Dietary intake of folate and alcohol, MTHFR C677T polymorphism, and colorectal cancer risk in Korea

MTHFR Gene C677T Polymorphism (rs1801133) and Susceptibility to Colorectal Polyps in an Azerbaijani Population

BACKGROUND

Understanding the relationships between the methylenetetrahydrofolate reductase (MTHFR) gene polymorphism, colorectal polyps, and CRC risk can aid in advancing personalized medicine approaches in CRC prevention. The aim of the current study is to identify the association of C677T polymorphism of the MTHFR gene with the risk of colorectal polyps in the Azerbaijani population.

METHODS

This study included 125 patients with colon polyps and 155 healthy individuals as a control group. DNA was extracted from venous blood samples obtained from patients and healthy individuals, and the results were analyzed through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and agarose gel electrophoresis.

RESULTS

Wild-type, heterozygote, and homozygous mutant were revealed within 69 (55.2%), 49 (39.2%), and 7 (5.6%) patients and within 100 (64.5%), 45 (29%), and 10 (6.5%) healthy controls, respectively. However, no significant statistical associations were observed between CT and TT genotypes, dominant (CC vs. CT + TT) and recessive (CC + CT vs. TT) models, and the mutant T allele and disease risk. There were also no significant differences between patients and controls regarding age, sex, smoking and alcohol use.

CONCLUSION

Our research did not reveal any significant association between the MTHFR C677T polymorphism and susceptibility to colorectal polyps in the Azerbaijan population.

Association between nutrient intake related to the one-carbon metabolism and colorectal cancer risk: a case-control study in the Basque Country

PURPOSE

Epidemiologic evidence for the association between methyl-donor nutrient intake and colorectal cancer (CRC) risk remains inconclusive. We aimed to examine the relationship between intake of vitamins of the B group, methionine, total choline and betaine and CRC risk, in a population from the CRC screening programme in the Basque Country.

DESIGN

This observational study included 308 patients with CRC and 308 age- and sex-matched subjects as controls. During recruitment, dietary, anthropometric, lifestyle, socioeconomic, demographic, and health status information was collected. Conditional logistic regression was used to estimate the odds ratios (ORs) for CRC risk.

RESULTS

The adjusted ORs for CRC risk decreased with higher intakes of choline and betaine (p < 0.05). After further adjustment for folate, high intake of choline and betaine remained associated with a reduced CRC risk (adjusted model for choline, OR third tertile vs first tertile = 0.45, 95% CI 0.26-0.80, p = 0.006; for betaine, OR third tertile vs first tertile = 0.27, 95% CI 0.16-0.47, p < 0.001). Regarding the other nutrients, our findings indicated a non-significant decrease in CRC risk with the high level of intake.

CONCLUSIONS

Our data suggest that choline and betaine intake influence CRC risk in the studied population.

Diet is Linked to Colorectal Cancer Risk among Asian Adults: A Scoping Review

This review aimed to map current evidence on the association between dietary factors and colorectal cancer (CRC) risk in Asia. This review was conducted based on Arksey and O'Malley methodological framework. Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) flow diagram was used to record the review process. For the purpose of searching for articles, three electronic databases namely PubMed, EBSCOHost and ScienceDirect were employed. The inclusion criteria for articles selection were articles with association analysis between diet and CRC risk among Asians, had adults as participants, articles were written in English, open-accessed and published between years 2009 and 2021. Thus, 35 out of 369 screened articles were eventually included in this review which covered 28 case-control studies, six prospective cohort studies and one randomised clinical trial. Foods such as meats, alcohol and westernised diet have been shown to be associated with increase of CRC risk while fruits, vegetables and traditional meals decreased the risk of CRC. Only a few interventional and dietary patterns studies were identified. Specific single foods and nutrients and dietary patterns have been found to increase the risk but also protected the Asian population against CRC. The findings of this review will guide health professionals, researchers and policy makers to conduct a suitable study design and topic for future research.

Influence of methyl donor nutrients as epigenetic regulators in colorectal cancer: A systematic review of observational studies

BACKGROUND

Dietary methyl donors might influence DNA methylation during carcinogenesis of colorectal cancer (CRC). However, whether the influence of methyl donor intake is modified by polymorphisms in such epigenetic regulators is still unclear.

AIM

To improve the current understanding of the molecular basis of CRC.

METHODS

A literature search in the Medline database, Reference Citation Analysis (https://www.referencecitationanalysis.com/), and manual reference screening were performed to identify observational studies published from inception to May 2022.

RESULTS

A total of fourteen case-control studies and five cohort studies were identified. These studies included information on dietary methyl donors, dietary components that potentially modulate the bioavailability of methyl groups, genetic variants of methyl metabolizing enzymes, and/or markers of CpG island methylator phenotype and/or microsatellite instability, and their possible interactions on CRC risk.

CONCLUSION

Several studies have suggested interactions between methylenetetrahydrofolate reductase polymorphisms, methyl donor nutrients (such as folate) and alcohol on CRC risk. Moreover, vitamin B₆, niacin, and alcohol may affect CRC risk through not only genetic but also epigenetic regulation. Identification of specific mechanisms in these interactions associated with CRC may assist in developing targeted prevention strategies for individuals at the highest risk of developing CRC.

Association of MTHFR C677T variant genotype with serum folate and Vit B12 in Iranian patients with colorectal cancer or adenomatous polyps

Background

The incidence of colorectal cancer (CRC) has increased during recent years in Iran and other developing countries. Clinical studies suggest that essential folate dietary intake and moderate deficiency of methylenetetrahydrofolate reductase (MTHFR) may protect and reduce the risk of CRC. The present study aimed to investigate the clinical significance of C677T polymorphism within the MTHFR gene and its correlation with the serum folate and Vit B₁₂ in the Iranian population suffering from CRC.

Methods

Blood samples were taken from 1017 Iranian individuals (517 cases and 500 controls) who were referred for colonoscopy. TaqMan probe assay was performed for C677T MTHFR polymorphism. Sera were fractionated from the blood samples of 43 patients and controls and folate and Vit B₁₂ concentrations were measured by a monobind kit. The correlation of MTHFR polymorphisms and folate/vitamin-B₁₂ with CRC risk was analyzed.

Results

In the current study, we found the frequency of three different genotypes of MTHFR polymorphism in the Iranian population i.e., CC, CT, and TT, to be 51.31, 26.73, 21.96 and 61, 32.2, 6.8 in case and control groups, respectively. The homozygote genotype of MTHFR rs1801133 polymorphism is associated with an increased risk of CRC by 3.68, 1.42, and 3.74-fold in codominant, dominant, and recessive models respectively (p value < 0.01). Our study revealed that there was no significant difference between the amount of folate and Vit B12 in the case and control groups (p value > 0.05).

Conclusions

This study revealed that there was no significant difference between the amount of folate and Vit B₁₂ in the case and control groups. Furthermore, our results demonstrated a higher risk association for 677TT and 677TT + C677T genotypes of MTHFR compared with 677CC carriers among CRC patients.

