Independent and Interactive Influences of Environmental UVR, Vitamin D Levels, and Folate Variant MTHFD1-rs2236225 on Homocysteine Levels

Elevated homocysteine (Hcy) levels are a risk factor for vascular diseases. Recently, increases in ultraviolet radiation (UVR) have been linked to decreased Hcy levels. This relationship may be mediated by the status of UVR-responsive vitamins, vitamin D and folate, and/or genetic variants influencing their levels; however, this has yet to be examined. Therefore, the independent and interactive influences of environmental UVR, vitamin D and folate levels and related genetic variants on Hcy levels were examined in an elderly Australian cohort (n = 619). Red blood cell folate, 25-hydroxyvitamin D (25(OH)D), and plasma Hcy levels were determined, and genotyping for 21 folate and vitamin D-related variants was performed. Erythemal dose rate accumulated over six-weeks (6W-EDR) and four-months (4M-EDR) prior to clinics were calculated as a measure of environmental UVR. Multivariate analyses found interactions between 6W-EDR and 25(OH)D levels (pinteraction = 0.002), and 4M-EDR and MTHFD1-rs2236225 (pinteraction = 0.006) in predicting Hcy levels. The association between 6W-EDR and Hcy levels was found only in subjects within lower 25(OH)D quartiles (<33.26 ng/mL), with the association between 4M-EDR and Hcy occurring only in subjects carrying the MTHFD1-rs2236225 variant. 4M-EDR, 6W-EDR, and MTHFD1-rs2236225 were also independent predictors of Hcy. Findings highlight nutrient–environment and gene–environment interactions that could influence the risk of Hcy-related outcomes

Reduced plasma homocysteine levels in elderly Australians following mandatory folic acid fortification – A comparison of two cross-sectional cohorts

© 2017 Objective In 2009, Australia implemented mandatory folic acid fortification in wheat flour for bread-making. The primary aim was to improve folate status in reproductive-aged women to reduce neural tube defect incidence. However, folic acid consumption has consequently increased in all demographics. Blood folate is inversely associated with homocysteine levels, a risk factor for multiple diseases. Therefore, we assessed the impact of mandatory folic acid fortification on homocysteine levels in elderly Australians. Methods Homocysteine and blood folate levels were compared between two elderly cross-sectional cohorts (pre-versus post-mandatory folic acid fortification). Importantly, dietary habits were assessed to evaluate the confounding influence of altered dietary patterns not related to fortification. Results Post-fortification, plasma homocysteine levels (10.6 vs. 14.5 μmol/L) and hyperhomocysteinemia incidence (27.2% vs 56.3%) were significantly reduced, relative to the pre-fortification subjects. This was associated with increased blood folate (red cell: 1243 vs 1066 nmol/L, serum 28.0 vs 23.9 nmol/L), and increased intake of synthetic folic acid (366.8 vs 231.0 DFE/day) but not natural folate (332.7 vs 323.6 DFE/day). Limited other differences were detected in dietary intake patterns between groups. The positive relationship between homocysteine levels and age was abrogated post-fortification (p = 0.3 vs p = 0.0003). Conclusions A potential off-target benefit of mandatory folic acid fortification in Australia was demonstrated. With many countries still considering the merits and consequences of mandatory fortification policies, it is important to unravel the off-target effects including dietary context

Relationship between methylation status of Vitamin D-related genes, Vitamin D levels, and methyl-donor biochemistry

© 2016 The Authors. Published by Elsevier Inc. Vitamin D is known for its role in the regulation of gene expression via the Vitamin D receptor, a nuclear transcription factor. More recently, a role for Vitamin D in regulating DNA methylation has been identified as an additional mechanism of modulation of gene expression. How methylation status influences Vitamin D metabolism and response pathways is not yet clear. Therefore, we aimed to assess the relationship between plasma 25-hydroxycholecalciferol (25(OH)D) and the methylation status of Vitamin D metabolism enzyme genes (CYP2R1, CYP27B1 and CYP24A1) and the Vitamin D receptor gene (VDR). This analysis was conducted in the context of dietary Vitamin D, and background methyl donor related biochemistry, with adjustment for several dietary and lifestyle variables. Percentage methylation at CpG sites was assessed in peripheral blood cells using methylation sensitive and dependent enzymes and qPCR. Standard analytical techniques were used to determine plasma 25(OH)D and homocysteine, and serum folate and B12, with the relationship to methylation status assessed using multi-variable regression analysis. CYP2R1 and VDR methylation were found to be independent predictors of plasma 25(OH)D, when adjusted for Vitamin D intake and other lifestyle variables. CYP24A1 was related to plasma 25(OH)D directly, but not in the context of Vitamin D intake. Methyl-group donor biochemistry was associated with the methylation status of some genes, but did not alter the relationship between methylation and plasma 25(OH)D. Modulation of methylation status of CYP2R1, CYP24A1 and VDR in response to plasma 25(OH)D may be part of feedback loops involved in maintaining Vitamin D homeostasis, and may explain a portion of the variance in plasma 25(OH)D levels in response to intake and sun exposure. Methyl-group donor biochemistry, while a potential independent modulator, did not alter this effect

G80A reduced folate carrier SNP modulates cellular uptake of folate and affords protection against thrombosis via a non homocysteine related mechanism

Dietary folate is absorbed in the jejunum by the 'Reduced Folate Carrier' binding protein. This protein also sequesters extracellular folate for use by many cells in the body. As several biosynthetic pathways require folate for critical life processes, any change in the properties of this protein could lower folate bioavailability, cellular levels of the vitamin, and thus influence health. Since folate lowers thrombogenic homocysteine, we examined the prevalence of a common genetic polymorphism encoding the Reduced Folate Carrier (G80A RFC) to see if it acts as a risk factor for thrombotic vascular disease via an effect on homocysteine disposition in a cohort of 156 patients.The odds ratio indicates a significant protective effect of the mutant A allele against thrombosis: OR = 0.56(95% CI; 0.34-0.92). [chi]2; p = 0.022 (Yates corrected [chi]2; p = 0.031).The polymorphism had no impact on homocysteine, but did increase the level of extracellular to intracellular folate as might be predicted by the biological role of the expressed protein. This, and not homocysteine level, may be what affords protection against thrombosis

Folic acid: An essential nutrient with added health benefits

The story of folate nutrition is one of the most important in contemporary preventive medicine. In order to provide the ultimate answer as to why your children should eat their greens, and clear their plates - read on