Kristin A. Guertin

Metabolomics in nutritional epidemiology: identifying metabolites associated with diet and quantifying their potential to uncover diet-disease relations in populations.

BACKGROUND Metabolomics is an emerging field with the potential to advance nutritional epidemiology; however, it has not yet been applied to large cohort studies. OBJECTIVES Our first aim was to identify metabolites that are biomarkers of usual dietary intake. Second, among serum metabolites correlated with diet, we evaluated metabolite reproducibility and required sample sizes to determine the potential for metabolomics in epidemiologic studies. DESIGN Baseline serum from 502 participants in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was analyzed by using ultra-high-performance liquid-phase chromatography with tandem mass spectrometry and gas chromatography-mass spectrometry. Usual intakes of 36 dietary groups were estimated by using a food-frequency questionnaire. Dietary biomarkers were identified by using partial Pearsons correlations with Bonferroni correction for multiple comparisons. Intraclass correlation coefficients (ICCs) between samples collected 1 y apart in a subset of 30 individuals were calculated to evaluate intraindividual metabolite variability. RESULTS We detected 412 known metabolites. Citrus, green vegetables, red meat, shellfish, fish, peanuts, rice, butter, coffee, beer, liquor, total alcohol, and multivitamins were each correlated with at least one metabolite (P < 1.093 × 10(-6); r = -0.312 to 0.398); in total, 39 dietary biomarkers were identified. Some correlations (citrus intake with stachydrine) replicated previous studies; others, such as peanuts and tryptophan betaine, were novel findings. Other strong associations included coffee (with trigonelline-N-methylnicotinate and quinate) and alcohol (with ethyl glucuronide). Intraindividual variability in metabolite levels (1-y ICCs) ranged from 0.27 to 0.89. Large, but attainable, sample sizes are required to detect associations between metabolites and disease in epidemiologic studies, further emphasizing the usefulness of metabolomics in nutritional epidemiology. CONCLUSIONS We identified dietary biomarkers by using metabolomics in an epidemiologic data set. Given the strength of the associations observed, we expect that some of these metabolites will be validated in future studies and later used as biomarkers in large cohorts to study diet-disease associations. The PLCO trial was registered at clinicaltrials.gov as NCT00002540.

Association of Coffee Consumption With Overall and Cause-Specific Mortality in a Large US Prospective Cohort Study

Concerns about high caffeine intake and coffee as a vehicle for added fat and sugar have raised questions about the net impact of coffee on health. Although inverse associations have been observed for overall mortality, data for cause-specific mortality are sparse. Additionally, few studies have considered exclusively decaffeinated coffee intake or use of coffee additives. Coffee intake was assessed at baseline by self-report in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Hazard ratios were estimated using Cox proportional hazards models. Among 90,317 US adults without cancer at study baseline (1998-2001) or history of cardiovascular disease at study enrollment (1993-2001), 8,718 deaths occurred during 805,644 person-years of follow-up from 1998 through 2009. Following adjustment for smoking and other potential confounders, coffee drinkers, as compared with nondrinkers, had lower hazard ratios for overall mortality (<1 cup/day: hazard ratio (HR) = 0.99 (95% confidence interval (CI): 0.92, 1.07); 1 cup/day: HR = 0.94 (95% CI: 0.87, 1.02); 2-3 cups/day: HR = 0.82 (95% CI: 0.77, 0.88); 4-5 cups/day: HR = 0.79 (95% CI: 0.72, 0.86); ≥6 cups/day: HR = 0.84 (95% CI: 0.75, 0.95)). Similar findings were observed for decaffeinated coffee and coffee additives. Inverse associations were observed for deaths from heart disease, chronic respiratory diseases, diabetes, pneumonia and influenza, and intentional self-harm, but not cancer. Coffee may reduce mortality risk by favorably affecting inflammation, lung function, insulin sensitivity, and depression.

