OBJECTIVE:

There are several known monogenic causes of high and low high-density lipoprotein cholesterol (HDL-C) levels, but traditional sequencing studies have had limited success in identifying mutations in the majority of individuals with extreme HDL-C levels. The aim of this study was to assess the power of a targeted high-throughput sequencing strategy to elucidate the genetic basis of extreme HDL-C phenotypes. APPROACH AND

RESULTS:

We sequenced 195 genes with either established or implicated roles in lipid and lipoprotein metabolism plus 78 lipid-unrelated genes in patients with HDL-C <1st (n=40) or >99th (n=40) percentile values, and the results were compared with those of 498 individuals representative of the Dutch general population and 95 subjects with normal HDL-C (between 40th and 60th percentile values). The extreme HDL cohort carried more rare nonsynonymous variants in the lipid geneset than both the general population (odds ratio, 1.39; P=0.019) and normal HDL-C (odds ratio, 1.43; P=0.040) cohorts. The prevalence of such variants in the lipid-related and lipid-unrelated genesets was similar in the control groups, indicative of equal mutation rates. In the extreme HDL cohort, however, there was enrichment of rare nonsynonymous variants in the lipid versus the control geneset (odds ratio, 2.23; P<0.0001), and 70% of the lipid-related variants altered conserved nucleotides. The lipid geneset comprised 4 nonsense, 10 splice-site, and 8 coding indel variants, whereas the control geneset contained only 1 such variant. In the lipid geneset, 87% and 28% of the patients carried ≥2 and ≥5 rare variants.

CONCLUSIONS:

This study suggests that most extreme HDL-C phenotypes have a polygenic origin.

OBJECTIVE:

The objective of this study was to investigate the role of Kruppel-like factor (KLF) 10, a zinc-finger transcription factor, in bone marrow (BM)-derived cell responses to arterial endothelial injury. Accumulating evidence indicates that BM-derived progenitors are recruited to sites of vascular injury and contribute to endothelial repair. APPROACH AND

RESULTS:

In response to carotid artery endothelial denudation, KLF10 mRNA expression was markedly increased in both BM and circulating lin(-) progenitor cells. To examine the specific role of KLF10 in arterial reendothelialization, we used 2 models of endothelial denudation (wire- and thermal-induced injury) of the carotid artery in wild-type (WT) and KLF10(-/-) mice. WT mice displayed higher areas of reendothelialization compared with KLF10(-/-) mice after endothelial injury using either method. BM transplant studies revealed that reconstitution of KLF10(-/-) mice with WT BM fully rescued the defect in reendothelialization and increased lin(-)CD34(+)KDR(+) progenitors in the blood and injured carotid arteries. Conversely, reconstitution of WT mice with KLF10(-/-) BM recapitulated the defects in reendothelialization and peripheral cell progenitors. The media from cultured KLF10(-)/(-) BM progenitors was markedly inefficient in promoting endothelial cell growth and migration compared with the media from WT progenitors, indicative of defective paracrine trophic effects from KLF10(-)/(-) BM progenitors. Finally, BM-derived KLF10(-/-) lin(-) progenitors from reconstituted mice had reduced CXCR4 expression and impaired migratory responses.

CONCLUSIONS:

Collectively, these observations demonstrate a protective role for BM-derived KLF10 in paracrine and homing responses important for arterial endothelial injury and highlight KLF10 as a possible therapeutic target to promote endothelial repair in vascular disease states.