Role of Chronic Alcoholism Causing Cancer in Omnivores and Vegetarians through Epigenetic Modifications

One of the significant consequences of alcohol consumption is cancer formation via several contributing factors such as action of alcohol metabolites, vitamin deficiencies, and oxidative stress. All these factors have been shown to cause epigenetic modifications via DNA hypomethylation, thus forming a basis for cancer development. Several published reviews and studies were systematically reviewed. Omnivores and vegetarians differ in terms of nutritional intake and deficiencies. As folate deficiency was found to be common among the omnivores, chronic alcoholism could possibly cause damage and eventually cancer in an omnivorous individual via DNA hypomethylation due to folate deficiency. Furthermore, as niacin was found to be deficient among vegetarians, damage in vegetarian chronic alcoholics could be due to increased NADH/NAD ⁺ ratio, thus slowing alcohol metabolism in liver leading to increased alcohol and acetaldehyde which inhibit methyltransferase enzymes, eventually leading to DNA hypomethylation. Hence correcting the concerned deficiency and supplementation with S-adenosyl methionine could prove to be protective in chronic alcohol use.

Folate, alcohol, ADH1B and ALDH2 and colorectal cancer risk

OBJECTIVE

There is limited evidence on the interaction by alcohol dehydrogenase 2 (ADH1B) (rs1229984) and aldehyde dehydrogenase 2 (ALDH2) (rs671) regarding the associations of alcohol and a methyl diet (low folate and high alcohol intake) with cancer risk, partly because of rare polymorphisms in Western populations.

DESIGN

In a case-control study, we estimated the ORs and 95 % CIs to evaluate the associations of ADH1B and ALDH2 genotypes with colorectal cancer (CRC) and the joint association between methyl diets and ADH1B and ALDH2 polymorphisms with CRC risk using logistic regression models.

SETTING

A hospital-based case-control study.

PARTICIPANTS

In total, 1001 CRC cases and 899 cancer-free controls admitted to two university hospitals.

RESULTS

We found that alcohol intake increased the risk of CRC; OR (95 % CI) was 2·02 (1·41, 2·87) for ≥60 g/d drinkers compared with non-drinkers (Ptrend < 0·001). The associations for two polymorphisms with CRC were not statistically significant. However, we found a potential interaction of ALDH2 with methyl diets and CRC. We observed a 9·08-fold (95 % CI 1·93, 42·60) higher risk of CRC for low-methyl diets compared with high-methyl diets among individuals with an A allele of ALDH2, but the association was not apparent among those with ALDH2 GG (Pinteraction = 0·02).

CONCLUSIONS

Our data support the evidence that gene-methyl diet interactions may be involved in CRC risk in East Asian populations, showing that a low-methyl diet increased the risk of CRC among individuals with an A allele of ALDH2.

Folic Acid Supplement Intake and Risk of Colorectal Cancer in Women; A Case Control Study

Background

An ongoing controversy exists on the role of folic acid supplementation in colorectal cancer risk among epidemiological studies.

Objective

To assess the association between maternal folic acid supplementation and colorectal cancer risk.

Methods

A paired matched case control study of 405 subjects was performed, including women residing in 135 villages of East Azerbaijan, Iran. Per area, subjects were followed regularly in local healthcare centers, where health- and social-related information have been collected prospectively in face to face interviews by well-trained health workers. We extracted folic acid supplement intake, baseline characteristics, and confounders from healthcare records. The data for study participants were linked to national cancer registry repositories, from which we retrieved the data of 135 women diagnosed with colorectal cancer between 2005 to 2015. Two hundred seventy controls were individually matched with cases in terms of residing village, age, and gender. We applied multivariate conditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

Findings

There was no significant association between folic acid supplementation and colorectal cancer risk in those with history of folic acid intake compared to those with no history of intake (OR 0.95; 95% CI 0.59 to 1.53), in those with less than five years of folic acid (0.79; 0.45 to 1.39) or in those with ≥5 years intake (1.09; 0.52 to 2.26). This risk did not change after adjustment for covariates or further stratification.

Conclusions

Maternal folic acid supplementation did not affect colorectal cancer risk in a population where supplemental folic acid is prescribed with regular intervals for women of child-bearing age.

Dietary B vitamin and methionine intakes and risk for colorectal cancer: a case-control study in China

B vitamins (including folate, vitamin B2, vitamin B6 and vitamin B12) and methionine are essential for methylation reactions, nucleotide synthesis, DNA stability and DNA repair. However, epidemiological evidence among Chinese populations is limited. The objective of this study was to evaluate B vitamins and methionine in relation to colorectal cancer risk in a Chinese population. A case-control study was conducted from July 2010 to April 2019. A total of 2502 patients with colorectal cancer were recruited along with 2538 age- (5-year interval) and sex-matched controls. Dietary data were collected using a validated FFQ. Multivariable logistic regression was used to assess OR and 95 % CI. The intake of folate, vitamin B2, vitamin B6 and vitamin B12 was inversely associated with colorectal cancer risk. The multivariable OR for the highest quartile v. the lowest quartile were 0·62 (95 % CI 0·51, 0·74; Ptrend < 0·001) for folate, 0·46 (95 % CI 0·38, 0·55; Ptrend < 0·001) for vitamin B2, 0·55 (95 % CI 0·46, 0·76; Ptrend < 0·001) for vitamin B6 and 0·72 (95 % CI 0·60, 0·86; Ptrend < 0·001) for vitamin B12. No statistically significant association was found between methionine intake and colorectal cancer risk. Stratified analysis by sex showed that the inverse associations between vitamin B12 and methionine intake and colorectal cancer risk were found only among women. This study indicated that higher intake of folate, vitamin B2, vitamin B6 and vitamin B12 was associated with decreased risk of colorectal cancer in a Chinese population.

Meta-analysis of 16 studies of the association of alcohol with colorectal cancer

Alcohol consumption is an established risk factor for colorectal cancer (CRC). However, while studies have consistently reported elevated risk of CRC among heavy drinkers, associations at moderate levels of alcohol consumption are less clear. We conducted a combined analysis of 16 studies of CRC to examine the shape of the alcohol-CRC association, investigate potential effect modifiers of the association, and examine differential effects of alcohol consumption by cancer anatomic site and stage. We collected information on alcohol consumption for 14,276 CRC cases and 15,802 controls from 5 case-control and 11 nested case-control studies of CRC. We compared adjusted logistic regression models with linear and restricted cubic splines to select a model that best fit the association between alcohol consumption and CRC. Study-specific results were pooled using fixed-effects meta-analysis. Compared to non-/occasional drinking (≤1 g/day), light/moderate drinking (up to 2 drinks/day) was associated with a decreased risk of CRC (odds ratio [OR]: 0.92, 95% confidence interval [CI]: 0.88-0.98, p = 0.005), heavy drinking (2-3 drinks/day) was not significantly associated with CRC risk (OR: 1.11, 95% CI: 0.99-1.24, p = 0.08) and very heavy drinking (more than 3 drinks/day) was associated with a significant increased risk (OR: 1.25, 95% CI: 1.11-1.40, p < 0.001). We observed no evidence of interactions with lifestyle risk factors or of differences by cancer site or stage. These results provide further evidence that there is a J-shaped association between alcohol consumption and CRC risk. This overall pattern was not significantly modified by other CRC risk factors and there was no effect heterogeneity by tumor site or stage.

