Association of variants in the PCSK1 gene with obesity in the EPIC-Norfolk study.

Recently, the rs6232 (N221D) and rs6235 (S690T) SNPs in the PCSK1 gene were associated with obesity in a meta-analysis comprising more than 13 000 individuals of European ancestry. Each additional minor allele of rs6232 or rs6235 was associated with a 1.34- or 1.22-fold increase in the risk of obesity, respectively. So far, only one relatively small study has aimed to replicate these findings, but could not confirm the association of the rs6235 SNP and did not study the rs6232 variant. In the present study, we examined the associations of the rs6232 and rs6235 SNPs with obesity in a population-based cohort consisting of 20 249 individuals of European descent from Norfolk, UK. Logistic regression and generalized linear models were used to test the associations of the risk alleles with obesity and related quantitative traits, respectively. Neither of the SNPs was significantly associated with obesity, BMI or waist circumference under the additive genetic model (P > 0.05). However, we observed an interaction between rs6232 and age on the level of BMI (P = 0.010) and risk of obesity (P = 0.020). The rs6232 SNP was associated with BMI (P = 0.021) and obesity (P = 0.022) in the younger individuals [less than median age (59 years)], but not among the older age group (P = 0.81 and P = 0.68 for BMI and obesity, respectively). In conclusion, our data suggest that the PCSK1 rs6232 and rs6235 SNPs are not major contributors to common obesity in the general population. However, the effect of rs6232 may be age-dependent.

No evidence that social stress is associated with breast cancer incidence.

Women commonly attribute the experience of stress as a contributory cause of breast cancer. The purpose of this study is to investigate the associations between a history of social stress and breast cancer risk. A total of 11,467 women with no prior history of breast cancer, participants in the European Prospective Investigation into Cancer (EPIC)-Norfolk population-based prospective cohort study, completed a comprehensive assessment of lifetime social adversity exposure. Summary measures of social adversity were defined according to difficult circumstances in childhood, stressful life events and longer-term difficulties in adulthood, derived measures representing the subjective 'impact' of life events and associated 'stress adaptive capacity', and perceived stress over a 10-year period. Incident breast cancers were identified through linkage with cancer registry data. During 102,514 (median 9) person-years of follow-up, 313 incident breast cancers were identified. No associations were observed between any of the summary social adversity measures and subsequent breast cancer risk, with or without adjustment for age, menopausal status, parity, use of menopausal hormones, age at menarche, age at first birth, family history of breast cancer, physical activity, social class, body mass index, height, and alcohol intake. This study found no evidence that social stress exposure or individual differences in its experience are associated with the development of breast cancer. These findings may aid strategies designed to meet the psychosocial and emotional needs of breast cancer survivors and may be interpreted in a positive way in the context of commonly voiced beliefs that the experience of stress is a contributory cause of their disease.

Optimizing immunoslot blot assays and application to low DNA adduct levels using an amplification approach.

Immunoslot blot assays have been used for the analysis of many DNA adducts, but problems are frequently encountered in achieving reproducible results. Each step of the assay was examined systematically, and it was found that the major problems are in the DNA fragmentation step and the use of the manifold apparatus. Optimization was performed on both the malondialdehyde-deoxyguanosine (M(1)dG) adduct and the O(6)-carboxymethyl-deoxyguanosine (O(6)CMdG) adduct to demonstrate the applicability to other DNA adducts. Blood samples from the European Prospective Investigation on Cancer (EPIC) study (n = 162) were analyzed for M(1)dG adducts, and the data showed no correlation with adduct levels in other tissues, indicating that the EPIC blood samples were not useful for studying M(1)dG adducts. Blood samples from a processed meat versus vegetarian diet intervention (n = 6) were analyzed for O(6)CMdG, and many were below the limit of detection. The reduction of background adduct levels in standard DNA was investigated using chemical and whole genome amplification approaches. The latter gave a sensitivity improvement of 2.6 adducts per 10(7) nucleotides for the analysis of O(6)CMdG. Subsequent reanalysis for O(6)CMdG showed a weakly significant increase in O(6)CMdG on the processed meat diet compared with the vegetarian diet, demonstrating that further studies are warranted.

A single nucleotide polymorphism in the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene ( HMGCR) influences the serum triacylglycerol relationship with dietary fat and fibre in the European Prospective Investigation into Cancer and Nutrition in Norfolk (EPIC-Norfolk) study.

