Using surrogate biomarkers to improve measurement error models in nutritional epidemiology.

Nutritional epidemiology relies largely on self-reported measures of dietary intake, errors in which give biased estimated diet-disease associations. Self-reported measurements come from questionnaires and food records. Unbiased biomarkers are scarce; however, surrogate biomarkers, which are correlated with intake but not unbiased, can also be useful. It is important to quantify and correct for the effects of measurement error on diet-disease associations. Challenges arise because there is no gold standard, and errors in self-reported measurements are correlated with true intake and each other. We describe an extended model for error in questionnaire, food record, and surrogate biomarker measurements. The focus is on estimating the degree of bias in estimated diet-disease associations due to measurement error. In particular, we propose using sensitivity analyses to assess the impact of changes in values of model parameters which are usually assumed fixed. The methods are motivated by and applied to measures of fruit and vegetable intake from questionnaires, 7-day diet diaries, and surrogate biomarker (plasma vitamin C) from over 25000 participants in the Norfolk cohort of the European Prospective Investigation into Cancer and Nutrition. Our results show that the estimated effects of error in self-reported measurements are highly sensitive to model assumptions, resulting in anything from a large attenuation to a small amplification in the diet-disease association. Commonly made assumptions could result in a large overcorrection for the effects of measurement error. Increased understanding of relationships between potential surrogate biomarkers and true dietary intake is essential for obtaining good estimates of the effects of measurement error in self-reported measurements on observed diet-disease associations.

MLH1 promoter methylation, diet, and lifestyle factors in mismatch repair deficient colorectal cancer patients from EPIC-Norfolk.

There is conflicting evidence for the role diet and lifestyle play in the development of mismatch repair (MMR)-deficient colorectal cancers (CRC). In this study, associations between MMR deficiency, clinicopathological characteristics, and dietary and lifestyle factors in sporadic CRC were investigated. Tumor samples from 185 individuals in the EPIC-Norfolk study were analyzed for MLH1 gene promoter methylation and microsatellite instability (MSI). Dietary and lifestyle data were collected prospectively using 7-day food diaries (7dd) and questionnaires. MMR-deficient tumor cases (MLH1 promoter methylation positive, MSI-H) were more likely to be female, older at diagnosis, early Dukes' stage (A/B), and proximal in location (MSI-H P = 0.03, 0.03, 0.02, and 0.001, respectively). Tumors with positive MLH1 promoter methylation (>20%) were associated with poor differentiation (P = 0.03). Low physical activity was associated with cases without MSI (P = 0.05). MMR deficiency was not significantly associated with cigarette smoking or alcohol, folate, fruit, vegetable, or meat consumption. We conclude that MMR-deficient tumors represent a distinct subset of sporadic CRC that are proximal in location, early Dukes' stage, and poorly differentiated, in cases that are female and older at diagnosis. There is no overall role for diet and lifestyle in MMR status in CRC, consistent with age-related susceptibility to MLH1 promoter methylation.

Menopausal hormone therapy and risk of colorectal cancer in the European Prospective Investigation into Cancer and Nutrition.

Menopausal hormone therapy (HT) may influence colorectal cancer risk. A total of 136,275 postmenopausal women from the European Prospective Investigation into Cancer and Nutrition were followed for an average of 9 years, during which time 1,186 colorectal cancers were diagnosed. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models stratified by center and age, and adjusted for body mass index, smoking, diabetes, physical activity and alcohol consumption. Compared to never use of HT at study enrollment, current use of estrogen-only (HR, 1.02; 95% CI, 0.79-1.31) or estrogen plus progestin (HR, 0.94; 95% CI, 0.77-1.14) was not significantly associated with the risk of colorectal cancer, and these associations did not vary by recency, duration, route of administration, regimen or specific constituent of HT. Our results show no significant association of estrogen-only or estrogen plus progestin therapy with colorectal cancer risk.

SMAD7 and MGMT genotype variants and cancer incidence in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk Study.

PURPOSE: The SMAD7 gene was recently identified to be associated with colorectal cancer risk. Smad7 protein is a known inhibitor of TGF-ß signalling pathway which has a prominent role in tumorigenesis. MGMT gene regulates the direct damage reversal repair pathway, preventing DNA damage and potential cancer development. This exploratory study aims to investigate the association between SMAD7 (rs4464148, rs4939827) and MGMT (rs12917, rs2308321) genotype variants, and all-cancer incidence. METHODS: Our study population was a sub-cohort of the EPIC-Norfolk study, a prospective cohort of approximately 25,000 men and women aged 40-79. Between recruitment 1993-1997 and follow-up to 2006, 192 incident cases and 1155 non-cases with genotype data were identified. Baseline 7-day food diary and health/lifestyle questionnaire data were analysed. RESULTS: SMAD7 rs4464148 variant genotype was associated with increased cancer incidence [HR=1.34, 95%CI=1.00-1.80] but no overall association for SMAD7 rs4939827 or MGMT genotypes. Participants with variant genotypes in both SMAD7 SNPs had a higher cancer incidence compared to those without any (HR=2.74, 95%CI=1.10-6.79) (P=0.03; P(trend)=0.01). Amongst the younger age participants (

Genetic variants influencing circulating lipid levels and risk of coronary artery disease.

