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Articles by R. A Hegele
Total Records ( 5 ) for R. A Hegele
  M. B Lanktree , S. S Anand , S Yusuf , R. A Hegele and on behalf of the SHARE Investigators

Background— Functional copy number variation in the apolipoprotein(a) gene (LPA) underlies a variable number of protein kringle domains repeated in tandem in the lipoprotein(a) [Lp(a)] particle. Genomic analysis of LPA, including both single-nucleotide polymorphisms (SNPs) and kringle IV type 2 (KIV-2) copy number, has yet to be performed.

Methods and Results— First, we genotyped 49 SNPs within 100 kb of LPA in a multiethnic sample comprising South Asians (n=330), Chinese (n=304), and European Caucasians (n=272). Second, using quantitative polymerase chain reaction, we estimated the KIV-2 copy number in each sample. European Caucasians had the lowest KIV-2 copy number but displayed the strongest correlation between KIV-2 copy number and plasma Lp(a) concentration (rs=–0.31, P=4.2x10–7). SNP rs10455872, only prevalent in European Caucasians, was strongly associated with both plasma Lp(a) concentration (P=4.2x10–29) and KIV-2 copy number (P=7.2x10–5). LPA SNP rs6415084, within the same haplotype block as the KIV-2 variation, was significantly associated with both Lp(a) concentration and KIV-2 copy number in the same direction in all 3 ethnicities [Lp(a), P=5.3x10–7; KIV-2, P=2.6x10–4]. SNPs and KIV-2 copy number together explain a larger proportion of variation in plasma Lp(a) concentrations in European Caucasians (36%) than in Chinese (27%) or South Asians (21%).

Conclusions— LPA SNPs are in linkage disequilibrium with KIV-2 copy number, but KIV-2 copy number explains an increment in plasma Lp(a) variation over SNPs alone. Thus, both SNPs and KIV-2 copy number should be included in future genetic epidemiology studies of Lp(a).

  J. A Ronald , Y Chen , A. J. L Belisle , A. M Hamilton , K. A Rogers , R. A Hegele , B Misselwitz and B. K. Rutt

Background— Inflammation and neovascularization play critical roles in the stability of atherosclerotic plaques. Whole-body quantitative assessment of these plaque features may improve patient risk-stratification for life-threatening thromboembolic events and direct appropriate intervention. In this report, we determined the utility of the MR contrast agent gadofluorine-M (GdF) for staging plaque stability and compared this to the conventional agent Gd-DTPA.

Methods and Results— Five control and 7 atherosclerotic rabbits were sequentially imaged after administration of Gd-DTPA (0.2 mmol/kg) and GdF (0.1 mmol/kg) using a T1-weighted pulse sequence on a 3-T MRI scanner. Diseased aortic wall could be distinguished from normal wall based on wall-to-muscle contrast-to-noise values after GdF administration. RAM-11 (macrophages) and CD-31 (endothelial cells) immunostaining of MR-matched histological sections revealed that GdF accumulation was related to the degree of inflammation at the surface of plaques and the extent of core neovascularization. Importantly, an MR measure of GdF accumulation at both 1 and 24 hours after injection but not Gd-DTPA at peak enhancement was shown to correlate with a quantitative histological morphology index related to these 2 plaque features.

Conclusions— GdF-enhanced MRI of atherosclerotic plaques allows noninvasive quantitative information about plaque composition to be acquired at multiple time points after injection (within 1 and up to 24 hours after injection). This dramatically widens the imaging window for assessing plaque stability that is currently attainable with clinically approved MR agents, therefore opening the possibility of whole-body (including coronary) detection of unstable plaques in the future and potentially improved mitigation of cataclysmic cardiovascular events.

  S. H Ley , S. B Harris , P. W Connelly , M Mamakeesick , J Gittelsohn , T. M Wolever , R. A Hegele , B Zinman and A. J. Hanley

Background: Expanding evidence indicates that apolipoprotein B (apo B) is superior to LDL cholesterol as a marker of vascular disease. Although traditional lipid measures are known to predict type 2 diabetes, limited data are available regarding apo B. We assessed the association of apo B with incident type 2 diabetes and compared it with traditional lipid variables as a risk predictor in aboriginal Canadians.

