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1.  Comparison of Postprandial Responses to a High-Fat Meal in Hypertriglyceridemic Men and Women before and after Treatment with Fenofibrate in the Genetics and Lipid Lowering Drugs and Diet Network (GOLDN) Study 
SRX pharmacology  2010;2010:485146-.
The fenofibrate effect on the subclass size distribution of lipoproteins before and after a high-fat challenge is not well studied.
To characterize the baseline and post-prandial response (PPL) to a high-fat challenge following fenofibrate therapy, on changes in LDL, HDL, and VLDL particle subclasses, number, and size in 271 hypertriglyceridemic participants.
Participants from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study who conducted PPL studies both before and after three weeks of fenofibrate (160 mg/d) treatment were analyzed. Particle size distributions were determined using nuclear magnetic resonance imaging, and lipid determinations were measured at fasting (0 hr), 3.5 hours, and 6 hours after ingestion of a standardized high-fat meal. Analyses were stratified by gender. Changes in particle subclass distributions were assessed using repeated measures analysis of variance adjusted for pedigree.
Before PPL, fenofibrate in men (adjusted for age, field center, smoking status, diabetes, and weight circumference) lowered fasting and postprandial VLDL primarily due to reductions in postprandial levels of large and medium VLDL particles (9 SE +/–0.7 to 4 +/–0.4 and 78 / –4 to 36 / –3 nmol/L both P < .0001, resp.). Fenofibrate also reduced fasting and postprandial total LDL particles, primarily a result of reduced small LDL particles (1497 = / – 37 to 1088 = / – 36 nmol/L, P < .0001). Directional changes were similar in men and women but the magnitude of change was different for some parameters.
Fenofibrate treatment resulted in a lower triglyceride excursion following a high-fat meal. This investigation provides new knowledge of the magnitude and time course of fenofibrate induced attenuation of Lipoprotein subclass size distribution following a postprandial lipid challenge.
PMCID: PMC4067904  PMID: 24971173
2.  n-3 and n-6 Fatty acids are independently associated with lipoprotein-associated phospholipase A2 in the Multi-Ethnic Study of Atherosclerosis 
The British journal of nutrition  2013;110(9):1664-1671.
Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an independent risk factor for CVD and has been proposed as a marker of vascular inflammation. Polyunsaturated n-3 fatty acids (FA) and several n-6 FA are known to suppress inflammation and may influence Lp-PLA2 mass and activity. The associations of n-3 and n-6 plasma FA with Lp-PLA2 mass and activity were analysed using linear regression analysis in 2246 participants of the Multi-Ethnic Study of Atherosclerosis; statistical adjustments were made to control for body mass, inflammation, lipids, diabetes, and additional clinical and demographic factors. Lp-PLA2 mass and activity were significantly lower in participants with the higher n-3 FA EPA (β = −4·72, P<0·001; β = −1·53; P=0·023) and DHA levels (β = −4·47, β = −1·87; both P<0·001). Those in the highest quintiles of plasma EPA and DHA showed 12·71 and 19·15 ng/ml lower Lp-PLA2 mass and 5·7 and 8·90 nmol/min per ml lower Lp-PLA2 activity than those in the first quintiles, respectively. In addition, lower Lp-PLA2 mass and activity were associated with higher levels of n-6 arachidonic acid (β = −1·63, β = −1·30; both P<0·001), while γ-linolenic acid was negatively associated with activity (β = −27·7, P=0·027). Lp-PLA2 mass was significantly higher in participants with greater plasma levels of n-6 linoleic (β = 0·828, P=0·011) and dihomo-γ-linolenic acids (β = 4·17, P=0·002). Based on their independent associations with Lp-PLA2 mass and activity, certain n-3 and n-6 FA may have additional influences on CVD risk. Intervention studies are warranted to assess whether these macronutrients may directly influence Lp-PLA2 expression or activity.
PMCID: PMC4060439  PMID: 23551952
Fatty acids; n-3; Atherosclerosis; Lipoprotein-associated phospholipase; Lipoprotein-associated phospholipase A2
3.  APOE genotype modifies the association between plasma measured omega-3 fatty acids and plasma lipids in the Multi-Ethnic Study of Atherosclerosis (MESA) 
Atherosclerosis  2013;228(1):181-187.
The benefits of fish oil fatty acids eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) on plasma lipid profiles have been inconsistent but may partially depend on individual Apolipoprotein E (APOE) genotypes. We aimed to determine whether APOE genotype modifies the association of lipid profile characteristics with plasma EPA and DHA levels.
APOE genotype was determined in this cross-sectional analysis of 2340 Multi-Ethnic Study of Atherosclerosis (MESA) participants. Relative plasma phospholipid EPA and DHA levels, plasma lipids, and lipoprotein subclass particle sizes and concentrations were measured.
Significant gene-EPA interactions were found with HDL-C, and particle concentrations of large and total HDL (pinteraction = 0.0002, 0.006, and 0.007, respectively). The above lipid targets were positively associated with EPA in the E2 groups, whereas negative trends were observed among the E4 participants. Gene-DHA interactions were noted for small LDL particle concentrations alone (pinteraction = 0.01), where a positive trend was found among E4 but not E2 or E3 participants.
These results indicate a significant contribution of the APOE genotype to the EPA-lipid profile relationship; however, the results do not explain the differences in previous findings regarding LDL-C, triglycerides or total cholesterol. Future investigators examining the effects of EPA on HDL-C or lipoprotein characteristics may consider including APOE genotype in their analyses.
PMCID: PMC3640761  PMID: 23466070
APOE genotype; eicosapentaenoic acid (EPA); docosahexaenoic acid (DHA); plasma lipids; lipoproteins
4.  Genetic variants associated with VLDL, LDL and HDL particle size differ with race/ethnicity 
Human genetics  2012;132(4):405-413.
