Doubling Expression of the Low Density Lipoprotein Receptor by Truncation of the 3′-Untranslated Region Sequence Ameliorates Type III Hyperlipoproteinemia in Mice Expressing the Human ApoE2 Isoform

The primary receptor mediating clearance of apolipoprotein (apo)E- and apoB100-containing lipoproteins from the circulation is the low density lipoprotein (LDL) receptor. Reduced expression of the LDLR is believed to be a precipitating factor in the pathogenesis of type III hyperlipoproteinemia (HLP) in some humans homozygous for the apoE2 allele (APOE*2). To test the effect of genetic changes in LDL receptor expression on the pathogenesis of type III HLP, we have generated a variant allele at the endogenous mouse Ldlr locus that expresses the human LDL receptor transcript. Transcription of the human LDLR minigene is regulated by the endogenous mouse promoter sequence, but a truncation of 3'-untranslated region results in increased mRNA stability. Consequently, in liver of heterozygotes, steady state levels of mouse and human LDLR transcripts are 50 and 180% the levels of total transcript in wild type mice, respectively. Overall, the 2.3-fold normal level of LDLR message in heterozygotes completely ameliorates type III HLP caused by the homozygosity for the human APOE*2 allele, normalizing their plasma lipoprotein profile. We conclude that a modest increase in expression of the LDLR through message stabilization is sufficient to prevent precipitation of type III HLP in mice

RANTES/CCL5 and Risk for Coronary Events: Results from the MONICA/KORA Augsburg Case-Cohort, Athero-Express and CARDIoGRAM Studies

BACKGROUND: The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events. METHODS AND FINDINGS: We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±4.8 years). Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors and lifestyle factors revealed no significant association between RANTES and incident coronary events (HR [95% CI] for increasing RANTES tertiles 1.0, 1.03 [0.75-1.42] and 1.11 [0.81-1.54]). None of six CCL5 single nucleotide polymorphisms and no common haplotype showed significant associations with coronary events. Also in the CARDIoGRAM study (>22,000 cases, >60,000 controls), none of these CCL5 SNPs was significantly associated with coronary artery disease. In the prospective Athero-Express biobank study, RANTES plaque levels were measured in 606 atherosclerotic lesions from patients who underwent carotid endarterectomy. RANTES content in atherosclerotic plaques was positively associated with macrophage infiltration and inversely associated with plaque calcification. However, there was no significant association between RANTES content in plaques and risk for coronary events (mean follow-up 2.8±0.8 years). CONCLUSIONS: High RANTES plaque levels were associated with an unstable plaque phenotype. However, the absence of associations between (i) RANTES serum levels, (ii) CCL5 genotypes and (iii) RANTES content in carotid plaques and either coronary artery disease or incident coronary events in our cohorts suggests that RANTES may not be a novel coronary risk biomarker. However, the potential relevance of RANTES levels in platelet-poor plasma needs to be investigated in further studies

RANTES/CCL5 and risk for coronary events: Results from the MONICA/KORA Augsburg case-cohort, Athero-express and CARDIoGRAM studies

Background: The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events. Methods and Findings: We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±

Genome-wide association study identifies six new loci influencing pulse pressure and mean arterial pressure.

Numerous genetic loci have been associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP) in Europeans. We now report genome-wide association studies of pulse pressure (PP) and mean arterial pressure (MAP). In discovery (N = 74,064) and follow-up studies (N = 48,607), we identified at genome-wide significance (P = 2.7 × 10(-8) to P = 2.3 × 10(-13)) four new PP loci (at 4q12 near CHIC2, 7q22.3 near PIK3CG, 8q24.12 in NOV and 11q24.3 near ADAMTS8), two new MAP loci (3p21.31 in MAP4 and 10q25.3 near ADRB1) and one locus associated with both of these traits (2q24.3 near FIGN) that has also recently been associated with SBP in east Asians. For three of the new PP loci, the estimated effect for SBP was opposite of that for DBP, in contrast to the majority of common SBP- and DBP-associated variants, which show concordant effects on both traits. These findings suggest new genetic pathways underlying blood pressure variation, some of which may differentially influence SBP and DBP

Genetic associations at 53 loci highlight cell types and biological pathways relevant for kidney function.