The objective of the present study was to investigate the influence of the single nucleotide polymorphism (rs17238540) at the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene (HMGCR) on the relationship between serum lipids and dietary fat and fibre (NSP). FFQ and pyrosequencing were used to assess cross-sectional dietary intake and HMGCR genotype in a population study with data for serum lipids available. Genotype frequencies and allele distributions for 23 011 participants were: TT 95.65 %, TG 4.29 % and GG 0.06 %; T 97.8 % and G 2.2 %. In regression analyses, the TG+GG group showed a significant positive relationship between TAG and SFA intake (+0.11 (95 % CI 0.02, 0.20) mmol TAG/l; P = 0.017; per 3 % SFA energy increase) while the TT individuals showed no change in the TAG levels related to SFA intake ( - 0.0007 (95 % CI - 0.02, 0.02) mmol TAG/l; P = 0.99). TG+GG individuals showed an inverse relationship between TAG and fibre intake higher ( - 0.14 (95 % CI - 0.22, - 0.05) mmol TAG/l than the TT group ( - 0.04 (95 % CI - 0.06, - 0.02) mmol TAG/l). In both cases the respective coefficient regressions of TAG were different between the genotype groups (Z = 2.27, P = 0.023 for SFA intake; Z = 2.19, P = 0.029 for fibre intake). Individuals carrying the G allele may show a greater response in lower TAG levels with reduced SFA intake and increased fibre intake compared with those homozygous for the T allele. The effectiveness of different dietary interventions to control serum lipids may vary according to HMGCR genotype.

Effect of processed and red meat on endogenous nitrosation and DNA damage.

Haem in red meat (RM) stimulates the endogenous production of mutagenic nitroso compounds (NOC). Processed (nitrite-preserved red) meat additionally contains high concentrations of preformed NOC. In two studies, of a fresh RM versus a vegetarian (VEG) diet (six males and six females) and of a nitrite-preserved red meat (PM) versus a VEG diet (5 males and 11 females), we investigated whether processing of meat might increase colorectal cancer risk by stimulating nitrosation and DNA damage. Meat diets contained 420 g (males) or 366 g (females) meat/per day. Faecal homogenates from day 10 onwards were analysed for haem and NOC and associated supernatants for genotoxicity. Means are adjusted for differences in male to female ratios between studies. Faecal NOC concentrations on VEG diets were low (2.6 and 3.5 mmol/g) but significantly higher on meat diets (PM 175 +/- 19 nmol/g versus RM 185 +/- 22 nmol/g; P = 0.75). The RM diet resulted in a larger proportion of nitrosyl iron (RM 78% versus PM 54%; P < 0.0001) and less nitrosothiols (RM 12% versus PM 19%; P < 0.01) and other NOC (RM 10% versus PM 27%; P < 0.0001). There was no statistically significant difference in DNA breaks induced by faecal water (FW) following PM and RM diets (P = 0.80). However, PM resulted in higher levels of oxidized pyrimidines (P < 0.05). Surprisingly, VEG diets resulted in significantly more FW-induced DNA strand breaks than the meat diets (P < 0.05), which needs to be clarified in further studies. Meats cured with nitrite have the same effect as fresh RM on endogenous nitrosation but show increased FW-induced oxidative DNA damage.

Biomarker-calibrated energy and protein consumption and increased cancer risk among postmenopausal women.

The authors previously reported equations, derived from the Nutrient Biomarker Study within the Women's Health Initiative, that produce calibrated estimates of energy, protein, and percentage of energy from protein consumption from corresponding food frequency questionnaire estimates and data on other factors, such as body mass index, age, and ethnicity. Here, these equations were applied to yield calibrated consumption estimates for 21,711 women enrolled in the Women's Health Initiative dietary modification trial comparison group and 59,105 women enrolled in the observational study. These estimates were related prospectively to total and site-specific invasive cancer incidence (1993-2005). In combined cohort analyses that do not control for body mass, uncalibrated energy was not associated with total cancer incidence or site-specific cancer incidence for most sites, whereas biomarker-calibrated energy was positively associated with total cancer (hazard ratio = 1.18, 95% confidence interval: 1.10, 1.27, for 20% consumption increase), as well as with breast, colon, endometrial, and kidney cancer (respective hazard ratios of 1.24, 1.35, 1.83, and 1.47). Calibrated protein was weakly associated, and calibrated percentage of energy from protein was inversely associated, with total cancer. Calibrated energy and body mass index associations were highly interdependent. Implications for the interpretation of nutritional epidemiology studies are described.