Prioritization of Variants for Investigation of Genotype-Directed Nutrition in Human Superpopulations

Dietary guidelines recommended by key health agencies are generally designed for a global population. However, ethnicity affects human disease and environment-gene interactions, including nutrient intake. Historically, isolated human populations with different genetic backgrounds have adapted to distinct environments with varying food sources. Ethnicity is relevant to the interaction of food intake with genes and disease susceptibility; yet major health agencies generally do not recommend food and nutrients codified by population genotypes and their frequencies. In this paper, we have consolidated published nutrigenetic variants and examine their frequencies in human superpopulations to prioritize these variants for future investigation of population-specific genotype-directed nutrition. The nutrients consumed by individuals interact with their genome and may alter disease risk. Herein, we searched the literature, designed a data model, and manually curated hundreds of papers. The resulting database houses 101 variants that reached significance (p < 0.05), from 35 population studies. Nutrigenetic variants associated with modified nutrient intake have the potential to reduce the risk of colorectal cancer, obesity, metabolic syndrome, type 2 diabetes, and several other diseases. Since many nutrigenetic studies have identified a major variant in some populations, we suggest that superpopulation-specific genotype-directed nutrition modifications be prioritized for future study and evaluation. Genotype-directed nutrition approaches to dietary modification have the potential to reduce disease risk in select human populations.

Dietary Inflammatory Index, Dietary Non-Enzymatic Antioxidant Capacity, and Colorectal and Breast Cancer Risk (MCC-Spain Study)

Inflammation and antioxidant capacity have been associated with colorectal and breast cancer. We computed the dietary inflammatory index (DII^®), and the total dietary non-enzymatic antioxidant capacity (NEAC) and associated them with colorectal and breast cancer risk in the population-based multi case-control study in Spain (MCC-Spain). We included 1852 colorectal cancer and 1567 breast cancer cases, and 3447 and 1486 population controls, respectively. DII score and NEAC were derived using data from a semi-quantitative validated food frequency questionnaire. Unconditional logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (95%CI) for energy-adjusted DII (E-DII), and a score combining E-DII and NEAC. E-DII was associated with colorectal cancer risk (OR = 1.93, highest quartile versus lowest, 95%CI:1.60–2.32; p-trend: <0.001); this increase was observed for both colon and rectal cancer. Less pronounced increased risks were observed for breast cancer (OR = 1.22, highest quartile versus lowest, 95%CI:0.99–1.52, p-trend: >0.10). The combined score of high E-DII scores and low antioxidant values were associated with colorectal cancer risk (OR = 1.48, highest quartile versus lowest, 95%CI: 1.26–1.74; p-trend: <0.001), but not breast cancer. This study provides evidence that a pro-inflammatory diet is associated with increased colorectal cancer risk while findings for breast cancer were less consistent.

Dietary B-Vitamin Intake and Risk of Breast, Endometrial, Ovarian and Colorectal Cancer among Canadians

Few studies have explored the associations of thiamin, niacin and riboflavin with risk of cancer despite their role in potentially cancer-associated one-carbon metabolism. Using multivariable Cox proportional hazards regression models modified for the case-cohort design, we examined the associations of dietary intake of the above-mentioned B vitamins, as well as folate, and vitamins B6 and B12, with risk of the breast (n = 922), endometrial (n = 180), ovarian (n = 104) and colorectal (n = 266) cancers among age-stratified subcohorts of 3,185 women who were randomly selected from a cohort of 73,909 participants. None of the B-vitamins were associated with risk of breast or colorectal cancers. However, relatively high dietary intake of folate intake was inversely associated with risk of endometrial (HRq4 vs q1: 0.52; 95% CI: 0.29-0.93) and ovarian (HRq3 vs q1: 0.39; 95% CI: 0.19-0.80) cancers while relatively high dietary intake of vitamin B6 was inversely associated with ovarian cancer risk (HRq3 vs q1: 0.49; 95% CI: 0.24-0.98). These findings suggest that dietary intake of folate may reduce risk of endometrial and ovarian cancers and dietary intake of vitamin B6 may reduce risk of ovarian cancer.

Interaction between alcohol consumption and methylenetetrahydrofolate reductase polymorphisms in thyroid cancer risk: National Cancer Center cohort in Korea

The effect of alcohol intake on thyroid cancer is unestablished, and its interaction effects with genetic susceptibility are unclear. In this case-control study, the relationship among alcohol intake, the methylenetetrahydrofolate reductase (MTHFR) gene, and thyroid cancer risk has been evaluated. In total, 642 cases and 642 controls of Korean origin were included, and the genetic variants C677T and A1298C of the MTHFR gene were analysed. The interactions between alcohol-consumption behaviour and genetic variants were analysed with a likelihood ratio test, wherein a multiplicative interaction term was added to a logistic regression model. There was an independent association between the C677T polymorphism and thyroid cancer risk but not for drinking history. For C677T C/C homozygotes, individuals with a history of alcohol consumption showed a protective OR (95% CI) of 0.42 (0.15–1.13) when never drinkers were used as the reference. However, this protective association was not observed among individuals with a T+ allele with an OR (95% CI) of 1.27 (0.89–1.82), showing different directions for the association between genotypes with a significant interaction (P_interaction = 0.009). Based on the genetic characteristics of individuals included, an interaction between alcohol intake and MTHFR C677T may modify the risk of thyroid cancer.

The Evolving Role of Multivitamin/Multimineral Supplement Use among Adults in the Age of Personalized Nutrition

Micronutrient deficiencies occur in segments of the adult population in the United States. Multivitamin/multimineral supplements (MVMS) are widely used by this population, which reduces inadequacies in micronutrient intake, but the potential for exceeding tolerable upper intake levels in others should be considered. There are concerns associated with the excessive intake of certain nutrients, particularly folic acid, and potential untoward consequences. The advent of nutrigenomics and the enhanced ability to directly study the interactions between nutrition and genetic variants and expression will allow for the conduct of more targeted studies with specific endpoints and may ultimately lead to progress in the field of personalized nutrition. The role of MVMS in health maintenance and chronic disease prevention remains controversial. Conducting studies in this area has been hampered by, among other factors, inconsistent definitions of MVMS, ranging from as few as three vitamins to broad-spectrum products containing more than two dozen vitamins and minerals. Results from some observational studies and large-scale, randomized, controlled trials suggest that MVMS may reduce the risk of some forms of cancer and, potentially, cardiovascular disease. The ongoing COcoa Supplement and Multivitamin Outcomes Study (COSMOS) is expected to build on this research and provide additional insights into these areas.