Reduced glomerular filtration rate defines chronic kidney disease and is associated with cardiovascular and all-cause mortality. We conducted a meta-analysis of genome-wide association studies for estimated glomerular filtration rate (eGFR), combining data across 133,413 individuals with replication in up to 42,166 individuals. We identify 24 new and confirm 29 previously identified loci. Of these 53 loci, 19 associate with eGFR among individuals with diabetes. Using bioinformatics, we show that identified genes at eGFR loci are enriched for expression in kidney tissues and in pathways relevant for kidney development and transmembrane transporter activity, kidney structure, and regulation of glucose metabolism. Chromatin state mapping and DNase I hypersensitivity analyses across adult tissues demonstrate preferential mapping of associated variants to regulatory regions in kidney but not extra-renal tissues. These findings suggest that genetic determinants of eGFR are mediated largely through direct effects within the kidney and highlight important cell types and biological pathways

Apo E structure determines VLDL clearance and atherosclerosis risk in mice

We have generated mice expressing the human apo E4 isoform in place of the endogenous murine apo E protein and have compared them with mice expressing the human apo E3 isoform. Plasma lipid and apolipoprotein levels in the mice expressing only the apo E4 isoform (4/4) did not differ significantly from those in mice with the apo E3 isoform (3/3) on chow and were equally elevated in response to increased lipid and cholesterol in their diet. However, on all diets tested, the 4/4 mice had approximately twice the amount of cholesterol, apo E, and apo B-48 in their VLDL as did 3/3 mice. The 4/4 VLDL competed with human LDL for binding to the human LDL receptor slightly better than 3/3 VLDL, but the VLDL clearance rate in 4/4 mice was half that in 3/3 mice. On an atherogenic diet, there was a trend toward greater atherosclerotic plaque size in 4/4 mice compared with 3/3 mice. These data, together with our earlier observations in wild-type and human APOE*2-replacement mice, demonstrate a direct and highly significant correlation between VLDL clearance rate and mean atherosclerotic plaque size. Therefore, differences solely in apo E protein structure are sufficient to cause alterations in VLDL residence time and atherosclerosis risk in mice

Disruption of LDL but not VLDL clearance in autosomal recessive hypercholesterolemia

Genetic defects in LDL clearance result in severe hypercholesterolemia and premature atherosclerosis. Mutations in the LDL receptor (LDLR) cause familial hypercholesterolemia (FH), the most severe form of genetic hypercholesterolemia. A phenocopy of FH, autosomal recessive hypercholesterolemia (ARH), is due to mutations in an adaptor protein involved in LDLR internalization. Despite comparable reductions in LDL clearance rates, plasma LDL levels are substantially lower in ARH than in FH. To determine the metabolic basis for this difference, we examined the synthesis and catabolism of VLDL in murine models of FH (Ldlr(–/–)) and ARH (Arh(–/–)). The hyperlipidemic response to a high-sucrose diet was greatly attenuated in Arh(–/–) mice compared with Ldlr(–/–) mice despite similar rates of VLDL secretion. The rate of VLDL clearance was significantly higher in Arh(–/–) mice than in Ldlr(–/–) mice, suggesting that LDLR-dependent uptake of VLDL is maintained in the absence of ARH. Consistent with these findings, hepatocytes from Arh(–/–) mice (but not Ldlr(–/–) mice) internalized β-migrating VLDL (β-VLDL). These results demonstrate that ARH is not required for LDLR-dependent uptake of VLDL by the liver. The preservation of VLDL remnant clearance attenuates the phenotype of ARH and likely contributes to greater responsiveness to statins in ARH compared with FH

Identification of ADAMTS7 as a novel locus for coronary atherosclerosis and association of ABO with myocardial infarction in the presence of coronary atherosclerosis:two genome-wide association studies

BACKGROUND: We tested whether genetic factors distinctly contribute to either development of coronary atherosclerosis or, specifically, to myocardial infarction in existing coronary atherosclerosis. METHODS: We did two genome-wide association studies (GWAS) with coronary angiographic phenotyping in participants of European ancestry. To identify loci that predispose to angiographic coronary artery disease (CAD), we compared individuals who had this disorder (n=12,393) with those who did not (controls, n=7383). To identify loci that predispose to myocardial infarction, we compared patients who had angiographic CAD and myocardial infarction (n=5783) with those who had angiographic CAD but no myocardial infarction (n=3644). FINDINGS: In the comparison of patients with angiographic CAD versus controls, we identified a novel locus, ADAMTS7 (p=4·98×10(-13)). In the comparison of patients with angiographic CAD who had myocardial infarction versus those with angiographic CAD but no myocardial infarction, we identified a novel association at the ABO locus (p=7·62×10(-9)). The ABO association was attributable to the glycotransferase-deficient enzyme that encodes the ABO blood group O phenotype previously proposed to protect against myocardial infarction. INTERPRETATION: Our findings indicate that specific genetic predispositions promote the development of coronary atherosclerosis whereas others lead to myocardial infarction in the presence of coronary atherosclerosis. The relation to specific CAD phenotypes might modify how novel loci are applied in personalised risk assessment and used in the development of novel therapies for CAD. FUNDING: The PennCath and MedStar studies were supported by the Cardiovascular Institute of the University of Pennsylvania, by the MedStar Health Research Institute at Washington Hospital Center and by a research grant from GlaxoSmithKline. The funding and support for the other cohorts contributing to the paper are described in the webappendix