Daniel Lambert

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.

IL-6, TNF-α and atherosclerosis risk indicators in a healthy family population: the STANISLAS cohort

There are no satisfactory data on circulating concentrations of inflammatory cytokines and their potential relationship with traditional and nontraditional atherosclerosis risk factors in a large healthy young population. The present study was conducted to examine, in 179 healthy families selected from the STANISLAS cohort, the association between interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), C-reactive protein (CRP), orosomucoid, haptoglobin, cell-adhesion molecules (ICAM-1, E-, L- and P-selectin) and lipid parameter concentrations. Age, BMI, white blood cells and tobacco consumption contributed to the variation of IL-6 concentrations. Age and tobacco contributed also to TNF-alpha variation. Taking into account potential covariates, we showed strong positive correlation between IL-6 and both inflammatory markers TNF-alpha and CRP in parents and in offspring (P<0.001). In parents, IL-6 was associated with ICAM-1 and L-selectin (P<0.01), while IL-6 and TNF-alpha predicted E-selectin in offspring only (0.001<P<0.01). Furthermore, IL-6 showed a strong negative relationship with apo A-1 and HDL-cholesterol in females only (P<0.001). This study demonstrated that in a large healthy family population, children included, levels of IL-6 are closely associated with traditional and non-traditional atherosclerosis risk factors. All these data are useful for defining the precise role of cytokines in atherosclerosis mechanisms in physiological conditions.

No association between common polymorphisms in genes of folate and homocysteine metabolism and the risk of Down's syndrome among French mothers

The cause of the non-disjunction leading to trisomy 21 remains unclear. Recent evidence has suggested that 5,10-methylenetetrahydrofolate reductase (MTHFR) and/or methionine synthase reductase (MTRR) might contribute to the maternal risk of trisomy 21. The purpose of the present study was to analyse these findings among the French population and to investigate whether common polymorphisms in genes of the folate and homocysteine pathway, including the MTHFR 677C > T, MTHFR 1298A > C, the methionine synthase (MTR) 2756A > G, the cystathionine beta-synthase (CBS) 844Ins68 and the reduced folate carrier (RFC-1) 80G > A polymorphisms, contribute to the risk of trisomy 21. The risk was studied by analysing independent and combined genotypes in 119 case mothers and 119 control mothers. The MTHFR 677T, MTHFR 1298C, MTR2756G, MTRR66G, CBSIns68+ and the RFC-1 80G allele frequencies were not significantly different among French case mothers, compared with control mothers. The risk of having a child with trisomy 21 did not appear to be linked to polymorphisms in genes associated with folate and homocysteine metabolism.

Biological variations, genetic polymorphisms and familial resemblance of TNF-α and IL-6 concentrations: STANISLAS cohort

Cytokines are involved in the development of several inflammatory diseases and atherosclerosis. Their variations in healthy individuals are not well defined. The aims of this study were: firstly, to identify factors affecting biological variation of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α); secondly, to study their family resemblance; and thirdly, to evaluate the effect of two TNF-α (−308G/A and −238G/A) and two IL-6 polymorphisms (174G/C and −572G/C) on their corresponding circulating levels. A total of 171 healthy families selected from the STANISLAS cohort were studied. Age was negatively related to TNF-α concentrations in offspring only (both sons and daughters). Additionally, IL-6 and TNF-α levels were differently influenced by gender, white blood cells, tobacco consumption, and HDL-cholesterol level. A weak significant familial resemblance for TNF-α concentration was observed in siblings only. There was no significant familial resemblance for IL-6 levels. The TNF-α −308A allele was associated with decreased TNF-α concentrations in both offspring aged less than 18 and males without overweight (BMI<25 kg/m2). Fathers carrying the IL-6 −174CC genotype had higher IL-6 levels than those with the IL-6 −174G allele. Parents with the IL-6 −572GG genotype had higher IL-6 concentrations than the C allele carriers. In this sample of healthy families, plasma levels of IL-6 and TNF-α were differently affected by biological parameters including age, gender and smoking, and the impact of their respective polymorphisms was influenced by gender, age and BMI.

