The association of a healthy lifestyle index and imaging-based body fat distribution with glycemic status and Type 2 diabetes in the Multi Ethnic Cohort: a cross-sectional analysis

INTRODUCTION

As several behaviors captured by the Lifestyle Risk Factor Index (LSRI) are protective against Type 2 diabetes (T2D) and may affect body fat distribution, we examined its relation with both outcomes.

METHODS

In a subset of the Multiethnic Cohort, participants from five ethnic groups (60-77 years) were assigned LSRI scores (one point each for consuming <1 (women)/<2 (men) alcoholic drinks/day, ≥1.5 physical activity hours/week, not smoking, and adhering to ≥3/7 dietary recommendations). All participants completed an extensive Quantitative Food Frequency Questionnaire to allow estimation of adherence to intake recommendations for fruits, vegetables, refined and whole grains, fish, processed and non-processed meat. Glycemic/T2D status was classified according to self-reports and fasting glucose. We estimated prevalence odds ratios (POR) of LSRI with glycemic/T2D status and DXA- and MRI-based body fat distribution using logistic regression.

RESULTS

Of 1713 participants, 43% had normoglycemia, 30% Pre-T2D, 9% Undiagnosed T2D, and 18% T2D. Overall, 39% scored 0-2, 49% 3, and 12% 4 LSRI points. T2D prevalence was 55% (POR 0.45; 95% confidence intervals 0.27, 0.76) lower for 4 vs. 0-2 LSRI points with weaker associations for abnormal glycemic status. Despite the low adherence to dietary recommendations (22%), this was the only component related to lower T2D prevalence. The inverse LSRI-T2D association was only observed among Latinos and Japanese Americans in ethnic-specific models. Visceral fat measures were higher in T2D patients and attenuated the LSRI-T2D association.

CONCLUSION

These findings support the role of a healthy lifestyle, especially diet, in T2D prevention with differences across ethnicity.

Racial and Ethnic Differences in the Population-Attributable Fractions of Alzheimer Disease and Related Dementias

BACKGROUND AND OBJECTIVES

Previous studies estimated that modifiable risk factors explain up to 40% of the dementia cases in the United States and that this population-attributable fraction (PAF) differs by race and ethnicity-estimates of future impact based on the risk factor prevalence in contemporary surveys. The aim of this study was to determine the race-specific and ethnicity-specific PAF of late-onset Alzheimer disease and related dementias (ADRDs) based on the risk factor prevalence and associations observed on the same individuals within a prospective cohort.

METHODS

Data were from Multiethnic Cohort Study participants (African American, Japanese American, Latino, Native Hawaiian, and White) enrolled in Medicare Fee-for-Service. We estimated the PAF based on the prevalence of risk factors at cohort baseline and their mutually adjusted association with subsequent ADRD incidence. Risk factors included low educational attainment and midlife exposures to low neighborhood socioeconomic status, unmarried status, history of hypertension, stroke, diabetes or heart disease, smoking, physical inactivity, short or long sleep duration, obesity, and low-quality diet, as well as APOE ε4 for a subset.

RESULTS

Among 91,881 participants (mean age 59.3 at baseline, 55.0% female participants), 16,507 incident ADRD cases were identified from Medicare claims (1999-2016, mean follow-up 9.3 years). The PAF for nongenetic factors combined was similar in men (24.0% [95% CI 21.3-26.6]) and women (22.8% [20.3-25.2]) but varied across Japanese American (14.2% [11.1-17.2]), White (21.9% [19.0-24.7]), African American (27.8% [22.3-33.0]), Native Hawaiian (29.3% [21.0-36.7]), and Latino (33.3% [27.5-38.5]) groups. The combined PAF was attenuated when accounting for competing risk of death, in both men (10.4%) and women (13.9%) and across racial and ethnic groups (4.7%-25.5%). The combined PAF was also different by age at diagnosis and ADRD subtypes, higher for younger (65-74 years: 43.2%) than older (75-84 years: 32.4%; ≥85 years: 11.3%) diagnoses and higher for vascular or unspecified ADRD than for AD or Lewy body dementia. An additional PAF of 11.8% (9.9-13.6) was associated with APOE ε4, which together with nongenetic risk factors accounted for 30.6% (25.8-35.1) of ADRD.

DISCUSSION

Known risk factors explained about a third of the ADRD cases but with unequal distributions across racial and ethnic groups.

Diet Quality and Body Mass Index Over 20 Years in the Multiethnic Cohort

BACKGROUND

With increasing rates of overweight and obesity and disparities by ethnicity, it is important to understand the role of diet in ameliorating this health problem.

OBJECTIVE

This study examined the relation of diet quality as measured by the Healthy Eating Index 2015 with body mass index (BMI; calculated as kg/m2) and obesity among participants of the Multiethnic Cohort (MEC) in cross-sectional analyses at 3 time points (T-1, T-2, and T-3) over 20 years.

DESIGN

In a subset of 1,860 MEC participants, 3 cross-sectional analyses at cohort entry (1993 to 1996, T-1) and follow-ups in 2003 to 2008 (T-2) and 2013 to 2016 (T-3) were performed.

PARTICIPANTS/SETTING

The cohort consists of African American, Native Hawaiian, Japanese American, Latino, and White adults in Hawaii and California; mean age was 48 years at T-1.

MAIN OUTCOME MEASURE

BMI and weight status in relation to diet quality were measured.

STATISTICAL ANALYSIS

Linear and multinomial logistic regressions were applied to analyze the relation of diet quality with BMI and obesity, while adjusting for known confounders.

RESULTS

Healthy Eating Index 2015 increased by 6.1 and 5.1 units for men and women, respectively, from T-1 to T-3; the respective values for BMI were 1.5 and 2.4. Diet quality was inversely associated with BMI across time: BMI was lower by -0.47, -0.72, and -0.92 units for every 10-point increase in Healthy Eating Index 2015 scores at T-1, T-2, and T-3, respectively (P < .0001 for all). During the 20 years, the association was consistently high among Japanese American participants (-0.79, -0.87, and -1.02) and weakest in African American cohort members (-0.34, -0.37, and -0.40). Higher diet quality was related to lower odds of having obesity at all 3 time points; prevalence odds ratios were 0.72, 0.57, and 0.60.

CONCLUSIONS

These findings suggest that consuming a high-quality diet is related to lower BMI and rates of overweight and obesity but with the strongest association at an older age. To understand the ethnic differences, investigations of dietary habits and behaviors and/or fat distribution patterns will be needed in the future.

Dietary intake and visceral adiposity in older adults: The Multiethnic Cohort Adiposity Phenotype study

Background

There are established links between the accumulation of body fat as visceral adipose tissue (VAT) and the risk of developing obesity-associated metabolic disease. Previous studies have suggested that levels of intake of specific foods and nutrients are associated with VAT accumulation after accounting for total energy intake.

Objective

This study assessed associations between a priori selected dietary factors on VAT quantified using abdominal magnetic resonance imaging.

Methods

The cross-sectional Multiethnic Cohort Adiposity Phenotype Study included n = 395 White, n = 274 Black, n = 269 Native Hawaiian, n = 425 Japanese American and n = 358 Latino participants (mean age = 69 years ± 3 SD). Participants were enrolled stratified on sex, race, ethnicity and body mass index. General linear models were used to estimate the mean VAT area (cm2) for participants categorized into quartiles based on their dietary intake of selected foods/nutrients adjusting for age, sex, racial and ethnic groups, the total percentage fat from whole-body dual energy X-ray absorptiometry and total energy.

Results

There were significant inverse associations with VAT for dietary intake of total vegetables, total fruits (including juice), cereals, whole grains, calcium, copper and dietary fiber (p-trend ≤0.04). Positive trends were observed for VAT for participants who reported higher intake of potatoes, total fat and saturated fatty acids (SFA) (p-trend ≤0.02). Foods/nutrients that met the multiple testing significance threshold were total fruits, whole grains, copper, dietary fiber and SFA intake.

Conclusions

These results highlight foods and nutrients including SFA, total fruit, whole grains, fiber and copper as potential candidates for future research to inform dietary guidelines for the prevention of chronic disease among older adults.

Association of Habitual Intake of Probiotic Supplements and Yogurt with Characteristics of the Gut Microbiome in the Multiethnic Cohort Adiposity Phenotype Study

Consumption of probiotics and/or yogurt could be a solution for restoring the balance of the gut microbiota. This study examined associations of regular intake of probiotic supplements or yogurt with the gut microbiota among a diverse population of older adults (N=1,861; 60-72 years). Fecal microbial composition was obtained from 16S rRNA gene sequencing (V1-V3 region). General Linear Models were used to estimate the associations of probiotic supplement or yogurt intake with microbiome measures adjusting for covariates. Compared to non-yogurt consumers (N=1,023), regular yogurt consumers (≥once/week, N=818) had greater Streptococcus (β=0.29, P=0.0003) and lower Odoribacter (β=-0.33, P<0.0001) abundance. The directions of the above associations were consistent across the five ethnic groups but stronger among Japanese Americans (Streptococcus: β=0.56, P=0.0009; Odoribacter: β=-0.62, P=0.0005). Regular intake of probiotic supplements (N=175) was not associated with microbial characteristics (i.e., alpha diversity and the abundance of 152 bacteria genera). Streptococcus is one of the predominant bacteria genera in yogurt products, which may explain the positive association between yogurt consumption and Streptococcus abundance. Our analyses suggest that changes in Odoribacter were independent of changes in Streptococcus abundance. Future studies may investigate whether these microbial genera and their sub-level species mediate potential pathways between yogurt consumption and health.

Modifying effects of race and ethnicity and APOE on the association of physical activity with risk of Alzheimer's disease and related dementias

INTRODUCTION

We investigated whether the protective association of physical activity with risk of Alzheimer's disease and related dementias (ADRD) has genetic or behavioral variations.

METHODS

In the Multiethnic Cohort, we analyzed moderate or vigorous physical activity (MVPA) reported at ages 45 to 75 among 88,047 participants in relation to 13,039 incident diagnoses of late-onset ADRD identified in Medicare claims (1999 to 2014), by five racial and ethnic groups, hours sitting, and in a subset (16%), apolipoprotein E (APOE) genotype.

RESULTS

MVPA was inversely associated with ADRD (hazard ratio for ≥14 vs <2.5 hours/week: 0.83, 95% confidence interval [CI]: 0.76 to 0.90 in men; 0.88, 5% CI: 0.81 to 0.95 in women). The association was inverse in all racial and ethnic groups except Black participants (P-heterogeneity = 0.52), but stronger in individuals with lower levels of sitting duration or those who do not carry the APOE e4 risk allele.

DISCUSSION

The different effects of physical activity by sitting duration and APOE genotype warrant further research.