Dietary patterns and colorectal cancer risk: a meta-analysis

The analysis of dietary patterns has recently drawn considerable attention as a method of investigating the association between the overall whole diet and the risk of colorectal cancer. However, the results have yielded conflicting findings. Here, we carried out a meta-analysis to identify the association between dietary patterns and the risk of colorectal cancer. A total of 40 studies fulfilled the inclusion criteria and were included in this meta-analysis. The highest category of 'healthy' dietary pattern compared with the lowest category was apparently associated with a decreased risk for colorectal cancer [odds ratio (OR)=0.75; confidence interval (CI): 0.68-0.83; P<0.00001]. An increased risk of colorectal cancer was shown for the highest compared with the lowest category of a 'western-style' dietary pattern (OR=1.40; CI: 1.26-1.56; P<0.00001). There was an increased risk of colorectal cancer in the highest compared with the lowest category of 'alcohol-consumption' pattern (OR=1.44; CI: 1.13-1.82; P=0.003). The results of this meta-analysis indicate that a 'healthy' dietary pattern may decrease the risk of colorectal cancer, whereas 'western-style' and 'alcohol-consumption' patterns may increase the risk of colorectal cancer.

MTHFR Gene and Serum Folate Interaction on Serum Homocysteine Lowering: Prospect for Precision Folic Acid Treatment

OBJECTIVE

This post hoc analysis of the CSPPT (China Stroke Primary Prevention Trial) assessed the individual variation in total homocysteine (tHcy)-lowering response after an average 4.5 years of 0.8 mg daily folic acid therapy in Chinese hypertensive adults and evaluated effect modification by methylenetetrahydrofolate reductase (MTHFR) C677T genotypes and serum folate levels.

APPROACH AND RESULTS

This analysis included 16 413 participants from the CSPPT, who were randomly assigned to 2 double-blind treatment groups: either 10-mg enalapril+0.8-mg folic acid or 10-mg enalapril, daily and had individual measurements of serum folate and tHcy levels at baseline and exit visits and MTHFR C677T genotypes. Mean baseline tHcy levels were comparable between the 2 treatment groups (14.5±8.5 versus 14.4±8.1 μmol/L; P=0.561). After 4.5 years of treatment, mean tHcy levels were reduced to 12.7±6.1 μmol/L in the enalapril+folic acid group, but almost stayed the same in the enalapril group (14.4±7.9 μmol/L, group difference: 1.61 μmol/L; 11% reduction). More importantly, tHcy lowering varied by MTHFR genotypes and serum folate levels. Compared with CC and CT genotypes, participants with the TT genotype had a more prominent L-shaped curve between tHcy and serum folate levels and required higher folate levels (at least 15 ng/mL) to eliminate the differences in tHcy by genotypes.

CONCLUSIONS

Compared with CC or CT, tHcy in the TT group manifested a heightened L-shaped curve from low to high folate levels, but this difference in tHcy by genotype was eliminated when plasma folate levels reach ≈15 ng/mL or higher. Our data raised the prospect to tailor folic acid therapy according to individual MTHFR C677T genotype and folate status.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00794885.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

Methylenetetrahydrofolate reductase C677T polymorphism and colorectal cancer susceptibility: a meta-analysis

The association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and colorectal cancer (CRC) susceptibility has been researched in numerous studies. However, the results of these studies were controversial. Therefore, the objective of this meta-analysis was to offer a more convincible conclusion about such association with more included studies. Eligible studies published till May 1, 2017 were searched from PubMed, Embase, Web of Science, and CNKI database about such association. Pooled odds ratios (ORs) together with 95% confidence intervals (CIs) were calculated to evaluate such association. And the Begg's funnel plot and Egger's test were applied to assess the publication bias. This meta-analysis contained 37049 cases and 52444 controls from 87 publications with 91 eligible case-control studies. Because of lack of data for a particular genotype in several studies, all the included studies were analysed barely in the dominant model. Originally, there was no association between MTHFR C677T polymorphism and CRC susceptibility (OR =0.99, 95% CI =0.94-1.05). After excluding 13 studies according to their heterogeneity and publication bias, rs1801133 polymorphism was found to reduce the risks of CRC significantly (OR =0.96, 95% CI =0.94-0.99). In the subgroup analysis of ethnicity, there was a significant association in Asians (OR =0.94, 95% CI =0.89-1.00). Furthermore, when stratified by the source of controls and genotyping methods, the positive results were observed in population-based control group (OR =0.97, 95% CI =0.93-1.00) and PCR-restriction fragment length polymorphism (PCR-RFLP) method (OR =0.95, 95% CI =0.91-0.99. The results of the meta-analysis suggested that MTHFR C677T polymorphism was associated with CRC susceptibility, especially in Asian population.

Folic acid intake and folate status and colorectal cancer risk: A systematic review and meta-analysis

BACKGROUND & AIMS

To evaluate the controversies among the studies assessing the association between folic acid intake or folate status and colorectal cancer risk.

METHODS

PubMed, Cochrane library and references of related articles were searched from January 2000 to September 2016. Studies on folic acid intake or folate status and colorectal cancer or adenoma risk were included. Full text review was conducted for potentially eligible studies. Quality assessment was performed. Random-effects meta-analysis was used to estimate risk ratio and 95% Confidence Intervals. Analysis was conducted by Comprehensive Meta-Analysis software.

RESULTS

Folic acid supplement intake showed no significant effect on colorectal cancer risk in meta-analysis of randomized controlled trials, RR: 1.07 (95% CI: 0.86-1.43). The effect on risk was not significant in cohort studies either; RR = 0.96 (95% CI: 0.76-1.21). However, there was significant reduced colorectal cancer risk in total folate intake in cohort studies; 0.71 (95% CI: 0.59-0.86). Odds Ratio was also significantly reduced in case control studies; 0.77 (95% CI: 0.62-0.95). Nevertheless once folate status was measured as Red Blood Cell folate content, no significant effect on colorectal cancer risk was observed; 1.05 (95% CI: 0.85-1.30).

CONCLUSION

The differences in bioavailability and metabolism of synthetic folic acid and natural dietary folate as well as variation in the baseline characteristics of subjects and various methods of folate status assessment might be the main reasons for these controversies. Findings of present study highlight the importance of individualized folic acid supplement intake given the fact that the beneficiary effects of long term folic acid supplementation is not confirmed.

Circulating folate levels and colorectal adenoma: a case-control study and a meta-analysis

BACKGROUND/OBJECTIVES

The relationship between folate and colorectal neoplasia remains controversial. We examined the association between serum folate concentrations and colorectal adenomas in a case-control study of Korean adults and conducted a meta-analysis.

