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Simonetta Friso

Publications and source records attributed to Simonetta Friso.

At least 19 recordsLinked to original sources
PubMed2006

Hyperhomocysteinemia and mortality after coronary artery bypass grafting.

BACKGROUND: The independent prognostic impact, as well as the possible causal role, of hyperhomocysteinemia (HHcy) in coronary artery disease (CAD) is controversial. No previous study specifically has addressed the relationship between HHcy and mortality after coronary artery bypass grafting (CABG) surgery. The aim of this study is to evaluate the prognostic impact of HHcy after CABG surgery. METHODOLOGY AND PRINCIPAL FINDINGS: We prospectively followed 350 patients who underwent elective CABG between May 1996 and May 1999. At baseline, fasting total homocysteine (tHcy) levels were measured in all participants, and a post-methionine loading (PML) test was performed in 77.7% of them (n = 272). After a median follow-up of 58 months, 33 patients (9.4%) had died, 25 because of cardiovascular events. HHcy, defined by levels higher than the 90th percentile (25.2 micromol/L) of the population's distribution, was significantly associated to total and cardiovascular mortality (P = 0.018 [log-rank test 5.57]; P = 0.002 [log-rank test 9.76], respectively). The PML test had no prognostic value. After multiple adjustment for other univariate predictors by Cox regression, including statin therapy (the most powerful predictor in uni-/multivariate analyses), high-sensitivity C Reactive Protein (hs-CRP) levels, and all known major genetic (MTHFR 677C-->T polymorphism) and non-genetic (B-group vitamin status and renal function) tHcy determinants, HHcy remained an independent prognostic factor for mortality (HRs: 5.02, 95% CIs 1.88 to 13.42, P = 0.001). CONCLUSIONS: HHcy is an important prognostic marker after CABG, independent of modern drug therapy and biomarkers.

Aged↗
PubMed2006

The -1131 T>C and S19W APOA5 gene polymorphisms are associated with high levels of triglycerides and apolipoprotein C-III, but not with coronary artery disease: an angiographic study.

High plasma concentrations of triglycerides (TG) and apolipoprotein C-III (ApoC-III) are well-known risk factors for cardiovascular disease. Two variants of the recently discovered APOA5, 1131 C>T and S19W, have been associated with hypertriglyceridemia, whereas their relation with coronary artery disease (CAD) remains controversial. Nine hundred and thirteen angiografically defined patients (669 CAD and 244 CAD-free) were genotyped for APOA5 -1131 C>T and S19W polymorphisms. Carriership of the APOA5 -1131 C allele was identified, by multiple linear regression models, as a significant independent predictor for both TG (standardized beta-coefficient=0.112; p=0.010) and ApoC-III variability (standardized beta-coefficient=0.113; p=0.013). Similarly, APOA5 19W allele carriership was a significant independent predictor for both TG (standardized beta-coefficient=0.113; p=0.007) and ApoC-III variability (standardized beta-coefficient=0.088; p=0.045). Despite the association with at-risk lipid profile, no significant difference was detected in the distribution of both APOA5 gene polymorphisms between subjects with or without CAD. Moreover, homozygous carriers of the APOC3 -455 C, another TG- and ApoC-III raising variant, showed a significant increased risk for CAD (OR 1.90 with 95% CI 1.002-3.62; p=0.049; by multiple logistic regression). Different genotypes, i.e., APOA5 and APOC3 variants, may lead to similar biochemical phenotypes, namely hypertriglyceridemia, but to contrasting clinical phenotypes such as the presence of angiographically proven CAD.

Adult↗
PubMed2005

Folate supplementation increases genomic DNA methylation in the liver of elder rats.

The availability of folate is implicated as a determinant of DNA methylation, a functionally important feature of DNA. Nevertheless, when this phenomenon has been examined in the rodent model, the effect has not always been observed. Several reasons have been postulated for the inconsistency between studies: the rodent is less dependent on folate as a methyl source than man; juvenile animals, which most studies use, are more resistant to folate depletion than old animals; methods to measure genomic DNA methylation might not be sensitive enough to detect differences. We therefore examined the relationship between folate and genomic DNA methylation in an elder rat model with a newly developed method that can measure genomic DNA methylation sensitively and precisely. Thirty-nine 1-year-old rats were divided into three groups and fed a diet containing 0, 4.5 or 18 mumol folate/kg (folate-deplete, -replete and -supplemented groups, respectively). Rats were killed at 8 and 20 weeks. At both time points, mean liver folate concentrations increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend <0.001) and by 20 weeks hepatic DNA methylation also increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend=0.025). At both time points folate-supplemented rats had significantly increased levels of DNA methylation compared with folate-deplete rats (P<0.05). There was a strong correlation between hepatic folate concentration and genomic DNA methylation in the liver (r 0.48, P=0.004). In the liver of this animal model, dietary folate over a wide range of intakes modulates genomic DNA methylation.