Genome-wide association study of abdominal MRI-measured visceral fat: The multiethnic cohort adiposity phenotype study

Few studies have explored the genetic underpinnings of intra-abdominal visceral fat deposition, which varies substantially by sex and race/ethnicity. Among 1,787 participants in the Multiethnic Cohort (MEC)-Adiposity Phenotype Study (MEC-APS), we conducted a genome-wide association study (GWAS) of the percent visceral adiposity tissue (VAT) area out of the overall abdominal area, averaged across L1-L5 (%VAT), measured by abdominal magnetic resonance imaging (MRI). A genome-wide significant signal was found on chromosome 2q14.3 in the sex-combined GWAS (lead variant rs79837492: Beta per effect allele = -4.76; P = 2.62 × 10-8) and in the male-only GWAS (lead variant rs2968545: (Beta = -6.50; P = 1.09 × 10-9), and one suggestive variant was found at 13q12.11 in the female-only GWAS (rs79926925: Beta = 6.95; P = 8.15 × 10-8). The negatively associated variants were most common in European Americans (T allele of rs79837492; 5%) and African Americans (C allele of rs2968545; 5%) and not observed in Japanese Americans, whereas the positively associated variant was most common in Japanese Americans (C allele of rs79926925, 5%), which was all consistent with the racial/ethnic %VAT differences. In a validation step among UK Biobank participants (N = 23,699 of mainly British and Irish ancestry) with MRI-based VAT volume, both rs79837492 (Beta = -0.026, P = 0.019) and rs2968545 (Beta = -0.028, P = 0.010) were significantly associated in men only (n = 11,524). In the MEC-APS, the association between rs79926925 and plasma sex hormone binding globulin levels reached statistical significance in females, but not in males, with adjustment for total adiposity (Beta = -0.24; P = 0.028), on the log scale. Rs79837492 and rs2968545 are located in intron 5 of CNTNAP5, and rs79926925, in an intergenic region between GJB6 and CRYL1. These novel findings differing by sex and racial/ethnic group warrant replication in additional diverse studies with direct visceral fat measurements.

Racial, ethnic, and socioeconomic differences in a deficit accumulation frailty index in the Multiethnic Cohort Study

BACKGROUND

Frailty status has been sparsely studied in some groups including Native Hawaiians and Asian Americans.

METHODS

We developed a questionnaire-based deficit accumulation frailty index (FI) in the Multiethnic Cohort (MEC), and examined frailty status (robust, FI 0-<0.2, prefrail, FI 0.2-<0.35, and frail FI ≥0.35) among 29,026 men and 40,756 women.

RESULTS

After adjustment for age, demographic, lifestyle factors and chronic conditions, relative to White men, odds of being frail was significantly higher (34% to 54%) among African American, Native Hawaiian and other Asian American men while odds was significantly lower (36%) in Japanese American men and did not differ in Latino men. However, among men who had high school or less, none of the groups displayed significantly higher odds of prefrail or frail compared to White men. Relative to White women, odds of being frail were significantly higher (14% to 33%) in African American and Latino women, did not differ for other Asian American women and lower (14% to 36%) in Native Hawaiian and Japanese American women. These racial and ethnic differences in women were observed irrespective of education. Risk of all-cause mortality was higher in prefrail and frail men than robust men (adjusted hazard ratio (HR)=1.69, 1.59-1.81; HR=3.27, 3.03-3.53); results were similar in women. All cause-mortality was significantly positively associated with frailty status and frailty score across all sex, race and ethnic groups.

CONCLUSIONS

Frailty status differed significantly by race and ethnicity and was consistently associated with all-cause mortality. The FI may be a useful tool for aging studies in this multiethnic population.

Risk of Alzheimer's disease and related dementia by sex and race/ethnicity: The Multiethnic Cohort Study

INTRODUCTION

Data are limited for comparison of sex- and race/ethnicity-specific risks of Alzheimer's disease and related dementia (ADRD).

METHODS

In the population-based Multiethnic Cohort, we estimated the age-standardized diagnostic incidence rate (ASDIR) and relative risk of late-onset ADRD (n = 16,410) among 105,796 participants based on Medicare claims (1999-2014) by sex and race/ethnicity.

RESULTS

The ASDIR for ADRD was higher for women (17.0 per 1000 person-years) than for men (15.3) and varied across African Americans (22.9 in women, 21.5 in men), Native Hawaiians (19.3, 19.4), Latinos (16.8, 14.7), Whites (16.4, 15.5), Japanese Americans (14.8, 13.8), and Filipinos (12.5, 9.7). Similar risk patterns were observed for AD. Adjustment for education and cardiometabolic diseases attenuated the differences. Accounting for deaths from competing causes increased the sex difference, while reducing the racial/ethnic differences. Less racial/ethnic disparity was detected among apolipoprotein E (APOE) e4 carriers.

DISCUSSION

More research is needed to understand the sex and racial/ethnic differences in ADRD.

Body Fat Distribution, Glucose Metabolism, and Diabetes Status Among Older Adults: The Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

As the proportion of visceral (VAT) to subcutaneous adipose tissue (SAT) may contribute to type 2 diabetes (T2D) development, we examined this relation in a cross-sectional design within the Multiethnic Cohort that includes Japanese Americans known to have high VAT. The aim was to understand how ectopic fat accumulation differs by glycemic status across ethnic groups with disparate rates of obesity, T2D, and propensity to accumulate VAT.

METHODS

In 2013-2016, 1,746 participants aged 69.2 (standard deviation, 2.7) years from five ethnic groups completed questionnaires, blood collections, and whole-body dual X-ray absorptiometry and abdominal magnetic resonance imaging scans. Participants with self-reported T2D and/or medication were classified as T2D, those with fasting glucose >125 and 100-125 mg/dL as undiagnosed cases (UT2D) and prediabetes (PT2D), respectively. Using linear regression, we estimated adjusted means of adiposity measures by T2D status.

RESULTS

Overall, 315 (18%) participants were classified as T2D, 158 (9%) as UT2D, 518 (30%) as PT2D, and 755 (43%) as normoglycemic (NG), with significant ethnic differences (P < 0.0001). In fully adjusted models, VAT, VAT/SAT, and percent liver fat increased significantly from NG, PT2D, UT2D, to T2D (P < 0.001). Across ethnic groups, the VAT/SAT ratio was lowest for NG participants and highest for T2D cases. Positive trends were observed in all groups except African Americans, with highest VAT/SAT in Japanese Americans.

CONCLUSION

These findings indicate that VAT plays an important role in T2D etiology, in particular among Japanese Americans with high levels of ectopic adipose tissue, which drives the development of T2D to a greater degree than in other ethnic groups.

Associations of the Dietary Inflammatory Index with total adiposity and ectopic fat through the gut microbiota, LPS, and C-reactive protein in the Multiethnic Cohort-Adiposity Phenotype Study

BACKGROUND

Mechanisms linking a proinflammatory diet to obesity remain under investigation. The ability of diet to influence the gut microbiome (GM) in creating chronic low-grade systemic inflammation provides a plausible connection to adiposity.

OBJECTIVES

Assess whether any associations seen between the Energy-Adjusted Dietary Inflammatory Index (E-DII score), total fat mass, visceral adipose tissue (VAT), or liver fat (percentage volume) operated through the GM or microbial related inflammatory factors, in a multiethnic cross-sectional study.

METHODS

In the Multiethnic Cohort-Adiposity Phenotype Study (812 men, 843 women, aged 60-77 y) we tested whether associations between the E-DII and total adiposity, VAT, and liver fat function through the GM, LPS, and high-sensitivity C-reactive protein (hs-CRP). DXA-derived total fat mass, MRI-measured VAT, and MRI-based liver fat were measured. Participants provided stool and fasting blood samples and completed an FFQ. Stool bacterial DNA was amplified and the 16S rRNA gene was sequenced at the V1-V3 region. E-DII score was computed from FFQ data, with a higher E-DII representing a more proinflammatory diet. The associations between E-DII score, GM (10 phyla, 28 genera, α diversity), and adiposity phenotypes were examined using linear regression and mediation analyses, adjusting for confounders.

RESULTS

There were positive total effects (c) between E-DII and total fat mass (c = 0.68; 95% CI: 0.47, 0.90), VAT (c = 4.61; 95% CI: 2.95, 6.27), and liver fat (c = 0.40; 95% CI: 0.27, 0.53). The association between E-DII score and total fat mass was mediated by LPS, Flavonifractor, [Ruminococcus] gnavus group, and Tyzzerella. The association between E-DII score and ectopic fat occurred indirectly through Fusobacteria, Christensenellaceae R-7 group, Coprococcus 2, Escherichia-Shigella, [Eubacterium] xylanophilum group, Flavonifractor, Lachnoclostridium, [Ruminococcus] gnavus group, Tyzzerella, [Ruminococcus] gnavus group (VAT only), and α diversity (liver fat only). There was no significant association between E-DII score and adiposity phenotype through hs-CRP.

CONCLUSIONS

Associations found between E-DII and adiposity phenotypes occurred through the GM and LPS.

The joint association of cardiometabolic health and weight on mortality in the multiethnic cohort

Objective: While cardiometabolic abnormalities are associated with elevated risk of morbidity, they may not occur in all individuals with obesity. Less is known about associations with mortality, especially cancer mortality. This study examined associations between cardiometabolic-weight categories and mortality from cardiovascular disease (CVD), cancer, and all causes.Methods: Cox proportional hazards regressions of time to all-cause, CVD, and cancer mortalities were used to examine associations with cardiometabolic-weight status, in the Multiethnic Cohort (n=157,865). Cardiometabolic-weight status categories were: Metabolically Healthy Normal Weight, Metabolically Healthy Obese, Metabolically Healthy Overweight, Metabolically Unhealthy Normal Weight, Metabolically Unhealthy Obese, and Metabolically Unhealthy Overweight.Results: Higher mortality, especially for all-cause and CVD, was found for all metabolically unhealthy groups no matter the weight classification when compared to the Metabolically Healthy Normal Weight category across sex-ethnic groups. For all-cause mortality, a reduction in mortality was seen for males in the Metabolically Healthy Overweight category (HR: 0.88, 95% CI: 0.84, 0.93), especially for African American, Native Hawaiian, and Latino males. Mortality was elevated in the Metabolically Healthy Obese category for all-cause and CVD mortality in both sexes (HR_range: 1.08-1.93). Few associations were seen with cancer mortality.Conclusions: Past examinations of cardiometabolic-weight status and mortality have been hampered by a lack of diversity. In a racially/ethnically diverse population, metabolically unhealthy groups exhibited a substantially higher risk of death from all causes and CVD than metabolically healthy groups. A reduction in all-cause mortality was seen for some males classified as Metabolically Healthy Overweight; however, being classified as Metabolically Healthy Obese elevated mortality risk for males and females compared to Metabolically Healthy Normal Weight. Future research is needed to examine how sex-ethnic differences in body fat distribution and changes in weight over time influence associations between cardiometabolic-weight status and mortality.

Prognostic utility of self-reported sarcopenia (SARC-F) in the Multiethnic Cohort

BACKGROUND

Age-related loss in skeletal muscle mass, quality, and strength, known as sarcopenia, is a well-known phenomenon of aging and is determined clinically using methods such as dual-energy X-ray absorptiometry (DXA). However, these clinical methods to measure sarcopenia are not practical for population-based studies, and a five-question screening tool known as SARC-F has been validated to screen for sarcopenia.

