Trimethylamine N-oxide (TMAO), a compound derived from diet and metabolism by the gut microbiome, has been associated with several chronic diseases, although the mechanisms of action are not well ...understood and few human studies have investigated microbes involved in its production.
Our study aims were 1) to investigate associations of TMAO and its precursors (choline, carnitine, and betaine) with inflammatory and cardiometabolic risk biomarkers; and 2) to identify fecal microbiome profiles associated with TMAO.
We conducted a cross-sectional analysis using data collected from 1653 participants (826 men and 827 women, aged 60–77 y) in the Multiethnic Cohort Study. Plasma concentrations of TMAO and its precursors were measured by LC-tandem MS. We also analyzed fasting blood for markers of inflammation, glucose and insulin, cholesterol, and triglycerides (TGs), and further measured blood pressure. Fecal microbiome composition was evaluated by sequencing the 16S ribosomal RNA gene V1–V3 region. Associations of TMAO and its precursors with disease risk biomarkers were assessed by multivariable linear regression, whereas associations between TMAO and the fecal microbiome were assessed by permutational multivariate ANOVA and hurdle regression models using the negative binomial distribution.
Median (IQR) concentration of plasma TMAO was 3.05 μmol/L (2.10–4.60 μmol/L). Higher concentrations of TMAO and carnitine, and lower concentrations of betaine, were associated with greater insulin resistance (all P < 0.02). Choline was associated with higher systolic blood pressure, TGs, lipopolysaccharide-binding protein, and lower HDL cholesterol (P ranging from <0.001 to 0.03), reflecting an adverse cardiometabolic risk profile. TMAO was associated with abundance of 13 genera (false discovery rate < 0.05), including Prevotella, Mitsuokella, Fusobacterium, Desulfovibrio, and bacteria belonging to the families Ruminococcaceae and Lachnospiraceae, as well as the methanogen Methanobrevibacter smithii.
Plasma TMAO concentrations were associated with a number of trimethylamine-producing bacterial taxa, and, along with its precursors, may contribute to inflammatory and cardiometabolic risk pathways.
Background and Aims
Epidemiological data on dietary risk factors for nonalcoholic fatty liver disease (NAFLD) from population‐based studies, particularly in an ethnically diverse population, are ...scarce. We examined dietary factors in relation to NAFLD risk in African Americans, Japanese Americans, Latinos, native Hawaiians, and whites in the Multiethnic Cohort (MEC).
Approach and Results
A nested case–control analysis was conducted within the MEC, a large prospective study with >215,000 older adult participants in Hawaii and California. NAFLD was identified using Medicare claims data, and controls were selected among participants without liver disease and individually matched to cases by birth year, sex, ethnicity, and length of Medicare enrollment. Diet was assessed at baseline through a validated quantitative food frequency questionnaire. Diet–NAFLD associations were quantified by odds ratios and 95% confidence intervals using multivariable conditional logistic regression. The study consisted of 2,974 NAFLD cases (518 with cirrhosis, 2,456 without cirrhosis) and 29,474 matched controls. Red meat (P trend = 0.010), processed red meat (P trend = 0.004), poultry (P trend = 0.005), and cholesterol (P trend = 0.005) intakes were positively associated with NAFLD, while dietary fiber intake (P trend = 0.003) was inversely associated with risk. Stronger associations were observed between red meat and cholesterol and NAFLD with cirrhosis than without cirrhosis (P heterogeneity ≤0.014).
Conclusions
Dietary factors are independently associated with NAFLD and NAFLD‐related cirrhosis in a multiethnic population. Decreasing the consumption of cholesterol, red and processed meat, and poultry and increasing consumption of fiber may reduce the risk for NAFLD and related advanced liver disease.