Aging↗
PubMed2005

The MTHFR 1298A>C polymorphism and genomic DNA methylation in human lymphocytes.

Methylenetetrahydrofolate reductase (MTHFR) balances the pool of folate coenzymes in one-carbon metabolism for DNA synthesis and methylation, both implicated in carcinogenesis. Epidemiologic studies have shown that two functional polymorphisms in MTHFR gene, 677C>T and 1298A>C, are related to increased cancer risk. We aimed to analyze lymphocyte DNA from 198 subjects to evaluate the MTHFR 1298A>C polymorphism and folate status affecting genomic DNA methylation as a possible mechanism underlying the relationship between MTHFR polymorphisms and cancer susceptibility. Carriers of the 1298AA wild-type genotype showed lower genomic DNA methylation compared with 1298AC or 1298CC genotypes [3.72 versus 8.59 or 6.79 ng 5-methyl-2'-deoxycytidine (5-mCyt)/microg DNA, P < 0.0001 and P = 0.007, respectively]. When DNA methylation was evaluated according to plasma folate status, only 1298AA with low folate levels revealed diminished DNA methylation (P < 0.0001). Moreover, when the two MTHFR polymorphisms were concomitantly evaluated at the low folate status, DNA methylation was reduced only in 1298AA/677TT compared with 1298AA/677CC (3.11 versus 7.29 ng 5-mCyt/microg DNA, P = 0.001) and 1298CC/677CC genotypes (3.11 versus 7.14 ng 5-mCyt/microg DNA, P = 0.004). However, the high prevalence of 677TT mutants within the 1298AA group (79%) and the similar biochemical features of 1298AA/677CC and 1298CC/677CC combined genotypes suggest that the gene-nutrient interaction affecting DNA methylation in 1298AA is mainly due to the coexistence of the 677TT genotype and that the 1298A>C polymorphism may convey its protective effect not through this interaction but through another pathway in one-carbon metabolism. Further mechanistic studies are warranted to investigate how single polymorphisms as well as MTHFR combined genotypes exert their effect on cancer susceptibility.

Computers↗
PubMed2005

Interactions between folate and aging for carcinogenesis.

Inadequate folate intake and aging are each strongly implicated as important risk factors for certain cancers. Since both folate depletion and aging are strongly associated with hyperhomocysteinemia, genomic DNA hypomethylation, and increased uracil misincorporation into DNA, it appears that each of them enhances carcinogenesis by inducing a derangement of one-carbon metabolism that supplies one-carbons to biological methylation reactions and nucleotide synthesis. Recent studies have demonstrated that inadequate dietary folate and aging may interact and synergistically disturb the normal homeostasis of one-carbon metabolism, thereby provoking subsequent biochemical and molecular aberrations, including alterations in critical gene expression related to carcinogenesis. These studies have further indicated that modest folate supplementation may reverse or partially ameliorate those adverse effects induced by folate depletion and aging.

Aging↗
PubMed2005

The potential cocarcinogenic effect of vitamin B12 deficiency.

Since vitamin B12 serves as a cofactor in the synthesis of methyl precursors for biological methylation and enables methylfolate to be recycled for nucleotide synthesis, B12 deficiency has been known to induce hyperhomocysteinemia and inadequate DNA synthesis, along with "methylfolate trap". Even though depletion of B12, a common B-vitamin deficiency in the elderly, has not often been invoked as a causative factor in carcinogenesis, a recent animal study demonstrated that a B12-deficient diet, which was of insufficient severity to cause anemia or illness, disturbed normal homeostasis of one-carbon metabolism in the colonic mucosa and resulted in diminished genomic DNA methylation and increased uracil misincorporation in DNA, both of which are purported mechanisms for one-carbon metabolism-related colonic carcinogenesis.

Animals↗
PubMed2005

Gene-nutrient interactions in one-carbon metabolism.

