Relationship Between B-Vitamin Biomarkers and Dietary Intake with Apolipoprotein E є4 in Alzheimer's Disease.

The potential for B-vitamins to reduce plasma homocysteine (Hcy) and reduce the risk of Alzheimer's disease (AD) has been described previously. However, the role of Apolipoprotein E є4 (APOE4) in this relationship has not been adequately addressed. This case-control study explored APOE4 genotype in an Australian sample of 63 healthy individuals (female = 38; age = 76.9 ± 4.7 y) and 63 individuals with AD (female = 35, age = 77.1 ± 5.3 y). Findings revealed 55 of 126 participants expressed the APOE4 genotype with 37 of 126 having both AD and the APOE4 genotype. Analysis revealed an increased likelihood of AD when Hcy levels are >11.0 µmol/L (p = 0.012), cysteine levels were <255 µmol/L (p = 0.033) and serum folate was <22.0 nmol/L (p = 0.003; in males only). In females, dietary intake of total folate <336 µg/day (p=0.001), natural folate <270 µg/day (p = 0.011), and vitamin B2 < 1.12 mg/day (p = 0.028) was associated with an increased AD risk. These results support Hcy, Cys, and SF as useful biomarkers for AD, irrespective of APOE4 genotype and as such should be considered as part of screening and managing risk of AD.

A potential sex dimorphism in the relationship between bitter taste and alcohol consumption.

BACKGROUND: Bitterness is an innate aversive taste important in detecting potentially toxic substances, including alcohol. However, bitter compounds exist in many foods and beverages, and can be desirable, such as in beer. TAS2R38 is a well-studied bitter taste receptor with common polymorphisms. Some have reported relationships between TAS2R38 genotypes, bitter taste phenotype and alcohol intake, however results have been mixed. These mixed results may be explained by the varying taste properties of different alcoholic beverages or a sex dimorphism in responses. METHODS: Bitter taste phenotype was assessed using PROP taste test and TAS2R38-P49A genotype was assessed by RFLP-PCR. Alcohol intake was assessed by food frequency questionnaire and classified by beverage type (beer, wine, spirits or mixed drinks). The relationships between bitter taste phenotype and carriage of the P allele of the TAS2R38-A49P gene and alcohol intake were assessed adjusted for and stratified by sex, and the interaction between taste and sex was evaluated. RESULTS: The relationship between alcohol intake and bitter taste phenotype varied by beverage type, with significant results for beer, spirits and mixed drinks, but not wine. When stratified, results varied by sex, and were only significant in males. Significant interactions were found for taster phenotype and sex (total alcohol intake and intake of beer and spirits). Results were similar for carriage of the TAS2R38-P49A P allele. CONCLUSIONS: Sex-specific interactions between bitter taste phenotype, TAS2R38 genotype and alcohol intake may explain variance in previous studies and may have implications for sex-specific disease risk and public health interventions.

Vitamin D Receptor Polymorphisms Relate to Risk of Adenomatous Polyps in a Sex-Specific Manner.

Vitamin D receptor (VDR) gene polymorphisms may influence risk for adenomatous polyps (AP), a benign precursor to colon cancer, via modulation of vitamin D sensitive pathways, including cell proliferation and differentiation. However, results have been mixed and any association remains contentious. Failure to clinically exclude the presence of (AP in control cohorts may contribute to the lack of consensus. Therefore, we assessed the role of the FokI, BsmI, ApaI, and TaqI VDR polymorphisms in modifying risk for AP, adjusting for a range of dietary and lifestyle variables. Blood was collected from colonoscopy patients (n = 258) and VDR polymorphisms assessed by restriction fragment length polymorphism. Dietary habits were estimated from food frequency questionnaires. Odds ratios for AP were calculated by genotype, stratified by sex, and adjusted for age, lifestyle, and dietary factors. FokI was associated with modified risk for AP in males, whereas the BsmI/ApaI/TaqI haplotype was associated with modified risk in females. No interaction was found between VDR variants and vitamin D intake. This study offers novel insight into the potential for VDR genetics to contribute to risk for AP and is the first to demonstrate a sex-specific relationship between these polymorphisms and risk for AP.

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

PURPOSE: The 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. METHODS: 249 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. RESULTS: 1). 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. CONCLUSION: A 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.

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.

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.

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.

Vitamin D, folate, and potential early lifecycle environmental origin of significant adult phenotypes.