At the time of cancer diagnosis, body mass index (BMI) is inversely correlated with lung cancer risk, which may reflect reverse causality and confounding due to smoking behavior. We used two‐sample ...univariable and multivariable Mendelian randomization (MR) to estimate causal relationships of BMI and smoking behaviors on lung cancer and histological subtypes based on an aggregated genome‐wide association studies (GWASs) analysis of lung cancer in 29 266 cases and 56 450 controls. We observed a positive causal effect for high BMI on occurrence of small‐cell lung cancer (odds ratio (OR) = 1.60, 95% confidence interval (CI) = 1.24‐2.06, P = 2.70 × 10−4). After adjustment of smoking behaviors using multivariable Mendelian randomization (MVMR), a direct causal effect on small cell lung cancer (ORMVMR = 1.28, 95% CI = 1.06‐1.55, PMVMR = .011), and an inverse effect on lung adenocarcinoma (ORMVMR = 0.86, 95% CI = 0.77‐0.96, PMVMR = .008) were observed. A weak increased risk of lung squamous cell carcinoma was observed for higher BMI in univariable Mendelian randomization (UVMR) analysis (ORUVMR = 1.19, 95% CI = 1.01‐1.40, PUVMR = .036), but this effect disappeared after adjustment of smoking (ORMVMR = 1.02, 95% CI = 0.90‐1.16, PMVMR = .746). These results highlight the histology‐specific impact of BMI on lung carcinogenesis and imply mediator role of smoking behaviors in the association between BMI and lung cancer.
What's new?
Lung cancer risk appears to be inversely correlated with BMI, which could be due to a variety of factors. Here, the authors used Mendelian randomization (MR) to look for a causal effect of BMI on lung cancer. MR uses genetic variants as instrumental variables, and avoids the effects of confounding factors. However, linkage disequilibrium with causal variants may interfere with the results. After adjustment for smoking, the authors found a direct causal effect of BMI on small cell lung cancer, and an inverse effect on lung adenocarcinoma. These results highlight that the effect of BMI varies significantly depending on histology.
Chronic liver disease (CLD) and cirrhosis are major sources of morbidity and mortality in the United States. Little is known about the epidemiology of these two diseases in ethnic minority ...populations in the United States. We examined the prevalence of CLD and cirrhosis by underlying etiologies among African Americans, Native Hawaiians, Japanese Americans, Latinos, and whites in the Multiethnic Cohort. CLD and cirrhosis cases were identified using Medicare claims between 1999 and 2012 among the fee‐for‐service participants (n = 106,458). We used International Classification of Diseases Ninth Revision codes, body mass index, history of diabetes mellitus, and alcohol consumption from questionnaires to identify underlying etiologies. A total of 5,783 CLD (3,575 CLD without cirrhosis and 2,208 cirrhosis) cases were identified. The prevalence of CLD ranged from 3.9% in African Americans and Native Hawaiians to 4.1% in whites, 6.7% in Latinos, and 6.9% in Japanese. Nonalcoholic fatty liver disease (NAFLD) was the most common cause of CLD in all ethnic groups combined (52%), followed by alcoholic liver disease (21%). NAFLD was the most common cause of cirrhosis in the entire cohort. By ethnicity, NAFLD was the most common cause of cirrhosis in Japanese Americans, Native Hawaiians, and Latinos, accounting for 32% of cases. Alcoholic liver disease was the most common cause of cirrhosis in whites (38.2%), while hepatitis C virus was the most common cause in African Americans (29.8%). Conclusions: We showed racial/ethnic variations in the prevalence of CLD and cirrhosis by underlying etiology; NAFLD was the most common cause of CLD and cirrhosis in the entire cohort, and the high prevalence of NAFLD among Japanese Americans and Native Hawaiians is a novel finding, warranting further studies to elucidate the causes. (Hepatology 2016;64:1969‐1977)
We compared fat storage in the abdominal region among individuals from 5 different ethnic–racial groups to determine whether fat storage is associated with disparities observed in metabolic syndrome ...and other obesity-associated diseases.
We collected data from 1794 participants in the Multiethnic Cohort Study (60–77 years old; of African, European white, Japanese, Latino, or Native Hawaiian ancestry) with body mass index values of 17.1–46.2 kg/m2. From May 2013 through April 2016, participants visited the study clinic to undergo body measurements, an interview, and a blood collection. Participants were evaluated by dual-energy x-ray absorptiometry and abdominal magnetic resonance imaging. Among ethnic groups, we compared adiposity of the trunk, intra-abdominal visceral cavity, and liver, adjusting for total fat mass; we evaluated the association of adult weight change with abdominal adiposity; and we examined the prevalence of metabolic syndrome mediated by abdominal adiposity.
