Association of seven functional polymorphisms of one-carbon metabolic pathway with total plasma homocysteine levels and susceptibility to Parkinson's disease among South Indians

Exploring the complexities of 1C metabolism: implications in aging and neurodegenerative diseases

The intricate interplay of one-carbon metabolism (OCM) with various cellular processes has garnered substantial attention due to its fundamental implications in several biological processes. OCM serves as a pivotal hub for methyl group donation in vital biochemical reactions, influencing DNA methylation, protein synthesis, and redox balance. In the context of aging, OCM dysregulation can contribute to epigenetic modifications and aberrant redox states, accentuating cellular senescence and age-associated pathologies. Furthermore, OCM's intricate involvement in cancer progression is evident through its capacity to provide essential one-carbon units crucial for nucleotide synthesis and DNA methylation, thereby fueling uncontrolled cell proliferation and tumor development. In neurodegenerative disorders like Alzheimer's and Parkinson's, perturbations in OCM pathways are implicated in the dysregulation of neurotransmitter synthesis and mitochondrial dysfunction, contributing to disease pathophysiology. This review underscores the profound impact of OCM in diverse disease contexts, reinforcing the need for a comprehensive understanding of its molecular complexities to pave the way for targeted therapeutic interventions across inflammation, aging and neurodegenerative disorders.

Quantitative and causal analysis for inflammatory genes and the risk of Parkinson's disease

Background

The dysfunction of immune system and inflammation contribute to the Parkinson's disease (PD) pathogenesis. Cytokines, oxidative stress, neurotoxin and metabolism associated enzymes participate in neuroinflammation in PD and the genes involved in them have been reported to be associated with the risk of PD. In our study, we performed a quantitative and causal analysis of the relationship between inflammatory genes and PD risk.

Methods

Standard process was performed for quantitative analysis. Allele model (AM) was used as primary outcome analysis and dominant model (DM) and recessive model (RM) were applied to do the secondary analysis. Then, for those genes significantly associated with the risk of PD, we used the published GWAS summary statistics for Mendelian Randomization (MR) to test the causal analysis between them.

Results

We included 36 variants in 18 genes for final pooled analysis. As a result, IL-6 rs1800795, TNF-α rs1799964, PON1 rs854560, CYP2D6 rs3892097, HLA-DRB rs660895, BST1 rs11931532, CCDC62 rs12817488 polymorphisms were associated with the risk of PD statistically with the ORs ranged from 0.66 to 3.19 while variants in IL-1α, IL-1β, IL-10, MnSOD, NFE2L2, CYP2E1, NOS1, NAT2, ABCB1, HFE and MTHFR were not related to the risk of PD. Besides, we observed that increasing ADP-ribosyl cyclase (coded by BST1) had causal effect on higher PD risk (OR[95%CI] =1.16[1.10-1.22]) while PON1(coded by PON1) shown probably protective effect on PD risk (OR[95%CI] =0.81[0.66-0.99]).

Conclusion

Several polymorphisms from inflammatory genes of IL-6, TNF-α, PON1, CYP2D6, HLA-DRB, BST1, CCDC62 were statistically associated with the susceptibility of PD, and with evidence of causal relationships for ADP-ribosyl cyclase and PON1 on PD risk, which may help understand the mechanisms and pathways underlying PD pathogenesis.

One-carbon metabolism pathway genes and their non-association with the development of amyotrophic lateral sclerosis

Although of unknown etiology, some mechanisms associated with the metabolic cycle of folate are speculated to be related to the genesis of amyotrophic lateral sclerosis (ALS). Thus, the aim of the study was to analyze the role of genetic polymorphisms rs1051266 in SLC19A1 gene and rs1805087 in MTR gene and their associations with ALS development. A case-control study was conducted with 101 individuals with ALS and 119 individuals without diagnosis of neurodegenerative diseases, from the Brazilian central population. The polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism technique. The results showed no statistically significant differences, even when genotypes were analyzed by the dominant, recessive, codominant, and overdominant inheritance models. It was observed a statistical significance relating alcohol consumption with individuals in the case group (p = 0.01). Therefore, the need for more studies to evaluate the influence of genetic variants is highlighted, seeking to provide information on the etiopathogenesis of ALS.