SUBJECTS/METHODS

Our case-control study included 113 pairs of case and control who underwent colonoscopy and provided blood samples. We used multivariable conditional logistic regression models to obtain the odds ratios and 95% confidence interval (CIs). For meta-analysis, we identified the relevant studies by searching the PubMed database up to February 2017, included our case-control study and combined the study-specific relative risks (RRs) using a random-effects model.

RESULTS

In this case-control study, we included 58 men and 55 women with colorectal adenomas and sex and fasting status matched the controls. We did not find any significant association between the serum folate levels and colorectal adenomas in either men or women. For meta-analysis, a total of eleven studies were included in our analysis and classified into two groups; polyp clearance group (PC) for the studies that included participants who underwent endoscopies and had their polyps removed at baseline; and no polyp clearance group (NPC) for the studies that included participants whose histories of endoscopies were unknown or who underwent their first endoscopies. Four PC (1,311 cases and 1,672 non-cases) and eight NPC studies (3,501 cases and 11,347 non-cases) were included. The combined RRs (95% CIs) comparing the bottom with the top categories of circulating folate levels were 1.07 (0.97-1.18) for the NPC group but 1.45 (1.16-1.74) for the PC group.

CONCLUSIONS

Low circulating folate levels were associated with new adenoma formation.

The MTHFR C677T mutation is not a risk factor recognized for HBV-related HCC in a population with a high prevalence of this genetic marker

BACKGROUND

Polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene can affect disease progression in HBV infection. However, the results from different reports are inconsistent. The aim of this study was to investigate the association between the MTHFR C677T polymorphism and the outcome of HBV infection in a Tianjin Han population.

METHODS

TaqMan SNP genotyping was employed to determine the alleles and genotypes of MTHFR C677T in 2511 subjects from various stages of HBV infection and 549 healthy controls.

RESULTS

Of the 3060 subjects, the genotypic frequencies were CT 48.9%, TT 29.3% and CC 21.8%; the allelic frequencies were T 53.8% and C 46.2%. There was no significant difference in genotypic or allelic distribution among the different disease groups. When either healthy subjects or self-limited subjects were used as controls, the TT genotype and the T allele conferred protective effects against hepatocellular carcinoma (HCC) (HCC vs healthy subjects: OR=0.588, 95% CI=0.413-0.836, P=0.003; OR=0.768, 95% CI=0.645-0.915, P=0.003, respectively. HCC vs self-limited subjects: OR=0.598, 95% CI=0.404-0.886, P=0.010; OR=0.772, 95% CI=0.635-0.940, P=0.010, respectively). After sub-stratification by gender, the prevalence of the TT genotype or T allele was the lowest in the male HCC group (TT 23.5%, T 49.8%). The protective effects of the TT genotype and the T allele were observed in male HCC and cirrhotic subjects (HCC vs self-limited subjects: OR=0.470, 95% CI=0.288-0.766, P=0.002; OR=0.681, 95% CI=0.535-0.866, P=0.002, respectively. Liver cirrhosis vs self-limited subjects: OR=0.624, 95% CI=0.392-0.992, P=0.046; OR=0.791, 95% CI=0.627-0.998, P=0.048, respectively), but not in female. When the subjects were stratified according to the clinical features, no statistically significant difference in the genotypic distribution was observed (P>0.05).

CONCLUSIONS

The TT genotype and T allele of MTHFR C677T may confer a protective effect on disease progression to HCC in HBV-infected individuals, especially among male patients, in a population with a high prevalence of this genetic marker.

European Code against Cancer 4th Edition: Alcohol drinking and cancer

Alcohol consumption is the third leading risk factor for disease and mortality in Europe. As evaluated by the International Agency for Research on Cancer (IARC) Monographs, a causal relationship is established for consumption of alcoholic beverages and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colorectum and female breast, even at low and moderate alcohol intakes. The higher the amount of alcohol consumed, the higher the risk of developing cancer. In Europe, an estimated 10% (95% CI: 7%-13%) of all cancer cases in men and 3% (95% CI: 1%-5%) of all cancer cases in women are attributable to alcohol consumption. Several biological mechanisms explain the carcinogenicity of alcohol; among them, ethanol and its genotoxic metabolite, acetaldehyde, play a major role. Taking all this evidence into account, a recommendation of the 4th edition of European Code against Cancer is: "If you drink alcohol of any type, limit your intake. Not drinking alcohol is better for cancer prevention."

European Code against Cancer 4th Edition: Alcohol drinking and cancer

Alcohol consumption is the third leading risk factor for disease and mortality in Europe. The International Agency for Research on Cancer (IARC) Monographs provide strengthened evidence that the consumption of alcoholic beverages is causally associated with cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colorectum and female breast, even for low and moderate alcohol intakes. The risk of cancer increases in a dose-dependent manner, and the higher the amount of alcohol consumed, the higher the risk of developing cancer. Several biological mechanisms explain the carcinogenicity of alcohol; among them, ethanol and its genotoxic metabolite acetaldehyde play a major role. Taking all this evidence into account, a recommendation of the 4th edition of the European Code against Cancer (ECAC) is: "If you drink alcohol of any type, limit your intake. Not drinking alcohol is better for cancer prevention."

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.

5,10-Methylenetetrahydrofolate reductase polymorphisms and colon cancer risk: a meta-analysis

Previous studies investigating the association between 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and colon cancer risk have generated conflicting results. The aim of our meta-analysis was to clarify the precise association. A systematic literature search was conducted to identify all relevant studies. Pooled odds ratio (ORs) with 95% confidence interval (CI) were used to estimate the strength of the association. In this meta-analysis, a total of 13 articles, involving 5,386 cases and 8,017 controls met the inclusion criteria. Overall, a significant association was found between colon cancer risk and the MTHFR C667 polymorphism (TT vs CC+CT: OR=0.79; 95%CI=0.65-0.96; p=0.017). Stratification by ethnicity revealed that MTHFRC667 was associated with colon cancer risk in the non-Asian group (TT vs CC+CT:OR=0.77, 95%CI=0.68-0.89, p=0.000; TT vs CC: OR=0.84, 95%CI=0.73-0.97, p=0.016). Stratification by source of control indicated that MTHFR C667 also correlated with colon cancer risk in the population-based subgroup (TT vs CC: OR=0.85, 95%CI=0.74-0.97, p=0.017; TT vs CC+CT: OR=0.78, 95%CI=0.68-0.89, p=0.000) and hospital-based subgroup (TT vs CC+CT: OR=0.65, 95%CI=0.49-0.86, p=0.003). However, risk was significantly increased for MTHFR A1298C polymorphisms and colon cancer risk in hospital-based studies (C vs A: OR=1.52, 95%CI=1.26-1.83, p=0.000; CC+AC vs AA: OR=1.93, 95%CI=1.47-2.49, p=0.000) but reduced in population-based studies (CC vs AA: OR=0.83, 95%CI=0.70-0.99, p=0.042). In conclusion, the results of our meta-analysis suggest that the MTHFR C667 polymorphism is associated with reduced colon cancer risk, especially for non-Asian populations.

