modifications that make the guidelines more relevant for the assessment of this special type of application. We also discuss the need for flexibility, since while some parameters increase experimental quality, they also require more reagents and more time, which is not always feasible in a clinical setting.

[One carbon metabolism and trisomy 21: analysis of the genetic polymorphism]. / Métabolisme des substrats monocarbonés et trisomie 21: analyse de l'impact des polymorphismes génétiques.

Trisomy 21 is the most common chromosome abnormality characterized by the presence of three copies of chromosome 21 in the genome. The clinical disorder attributed to trisomy 21 is Down syndrome. Patients with Down syndrome are heterogeneous in their phenotypic expression. Due to the location of the cystathionine b-synthase gene on chromosome 21, and its involvement in one carbon metabolism, homocysteine levels have been found to be decreased in children with Down syndrome. The study of the regulation of one carbon metabolism in Down syndrome becomes important in light of possible normalization of the metabolic imbalance and the detection of increased sensitivity to therapeutic interventions. Thus, the importance of evaluating single nucleotide polymorphisms in genes involved in one carbon metabolism need to be addressed in individuals with trisomy 21. This review offers an analysis of the impact of these polymorphisms in Down syndrome and their possible implications for phenotypic heterogeneity.

Detection of moderate hyperhomocysteinemia: comparison of the Abbott fluorescence polarization immunoassay with the Bio-Rad and SBD-F high-performance liquid chromatographic assays.

The importance of accurate methods for homocysteine measurement has been emphasized. We compared the results obtained with the most commonly used high-performance liquid chromatography (HPLC) assay, and two recently commercially available methods: another HPLC and a fluorescence polarization immunoassay, in plasmas from normo- or hyperhomocysteinemic patients. A significant agreement between the different methods in classifying the results as hyper or normal-homocysteinemia was observed. However, a significant difference between the results was found. Standardization is urgently necessary to improve the concordance of homocysteine determination.

Homocysteine metabolism in children with Down syndrome: in vitro modulation.

The gene for cystathionine beta-synthase (CBS) is located on chromosome 21 and is overexpressed in children with Down syndrome (DS), or trisomy 21. The dual purpose of the present study was to evaluate the impact of overexpression of the CBS gene on homocysteine metabolism in children with DS and to determine whether the supplementation of trisomy 21 lymphoblasts in vitro with selected nutrients would shift the genetically induced metabolic imbalance. Plasma samples were obtained from 42 children with karyotypically confirmed full trisomy 21 and from 36 normal siblings (mean age 7.4 years). Metabolites involved in homocysteine metabolism were measured and compared to those of normal siblings used as controls. Lymphocyte DNA methylation status was determined as a functional endpoint. The results indicated that plasma levels of homocysteine, methionine, S-adenosylhomocysteine, and S-adenosylmethionine were all significantly decreased in children with DS and that their lymphocyte DNA was hypermethylated relative to that in normal siblings. Plasma levels of cystathionine and cysteine were significantly increased, consistent with an increase in CBS activity. Plasma glutathione levels were significantly reduced in the children with DS and may reflect an increase in oxidative stress due to the overexpression of the superoxide dismutase gene, also located on chromosome 21. The addition of methionine, folinic acid, methyl-B(12), thymidine, or dimethylglycine to the cultured trisomy 21 lymphoblastoid cells improved the metabolic profile in vitro. The increased activity of CBS in children with DS significantly alters homocysteine metabolism such that the folate-dependent resynthesis of methionine is compromised. The decreased availability of homocysteine promotes the well-established "folate trap," creating a functional folate deficiency that may contribute to the metabolic pathology of this complex genetic disorder.

A polymorphism (80G->A) in the reduced folate carrier gene and its associations with folate status and homocysteinemia.

5-methyltetrahydrofolate is the predominant form of folate in plasma. It may be the preferred substrate for transport via the reduced-folate carrier (RFC). We isolated a cDNA for the reduced folate carrier (RFC-1) from human skin fibroblasts. A common polymorphism at position 80 in exon 2 of RFC-1 was identified. This polymorphism changes a guanine (G) to an adenine (A), abolishing a CfoI restriction site. Using genomic DNA samples from 169 healthy subjects, we identified 27.1% GG homozygotes, 21.9% AA homozygotes, and 50.9% GA heterozygotes. We explored the impact of this polymorphism, separately and in combination with the 677C->T polymorphism in the methylenetetrahydrofolate reductase gene, on folate status and total homocysteine levels. We found a moderate, but significant, increase in total homocysteine levels in doubly homozygous 80GG/677TT subjects as compared to 80GG/677CC (P = 0.01) or 80GG/677CT (P = 0.04) subjects. In addition, individuals who were 80AA/677CT had higher plasma folate levels than those who were 80GG/677CT (P = 0.02).

The effect of 677C-->T and 1298A-->C mutations on plasma homocysteine and 5,10-methylenetetrahydrofolate reductase activity in healthy subjects.

We have studied the effect of common mutations (677C-->T and 1298A-->C) of the methylenetetrahydrofolate reductase (MTHFR) gene in sixty-six healthy French subjects, aged 27-47 years. Serum folate, vitamin B12, and plasma total homocysteine were measured as well as the specific activity of MTHFR in lymphocytes. The frequency of subjects homozygous for the 677TT genotype was 18%, and that of those homozygous for the 1298CC genotype was 12.5%. The frequency of individuals heterozygous for both mutations was 23.5%. The 1298A-->C mutation was associated with decreased MTHFR specific activity in subjects with both 677CC and 677CT genotypes. This activity was 60% for the 677CC/1298AC genotype and 52% for the 677CC/1298CC genotype when compared with the MTHFR specific activity of the 677CC/1298AA genotype. Heterozygotes for both mutations (677CT/1298AC genotype) had 36% of the reference specific activity. Although homocysteine levels in 677TT and 1298CC genotype subjects were higher than for other genotypes, no significant differences were observed among different genotypes. This may be due to high serum folate level in our samples, and suggests that folate therapy may be useful to prevent hyperhomocysteinaemia in homozygous mutant subjects.