METHODS

We investigated the relationship between appendicular skeletal lean mass/height² (ALM/HT² ) (kg/m² ) assessed by DXA and SARC-F in a subset of 1538 (778 men and 760 women) participants in the Multiethnic Cohort (MEC) Study after adjustment for race/ethnicity, age, and body mass index (BMI) at the time of DXA measurement. We then investigated the association between SARC-F and mortality among 71 283 (41 757 women and 29 526 men) participants in the MEC, who responded to the five SARC-F questions on a mailed questionnaire as part of the MEC follow-up in 2012-2016.

RESULTS

In women, SARC-F score was significantly inversely associated with ALM/HT² after adjusting for race/ethnicity, and age and BMI at DXA (r = -0.167, P < 0.001); the result was similar in men although it did not reach statistical significance (r = -0.056, P = 0.12). Among the 71 000+ MEC participants, SARC-F score ≥ 4, as an indicator of sarcopenia, was higher in women (20.9%) than in men (11.2%) (P < 0.0001) and increased steadily with increasing age (6.3% in <70 vs. 41.3% in 90+ years old) (P < 0.0001). SARC-F score ≥ 4 was highest among Latinos (30.8% in women and 16.1% in men) and lowest in Native Hawaiian women (15.6%) and Japanese American men (8.9%). During an average of 6.8 years of follow-up, compared with men with SARC-F score of 0-1 (indicator of no sarcopenia), men with SARC-F 2-3 (indicator of pre-sarcopenia) and SARC-F ≥ 4 had significantly increased risk of all-cause mortality [hazard ratio (HR) = 1.00, 1.77, 3.73, P < 0.001], cardiovascular disease (CVD) mortality (HR = 1.00, 1.85, 3.98, P < 0.001), and cancer mortality (HR = 1.00, 1.46, 1.96, P < 0.001) after covariate adjustment. Comparable risk association patterns with SARC-F scores were observed in women (all-cause mortality: HR = 1.00, 1.47, 3.10, P < 0.001; CVD mortality: HR = 1.00, 1.59, 3.54, P < 0.001; cancer mortality: HR = 1.00, 1.30, 1.77, P < 0.001). These significant risk patterns between SARC-F and all-cause mortality were found across all sex-race/ethnic groups considered (12 in total).

CONCLUSIONS

An indicator of sarcopenia, determined using SARC-F, showed internal validity against DXA and displayed racial/ethnic and sex differences in distribution. SARC-F was associated with all-cause mortality as well as cause-specific mortality.

Subcutaneous and visceral fat assessment by DXA and MRI in older adults and children

OBJECTIVE

Given the importance of body fat distribution in chronic disease development, feasible methods to assess body fat are essential. This study compared dual-energy x-ray absorptiometry (DXA) in measuring visceral and subcutaneous adipose tissue (VAT and SAT) with magnetic resonance imaging (MRI).

METHODS

VAT and SAT were assessed using similar DXA and MRI protocols among 1,795 elderly participants of the Adiposity Phenotype Study (APS) and 309 children/adolescents in Shape Up! Kids (SKids). Spearman correlations, Bland-Altman plots, and coefficients of determination (R2 ) assessed agreement between DXA and MRI measures.

RESULTS

DXA overestimated SAT values in APS (315 vs. 229 cm2 ) and SKids (212 vs. 161 cm2 ), whereas DXA underestimated VAT measures (141 vs. 167 cm2 ) in adults only. The correlations between DXA and MRI values were stronger for SAT than VAT (APS: r = 0.92 vs. 0.88; SKids: 0.90 vs. 0.74). Bland-Altman plots confirmed better agreement for SAT than VAT despite differences by sex, ethnicity, and weight status with respective R2 values for SAT and VAT of 0.88 and 0.84 (APS) and 0.81 and 0.69 (SKids).

CONCLUSION

These findings indicate that SAT by DXA reflects MRI measures in children and older adults, whereas agreement for VAT is weaker for individuals with low VAT levels.

The Gut Microbiome Is Associated with Circulating Dietary Biomarkers of Fruit and Vegetable Intake in a Multiethnic Cohort

BACKGROUND

Results from observational studies suggest high diet quality favorably influences the human gut microbiome. Fruit and vegetable consumption is often a key contributor to high diet quality.

OBJECTIVE

To evaluate measures of gut bacterial diversity and abundance in relation to serum biomarkers of fruit and vegetable intake.

DESIGN

Secondary analysis of cross-sectional data.

PARTICIPANTS AND SETTING

Men and women from Los Angeles, CA, and Hawai'i who participated in the Multiethnic Cohort-Adiposity Phenotype Study from 2013 to 2016 (N = 1,709).

MAIN OUTCOME MEASURES

Gut microbiome diversity and composition in relation to dietary biomarkers.

STATISTICAL ANALYSIS

Carotenoid (beta carotene, alpha carotene, cryptoxanthins, lutein, lycopene, and zeaxanthin), tocopherol (α, β + γ, and δ), and retinol concentrations were assessed in serum. The α and β diversity and composition of the gut microbiome were classified based on 16S rRNA gene sequencing of bacterial DNA from self-collected fecal samples. Global differences in microbial community profiles in relation dietary biomarkers were evaluated using multivariable permutational analysis of variance. Associations of α diversity (Shannon index), β diversity (weighted and unweighted UniFrac) with center log-ratio-transformed phyla and genera abundances were evaluated using linear regression, adjusted for covariates.

RESULTS

Increasing total carotenoid, beta carotene, alpha carotene, cryptoxanthin, and lycopene concentrations were associated with higher gut bacterial diversity (Shannon Index) (P < 0.001). Total tocopherol, α-tocopherol, and δ-tocopherol concentrations contributed significantly to more than 1% of the microbiome variation in gut bacterial community: total tocopherol: 1.74%; α-tocopherol: 1.70%; and δ-tocopherol: 1.16% (P < 0.001). Higher total carotenoid was associated with greater abundance of some genera relevant for microbial macronutrient metabolism (P < 0.001).

CONCLUSIONS

Objective biomarkers of fruit and vegetable intake, particularly carotenoids, were favorably associated with gut bacterial composition and diversity in this multiethnic population. These observations provide supportive evidence that fruit and vegetable intake is related to gut bacterial composition; more work is needed to elucidate how this influences host health.

Race/ethnicity-associated blood DNA methylation differences between Japanese and European American women: an exploratory study

BACKGROUND

Racial/ethnic disparities in health reflect a combination of genetic and environmental causes, and DNA methylation may be an important mediator. We compared in an exploratory manner the blood DNA methylome of Japanese Americans (JPA) versus European Americans (EUA).

METHODS

Genome-wide buffy coat DNA methylation was profiled among healthy Multiethnic Cohort participant women who were Japanese (JPA; n = 30) or European (EUA; n = 28) Americans aged 60-65. Differentially methylated CpGs by race/ethnicity (DM-CpGs) were identified by linear regression (Bonferroni-corrected P < 0.1) and analyzed in relation to corresponding gene expression, a priori selected single nucleotide polymorphisms (SNPs), and blood biomarkers of inflammation and metabolism using Pearson or Spearman correlations (FDR < 0.1).

RESULTS

We identified 174 DM-CpGs with the majority of hypermethylated in JPA compared to EUA (n = 133), often in promoter regions (n = 48). Half (51%) of the genes corresponding to the DM-CpGs were involved in liver function and liver disease, and the methylation in nine genes was significantly correlated with gene expression for DM-CpGs. A total of 156 DM-CpGs were associated with rs7489665 (SH2B1). Methylation of DM-CpGs was correlated with blood levels of the cytokine MIP1B (n = 146). We confirmed some of the DM-CpGs in the TCGA adjacent non-tumor liver tissue of Asians versus EUA.

CONCLUSION

We found a number of differentially methylated CpGs in blood DNA between JPA and EUA women with a potential link to liver disease, specific SNPs, and systemic inflammation. These findings may support further research on the role of DNA methylation in mediating some of the higher risk of liver disease among JPA.

Diet and Liver Adiposity in Older Adults: The Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

Diet plays a key role in the pathogenesis of nonalcoholic fatty liver disease. Limited data exist regarding specific nutrients and food groups and liver fat continuously, particularly among different ethnicities.

OBJECTIVES

We aimed to determine the relationship between usual dietary intake and accurately measured liver fat content in a multiethnic population.

METHODS

Participants from the Multiethnic Cohort were recruited into the cross-sectional Adiposity Phenotype Study including women and men aged 60-77 y and 5 race/ethnic groups (African American, Japanese American, Latino, Native Hawaiian, and white). They filled out a detailed FFQ and underwent abdominal MRI for liver fat quantification and whole-body DXA for total adiposity. Intake of a priori-selected dietary factors (total and macronutrient energy, specific micronutrients, and food groups) was analyzed in relation to liver fat by estimating the mean percentage liver fat for quartiles of each dietary factor in a general linear model that adjusted for age, sex, race/ethnicity, percentage body fat, and daily energy intake (kcal/d).

RESULTS

In total, 1682 participants (mean age: 69.2 y; 51% female) were included. Mean ± SD liver fat percentage was 5.7 ± 4.6. A significant positive association with liver fat was found across quartiles of percentage energy from fat, saturated fat, cholesterol, total red meat, red meat excluding processed red meat, and coffee (Bonferroni-adjusted P-trend < 0.05). A significant inverse association was observed for dietary fiber, vitamin C, and vitamin E (Bonferroni-adjusted P-trend < 0.05).

CONCLUSIONS

This study of ethnically diverse older adults shows that certain dietary factors, in particular red meat and saturated fat from red meat, were strongly associated with liver fat, whereas dietary fiber was inversely associated with liver fat, replicating some of the previous studies conducted mostly in whites.

Population-specific reference panels are crucial for genetic analyses: an example of the CREBRF locus in Native Hawaiians

Statistical imputation applied to genome-wide array data is the most cost-effective approach to complete the catalog of genetic variation in a study population. However, imputed genotypes in underrepresented populations incur greater inaccuracies due to ascertainment bias and a lack of representation among reference individuals, further contributing to the obstacles to study these populations. Here we examined the consequences due to the lack of representation by genotyping in a large number of self-reported Native Hawaiians (N = 3693) a functionally important, Polynesian-specific variant in the CREBRF gene, rs373863828. We found the derived allele was significantly associated with several adiposity traits with large effects (e.g. ~ 1.28 kg/m2 per allele in body mass index as the most significant; P = 7.5 × 10-5), consistent with the original findings in Samoans. Due to the current absence of Polynesian representation in publicly accessible reference sequences, rs373863828 or its proxies could not be tested through imputation using these existing resources. Moreover, the association signals at the entire CREBRF locus could not be captured by alternative approaches, such as admixture mapping. In contrast, highly accurate imputation can be achieved even if a small number (<200) of internally constructed Polynesian reference individuals were available; this would increase sample size and improve the statistical evidence of associations. Taken together, our results suggest the alarming possibility that lack of representation in reference panels could inhibit discovery of functionally important loci such as CREBRF. Yet, they could be easily detected and prioritized with improved representation of diverse populations in sequencing studies.