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.

Folate and nutrients involved in the 1-carbon cycle in the pretreatment of patients for colorectal cancer

To assess the ingestion of folate and nutrients involved in the 1-carbon cycle in non-treated patients with colorectal adenocarcinoma in a reference center for oncology in southeastern Brazil. In total, 195 new cases with colorectal adenocarcinoma completed a clinical evaluation questionnaire and a Food Frequency Questionnaire (FFQ). Blood samples from 161 patients were drawn for the assessment of serum folate. A moderate correlation was found between serum concentrations of folate, folate intake and the dietary folate equivalent (DFE) of synthetic supplements. Mulatto or black male patients with a primary educational level had a higher intake of dietary folate. Of patients obtaining folate from the diet alone or from dietary supplements, 11.00% and 0.10%, respectively, had intake below the recommended level. Of the patients using dietary supplements, 35% to 50% showed high levels of folic acid intake. There was a prevalence of inadequacy for vitamins B2, B6 and B12, ranging from 12.10% to 20.18%, while 13.76% to 22.55% of patients were likely to have adequate choline intake. The considerable percentage of patients with folate intake above the recommended levels deserves attention because of the harmful effects that this nutrient may have in the presence of established neoplastic lesions.

Associations of colorectal cancer incidence with nutrient and food group intakes in korean adults: a case-control study

This study aimed to examine the associations between intakes of various nutrients and food groups and colorectal cancer risk in a case-control study among Koreans aged 20 to 80 years. A total of 150 new cases and 116 controls were recruited with subjects' informed consent. Dietary data were collected using the food frequency questionnaire developed and validated by the Korea Centers for Disease Control and Prevention. Multivariate logistic regression models were used to estimate odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for colorectal cancer incidence. High intakes of total lipid (OR_{T3 vs T1} = 4.15, 95% CI: 1.33-12.96, p for trend = 0.034), saturated fatty acid (OR_{T3 vs T1} = 2.96, 95% CI: 1.24-7.04, p for trend = 0.016) and monounsaturated fatty acid (OR_{T3 vs T1} = 3.04, 95% CI: 1.23-7.54, p for trend = 0.018) were significantly associated with increased incidence of colorectal cancer. High dietary fiber (OR_{T3 vs T1} = 0.22, 95% CI: 0.08-0.56, p for trend = 0.002) and vitamin C (OR_{T3 vs T1} = 0.38, 95% CI: 0.14-1.05, p for trend = 0.021) intakes were significantly associated with reduced colorectal cancer incidence. From the food group analysis, bread (OR_{T3 vs T1} = 2.26, 95% CI: 0.96-5.33, p for trend = 0.031), red meat (OR_{T3 vs T1} = 7.33, 95% CI: 2.98-18.06, p for trend < 0.001), milk·dairy product (OR_{T3 vs T1} = 2.42, 95% CI: 1.10-5.31, p for trend = 0.071) and beverage (OR_{T3 vs T1} = 3.17, 95% CI: 1.35-7.48, p for trend = 0.002) intakes were positively associated with colorectal cancer risk. On the other hand, high intake of traditional rice cake (OR_{T3 vs T1} = 0.35, 95% CI: 0.14-0.86, p for trend = 0.024) was linked with lower colorectal cancer incidence. In conclusion, eating a diet high in total lipid, saturated fatty acids and monounsaturated fatty acids is associated with higher incidence of colorectal cancer, whereas a diet high in dietary fiber and vitamin C was found to lower the incidence in Korean adults. Interestingly high traditional rice cake consumption is associated inversely with colorectal cancer incidence, warranting a future study.

Folate-related nutrients, genetic polymorphisms, and colorectal cancer risk: the fukuoka colorectal cancer study

One-carbon metabolism plays an important role in colorectal carcinogenesis. Meta-analyses have suggested protective associations of folate and vitamin B6 intakes with colorectal cancer primarily based on studies in Caucasians, and genetic polymorphisms pertaining to the folate metabolism have been a matter of interest. Less investigated are the roles of methionine synthase (MTR) and thymidylate synthetase (TS) polymorphisms in colorectal carcinogenesis. In a study of 816 cases and 815 community controls in Japan, we investigated associations of dietary intakes of folate, methionine, vitamin B2, vitamin B6, and vitamin B12 with colorectal cancer risk. The associations with MTR 2756A>G, MTRR 66A>G, and TSER repeat polymorphism were examined in 685 cases and 778 controls. Methionine and vitamin B12 intakes were inversely associated with colorectal cancer risk, but the associations were totally confounded by dietary calcium and n-3 fatty acids. The other nutrients showed no association with the risk even without adjustment for calcium and n-3 fatty acids. The TSER 2R allele was dose-dependently associated with an increased risk. The MTR and MTRR polymorphisms were unrelated to colorectal cancer risk. There was no measurable gene-gene or gene-nutrient interaction, but increased risk associated with the TSER 2R allele seemed to be confined to individuals with high folate status. This study does not support protective associations for folate and vitamin B6. The TSER 2R allele may confer an increased risk of colorectal cancer. The role of the TSER polymorphism in colorectal carcinogenesis may differ by ethnicity.

A critical analysis of the relationship between aldehyde dehydrogenases-2 Glu487Lys polymorphism and colorectal cancer susceptibility

Studies investigating the association between genetic polymorphism of aldehyde dehydrogenases-2 (ALDH-2) Glu487Lys and colorectal cancer (CRC) risk have reported conflicting results. Given this uncertainty, we carried out a critical analysis of published case-control studies to derive a more precise estimation of this relationship. Published literature from PubMed, EMBASE and China Knowledge Resource Integrated Database were retrieved, and the literature search was updated in June 2014. Eleven studies comprising 6965 subjects were selected (2300 cases and 4665 controls). Overall, our study showed no statistical significance for CRC risk associated with any of the genetic models of ALDH-2 Glu487Lys polymorphism. When studies were stratified for control source, a decreased risk of CRC for participants with Lys/Lys was observed in population based case-control studies [Lys/Lys vs. (Glu/Lys + Glu/Glu): odds ratio (OR) = 0.57, 95% confidence interval (CI) = 0.38-0.87]. Furthermore, we also confirmed the significant correlation between Glu487Lys polymorphism and the influence on the risk of rectal cancer in males [Glu/Glu vs. (Glu/Lys + Lys/Lys): OR = 1.52, 95%CI = 1.10-2.08]. The combined effects of the two gene polymorphisms [ALDH-2 and alcohol dehydrogenase 1B (ADH-1B)] were also studied. Compared with subjects having ALDH-2 Lys+ with ADH-1B His/His, ORs and 95%CIs for those with ALDH-2 Glu/Glu and ADH-1B His/His was 3.42(0.57-20.38). Similar trends were observed for the other two types of comparisons. Our study supports that ALDH-2 Glu487Lys polymorphism is associated with significant reduced risks of CRC in population-based samples, and of rectal cancer in males.

