The role of folate, choline, and methionine in carcinogenesis induced by methyl-deficient diets

Association between vitamin B2 intake and prostate-specific antigen in American men: 2003-2010 National Health and Nutrition Examination Survey

BACKGROUND

Accumulating evidence suggests a pivotal role of vitamin B2 in the pathogenesis and progression of prostate cancer (PCa). Vitamin B2 intake has been postulated to modulate the screening rate for PCa by altering the concentration of prostate-specific antigen(PSA). However, the relationship between vitamin B2 and PSA remains indeterminate. Hence, we conducted a comprehensive evaluation of the association between vitamin B2 intake and PSA levels, utilizing data from the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

From a pool of 20,371 participants in the NHANES survey conducted between 2003 and 2010, a cohort of 2,323 participants was selected for the present study. The male participants were classified into four distinct groups based on their levels of vitamin B2 intake. We employed a multiple linear regression model and a non-parametric regression method to investigate the relationship between vitamin B2 and PSA levels.

RESULTS

The study cohort comprised of 2,323 participants with a mean age of 54.95 years (± 11.73). Our findings revealed a statistically significant inverse correlation between vitamin B2 intake (mg) and PSA levels, with a reduction of 0.13 ng/ml PSA concentration for every unit increase in vitamin B2 intake. Furthermore, we employed a fully adjusted model to construct a smooth curve to explore the possible linear relationship between vitamin B2 intake and PSA concentration.

CONCLUSIONS

Our study in American men has unveiled a notable inverse association between vitamin B2 intake and PSA levels, potentially posing a challenge for the identification of asymptomatic prostate cancer. Specifically, our findings suggest that individuals with higher vitamin B2 intake may be at a greater risk of being diagnosed with advanced prostate cancer in the future, possibly indicating a detection bias. These results may offer a novel explanation for the observed positive correlation between vitamin B2 intake and prostate cancer.

Dietary choline and betaine intake, choline-metabolising genetic polymorphisms and breast cancer risk: a case-control study in China

Choline and betaine are essential nutrients involved in one-carbon metabolism and have been hypothesised to affect breast cancer risk. Functional polymorphisms in genes encoding choline-related one-carbon metabolism enzymes, including phosphatidylethanolamine N-methyltransferase (PEMT), choline dehydrogenase (CHDH) and betaine-homocysteine methyltransferase (BHMT), have important roles in choline metabolism and may thus interact with dietary choline and betaine intake to modify breast cancer risk. This study aimed to investigate the interactive effect of polymorphisms in PEMT, BHMT and CHDH genes with choline/betaine intake on breast cancer risk among Chinese women. This hospital-based case-control study consecutively recruited 570 cases with histologically confirmed breast cancer and 576 age-matched (5-year interval) controls. Choline and betaine intakes were assessed by a validated FFQ, and genotyping was conducted for PEMT rs7946, CHDH rs9001 and BHMT rs3733890. OR and 95 % CI were estimated using unconditional logistic regression. Compared with the highest quartile of choline intake, the lowest intake quartile showed a significant increased risk of breast cancer. The SNP PEMT rs7946, CHDH rs9001 and BHMT rs3733890 had no overall association with breast cancer, but a significant risk reduction was observed among postmenopausal women with AA genotype of BHMT rs3733890 (OR 0·49; 95 % CI 0·25, 0·98). Significant interactions were observed between choline intake and SNP PEMT rs7946 (P interaction=0·029) and BHMT rs3733890 (P interaction=0·006) in relation to breast cancer risk. Our results suggest that SNP PEMT rs7946 and BHMT rs3733890 may interact with choline intake on breast cancer risk.

Plasma folate, vitamin B12, and homocysteine and cancers of the esophagus, stomach, and liver in a Chinese population