Specific constellations of lipoprotein particle features, reflected as differences in mean lipoprotein particle diameters, are associated with risk of insulin resistance (IR) and cardiovascular disease (CVD). The associations of lipid profiles with disease risk differ by race/ethnicity, the reason for this is not clear. We aimed to examine whether there were additional genetic differences between racial / ethnic groups on lipoprotein profile.
Methods and results
Genotypes were assessed using the Affymetrix 6.0 array in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN). Association analysis was conducted on fasting mean particle diameters using linear models, adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. Replication of associations reaching P<1.97 * 10−05 (the level at which we achieved at least 80% power to replicate SNP-phenotype associations) was conducted in the Caucasian population of the Multi-Ethnic Study of Atherosclerosis (MESA; N=2430). Variants which replicated across both Caucasian populations were subsequently tested for association in the African-American (N=1594), Chinese (N=758) and Hispanic (N=1422) populations of MESA. Variants in the APOB gene region were significantly associated with mean VLDL diameter in GOLDN, and in the Caucasian and Hispanic populations of MESA, while variation in the hepatic lipase (LIPC) gene was associated with mean HDL diameter in both Caucasians populations only.
Our findings suggest the genetic underpinnings of mean lipoprotein diameter differ by race/ethnicity. As lipoprotein diameters are modifiable, this may lead new strategies to modify lipoprotein profiles during the reduction of IR that are sensitive to race / ethnicity.
PMCID: PMC3600091  PMID: 23263444
Lipoprotein size; race / ethnicity; ApoB; Hepatic Lipase; NMR
5.  Genetic Analysis of 16 NMR-Lipoprotein Fractions in Humans, the GOLDN Study 
Lipids  2012;48(2):155-165.
Sixteen nuclear magnetic resonance (NMR) spectroscopy lipoprotein measurements of more than 1,000 subjects of GOLDN study, at fasting and at 3.5 and 6 h after a postprandial fat (PPL) challenge at visits 2 and 4, before and after a 3 weeks Fenofibrate (FF) treatment, were included in 6 time-independent multivariate factor analyses. Their top 1,541 unique SNPs were assessed for association with GOLDN NMR-particles and classical lipids. Several SNPs with −log10 p > 7.3 and MAF ≥ 0.10, mostly intergenic associated with NMR-single traits near genes FAM84B (8q24.21), CRIPT (2p21), ACOXL (2q13), BCL2L11 (2q13), PCDH10 (4q28.3), NXPH1 (7p22), and SLC24A4 (14q32.12) in association with NMR-LDLs; HOMER1 (5q14.2), KIT (4q11–q12), VSNL1 (2p24.3), QPRT (16p11.2), SYNPR (3p14.2), NXPH1 (7p22), NELL1 (11p15.1), and RUNX3 (1p36) with NMR-HDLs; and DOK5-CBLN4-MC3R (20q13), NELL1 (11p15.1), STXBP6 (14q12), APOB (2p24-p23), GPR133 (12q24.33), FAM84B (8q24.21) and NR5A2 (1q32.1) in association with NMR-VLDLs particles. NMR single traits associations produced 75 % of 114 significant candidates, 7 % belonged to classical lipids and 18 % overlapped, and 16 % matched for time of discovery between NMR- and classical traits. Five proxy genes, (ACOXL, FAM84B, NXPH1, STK40 and VAPA) showed pleiotropic effects. While tagged for significant associations in our study and with some extra evidence from the literature, candidates as CBNL4, FAM84B, NXPH1, SLC24A4 remain unclear for their functional relation to lipid metabolism. Although GOLDN study is one of the largest in studying PPL and FF treatment effects, the relatively small samples (over 700–1,000 subjects) in association tests appeals for a replication of such a study. Thus, further investigation is needed.
PMCID: PMC3601742  PMID: 23192668
Nuclear magnetic resonance particles; Lipoproteins; Fenofibrate; Postprandial challenge; Genome-wide association
6.  Circulating and Dietary Omega‐3 and Omega‐6 Polyunsaturated Fatty Acids and Incidence of CVD in the Multi‐Ethnic Study of Atherosclerosis 
Dietary guidelines support intake of polyunsaturated fatty acids (PUFAs) in fish and vegetable oils. However, some controversy remains about benefits of PUFAs, and most prior studies have relied on self‐reported dietary assessment in relatively homogeneous populations.
Methods and Results
In a multiethnic cohort of 2837 US adults (whites, Hispanics, African Americans, Chinese Americans), plasma phospholipid PUFAs were measured at baseline (2000–2002) using gas chromatography and dietary PUFAs estimated using a food frequency questionnaire. Incident cardiovascular disease (CVD) events (including coronary heart disease and stroke; n=189) were prospectively identified through 2010 during 19 778 person‐years of follow‐up. In multivariable‐adjusted Cox models, circulating n‐3 eicosapentaenoic acid and docosahexaenoic acid were inversely associated with incident CVD, with extreme‐quartile hazard ratios (95% CIs) of 0.49 for eicosapentaenoic acid (0.30 to 0.79; Ptrend=0.01) and 0.39 for docosahexaenoic acid (0.22 to 0.67; Ptrend<0.001). n‐3 Docosapentaenoic acid (DPA) was inversely associated with CVD in whites and Chinese, but not in other race/ethnicities (P‐interaction=0.01). No significant associations with CVD were observed for circulating n‐3 alpha‐linolenic acid or n‐6 PUFA (linoleic acid, arachidonic acid). Associations with CVD of self‐reported dietary PUFA were consistent with those of the PUFA biomarkers. All associations were similar across racial‐ethnic groups, except those of docosapentaenoic acid.