Investigating the causality of metabolites involved in one-carbon metabolism with the risk and age at onset of Parkinson's disease: A two-sample mendelian randomization study

With the aging population and increasing life expectancy, Parkinson's disease (PD), a neurological disorder rapidly increasing in morbidity and mortality, is causing a huge burden on society and the economy. Several studies have suggested that one-carbon metabolites, including homocysteine, vitamin B6, vitamin B12 and folate acid, are associated with PD risk. However, the results remain inconsistent and controversial. Thus, we performed a two-sample Mendelian randomization (MR) study to detect the causality between one-carbon metabolites and PD susceptibility as well as age at PD onset. We collected several genetic variants as instrumental variables from large genome-wide association studies of one-carbon metabolites (homocysteine: N = 14, vitamin B6: N = 1, vitamin B12: N = 10, folate acid: N = 2). We then conducted MR analyses using the inverse variance-weighted (IVW) approach and additional MR-Egger regression, weighted median and MR-pleiotropy residual sum and outlier (MR-PRESSO) methods to further test causality. The results showed no causal association between circulating homocysteine levels and PD risk (p = 0.868) or age at PD onset (p = 0.222) with the IVW method. Meanwhile, similar results were obtained by three complementary analyses. In addition, we did not observe any evidence that the circulating levels of vitamin B6, vitamin B12 and folate acid affected the risk of PD or age at onset of PD. Our findings implied that lowering homocysteine levels through vitamin B6, vitamin B12 or folate acid supplementation may not be clinically helpful in preventing PD or delaying the age at PD onset.

Differences in MTHFR and LRRK2 variant's association with sporadic Parkinson's disease in Mexican Mestizos correlated to Native American ancestry

Parkinson's disease (PD), a common neurodegenerative disorder, has a complex etiology where environmental and genetic factors intervene. While a number of genes and variants have been identified in recent decades as causative or protective agents of this condition, a limited number of studies have been conducted in mixed populations, such as Mexican Mestizos. The historical convergence of two founding groups and three ethnicities, and the increasing north-to-south gradient of Native American ancestry in Mexico resulted in a subpopulation structure with considerable genetic diversity. In this work, we investigate the influence of 21 known susceptibility variants for PD. Our case-control study, with a cohort of 311 Mexican Mestizo subjects, found a significant risk association for the variant rs1491942 in LRRK2. However, when stratification by ancestry was performed, a risk effect for MTHFR rs1801133 was observed only in the group with the highest percentage of European ancestry, and the PD risk effect for LRRK2 rs1491942 was significant in subjects with a higher ratio of Native American ancestry. Meta-analyses of these SNP revealed the effect of LRRK2 rs1491942 to be even more significant than previously described in populations of European descent. Although corroboration is necessary, our findings suggest that polymorphism rs1491942 may be useful as a risk marker of PD in Mexican Mestizos with greater Native American ancestry. The absence of associations with the remaining known risk factors is, in itself, a relevant finding and invites further research into the shared risk factors' role in the pathophysiological mechanisms of this neurodegenerative disorder.