Advances in molecular biology greatly contributed, in the past decades, to a deeper understanding of the role of gene function in disease development. Environmental as well as nutritional factors are now well acknowledged to interact with the individual genetic background for the development of several diseases, including cancer, cardiovascular disease, and neurodegenerative diseases. The precise mechanisms of such gene-nutrient interactions, however, are not fully elucidated yet. Many micronutrients and vitamins are crucial in regulating mechanisms of DNA metabolism. Indeed, folate has been most extensively investigated for its unique function as mediator for the transfer of one-carbon moieties for nucleotide synthesis/repair and biological methylation. Cell culture, animal, and human studies, clearly demonstrated that folate deficiency induces disruption of DNA synthesis/repair pathways as well as DNA methylation anomalies. Remarkably, a gene-nutrient interaction between folate status and a polymorphism in methylenetetrahydrofolate reductase gene has been reported to modulate genomic DNA methylation. This observation suggests that the interaction between a nutritional status and a mutant genotype may modulate gene expression through DNA methylation, especially when such polymorphism affects a key enzyme in one-carbon metabolism and limits the methyl supply. DNA methylation, both genome-wide and gene-specific, is of particular interest for the study of aging, cancer, and other pathologic conditions, because it affects gene expression without permanent alterations in the DNA sequence such as mutations or allele deletions. Understanding the patterns of DNA methylation through the interaction with nutrients is a critical issue, not only to provide pathophysiological explanations of a disease state, but also to identify individuals at-risk to conduct targeted diet-based interventions.

Animals↗
PubMed2004

Apolipoprotein C-III, n-3 polyunsaturated fatty acids, and "insulin-resistant" T-455C APOC3 gene polymorphism in heart disease patients: example of gene-diet interaction.

BACKGROUND: Apolipoprotein C-III (apo C-III) is a marker of cardiovascular disease risk associated with triglyceride (TG)-rich lipoproteins. The T-455C polymorphism in the insulin-responsive element of the APOC3 gene influences TG and apo C-III concentrations. Long-chain n-3 polyunsaturated fatty acids (PUFAs) contained in fish have well-known apo C-III-lowering properties. METHODS: We investigated the possibility of an interactive effect between the APOC3 gene variant and erythrocyte n-3 PUFAs, suitable markers of dietary intake of fatty acids, on apo C-III concentrations in a population of 848 heart disease patients who had coronary angiography. RESULTS: In the population as a whole, apo C-III concentrations were significantly inversely correlated with total erythrocyte PUFAs, but the correlation was not significant when only -455CC homozygous individuals were taken into account. In the total population and in subgroups with the -455TT and -455CT genotypes, the relative proportions of individuals presenting with increased apo C-III (i.e., above the 75th percentile value calculated on the entire population after exclusion of individuals taking lipids-lowering medications) decreased progressively as the n-3 PUFA and docosahexaenoic acid concentrations increased. The opposite situation was observed in the homozygous -455CC subgroup, in whom increasing erythrocyte n-3 PUFA and docosahexaenoic acid concentrations were associated with higher proportions of individuals with high apo C-III. A formal interactive effect between genotype and n-3 PUFAs was confirmed even after adjustment for possible confounding variables [age, sex, body mass index, smoking, coronary artery disease (CAD)/CAD-free status, or use of lipid-lowering medications] by logistic models. CONCLUSION: Patients homozygous for the -455C APOC3 variant are poorly responsive to the apo C-III-lowering effects of n-3 PUFAs.

Apolipoprotein C-III↗
PubMed2004

Low plasma vitamin B-6 concentrations and modulation of coronary artery disease risk.

BACKGROUND: Low concentrations of pyridoxal-5'-phosphate (PLP), the active metabolite of vitamin B-6, are associated with high C-reactive protein (CRP) concentrations. Both low PLP and elevated inflammatory markers, such as high-sensitivity CRP (hs-CRP) and fibrinogen, are related to higher risk of coronary artery disease (CAD). OBJECTIVES: The objectives were to evaluate the relation between PLP and acute-phase reactants in affecting CAD risk and to estimate the risk of CAD related to low plasma PLP, either alone or in combination with high concentrations of acute-phase reactants and other classic risk factors for CAD. DESIGN: A case-control study was conducted with 742 participants: 475 with severe multivessel CAD and 267 free from coronary atherosclerosis (CAD-free). We measured plasma PLP, fibrinogen, hs-CRP, and serum lipid concentrations and all major biochemical CAD risk factors, including total homocysteine. RESULTS: A significant, inverse, graded relation was observed between PLP and both hs-CRP and fibrinogen (P < 0.001). The prevalence of PLP concentrations in the lower half of the population (<50th percentile: 36.3 nmol/L) was significantly higher among CAD patients than among CAD-free subjects (P < 0.001). The odds ratio for CAD risk related to low PLP concentrations after adjustments for the major classic CAD risk factors, including hs-CRP and fibrinogen, was 1.89 (95% CI: 1.18, 3.03; P = 0.008). The CAD risk as a result of low PLP was additive when considered in combination with elevated hs-CRP concentrations or with an increased ratio of LDL to HDL. CONCLUSION: Low plasma PLP concentrations are inversely related to major markers of inflammation and independently associated with increased CAD risk.