Both dietary and circulating eicosapentaenoic acid and docosahexaenoic acid, but not alpha‐linolenic acid or n‐6 PUFA, were inversely associated with CVD incidence. These findings suggest that increased consumption of n‐3 PUFA from seafood may prevent CVD development in a multiethnic population.
PMCID: PMC3886748  PMID: 24351702
cardiovascular disease prevention; cardiovascular risk factors; diet; fatty acids
7.  The SCARB1 gene is associated with lipid response to dietary and pharmacological interventions 
Journal of human genetics  2008;53(8):10.1007/s10038-008-0302-2.
The scavenger receptor class B type 1 (SCARB1) gene is a key component in the reverse cholesterol transport pathway and thus plays an important role in lipid metabolism. Studies suggested that the SCARB1 gene may contribute to variation in plasma lipid levels at the fasting; however, the results have been inconsistent and it is unclear if SCARB1 may also influence lipid response to dietary and pharmacologic interventions. In this study, we examined genetic variation in the SCARB1 gene in participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study for associations with basal lipid levels, changes in lipid measures after dietary fat intake and fenofibrate treatment. We found that the exon 1 variant SCARB1_G2S was significantly associated with post-fenofibrate change for triglyceride (TG) (P = 0.004). Subjects bearing SCARB1_G2S minor allele A tend to have higher responsiveness to fenofibrate in lowering TG. In summary, our study suggested that the SCARB1 gene may serve as a useful marker that predicts variation in baseline lipid levels, postprandial lipid response as well as response to fenofibrate intervention.
PMCID: PMC3836273  PMID: 18542840
Scavenger receptor class B type 1; lipid; genetics; fenofibrate; postprandial
8.  Plasma Phospholipid Concentration of Cis Palmitoleic Acid and Risk of Heart Failure 
Circulation. Heart failure  2012;5(6):703-709.
While plasma palmitoleic acid has been positively associated with blood pressure, inflammation, and insulin resistance, its association with heart failure has not been investigated. We assessed whether plasma phospholipid cis palmitoleic acid was associated with heart failure risk.
Methods and Results
This ancillary study of the Physicians’ Health Study used a risk set sampling method to select 788 matched pairs. For each case of incident heart failure, we randomly selected a control among subjects that were free of heart failure and alive at the time of index case diagnosis and matched on age, year of birth, race, and time of blood collection. Plasma phospholipid fatty acids were measured using gas chromatography. Heart failure was ascertained using annual follow-up questionnaire and validated in a subsample. In a multivariable conditional logistic regression, odds ratios (95% CI) for heart failure were 1.0 (ref), 1.06 (0.75-1.48), 1.20 (0.85-1.68), and 1.58 (1.11-2.25) across consecutive quartiles of cis palmitoleic acid (p for trend 0.009). Each standard deviation increase in plasma cis palmitoleic acid was associated with 17% higher odds of heart failure (95% CI: 2% to 33%) in a multivariable model. In a secondary analysis, each standard deviation increase of log-stearoyl-coA desaturase activity (16:1n-7/16:0 ratio) was positively associated with the risk of heart failure [OR: 1.14 (95% CI: 1.00-1.29)] whereas oleic acid and cis-vaccenic acid concentrations were not related to heart failure risk.
Our data showed a positive association between plasma phospholipid cis-palmitoleic acid and heart failure risk in male physicians.
PMCID: PMC3618485  PMID: 23065037
heart failure; epidemiology; fatty acids; cis-palmitoleic acids; risk factors
9.  Association between adiponectin and heart failure risk in the Physicians' Health Study 
Obesity (Silver Spring, Md.)  2013;21(4):831-834.
Limited data are available on the association between adiponectin and incident heart failure. In the current ancillary study to the Physicians' Health Study, we used a prospective nested-case control design to examine whether plasma adiponectin concentration was related to the risk of heart failure. We selected 787 incident heart failure cases and 787 matched controls for the current analysis. Each control was selected using a risk set sampling technique at the time of the occurrence of the index case and matched on year of birth, age at blood collection, and race. Adiponectin was measured using ELISA. Heart failure occurrence was self-reported in annual follow-up questionnaire. Validation of self-reported heart failure in this cohort has been published. The mean age was 58.7 years. In a conditional logistic regression adjusting for age, race, time of blood collection, year of birth, hypertension, atrial fibrillation, smoking, alcohol intake, and exercise, estimates of the relative risk (95% confidence interval) were 1.0 (ref), 0.74 (0.53–1.04), 0.67 (0.48–0.94), 0.70 (0.50–0.99), and 0.92 (0.65–1.30) from the lowest to the highest quintile of adiponectin, respectively, p for quadratic trend 0.004. Additional adjustment for potential mediating factors including diabetes, C-reactive protein, and body mass index led to the attenuation of the estimate of effect [1.0 (ref), 0.81 (0.57–1.15), 0.75 (0.53–1.06), 0.83 (0.58–1.18), and 1.26 (0.87–1.81) across consecutive quintiles of adiponectin]. Our data are consistent with a J-shaped association between total adiponectin and the risk of heart failure among US male physicians.
PMCID: PMC3479315  PMID: 23712986
Adiponectin; epidemiology; heart failure; risk factors
10.  Association of Biomarkers for Inflammation, Endothelial Dysfunction and Oxidative Stress with Cognitive Impairment. The Epidemiology of Hearing Loss Study (EHLS) 
Individual biomarkers of inflammation, endothelial dysfunction and oxidative stress have been associated with cognitive impairment. This study explored whether a combination of biomarkers could prospectively identify those who developed cognitive decline.
Biomarkers were obtained during the baseline examination of the Beaver Dam Eye Study (1988–90), and cognitive status was assessed during the 5-year follow-up examination of the Epidemiology of Hearing Loss Study (1998–2000). Cognitive impairment was defined as a score of < 24 points on the Mini-Mental State Examination or self- or proxy report of Alzheimer Disease or dementia. Among those with cognitive data, interleukin-6, isoprostanes, protein carbonyl, soluble inter-cellular adhesion molecule-1 and vascular cell adhesion molecule-1 were available for 950 participants and 2,336 had high sensitivity C-reactive protein.