Methods: Of an initial cohort of 606 individuals without diabetes in 1993–1995, 540 were contacted for the 10-year follow-up evaluation in 2003–2005. Fasting and 2-h postload glucose concentrations were obtained at baseline and follow-up to determine incident type 2 diabetes. Baseline fasting serum lipids were measured with standard laboratory procedures.

Results: The cumulative 10-year incidence of type 2 diabetes was 17.5%. High concentrations of apo B, triglycerides, and LDL cholesterol, and low concentrations of HDL cholesterol were individually associated with incident type 2 diabetes in univariate analyses. Comparing C statistics of univariate models showed apo B to be a superior determinant of incident diabetes compared with LDL (P = 0.026) or HDL (P = 0.004) cholesterol. With multivariate adjustment including waist circumference, apo B (odds ratio, 1.50; 95% CI, 1.11–2.02) and triglycerides (odds ratio, 1.49; 95% CI, 1.12–1.98) remained associated with incident diabetes, whereas LDL and HDL cholesterol became nonsignificant.

Conclusions: The association of plasma apo B with incident type 2 diabetes and its better prediction of risk compared with LDL or HDL cholesterol suggest the potential for the use of apo B in type 2 diabetes risk communication and prevention.

  P. W Connelly , B Zinman , G. F Maguire , M Mamakeesick , S. B Harris , R. A Hegele , R Retnakaran and A. J. G. Hanley

Paraoxonase 1 (PON1) has been reported to be associated with proteinuria in subjects with type 2 diabetes mellitus (T2DM). Plasma cystatin C is more accurate than creatinine for identifying stage 3 kidney disease in T2DM. We tested the hypothesis that PON1 and cystatin C would be associated in T2DM subjects from an Aboriginal Canadian community, who are at high risk for the development of nephropathy. PON1 A(-162)G and PON2 Ala148Gly genotypes, cystatin C, HbA1c, high density lipoprotein cholesterol (HDLC), waist circumference (waist), and duration of diabetes were included in the regression analysis with loge (ln) of PON1 mass as the dependent variable. A regression model including PON2 Ala148Gly genotype, HDLC, and ln cystatin C explained 25.8% of the variance in PON1 mass. Conversely, waist, age, ln HbA1c, ln duration of diabetes, and ln PON1 mass, but not PON2 genotype, explained 38% of the variance in cystatin C. Subjects with cystatin C estimated glomerular filtration rate (eGFR) <60 ml/min per 1.73 m2 (stage 3 kidney disease) had significantly lower PON1 mass compared with subjects with cystatin C-eGFR >60 ml/min per 1.73 m2. The lower mass of PON1, an anti-inflammatory HDL-associated enzyme, in T2DM with cystatin C-eGFR <60 ml/min per 1.73 m2 may contribute to their increased risk for cardiovascular disease.

  M. B Lanktree , S. S Anand , S Yusuf , R. A Hegele and the SHARE Investigators

Recent genome-wide association studies (GWAS) have reproducibly identified loci associated with plasma triglycerides (TG), HDL cholesterol, and LDL cholesterol. We sought to replicate these findings in a multiethnic population-based cohort using the curated single nucleotide polymorphism (SNP) set found on the new Illumina cardiovascular disease (CVD) beadchip, which contains approximately 50,000 SNPs densely mapping approximately 2,100 genes, selected based on their potential role in CVD. The sample consisted of individuals with European (n = 272), South Asian (n = 330), and Chinese (n = 304) ancestry. Identity by state clustering successfully classified individuals according to self-reported ethnicities. Associations between TG and APOA5, TG and LPL, HDL and CETP, and LDL and APOE were all identified (P < 2 x 10–6). In 13 loci, associations with the same SNP or a proxy SNP were identified in the same direction as previously reported (P < 0.05). Assessing the cumulative number of risk-associated alleles at multiple replicated SNPs increased the proportion of explained lipoprotein variance over and above traditional variables such as age, sex, body mass index, and ethnicity. The findings indicate the potential utility of the Illumina CVD beadchip, but they underscore the need to consider meta-analysis of results from commonly studied clinical or epidemiological samples.

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