Evidence is accumulating regarding a role of micronutrients in folate metabolism in cancer risk. We investigated the associations of plasma folate, vitamin B12, and homocysteine with upper gastrointestinal (GI) cancers in a population-based case-control study in Taixing City, China. With informed consent, we recruited cases with cancers of esophagus (n = 218), stomach (n = 206), and liver (n = 204), and one common healthy control group (n = 405). A standardized epidemiologic questionnaire was used in face-to-face interviews, and blood samples were collected during interviews. We observed an inverse association between plasma folate levels and liver cancer. The adjusted odds ratio (aOR) was 0.46 [95% confidence interval (CI) = 0.24-0.88] comparing individuals in the highest quartile to those in the lowest. We found a positive association between plasma vitamin B12 levels and all three cancers. The aORs for those in the highest quartile were 2.80 (95% CI = 1.51-5.18) for esophageal cancer, 2.17 (1.21-3.89) for stomach cancer, and 9.97 (4.82-20.60) for liver cancer, comparing to those in the lowest quartile. We further observed interaction between plasma folate and vitamin B12 on these cancers. Our data indicated associations between plasma folate and vitamin B12 with upper GI cancers in Chinese population. Further research is warranted considering the debate over the necessity of food fortification.

Associations between dietary intake of choline and betaine and lung cancer risk

Evidence from human and animal research indicates that choline metabolic pathways may be activated during a variety of diseases, including cancer. We report results of a case-control study of 2821 lung cancer cases and 2923 controls that assessed associations of choline and betaine dietary intakes with lung cancer. Using multivariable logistic regression analyses, we report a significant association between higher betaine intake and lower lung cancer risk that varied by smoking status. Specifically, no significant association was observed between betaine intake and lung cancer among never-smokers. However, higher betaine intake was significantly associated with reduced lung cancer risk among smokers, and the protective effect was more evident among current than former smokers: for former and current smokers, the ORs (95% CI) of lung cancer for individuals with highest as compared to lowest quartiles of intake were 0.70(0.55–0.88) and 0.51(0.39–0.66) respectively. Significant linear trend of higher betaine intake and lower lung cancer risk was observed among both former (p_trend = 0.002) and current (p_trend<0.0001) smokers. A similar protective effect was also observed with choline intake both in overall analysis as well as among current smokers, with p-values for chi-square tests being 0.001 and 0.004 respectively, but the effect was less evident, as no linear trend was observed. Our results suggest that choline and betaine intake, especially higher betaine intake, may be protective against lung cancer through mitigating the adverse effect of smoking.

The effect of SAMe and betaine on Hepa 1-6, C34 and E47 liver cell survival in vitro

In recent years, methyl one-carbon metabolism has received a great deal of attention because the disruption of methyl balance in a variety of genetically modified mice is associated with the development of various forms of liver injury, namely fatty liver disease and hepatocellular carcinoma (HCC). In addition, patients with liver disease often have an abnormal expression of key genes involved in methionine metabolism as well as elevated serum levels of methionine and homocysteine (Hcy). S-adenosylmethionine (SAMe) has rapidly moved from being a methyl donor to a key metabolite that regulates hepatocyte proliferation, necrosis and differentiation. Biosynthesis of SAMe occurs in all mammalian cells as the first step in methionine catabolism in a reaction catalyzed by methionine adenosyltransferase (MAT). Decreased hepatic SAMe biosynthesis is a consequence of numerous forms of chronic liver injury. In an animal model of chronic liver SAMe deficiency, the liver is predisposed to further injury and develops spontaneous steatohepatitis and HCC. SAMe treatment in experimental animal models of liver injury shows hepatoprotective properties. Meta-analyses also showed that it is effective in the treatment of patients with cholestatic liver diseases. We studied the survival of liver cells treated with SAMe and betaine using Hepa 1-6 and E47/C34 cell lines. We showed that exogenous SAMe decreased the number of Hepa 1-6 and E47/C34 cells, and increased the number of dead cells in vitro. Betaine had no significant effect on the number of surviving cells and the number of dead cells. The combination of both methyl donors significantly increased the survival of liver cells and reduced necrosis, compared to SAMe alone. This study showed the inhibition of the proliferation and increased necrosis in response to SAMe on liver cancer cell lines Hepa 1-6 and C34.

New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

Choline and betaine intake and risk of breast cancer among post-menopausal women

Background:

Choline and betaine, similar to folate, are nutrients involved in one-carbon metabolism and hypothesised to reduce breast cancer risk. No prospective study among post-menopausal women has examined choline and betaine intakes in relation to breast cancer risk.

Methods:

We examined the intake of choline and betaine and breast cancer risk among 74 584 post-menopausal women in the Nurses’ Health Study. Nutrient intake was assessed using a validated food-frequency questionnaire six times since 1984. During 20 years of follow-up from 1984 until 2004, we documented 3990 incident cases of invasive breast cancer.