Biomarkers of inflammation and endothelial dysfunction were not associated with cognitive impairment. There was a weak inverse association between higher levels of protein carbonyl content and cognitive impairment (OR, 0.8 per quartile of protein carbonyl content, p=0.045 unadjusted for multiple comparisons). This was not significant on multiple testing and may have been a chance finding.
We found that many markers of inflammation and endothelial dysfunction were not associated with cognitive impairment. An inverse association with carbonyl protein, a marker of oxidative stress needs further confirmation.
PMCID: PMC3693393  PMID: 23814681
oxidative stress; inflammation; biomarkers; cognitive impairment
11.  Cholesteryl Ester Transfer Protein Genetic Polymorphisms, HDL Cholesterol, and Subclinical Cardiovascular Disease in the Multi-Ethnic Study of Atherosclerosis 
Atherosclerosis  2008;200(2):359-367.
The cholesteryl ester transport protein (CETP) plays a key role in high-density lipoprotein (HDL) metabolism. Genetic variants that alter CETP activity and concentration may cause significant alterations in HDL-cholesterol (HDL-C) concentration; however, controversies remain about whether these genetic variants are associated with atherosclerosis. We genotyped the CETP R451Q, A373P, -629C/A, Taq1B, and -2505C/A polymorphisms in a cohort of Caucasian, Chinese, African-American, and Hispanic individuals within the Multi-Ethnic Study of Atherosclerosis. Genotypes were examined in relationship to HDL-C, CETP activity, CETP concentration, and three measures of subclinical cardiovascular disease (CVD): coronary artery calcium (CAC) measured by fast CT scanning, and carotid intimal-medial thickness (IMT) and carotid artery plaque, measured by ultrasonography. Carriers of the 451Q and 373P alleles have significantly higher CETP concentration (22.4% and 19.5%, respectively; p<0.001) and activity (13.1% and 9.4%, respectively; p<0.01) and lower HDL-C (5.6% and 6.0%, respectively; p<0.05). The minor alleles of the R451Q and A373P polymorphisms are associated with the presence of CAC, even after adjusting for CVD risk factors and HDL-C (p=0.006 and p=0.01, respectively). The R451Q polymorphism is also associated with presence of carotid artery plaque (p=0.036). Neither polymorphism is associated with common or internal carotid IMT. We confirmed that the -629A, Taq1B B2, and -2505A alleles are significantly associated with lower CETP concentration (20.8%, 25.0%, and 23.7%, respectively; p<0.001) and activity (14.8%, 19.8%, and 18.4%, respectively; p<0.001) and higher HDL-C concentration (9.7%, 11.5%, and 10.4%, respectively; p<0.01). However, we did not find any associations between these non-coding polymorphisms and subclinical CVD.
PMCID: PMC3612981  PMID: 18243217
12.  Effect of Fenofibrate Therapy and ABCA1 Polymorphisms on High Density Lipoprotein Subclasses in the Genetics of Lipid Lowering Drugs and Diet Network 
Molecular genetics and metabolism  2010;100(2):118-122.
Previous studies have shown that ATP-binding cassette transporter 1 (ABCA1) polymorphisms associated with increased ABCA1 expression result in increased small HDL (high density lipoprotein) subclass particle concentration. The present study examines the effect of treatment with fenofibrate, a drug known to bind peroxisome proliferator-activated receptor alpha (PPARα) which increases the expression of ABCA1 gene, on lipoprotein subclass profiles of individuals stratified by ABCA1 genotypes.
Participants of Genetics of Lipid-lowering Drugs and Diet Network (GOLDN) were treated with fenofibrate over a three week period. We analyzed six ABCA1 polymorphisms in 287 GOLDN participants with triglyceride concentrations ≥ 150 mg/dL and studied their associations with HDL subclass particle concentrations, as measured by nuclear magnetic resonance spectroscopy, before and after treatment.
Fenofibrate treatment did not result in significant changes in small HDL subclass particle concentration. When changes in HDL subclasses were stratified by ABCA1 polymorphism genotypes, there were no statistically significant associations between ABCA1 genotypes and small HDL subclasses before fenofibrate treatment. However, after fenofibrate treatment the KK genotype of R1587K (mean 4.40 μmol/L; p = 0.004) and the RK genotype of R219K (mean 1.60 μmol/L; p = 0.02) polymorphisms were associated with significantly increased small HDL. The R1587K KK genotype (mean 4.80 μmol/L; p = 0.0002) and the R219K KK genotype (mean 2.50 μmol/L; p = 0.02) were also associated with increased HDL particle concentrations.
There is a synergistic effect between ABCA1 polymorphisms and fenofibrate. Thus our study indirectly confirms the role of fenofibrate and genotype in increasing cholesterol efflux, as evidenced by increased small HDL particles.
PMCID: PMC3598593  PMID: 20346718
ABCA1; cardiovascular disease; fenofibrate; lipoprotein; lipoprotein particle size
13.  A genome-wide association study of inflammatory biomarker changes in response to fenofibrate treatment in the Genetics of Lipid Lowering Drug and Diet Network (GOLDN) 
Pharmacogenetics and Genomics  2012;22(3):191-197.
Despite evidence in support of anti-inflammatory and triglyceride-lowering effects of fenofibrate, little is known about genetic determinants of the observed heterogeneity in treatment response. This study provides the first genome-wide examination of fenofibrate effects on systemic inflammation.