Acute-Phase Proteins↗
PubMed2004

Vitamin B-12 deficiency induces anomalies of base substitution and methylation in the DNA of rat colonic epithelium.

Derangements of one-carbon metabolism can directly affect the integrity of the genome by producing inappropriate uracil insertion into DNA and by altering patterns of DNA methylation. Vitamin B-12, a one-carbon nutrient, serves as a cofactor in the synthesis of precursors of biological methylation and in nucleotide synthesis. We therefore examined whether vitamin B-12 deficiency can induce these molecular anomalies in the colonic mucosa of rats. Weanling male Sprague-Dawley rats (n = 30) were divided into 2 groups and fed either a vitamin B-12-deficient diet or a similar diet containing adequate amounts of the vitamin. Rats from each group were killed at 6 and 10 wk. Uracil misincorporation into DNA was measured by GC/MS and genomic DNA methylation was measured by LC/MS. Plasma vitamin B-12 concentrations in deficient rats were below detectable limits at 6 and 10 wk; in control rats, concentrations were 0.46 +/- 0.07 and 0.42 +/- 0.10 nmol/L at those times. Although the colon total folate concentration did not differ between the groups, the proportion that was methylfolate was marginally greater in the deficient rats at 10 wk (P = 0.05) compared with control, consistent with the "methylfolate trap" that develops during vitamin B-12 deficiency. After 10 wk, the colonic DNA of the deficient rats displayed a 35% decrease in genomic methylation and a 105% increase in uracil incorporation (P < 0.05). This vitamin B-12-deficient diet, which was of insufficient severity to cause anemia or illness, created aberrations in both base substitution and methylation of colonic DNA, which might increase susceptibility to carcinogenesis.

Animals↗
PubMed2004

Influence of polymorphisms in the factor VII gene promoter on activated factor VII levels and on the risk of myocardial infarction in advanced coronary atherosclerosis.

In this study, we investigate the influence of three factor VII (FVII) gene polymorphisms on activated FVII levels (FVIIa), and also on the risk of myocardial infarction (MI) in patients with advanced coronary atherosclerotic disease (CAD). The -323A2 allele in the promoter is known to be associated with low FVII levels, and has been suggested to protect against MI in some studies. The -402GA promoter polymorphism, that in vitro has been associated with having opposite effect, is less well studied clinically. For this study, plasma FVIIa levels and three FVII gene polymorphisms were assessed in 934 subjects of both sexes, all with an angiographic documentation of coronary vessels. Our results show that two promoter polymorphisms, plasma cholesterol, and gender, were significant predictors of FVIIa levels. The -402A allele was associated to a significant increase of FVIIa levels in males (by 19.2%). In a selected clinical model including the patients with severe CAD, with or without a thrombotic complication (MI), male carriers of the -402A had an increased risk of MI (OR=1.79; 95% CI 1.15-2.80). The -323A2 allele was associated to a significant decrease in FVIIa (by 36.02% in males, and 39.7% in females). Male carriers of the -323A2 were protected from MI (OR=0.6; 95% CI 0.39-0.94), but only after correction for the confounding effect of combined heterozygosity for the promoter polymorphisms. We can conclude that FVII gene polymorphisms with an opposite effect on FVIIa levels may modulate the risk of MI in males with advanced CAD. This study highlights a "within-gene" interaction, and the need to explore polymorphisms in candidate gene(s) in detail.

Case-Control Studies↗
PubMed2003

Apolipoprotein C-III, metabolic syndrome, and risk of coronary artery disease.