Comparing metabolite profiles of habitual diet in serum and urine

BACKGROUND Diet plays an important role in chronic disease etiology, but some diet-disease associations remain inconclusive because of methodologic limitations in dietary assessment. Metabolomics is a novel method for identifying objective dietary biomarkers, although it is unclear what dietary information is captured from metabolites found in serum compared with urine. OBJECTIVE We compared metabolite profiles of habitual diet measured from serum with those measured from urine. DESIGN We first estimated correlations between consumption of 56 foods, beverages, and supplements assessed by a food-frequency questionnaire, with 676 serum and 848 urine metabolites identified by untargeted liquid chromatography mass spectrometry, ultra-high performance liquid chromatography tandem mass spectrometry, and gas chromatography mass spectrometry in a colon adenoma case-control study (n = 125 cases and 128 controls) while adjusting for age, sex, smoking, fasting, case-control status, body mass index, physical activity, education, and caloric intake. We controlled for multiple comparisons with the use of a false discovery rate of <0.1. Next, we created serum and urine multiple-metabolite models to predict food intake with the use of 10-fold crossvalidation least absolute shrinkage and selection operator regression for 80% of the data; predicted values were created in the remaining 20%. Finally, we compared predicted values with estimates obtained from self-reported intake for metabolites measured in serum and urine. RESULTS We identified metabolites associated with 46 of 56 dietary items; 417 urine and 105 serum metabolites were correlated with ≥1 food, beverage, or supplement. More metabolites in urine (n = 154) than in serum (n = 39) were associated uniquely with one food. We found previously unreported metabolite associations with leafy green vegetables, sugar-sweetened beverages, citrus, added sugar, red meat, shellfish, desserts, and wine. Prediction of dietary intake from multiple-metabolite profiles was similar between biofluids. CONCLUSIONS Candidate metabolite biomarkers of habitual diet are identifiable in both serum and urine. Urine samples offer a valid alternative or complement to serum for metabolite biomarkers of diet in large-scale clinical or epidemiologic studies.

Coffee consumption and incidence of lung cancer in the NIH-AARP Diet and Health Study

BACKGROUND Coffee drinkers had a higher risk of lung cancer in some previous studies, but as heavy coffee drinkers tend to also be cigarette smokers, such findings could be confounded. Therefore, we examined this association in the nearly half a million participants of the US NIH-AARP Diet and Health Study. METHODS Typical coffee intake and smoking history were queried at baseline. During 4 155 256 person-years of follow-up, more than 9000 incident lung cancer cases occurred. We used Cox proportional hazards regression to estimate hazard ratios (HRs)and 95% confidence intervals for coffee intake and subsequent incidence of lung cancer. We also comprehensively adjusted for tobacco smoking and examined associations by detailed strata of tobacco use. RESULTS Coffee drinkers were far more likely to smoke than non-drinkers. Although coffee drinking was associated with lung cancer in age- and sex- adjusted models (HR for ≥ 6 cups/day compared with none: 4.56, 4.08-5.10), this association was substantially attenuated after adjusting for smoking (HR: 1.27, 1.14-1.42). Similar findings were observed for each different histological type of lung cancer, and for participants drinking predominantly caffeinated or decaffeinated coffee. Little evidence for an association was observed in our stratified analyses, either within never smokers or in most categories of tobacco use. CONCLUSIONS Coffee drinking was positively associated with lung cancer in our study, although the association was substantially attenuated after adjustment for tobacco smoking. As our adjustment for lifetime tobacco use was imperfect, it is likely that the remaining association is due to residual confounding by smoking, although other explanations are possible.

Dietary Inflammatory Index and Risk of Epithelial Ovarian Cancer in African American Women

Chronic inflammation has been implicated in the development of epithelial ovarian cancer (EOC); yet the contribution of inflammatory foods and nutrients to EOC risk has been understudied. We investigated the association between the dietary inflammatory index (DII), a novel literature‐derived tool to assess the inflammatory potential of ones diet, and EOC risk in African American (AA) women in the African American Cancer Epidemiology Study, the largest population‐based case–control study of EOC in AA women to date. The energy‐adjusted DII (E‐DII) was computed per 1,000 kilocalories from dietary intake data collected through a food frequency questionnaire, which measured usual dietary intake in the year prior to diagnosis for cases or interview for controls. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using multivariable logistic regression for the association between the E‐DII and EOC risk. 493 cases and 662 controls were included in the analyses. We observed a 10% increase in EOC risk per a one‐unit change in the E‐DII (OR = 1.10, 95% CI = 1.03–1.17). Similarly, women consuming the most pro‐inflammatory diet had a statistically significant increased EOC risk in comparison to the most anti‐inflammatory diet (ORQuartile4/Quartile1 = 1.72; 95% CI = 1.18–2.51). We also observed effect modification by age (p < 0.05), where a strong, significant association between the E‐DII and EOC risk was observed among women older than 60 years, but no association was observed in women aged 60 years or younger. Our findings suggest that a more pro‐inflammatory diet was associated with an increased EOC risk, especially among women older than 60 years.