Association Between MTHFR Genetic Polymorphism and Parkinson's Disease Susceptibility: A Meta-analysis

Folate metabolism plays quite a critical role in Parkinson’s disease (PD). Previous published research works have studied the link existing between the folate metabolism genetic polymorphisms and PD susceptibility; nevertheless, the results continue having controversies and inconclusiveness. Accordingly, we carried out the present meta-analysis for the assessment of the potential link between the folate metabolism genetic polymorphisms and the susceptibility to PD. In addition we carried out a literature search in the PubMed, EMBASE, Cochrane Library, and WanFang databases till November 10, 2018. The odds ratios (ORs) with corresponding 95% credible interval (95%CI) were put to use for evaluating the strength of the association of three folate metabolism genetic polymorphism ( C677T, A1298C, and A2756G) with the susceptibility to PD. Each statistical analysis was carried out with the use of STATA 15.0. An aggregate of twenty-one case-control investigations were retrieved, which involved 3,944 PD patients and 4,412 controls. We discovered the existence of no substantial link between the C677T and A1298C polymorphism and PD risk in any genetic framework comparisons. With regard to A2756G polymorphism, we discovered that there was an association between the A2756G genetic polymorphism and an augmented threat of PD in the co-dominant genetic framework (GG vs. AA: OR=1.86, 95%CI=1.02-3.37, P=0.042) and the recessive genetic model (GG vs. GA+AA: OR=1.90, 95%CI=1.06-3.41, P=0.031). To summarize, our research work indicates that the A2756G polymorphism of the folate metabolism gene had an association with an augmented threat of PD. Also, A1298C polymorphisms is unlikely to significantly contribute towards the susceptibility to PD. Further large-scale case-control studies are still required.

Rehydration during exercise prevents the increase of homocysteine concentrations

This study aimed to assess the effect of rehydration during and after acute aerobic submaximal exercise on total homocysteine (tHcy) concentrations and related parameters in physically active adult males. Twenty trained males (29.4 ± 7.9 years old) completed four exercise tests: two without rehydration during exercise (NH1 and NH2), one with rehydration during exercise using water (H1) and one with rehydration during exercise using an isotonic sports drink (H2). After finishing the exercise tests, subjects followed a rehydration protocol for 2 h. Serum tHcy, vitamin B12, folate, creatine and creatinine were analysed before, after and at 2, 6 and 24 h after exercise. Data were analysed with and without correcting for haemoconcentration to assess the changes in tHcy related. The methylenetetrahydrofolate reductase (MTHFR) 677TT genotype was also analysed. THcy (uncorrected by haemoconcentration) increased significantly after exercise (P < 0.05) in the NH1 and NH2 tests [mean increase ± SD: 1.55 ± 0.33 (15.18%) and 1.76 ± 0.25 (17.69%) µmol/L, respectively], while no significant differences were found in the H1 and H2 tests [mean increase: 0.65 (6.29%) and 0.90 (8.69%) μmol/L, respectively]. The increase was partly due to haemoconcentration and partly due to the metabolism underlying acute exercise. THcy concentrations recovered to baseline after 24 h in all tests. In conclusion, adequate rehydration during acute aerobic exercise using either water or a sports drink maintains tHcy concentrations at baseline and for up to 2 h after exercise in physically active male adults and prevents further increases when compared to no rehydration.

Acute exercise alters homocysteine plasma concentration in an intensity-dependent manner due increased methyl flux in liver of rats

PURPOSE

We aimed to determine the effects of different intensities of acute exercise on Hcy plasma levels, and the exercise-induced changes in Hcy liver metabolism.

METHOD

First, thirty-two Wistar rats were randomly submitted to an acute bout of swimming exercise carrying a load of 2% (n=8), 4% (n=8) and 6% (n=8) of their total body weight attached in their tail. Control rats remained rested (n=8). Blood samples were taken from tail vein for plasma S-containing amino acids determination before (Rest) and post, 1, 2, 3, 4, 6, and 10h after acute swimming exercise. Second, 56 exercised rats (4% loads) were euthanized before (Rest) and1, 2, 3, 4, 6, and 10h after acute swimming exercise. Blood and liver samples were collected for amino acids and keys genes involved in the Hcy metabolism assay.