Biomarkers of inflammation were measured in participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN, n=1092) before and after a 3-week daily treatment with 160 mg of fenofibrate. Two inflammatory patterns (hsCRP-IL6 and MCP1-TNF-α) were derived using principal component analysis. Associations between single nucleotide polymorphisms on the Affymetrix 6.0 chip and phenotypes were assessed using mixed linear models, adjusted for age, sex, study center, and ancestry as fixed effects and pedigree as a random effect.
Before fenofibrate treatment, the strongest evidence for association was observed for polymorphisms near or within the IL2RA gene with the hsCRP-IL6 pattern (rs7911500, P=5×10−9 and rs12722605, P=5×10−8). Associations of the MCP1-TNF-α pattern with loci in several biologically plausible genes (CYP4F8 (rs3764563), APBB1IP (rs1775246), COL13A1 (rs2683572), and COMMD10 (rs1396485)) approached genome-wide significance (P=3×10−7, 5×10−7, 6×10−7, and 7×10−7 respectively) before fenofibrate treatment. After fenofibrate treatment, the rs12722605 locus in IL2RA was also associated with the MCP1-TNF-α pattern (P=3×10−7). The analyses of individual biomarker response to fenofibrate did not yield genome-wide significant results, but the rs6517147 locus near the immunologically relevant IFNAR2 gene was suggestively associated with IL6 (P=7×10−7).
We have identified several novel biologically relevant loci associated with systemic inflammation before and after fenofibrate treatment.
PMCID: PMC3275691  PMID: 22228203
fenofibrate; inflammation; genome-wide association study
14.  Polygenic Association with Total Homocysteine in the Post Folic Acid Fortification Era: the CARDIA Study 
Molecular genetics and metabolism  2009;98(1-2):181-186.
Elevated plasma concentration of total homocysteine (tHcy) has been linked with many diseases. tHcy is associated with a variety of factors, including polymorphisms in genes involved in homocysteine metabolism. It is not clear whether US-mandated fortification of grain products with folic acid has affected the association of genetic variants with tHcy levels. We determined tHcy concentrations in sera from 997 Caucasians and 692 African Americans participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study before and after folic acid fortification. DNA was genotyped for variants present in four genes involved in homocysteine metabolism: cystathionine β-synthase (CBS) 844ins68, methionine synthase (MS) 2756A>G; methionine synthase reductase (MTRR) 66A>G, and methylenetetrahydrofolate reductase (MTHFR) 677C>T and 1298A>C. A greater number of African Americans were homozygous for the MS 2756GG, MTRR 66GG and CBS 844ins68 genotypes compared to Caucasians, while prevalence of MTHFR 677TT and 1298CC genotypes was substantially lower in African Americans compared to Caucasians. The overall variance in tHcy levels at y 0, 7, and 15 that can be explained by the combined presence of all five variants increased slightly over time in Caucasians (17%, y 0; 21%, y 7 and 26%, y 15) and in African Americans (13%, y 0; 17% y 7; 18% y 15) largely due to decrease in tHcy variance.
PMCID: PMC3578421  PMID: 19577940
Cystathionine B-synthase; folic acid; homocysteine; methylenetetrahydrofolate reductase; methionine synthase; methionine synthase reductase
15.  Epistatic study reveals two genetic interactions in blood pressure regulation 
BMC Medical Genetics  2013;14:2.
Although numerous candidate gene and genome-wide association studies have been performed on blood pressure, a small number of regulating genetic variants having a limited effect have been identified. This phenomenon can partially be explained by possible gene-gene/epistasis interactions that were little investigated so far.
We performed a pre-planned two-phase investigation: in phase 1, one hundred single nucleotide polymorphisms (SNPs) in 65 candidate genes were genotyped in 1,912 French unrelated adults in order to study their two-locus combined effects on blood pressure (BP) levels. In phase 2, the significant epistatic interactions observed in phase 1 were tested in an independent population gathering 1,755 unrelated European adults.
Among the 9 genetic variants significantly associated with systolic and diastolic BP in phase 1, some may act through altering the corresponding protein levels: SNPs rs5742910 (Padjusted≤0.03) and rs6046 (Padjusted =0.044) in F7 and rs1800469 (Padjusted ≤0.036) in TGFB1; whereas some may be functional through altering the corresponding protein structure: rs1800590 (Padjusted =0.028, SE=0.088) in LPL and rs2228570 (Padjusted ≤9.48×10-4) in VDR. The two epistatic interactions found for systolic and diastolic BP in the discovery phase: VCAM1 (rs1041163) * APOB (rs1367117), and SCGB1A1 (rs3741240) * LPL (rs1800590), were tested in the replication population and we observed significant interactions on DBP. In silico analyses yielded putative functional properties of the SNPs involved in these epistatic interactions trough the alteration of corresponding protein structures.
These findings support the hypothesis that different pathways and then different genes may act synergistically in order to modify BP. This could highlight novel pathophysiologic mechanisms underlying hypertension.
PMCID: PMC3599121  PMID: 23298194
Blood pressure; Epistasis; Single nucleotide polymorphism; Epidemiology
16.  The Relation between Erythrocyte Trans Fat and Triglyceride, VLDL- and HDL-Cholesterol Concentrations Depends on Polyunsaturated Fat 
PLoS ONE  2012;7(10):e47430.
Trans fatty acids (TFA) lower HDL and increase triglyceride concentrations while polyunsaturated fatty acids (PUFA) lower triglycerides and may decrease HDL concentrations. The effect of the interaction between trans fat and PUFA on lipids is uncertain.
Men and women (n = 1032) in the Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN) study were included. Fatty acids in erythrocyte membranes were measured with gas chromatography while data on potential confounders were obtained from questionnaires. To test the interaction between total erythrocyte PUFA (ePUFA) and TFA (eTFA) on lipid concentrations we distributed eTFA into tertiles and dichotomized ePUFA at the median concentration.