OBJECTIVE: Genetic studies might provide new insights into the biological mechanisms underlying lipid metabolism and risk of CAD. We therefore conducted a genome-wide association study to identify novel genetic determinants of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides. METHODS AND RESULTS: We combined genome-wide association data from 8 studies, comprising up to 17 723 participants with information on circulating lipid concentrations. We did independent replication studies in up to 37 774 participants from 8 populations and also in a population of Indian Asian descent. We also assessed the association between single-nucleotide polymorphisms (SNPs) at lipid loci and risk of CAD in up to 9 633 cases and 38 684 controls. We identified 4 novel genetic loci that showed reproducible associations with lipids (probability values, 1.6×10(-8) to 3.1×10(-10)). These include a potentially functional SNP in the SLC39A8 gene for HDL-C, an SNP near the MYLIP/GMPR and PPP1R3B genes for LDL-C, and at the AFF1 gene for triglycerides. SNPs showing strong statistical association with 1 or more lipid traits at the CELSR2, APOB, APOE-C1-C4-C2 cluster, LPL, ZNF259-APOA5-A4-C3-A1 cluster and TRIB1 loci were also associated with CAD risk (probability values, 1.1×10(-3) to 1.2×10(-9)). CONCLUSIONS: We have identified 4 novel loci associated with circulating lipids. We also show that in addition to those that are largely associated with LDL-C, genetic loci mainly associated with circulating triglycerides and HDL-C are also associated with risk of CAD. These findings potentially provide new insights into the biological mechanisms underlying lipid metabolism and CAD risk.

Meat, poultry and fish and risk of colorectal cancer: pooled analysis of data from the UK dietary cohort consortium.

OBJECTIVE: Some but not all epidemiological studies have reported that high intakes of red and processed meat are associated with an increased risk of colorectal cancer. In the UK Dietary Cohort Consortium, we examined associations of meat, poultry and fish intakes with colorectal cancer risk using standardised individual dietary data pooled from seven UK prospective studies. METHODS: Four- to seven-day food diaries were analysed, disaggregating the weights of meat, poultry and fish from composite foods to investigate dose-response relationships. We identified 579 cases of colorectal cancer and matched with 1,996 controls on age, sex and recruitment date. Conditional logistic regression models were used to estimate odds ratios for colorectal cancer associated with meat, poultry and fish intakes, adjusting for relevant covariables. RESULTS: Disaggregated intakes were moderately low, e.g. mean red meat intakes were 38.2 g/day among male and 28.7 g/day among female controls. There was little evidence of association between the food groups examined and risk for colorectal cancer: Odds ratios (95% confidence intervals) for a 50 g/day increase were 1.01 (0.84-1.22) for red meat, 0.88 (0.68-1.15) for processed meat, 0.97 (0.84-1.12) for red and processed meat combined, 0.80 (0.65-1.00) for poultry, 0.92 (0.70-1.21) for white fish and 0.89 (0.70-1.13) for fatty fish. CONCLUSIONS: This study using pooled data from prospective food diaries, among cohorts with low to moderate meat intakes, shows little evidence of association between consumption of red and processed meat and colorectal cancer risk.

Lifestyle factors and p53 mutation patterns in colorectal cancer patients in the EPIC-Norfolk study.