Cigarette smoking and pancreatic cancer: a pooled analysis from the pancreatic cancer cohort consortium.

Smoking is an established risk factor for pancreatic cancer; however, detailed examination of the association of smoking intensity, smoking duration, and cumulative smoking dose with pancreatic cancer is limited. The authors analyzed pooled data from the international Pancreatic Cancer Cohort Consortium nested case-control study (1,481 cases, 1,539 controls). Odds ratios and 95% confidence intervals were calculated by using unconditional logistic regression. Smoking intensity effects were examined with an excess odds ratio model that was linear in pack-years and exponential in cigarettes smoked per day and its square. When compared with never smokers, current smokers had a significantly elevated risk (odds ratio (OR) = 1.77, 95% confidence interval (CI): 1.38, 2.26). Risk increased significantly with greater intensity (> or =30 cigarettes/day: OR = 1.75, 95% CI: 1.27, 2.42), duration (> or =50 years: OR = 2.13, 95% CI: 1.25, 3.62), and cumulative smoking dose (> or =40 pack-years: OR = 1.78, 95% CI: 1.35, 2.34). Risk more than 15 years after smoking cessation was similar to that for never smokers. Estimates of excess odds ratio per pack-year declined with increasing intensity, suggesting greater risk for total exposure delivered at lower intensity for longer duration than for higher intensity for shorter duration. This finding and the decline in risk after smoking cessation suggest that smoking has a late-stage effect on pancreatic carcinogenesis.

Biomarkers in nutritional epidemiology: applications, needs and new horizons.

Modern epidemiology suggests a potential interactive association between diet, lifestyle, genetics and the risk of many chronic diseases. As such, many epidemiologic studies attempt to consider assessment of dietary intake alongside genetic measures and other variables of interest. However, given the multi-factorial complexities of dietary exposures, all dietary intake assessment methods are associated with measurement errors which affect dietary estimates and may obscure disease risk associations. For this reason, dietary biomarkers measured in biological specimens are being increasingly used as additional or substitute estimates of dietary intake and nutrient status. Genetic variation may influence dietary intake and nutrient metabolism and may affect the utility of a dietary biomarker to properly reflect dietary exposures. Although there are many functional dietary biomarkers that, if utilized appropriately, can be very informative, a better understanding of the interactions between diet and genes as potentially determining factors in the validity, application and interpretation of dietary biomarkers is necessary. It is the aim of this review to highlight how some important biomarkers are being applied in nutrition epidemiology and to address some associated questions and limitations. This review also emphasizes the need to identify new dietary biomarkers and highlights the emerging field of nutritional metabonomics as an analytical method to assess metabolic profiles as measures of dietary exposures and indicators of dietary patterns, dietary changes or effectiveness of dietary interventions. The review will also touch upon new statistical methodologies for the combination of dietary questionnaire and biomarker data for disease risk assessment. It is clear that dietary biomarkers require much further research in order to be better applied and interpreted. Future priorities should be to integrate high quality dietary intake information, measurements of dietary biomarkers, metabolic profiles of specific dietary patterns, genetics and novel statistical methodology in order to provide important new insights into gene-diet-lifestyle-disease risk associations.

LDL-cholesterol concentrations: a genome-wide association study.

