Dataset Information

Time-Course Analysis of Flow Mediated Dilation for the Evaluation of Endothelial Function After a High-Fat Meal in African Americans.

ABSTRACT: Flow-mediated dilation (FMD) is used to assess endothelial function through changes in vascular diameter after hyperemia. High-fat meal (HFM) has been shown to induce endothelial dysfunction; recent studies, however, reported conflicting results in obese African American women (AAW). Differences in the method used to analyze FMD may explain these discrepancies.In protocol 1, we assessed the time course of FMD and compared the repeatability of FMD using the individual maximum peak dilation (FMDpeak) and the dilation at 60 seconds (FMD60). Sixteen AAW (age, 42±10.4 years; body mass index [BMI], 39±5.8 kg/m(2)) were studied on 2 occasions, 4 weeks apart, under fasting conditions (study 1 and study 2). In protocol 2, we used the most repeatable measurement from protocol 1 to assess changes in endothelial function after an HFM in 17 AAW (agen 42±11.1 years; BMIn 38±5.6 kg/m(2)). We found that FMDpeak was the most repeatable measurement (N=16; study 1, 5.31±3.12% and study 2, 5.80±2.91%; r=0.94). After an HFM, the baseline brachial artery diameter significantly increased at 2 hours (0.10 mm; 95% confidence interval [CI], 0.01-0.18; P=0.03) and at 4 hours (0.17 mm; 95% CI, 0.09-0.25; P<0.001). At 2 hours, the FMDpeak decreased compared with pre-HFM (-1.76; 95% CI, -3.55-0.02; P?0.05).The individual's maximum peak dilation after hyperemia is the most consistent measure to assess the effect of an HFM on endothelial function. Endothelial dysfunction occurred at 2 hours after an HFM in AAW.URL: https://clinicaltrials.gov/ Unique identifiers: NCT01334554 and NCT02126735.

SUBMITTER: Marinos A

PROVIDER: S-EPMC4845211 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Time-Course Analysis of Flow Mediated Dilation for the Evaluation of Endothelial Function After a High-Fat Meal in African Americans.

Marinos Alejandro A Celedonio Jorge E JE Ramirez Claudia E CE Gottlieb JoAnn J Gamboa Alfredo A Hui Nian N Yu Chang C Stein C Michael CM Biaggioni Italo I Shibao Cyndya A CA

Journal of the American Heart Association 20151105 11

<h4>Background</h4>Flow-mediated dilation (FMD) is used to assess endothelial function through changes in vascular diameter after hyperemia. High-fat meal (HFM) has been shown to induce endothelial dysfunction; recent studies, however, reported conflicting results in obese African American women (AAW). Differences in the method used to analyze FMD may explain these discrepancies.<h4>Methods and results</h4>In protocol 1, we assessed the time course of FMD and compared the repeatability of FMD us ...[more]

PMID: 26541392

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Project description:Imputation of genome-wide single-nucleotide polymorphism (SNP) arrays to a larger known reference panel of SNPs has become a standard and an essential part of genome-wide association studies. However, little is known about the behavior of imputation in African Americans with respect to the different imputation algorithms, the reference population(s) and the reference SNP panels used. Genome-wide SNP data (Affymetrix 6.0) from 3207 African American samples in the Atherosclerosis Risk in Communities Study (ARIC) was used to systematically evaluate imputation quality and yield. Imputation was performed with the imputation algorithms MACH, IMPUTE and BEAGLE using several combinations of three reference panels of HapMap III (ASW, YRI and CEU) and 1000 Genomes Project (pilot 1 YRI June 2010 release, EUR and AFR August 2010 and June 2011 releases) panels with SNP data on chromosomes 18, 20 and 22. About 10% of the directly genotyped SNPs from each chromosome were masked, and SNPs common between the reference panels were used for evaluating the imputation quality using two statistical metrics-concordance accuracy and Cohen's kappa (?) coefficient. The dependencies of these metrics on the minor allele frequencies (MAF) and specific genotype categories (minor allele homozygotes, heterozygotes and major allele homozygotes) were thoroughly investigated to determine the best panel and method for imputation in African Americans. In addition, the power to detect imputed SNPs associated with simulated phenotypes was studied using the mean genotype of each masked SNP in the imputed data. Our results indicate that the genotype concordances after stratification into each genotype category and Cohen's ? coefficient are considerably better equipped to differentiate imputation performance compared with the traditionally used total concordance statistic, and both statistics improved with increasing MAF irrespective of the imputation method. We also find that both MACH and IMPUTE performed equally well and consistently better than BEAGLE irrespective of the reference panel used. Of the various combinations of reference panels, for both HapMap III and 1000 Genomes Project reference panels, the multi-ethnic panels had better imputation accuracy than those containing only single ethnic samples. The most recent 1000 Genomes Project release June 2011 had substantially higher number of imputed SNPs than HapMap III and performed as well or better than the best combined HapMap III reference panels and previous releases of the 1000 Genomes Project.

Project description:Background: African Americans (AA) have increased burdens of cardiovascular disease and cancer compared to Caucasian Americans (CA). This study addresses the possibility that genetic differences affecting the biology of the vascular endothelium could be a factor contributing to this health disparity. Methods: From self-identified, healthy, 20-29 year old AA (n=21) and CA (n=17), we established cultures of blood outgrowth endothelial cells (BOEC) and applied microarray profiling. BOEC have never been exposed to in vivo influences, and their gene expression reflects culture conditions (meticulously controlled) and donor genetics. Analysis used two distinct approaches. Significance Analysis of Microarray, a FDR-based test, identified significant differential expression of single genes. Gene Set Enrichment Analysis examined expression of pre-determined gene sets that survey each of nine biological systems relevant to endothelial cell biology. Results: At the highly stringent threshold of FDR=0, we identified 31 single genes that were differentially expressed, 4 higher and 27 lower in AA. “PSPH” exhibited the greatest fold-change (AA>CA), but this was entirely accounted for by a homolog (PSPHL) hidden within the PSPH probe set. Among other significantly different genes were: for AA>CA, SOS1, AMFR, FGFR3; and for AA<CA, ARVCF, BIN3, EIF4B. Many more (221 transcripts for 204 genes) were differentially expressed at the more customary, less stringent threshold of FDR<.05. Using the biological systems approach, we identified shear response biology as being significantly altered for AA versus CA. It detected an apparent tonic increase of expression (AA>CA) for 46/157 genes within that system. Conclusions: The most significant single gene changes detected for AA involved genes having substantial, known roles in endothelial biology. Biological systems analysis suggested that shear stress response, a critical regulator of endothelial function and vascular homeostasis, may be different between AA and CA. These results potentially have direct implications for the role of endothelial cells in both vascular disease (e.g., hypertension and stroke) and cancer (via angiogenesis). The present findings are consistent with our overarching hypothesis that genetic influences stemming from ancestral continent-of-origin could impact upon endothelial cell biology and thereby contribute to disparity of vascular-related disease burden amongst AA.

Dataset Information

Time-Course Analysis of Flow Mediated Dilation for the Evaluation of Endothelial Function After a High-Fat Meal in African Americans.

Publications

Time-Course Analysis of Flow Mediated Dilation for the Evaluation of Endothelial Function After a High-Fat Meal in African Americans.

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