Apolipoprotein C-III (apoC-III) is a marker of triglyceride (TG)-rich lipoproteins, which are often increased in metabolic syndrome (MS). The T-455C polymorphism in the insulin-responsive element of the APOC3 gene influences TG and apoC-III levels. To evaluate the contribution of apoC-III levels and T-455C polymorphisms in the coronary artery disease (CAD) risk of MS patients, we studied 873 patients, 549 with CAD and 251 with normal coronary arteries. Patients were classified also as having or not having MS (MS, n = 270; MS-free, n = 603). Lipids, insulin, apolipoprotein levels, and APOC3 T-455C genotypes were evaluated. ApoC-III levels were significantly increased in MS patients, and the probability of having MS was correlated with increasing quartiles of apoC-III levels. MS patients with CAD had significantly higher apoC-III levels than did CAD-free MS patients. The carriership for the -455C variant multiplied the probability of CAD in MS in an allele-specific way and was associated with increased apoC-III and TG levels. Obesity was less frequent in MS carriers of the -455C allele than in MS noncarriers (21.6% vs. 34.8%, P < 0.05). In conclusion, apoC-III-rich lipoprotein metabolism and the APOC3 polymorphism have relevant impacts on the CAD risk of MS patents.

Adult↗
PubMed2003

Age and gender affect the relation between methylenetetrahydrofolate reductase C677T genotype and fasting plasma homocysteine concentrations in the Framingham Offspring Study Cohort.

The C677T variant of methylenetetrahydrofolate reductase (MTHFR), a key enzyme in the remethylation of homocysteine to methionine, is a frequent genetic cause of mild hyperhomocysteinemia among individuals with low folate status. However, little is known about the influence of subject characteristics, such as age and sex, on the relation between the C677T MTHFR polymorphism and fasting plasma total homocysteine (tHcy) concentrations. The aim of the present study was to explore the influence of age and gender, together with folate status, on the association between the C677T polymorphism and tHcy concentrations. The C677T genotype was determined for 1820 participants from the fifth examination of the Framingham Offspring Study. Mean age of the participants was 56 y (range 28-82 y). The allelic distribution was not different from the Hardy-Weinberg equilibrium, with a TT frequency comparable in men and women (14%). Geometric mean tHcy was 15% higher in men than in women (P < 0.001), and women had significantly higher plasma folate levels (P < 0.001). Geometric mean tHcy was significantly higher in TT participants (P = 0.001) than in participants with the CC and CT genotypes among those with plasma folate <12.5 nmol/L, but not among those with higher folate status. Because of a significant age and sex interaction (P = 0.02), we further stratified the low folate group by age and sex, and observed that the association between genotype and tHcy was confined to men <55 y old (P < 0.001). Our results suggest that age and sex modify the contribution of the MTHFR C677T mutation to fasting tHcy concentrations.

Adult↗
PubMed2003

Biochemical and molecular aberrations in the rat colon due to folate depletion are age-specific.

Elder adulthood and diminished folate status are each associated with an enhanced risk of colorectal carcinogenesis. We therefore examined whether these two factors are mechanistically related. Weanling male Sprague-Dawley rats (n = 44) and 1-y-old rats (n = 44) were each divided into three groups and fed diets containing 0, 4.5 or 18 micro mol folic acid/kg (deplete, replete and supplemented groups, respectively). Rats were killed at 0, 8 and 20 wk. The folate concentrations, the distribution of the different coenzymatic forms of folate, uracil incorporation into DNA and genomic DNA methylation were measured in the colonic mucosa. Folate-deplete and folate-replete elder rats had 30-45% lower colonic folate concentrations than young rats. Furthermore, 5-methyltetrahydrofolate was uniformly depleted in colons of the elder, folate-deplete rats, whereas this depletion occurred in only a minority of the younger rats. By the end of the experiment, the folate-deplete and folate-replete elder rats had approximately 50% more uracil incorporated into their colonic DNA than the corresponding young groups (P < 0.05). In elder rats, this uracil misincorporation was incremental across the three diet groups (P-test for trend < 0.05), whereas no excess uracil incorporation was observed in young rats. Neither age nor dietary folate affected genomic DNA methylation in the colon. In conclusion, the colon of elder rats is more susceptible to biochemical and molecular consequences of folate depletion than that of young rats. However, folate supplementation is as effective at sustaining adequate colonic folate status in elder rats as it is in the young.

Aging↗
PubMed2003

The interaction between MTHFR 677 C-->T genotype and folate status is a determinant of coronary atherosclerosis risk.