BACKGROUND: LDL cholesterol has a causal role in the development of cardiovascular disease. Improved understanding of the biological mechanisms that underlie the metabolism and regulation of LDL cholesterol might help to identify novel therapeutic targets. We therefore did a genome-wide association study of LDL-cholesterol concentrations. METHODS: We used genome-wide association data from up to 11,685 participants with measures of circulating LDL-cholesterol concentrations across five studies, including data for 293 461 autosomal single nucleotide polymorphisms (SNPs) with a minor allele frequency of 5% or more that passed our quality control criteria. We also used data from a second genome-wide array in up to 4337 participants from three of these five studies, with data for 290,140 SNPs. We did replication studies in two independent populations consisting of up to 4979 participants. Statistical approaches, including meta-analysis and linkage disequilibrium plots, were used to refine association signals; we analysed pooled data from all seven populations to determine the effect of each SNP on variations in circulating LDL-cholesterol concentrations. FINDINGS: In our initial scan, we found two SNPs (rs599839 [p=1.7x10(-15)] and rs4970834 [p=3.0x10(-11)]) that showed genome-wide statistical association with LDL cholesterol at chromosomal locus 1p13.3. The second genome screen found a third statistically associated SNP at the same locus (rs646776 [p=4.3x10(-9)]). Meta-analysis of data from all studies showed an association of SNPs rs599839 (combined p=1.2x10(-33)) and rs646776 (p=4.8x10(-20)) with LDL-cholesterol concentrations. SNPs rs599839 and rs646776 both explained around 1% of the variation in circulating LDL-cholesterol concentrations and were associated with about 15% of an SD change in LDL cholesterol per allele, assuming an SD of 1 mmol/L. INTERPRETATION: We found evidence for a novel locus for LDL cholesterol on chromosome 1p13.3. These results potentially provide insight into the biological mechanisms that underlie the regulation of LDL cholesterol and might help in the discovery of novel therapeutic targets for cardiovascular disease.

Phytoestrogen content of cereals and cereal-based foods consumed in the UK.

Dietary phytoestrogens may be involved in the occurrence of chronic diseases. Reliable information on the phytoestrogen content in foods is required to assess dietary exposure and disease risk in epidemiological studies. However, there is little information on isoflavone, lignan, and coumestrol content of cereals and cereal-based foods, leading to an underestimation of intake. This is the first study of phytoestrogens (isoflavones: biochanin A, daidzein, formononetin, genistein, glycitein; lignans: matairesinol, secoisplariciresinol; coumestrol) in a comprehensive selection of 101 cereals and cereal-based foods-including breads, breakfast cereals, biscuits, pasta and rice-consumed in the UK using a sensitive LCMS technique with 13C-labelled internal standards. Phytoestrogens were detected in all foods analyzed; bread contained the highest amount of phytoestrogens-many as isoflavones-with an average content of 375 +/- 67 microg/100 g wet weight (excluding soya-linseed bread with 12,000 microg/100 g). Most other foods contained less than 100 microg/100 g, many as lignans. Our study shows that all foods analyzed contained phytoestrogens, with the highest amount found in breads, making them one of the main sources of dietary phytoestrogens in the UK. These results will allow a more accurate estimation of exposure to dietary phytoestrogens.

Energy intake at breakfast and weight change: prospective study of 6,764 middle-aged men and women.

To investigate the association between percentage of total daily energy intake consumed at breakfast and weight change in middle-aged men and women, the authors analyzed data from a prospective population-based cohort study from Norfolk, United Kingdom. Participants were 6,764 men and women aged 40-75 years at baseline (1993-1997). Participants completed a 7-day food diary at baseline, and objective measurements of height and weight were carried out at baseline and follow-up (1998-2000). Mean baseline body mass index (weight (kg)/height (m)(2)) was lowest among persons in the highest quintile of percentage of daily energy consumed at breakfast (mean values were 26.0 in the highest quintile and 26.3 in the lowest quintile), despite higher daily total energy intake in this group. Although all participants gained weight, increased percentage of daily energy consumed at breakfast was associated with relatively lower weight gain (adjusted beta coefficient = -0.021, 95% confidence interval: -0.035, -0.007; p = 0.004). The association between percentage of daily energy intake consumed at breakfast and weight gain was independent of age, sex, smoking, total energy intake, macronutrient intake, social class, and physical activity. Redistribution of daily energy intake, so that more energy is consumed at breakfast and less energy is consumed later in the day, may help to reduce weight gain in middle-aged adults.

Use of recovery biomarkers to calibrate nutrient consumption self-reports in the Women's Health Initiative.