Polymorphisms in RETN gene and susceptibility to colon cancer in Saudi patients

BACKGROUND AND OBJECTIVES

Resistin is an adipocytokine, which has been studied for its role in insulin resistance and recently in inflammation. Several single-nucleotide polymorphisms (SNPs) have been identified in the human resistin gene (RETN). This study aims to investigate the association of RETN rs1862513 (C-420G) and rs3745367 (G+299A) SNPs with the colon cancer risk in Saudi patients.

DESIGN AND SETTING

This is a case-control study conducted among Saudi adult colon cancer patients recruited from King Abdulaziz Hospital and Oncology Center in Jeddah, Saudi Arabia.

SUBJECTS AND METHODS

In this study, 120 Saudi volunteers (60 colon cancer patients and 60 disease-free controls) were studied. The SNPs were determined by polymerase chain reaction (PCR) and genotyping using PCR- restriction fragment length polymorphism analysis.

RESULTS

In comparing the result obtained for the patient group with that of the controls, colon cancer group displayed different genotype distribution of the RETN C-420G and G+299A SNPs. The study indicated that the SNP-420 heterozygous (CG) genotype (odds ratio [OR]=2.48, 95% CI 1.07-5.74, P=.03) and the SNP +299 heterozygous (GA) genotype (OR=6.5, 95% CI 1.77-24.18, P=.002) significantly increased the risk of colon cancer. A further analysis of the genotype combination of SNPs RETN C-420G and G+299A showed a larger increase in the colon cancer risk.

CONCLUSION

These preliminary results suggested a potential role for RETN C-420G and G+299A polymorphisms in the genetic predisposition to colon cancer disease.

Recent evidence on alcohol and cancer epidemiology

This review presents an overview of the impact of alcohol consumption on cancer risk. Results from the 2009 International Agency for Research on Cancer monograph as well as the most recent meta-analyses and epidemiological studies are considered. Alcohol consumption is one of the most important known risk factors for human cancer and potentially one of the most avoidable factors, but it is increasing worldwide. Ethanol in alcoholic beverages is carcinogenic to humans and causes several cancers (oral cavity, pharynx, larynx, esophagus, colorectum, liver and female breast). Cumulative lifetime consumption, frequency and drinking pattern appear to play a role in risk characterization. While the role of heavy drinking has been long recognized, new evidence suggests that light consumption (up to one drink/day) is also associated with adverse effects. In addition, some genetic polymorphisms interact with alcohol metabolism and may modify its impact.

Nutrition in early life and the programming of adult disease: a review

Foetal development and infancy are life stages that are characterised by rapid growth, development and maturation of organs and systems. Variation in the quality or quantity of nutrients consumed by mothers during pregnancy, or infants during the first year of life, can exert permanent and powerful effects upon developing tissues. These effects are termed 'programming' and represent an important risk factor for noncommunicable diseases of adulthood, including the metabolic syndrome and coronary heart disease. This narrative review provides an overview of the evidence-base showing that indicators of nutritional deficit in pregnancy are associated with a greater risk of type-2 diabetes and cardiovascular mortality. There is also a limited evidence-base that suggests some relationship between breastfeeding and the timing and type of foods used in weaning, and disease in later life. Many of the associations reported between indicators of early growth and adult disease appear to interact with specific genotypes. This supports the idea that programming is one of several cumulative influences upon health and disease acting across the lifespan. Experimental studies have provided important clues to the mechanisms that link nutritional challenges in early life to disease in adulthood. It is suggested that nutritional programming is a product of the altered expression of genes that regulate the cell cycle, resulting in effective remodelling of tissue structure and functionality. The observation that traits programmed by nutritional exposures in foetal life can be transmitted to further generations adds weight the argument that heritable epigenetic modifications play a critical role in nutritional programming.

Association of MTHFR C677T polymorphisms and colorectal cancer risk in Asians: evidence of 12,255 subjects

OBJECTIVES

To investigate the relationship of the MTHFR polymorphisms (C677T) and the risk of CRC by meta-analysis.

METHODS

Relevant literatures concerning the association between the MTHFR C677T polymorphism and the risk of CRC were searched using the electronic database PubMed, EMBASE, Cochrane and China National Knowledge Infrastructure (CNKI). Odds ratio (ORs) and 95 % confidence intervals (CIs) were determined to assess the gene-disease association using fixed or random effect models, according to the heterogeneity among included studies.

RESULTS

The study shows that the MTHFR 677 TT homozygous genotype significantly decreases the risk of CRC in Asians (TT vs. CC: OR = 0.82, 95 % CI 0.73-0.92; TT vs. CT: OR = 0.84, 95 % CI 0.75-0.94; TT vs. CC+TT: OR = 0.83, 95 % CI 0.75-0.93).

CONCLUSION

This meta-analysis indicated that the MTHFR 677 TT homozygous genotype decreased the risk of CRC in Asians, while the MTHFR 677 CT heterozygous genotype did not contribute to CRC susceptibility.

Association of methylenetetrahydrofolate reductase C677T and A1298C polymorphisms with colorectal cancer risk: A meta-analysis

Colorectal cancer (CRC) is one of the most common types of cancer worldwide and a leading cause of cancer-related mortality. This meta-analysis was conducted to determine the effect of methylenetetrahydrofolate reductase (MTHFR) mutants on the risk of CRC. A literature search was conducted on PubMed, Medline and the China National Knowledge Infrastructure (CNKI) databases. Eligible studies were collected based on rigorous criteria of inclusion. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by the fixed- or random-effects model. After all the studies were pooled, the OR of CRC for individuals carrying the MTHFR 677TT genotype, compared to the CC genotype, was 0.89 (95% CI: 0.82-0.97). When analyzed by ethnicity, Asians with the MTHFR 1298CC genotype exhibited a decreased risk of CRC (OR=0.69; 95% CI: 0.54-0.89). In a mixed population, a significantly reduced risk of CRC was observed among carriers of the 677TT (OR=0.86; 95% CI: 0.76-0.96) and the 1298CC (OR=0.82; 95% CI: 0.69-0.98) genotypes, compared to the wild-type homozygous genotype. In the subgroup of colon cancer, the OR of 677TT vs. CC+CT was 0.83 (95% CI: 0.72-0.96) and the OR of 1298CC vs. AA+AC was 0.81 (95% CI: 0.69-0.96). In the rectal cancer subgroup, the OR of 677TT vs. CC+CT was 0.86 (95% CI: 0.77-0.97). Therefore, this meta-analysis suggested that the MTHFR 677T and 1298C alleles were associated with a low risk of CRC.

