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

Methylation diet and methyl group genetics in risk for adenomatous polyp occurrence

PurposeThe aim of this study is to explore whether a methylation diet influences risk for adenomatous polyps (AP) either independently, or interactively with one-carbon metabolism-dependent gene variants, and whether such a diet modifies blood homocysteine, a biochemical phenotype closely related to the phenomenon of methylation.Methods249 subjects were examined using selective fluorescence, PCR and food frequency questionnaire to determine homocysteine, nine methylation-related gene polymorphisms, dietary methionine, 5-methyltetrahydrofolate, vitamins B6 and B12.Results1). Both dietary methionine and 5-methyltetrahydrofolate intake are significantly associated with plasma homocysteine. 2). Dietary methionine is related to AP risk in 2R3R-TS wildtype subjects, while dietary B12 is similarly related to this phenotype in individuals heterozygous for C1420T-SHMT, A2756G-MS and 844ins68-CBS, and in those recessive for 2R3R-TS. 3). Dietary methionine has a marginal influence on plasma homocysteine level in C1420T-SHMT heterozygotes, while B6 exhibits the same effect on homocysteine in C776G-TCN2 homozygote recessive subjects. Natural 5-methyltetrahydrofolate intake is interesting: Wildtype A1298C-MTHFR, heterozygote C677T-MTHFR, wildtype A2756G-MS and recessive A66G-MSR individuals all show a significant reciprocal association with homocysteine. 4). Stepwise regression of all genotypes to predict risk for AP indicated A2756G-MS and A66G-MSR to be most relevant (p = 0.0176 and 0.0408 respectively). Results were corrected for age and gender.ConclusionA methylation diet influences methyl group synthesis in the regulation of blood homocysteine level, and is modulated by genetic interactions. Methylation-related nutrients also interact with key genes to modify risk of AP, a precursor of colorectal cancer. Independent of diet, two methylation-related genes (A2756G-MS and A66G-MSR) were directly associated with AP occurrence

Hydrogen sulphide-related thiol metabolism and nutrigenetics in relation to hypertension in an elderly population

Hydrogen sulphide (H2S) is a gaseous signalling molecule that regulates blood flow and pressure. It is synthesised from cysteine via cystathionine β-synthase and cystathionine γ-lyase. We examined whether thiol precursors of H2S, transsulphuration pathway gene variants (CBS-844ins68 and CTH-G1364T) and key B-vitamin cofactors might be critical determinants of hypertension in an elderly Australian population. An elderly Australian retirement village population (n = 228; age 65–96 years, 91 males and 137 females) was assessed for the prevalence of two transsulphuration pathway–related variant genes associated with cysteine synthesis and hence H2S production. Thiols were determined by HPLC, genotypes by PCR and dietary intake by food frequency questionnaire. Homocysteine levels were statistically higher in the hypertensive phenotype (p = 0.0399), but there was no difference for cysteine or glutathione. Using nominal logistic regression, cysteine, CTH-G1364T genotype, dietary synthetic folate and vitamin B6 predicted clinical phenotype (determined as above/below 140/90 mm Hg) and then only in female subjects (p = 0.0239, 0.0178, 0.0249 and 0.0371, respectively). Least-squares regression supports cysteine being highly inversely predictive of diastolic blood pressure: p and r 2 values <0.0001 and 0.082; 0.0409 and 0.046; and <0.0001 and 0.113 for all subjects, males and females, respectively. Additionally, CTH-G1364T genotype predicts diastolic blood pressure in males (p = 0.0217; r 2 = 0.083), but contrasts with observations for females. Overall, analyses, including stepwise regression, suggest cysteine, dietary natural and synthetic folate, vitamins B6 and B12, and both genetic variants (CTH-C1364T and CBS-844ins68) are all aetiologically relevant in the regulation of blood pressure. Hydrogen sulphide is a vasorelaxant gasotransmitter with characteristics similar to nitric oxide. Cysteine and the G1364T and 844ins68 variants of the cystathionine γ-lyase and cystathionine β-synthase genes, respectively, are the biological determinants of H2S synthesis, and all three are shown here to influence the hypertensive phenotype. Additionally, B-vitamin cofactors for these three enzymes may also be important determinants of blood pressure

Gene-nutrient interaction between folate and dihydrofolate reductase in risk for adenomatous polyp occurrence : a preliminary report

Folate and related gene variants are significant risk factors in the aetiology of colorectal cancer. Dihydrofolate reductase (DHFR) is critical in the metabolism of synthetic folic acid (pteroylmonoglutamatamic, PteGlu) to tetrahydrofolate following absorption. Therefore, the 19bp deletion variant of DHFR may lead to the alteration of folate-related colorectal disease susceptibility. This study examined the association between PteGlu and 19bp del-DHFR, and adenomatous polyp (AP) occurrence, an antecedent of colorectal cancer. A total of 199 subjects (162 controls and 37 AP cases) were analysed to determine dietary intake of total folate, natural methylfolate and synthetic PteGlu, level of erythrocyte folate and plasma homocysteine (tHcy), and genotype of 19bp del-DHFR. Dietary folate intake, erythrocyte folate, tHcy and 19bp del-DHFR variants did not independently predict the occurrence of AP. However, a gene-nutrient interaction was observed when subjects were stratified according to dietary folate intake. In subjects with a folate intake above the median value due to significant dietary PteGlu content, the presence of the 19bp-deletion allele decreased the risk for AP (OR=0.35, 95% CI: 0.13-0.97). However, such association was not evident in individuals with a folate intake below the median value. In conclusion, the finding suggests that folate nutrition and 19bp del-DHFR variation may interact to modify AP risk