Serum trimethylamine n-oxide, carnitine, choline, and betaine in relation to colorectal cancer risk in the alpha tocopherol, beta carotene cancer prevention study

Background: Trimethylamine N-oxide (TMAO), a choline-derived metabolite produced by gut microbiota, and its biomarker precursors have not been adequately evaluated in relation to colorectal cancer risk. Methods: We investigated the relationship between serum concentrations of TMAO and its biomarker precursors (choline, carnitine, and betaine) and incident colorectal cancer risk in a nested case–control study of male smokers in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. We measured biomarker concentrations in baseline fasting serum samples from 644 incident colorectal cancer cases and 644 controls using LC/MS-MS. Logistic regression models estimated the ORs and 95% confidence interval (CI) for colorectal cancer by quartile (Q) of serum TMAO, choline, carnitine, and betaine concentrations. Results: Men with higher serum choline at ATBC baseline had approximately 3-fold greater risk of developing colorectal cancer over the ensuing (median ± IQR) 14 ± 10 years (in fully adjusted models, Q4 vs. Q1, OR, 3.22; 95% CI, 2.24–4.61; Ptrend < 0.0001). The prognostic value of serum choline for prediction of incident colorectal cancer was similarly robust for proximal, distal, and rectal colon cancers (all P < 0.0001). The association between serum TMAO, carnitine, or betaine and colorectal cancer risk was not statistically significant (P = 0.25, 0.71, and 0.61, respectively). Conclusions: Higher serum choline concentration (but not TMAO, carnitine, or betaine) was associated with increased risk of colorectal cancer. Impact: Serum choline levels showed strong prognostic value for prediction of incident colorectal cancer risk across all anatomical subsites, suggesting a role of altered choline metabolism in colorectal cancer pathogenesis. Cancer Epidemiol Biomarkers Prev; 26(6); 945–52. ©2017 AACR.

Time to First Morning Cigarette and Risk of Chronic Obstructive Pulmonary Disease: Smokers in the PLCO Cancer Screening Trial

Background Time to first cigarette (TTFC) after waking is an indicator of nicotine dependence. The association between TTFC and chronic obstructive pulmonary disease (COPD), the third leading cause of death in the United States, has not yet been reported. Methods We investigated the cross-sectional association between TTFC and prevalent COPD among 6,108 current smokers in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. COPD was defined as a self-reported diagnosis of emphysema, chronic bronchitis, or both. Current smokers in PLCO reported TTFC, the amount of time they typically waited before smoking their first cigarette of the day after waking, in four categories: ≤5, 6-30, 31-60, or >60 minutes. We used logistic regression models to investigate the association between TTFC and prevalent COPD with adjustments for age, gender, race, education, and smoking (cigarettes/day, years smoked during lifetime, pack-years, age at smoking initiation), and prior lung cancer diagnosis. Results COPD was reported by 19% of these 6,108 smokers. Individuals with the shortest TTFC had the greatest risk of COPD; compared to those with the longest TTFC (>60 minutes) the adjusted odds ratios (OR) and 95% confidence intervals (CI) for COPD were 1.48 (95% CI, 1.15-1.91), 1.64 (95% CI, 1.29-2.08), 2.18 (95% CI, 1.65-2.87) for those with TTFC 31-60 minutes, 6-30 minutes, and ≤5 minutes, respectively (P-trend <0.0001). The association between TTFC and emphysema was similar to that for bronchitis, albeit the ORs were slightly stronger for chronic bronchitis; comparing TTFC ≤5 minutes to >60 minutes, the adjusted OR (95% CI) was 2.29 (1.69-3.12) for emphysema and 2.99 (1.95-4.59) for chronic bronchitis. Conclusions Current smokers with shorter TTFC have increased risk of COPD compared to those with longer TTFC, even after comprehensive adjustment for established smoking covariates. Future epidemiologic studies, including prospective designs, should incorporate TTFC to better assess disease risk and evaluate the potential utility of TTFC as a COPD screening tool for smokers in the clinical setting.

Alcohol Consumption-Related Metabolites in Relation to Colorectal Cancer and Adenoma: Two Case-Control Studies Using Serum Biomarkers.