NQO1 609C>T polymorphism interaction with tobacco smoking and alcohol drinking increases colorectal cancer risk in a Chinese population

BACKGROUND

NAD (P)H:quinone oxidoreductase (NQO1) catalyzes the activation of some environmental procarcinogens present in tobacco smoke or the diet. We conducted a hospital-based case-control study to evaluate the potential association between NQO1 609C>T polymorphisms and colorectal cancer risk in a Chinese population.

METHODS

The study population comprised 672 histologically confirmed colorectal cancer patients and 672 frequency-matched control subjects without cancer or systemic illness. We used PCR restriction fragment length polymorphism-based methods for genotyping analyses and unconditional logistic regression model for statistical evaluations.

RESULTS

The risk of colorectal cancer increased with the level of smoking and decreased with the consumption of tea, fresh fruits, and vegetables. In addition, we found that the NQO1 609 CT and TT genotypes were associated with an increased risk of colorectal cancer (CT: adjusted OR=2.02, 95% CI=1.55-2.57; TT: adjusted OR=2.51, 95% CI=1.82-3.47), compared with the CC genotype. Moreover, NQO1 609C>T appeared to have a multiplicative joint effect with both tobacco smoking and alcoholic drinking (P for multiplicative interactions were 0.0001 and 0.013, respectively) on colorectal cancer risk.

CONCLUSION

Our findings suggest that the NQO1 609C>T polymorphism plays an important role in the development of colorectal cancer in the Chinese population, which is strengthened by alcohol drinking or tobacco smoking.

Folate, alcohol, and liver disease

Alcoholic liver disease (ALD) is typically associated with folate deficiency, which is the result of reduced dietary folate intake, intestinal malabsorption, reduced liver uptake and storage, and increased urinary folate excretion. Folate deficiency favors the progression of liver disease through mechanisms that include its effects on methionine metabolism with consequences for DNA synthesis and stability and the epigenetic regulation of gene expression involved in pathways of liver injury. This paper reviews the pathogenesis of ALD with particular focus on ethanol-induced alterations in methionine metabolism, which may act in synergy with folate deficiency to decrease antioxidant defense as well as DNA stability while regulating epigenetic mechanisms of relevant gene expressions. We also review the current evidence available on potential treatments of ALD based on correcting abnormalities in methionine metabolism and the methylation regulation of relevant gene expressions.

Folate Intake, MTHFR Polymorphisms, and the Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis

Background. The objective was to determine whether relationships exist between the methylene-tetrahydrofolate reductase (MTHFR) polymorphisms and risk of colorectal cancer (CRC) and examine whether the risk is modified by level of folate intake. Methods. MEDLINE, Embase, and SCOPUS were searched to May 2012 using the terms "folic acid," "folate," "colorectal cancer," "methylenetetrahydrofolate reductase," "MTHFR." Observational studies were included which (1) assessed the risk of CRC for each polymorphism and/or (2) had defined levels of folate intake for each polymorphism and assessed the risk of CRC. Results. From 910 references, 67 studies met our criteria; hand searching yielded 10 studies. The summary risk estimate comparing the 677CT versus CC genotype was 1.02 (95% CI 0.95-1.10) and for 677TT versus CC was 0.88 (95% CI 0.80-0.96) both with heterogeneity. The summary risk estimates for A1298C polymorphisms suggested no reduced risk. The summary risk estimate for high versus low total folate for the 677CC genotype was 0.70 (95% CI 0.56-0.89) and the 677TT genotype 0.63 (95% CI 0.41-0.97). Conclusion. These results suggest that the 677TT genotype is associated with a reduced risk of developing CRC, under conditions of high total folate intake, and this associated risk remains reduced for both MTHFR 677 CC and TT genotypes.

Quantitative assessment of the association between MTHFR C677T polymorphism and colorectal cancer risk in East Asians

A great number of studies regarding the association between MTHFR C677T polymorphism and risk of colorectal cancer (CRC) in East Asians were published, but the results were inconsistent. Thus, a meta-analysis was performed to investigate the association. PubMed, Embase, and CBM databases were searched for eligible publications. Pooled odds ratios (ORs) with 95 % confidence intervals (95 % CIs) were calculated using random or fixed effect models. Finally, 24 case-control studies with a total of 7,230 CRC cases and 9,285 controls were included. Meta-analyses of a total of 24 studies showed there was a statistically significant association between MTHFR C677T polymorphism and decreased CRC risk in East Asians under four genetic models (T versus C, OR = 0.92, 95 % CI 0.85-0.99; TT versus CC, OR = 0.80, 95 % CI 0.69-0.94; TT versus CT/CC, OR = 0.82, 95 % CI 0.71-0.95; TT/CT versus CC, OR = 0.92, 95 % CI 0.86-0.98). The cumulative meta-analyses for the allele contrast (T versus C), homozygote (TT versus CC), dominant (TT/CT versus CC), and recessive (TT versus CT/CC) models all showed a trend of more obvious association as information accumulated by year. Subgroup analyses by country further identified this association in Korea and Japan. This meta-analysis suggests that MTHFR C677T polymorphism is associated with decreased risk of colorectal cancer in East Asians, and MTHFR 677T variant has a protective effect on colorectal cancer.

MTHFR polymorphisms and ovarian cancer risk: a meta-analysis

The C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase (MTHFR) have been reported to alter the risk of ovarian cancer. However, the results are still inconclusive. For better understanding of the effect of these two polymorphisms on ovarian cancer risk, a meta-analysis was performed. An extensive search was performed to identify all case-control studies investigating such association. The strength of association between these two polymorphisms and ovarian cancer risk was assessed by odds ratio (OR) with the corresponding 95 % confidence interval (95 % CI). 3,496 cases and 3,631 controls for C677T polymorphism and 3,280 cases and 3,346 controls for A1298C polymorphism were included in this meta-analysis. The results suggested that there were no significant associations between C677T and A1298C polymorphisms and ovarian cancer risk in overall comparisons in all genetic models (For C677T: TT vs. CC: OR = 0.94, 95 % CI = 0.71-1.24, P = 0.65; CT vs. CC: OR = 1.03, 95 % CI = 0.93-1.14, P = 0.57; TT/CT vs. CC: OR = 1.01, 95 % CI = 0.88-1.16, P = 0.87; TT vs.

CC/CT

OR = 0.93, 95 % CI = 0.72-1.20, P = 0.58. For A1298C: CC vs. AA: OR = 1.05, 95 % CI = 0.88-1.25, P = 0.65; CA vs. AA: OR = 0.98, 95 % CI = 0.88-1.08, P = 0.66; CC/CA vs. AA: OR = 0.99, 95 % CI = 0.90-1.09, P = 0.85; CC vs. AA/CA: OR = 1.06, 95 % CI = 0.90-1.26, P = 0.46). Subgroup analysis based on ethnicities and influence analysis did not perturb the results. In conclusion, the results of this meta-analysis indicate that the MTHFR C677T and A1298C polymorphisms are not associated with ovarian cancer risk, especially in Caucasians.