Long-term association between diet quality and characteristics of the gut microbiome in the multiethnic cohort study

As past usual diet quality may affect gut microbiome (GM) composition, we examined the association of the Healthy Eating Index (HEI)-2015 assessed 21 and 9 years before stool collection with measures of fecal microbial composition in a subset of the Multiethnic Cohort. A total of 5936 participants completed a validated quantitative FFQ (QFFQ) at cohort entry (Q1, 1993-1996), 5280 at follow-up (Q3, 2003-2008) and 1685 also at a second follow-up (Adiposity Phenotype Study (APS), 2013-2016). All participants provided a stool sample in 2013-2016. Fecal microbial composition was obtained from 16S rRNA gene sequencing (V1-V3 regions). HEI-2015 scores were computed based on each QFFQ. Using linear regression adjusted for relevant covariates, we calculated associations of HEI-2015 scores with gut microbial diversity and 152 individual genera. The mean HEI-2015 scores increased from Q1 (67 (sd 10)) to Q3 (71 (sd 11)) and APS (72 (sd 10)). Alpha diversity assessed by the Shannon Index was significantly higher with increasing tertiles of HEI-2015. Of the 152 bacterial genera tested, seven (Anaerostipes, Coprococcus_2, Eubacterium eligens, Lachnospira, Lachnospiraceae_ND3007, Ruminococcaceae_UCG-013 and Ruminococcus_1) were positively and five (Collinsella, Parabacteroides, Ruminiclostridium_5, Ruminococcus gnavus and Tyzzerella) were inversely associated with HEI-2015 assessed in Q1, Q3 and APS. The estimates of change per unit of the HEI-2015 score associated with the abundance of these twelve genera were consistent across the three questionnaires. The quality of past diet, assessed as far as ∼20 years before stool collection, is equally predictive of GM composition as concurrently assessed diet, indicative of the long-term consistency of this relation.

Genome-wide association study of pancreatic fat: The Multiethnic Cohort Adiposity Phenotype Study

Several studies have found associations between higher pancreatic fat content and adverse health outcomes, such as diabetes and the metabolic syndrome, but investigations into the genetic contributions to pancreatic fat are limited. This genome-wide association study, comprised of 804 participants with MRI-assessed pancreatic fat measurements, was conducted in the ethnically diverse Multiethnic Cohort-Adiposity Phenotype Study (MEC-APS). Two genetic variants reaching genome-wide significance, rs73449607 on chromosome 13q21.2 (Beta = -0.67, P = 4.50x10-8) and rs7996760 on chromosome 6q14 (Beta = -0.90, P = 4.91x10-8) were associated with percent pancreatic fat on the log scale. Rs73449607 was most common in the African American population (13%) and rs79967607 was most common in the European American population (6%). Rs73449607 was also associated with lower risk of type 2 diabetes (OR = 0.95, 95% CI = 0.89-1.00, P = 0.047) in the Population Architecture Genomics and Epidemiology (PAGE) Study and the DIAbetes Genetics Replication and Meta-analysis (DIAGRAM), which included substantial numbers of non-European ancestry participants (53,102 cases and 193,679 controls). Rs73449607 is located in an intergenic region between GSX1 and PLUTO, and rs79967607 is in intron 1 of EPM2A. PLUTO, a lncRNA, regulates transcription of an adjacent gene, PDX1, that controls beta-cell function in the mature pancreas, and EPM2A encodes the protein laforin, which plays a critical role in regulating glycogen production. If validated, these variants may suggest a genetic component for pancreatic fat and a common etiologic link between pancreatic fat and type 2 diabetes.

Biomarker-based visceral adiposity score and incident type 2 diabetes in the multiethnic cohort

PURPOSE

Visceral adipose tissue (VAT) may be more important than subcutaneous fat in type 2 diabetes (T2D) etiology. We examined a VAT score developed in reference to MRI measurement of VAT in the Multiethnic Cohort (MEC) as a risk factor for incident T2D.

METHODS

Two nested case-control studies of cancer allowed calculation of the VAT score based on anthropometric measures and 8 biomarkers among 2,556 participants without T2D. Incident cases were identified from Medicare linkages and self-reports after blood draws in 2001-2006. Cox regression with age as time metric was applied to estimate the association of the VAT score with T2D.

RESULTS

During 10.1 ± 2.4 years, 355 incident T2D cases were identified. VAT scores were higher in T2D cases than among those without disease (5.06±0.43 vs. 4.95±0.41; P<0.0001) and significantly associated with T2D (HR = 2.70; 95%CI 1.60, 4.58 per unit) with similar values in men (HR = 2.99; 95%CI 1.03, 8.73) and women (HR = 2.61; 95%CI 1.39, 4.91). A significant association was observed in all five ethnic groups but only statistically significant among Japanese Americans (HR = 6.24; 95%CI 2.34, 16.68).

CONCLUSION

These findings support that VAT as estimated by a biomarker-based score predicts T2D incidence beyond BMI in particular among older adults of Japanese ancestry.

The gut microbiome and type 2 diabetes status in the Multiethnic Cohort

BACKGROUND

The gut microbiome may play a role in inflammation associated with type 2 diabetes (T2D) development. This cross-sectional study examined its relation with glycemic status within a subset of the Multiethnic Cohort (MEC) and estimated the association of circulating bacterial endotoxin (measured as plasma lipopolysaccharide-binding protein (LBP)) with T2D, which may be mediated by C-reactive protein (CRP).

METHODS

In 2013-16, cohort members from five ethnic groups completed clinic visits, questionnaires, and stool and blood collections. Participants with self-reported T2D and/or taking medication were considered T2D cases. Those with fasting glucose >125 and 100-125 mg/dL were classified as undiagnosed (UT2D) and pre-diabetes (PT2D) cases, respectively. We characterized the gut microbiome through 16S rRNA gene sequencing and measured plasma LBP and CRP by standard assays. Linear regression was applied to estimate associations of the gut microbiome community structure and LBP with T2D status adjusting for relevant confounders.

RESULTS

Among 1,702 participants (59.9-77.4 years), 735 (43%) were normoglycemic (NG), 506 (30%) PT2D, 154 (9%) UT2D, and 307 (18%) T2D. The Shannon diversity index decreased (ptrend = 0.05), while endotoxin, measured as LBP, increased (ptrend = 0.0003) from NG to T2D. Of 10 phyla, Actinobacteria (ptrend = 0.007), Firmicutes (ptrend = 0.003), and Synergistetes (ptrend = 0.02) were inversely associated and Lentisphaerae (ptrend = 0.01) was positively associated with T2D status. Clostridium sensu stricto 1, Lachnospira, and Peptostreptococcaceae were less, while Escherichia-Shigella and Lachnospiraceae were more abundant among T2D patients, but the associations with Actinobacteria, Clostridium sensu stricto 1, and Escherichia-Shigella may be due metformin use. PT2D/UT2D values were closer to NG than T2D. No indication was detected that CRP mediated the association of LBP with T2D.

CONCLUSIONS

T2D but not PT2D/UT2D status was associated with lower abundance of SCFA-producing genera and a higher abundance of gram-negative endotoxin-producing bacteria suggesting that the gut microbiome may contribute to chronic systemic inflammation and T2D through bacterial translocation.

Food Intakes Mediate Ethnic Differences in the Gut Microbiome

Objectives

Gut microbial composition has been associated with diet quality and health outcomes and has also been found to vary across ethnic groups. We explored how ethnic differences in food consumption may mediate some of the ethnic variation in the gut microbiome (GM).

Methods

In a subset of 5,280 Multiethnic Cohort participants, based on a food frequency questionnaire administered in 2003–2008, we assessed overall diet quality using the Healthy Eating Index (HEI-2015; scores 0–100) and specific food consumption using the intake amounts of 10 component food groups used to define common diet quality indexes. GM composition was obtained from 16S rRNA gene sequencing of a stool sample (2013–2016; age 59–98 years) and estimated in genus proportions (as the centered log ratio (CLR) transformed counts). Using mediation analysis, we determined the % of the total ethnicity effect on the genus proportion for each of the ethnically divergent bacterial genera mediated by overall diet quality and component food groups, while adjusting for age, sex, total energy intake, body mass index, and antibiotics use.

Results

Overall diet quality was highest in Whites (mean HEI-2015 = 73.1) and African Americans (72.7), followed by Japanese Americans (71.3), Native Hawaiians (70.1) and Latinos (68.9). Of the 152 genera, 7 with the largest ethnic variation (CLR difference for the genus between most vs. least abundant ethnic group &gt; 1) were examined for mediation. Five genera showed significant mediation of their ethnic differences through diet (P &lt; 0.00,045 for Bonferroni correction), ranging from the −12% for Flavonifractor in African Americans vs. Whites mediated by vegetable intake to the 19% for Christensenellaceae R-7 group in Latinos vs. Whites mediated by overall diet quality. Large mediation effects were also seen by saturated fat for Ruminococcaceae NK4A214 in African Americans vs. Whites (18%) and by alcohol for Erysipelatoclostridium in Latinos vs. Whites (18%).

Conclusions

Overall diet quality and component foods may contribute substantially to ethnic differences in gut bacterial composition. These novel findings may help the development of targeted dietary interventions to improve the gut health of specific ethnic groups.

Funding Sources

This work was supported by the US National Cancer Institute (NCI) grants P01 CA168530, U01 CA164973, and P30 CA71789.

Associations of the Dietary Inflammatory Index With Total Adiposity and Ectopic Fat and the Mediating Effect of the Gut Microbiota

Objectives

To assess, in a large multiethnic cross-sectional study, associations between the Dietary Inflammatory Index (DII®) and total adiposity and ectopic fat, and whether these associations are mediated by gut microbiota (GM).

Methods

Analyses used data from 1,655 participants (812 men, 843 women, 60–77 y) in the Adiposity Phenotype Study. At clinic visit (2013–2015), DXA-based total fat mass, MRI-based visceral adipose tissue (VAT) area at L1-L5 (cm2), and liver fat (% volume) were measured. Participants provided a stool sample and completed a validated food frequency questionnaire (FFQ). Stool bacterial DNA was amplified and the V1-V3 region of the 16S rRNA gene was sequenced. As ratios, GM data were centered log-ratio transformed. DII score was computed from FFQ data, with a higher DII representing a more inflammatory diet. The relationships between DII, GM and adiposity phenotypes were examined using linear regression and mediation analyses. Bootstrap 95% CI were calculated for the indirect effect (IE).