The tumour suppressor p53 is one of the most commonly altered genes in colorectal cancer (CRC) development. Genetic alterations in p53 may therefore be associated with postulated lifestyle risk factors for CRC, such as red meat consumption. In the European Prospective Investigation into Cancer and Nutrition-Norfolk study, we examined whether detailed estimates of dietary and lifestyle factors measured at baseline related to later development of p53 mutations in CRCs. After 10-year follow-up, there were 185 incident CRCs of which 34% had somatic p53 mutations (p53+). We observed significantly higher mean intakes of alcohol, total meat and red meat, in the group with p53 mutations and advanced Dukes' stage disease (daily alcohol intake was 7 and 12 g for p53- and p53+ cases, respectively, P = 0.04; daily total meat intake was 69 and 100 g for p53- and p53+ cases, respectively, P = 0.03 and daily red meat intake was 39 and 75 g for p53- and p53+ cases, respectively, P = 0.01). Each 50 g/day increment in total meat intake was associated with having p53 mutations in cases with advanced Dukes' stages [odds ratio (OR): 3.43, 95% confidence interval (CI): 1.47-7.96]. Similarly, each 50 g/day increment in red meat intake was also significantly associated with having consistent p53 mutations in cases with advanced Dukes' stages (OR: 2.42, 95% CI: 1.18-4.96). These effects of total meat or red meat intake and advanced Dukes' stages were independent of age, sex, body mass index, smoking and alcohol intake. Furthermore, P values for interaction between daily total meat or red meat intake and Dukes' stages were statistically significant in multivariable models (Pinteraction < 0.001). Our results suggest that p53 mutations accelerate progression of CRC to advanced Dukes' stage in association with higher meat especially red meat intakes.

Dietary, lifestyle and clinicopathological factors associated with BRAF and K-ras mutations arising in distinct subsets of colorectal cancers in the EPIC Norfolk study.

BACKGROUND: BRAF and K-ras proto-oncogenes encode components of the ERK signalling pathway and are frequently mutated in colorectal cancer. This study investigates the associations between BRAF and K-ras mutations and clinicopathological, lifestyle and dietary factors in colorectal cancers. METHODS: 186 adenocarcinomas and 16 adenomas from the EPIC Norfolk study were tested for BRAF and K-ras mutations. Diet and lifestyle data were collected prospectively using seven day food diaries. RESULTS: BRAF V600E mutation was found in 15.6% of colorectal cancers but at higher frequencies in cancers with proximal location, poor differentiation and microsatellite instability (MSI) (all p < 0.001). K-ras mutation (mostly in codons 12 and 13) was found in 22.0% of colorectal cancers but at higher frequencies in cancers of more advanced Dukes' stage (p = 0.001), microsatellite stable (MSS) status (p = 0.002) and in individuals with lower blood high-density lipoprotein concentrations (p = 0.04). Analysis of dietary factors demonstrated no link between BRAF mutation and any specific dietary constituent, however, K-ras mutation was found at higher frequencies in individuals with higher white meat consumption (p < 0.001). Further analysis of specific mutation type demonstrated that G to A transitions in K-ras were observed at higher frequencies in individuals consuming lower amounts of fruit (p = 0.02). CONCLUSION: These data support the model of BRAF and K-ras mutations arising in distinct colorectal cancer subsets associated with different clinicopathological and dietary factors, acting as mutually exclusive mechanisms of activation of the same signalling pathway.

MGMT Ile143Val polymorphism, dietary factors and the risk of breast, colorectal and prostate cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study.

O(6)-Methylguanine-DNA methyltransferase (MGMT) repairs DNA damage caused by alkylating agents including N-nitroso compounds from diet. MGMT Ile143Val polymorphism may lead to less DNA damage repair and increased cancer risk depending on the environmental exposures. We investigated interactions between dietary factors and the MGMT Ile143Val polymorphism in relation to breast, colorectal and prostate cancer risk. There were 276/1498, 273/2984 and 312/1486 cases/controls for the breast, colorectal and prostate cancer studies respectively; all nested within the EPIC-Norfolk study, a prospective cohort of approximately 25,000 men and women aged 40-79. Baseline 7-day food diary data were collected for dietary assessment. MGMT Ile143Val polymorphism was not overall associated with breast, colorectal and prostate cancer risk. There was a significant interaction between this polymorphism and intake of red and processed meat on colorectal cancer risk (P(interaction)=0.04) suggesting an increased risk among carriers of the variant genotype compared to the MGMT Ile143Ile common genotype. A lower colorectal cancer risk was seen with higher intake of vitamin E and carotene among the variant genotype group but not in the common genotype group (P(interaction)=0.009 and P(interaction)=0.005 for vitamin E and carotene, respectively). A higher prostate cancer risk was seen with higher alcohol intake among the variant genotype (OR=2.08, 95% CI=1.21-3.57, P(interaction)=0.0009) compared to the common genotype with lower alcohol intake. In this UK population, the MGMT Ile143Val polymorphism was not overall associated with breast, colorectal and prostate cancer risk. There was evidence for this polymorphism playing a role in modulating the risk of prostate cancer in presence of alcohol. For colorectal cancer, the MGMT Ile143Val polymorphism may confer increased or decreased risk depending on the dietary exposure.

Effect of dietary meat and fish on endogenous nitrosation, inflammation and genotoxicity of faecal water.