Relative amounts of trunk, visceral, and liver fat varied significantly with ethnicity—they were highest in Japanese Americans, lowest in African Americans, and intermediate in the other groups. Compared with African Americans, the mean visceral fat area was 45% and 73% greater in Japanese American men and women, respectively, and the mean measurements of liver fat were 61% and 122% greater in Japanese American men and women. The visceral and hepatic adiposity associated with weight gain since participants were 21 years old varied in a similar pattern among ethnic–racial groups. In the mediation analysis, visceral and liver fat jointly accounted for a statistically significant fraction of the difference in metabolic syndrome prevalence, compared with white persons, for African Americans, Japanese Americans, and Native Hawaiian women, independently of total fat mass.
In an analysis of data from the participants in the Multiethnic Cohort Study, we found extensive differences among ethnic–racial groups in the propensity to store fat intra-abdominally. This observation should be considered by clinicians in the prevention and early detection of metabolic disorders.
In a population of almost 184,000 prospectively studied participants, the risk of lung cancer was ascertained according to the level of cigarette smoking and ethnic or racial background. Among those ...who smoked no more than 30 cigarettes per day, the relative risk of lung cancer was highest among African Americans and native Hawaiians, as compared with whites, Hispanics, and Japanese Americans.
Among those who smoked no more than 30 cigarettes per day, the relative risk of lung cancer was highest among African Americans and native Hawaiians, as compared with whites, Hispanics, and Japanese Americans.
The incidence of lung cancer is substantially higher among blacks, Native Hawaiians, and other Polynesians and lower among Japanese Americans and Hispanics than among whites in the United States.
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The vast majority (80 to 90 percent) of these cases are attributable to cigarette smoking. Smoking behavior also varies widely among these ethnic and racial groups. In aggregated population surveys conducted in the United States, the age-adjusted prevalence of cigarette smoking was 30.1 percent among black adults and 27.3 percent among white adults.
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Only 8.0 percent of black smokers, however, were reported to be heavy smokers (smoking at least 25 cigarettes . . .
To determine whether cancer risks for carriers and noncarriers from families with a mismatch repair (MMR) gene mutation are increased above the risks of the general population.
We prospectively ...followed a cohort of 446 unaffected carriers of an MMR gene mutation (MLH1, n = 161; MSH2, n = 222; MSH6, n = 47; and PMS2, n = 16) and 1,029 their unaffected relatives who did not carry a mutation every 5 years at recruitment centers of the Colon Cancer Family Registry. For comparison of cancer risk with the general population, we estimated country-, age-, and sex-specific standardized incidence ratios (SIRs) of cancer for carriers and noncarriers.
Over a median follow-up of 5 years, mutation carriers had an increased risk of colorectal cancer (CRC; SIR, 20.48; 95% CI, 11.71 to 33.27; P < .001), endometrial cancer (SIR, 30.62; 95% CI, 11.24 to 66.64; P < .001), ovarian cancer (SIR, 18.81; 95% CI, 3.88 to 54.95; P < .001), renal cancer (SIR, 11.22; 95% CI, 2.31 to 32.79; P < .001), pancreatic cancer (SIR, 10.68; 95% CI, 2.68 to 47.70; P = .001), gastric cancer (SIR, 9.78; 95% CI, 1.18 to 35.30; P = .009), urinary bladder cancer (SIR, 9.51; 95% CI, 1.15 to 34.37; P = .009), and female breast cancer (SIR, 3.95; 95% CI, 1.59 to 8.13; P = .001). We found no evidence of their noncarrier relatives having an increased risk of any cancer, including CRC (SIR, 1.02; 95% CI, 0.33 to 2.39; P = .97).
We confirmed that carriers of an MMR gene mutation were at increased risk of a wide variety of cancers, including some cancers not previously recognized as being a result of MMR mutations, and found no evidence of an increased risk of cancer for their noncarrier relatives.