Results

DII was positively associated with total fat mass (β = 0.71 kg), VAT (β = 4.73 cm2), and liver fat (β = 0.40%) (P-values &lt; 0.001). DII was negatively associated with Eubacterium xylanophilum (β = −2.86), and alpha diversity (β = −0.04), and positively associated with Tyzzerella (β = 5.78) (P-values &lt; 0.001). An inverse relationship was found between E. xylanophilum, VAT (β = −0.11 cm2), and liver fat (β = −0.01%), and between alpha diversity and liver fat (β = −0.93%) (P-values &lt; 0.001). Tyzzerella was positively associated with VAT (β = 0.04 cm2) (P &lt; 0.001). The total effect of DII on VAT was partially mediated by E. xylanophilum (IE = 0.30) and Tyzzerella (IE = 0.26). The association between DII and liver fat was partially mediated by E. xylanophilum (IE = 0.02) and alpha diversity (IE = 0.04). GM did not mediate the total effect between DII and total fat mass.

Conclusions

The total effect of DII on ectopic fat was partially mediated by lower bacterial diversity and E. xylanophilum, a butyrate-producing genera often inversely associated with inflammation. The association between DII and ectopic fat was also mediated by an abundance of Tyzzerella, a genus previously found to be associated with low-quality diets. Following an anti-inflammatory diet may minimize intra-abdominal fat, in part through the indirect effect of the gut microbiota.

Funding Sources

NIH, NCI.

Metabolic syndrome screening using visceral adipose tissue (VAT) from opportunistic MRI locations in a multi-ethnic population

OBJECTIVE

To determine if visceral adipose tissue (VAT) area measured through MRI can be used opportunistically to assess the presence of cardiometabolic risk factors and compare its performance to simpler adiposity measures.

METHODS

A cross-sectional analysis was carried out on a subset of 1683 participants (856 women) from the Adiposity Phenotype Study (mean age=69.2y; range 59.9-77.4). The association of total VAT area (sum of four cross sections, L1-L2, L2-L3, L3-L4, L4-L5) and each location, as well as BMI and body fat % (per SD) with the metabolic syndrome (MetSx) or its components was evaluated through logistic regression analysis.

RESULTS

Total VAT can be accurately predicted using all sites evaluated (R² range=0.82-0.96). In men, VAT did not show a superior association to MetSx compared to BMI in men. However, in women, VAT was consistently superior to BMI and body fat % in its association to MetSx, independent of ethnicity [odds ratio for BMI, body fat %and total VAT area=2.25 (95% CI: 1.93-2.62); 1.66 (95% CI: 1.36-2.03); 6.20 (95% CI: 4.69-8.21) respectively in all women]. Ethnic-specific odds ratios to MetSx in women ranged from 5.38 to 8.63 for total VAT area and 2.12-4.08 for BMI.

CONCLUSION

Total VAT area can be accurately predicted from individual VAT regions in men and women and offers superior association to BMI for MetSx in women but not in men for five ethnicities. Therefore, opportunistic screening for elevated VAT area in women may be warranted across multiple ethnic groups.

Associations of the gut microbiome with hepatic adiposity in the Multiethnic Cohort Adiposity Phenotype Study

Nonalcoholic fatty liver disease (NAFLD) is a risk factor for liver cancer and prevalence varies by ethnicity. Along with genetic and lifestyle factors, the gut microbiome (GM) may contribute to NAFLD and its progression to advanced liver disease. Our cross-sectional analysis assessed the association of the GM with hepatic adiposity among African American, Japanese American, White, Latino, and Native Hawaiian participants in the Multiethnic Cohort. We used MRI to measure liver fat and determine nonalcoholic fatty liver disease (NAFLD) status (n = 511 cases) in 1,544 participants, aged 60-77 years, with 12-53% overall adiposity (BMI of 17.8-46.2 kg/m2). The GM was measured by 16S rRNA gene sequencing and, on a subset, by metagenomic sequencing. Alpha diversity was lower overall with NAFLD and in certain ethnicities (African Americans, Whites, and Latinos). In models regressing genus on NAFLD status, 62 of 149 genera (40%) exhibited a significant interaction between NAFLD and ethnicity stratified analysis found 69 genera significantly associated with NAFLD in at least one ethnic group. No single genus was significantly associated with NAFLD across all ethnicities. In contrast, the same bacterial metabolic pathways were over-represented in participants with NAFLD regardless of ethnicity. Imputed secondary bile acid and carbohydrate pathways were associated with NAFLD, the latter of which was corroborated by metagenomics, although different genera in different ethnicities were associated with these pathways. Overall, we found that NAFLD was associated with altered bacterial composition and metabolism, and that bacterial endotoxin, assessed by plasma lipopolysaccharide binding protein (LBP), may mediate liver fat-associated systemic inflammation in a manner that seems to vary by ethnicity.

Genome-Wide Association Study of Liver Fat: The Multiethnic Cohort Adiposity Phenotype Study

The global rise in fatty liver is a major public health problem. Thus, it is critical to identify both global and population-specific genetic variants associated with liver fat. We conducted a genome-wide association study (GWAS) of percent liver fat and nonalcoholic fatty liver disease (NAFLD) assessed by magnetic resonance imaging in 1,709 participants from the population-based Multiethnic Cohort Adiposity Phenotype Study. Our participants comprised older adults of five U.S. racial/ethnic groups: African Americans (n = 277), Japanese Americans (n = 424), Latinos (n = 348), Native Hawaiians (n = 274), and European Americans (n = 386). The established missense risk variant rs738409 located in patatin-like phospholipase domain containing 3 (PNPLA3) at 22q13 was confirmed to be associated with percent liver fat (P = 3.52 × 10-15) but more strongly in women than men (P heterogeneity = 0.002). Its frequency correlated with the prevalence of NAFLD across the five ethnic/racial groups. Rs738409 was also associated with homeostasis model assessment of insulin resistance (HOMA-IR) (beta = 0.028; P = 0.009) and circulating levels of insulin (beta = 0.022; P = 0.020) and alanine aminotransferase (beta = 0.016; P = 0.030). A novel association of percent liver fat with rs77249491 (located at 6q13 between limb region 1 domain containing 1 [LMBRD1] and collagen type XIX alpha 1 chain [COL19A1] (P = 1.42 × 10-8) was also observed. Rs7724941 was associated with HOMA-IR (beta = 0.12; P = 0.0005), insulin (beta = 0.11; P = 0.0003), triglycerides (beta = 0.059; P = 0.01), high-density lipoprotein (beta = -0.046; P = 0.04), and sex hormone binding globulin (beta = -0.084; P = 0.0012). This variant was present in Japanese Americans (minor allele frequency [MAF], 8%) and Native Hawaiians (MAF, 2%). Conclusion: We replicated the PNPLA3 rs738409 association in a multiethnic population and identified a novel liver fat risk variant in Japanese Americans and Native Hawaiians. GWASes of percent liver fat in East Asian and Oceanic populations are needed to replicate the rs77249491 association.

Associations of plasma trimethylamine N-oxide, choline, carnitine, and betaine with inflammatory and cardiometabolic risk biomarkers and the fecal microbiome in the Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

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.

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Abstract IA38: Racial/ethnic differences in liver fat, an obesity-associated risk factor for liver cancer

Background: Nonalcoholic fatty liver disease (NAFLD) is thought to be the main driver for the recent rise of chronic liver disease and liver cancer. NAFLD is also associated with other obesity-related metabolic diseases. Relative fat deposition in the liver varies by race/ethnicity and may partially account for liver cancer disparities. Thus, we aimed to compare liver fat content across five racial/ethnic groups, assess their contribution to the metabolic syndrome (MetSx), and predict NAFLD using common blood biomarkers.

Methods: We conducted a cross-sectional study within the Multiethnic Cohort. A total of 1,861 healthy men and women aged 60-77 years were recruited, after stratification on sex, ethnicity (African, Japanese, Latino, Native Hawaiian, or white ancestry), and six BMI categories (range, 17.1-49.8 kg/m2). We estimated total fat mass using DXA and liver fat content using abdominal MR imaging. Fasting blood was analyzed for ~50 markers including adipocytokines, insulin and IGFs, lipids and lipid-soluble micronutrients, liver enzymes, and steroid hormones, using multiple assay platforms. Liver fat amounts were compared across sex and ethnic groups after adjustment for age, total fat mass, and height. The contribution of liver fat to MetSx was estimated in multivariable-adjusted mediation analysis. A prediction model for NAFLD was developed using regularized logistic regression.

Results: The correlation between liver fat and total fat was only moderate (rSp = 0.34) and varied across ethnic groups (0.20-0.55). Liver fat content was similar between the sexes but differed by ethnicity (p&lt;.0001), with a four-fold range in NAFLD prevalence between Japanese Americans (57% in men, 72% in women) and African Americans (12%, 19%) after adjustment for total fat mass. Total fat-adjusted prevalence of MetSx also differed by ethnicity: compared to whites, it was higher among Japanese Americans and Native Hawaiian women and lower among African Americans and Latinos. This ethnic difference was significantly mediated by liver fat among African Americans (proportion mediated =19-24%), Japanese Americans (22-34%), and Native Hawaiian women (20%). The final prediction model for NAFLD included age, sex, BMI, waist circumference, waist/hip, and top five biomarker predictors (IGFBP2, HOMA-IR, TG, adiponectin, SHBG). Discrimination of NAFLD cases in a validation dataset had high accuracy (AUC=0.90), across ethnic groups (AUCs of 0.80-0.96), and was significantly improved by the biomarkers (p's for contrast&lt;.0001, except in African Americans).

Conclusions: Relative fat storage in the liver varies substantially by race/ethnicity. In particular, Japanese Americans and Native Hawaiian women appear to experience a greater metabolic burden from their propensity to store excess fat in ectopic areas, which is consistent with a stronger association of BMI with liver cancer in these groups. Key metabolism markers may be used to successfully detect and monitor NAFLD patients of in various ethnic groups.

Citation Format: Unhee Lim, Lynne R. Wilkens, Kristine R. Monroe, Iona Cheng, Bruce S. Kristal, Johanna W. Lampe, Meredith A. Hullar, John Shepherd, Thomas Ernst, Loic Le Marchand. Racial/ethnic differences in liver fat, an obesity-associated risk factor for liver cancer [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr IA38.

Abstract A31: Genome-wide association study (GWAS) of host DNA sequence variation and the gut microbiome in the Multiethnic Cohort

Patterns of microbiome diversity vary across human populations, and although variation is largely driven by diet and lifestyle, genetically encoded differences between hosts may be important in shaping the microbiome and health outcomes, including cancer. We report preliminary results from a GWAS of the gut microbiome in 6,217 individuals from the Multiethnic Cohort Study, including African Americans, Japanese Americans, Native Hawaiians, Latinos, and Whites. Genome-wide SNP data was based on existing data from a variety of Illumina Infinium arrays (500,000 to 2.5 million single nucleotide polymorphisms (SNPs); n=4,363) as well as genotyping 1,853 individuals using the Illumina MEGA EX array. SNP imputation was conducted using a cosmopolitan reference panel of all 1000 Genomes samples. The stool microbiome was assessed by paired-end sequencing (Illumina MiSeq) of the16S rRNA gene (V1-3). SNP-genera association tests were conducted using linear regression of covariate-adjusted bacterial genera abundance quintiles on SNP genotype. The chi-square statistics were adjusted by the genomic inflation factor. A threshold of p=5 × 10−8 was used to determine genome-wide statistical significance. The covariate-adjusted genera values were computed as the residuals of a logistic ordinal regression of genera abundance quintiles on variables expected to affect the microbiome (i.e., age, sex, genetic ancestry proportions, sample month, and sequencing batch). Initial results yielded 22 genome-wide significant associations across SNPs in 15 different human chromosomes and 11 bacterial genera. Notably, Fusobacteria was significantly associated with star-related lipid transfer domain (STARD3, chromosome 13q13; p=2.8 × 10−8), voltage-dependent calcium channel gamma 3 subunit (CACNG3, chromosome 16p12; p=3.1 × 10−8), organic anion transporter polypeptide (OATP, SCLO2B1, chromosome 11q13; p=2.8 × 10−8), and E-cadherin (CDHR3, chromosome 7q22, p=1.6 × 10−8). Some Fusobacterial species have been associated with increased risk of colon tumors. Coprobacillus was significantly associated with ubiquitin modifier activating enzyme 2 (UBA2, chromosome 19q13, p=4.1 × 10−9). The pathogen Slackia was significantly associated with variants in the zinc finger 850 gene (ZNF850, chromosome 19p13; p=4.3 × 10−8). These results suggest that host gene variants may be important in shaping the microbiome and may influence bacterial pathogen-associated cancer outcomes.