BACKGROUND AND OBJECTIVES: Vitamin D and folate are highly UV sensitive, and critical for maintaining health throughout the lifecycle. This study examines whether solar irradiance during the first trimester of pregnancy influences vitamin D receptor (VDR) and nuclear folate gene variant occurrence, and whether affected genes influence late-life biochemical/clinical phenotypes. METHODOLOGY: 228 subjects were examined for periconceptional exposure to solar irradiance, variation in vitamin D/folate genes (polymerase chain reaction (PCR)), dietary intake (food frequency questionnaire (FFQ)) and important adult biochemical/clinical phenotypes. RESULTS: Periconceptional solar irradiance was associated with VDR-BsmI (P = 0.0008(wk7)), TaqI (P = 0.0014(wk7)) and EcoRV (P = 0.0030(wk6)) variant occurrence between post-conceptional weeks 6-8, a period when ossification begins. Similar effects were detected for other VDR gene polymorphisms. Periconceptional solar irradiance was also associated with 19 bp del-DHFR (P = 0.0025(wk6)), and to a lesser extent C1420T-SHMT (P = 0.0249(wk6)), a folate-critical time during embryogenesis. These same genes were associated with several late-life phenotypes: VDR-BsmI, TaqI and ApaI determined the relationship between dietary vitamin D and both insulin (P < 0.0001/BB, 0.0007/tt and 0.0173/AA, respectively) and systolic blood pressure (P = 0.0290/Bb, 0.0299/Tt and 0.0412/AA, respectively), making them important early and late in the lifecycle. While these and other phenotype associations were found for the VDR variants, folate polymorphism associations in later-life were limited to C1420T-SHMT (P = 0.0037 and 0.0297 for fasting blood glucose and HbA1c levels, respectively). We additionally report nutrient-gene relationships with body mass index, thiol/folate metabolome, cognition, depression and hypertension. Furthermore, photoperiod at conception influenced occurrence of VDR-Tru9I and 2R3R-TS genotypes (P = 0.0120 and 0.0360, respectively). CONCLUSIONS AND IMPLICATIONS: Findings identify environmental and nutritional agents that may interact to modify gene-phenotype relationships across the lifecycle, offering new insight into human ecology. This includes factors related to both disease aetiology and the evolution of skin pigmentation.

Vitamin C-related nutrient-nutrient and nutrient-gene interactions that modify folate status.

PURPOSE: Folate-related nutrient-nutrient and nutrient-gene interactions modify disease risk; we therefore examined synergistic relationships between dietary folic acid, vitamin C and variant folate genes with respect to red cell folate status. METHODS: Two hundred and twelve subjects were examined using chemiluminescent immunoassay, PCR and food frequency questionnaire to determine red cell and serum folate, 14 folate gene polymorphisms, dietary folate (natural and synthetic) and vitamin C. RESULTS: When examined independently, synthetic PteGlu correlates best with red cell folate at higher levels of intake (p = 0.0102), while natural 5CH(3)-H(4)-PteGlu(n) correlates best with red cell folate at lower levels of intake (p = 0.0035). However, dietary vitamin C and 5CH(3)-H(4)-PteGlu(n) interact synergistically to correlate with red cell folate at higher levels of intake (p = 0.0005). No interaction between dietary vitamin C and PteGlu was observed. This 'natural' nutrient-nutrient interaction may provide an alternative to synthetic PteGlu supplementation that is now linked to adverse phenomena/health outcomes. On its own, vitamin C also correlates with red cell folate (p = 0.0150) and is strongly influenced by genetic variation in TS, MTHFR and MSR, genes critical for DNA and methionine biosynthesis that underpin erythropoiesis. Similarly, dietary vitamin C and 5CH(3)-H(4)-PteGlu(n) act synergistically to modify red cell folate status according to variation in folate genes: of note, heterozygosity for 2R3R-TS (p = 0.0181), SHMT (p = 0.0046) and all three MTHFR SNPs (p = 0.0023, 0.0015 and 0.0239 for G1793A, C677T and A1298C variants, respectively) promote a significant association with red cell folate. Again, all these genes are critical for nucleic acid biosynthesis. Folate variants with the strongest independent effect on folate status were C677T-MTHFR (p = 0.0004) and G1793A-MTHFR (p = 0.0173). CONCLUSIONS: 5CH(3)-H(4)-PteGlu(n) assimilation and variant folate gene expression products may be critically dependent on dietary vitamin C.

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

Hydrogen sulphide (H(2)S) is a gaseous signalling molecule that regulates blood flow and pressure. It is synthesised from cysteine via cystathionine ß-synthase and cystathionine γ-lyase. We examined whether thiol precursors of H(2)S, 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 H(2)S 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 B(6) 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 B(6) and B(12), 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 ß-synthase genes, respectively, are the biological determinants of H(2)S 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.

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.

Folate nutritional genetics and risk for hypertension in an elderly population sample.

BACKGROUND/AIMS: 118 elderly participants (65-90 years) were assessed for any relationship between folate, related genes and hypertension. METHODS: Six B-vitamin-related SNPs were genotyped in 80 normotensive and 38 hypertensive subjects. RESULTS: Of six polymorphisms (677C>T-MTHFR, 1298A>C-MTHFR, 80G>A-RFC, 2756A>G-MS, 66A>G- MSR, 19bpDHFR and 1561C>T-GCPII), only 677C>T-MTHFR was a significant risk for hypertension: OR 1.89; 95% CI 1.07-3.32 (chi2 p = 0.038). Additionally, hypertensive subjects had a significantly lower intake of dietary folate than normotensive individuals (p = 0.0221), although this did not markedly alter blood metabolite levels. Several significant linear associations between dietary folate and related blood metabolites were found in normotensive subjects (p < 0.001 for Hcy, red cell and serum folate) and were as predicted on an a priori basis -- generally weaker associations existed in hypertensive subjects (p < 0.05 for serum folate). This was true for data examined collectively or by genotype. Multiple-regression analysis for diastolic or systolic blood pressure showed significant interaction for gender and folate intake (p = 0.014 and 0.019, respectively). In both cases this interaction occurred only in females, with higher folate intake associated with decreased blood pressure. Regressing diastolic blood pressure and 677C>T-MTHFR genotype showed significance (males; p = 0.032) and borderline significance (all subjects). CONCLUSION: Dietary folate and 677C>T-MTHFR genotype may modify blood pressure.