RESULTS

Acute exercise increases (P<0.05) plasma Hcy concentration in an intensity-dependent manner (rest 7.7±0.8; 6% load 13.8±3.6; 4% load 12.2±2.9±and 2% load 10.1±2.6, μmol/L); this increase is transient and does not promote hyperhomocysteinemia (<15μmol/L).Exercise-induced increased plasma Hcywas accompanied by the decreased liver S-adenosylmethionine/S-adenosylhomocysteine ratio and elevated MAT1a mRNA content. Acute exercise also caused elevated mRNA of key enzymes of transsulfuration (CBS) and remethylation (BHMT and the MTRR).

CONCLUSION

Our data provided evidence that acute exercise increases plasma Hcy concentration due to the augmented requirement for methylated compounds that increases liver SAM consumption. Also, Hcy remethylation and transsulfuration are coordinately regulated to maintain methyl balance.

Single Nucleotide Polymorphisms in Key One-Carbon Metabolism Genes and Their Association with Blood Folate and Homocysteine Levels in a Chinese Population in Yunnan

OBJECTIVE

One-carbon metabolism (OCM) is essential for DNA synthesis and methylation. Single nucleotide polymorphisms (SNPs) within OCM genes may affect folic acid (FA) metabolism, disrupt homocysteine (Hcy) homeostasis, and increase the risk of disease. This study investigated the relationship between SNPs in key OCM genes and their association with blood FA and Hcy levels in a healthy population in Yunnan, China.

METHODS

Six SNPs within five key OCM genes (MTHFR C677T, MTHFR A1298C, MS A2756G, MTRR A66G, CBS T833C, and SHMT C1420T) were genotyped in 300 healthy volunteers (148 males and 152 females) using polymerase chain reaction/restriction fragment length polymorphism. Blood folate [serum FA (SFA) and red blood cell folate (RBC FA)] and Hcy levels were determined by chemiluminescence immunoassays and enzymatic assays.

RESULTS

Subjects with the MTHFR 677TT genotype had significantly higher Hcy levels and RBC FA concentrations compared with those harboring the MTHFR 677CC/CT genotypes (p < 0.01). Both Hcy and blood FA concentrations were also increased in subjects with MS 2756AA, as well as those within CBS 833TT, when compared with those with MS 2756AG/GG (p < 0.05) and CBS 833TC/CC (p < 0.05) genotypes, respectively. Subjects harboring the combined genotype of MTHFR 677TT and MS 2756AA had a higher Hcy concentration than those carrying other MTHFR and MS combinations (p = 0.002). Similarly, subjects harboring the combination of CBS 833TT with MTHFR 677TT had higher Hcy concentrations than those harboring other CBS and MTHFR combinations (p = 0.011).

CONCLUSIONS

The genotypes involving the MTHFR C677T, MS A2756G, and CBS T833C polymorphisms, including combinations of these genotypes, were the most important factors associated with blood FA and Hcy levels of the investigated SNPs in the OCM genes.

Neuro-fuzzy model of homocysteine metabolism

In view of well-documented association of hyperhomocysteinaemia with a wide spectrum of diseases and higher incidence of vitamin deficiencies in Indians, we proposed a mathematical model to forecast the role of demographic and genetic variables in influencing homocysteinemetabolism and investigated the influence of life style modulations in controlling homocysteine levels. Total plasma homocysteine levels were measured in fasting samples using reverse phase HPLC. Multiple linear regression (MLR) and neuro-fuzzy models were developed. The MLR model explained 64% variability in homocysteine, while the neurofuzzy model showed higher accuracy in predicting homocysteine with a mean absolute error of 0.00002 μmol/L. Methylene tetrahydrofolate reductase (MTHFR) C677T, 5-methyltetrahydrofolate homocysteine methyltransferase (MTR) A2756G and 5- methyltetrahydrofolate homocysteine methyltransferase reductase (MTRR) A66G were shown to be positively associatiated with homocysteine, while nonvegetarian diet, serine hydroxymethyltransferase 1 (SHMT1) C1420T and TYMS 5'-UTR 28 bp tandem repeat exhibited negative association with homocysteine. The protective role of SHMT1 C1420T was attributed to more H-bonding interactions in the mutant modelled compared to the wild type, as shown through in silico analysis. To conclude, polymorphisms in genes regulating remethylation of homocysteine strongly influence homocysteine levels. The restoration of one-carbon homeostasis by SHMT1 C1420T or increased flux of folate towards remethylation due to TYMS 5'-UTR 28 bp tandem repeat or nonvegetarian diet can lower homocysteine levels.