Underreporting of energy consumption by self-report is well-recognized, but previous studies using recovery biomarkers have not been sufficiently large to establish whether participant characteristics predict misreporting. In 2004-2005, 544 participants in the Women's Health Initiative Dietary Modification Trial completed a doubly labeled water protocol (energy biomarker), 24-hour urine collection (protein biomarker), and self-reports of diet (assessed by food frequency questionnaire (FFQ)), exercise, and lifestyle habits; 111 women repeated all procedures after 6 months. Using linear regression, the authors estimated associations of participant characteristics with misreporting, defined as the extent to which the log ratio (self-reported FFQ/nutritional biomarker) was less than zero. Intervention women in the trial underreported energy intake by 32% (vs. 27% in the comparison arm) and protein intake by 15% (vs. 10%). Younger women had more underreporting of energy (p = 0.02) and protein (p = 0.001), while increasing body mass index predicted increased underreporting of energy and overreporting of percentage of energy derived from protein (p = 0.001 and p = 0.004, respectively). Blacks and Hispanics underreported more than did Caucasians. Correlations of initial measures with repeat measures (n = 111) were 0.72, 0.70, 0.46, and 0.64 for biomarker energy, FFQ energy, biomarker protein, and FFQ protein, respectively. Recovery biomarker data were used in regression equations to calibrate self-reports; the potential application of these equations to disease risk modeling is presented. The authors confirm the existence of systematic bias in dietary self-reports and provide methods of correcting for measurement error.

Depression and ischemic heart disease mortality: evidence from the EPIC-Norfolk United Kingdom prospective cohort study.

OBJECTIVE: The authors investigated the association between major depressive disorder, including its clinical course, and mortality from ischemic heart disease. METHOD: This was a prospective cohort study of 8,261 men and 11,388 women 41-80 years of age who were free of clinical manifestations of heart disease and participated in the Norfolk, U.K., cohort of the European Prospective Investigation Into Cancer. The authors conducted a cross-sectional assessment of major depressive disorder during the period 1996-2000 and ascertained subsequent deaths from ischemic heart disease through linkage with data from the U.K. Office for National Statistics. RESULTS: As of July 31, 2006, 274 deaths from ischemic heart disease were recorded over a total follow-up of 162,974 person-years (the median follow-up period was 8.5 years). Participants who had major depression during the year preceding baseline assessment were 2.7 times more likely to die from ischemic heart disease over the follow-up period than those who did not, independently of age, sex, smoking, systolic blood pressure, cholesterol, physical activity, body mass index, diabetes, social class, heavy alcohol use, and antidepressant medication use. This association remained after exclusion of the first 6 years of follow-up data. Consideration of measures of major depression history (including recency of onset, recurrence, chronicity, and age at first onset) revealed recency of onset to be associated most strongly with ischemic heart disease mortality. CONCLUSIONS: Major depression was associated with an increased risk of ischemic heart disease mortality. The association was independent of established risk factors for ischemic heart disease and remained undiminished several years after the original assessment.

Plasma vitamin C concentrations predict risk of incident stroke over 10 y in 20 649 participants of the European Prospective Investigation into Cancer Norfolk prospective population study.

BACKGROUND: The relation between plasma vitamin C and risk of stroke remains unclear. Although clinical trials showed no significant benefit of vitamin C supplementation in reducing stroke risk, they were not able to examine the relation between plasma vitamin C concentrations and stroke risk in a general population. OBJECTIVE: The objective was to examine the relation between baseline plasma vitamin C concentrations and risk of incident stroke in a British population. DESIGN: A population-based prospective study was conducted in 20,649 men and women aged 40-79 y without prevalent stroke at baseline and participating in the European Prospective Investigation into Cancer-Norfolk prospective population study. The participants completed a health questionnaire and attended a clinic during 1993-1997 and were followed up for incident strokes through March 2005. RESULTS: Over 196,713 total person-years (average follow-up: 9.5 y), 448 incident strokes occurred. In a Cox proportional hazards model, persons in the top quartiles of baseline plasma vitamin C concentrations had a 42% lower risk (relative risk: 0.58; 95% CI: 0.43, 0.78) than did those in the bottom quartile, independently of age, sex, smoking, body mass index, systolic blood pressure, cholesterol, physical activity, prevalent diabetes and myocardial infarction, social class, alcohol consumption, and any supplement use. Similar results were obtained after exclusion of persons with illnesses, users of ascorbic acid-containing supplements, and persons with a history of early strokes during the initial 2 y of follow-up. CONCLUSIONS: Plasma vitamin C concentrations may serve as a biological marker of lifestyle or other factors associated with reduced stroke risk and may be useful in identifying those at high risk of stroke.