Citation Format: Meredith A. Hullar, Johanna W. Lampe, Timothy Randolph, Keith R. Curtis, Unhee Lim, Lynne R. Wilkens, Loic Le Marchand, Bruce S. Kristal, Kris R. Monroe, Kechen Zhao, Daniel Stram, Iona Cheng. Genome-wide association study (GWAS) of host DNA sequence variation and the gut microbiome in the Multiethnic Cohort [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr A31.

Circulating Biomarker Score for Visceral Fat and Risks of Incident Colorectal and Postmenopausal Breast Cancer: The Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

Visceral adipose tissue (VAT) may play a greater role than subcutaneous fat in increasing cancer risk but is poorly estimated in epidemiologic studies.

METHODS

We developed a VAT prediction score by regression equations averaged across 100 least absolute shrinkage and selection operator models in a cross-sectional study of 1,801 older adults in the Multiethnic Cohort (MEC). The score was then used as proxy for VAT in case-control studies of postmenopausal breast (950 case-control pairs) and colorectal (831 case-control pairs) cancer in an independent sample in MEC. Abdominal MRI-derived VAT; circulating biomarkers of metabolic, hormonal, and inflammation dysfunctions; and ORs for incident cancer adjusted for BMI and other risk factors were assessed.

RESULTS

The final score, composed of nine biomarkers, BMI, and height, explained 11% and 15% more of the variance in VAT than BMI alone in men and women, respectively. The area under the receiver operator curve for VAT >150 cm² was 0.90 in men and 0.86 in women. The VAT score was associated with risk of breast cancer [OR (95% confidence interval [CI]) by increasing tertiles: 1.00, 1.09 (0.86-1.39), 1.48 (1.16-1.89); P _trend = 0.002] but not with colorectal cancer (P = 0.84), although an association [1.00, 0.98 (0.68-1.39), 1.24 (0.88-1.76); P _trend = 0.08] was suggested for this cancer after excluding cases that occurred within 7 years of blood draw (P _{heterogeneity} = 0.06).

CONCLUSIONS

The VAT score predicted risks of postmenopausal breast cancer and can be used for risk assessment in diverse populations.

IMPACT

These findings provide specific evidence for a role of VAT in breast cancer.

Association of Imaging-Based Body Fat Distribution and Mammographic Density in the Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

As the stronger association of obesity with postmenopausal breast cancer in Asian than white women may be due to body fat distribution, we examined the relation of adiposity measures with percent mammographic density (PMD), a strong predictor of breast cancer incidence.

METHODS

A total of 938 women from five ethnic groups (69.1 ± 2.7 years) in the Adiposity Phenotype Study (APS) underwent DXA and MRI imaging. PMD was assessed in routine mammograms using a computer-assisted method. Spearman correlation coefficients were computed and general linear models were applied to estimate regression coefficients (β) for PMD per 0.5 SD units of adiposity measures while adjusting for known confounders, including DXA total body fat.

RESULTS

For 701 (75%) of the participants (69.1 ± 2.7 years), valid mammograms were obtained. Whereas total body fat, the trunk-to-periphery fat ratio (TPFR), visceral fat (VAT), and subcutaneous fat (SAT) were inversely correlated with PMD (P < 0.0001), the VAT/SAT ratio correlated positively (r _spearman = 0.10; P = 0.01). In fully adjusted models, PMD remained inversely related to TPFR and SAT and disappeared for VAT, while it was strengthened for VAT/SAT (β = 0.51; P = 0.009). This relation was stronger in Japanese Americans than other ethnic groups.

CONCLUSIONS

This is the first study to show an association of a high VAT/SAT ratio with greater PMD, a marker of breast cancer risk after taking into account total body fat.

IMPACT

The results indicate a link between the propensity to accumulate VAT and the amount of fat in the breast (1-PMD), which may influence the relation of obesity with breast cancer incidence.

Fecal Microbial Diversity and Structure Are Associated with Diet Quality in the Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

Variation in gut microbial community structure is partly attributed to variations in diet. A priori dietary indexes capture diet quality and have been associated with chronic disease risk.

OBJECTIVES

The aim of this study was to examine the association of diet quality, as assessed by the Healthy Eating Index, Alternative Healthy Eating Index-2010, alternate Mediterranean Diet, and the Dietary Approaches to Stop Hypertension Trial, with measures of fecal microbial community structure assessed in the Adiposity Phenotype Study (APS), an ethnically diverse study population with varied food intakes.

METHODS

Multiethnic Cohort Study members completed a validated quantitative food frequency questionnaire (QFFQ) at cohort entry (1993-1996) and, for the APS subset, at clinic visit (2013-2015), when they also provided a stool sample. DNA was extracted from stool, and the V1-V3 region of the 16S rRNA gene was amplified and sequenced. Dietary index scores were computed based on the QFFQ and an extensive nutritional database. Using linear regression adjusted for relevant covariates, we estimated associations of dietary quality with microbiome measures and computed adjusted mean values of microbial measures by tertiles of dietary index scores.

RESULTS

The 858 men and 877 women of white, Japanese American, Latino, Native Hawaiian, and African American ancestry had a mean age of 69.2 years at stool collection. Alpha diversity according to the Shannon index increased by 1-2% across tertiles of all 4 diet indexes measured at clinic visit. The mean relative abundance of the phylum Actinobacteria was 13-19% lower with higher diet quality across all 4 indexes (difference between tertile 3 and tertile 1 divided by tertile 1). Of the 104 bacterial genera tested, 21 (primarily from the phylum Firmicutes) were positively associated with at least 1 index after Bonferroni adjustment.

CONCLUSION

Diet quality was strongly associated with fecal microbial alpha diversity and beta diversity and several genera previously associated with human health.

Diet Quality and Biomarker Profiles Related to Chronic Disease Prevention: The Multiethnic Cohort Study

Objective: To understand how diet quality affects chronic disease etiology, the associations of 4 a priori diet quality indices with blood levels of lipid-soluble micronutrients and biomarkers of inflammation, lipid, and glucose metabolism were examined in 5 ethnic groups.Methods: In a cross-sectional design, the Adiposity Phenotype Study, a subset of the Multiethnic Cohort in Hawaii and Los Angeles, recruited participants of white, African American, Native Hawaiian, Japanese American, and Latino ancestry. A total of 896 men and 910 women completed a validated quantitative food frequency questionnaire and anthropometric measurements and donated a fasting blood sample. Using general linear models, covariate-adjusted mean levels of lipid-soluble micronutrients (total carotenes, lycopene, total tocopherols, total lutein, cryptoxanthins), biomarkers of inflammation (C-reactive protein [CRP], tumor necrosis factor-[Formula: see text]), adipokines (adiponectin, leptin), lipids (total cholesterol, high-density lipoprotein cholesterol [HDL-C], triglycerides), and glucose metabolism (glucose, insulin, homeostatic model assessment of insulin resistance [HOMA-IR]) were computed across tertiles of 4 a priori dietary indices Healthy Eating Index (HEI)-2010, Alternative HEI (AHEI)-2010, alternate Mediterranean Diet (aMED), Dietary Approaches to Stop Hypertension (DASH); trends were evaluated in models with diet quality scores as continuous variables.Results: With better diet quality, levels of carotenes, lutein, cryptoxanthin, adiponectin, and HDL-C were significantly higher (p_trend < 0.01), whereas levels of CRP, leptin, total cholesterol, triglycerides, glucose, insulin, and HOMA-IR were inversely associated (p_trend < 0.05) with diet quality. With the exception of cryptoxanthins and triglycerides, the associations were consistent across ethnic groups.Conclusions: These findings confirm the association between diet quality and nutrition-related biomarkers and support the idea that a high-quality diet positively influences biologic pathways involved in chronic disease etiology across different ethnic groups.

Effects of Intermittent Energy Restriction Combined with a Mediterranean Diet on Reducing Visceral Adiposity: A Randomized Active Comparator Pilot Study

Intermittent energy restriction combined with a Mediterranean diet (IER+MED) has shown promise to reduce body fat and insulin resistance. In the Multiethnic Cohort Adiposity Phenotype Study, Japanese Americans had the highest visceral adipose tissue (VAT) when adjusting for total adiposity. We conducted this pilot study to demonstrate feasibility and explore efficacy of following IER+MED for 12 weeks to reduce VAT among East Asians in Hawaii. Sixty volunteers (aged 35-55, BMI 25-40 kg/m2, VAT ≥ 90 cm2 for men and ≥ 80 cm2 for women) were randomized to IER+MED (two consecutive days with 70% energy restriction and 5 days euenergetic MED) or an active comparator (euenergetic Dietary Approaches to Stop Hypertension (DASH) diet). Participants and clinic staff (except dietitians) were blinded to group assignments. IER+MED had significantly larger reductions in DXA-measured VAT and total fat mass (-22.6 ± 3.6 cm2 and -3.3 ± 0.4 kg, respectively) vs. DASH (-10.7 ± 3.5 cm2 and -1.6 ± 0.4 kg) (p = 0.02 and p = 0.005). However, after adjusting for total fat mass, change in VAT was not statistically different between groups; whereas, improvement in alanine transaminase remained significantly greater for IER+MED vs. DASH (-16.2 ± 3.8 U/L vs. -4.0 ± 3.6 U/L, respectively, p = 0.02). Attrition rate was 10%, and participants adhered well to study prescriptions with no reported major adverse effect. Results demonstrate IER+MED is acceptable, lowers visceral and total adiposity among East Asian Americans, and may improve liver function more effectively than a healthful diet pattern. ClinicalTrials.gov Identifier: NCT03639350.