MTHFR C677T and A1298C polymorphisms may contribute to the risk of Parkinson's disease: A meta-analysis of 19 studies

The 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been reported to be a candidate gene for susceptibility to Parkinson's disease (PD), but results of different studies are conflicting. Here, we conducted a meta-analysis of published case-control studies to evaluate the association between MTHFR C677T and A1298C gene polymorphisms with the risk of PD. Electronic search through PubMed, EmBase, ScienceDirect and Cochrane Library was conducted to identify all relevant studies. A total of 19 studies with 2746 cases and 8967 controls were included. No significant association between MTHFR C677T polymorphism and PD risk was found in the overall population in all five genetic models. In the subgroup analysis stratified by ethnicity, a significant association between MTHFR C677T and PD risk was observed in the dominant model in Caucasians (OR=1.175, 95%CI: 1.008-1.369, P=0.040), but not in Asians. Significant association was found between MTHFR A1298C polymorphism and PD risk in the overall population in the dominant (OR=1.168, 95%CI: 1.008-1.353, P=0.039) and heterozygous model (OR=1.172, 95%CI: 1.004-1.367, P=0.044). But in the subgroup analysis, no association was found between MTHFR A1298C and PD neither in Caucasians nor in Asians. Our meta-analysis suggests that MTHFR C677T polymorphism may be associated with increased PD risk in Caucasians and MTHFR A1298C polymorphism may also increase susceptibility to PD.

MTRR rs326119 polymorphism is associated with plasma concentrations of homocysteine and cobalamin, but not with congenital heart disease or coronary atherosclerosis in Brazilian patients

Background

Differences in the distribution of the MTRR rs326119 polymorphism (c.56 + 781 A > C) between patients with congenital heart disease (CHD) and controls have been described in Chinese individuals. The association is thought to be due to deregulation of homocysteine-cobalamin pathways. This has not been replicated in other populations. The primary objective of this study was to assess the influence of the MTRR rs326119 polymorphism on biochemical parameters of vitamin B12 metabolism, coronary lesions, and congenital heart disease in Brazilian subjects.

Methods

We selected 722 patients with CHD, 1432 patients who underwent coronary angiography, and 156 blood donors. Genotyping for the MTRR polymorphism was evaluated by high-resolution melting analysis, and biochemical tests of vitamin B12 metabolism were measured.

Results

Subjects carrying the AC or CC genotypes had higher homocysteine concentrations (9.7 ± 0.4 μmol/L and 10.1 ± 0.6 μmol/L) and lower cobalamin concentrations (260.5 ± 13.3 pmol/L and 275.6 ± 19.9 pmol/L) compared with the subjects carrying the AA genotype (8.7 ± 0.5 μmol/L and 304.8 ± 14.7 pmol/L), respectively. A multiple linear regression model also identified a significant association between the number of C variant alleles with the concentrations of homocysteine and cobalamin. Nonetheless, the allelic and genotypic distributions for MTRR rs326119 were not associated with CHD or coronary atherosclerosis in the studied samples.

Conclusion

Our findings indicate that the MTRR rs326119 variant might be a genetic marker associated with homocysteine and cobalamin concentrations, but not a strong risk factor for CHD or coronary atherosclerosis in the Brazilian population.