Contribution of TNFSF15 gene variants to Crohn's disease susceptibility confirmed in UK population.

BACKGROUND: Identification of Crohn's disease (CD)-associated genetic variants is key to understanding pathogenic pathways underlying disease susceptibility. Recent reports of an association between TNFSF15 variants and CD have been modestly replicated in European populations, suggesting heterogeneity at this locus with stronger CD association in Japanese than European populations. METHODS: We investigated the association between variants in TNFSF15 and CD in 756 CD patients and 636 controls. Disease subphenotype associations were also investigated. RESULTS: TNFSF15 single nucleotide polymorphism (SNP) variants were associated with CD in our panel with peak odds ratio (OR) 1.2 (95% confidence interval [CI] 1.01-1.41) P = 0.033. The presence of a risk haplotype was replicated for the first time in a European population (frequency 67% in cases and 61% in controls) OR = 1.44 (95% CI 1.23-1.68) P = 0.00012. This result mirrors the UK panel in the index study (Yamazaki et al [2005] Hum Mol Genet 14:3499-3506) but is less significant than that reported in Japanese populations. There was no evidence of association with any individual CD subphenotype. CONCLUSIONS: Variants in TNFSF15 contribute to overall CD susceptibility in European populations, although to a lesser extent than that seen in the Japanese. Further studies to define the precise disease-causing variants as well as targeted functional studies are now required in human CD as TNFSF15 is a potential target for biological therapies.

Risk factors for first-ever stroke in the EPIC-Norfolk prospective population-based study.

BACKGROUND: Many studies examining stroke risk factors have focused on men and younger age groups. We examined stroke risk factors over a wide age range including elderly and women in a British population. METHODS: We examined the prospective relationship between known risk factors for stroke and stroke incidence in 22 516 men and women aged 40-79 years without stroke at baseline in the years 1993-1997 participating in the European Prospective Investigation into Cancer-Norfolk. RESULTS: During a total of 214 542 person-years of follow-up, 507 incident strokes occurred (fatal=162). Stroke risk increased with increasing age [relative risk (RR) 1.65, 95% confidence interval: 1.54, 1.75 per increase in 5 years]. Our results confirm the importance of modifiable risk factors for stroke in men and women, in particular, blood pressure and smoking. Higher systolic blood pressure of 10 mmHg was associated with RR of 1.19 (1.13, 1.24) and current smokers had RR of 1.70 (1.29, 2.23) compared with never smokers independent of age, sex, body mass index, cholesterol, triglycerides and diabetes. Having a systolic blood pressure greater than 140 mmHg compared with less than 140 mmHg was equivalent to being 6 years older and current smoking compared with nonsmoking equivalent to being 5 years older and diabetes 5 years older in terms of stroke risk. CONCLUSION: Classical modifiable stroke risk factors, blood pressure and smoking, may have a substantial impact on the age-related increase in stroke risk in men and women.

Urine pH is an indicator of dietary acid-base load, fruit and vegetables and meat intakes: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk population study.

Evidence exists that a more acidic diet is detrimental to bone health. Although more precise methods exist for measurement of acid-base balance, urine pH reflects acid-base balance and is readily measurable but has not been related to habitual dietary intake in general populations. The present study investigated the relationship between urine pH and dietary acid-base load (potential renal acid load; PRAL) and its contributory food groups (fruit and vegetables, meats, cereal and dairy foods). There were 22,034 men and women aged 39-78 years living in Norfolk (UK) with casual urine samples and dietary intakes from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk FFQ. A sub-study (n 363) compared pH in casual samples and 24 h urine and intakes from a 7 d diary and the FFQ. A more alkaline diet (low PRAL), high fruit and vegetable intake and lower consumption of meat was significantly associated with a more alkaline urine pH before and after adjustment for age, BMI, physical activity and smoking habit and also after excluding for urinary protein, glucose, ketones, diagnosed high blood pressure and diuretic medication. In the sub-study the strongest relationship was found between the 24 h urine and the 7 d diary. In conclusion, a more alkaline diet, higher fruit and vegetable and lower meat intake were related to more alkaline urine with a magnitude similar to intervention studies. As urine pH relates to dietary acid-base load its use to monitor change in consumption of fruit and vegetables, in individuals, warrants further investigation.