Alcohol is a known carcinogen that may be associated with colorectal cancer. However, most epidemiologic studies assess alcoholic beverage consumption using self-reported data, leading to potential exposure misclassification. Biomarkers of alcohol consumption may provide an alternative, complementary approach that reduces misclassification and incorporates individual differences in alcohol metabolism. Therefore, we evaluated the relationship between previously identified alcohol consumption-related metabolites and colorectal cancer and adenoma using serum metabolomics data from two studies. Data on colorectal cancer were obtained from a nested case-control study of 502 US adults (252 cases, 250 controls) within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Data on colorectal adenoma were obtained from a case-control study of 197 US adults (120 cases, 77 controls) from the Navy Colon Adenoma Study. Unconditional multivariable logistic regression models were fit to calculate odds ratios (OR) and 95% confidence intervals (CI) for eight alcohol consumption-related metabolites identified in a previous analysis: ethyl glucuronide; 4-androstene-3beta,17beta-diol disulfate 1; 5-alpha-androstan-3beta,17beta-diol disulfate; 16-hydroxypalmitate; bilirubin (E,Z or Z,E); cyclo (-leu-pro); dihomo-linoleate (20:2n6); and palmitoleate (16:1n7). We found no clear association between these alcohol consumption-related metabolites and either endpoint. However, we did observe an inverse association between cyclo (-leu-pro) and colorectal adenoma that was only observed in the highest metabolite quantile (OR 4th vs. 1st Quantile = 0.30, 95% CI: 0.12–0.78; P-trend = 0.047), but no association for colorectal cancer. In conclusion, there were no adverse associations between alcohol consumption-related metabolites and colorectal cancer or adenoma.

Supplemental Selenium May Decrease Ovarian Cancer Risk in African-American Women

Background: To our knowledge, no previous study has evaluated the associations of antioxidant intake with the risk of ovarian cancer in African-American women, who are known to have high mortality from the disease.Objective: We sought to evaluate these associations among 406 ovarian cancer cases and 632 age- and site-matched controls of African-American descent recruited from AACES (African American Cancer Epidemiology Study), a population-based, case-control study in 11 geographical areas within the United States.Methods: Multivariable logistic regression models were used to estimate ORs and 95% CIs adjusted for a wide range of potentially confounding factors, including age, region, education, parity, oral contraceptive use, menopause, tubal ligation, family history, body mass index (BMI), smoking status, total energy, and physical activity.Results: Women with the highest intakes of supplemental selenium (>20 μg/d) had an ∼30% lower risk of ovarian cancer than those with no supplemental intake (OR: 0.67; 95% CI: 0.46, 0.97; P-trend = 0.035). This inverse association was stronger in current smokers (OR: 0.13; 95% CI: 0.04, 0.46; P-trend = 0.001). There was no association with dietary selenium. The associations with carotenoid intakes were weak and nonsignificant (P = 0.07-0.60). We observed no association with dietary or supplemental intake of vitamin C or vitamin E. There were no appreciable differences in results between serous and nonserous tumors.Conclusions: These findings provide the first insights, to our knowledge, into the potential association between antioxidants and ovarian cancer in African-American women, indicating potential inverse associations with supplemental selenium.

Longitudinal changes in anthropometry and body composition in university freshmen

ABSTRACT Objective: We investigated predictors of weight gain in college freshmen. Participants: A longitudinal cohort study followed a representative sample of freshmen (N = 264) from 8/2011 to 6/2012. Methods: Repeated measurements of anthropometry, dual-energy X-ray absorptiometry (DXA), physical activity, and diet were collected. We investigated predictors of 9-month weight gain using regression models. Results: 172 participants completed follow-up: 75% gained >0.5 kg. Mean weight change was +2.3 kg (SD 3.2) and +2.0 kg (SD 3.2) and mean adiposity change was +1.3% (SD 1.6) and +0.7% (SD 2.2) in men and women, respectively. In participants gaining >0.5 kg, weight increased 5.6% and body fat increased 1.6%. Anthropometric change in men occurred in the first semester, while women increased in both semesters. Leaner DXA-defined body composition at baseline was consistently associated with greater weight gain (p-values 0.029–0.049). Conclusions: Freshman weight gain is common and reflects increased adiposity. Leaner body composition at the beginning of college predicted greater weight gain in men and women during the first year of college.