Folate status, folate-related genes and serum miR-21 expression: Implications for miR-21 as a biomarker

Background: Free circulating microRNA (miRNA) in serum may be valuable biomarkers for disease diagnosis and prognosis. miR-21, the archetypal oncogenic miRNA, has been proposed as a biomarker for colorectal cancer and its benign precursor, adenomatous polyps. However, it is now becoming clear that circulating miRNA profiles may be sensitive to lifestyle and environmental influences. Dietary components involved in one-carbon metabolism are particularly well placed to modulate miRNA expression through an influence on DNA methylation pathways. Methods: We investigated the role of methyl group donors (folate, B12, cysteine, homocysteine), polymorphisms of the enzymes of one-carbon metabolism, and serum miR-21 expression in a primary case–control cohort (colonoscopy confirmed adenomatous colon polyps vs controls; n = 253) and a secondary cross-sectional cohort (over 65s; n = 649). The relationships between these parameters and serum miR-21 levels were assessed, stratified by gender. Conclusions: Serum miR-21 expression was related to occurrence of adenomatous polyps in females, but not males. Folate levels and MTHFR-C677T genotype was associated with miR-21 expression in both genders. Additionally, DHFR-19 del and MSR-A66G were associated with miR-21 expression in females and males, respectively. Stimulation with excess folate increased expression of miR-21 in colon cancer cell lines. General significance: This study demonstrates that serum miR-21 expression correlates with folate status and related genetic status. This may have consequences for the proposed use of miR-21 as a colorectal cancer biomarker

TAS2R38 bitter taste genetics, dietary vitamin C, and both natural and synthetic dietary folic acid predict folate status, a key micronutrient in the pathoaetiology of adenomatous polyps

Taste perception may influence dietary preferences and nutrient intakes contributing to diet-related disease susceptibility. This study examined bitter taste genetics and whether variation in the TAS2R38 gene at three polymorphic loci (A49P, V262A and I296V) could alter dietary and systemic folate levels and dietary vitamin C intake, and whether a nutrigenetic circuit existed that might link bitter taste, folate/antioxidant status and risk for a colonic adenomatous polyp. TAS2R38 diplotype predicted bitter taste (PROP) phenotype (p value <0.00001) and red cell folate status (p = 0.0179) consistent with the diplotype that has the broadest range of bitter perception (AVI/PAV) also possessing the highest average red cell folate value. However, TAS2R38 diplotype did not predict dietary intake of methylfolic acid, pteroylmonoglutamic acid or total folic acid. Neither did it predict dietary intake of vitamin C. Despite this, intake of dietary folate predicts red cell folate with analysis pointing to a key nutrient-nutrient interaction between vitamin C intake and systemic folate status. Analysis of 38 patients with an adenomatous polyp and 164 controls showed that individually, dietary nutrient intake, nutrient status and taste diplotype did not influence polyp risk. However, red cell folate status (in individuals below the population median value) did interact with bitter taste diplotype (AVI/PAV) to predict polyp risk (p = 0.0145). Furthermore, synthetic folic acid (below median intake) was statistically associated with adenoma occurrence (p = 0.0215); individuals with adenomatous polyps had a 1.77× higher intake than controls. Additionally, stepwise regression taking account of all dietary nutrients showed a tight relationship between methylfolic acid (but not pteroylmonoglutamic acid) intake and red cell folate level in those with a low folate status and occurrence of an adenomatous polyp (p = 0.0039). These findings point to a role for folate in the pathoaetiology of adenomatous polyps, with the natural and synthetic vitamers not necessarily having the same biological effect

Genetic variation in glutamate carboxypeptidase II and interaction with dietary natural vitamin C may predict risk for adenomatous polyp occurrence

Background: The C1561T variant of the glutamate carboxypeptidase II (GCPII) gene is critical for natural methylfolylpolyglutamte (methylfolate) absorption, and has been associated with perturbations in folate metabolism and disease susceptibility. However, little is known on C1561T-GCPII as a risk factor for colorectal cancer. Therefore, this study examined whether C1561T-GCPII influences folate metabolism and adenomatous polyp occurrence. Materials and Methods: 164 controls and 38 adenomatous polyp cases were analysed to determine blood folate and plasma homocysteine (Hcy) level, dietary intake of natural methylfolate, synthetic pteroylglutamic acid (PteGlu), vitamin C and C1561T-GCPII genotype. Results: In controls and cases, 7.3 and 18.4 percent of subjects respectively, were found to have the CT genotype, increasing the risk for adenomatous polyp occurrence 2.86 times (95% CI:1.37-8.0, p=0.035). Total dietary folate, methylfolate and PteGlu intake and the level of erythrocyte folate and plasma Hcy did not predict the occurrence of an adenomatous polyp. However, dietary natural vitamin C intake was associated with adenomatous polyp risk within C1561T-GCPII CT genotype subjects (p=0.037). Conclusions: The findings suggest that C1561T-GCPII variation may be associated with risk for adenomatous polyp, and vitamin C may modify risk by interacting with the variant gene, its expression product and/or folate substrates