The 677 C-->T polymorphism in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene interacts with folate status in determining elevated total plasma levels of homocysteine, a risk factor for coronary atherosclerotic disease (CAD). The present study had the following goals: 1) to define the 677 C-->T genotype-specific threshold values of both plasma and RBC folate, associated with hyperhomocysteinemia (>15 micro mol/L); and 2) to determine the risk of CAD among subjects with levels of folate below the genotype-specific threshold considered at risk for hyperhomocysteinemia. We examined 655 subjects, with (433) or without (222) angiographically documented CAD. The MTHFR 677 C-->T genotype-specific threshold values of plasma folate corresponded to the 40th, 30th and 10th percentile in the TT, CT and CC genotype, respectively. A multivariate logistic regression analysis showed that the risk of CAD among subjects with plasma folate levels below the genotype-specific thresholds was 1.6 (95% CI, 1.04-2.46). Similar results were obtained when RBC folate was considered as a measure of folate status (odds ratio = 1.8, 95% CI, 1.03-3.15). A gene-nutrient interaction that defines a higher risk for CAD is determined by folate levels below specific thresholds, which differ depending on the MTHFR 677 C-->T genotype.

Base Sequence↗
PubMed2002

A method to assess genomic DNA methylation using high-performance liquid chromatography/electrospray ionization mass spectrometry.

Eukaryotic DNA is methylated at some cytosine residues, and this epigenetic feature performs critical functions. We developed a method for quantitative determination of 5-methyl-2'-deoxycytidine in human DNA using liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The DNA was enzymatically hydrolyzed by sequential digestion with three enzymes. DNA hydrolyzates were subsequently separated by reversed-phase high-performance liquid chromatography in isocratic mode. The four major DNA bases and 5-methyl-2'-deoxycytidine were resolved and eluted in 13 min. Identification of 2'-deoxycytidine and 5-methyl-2'-deoxycytidine was obtained by combined diode array UV spectra analysis and mass spectra of chromatographic peaks. The isotopomers [15N3]-2'-deoxycytidine and (methyl-d3,ring-6-d1)-5-methyl-2'-deoxycytidine were used as internal standards. Ions of m/z 126 and 130 were used to detect 5-methyl-2'-deoxycytidine and its isotopomer, and ions of m/z 112 and 115 were used to detect 2'-deoxycytidine and its stable isotopomer, respectively. The DNA methylation status was calculated on the basis of the amount of 5-methyl-2'-deoxycytidine per microgram of DNA with percent relative standard deviations (%RSD) for a method precision of 7.1 (within-day) and 5.7 (day-to-day). This method also allows the measurement of 5-methyl-2'-deoxycytidine expressed as a percentage of total deoxycytidine residues in genomic DNA with %RSD for method precision of 1.9 (within-day) and 1.7 (day-to-day). This LC/MS method for quantitative determination of genomic DNA methylation status is rapid, sensitive, selective, and precise.

Chromatography, High Pressure Liquid↗
PubMed2002

A common mutation in the 5,10-methylenetetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status.

DNA methylation, an essential epigenetic feature of DNA that modulates gene expression and genomic integrity, is catalyzed by methyltransferases that use the universal methyl donor S-adenosyl-l-methionine. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), the methyl donor for synthesis of methionine from homocysteine and precursor of S-adenosyl-l-methionine. In the present study we sought to determine the effect of folate status on genomic DNA methylation with an emphasis on the interaction with the common C677T mutation in the MTHFR gene. A liquid chromatography/MS method for the analysis of nucleotide bases was used to assess genomic DNA methylation in peripheral blood mononuclear cell DNA from 105 subjects homozygous for this mutation (T/T) and 187 homozygous for the wild-type (C/C) MTHFR genotype. The results show that genomic DNA methylation directly correlates with folate status and inversely with plasma homocysteine (tHcy) levels (P < 0.01). T/T genotypes had a diminished level of DNA methylation compared with those with the C/C wild-type (32.23 vs.62.24 ng 5-methylcytosine/microg DNA, P < 0.0001). When analyzed according to folate status, however, only the T/T subjects with low levels of folate accounted for the diminished DNA methylation (P < 0.0001). Moreover, in T/T subjects DNA methylation status correlated with the methylated proportion of red blood cell folate and was inversely related to the formylated proportion of red blood cell folates (P < 0.03) that is known to be solely represented in those individuals. These results indicate that the MTHFR C677T polymorphism influences DNA methylation status through an interaction with folate status.

Adult↗