Mammographic density using two computer-based methods in an isoflavone trial.

OBJECTIVES: Mammographic density is a useful biomarker of breast cancer risk. Computer-based methods can provide continuous data suitable for analysis. This study aimed to compare a semi-automated computer-assisted method (Cumulus) and a fully automated volumetric computer method (standard mammogram form (SMF)) for assessing mammographic density using data from a previously conducted randomised placebo-controlled trial of an isoflavone supplement. METHODS: Mammograms were obtained from participants in the intervention study. A total of 177 women completed the study. Baseline and follow-up mammograms were digitised and density was estimated using Cumulus (read by two readers) and SMF. Left-right correlation, changes in density over time, and difference between intervention and control groups were evaluated. Changes of density over time, and changes between intervention group and control group were examined using paired t-test and Student's t-test, respectively. RESULTS: Inter-reader correlation coefficient by Cumulus was 0.90 for dense area, and 0.86 for percentage density. Left-right correlation of percent density was lower in SMF than in Cumulus. Among all women, percentage density by Cumulus decreased significantly over time, but no change was seen for SMF percentage density. The intervention group showed marginally significant greater reduction of percent density by Cumulus compared to controls (p=0.04), but the difference became weak after adjustment for baseline percent density (p=0.06). No other measurement demonstrated significant difference between intervention and control groups. CONCLUSIONS: This comparison suggests that slightly different conclusions could be drawn from different methods used to assess breast density. The development of a more robust fully automated method is awaited.

Implications of gene-environment interaction in studies of gene variants in breast cancer: an example of dietary isoflavones and the D356N polymorphism in the sex hormone-binding globulin gene.

Studies to identify common genetic variants contributing to breast cancer risk often yield inconsistent results. Breast cancer is a complex disease involving both genetic and environmental determinants. Dietary isoflavones are thought to reduce breast cancer risk by stimulating circulating sex hormone-binding globulin (SHBG) levels. The SHBG gene contains a D356N polymorphism and the N variant is associated with reduced SHBG clearance compared with the D variant. In this study, we show a significant gene-environment interaction between SHBG D356N polymorphism and dietary isoflavone exposure on circulating SHBG levels in 1,988 postmenopausal women. SHBG levels were positively associated with isoflavones in women carrying the N variant (etap2 = 1.9%; P = 0.006) but not in women carrying only the D variant (etap2 = 0.0%; P = 0.999; P(interaction) = 0.019). This finding shows that the subtle effects of some genetic variants may be magnified and only become detectable in the presence of certain exposures. This gene-environment interaction might explain heterogeneity in studies associating SHBG gene variants and soy consumption with breast cancer risk in Far East population exposed to high isoflavone levels compared with populations with lower levels.

Red meat enhances the colonic formation of the DNA adduct O6-carboxymethyl guanine: implications for colorectal cancer risk.

Red meat is associated with increased risk of colorectal cancer and increases the endogenous formation of N-nitrosocompounds (NOC). To investigate the genotoxic effects of NOC arising from red meat consumption, human volunteers were fed high (420 g) red meat, vegetarian, and high red meat, high-fiber diets for 15 days in a randomized crossover design while living in a volunteer suite, where food was carefully controlled and all specimens were collected. In 21 volunteers, there was a consistent and significant (P < 0.0001) increase in endogenous formation of NOC with the red meat diet compared with the vegetarian diet as measured by apparent total NOC (ATNC) in feces. In colonic exfoliated cells, the percentage staining positive for the NOC-specific DNA adduct, O(6)-carboxymethyl guanine (O(6)CMG) was significantly (P < 0.001) higher on the high red meat diet. In 13 volunteers, levels were intermediate on the high-fiber, high red meat diet. Fecal ATNC were positively correlated with the percentage of cells staining positive for O(6)CMG (r(2) = 0.56, P = 0.011). The presence of O(6)CMG was also shown in intact small intestine from rats treated with the N-nitrosopeptide N-acetyl-N'-prolyl-N'-nitrosoglycine and in HT-29 cells treated with diazoacetate. This study has shown that fecal NOC arising from red meat include direct acting diazopeptides or N-nitrosopeptides able to form alkylating DNA adducts in the colon. As these O(6)CMG adducts are not repaired, and if other related adducts are formed and not repaired, this may explain the association of red meat with colorectal cancer.