N-3 polyunsaturated fatty acids have been associated with reduced colon tumorigenesis. However, their association with colorectal cancer incidence is not conclusive. We investigated the influence of isocaloric replacement of red meat with fatty fish on endogenous nitrosation, inflammation and genotoxicity of faecal water in apparently healthy human volunteers on controlled diets. Fourteen volunteers consumed a high red meat, a combined red meat/fish and a high fish diet for 8 days each. Faecal homogenates were analysed for haem, nitroso compounds (NOC) and calprotectin and associated supernatants for genotoxicity. Both faecal NOC and haem excretion decreased with more fish and less meat in the diet. Nitrosyl iron (FeNO) was the main contributor to total NOC on all diets. The proportion of other NOC increased with more fish and less meat in the diet (P = 0.01), resulting in a non-statistically significant decrease in the proportion of FeNO on the fish diet. There was no statistically significant difference in faecal calprotectin (P = 0.54) and faecal water-induced DNA strand breaks and oxidized purines and pyrimidines between the diets (P > 0.36). Increasing fish intake and reducing the intake of red meat does not seem to have an effect on inflammation and faecal water-induced (oxidative) DNA damage; however, it does reduce the formation of mutagenic and potentially carcinogenic NOC and may as such beneficially affect colorectal risk.

Cumulative effects and predictive value of common obesity-susceptibility variants identified by genome-wide association studies.

BACKGROUND: Large-scale genome-wide association studies have identified 12 genetic loci that are robustly associated with body mass index (BMI). OBJECTIVES: We examined associations and compared effect sizes of these newly identified obesity susceptibility loci with various anthropometric traits and assessed their cumulative effects and predictive value for obesity risk. DESIGN: We genotyped 12 single nucleotide polymorphisms (SNPs) from each locus in 20,431 individuals (age: 39-79 y) from the population-based European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohort. General linear model and logistic regression were used to examine associations, and the area under the receiver operating characteristic curve (AUC) was used to assess the predictive value of these variants for obesity risk. RESULTS: Effect sizes of the risk alleles ranged between 0.058 and 0.329 for BMI (in kg/m(2)), between 0.094 and 0.866 kg for weight, and between 0.085 and 0.819 cm for waist circumference, with rs1121980 (FTO locus) showing the largest effect. Risk alleles of rs7132908 (FAIM2 locus) and rs17782313 (MC4R locus) were also associated with taller height. On average, each additional risk allele was associated with increases of 0.149 in BMI (P = 1.54 x 10(-22)), 0.444 kg in body weight (P = 9.88 x 10(-22)), and 0.357 cm in waist circumference (P = 1.10 x 10(-18)) and 10.8% (P = 9.83 x 10(-16)) and 5.5% (P = 3.38 x 10(-10)) increased risks of obesity and overweight, respectively. All SNPs combined explained 0.9% of BMI variation, with an AUC of 0.574 (95% CI: 0.559, 0.590) for prediction of obesity. CONCLUSIONS: Common variants for BMI have small effects on obesity measures and show different association patterns with anthropometric traits, with the largest effect shown for the FTO locus. These variants have cumulative effects, yet their predictive value for obesity risk is limited.

Baseline alcohol consumption, type of alcoholic beverage and risk of colorectal cancer in the European Prospective Investigation into Cancer and Nutrition-Norfolk study.

Excessive alcohol consumption has been associated with increased risk of colorectal cancer (CRC). However, the effect of modest alcohol consumption or of particular types of beverages on CRC risk remains unclear. We examined whether consumption of total alcohol or specific types of alcoholic beverages relate to overall or site-specific CRC risk in a prospective population study of 24,244 participants and 407 incident CRC cases after 11 years of follow-up. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. Consumption of specific alcoholic beverages at baseline was collected using a detailed health and lifestyle questionnaire. Total alcohol consumption was not associated with CRC risk before or after adjustment for age, sex, weight, height, and smoking status (HR: 0.80, 95% CI: 0.51-1.26 for alcohol consumption of > or =21 units/week compared with non-drinkers), and further adjustment for education level, exercise, family history of CRC, and dietary factors did not significantly alter the risk estimates (HR: 0.70, 95% CI: 0.44-1.13). No significant associations were observed between consumption of specific alcoholic beverages (beer, sherry, or spirits) and CRC risk when compared with non-drinkers after adjustment for lifestyle and dietary factors. Daily consumption of > or =1 unit of wine appeared inversely related to CRC risk (HR: 0.61, 95% CI: 0.40-0.94). No evidence was found for sex-specific relationships, and further exclusion of cases incident within 3 years of baseline did not change the associations observed. In this population-based UK cohort, we did not find any significant adverse effect of alcohol over the moderate range of intake on colorectal cancer risk.