5,10-methylenetetrahydrofolate reductase common mutations, folate status and plasma homocysteine in healthy French adults of the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI.MAX) cohort.

The 677cytosine mutation identified in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been frequently associated with an elevated plasma homocysteine concentration. The aim of the present study was to determine the impact of this MTHFR common mutation on plasma and erythrocyte folate (RCF) and plasma total homocysteine (tHcy) concentrations in healthy French adults. A cohort of 291 subjects living in the Paris area and participating in the Supplementation en Vitamines et Mineraux Antioxydants (SU.VI.MAX) study were analysed to assess the impact of MTHFR polymorphism 677C-->T on folate status and plasma tHcy concentration. The frequency of the mutant homozygote for 677C-->T polymorphism (677TT genotype) in the present cohort was 16.8%. There were significant differences in plasma tHcy between 677CC, 677CT and 677TT genotype groups. The RCF concentrations were significantly different between each genotype, the lowest levels being associated with the 677TT genotype. When segregated by gender, no differences in tHcy between homozygous 677TT, heterozygous 677CT and wild-type 677CC genotype groups in women were observed. The fasting tHcy in women was unrelated to the 677C-->T mutation. However, tHcy was significantly increased in men with the homozygous 677TT genotype. We also analysed the possible implication of a second new MTHFR polymorphism (1298A-->C) in subjects with mild hyperhomocysteinaemia (4th quartile of homocysteinaemia; tHcy >11.1 micromol/l). The polymorphism 1298A-->C did not have a notable effect on tHcy or on the RCF levels. Our observations confirm a relatively high frequency of the 677TT genotype in the French population. Women with this genotype did not show the same increase in tHcy observed in men. In the present study dietary folate intake was not measured. Thus, the interaction of dietary folate with the MTHFR genotype in the French population needs further study.

[Molecular genetics of the remethylation of homocysteine]. / Génétique moléculaire de la reméthylation de l'homocystéine.

In plasma of mothers with a child affected with a neural tube defect plasma homocysteine is often elevated, and attributed to a reduced folate-dependent homocysteine remethylation. There is strong evidence that folic acid prevents fasting moderate hyperhomocysteinemia. The pathophysiology of neural tube defect and interactions between genetic and nutritional factors that determine plasma homocysteine levels remain poorly understood. Investigations on genetic causes of moderate hyperhomocysteinemia are in progress. This mini-review focuses on molecular genetic knowledge of folate-dependent homocysteine remethylation in neural tube defect.

[Deregulation of homocysteine metabolism and consequences for the vascular system]. / Dérégulation du métabolisme de l'homocystéine et conséquences pour le système vasculaire.

The link between vascular disease and elevated homocysteine levels has been recognized for more than 30 years, and association with moderately elevated levels has been suspected for 20 years. Homocysteine is a sulfhydryl-containing amino acid that is formed by the demethylation of methionine. It is normally catalysed to cystathionine by cystathionine beta-synthase a pyridoxal phosphate-dependent enzyme. Homocysteine is also remethylated to methionine by methionine synthase, a vitamin B12 dependent enzyme and by methylenetetrahydrofolate reductase. Environmental factors such as folate, or vitamin B12, or vitamin B6 deficiencies and genetic defects such as cystathionine beta-synthase or abnormality of methylene-tetrahydrofolate reductase or some vitamin B12 metabolism defects may contribute to increasing plasma homocysteine levels. Normal fasting levels of homocysteine lie within the range 6-16 mumol/l. Apart from differences in assay methods, age, sex and nutritional status may affect the plasma levels. Though it is now well known that homocysteine is an independent risk factor for premature vascular disease, the pathogenesis of homocysteine-induced vascular damage is, for the most part, unknown. It may be multifactorial, including direct homocysteine damage to the endothelium, an enhanced low-density lipoprotein peroxidation, an increase of platelet thromboxane A2, or a decrease of protein C activation.

[Effects of treatments (heat and fermentation by Rhizopus oligosporus sp-T3) of sweet white lupin seeds on certain factors of its nutritional use]. / Effets des traitements (chauffage et fermentation par Rhizopus oligosporus sp-T3) de la graine de lupin blanc doux sur certains facteurs de son utilisation nutritionnelle.

For improving the nutritional value and functional properties of sweet white lupin (SWL), a solid fermentation process using Rhizopus oligosporus was developed for the preparation of lupin products. A comparison of the effects of soaking + thermal treatment and fermentation was made from 3 lupin products: non-treated lupin seeds (SWLnt), heated lupin seeds (steamed at 100 degrees C for 30 min) (SWLh), and fermented lupin products (SWLf) from SWLh on chemical characteristics and protein efficiency ratio (PER) in rats. The major effect of soaking and thermal treatment is a loss of protein solubility and available lysine (from 3.02 +/- 0.18 g/16 g N to 2.3 +/- 0.25). Fermentation leads to a modification, of amino acid composition and to an increase in available lysine compared to heating (2.90 +/- 0.12 g/16 g N). The nutritional quality of SWLnt is low (PER = 0.83 +/- 0.09), thermal treatment decreases it (0.58 +/- 0.18) and fermentation compensates heating effect (0.74 +/- 0.25). It is suggested that the modifications of nutritional quality depends on the availability of lysine rather than on the variations of the levels of other amino acids.