For the 1st, 2nd and 3rd tertiles of eTFA, multivariate-adjusted means±s.e.m for HDL were 46.2±1.1, 46.3±1.1 and 45.5±1.0 mg/dL among those with low ePUFA, respectively, while they were 50.0±1.1, 46.9±1.1 and 44.7±1.1 mg/dL among those with high ePUFA, respectively (P for interaction = 0.01). For the 1st, 2nd and 3rd tertiles of eTFA, multivariate-adjusted means±s.e.m for triglycerides were 178.6±11.3, 144.7±10.9 and 140.8±10.6, respectively, among those with low ePUFA, while they were 133.8±11.3, 145.7±10.9 and 149.3±11.5, respectively, among those with high ePUFA (P for interaction = 0.005). Results for VLDL were similar to those for triglycerides. No significant interactions were observed for LDL or total cholesterol.
The relation between trans fat and HDL, VLDL and triglycerides may depend on PUFA. The benefit of avoiding trans fat may be greater among individuals with higher PUFA intake. Supplementation with PUFA among individuals with relatively high trans fat intake may have limited benefits on lipid profiles.
PMCID: PMC3471823  PMID: 23077615
17.  Short-Term Fenofibrate Treatment Reduces Elevated Plasma Lp-PLA2 Mass and sVCAM-1 Levels in a Sub-Cohort of Hypertriglyceridemic GOLDN Participants 
High levels of lipoprotein-associated phospholipase A2 (Lp-PLA2) are associated with inflammation, atherosclerosis, and CHD events. In addition, Lp-PLA2 has been linked to classical markers of endothelial activation, including soluble vascular cell adhesion molecule-1 (sVCAM-1). Though treatment with fenofibrate reduces Lp-PLA2 mass, it is unclear whether fenofibrate reduces sVCAM-1 levels or whether there is an association between any changes observed in Lp-PLA2 and sVCAM-1.
Concentrations of Lp-PLA2 mass and sVCAM-1 levels were measured in plasma at baseline and after 3 weeks of fenofibrate treatment (160 mg/d) in 96 hypertriglyceridemic participants of the Genetics of Lipid-lowering Drugs and Diet Network (GOLDN) study.
Lp-PLA2 and sVCAM-1 were stratified by tertiles as determined by baseline levels of the respective target. Fenofibrate treatment resulted in increases of 30.1% in Lp-PLA2 mass (p=0.0003) and 14.7% in sVCAM-1 levels (p=0.0096), but only in tertile1 of either target. In contrast, Lp-PLA2 mass was reduced by 35.3 % (p<0.0001) in tertile 3. Soluble VCAM-1 levels were significantly reduced by 7.74% (p=0.0109) and 17.2% (p<0.0001) in tertiles 2 and 3, respectively. No associations were observed between Lp-PLA2 and sVCAM-1 at baseline or post-treatment.
In conclusion, fenofibrate treatment in hypertriglyceridemic subjects reduced levels of LpPLA2 mass and sVCAM-1, but only in those with elevated baseline levels of these biomarkers. The greatest reductions in LpPLA2 levels were observed in individuals with LpPLA2 concentrations indicative of increased CVD risk (>200 ng/mL).
PMCID: PMC3138503  PMID: 21757154
Fenofibrate; atherosclerosis; VCAM; Lp-PLA; triglyceride; GOLDN
18.  Analysis of Family- and Population-Based Samples in Cohort Genome-Wide Association Studies 
Human Genetics  2011;131(2):275-287.
Cohort studies typically sample unrelated individuals from a population, although family members of index cases may be also be recruited to investigate shared familial risk factors. Recruitment of family members may be incomplete or ancillary to the main cohort, resulting in a mixed sample of independent family units, including unrelated singletons and multiplex families. Multiple methods are available to perform genome wide association (GWA) analysis of binary or continuous traits in families, but it is unclear whether methods known to perform well on ascertained pedigrees, sib-ships, or trios are appropriate in analysis of a mixed unrelated cohort and family sample.
We present simulation studies based on Multi-Ethnic Study of Atherosclerosis (MESA) pedigree structures to compare the performance of several popular methods of GWA analysis for both quantitative and dichotomous traits in cohort studies. We evaluate approaches suitable for analysis of families, and combined the best performing methods with population-based samples either by meta-analysis, or by pooled analysis of family- and population-based samples (mega-analysis), comparing type 1 error and power. We further assess practical considerations, such as availability of software and ability to incorporate covariates in statistical modeling, and demonstrate our recommended approaches through quantitative and binary trait analysis of HDL cholesterol (HDL-C) in 2,553 MESA family- and population-based African-American samples. Our results suggest linear modeling approaches that accommodate family-induced phenotypic correlation (e.g., variance component model for quantitative traits or generalized estimating equations for dichotomous traits) perform best in the context of combined family- and population-based cohort GWAS.
PMCID: PMC3369696  PMID: 21805149
genome-wide association study (GWAS); cohort study; simulation study; generalized estimating equations (GEE); variance component model; family-based association
19.  Bidirectional Association of Retinal Vessel Diameters and Estimated Glomerular Filtration Rate Decline: The Beaver Dam CKD Study 
Recent cross-sectional studies have reported an association between retinal vessel caliber and chronic kidney disease (CKD), but the direction of the association between these two processes is not clear. In a prospective study with multiple measurements of retinal vessel diameters and serum creatinine, we examined if baseline retinal vessel diameters are associated with future risk of CKD, or vice versa.
Study design
Population-based cohort study
Setting and participants
3,199 Wisconsin adults aged 43-84 years who were followed prospectively for 15 years.
Baseline retinal arteriolar and venular diameters for analysis 1, and baseline estimated glomerular filtration rate (eGFR) categories for analysis 2.