Application of adaptive neuro-fuzzy inference systems (ANFIS) to delineate estradiol, glutathione and homocysteine interactions

The rationale of the current study was to elucidate the contributing factors for the gender-based differences in total plasma homocysteine levels. A total of 413 subjects comprising of 293 men and 120 women were enrolled for the study. Chemiluminescence technology for vitamin B₁₂, folate and total plasma homocysteine; ELISA for estradiol and 8-oxo-2-deoxyguanosine; Ellman's method for total glutathione; and PCR-RFLP analysis for the detection of methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism were employed. No statistically significant differences were observed between the men and women in the distribution of age (p = 0.82), vitamin B₁₂ (p = 0.23), folate (p = 0.36) and MTHFR C677T polymorphism (p = 0.35). However, the total plasma homocysteine levels were higher in men compared to women (28.4 ± 17.9 vs. 20.6 ± 13.6 μmol/L, p < 0.0001). In order to explain this gender differences in homocysteine, adaptive neuro-fuzzy inference systems (ANFIS) were developed to understand trivariate interactions among estradiol, glutathione and homocysteine. In the presence of adequate estradiol levels, inverse association was observed between glutathione and homocysteine. This association is lost when estradiol levels were inadequate. Estradiol was found to quench homocysteine mediated oxidative DNA damage. Irrespective of gender, combined deficiency of vitamin B₁₂ and folate showed positive association with hyperhomocysteinemia and vice versa. Homocysteine reduction in response to vitamin status varied according to gender with men responding to folate and women responding to B₁₂. To conclude, gender-differences in homocysteine are attributable estradiol mediated lowering of homocysteine that prevents inactivation of glutathione mediated oxidative defense in women.

The Effects of Acute Exercise and Exercise Training on Plasma Homocysteine: A Meta-Analysis

Background

Although studies have demonstrated that physical exercise alters homocysteine levels in the blood, meta-analyses of the effects of acute exercise and exercise training on homocysteine blood concentration have not been performed, especially regarding the duration and intensity of exercise, which could affect homocysteine levels differently.

Objective

The aim of this meta-analysis was to ascertain the effects of acute exercise and exercise training on homocysteine levels in the blood.

Method

A review was conducted according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses using the online databases PubMed, SPORTDiscus, and SciELO to identify relevant studies published through June 2015. Review Manager was used to calculate the effect size of acute exercise and exercise training using the change in Hcy plasmaserum concentration from baseline to post-acute exercise and trained vs. sedentary control groups, respectively. Weighted mean differences were calculated using random effect models.

Results

Given the abundance of studies, acute exercise trials were divided into two subgroups according to exercise volume and intensity, whereas the effects of exercise training were analyzed together. Overall, 22 studies with a total of 520 participants indicated increased plasma homocysteine concentration after acute exercise (1.18 μmol/L, 95% CI: 0.71 to 1.65, p < .01). Results of a subgroup analysis indicated that either long-term exercise of low-to-moderate intensity (1.39 μmol/L, 95% CI: 0.9 to 1.89, p < .01) or short-term exercise of high intensity (0.83 μmol/L, 95% CI: 0.19 to 1.40, p < .01) elevated homocysteine levels in the blood. Increased homocysteine induced by exercise was significantly associated with volume of exercise, but not intensity. By contrast, resistance training reduced plasma homocysteine concentration (-1.53 μmol/L, 95% CI: -2.77 to -0.28, p = .02), though aerobic training did not. The cumulative results of the seven studies with a total of 230 participants in exercise training analysis did not demonstrate a significant impact on homocysteine levels in the blood (-0.56 μmol/L, 95% CI: -1.61 to 0.50, p = .23).

Conclusions

Current evidence demonstrates that acute exercise increases homocysteine levels in the blood independent of exercise duration and intensity. Resistance, but not aerobic training decreases plasma homocysteine levels.