Results:

Overall, choline (mean±s.d.; 326±61 mg per day) and betaine (104±33 mg per day) intake was not associated with a reduced risk of post-menopausal breast cancer. Participants in the highest quintile of intakes had multivariate relative risks of 1.10 (95% confidence interval (95% CI): 0.99–1.22; P-value, test for trend=0.14) for choline and 0.98 (95% CI: 0.89–1.09; P-value, test for trend=0.96) for betaine, compared with those in the lowest quintiles of intakes. The results were similar in breast cancer stratified by hormone receptor (oestrogen receptor/progesterone receptor) status. The association between choline intake and breast cancer risk did not differ appreciably by alcohol intake (non-drinker, <15 or 15+ g per day) or several other breast cancer risk factors, including family history of breast cancer, history of benign breast disease, body mass index, post-menopausal hormone use, and folate intake.

Conclusion:

We found no evidence that higher intakes of choline and betaine reduce risk of breast cancer among post-menopausal women.

Dietary choline and betaine and the risk of distal colorectal adenoma in women

BACKGROUND

Choline and betaine are involved in methyl-group metabolism as methyl-group donors; thus, like folate, another methyl-group donor, they may be associated with a reduced risk of colorectal adenomas. No epidemiologic study has examined the association of intake of these nutrients and colorectal adenoma risk.

METHODS

We investigated the relationship between intakes of choline and betaine and risk of colorectal adenoma in US women enrolled in the Nurses' Health Study. Dietary intake was measured by food-frequency questionnaires, and individual intakes of choline and betaine were calculated by multiplying the frequency of consumption of each food item by its choline and betaine content and summing the nutrient contributions of all foods. Logistic regression models were used to calculate adjusted odds ratios (as approximations for relative risks) and 95% confidence intervals (CIs) of colorectal adenoma. All statistical tests were two-sided.

RESULTS

Among 39246 women who were initially free of cancer or polyps and who had at least one endoscopy from 1984 through 2002, 2408 adenoma cases were documented. Increasing choline intake was associated with an elevated risk of colorectal adenoma; the multivariable relative risks (95% CIs) for increasing quintiles of intake, relative to the lowest quintile, were 1.03 (0.90 to 1.18), 1.01 (0.88 to 1.16), 1.23 (1.07 to 1.41), and 1.45 (1.27 to 1.67; P(trend)<.001). Betaine intake had a nonlinear inverse association with colorectal adenoma; the multivariable relative risks (95% CIs) for increasing quintiles of intake were 0.94 (0.83 to 1.07), 0.85 (0.75 to 0.97), 0.86 (0.75 to 0.98), and 0.90 (95% CI = 0.78 to 1.04; P(trend) = .09). Among individual sources of choline, choline from phosphatidylcholine and from sphingomyelin were each positively related to adenoma risk.

CONCLUSIONS

Our findings do not support an inverse association between choline intake and risk of colorectal adenoma. The positive association between choline intake and colorectal adenoma that we observed could represent effects of other components in the foods from which choline was derived and should be investigated further.

Methyl deficiency, alterations in global histone modifications, and carcinogenesis

The methyl-deficient model of endogenous hepatocarcinogenesis in rodents is unique in that dietary omission rather than the addition of chemical carcinogens leads to tumor formation. Thus, the biochemical and molecular events predisposing to cancer in this model result from chronic metabolic stress and provide an ideal model system to study progressive alterations that occur during carcinogenesis. Moreover, epigenetic alterations imposed by this diet are believed to be 1 of the main mechanisms responsible for malignant transformation of rat liver cells. In this study we examined the changes in global histone modification patterns in liver during hepatocarcinogenesis induced by methyl deficiency. Feeding animals the methyl-deficient diet (MDD) led to progressive loss of histone H4 lysine 20 trimethylation (H4K20me3), H3 lysine 9 trimethylation (H3K9me3), and histone H3 lysine 9 (H3K9ac) and histone H4 lysine 16 (H4K16ac) acetylation. A considerable decrease of H4K20me3 and H3K9ac was also detected in liver tumors induced by MDD. In contrast, liver tumors displayed an increase in H3K9me3 and H4K16ac. To determine the possible mechanism of alterations of histone modifications, we analyzed the expression of histone-modifying enzymes in liver during hepatocarcinogenesis. The expression of Suv4-20h2 and RIZ1 histone methyltransferases (HMTs) steadily decreased along with the development of liver tumors and reached its lowest level in tumor tissue, whereas the expression of Suv39-h1 HMT and histone acetyltransferase 1 (HAT1) substantially increased in tumors. These results illustrate the complexity and importance of histone modification changes in the etiology of hepatocarcinogenesis induced by MDD.