Genetic analyses of diverse populations improves discovery for complex traits

Genome-wide association studies (GWAS) have laid the foundation for investigations into the biology of complex traits, drug development and clinical guidelines. However, the majority of discovery efforts are based on data from populations of European ancestry^1-3. In light of the differential genetic architecture that is known to exist between populations, bias in representation can exacerbate existing disease and healthcare disparities. Critical variants may be missed if they have a low frequency or are completely absent in European populations, especially as the field shifts its attention towards rare variants, which are more likely to be population-specific^4-10. Additionally, effect sizes and their derived risk prediction scores derived in one population may not accurately extrapolate to other populations^11,12. Here we demonstrate the value of diverse, multi-ethnic participants in large-scale genomic studies. The Population Architecture using Genomics and Epidemiology (PAGE) study conducted a GWAS of 26 clinical and behavioural phenotypes in 49,839 non-European individuals. Using strategies tailored for analysis of multi-ethnic and admixed populations, we describe a framework for analysing diverse populations, identify 27 novel loci and 38 secondary signals at known loci, as well as replicate 1,444 GWAS catalogue associations across these traits. Our data show evidence of effect-size heterogeneity across ancestries for published GWAS associations, substantial benefits for fine-mapping using diverse cohorts and insights into clinical implications. In the United States-where minority populations have a disproportionately higher burden of chronic conditions¹³-the lack of representation of diverse populations in genetic research will result in inequitable access to precision medicine for those with the highest burden of disease. We strongly advocate for continued, large genome-wide efforts in diverse populations to maximize genetic discovery and reduce health disparities.

Proton Magnetic Resonance Spectroscopy (1H-MRS)-Based Neurometabolite Levels and Cognitive Function in Relation to Visceral Obesity and Non-Alcoholic Fatty Liver Disease (P14-019-19)

Objectives

Intra-abdominal adiposity in the viscera and liver, compared to total adiposity, carries a higher metabolic risk, and it varies substantially by sex and race. We examined the association of neurometabolites and cognitive function with visceral obesity and non-alcoholic fatty liver disease (NAFLD) in multiethnic older adults.

Methods

The Multiethnic Cohort Brain-Gut-Adiposity Study included 100 participants aged 61–77 years, who were recruited into balanced strata by sex, ancestry (Japanese, Native Hawaiian or white) and body mass index (BMI) levels (range: 18.0–44.9 kg/m2). We measured the concentration of key brain metabolites in the frontal and parietal gray matter (GM) and frontal white matter using 1H-MRS and assessed cognitive function using the Modified Mini-Mental State (3MS) and the NIH Toolbox (NIHTB) tests. Mean neurometabolite levels and cognition scores were compared by visceral obesity (visceral fat area at L1-L5 > 150 cm2) and NAFLD (liver fat >5.0%) status determined by abdominal MR imaging, while adjusting for age, sex, race, education, dual energy X-ray absorptiometry-based total adiposity and other confounders.

Results

The prevalence of visceral obesity was 52%, NAFLD 32%, and both conditions 27%. Participants with visceral obesity had higher adjusted mean levels of total glutamate [11.6 (11.3, 12.0) vs. 10.8 (10.4, 11.2) mM/kg; P = 0.01] and myo-inositol [5.2 (5.0, 5.4) vs. 4.7 (4.6, 4.9) mM/kg; P = 0.004] in the parietal GM but had similar levels of total choline, total creatine and N-acetylaspartate. NAFLD status was not significantly associated with the levels of neurometabolites. No significant interaction was detected between the two conditions: participants with either condition compared to those with neither showed a trend toward higher levels of myo-inositol [5.2 (4.9, 5.5) vs. 4.8 (4.5, 5.0) mM/kg; P = 0.07]. Further, participants with NAFLD scored lower for crystallized cognition for language [113 (110, 117) vs. 118 (116, 120); P = 0.02], in particular for reading ability [113 (109, 117) vs. 119 (117, 123); P = 0.03].

Conclusions

Results of this comprehensive, pilot imaging study suggest that, regardless of total adiposity and race/ethnicity, high visceral adiposity is associated with elevated concentrations of inflammatory neurometabolites, and NAFLD is associated with reduced language abilities.

Funding Sources

National Institutes of Health (National Institute of Diabetes and Digestive and Kidney Diseases and National Cancer Institute).

Does Intermittent Energy Restriction Plus Mediterranean Diet Reduce Visceral Adipose Tissue and Minimize Adaptive Responses of Energy Restriction? A Randomized Pilot Study (P21-016-19)

Objectives

Test if an intermittent energy restriction with a Mediterranean diet (IER + MED) preferentially promotes loss of visceral adipose tissue (VAT) over subcutaneous adipose tissue (SAT), with minimal changes to resting energy expenditure (REE) and physical activity level (PAL), compared to an active control, the Dietary Approaches to Stop Hypertension (DASH) diet, in an East Asian adult population.

Methods

Men and women in Hawai'i (n = 60, aged 35–55, BMI 25–40, VAT ≥ 90cm2 for men and ≥ 80cm2 for women) of East Asian origin, were randomized equally to IER + MED (2 days with 70% energy restriction and 5 days euenergetic MED) or a 7 day euenergetic DASH diet for 12 weeks. Dual energy X-ray absorptiometry (DXA) for estimation of VAT and abdominal SAT, REE through indirect calorimetry, and physical activity questionnaires were collected at baseline and week 12. Four-days mobile food records were completed at baseline, weeks 5–6 and 11.

Results

At week 12, participants in the IER + MED group lost greater amounts of VAT (−22.6 ± 3.6 cm2 vs. −10.7 ± 3.5 cm2 in DASH, P = 0.022) and SAT (−48.2 ± 6.4 cm2 vs. −15.0 ± 6.1 cm2 in DASH, P < 0.001). The IER + MED diet did not preferentially promote loss of VAT over SAT compared to DASH. Changes in VAT: SAT were 0.01 ± 0.01 for both groups (IER + MED vs. DASH, P = 0.825). Mean daily energy intake reductions at week 11 were larger in IER + MED (27%) than DASH (16%); and mean loss of weight at week 12 was higher in the IER + MED group (−5.9 ± 0.7 kg vs. −3.3 ± 0.6 kg in DASH, P = 0.007). Despite the significant drop in energy and weight for IER + MED, there was a non-significant change in REE of −105 ± 56 kcal/day for IER + MED (P = 0.068) and −25 ± 57 kcal/day for DASH (P = 0.663). Hours of moderate-to-vigorous physical activity per day were 1.6 ± 0.2 for IER + MED and 1.4 ± 0.3 for DASH at baseline and did not change significantly over 12 weeks.

Conclusions

In this short-term pilot study, the IER + MED diet was more effective at reducing VAT, SAT and weight; however, it did not preferentially promote loss of VAT over SAT, as compared to the active control DASH group. Loss of VAT, SAT and weight from the IER + MED diet may be sustainable long term as REE and PAL, which commonly decrease with large energy restriction, did not significantly change over 12 weeks.

Funding Sources

The William & Ellen Melohn Endowed Research Fund, University of Hawaii; National Institutes of Health, National Cancer Institute.

Propensity for Intra-abdominal and Hepatic Adiposity Varies Among Ethnic Groups

BACKGROUND & AIMS

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Circulating 25-hydroxyvitamin D up to 3 decades prior to diagnosis in relation to overall and organ-specific cancer survival

While vitamin D has been associated with improved overall cancer survival in some investigations, few have prospectively evaluated organ-specific survival. We examined the accepted biomarker of vitamin D status, serum 25-hydroxyvitamin D [25(OH)D], and cancer survival in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Of 4616 cancer cases with measured serum 25(OH)D, 2884 died of their cancer during 28 years of follow-up and 1732 survived or died of other causes. Proportional hazards regression estimated hazard ratios (HR) and 95% confidence intervals (CI) for the association between pre-diagnostic 25(OH)D and overall and site-specific survival. Serum 25(OH)D was significantly lower among cases who subsequently died from their malignancy compared with those who did not (medians 34.7 vs. 36.5 nmol/L, respectively; p = 0.01). Higher 25(OH)D was associated with lower overall cancer mortality (HR = 0.76, 95% CI 0.67-0.85 for highest vs. lowest quintile, p-trend < 0.0001). Higher 25(OH)D was related to lower mortality from the following site-specific malignancies: prostate (HR = 0.74, 95% CI 0.55-1.01, p-trend = 0.005), kidney (HR = 0.59, 95% CI 0.35-0.98, p-trend = 0.28), and melanoma (HR = 0.39, 95% CI 0.20-0.78, p-trend = 0.01), but increased mortality from lung cancer (HR = 1.28, 95% CI 1.02-1.61, p-trend = 0.19). Improved survival was also suggested for head and neck, gastric, pancreatic, and liver cancers, though not statistically significantly, and case numbers for the latter two organ sites were small. Higher 25(OH)D status years prior to diagnosis was related to improved survival for overall and some site-specific cancers, associations that should be examined in other prospective populations that include women and other racial-ethnic groups.

Methylation of imprinted IGF2 regions is associated with total, visceral, and hepatic adiposity in postmenopausal women

Excess body fat, especially intra-abdominal fat, is a leading risk factor for metabolic diseases. Differentially methylated regions (DMRs) of two imprinted genes, insulin-like growth factor 2 (IGF2) and H19, have been associated with obesity due to their important roles in regulating body composition, but have not been examined in relation to intra-abdominal fat depots. Total body fat from whole-body dual energy X-ray absorptiometry and visceral and liver fat contents from abdominal magnetic resonance imaging in 48 healthy women aged 60-65 years (of White or Japanese ancestry) were each regressed on circulating leukocyte DNA methylation levels of IGF2 (at DMR0, DMR2a, and DMR2b) and H19 (at CTCF3) as assessed by pyrosequencing, while adjusting for age and race/ethnicity. Total fat mass was inversely associated with methylation levels of IGF2 DMR2b (P = 0.016). Total fat-adjusted visceral fat area (P = 0.062) and percent visceral fat measured at L4-L5 (P = 0.045) were associated with higher methylation levels of IGF2 DMR2b. Both total fat-adjusted percent liver fat (P = 0.039) and the presence of fatty liver (P = 0.015) were positively associated with IGF2 DMR2a methylation. Methylation levels of H19 CTCF3 were not associated with overall or intra/abdominal adiposity. The findings indicate that methylation levels of IGF2 DMR regions in leukocytes are associated with total body fat and with fat distribution in the viscera and liver independently of total adiposity.

Temporal Variability and Stability of the Fecal Microbiome: The Multiethnic Cohort Study

BACKGROUND

Measurement reliability and biological stability need to be considered when developing sampling protocols for population-based fecal microbiome studies.

METHODS

Stool samples were collected biannually over a 2-year period and sequenced for the V1-V3 region of the 16S rRNA gene in 50 participants from the Multiethnic Cohort Study. We evaluated the temporal stability of the fecal microbiome on a community level with permutational multivariate analysis of variance (PERMANOVA), as well as on taxa and diversity measures with intraclass correlation coefficients.

RESULTS

Interindividual differences were the predominant source of fecal microbiome variation, and variation within individual was driven more by changing abundances than by the complete loss or introduction of taxa. Phyla and diversity measures were reliable over the 2 years. Most genera were stable over time, although those with low abundances tended to be more dynamic. Reliability was lower among participants who used antibiotics, with the greatest difference seen in samples taken within 1 month of reported use.