Alcoholic Cirrhosis and Cobalamin Metabolism

The cobalamin status of 27 patients suffering from alcoholic cirrhosis and 20 control subjects was analyzed. Plasma cobalamin (p < 0.005), total corrinoids (p < 0.005) and their analogs (p < 0.05) were all significantly elevated in the cirrhosis patients. These differences were due to increased haptocorrin (HC)-bound corrinoid (p < 0.02), which could be explained by a deficient hepatic clearance of cobalamin bound to HC. The increase in the concentration of true cobalamin was greater than that of its analogs. There were positive correlations between cholestasis (serum alkaline phosphatase) and plasma analog concentrations (p < 0.05), HC-bound cobalamin (p < 0.005) and total corrinoids bound to HC (p < 0.005). The plasma concentrations of the indicators of cobalamin deficiency, homocysteine (p < 0.05) and methylmalonic acid (p < 0.001), were increased, which could indicate poor cellular penetration of vitamin B12 or a defect in the activation of the two vitamin-B12-dependent enzymes.

Identification of vitamin B12 and analogues by high- performance capillary electrophoresis and comparison with high-performance liquid chromatography

Abstract High-performance capillary electrophoresis (HPCE) was compared for the identification and determination of corrinoids (hydroxy-, cyano-, 5′-desoxyadenosyl- and methyl-cobalamin and cyano-cobinamide) with high-performance liquid chromatography (HPLC). The within-run reproducibility of the retention times in HPCE and HPLC were similar (2.4 and 2.2%, respectively). The detection limit in HPCE was 20 μg/ml. HPLC can be used, in combination with radioisotope dilution assay, when very low concentrations (100 pg/ml) have to be determined in biological material. HPCE is more efficient than HPLC for the identification of corrinoids after conversion into the CN-cobalamin and CN-cobinamide forms.

Association between Gly241Arg ICAM-1 gene polymorphism and serum sICAM-1 concentration in the Stanislas cohort

Intracellular adhesion molecule-1 (ICAM-1), a cellular adhesion molecule that mediates the interaction of activated endothelial cells with leukocytes, is involved in various inflammatory and cardiovascular disorders. The relation between these markers and genetic polymorphism, however, remains to be elucidated. The aim of this study is to estimate the effect of a single-base polymorphism at codon 241 in exon 4 of ICAM-1 gene on serum sICAM-1 concentration in a healthy population, taking into account other biological determinants of sICAM-1 level. Serum sICAM-1 levels and the G/R241 polymorphism of the ICAM-1 gene were measured in a large healthy population consisting of 413 children aged 6–21 years and 363 adults aged 38–55 years extracted from the Stanislas cohort. The R241 allele was significantly associated with lower sICAM-1 levels and explained 3.4 and 1.9% of the sICAM-1 variability in children and adults, respectively. A codominant pattern contributed better to the model after adjustment for covariates as the RR homozygote effect was higher than that of the GR heterozygote. Moreover, significant independent associations were found between sICAM-1 and smoking, insulin resistance index (HOMA IR), interleukin-6 level, and alkaline phosphatase and aspartate aminotransferase activities. In conclusion, this study revealed a significant association between the G/R241 ICAM-1 polymorphism and serum sICAM-1 levels, probably due to the impairment in binding of ICAM-1 to leukocyte integrin Mac-1 protein.

Vitamin E and lipoproteins in hyperlipoproteinemia.

The composition of vitamin E in serum and lipoproteins was determined in type I, IIa, IIb, IV and IV hyperlipoproteinemia and in normal subjects. Vitamin E was not specifically associated with any one of the lipoproteins but increased vitamin E levels were observed in VLDL when triacylglycerols level was increased (types IIb and IV); the same observations were noted in LDL when cholesterol level was increased (type IIa).

The Leu554Phe polymorphism in the E-selectin gene is associated with blood pressure in overweight people

BackgroundAssociations between circulating concentrations of E-selectin, blood pressure and obesity, and between the Leu554Phe (L/F554) polymorphism and blood pressure have been documented.ObjectivesTo investigate how the E-selectin L/F554 polymorphism is involved in longitudinal blood pressure chan

Crohn's disease and vitamin B12 metabolism

The concentrations of vitamin B12, its analogs, and the haptocorrin and transcobalamin carriers in 21 patients suffering from Crohns disease and a group of controls (20 adults) were measured. There were no significant differences in the mean values for vitamin B12, total corrinoids (vitamin B12 + analogs), or vitamin B12 or total corrinoids bound to haptocorrin or transcobalamin of the Crohns and control patients. There was a significant increase in the binding capacity of transcobalamin in the Crohns patients compared to the controls (P<0.001), but there was no difference in the binding capacities of haptocorrin. The serum concentrations of the markers of vitamin B12 status, homocysteine and methylmalonic acid, showed an increase (P<0.01) in homocysteine in the Crohns disease patients, but no change in methylmalonic acid. As the hyperhomocysteinemia was associated with normal folate concentrations, there may have been a defect in the activation of the enzyme due to altered intracellular vitamin B12 status.