Dietary choline and betaine assessed by food-frequency questionnaire in relation to plasma total homocysteine concentration in the Framingham Offspring Study

BACKGROUND

Epidemiologic studies of choline and betaine intakes have been sparse because a food-composition database was not available until recently. The physiologic relevance of a variation in dietary choline and betaine in the general population and the validity of intake assessed by food-frequency questionnaire (FFQ) have not been evaluated.

OBJECTIVE

This study was conducted to examine the physiologic relevance and validity of choline and betaine intakes measured by an FFQ.

DESIGN

We examined the relations between choline and betaine intakes measured by FFQ and plasma total homocysteine (tHcy) concentrations in 1960 participants from the Framingham Offspring Study.

RESULTS

Higher intakes of dietary choline and betaine were related to lower tHcy concentrations independent of other determinants, including folate and other B vitamins. For the lowest and highest quintiles of dietary choline plus betaine, the multivariate geometric means for tHcy were 10.9 and 9.9 mumol/L (P for trend < 0.0001). The inverse association was manifested primarily in participants with low folate intakes (P for interaction < 0.0001). Among participants with folate intakes < or =250 microg/d, the geometric mean tHcy concentrations in the lowest and highest quintiles of choline plus betaine intakes were 12.4 and 10.2 micromol/L (P for trend < 0.0001). Except for choline from phosphatidylcholine, individual forms of choline were inversely associated with tHcy concentrations.

CONCLUSIONS

Our findings provide support for a physiologically important variation in choline and betaine intakes in the general population and for the validity of intake measured by FFQ.

Diethanolamine and Phenobarbital Produce an Altered Pattern of Methylation in GC-Rich Regions of DNA in B6C3F1 Mouse Hepatocytes Similar to That Resulting from Choline Deficiency

DNA methylation is an epigenetic mechanism regulating transcription, which when disrupted, can alter gene expression and contribute to carcinogenesis. Diethanolamine (DEA), a non-genotoxic alkanolamine, produces liver tumors in mice. Studies suggest DEA inhibits choline uptake and causes biochemical changes consistent with choline deficiency (CD). Rodents fed methyl-deficient diets exhibit altered methylation of hepatic DNA and an increase in liver tumors, e.g., CD causes liver tumors in B6C3F1 mice. We hypothesize that DEA-induced CD leads to altered methylation patterns which facilitates tumorigenesis. B6C3F1 hepatocytes in primary culture were grown in the presence of either 4.5 mM DEA, 3 mM Phenobarbital (PB), or CD media for 48 h. These concentrations induced comparable increases in DNA synthesis. PB, a nongenotoxic rodent liver carcinogen known to alter methylation in mouse liver, was included as a positive control. Global, average, DNA methylation status was not affected. The methylation status of GC-rich regions of DNA, which are often associated with promoter regions, were assessed via methylation-sensitive restriction digestion and arbitrarily primed PCR with capillary electrophoretic separation and detection of PCR products. DEA, PB, and CD treatments resulted in 54, 63, and 54 regions of altered methylation (RAMs), respectively, and the majority were hypomethylations. A high proportion of RAMs (72%) were identical when DEA was compared to CD. Similarly, 70% were identical between PB and CD. Altered patterns of methylation in GC-rich regions induced by DEA and PB resemble that of CD and indicate that altered DNA methylation is an epigenetic mechanism involved in the facilitation of mouse liver tumorigenesis.