CONCLUSIONS

The fecal microbiome as a whole is stable over a 2-year period, although certain taxa may exhibit more temporal variability.

IMPACT

When designing large epidemiologic studies, a single sample is sufficient to capture the majority of the variation in the fecal microbiome from 16S rRNA gene sequencing, while multiple samples may be needed for rare or less-abundant taxa.

Abstract 3268: Associations of plasma trimethylamine N-oxide (TMAO), choline, and betaine with the gut microbiome and biomarkers of inflammation and cardiometabolic risk in the Multiethnic Cohort

Background: TMAO is produced by gut microbial metabolism of dietary quaternary amines and has been linked to several chronic diseases, including colorectal cancer and cardiovascular disease. However, the microbes and mechanisms involved are still unclear. Here, we aimed to 1) identify microbial taxa associated with TMAO and 2) evaluate associations of plasma TMAO, along with its precursors choline and betaine, with inflammatory and cardiometabolic biomarkers.

Methods: We conducted a cross-sectional analysis in 1,716 participants (men and women, 60-77, and of 5 racial/ethnic groups) of the Adiposity Phenotype Study within the Multiethnic Cohort in Hawaii and California. Plasma TMAO, choline, and betaine were measured by LC-MS/MS. The gut microbiome was analyzed by Illumina MiSeq paired-end sequencing of the 16S rRNA gene V1-V3 region using DNA extracted from stool. Fasting blood was analyzed for lipopolysaccharide-binding protein (LBP) and insulin by ELISA; C-reactive protein (CRP), cholesterol, glucose, and triglycerides using a Cobas autoanalyzer; and HOMA-IR for insulin resistance by derivation. Associations between microbial genera and TMAO were assessed with negative binomial and zero-inflated negative binomial (ZINB) regression models, with control of the false discovery rate (FDR) using the Benjamini-Hochberg procedure. Associations of TMAO, choline, and betaine with biomarkers were determined using multivariable linear regression and a ZINB model for CRP, adjusted for age, sex, race/ethnicity, physical activity, aspirin use, and % body fat.

Results: Of 105 genera examined, 7 were associated with TMAO at an FDR of 0.01: Streptoccoccus, Blautia, Clostridium, a genus from the Ruminococcaceae family, Butyricimonas, Lactobacillus, and an uncultured Verrucomicrobia of the order vadinHA64; all showed a positive relationship. Plasma choline (β±SE: 0.23±0.10; p=0.03) and betaine (0.19±0.08; p=0.02), but not TMAO, were positively associated with CRP, whereas only choline was associated with LBP (1.97±0.80; p=0.01). Choline was inversely associated with HDL cholesterol (-14.86±2.29; p&lt;0.001) and positively associated with LDL cholesterol (9.86±5.01; p=0.049). Betaine (-0.16±0.03; p&lt;0.001) and choline (0.14±0.05; p=0.002) were associated with triglycerides, while TMAO was not (0.01±0.02; p=0.46). All 3 plasma compounds were associated with HOMA-IR, with only betaine having an inverse association (-0.32±0.06; p=0.004).

Conclusion: We found several genera of gut microbes associated with plasma TMAO, including Clostridium, several species of which can metabolize choline to trimethylamine. We also identified associations between plasma TMAO, choline, and betaine with inflammatory and cardiometabolic markers, particularly choline, which indicated risk to adverse health outcomes.

Citation Format: Benjamin C. Fu, Meredith AJ Hullar, Timothy W. Randolph, Adrian A. Franke, Kristine R. Monroe, Iona Cheng, Lynne R. Wilkens, John Shepherd, Loïc Le Marchand, Unhee Lim, Johanna W. Lampe. Associations of plasma trimethylamine N-oxide (TMAO), choline, and betaine with the gut microbiome and biomarkers of inflammation and cardiometabolic risk in the Multiethnic Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3268.

Trans-ethnic analysis of metabochip data identifies two new loci associated with BMI

OBJECTIVE

Body mass index (BMI) is commonly used to assess obesity, which is associated with numerous diseases and negative health outcomes. BMI has been shown to be a heritable, polygenic trait, with close to 100 loci previously identified and replicated in multiple populations. We aim to replicate known BMI loci and identify novel associations in a trans-ethnic study population.

SUBJECTS

Using eligible participants from the Population Architecture using Genomics and Epidemiology consortium, we conducted a trans-ethnic meta-analysis of 102 514 African Americans, Hispanics, Asian/Native Hawaiian, Native Americans and European Americans. Participants were genotyped on over 200 000 SNPs on the Illumina Metabochip custom array, or imputed into the 1000 Genomes Project (Phase I). Linear regression of the natural log of BMI, adjusting for age, sex, study site (if applicable), and ancestry principal components, was conducted for each race/ethnicity within each study cohort. Race/ethnicity-specific, and combined meta-analyses used fixed-effects models.

RESULTS

We replicated 15 of 21 BMI loci included on the Metabochip, and identified two novel BMI loci at 1q41 (rs2820436) and 2q31.1 (rs10930502) at the Metabochip-wide significance threshold (P<2.5 × 10-7). Bioinformatic functional investigation of SNPs at these loci suggests a possible impact on pathways that regulate metabolism and adipose tissue.

CONCLUSION

Conducting studies in genetically diverse populations continues to be a valuable strategy for replicating known loci and uncovering novel BMI associations.

Transethnic insight into the genetics of glycaemic traits: fine-mapping results from the Population Architecture using Genomics and Epidemiology (PAGE) consortium

AIMS/HYPOTHESIS

Elevated levels of fasting glucose and fasting insulin in non-diabetic individuals are markers of dysregulation of glucose metabolism and are strong risk factors for type 2 diabetes. Genome-wide association studies have discovered over 50 SNPs associated with these traits. Most of these loci were discovered in European populations and have not been tested in a well-powered multi-ethnic study. We hypothesised that a large, ancestrally diverse, fine-mapping genetic study of glycaemic traits would identify novel and population-specific associations that were previously undetectable by European-centric studies.

METHODS

A multiethnic study of up to 26,760 unrelated individuals without diabetes, of predominantly Hispanic/Latino and African ancestries, were genotyped using the Metabochip. Transethnic meta-analysis of racial/ethnic-specific linear regression analyses were performed for fasting glucose and fasting insulin. We attempted to replicate 39 fasting glucose and 17 fasting insulin loci. Genetic fine-mapping was performed through sequential conditional analyses in 15 regions that included both the initially reported SNP association(s) and denser coverage of SNP markers. In addition, Metabochip-wide analyses were performed to discover novel fasting glucose and fasting insulin loci. The most significant SNP associations were further examined using bioinformatic functional annotation.

RESULTS

Previously reported SNP associations were significantly replicated (p ≤ 0.05) in 31/39 fasting glucose loci and 14/17 fasting insulin loci. Eleven glycaemic trait loci were refined to a smaller list of potentially causal variants through transethnic meta-analysis. Stepwise conditional analysis identified two loci with independent secondary signals (G6PC2-rs477224 and GCK-rs2908290), which had not previously been reported. Population-specific conditional analyses identified an independent signal in G6PC2 tagged by the rare variant rs77719485 in African ancestry. Further Metabochip-wide analysis uncovered one novel fasting insulin locus at SLC17A2-rs75862513.

CONCLUSIONS/INTERPRETATION

These findings suggest that while glycaemic trait loci often have generalisable effects across the studied populations, transethnic genetic studies help to prioritise likely functional SNPs, identify novel associations that may be population-specific and in turn have the potential to influence screening efforts or therapeutic discoveries.

DATA AVAILABILITY

The summary statistics from each of the ancestry-specific and transethnic (combined ancestry) results can be found under the PAGE study on dbGaP here: https://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?study_id=phs000356.v1.p1.

Correction to: Transethnic insight into the genetics of glycaemic traits: fine-mapping results from the Population Architecture using Genomics and Epidemiology (PAGE) consortium

The authors regret that Yinchang Lu's name incorrectly included a middle initial in the author list. The details given in this erratum are correct.

Plasma lipopolysaccharide-binding protein and colorectal cancer risk: a nested case-control study in the Multiethnic Cohort

BACKGROUND

Lipopolysaccharide (LPS), an endotoxin found on the outer cell wall of Gram-negative bacteria, increases inflammatory response signaling and may play a role in the pathogenesis of several adverse outcomes, including inflammatory bowel diseases, cardiovascular disease, and cancer. While LPS is hypothesized to be associated with colorectal carcinogenesis, there are relatively few human studies which have examined this association.

METHODS

We examined the association between colorectal cancer (CRC) and plasma lipopolysaccharide-binding protein (LBP), a marker of LPS, in 1,638 participants (819 CRC cases and 819 controls) matched on multiple factors, including age, sex, and race/ethnicity, from the Multiethnic Cohort study. Conditional logistic regression models were used to estimate the multivariable-adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Compared to individuals whose LBP concentrations were in the lowest quartile, the ORs associated with second, third, and fourth quartiles were 1.23 (95% CI 0.91-1.67), 1.36 (95% CI 1.01-1.83), and 1.01 (95% CI 0.73-1.39), respectively, (p _trend = 0.66). No differences were observed by BMI, fiber intake, saturated fat intake, cancer site, or cancer stage.

CONCLUSIONS

This study did not find an overall statistically significant association between LBP (as a marker of LPS exposure) and CRC. Further prospective studies with multiple LBP measurements are needed to validate current findings.

Diet Quality in Midadulthood Predicts Visceral Adiposity and Liver Fatness in Older Ages: The Multiethnic Cohort Study

OBJECTIVE

The relationship of diet quality assessed by established indices (HEI-2010, AHEI-2010, aMED, DASH) with adiposity measures was examined, especially visceral adipose tissue (VAT) and nonalcoholic fatty liver (NAFL).

METHODS

Close to 2,000 participants of the Multiethnic Cohort completed validated food frequency questionnaires at cohort entry (1993-1996) and clinic visit (2013-2016) when they underwent whole-body dual-energy x-ray absorptiometry and abdominal magnetic resonance imaging scans. Linear regression was used to estimate mean values of adiposity measures by dietary index tertiles at baseline and standardized regression coefficients (β_s ) after adjusting for total adiposity and other covariates. Logistic regression of VAT and NAFL on dietary indices was also performed.

RESULTS

Higher dietary quality scores at cohort entry were inversely related to all adiposity measures, with the strongest associations for percent liver fat (β_s  = -0.14 to -0.08), followed by VAT (β_s  = -0.11 to -0.05), BMI (β_s  = -0.11 to -0.06), and total body fat (β_s  = -0.09 to -0.05). Odds ratios adjusted for total adiposity ranged between 0.57 and 0.77 for NAFL and between 0.41 and 0.65 for high VAT when comparing the highest versus lowest tertiles of diet quality.

CONCLUSIONS

These longitudinal findings indicate that maintaining a high-quality diet during mid-to-late adulthood may prevent adverse metabolic consequences related to VAT and NAFL.