Outcomes and measurements
For analysis 1, incident CKD defined as eGFR <60 mL/min/1.73m2 accompanied by a 25% decrease in eGFR during follow up. For analysis 2, incident retinal arteriolar narrowing defined as a central retinal arteriolar equivalent measurement of <144.0μm and incident retinal venular dilation defined as a central retinal venular equivalent measurement of >243.8μm.
Baseline retinal arteriolar and venular diameters were not found to be associated with the 15-year risk of incident CKD. After adjustment for age, sex, diabetes, hypertension and other confounders, the multivariable hazard ratio (HR) (95% confidence interval (CI) of incident CKD comparing the narrowest with the widest quartile was 1.15 (0.74-1.80) for retinal arteriolar and 1.05 (0.67-1.67) for retinal venular diameter. Similarly, there was no significant association between eGFR and 15-year risk of incident retinal arteriolar narrowing or retinal venular widening. Compared to eGFR >90 mL/min/1.73m2 (referent), the multivariable HR (95% CI) among those with eGFR <45 mL/min/1.73m2 was 1.66 (0.93-2.96) for incident retinal arteriolar narrowing and 0.60 (0.17-1.85) for retinal venular widening.
Lack of data on albuminuria and loss to follow-up.
Retinal vessel diameters and CKD may run together through shared mechanisms but are not causally related.
PMCID: PMC3080044  PMID: 21439697
Retinal arteriolar diameter; retinal venular diameter; retinal vessel diameter; chronic kidney disease; eGFR; CKD; glomerular filtration rate
20.  Perilipin polymorphism interacts with saturated fat and carbohydrates to modulate insulin resistance1,2 
Macronutrient intakes and genetic variants have been shown to interact to alter the risk of insulin resistance, but replication of gene-nutrient interactions across independent populations may be difficult to achieve. Saturated fat and carbohydrate were previously shown to interact with genotype for insulin resistance for a variant of perilipin (PLIN), the major adipocyte-associated protein and a regulator of adipocyte metabolism. We investigated the same interaction for PLIN 11482G>A (rs894160) on insulin resistance in US men(n=462) and women(n=508) (mean ±SD, 49±16 years). In multivariate linear regression models, we found a significant (P<0.05) interaction between the ratio of saturated fat to carbohydrate intake as a continuous variable and PLIN 11482G>A for HOMA-IR (homeostasis model assessment of insulin resistance) in women. For carriers of the minor allele but not for non-carriers, as the ratio of saturated fat to carbohydrate intake increased, predicted HOMA-IR increased significantly (P=0.002). By dichotomizing the ratio of saturated fat to carbohydrate intake into high and low, we found significant interaction terms for insulin and HOMA-IR (P<0.05). When the ratio of saturated fat to carbohydrate was high, insulin and HOMA-IR were higher in minor allele carriers (P=0.004 and P=0.003, respectively), but did not differ when the ratio was low. Similar patterns or trends were observed when saturated fat and carbohydrate were dichotomized into high and low as individual macronutrients. Replication of the previously reported interaction between macronutrient intakes and PLIN genotype for insulin resistance reinforces the potential usefulness of applying genotype information in the dietary management of insulin resistance.
PMCID: PMC3117106  PMID: 21193293
21.  Effects of Fenofibrate on Plasma Oxidized LDL and 8-Isoprostane In a Sub-Cohort of GOLDN Participants 
Atherosclerosis  2010;214(2):422-425.
Fenofibrate significantly reduces circulating triglyceride (TG) concentrations, particularly in individuals with elevated levels. The purpose of the current study was to determine whether fenofibrate treatment reduces markers of oxidative stress, oxidized low density lipoprotein (ox-LDL) and 8-isoprostane (8-isoP), in a manner similar to TG where those with the highest levels show the greatest reductions.
The concentrations of TG, 8-isoP, and ox-LDL were measured in plasma before and after 3 weeks of fenofibrate treatment (160 mg/d) in a sub-cohort (n=187) of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study.
Data were divided into tertiles as determined by pre-treatment values of the respective target. Fenofibrate treatment resulted in significant reductions in TG concentrations by 24.2% (p<0.0001), 41.9% (p<0.0001), and 46.6% (p<0.0001) in tertiles 1, 2, and 3, respectively. Significant reductions were also observed in ox-LDL of 7.2% (p=0.0096), 8.5% (p=0.0019) and 12.1% (p<0.0001) in tertiles 1, 2, and 3, respectively. Finally, fenofibrate treatment resulted in a 32.7% increase (p=0.0201) in 8-isoP levels in tertile 1, but a significant decrease of 34.4% (p<0.0001) in tertile 3.
This study is the largest to date to demonstrate that fenofibrate reduces oxidative stress and the first to show a suppressive effect on 8-isoP levels in individuals with a high oxidative burden following short term (3 wk) drug therapy. Those with the highest baseline levels of ox-LDL and 8-isoP showed the greatest reductions following fenofibrate treatment. Given the role of oxidative stress in atherosclerosis and coronary heart disease, our observations may partially explain the efficacy of fenofibrate in reducing cardiovascular events in select patients.
PMCID: PMC3031718  PMID: 21159339
Fenofibrate; atherosclerosis; isoprostane; ox-LDL; triglyceride; GOLDN
22.  Markers of inflammation predict the long-term risk of developing chronic kidney disease: a population-based cohort study 
Kidney International  2011;80(11):1231-1238.