Irreversible global DNA hypomethylation as a key step in hepatocarcinogenesis induced by dietary methyl deficiency

Dietary methyl group deprivation is now well recognized as a model of hepatocarcinogenesis in rodents. In the present study, we examined the effects of feeding a methyl-deficient diet followed by a methyl-adequate diet on the extent of methylation of liver DNA and on the formation and evolution of altered hepatic foci. Male F344 rats were fed a methyl-deficient diet for 9, 18, 24, and 36 weeks, followed by re-feeding a methyl-adequate diet for a total of 54 weeks. Similar to previous findings, the methyl-deficient diet resulted in decreased levels of S-adenosylmethionine (SAM), SAM/SAH ratios, and global DNA hypomethylation. Feeding the methyl-adequate diet restored the liver SAM levels and SAM/SAH ratios to control levels in all experimental groups. In contrast, re-feeding the complete diet restored DNA methylation to normal level only in the group that had been fed the methyl-deficient diet for 9 weeks; in animals exposed to methyl deprivation longer, the methyl-adequate diet failed to reverse the hypomethylation of DNA. Liver tissue of rats exposed to methyl deficiency for 9, 18, 24, or 36 weeks was characterized by the persistent presence of placental isoform of glutathione-S-transferase (GSTpi)-positive lesions despite re-feeding the methyl-adequate diet. The persistence of altered hepatic foci in liver after withdrawal of methyl-deficient diet serves as an indication of the carcinogenic potential of a methyl-deficient diet. Substitution of the methyl-deficient diet with complete diet failed to prevent the expansion of initiated foci and restore DNA methylation in animals exposed to deficiency for 18, 24, or 36 weeks. The association between DNA hypomethylation and expansion of foci suggests that stable DNA hypomethylation is a promoting factor for clonal expansion of initiated cells. These results provide an experimental evidence and a mechanistic basis by which epigenetic alterations may contribute to the initiation and promotion steps of carcinogenesis.

Hypomethylation of DNA and the insulin-like growth factor-II gene in dichloroacetic and trichloroacetic acid-promoted mouse liver tumors

Dichloroacetic acid (DCA) and trichloroacetic acid (TCA) are mouse liver carcinogens. DNA hypomethylation is a common molecular event in cancer that is induced by DCA and TCA. Hypomethylation of DNA and the insulin-like growth factor-II (IGF-II) gene was determined in DCA- and TCA-promoted liver tumors. Mouse liver tumors were initiated by N-methyl-N-nitrosourea and promoted by either DCA or TCA. By dot-blot analysis using an antibody for 5-methylcytosine, the DNA in DCA- and TCA-promoted tumors was demonstrated to be hypomethylated. The methylation status of 28 CpG sites in the differentially methylated region-2 (DMR-2) of mouse IGF-II gene was determined. In liver, 79.3 +/- 1.7% of the sites were methylated, while in DCA- and TCA-treated mice, only 46.4 +/- 2.1% and 58.0 +/- 1.7% of them were methylated and 8.7 +/- 2.6% and 10.7 +/- 7.4% were methylated in tumors. The decreased methylation found in liver from mice exposed to DCA or TCA occurred only in the upstream region of DMR-2, while in tumors it occurred throughout the probed region. mRNA expression of the IGF-II gene was increased in DCA- and TCA-promoted liver tumors but not in non-involved liver from DCA- and TCA-exposed mice. The results support the hypothesis that DNA hypomethylation is involved in the mechanism for the tumorigenicity of DCA and TCA.

Effects of vitamin B12 and folate deficiencies on DNA methylation and carcinogenesis in rat liver

Deficiencies of the major dietary sources of methyl groups, methionine and choline, lead to the formation of liver cancer in rodents. The most widely investigated hypothesis has been that dietary methyl insufficiency results in abnormal DNA methylation. Vitamin B12 and folate also play important roles in DNA methylation since these two coenzymes are required for the synthesis of methionine and S-adenosyl methionine, the common methyl donor required for the maintenance of methylation patterns in DNA. The aim of this study was to review the effects of methyl-deficient diets on DNA methylation and liver carcinogenesis in rats, and to evaluate the role of vitamin B12 status in defining carcinogenicity of a methyl-deficient diet. Several studies have shown that a methyl-deficient diet influences global DNA methylation. Evidence from in vivo studies has not clearly established a link between vitamin B12 and DNA methylation. We reported that vitamin B12 and low methionine synthase activity were the two determinants of DNA hypomethylation. Choline- or choline/methionine-deficient diets have been shown to cause hepatocellular carcinoma in 20-50% of animals after 12-24 months. In contrast, the effect of vitamin B12 withdrawal, in addition to choline, methionine and folate, induced hepatocellular carcinoma in less than 5% of rats.