Coffee consumption has been associated with reduced risk for death in prospective cohort studies; however, data in nonwhites are sparse.
To examine the association of coffee consumption with risk for ...total and cause-specific death.
The MEC (Multiethnic Cohort), a prospective population-based cohort study established between 1993 and 1996.
Hawaii and Los Angeles, California.
185 855 African Americans, Native Hawaiians, Japanese Americans, Latinos, and whites aged 45 to 75 years at recruitment.
Outcomes were total and cause-specific mortality between 1993 and 2012. Coffee intake was assessed at baseline by means of a validated food-frequency questionnaire.
58 397 participants died during 3 195 484 person-years of follow-up (average follow-up, 16.2 years). Compared with drinking no coffee, coffee consumption was associated with lower total mortality after adjustment for smoking and other potential confounders (1 cup per day: hazard ratio HR, 0.88 95% CI, 0.85 to 0.91; 2 to 3 cups per day: HR, 0.82 CI, 0.79 to 0.86; ≥4 cups per day: HR, 0.82 CI, 0.78 to 0.87; P for trend < 0.001). Trends were similar between caffeinated and decaffeinated coffee. Significant inverse associations were observed in 4 ethnic groups; the association in Native Hawaiians did not reach statistical significance. Inverse associations were also seen in never-smokers, younger participants (<55 years), and those who had not previously reported a chronic disease. Among examined end points, inverse associations were observed for deaths due to heart disease, cancer, respiratory disease, stroke, diabetes, and kidney disease.
Unmeasured confounding and measurement error, although sensitivity analysis suggested that neither was likely to affect results.
Higher consumption of coffee was associated with lower risk for death in African Americans, Japanese Americans, Latinos, and whites.
National Cancer Institute.
Previous studies using different exposure methods to assess air pollution and breast cancer risk among primarily whites have been inconclusive. Air pollutant exposures of particulate matter and ...oxides of nitrogen were estimated by kriging (NOx, NO2, PM10, PM2.5), land use regression (LUR, NOx, NO2) and California Line Source Dispersion model (CALINE4, NOx, PM2.5) for 57,589 females from the Multiethnic Cohort, residing largely in Los Angeles County from recruitment (1993–1996) through 2010. Cox proportional hazards models were used to examine the associations between time‐varying air pollution and breast cancer incidence adjusting for confounding factors. Stratified analyses were conducted by race/ethnicity and distance to major roads. Among all women, breast cancer risk was positively but not significantly associated with NOx (per 50 parts per billion ppb) and NO2 (per 20 ppb) determined by kriging and LUR and with PM2.5 and PM10 (per 10 μg/m3) determined by kriging. However, among women who lived within 500 m of major roads, significantly increased risks were observed with NOx (hazard ratio HR = 1.35, 95% confidence interval 95% CI: 1.02–1.79), NO2 (HR = 1.44, 95% CI: 1.04–1.99), PM10 (HR = 1.29, 95% CI: 1.07–1.55) and PM2.5 (HR = 1.85, 95% CI: 1.15–2.99) determined by kriging and NOx (HR = 1.21, 95% CI:1.01–1.45) and NO2 (HR = 1.26, 95% CI: 1.00–1.59) determined by LUR. No overall associations were observed with exposures assessed by CALINE4. Subgroup analyses suggested stronger associations of NOx and NO2 among African Americans and Japanese Americans. Further studies of multiethnic populations to confirm the effects of air pollution, particularly near‐roadway exposures, on the risk of breast cancer is warranted.
What's new?
Prior studies of air pollution and breast cancer generally have employed one method of exposure assessment and have focused on white women, with inconsistent results. Here, three exposure assessment methods, kriging interpolation, land use regression (LUR), and California Line Source Dispersion model (CALINE4), were used to investigate associations between long‐term air pollutant exposure and breast cancer risk in the Southern California Multiethnic Cohort. Breast cancer risk was increased in association with air pollution exposure among women residing near major roads according to kriging and LUR measures.
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