In animal models, inflammatory processes have been shown to have an important role in the development of kidney disease. In humans, however, the independent relation between markers of inflammation and the risk of chronic kidney disease (CKD) is not known. To clarify this, we examined the relationship of several inflammatory biomarker levels (high-sensitivity C-reactive protein, tumor necrosis factor-α receptor 2, white blood cell count, and interleukin-6) with the risk of developing CKD in a population-based cohort of up to 4926 patients with 15 years of follow-up. In cross-sectional analyses, we found that all these inflammation markers were positively associated with the outcome of interest, prevalent CKD. However, in longitudinal analyses examining the risk of developing incident CKD among those who were CKD-free at baseline, only tumor necrosis factor-α receptor 2, white blood cell count, and interleukin-6 levels (hazard ratios comparing highest with the lowest tertile of 2.10, 1.90, and 1.45, respectively), and not C-reactive protein (hazard ratio 1.09), were positively associated with incident CKD. Thus, elevations of most markers of inflammation predict the risk of developing CKD. Each marker should be independently verified.
PMCID: PMC3260339  PMID: 21866089
chronic kidney disease; CRP; inflammation; tumor necrosis factor-alpha
23.  A clustering analysis of lipoprotein diameters in the metabolic syndrome 
The presence of smaller low-density lipoproteins (LDL) has been associated with atherosclerosis risk, and the insulin resistance (IR) underlying the metabolic syndrome (MetS). In addition, some research has supported the association of very low-, low- and high-density lipoprotein (VLDL HDL) particle diameters with components of the metabolic syndrome (MetS), although this has been the focus of less research. We aimed to explore the relationship of VLDL, LDL and HDL diameters to MetS and its features, and by clustering individuals by their diameters of VLDL, LDL and HDL particles, to capture information across all three fractions of lipoprotein into a unified phenotype.
We used nuclear magnetic resonance spectroscopy measurements on fasting plasma samples from a general population sample of 1,036 adults (mean ± SD, 48.8 ± 16.2 y of age). Using latent class analysis, the sample was grouped by the diameter of their fasting lipoproteins, and mixed effects models tested whether the distribution of MetS components varied across the groups.
Eight discrete groups were identified. Two groups (N = 251) were enriched with individuals meeting criteria for the MetS, and were characterized by the smallest LDL/HDL diameters. One of those two groups, one was additionally distinguished by large VLDL, and had significantly higher blood pressure, fasting glucose, triglycerides, and waist circumference (WC; P < .001). However, large VLDL, in the absence of small LDL and HDL particles, did not associate with MetS features. These associations held after additionally controlling for VLDL, LDL and HDL particle concentrations.
While small LDL diameters remain associated with IR and the MetS, the occurrence of these in conjunction with a shift to overall larger VLDL diameter may identify those with the highest fasting glucose, TG and WC within the MetS. If replicated, the association of this phenotype with more severe IR-features indicated that it may contribute to identifying of those most at risk for incident type II diabetes and cardiometabolic disease.
PMCID: PMC3260106  PMID: 22182248
lipoprotein particle diameter; insulin resistance; nuclear resonance spectroscopy; Metabolic Syndrome; latent class analysis; GOLDN; waist circumference; hypertension; hypertriglyceridemia; fasting glucose
24.  High-fat meal effect on LDL, HDL, and VLDL particle size and number in the Genetics of Lipid-Lowering drugs and diet network (GOLDN): an interventional study 
Postprandial lipemia (PPL) is likely a risk factor for cardiovascular disease but these changes have not been well described and characterized in a large cohort. We assessed acute changes in the size and concentration of total and subclasses of LDL, HDL, and VLDL particles in response to a high-fat meal. Participants (n = 1048) from the Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN) Study who ingested a high-fat meal were included in this analysis. Lipids were measured at 0 hr (fasting), 3.5 hr, and 6 hr after a standardized fat meal. Particle size distributions were determined using nuclear magnetic resonance spectroscopy. Analyses were stratified by baseline triglycerides (normal vs. elevated) and gender. The effect of PPL on changes in lipoprotein subclasses was assessed using repeated measures ANOVA.
Postprandially, LDL-C, HDL-C, VLDL-C, and triglycerides increased regardless of baseline triglyceride status, with the largest increases in VLDL-C and TG; however, those with elevated triglycerides demonstrated larger magnitude of response. Total LDL particle number decreased over the 6-hour time interval, mostly from a decrease in the number of small LDL particles. Similarly, total VLDL particle number decreased due to reductions in medium and small VLDL particles. Large VLDL particles and chylomicrons demonstrated the largest increase in concentration. HDL particles demonstrated minimal overall changes in total particle number.
We have characterized the changes in LDL and VLDL particle number, and their subclass patterns following a high-fat meal.
PMCID: PMC3206850  PMID: 22008512
postprandial lipemia; lipoprotein particles; NMR; high-fat meal
25.  Associations of Plasma Phospholipid Omega-6 and Omega-3 Polyunsaturated Fatty Acid Levels and MRI Measures of Cardiovascular Structure and Function: The Multiethnic Study of Atherosclerosis 
Background. The association between plasma omega-6 fatty acids and cardiovascular disease (CVD) is unclear, and discrepancy remains concerning the cardiovascular benefit of the omega-3 fatty acid alpha-linolenic acid. Methods. Associations of plasma phospholipid fatty acid levels (arachidonic acid, linoleic acid, eicosapentaenoic acid, docosahexaenoic acid (DHA), and alpha-linolenic acid) with cardiac magnetic resonance imaging measures of left ventricular (LV) mass, LV volume, ejection fraction, stroke volume, and aortic distensibility were investigated in 1,274 adults. Results. Results of multivariate analysis showed no statistically significant associations of plasma omega-6 or omega-3 levels with cardiac magnetic resonance imaging measures. Stratification by gender revealed a positive association between DHA and LV mass in women (β = 1.89, P = 0.02; P interaction = 0.003) and a trend for a positive association between DHA and ejection fraction in men (β = 0.009, P = 0.05; P interaction = 0.03). Conclusion. Additional research is warranted to clarify the effects of plasma DHA on cardiac structure and function in women versus men.
PMCID: PMC3159987  PMID: 21869927

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