Association of the MTHFR rs1801131 and rs1801133 variants in sporadic Parkinson's disease patients

Parkinson's disease (PD) is a common age-dependent neurodegenerative movement disorder related to multiple factors, and genetic factors play an important role in the pathogenesis of PD. Variants in the methylenetetrahydrofolate reductase gene (MTHFR), a gene encoding a folate-dependent enzyme that is involved in homocysteine metabolism, have been reported to be associated with PD. To explore the role of the MTHFR gene in the development of PD in Chinese Han population, we analyzed two MTHFR variants (rs1801131 and rs1801133) in a patient cohort consisting of 512 patients with PD from mainland China and a control cohort consisting of 512 age, gender and ethnicity matched normal subjects. Statistically significant differences in genotypic and allelic frequencies were detected in the MTHFR variant rs1801133 (P=0.022 and 0.007, respectively; odds ratio=0.780, 95% confidence interval=0.651-0.934). In addition, the A-T haplotype of rs1801131-rs1801133 showed a protective role against PD development (P=0.007, odds ratio=0.779, 95% confidence interval=0.650-0.933). Our results suggested that the T allele of rs1801133 variant and A-T haplotype of rs1801131-rs1801133 in the MTHFR gene may decrease the risk of developing PD in Chinese Han population from mainland China.

Multifactor dimensionality reduction analysis to elucidate the cross-talk between one-carbon and xenobiotic metabolic pathways in multi-disease models

Putatively functional polymorphisms of one-carbon and xenobiotic metabolic pathways influence susceptibility for wide spectrum of diseases. The current study was aimed to explore gene-gene interactions among these two metabolic pathways in four diseases i.e. breast cancer, systemic lupus erythematosus (SLE), coronary artery disease (CAD) and Parkinson's disease (PD). Multifactor dimensionality reduction analysis was carried out on four case-control datasets. Cross-talk was observed between one-carbon and xenobiotic pathways in breast cancer (RFC 80 G>A, COMT H108L and TYMS 5'-UTR 28 bp tandem repeat) and SLE (CYP1A1 m1, MTRR 66 A>G and GSTT1). Gene-gene interactions within one-carbon metabolic pathway were observed in CAD (GCPII 1561 C>T, SHMT 1420 C>T and MTHFR 677 C>T) and PD (cSHMT 1420 C>T, MTRR 66 A>G and RFC1 80 G>A). These interaction models showed good predictability of risk for PD (The area under the receiver operating characteristic curve (C) = 0.83) and SLE (C = 0.73); and moderate predictability of risk for breast cancer (C = 0.64) and CAD (C = 0.63). Cross-talk between one-carbon and xenobiotic pathways was observed in diseases with female preponderance. Gene-gene interactions within one-carbon metabolic pathway were observed in diseases with male preponderance.

A pilot study evaluating the contribution of SLC19A1 (RFC-1) 80G>a polymorphism to Alzheimer's disease in Italian Caucasians

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the primary form of dementia in the elderly. Polymorphisms of genes involved in folate metabolism have been frequently suggested as risk factors for sporadic AD. A common c.80G>A polymorphism (rs1051266) in the gene coding for the reduced folate carrier (SLC19A1 gene, commonly known as RFC-1 gene) was investigated as AD risk factor in Asian populations, yielding conflicting results. We screened a Caucasian population of Italian origin composed of 192 sporadic AD patients and 186 healthy matched controls, for the presence of the RFC-1 c.80G>A polymorphism, and searched for correlation with circulating levels of folate, homocysteine, and vitamin B12. No difference in the distribution of allele and genotype frequencies was observed between AD patients and controls. No correlation was observed among the genotypes generated by the RFC-1 c.80G>A polymorphism and circulating levels of folate, homocysteine, and vitamin B12 either in the whole cohort of subjects or after stratification into clinical subtypes. Present results do not support a role for the RFC-1 c.80G>A polymorphism as independent risk factor for sporadic AD in Italian Caucasians.