OBJECTIVE:

We aimed to analyze the association between hepatic steatosis and aortic valve sclerosis in the general population. APPROACH AND

RESULTS:

Cross-sectional data of 2212 men and women, aged 45 to 81 years, from the baseline examination of the population-based Study of Health in Pomerania (SHIP-0) were analyzed. Hepatic steatosis was primarily defined as the presence of a hyperechogenic ultrasound pattern of the liver. Aortic valve sclerosis was determined by echocardiography. In our sample, hepatic steatosis was present in 877 (39.7%) individuals. Among participants with hepatic steatosis, aortic valve sclerosis was more common (n=323; 36.8%) compared with participants without hepatic steatosis (n=379; 28.4%; P<0.001). After adjustment for potential confounders, individuals with hepatic steatosis had 33% higher odds of aortic valve sclerosis compared with those without hepatic steatosis (95% confidence interval, 6%-66%; P=0.014). Additional adjustment for high-sensitive C-reactive protein, serum ferritin levels, and white blood cells slightly reduced the association to 32% (95% confidence interval, 4%-66%; P=0.021).

CONCLUSIONS:

Our findings add evidence that hepatic steatosis and aortic valve sclerosis are interrelated after adjustment for major confounders. The release of proatherogenic substances by the steatotic liver or its contribution to insulin resistance and dyslipidemia may contribute to the development of calcification and sclerosis of the aortic valve.

Aneurysmal arterial disease is a vascular degenerative condition that is distinct from atherosclerotic and other occlusive arterial diseases. There is regionalization of the predisposition to aneurysm formation within the vascular tree, and the pathological process varies with location. Infrarenal abdominal aortic aneurysm (AAA) is the most common manifestation of aneurysmal disease, and smoking is the dominant risk factor. Smoking is a much greater risk factor for AAA than for atherosclerosis. In addition to playing a role in the pathogenesis of AAA, smoking also increases the rate of expansion and risk of rupture of established AAA. The mechanistic relationship between AAA and smoking is being established by the use of enhanced animal models that are dependent on smoke or smoke components. The mechanisms seem to involve durable alterations in vascular smooth muscle cell and inflammatory cell function. This review examines the clinical, epidemiological, and mechanistic evidence implicating smoking as a cause of aneurysms, focusing on AAA.

Acute rupture or erosion of a coronary atheromatous plaque and subsequent coronary artery thrombosis cause the majority of sudden cardiac deaths and myocardial infarctions. Cigarette smoking is a major risk factor for acute coronary thrombosis. Indeed, a majority of sudden cardiac deaths attributable to acute thrombosis are in cigarette smokers. Both active and passive cigarette smoke exposure seem to increase the risk of coronary thrombosis and myocardial infarctions. Cigarette smoke exposure seems to alter the hemostatic process via multiple mechanisms, which include alteration of the function of endothelial cells, platelets, fibrinogen, and coagulation factors. This creates an imbalance of antithrombotic/prothrombotic factors and profibrinolytic/antifibrinolytic factors that support the initiation and propagation of thrombosis.

OBJECTIVE:

Endothelial cells (ECs) can undergo an endothelial-mesenchymal transition with tissue fibrosis. Wnt- and Msx2-regulated signals participate in arteriosclerotic fibrosis and calcification. We studied the impact of Wnt7, Msx2, and Dkk1, a Wnt7 antagonist, on endothelial-mesenchymal transition in primary aortic ECs. APPROACH AND

RESULTS:

Transduction of aortic ECs with vectors expressing Dkk1 suppressed EC differentiation and induced a mineralizing myofibroblast phenotype. Dkk1 suppressed claudin 5, PECAM, cadherin 5 (Cdh5), Tie1, and Tie2. Dkk1 converted the cuboidal cell monolayer into a spindle-shaped multilayer and inhibited EC cord formation. Myofibroblast and osteogenic markers, SM22, type I collagen, Osx, Runx2, and alkaline phosphatase, were upregulated by Dkk1 via activin-like kinase/Smad pathways. Dkk1 increased fibrotic mineralization of aortic ECs cultured under osteogenic conditions-the opposite of mesenchymal cell responses. Msx2 and Wnt7b maintained morphology and upregulated markers of differentiated ECs. Deleting EC Wnt7b with the Cdh5-Cre transgene in Wnt7b(fl/fl);LDLR(-/-) mice upregulated aortic osteogenic genes (Osx, Sox9, Runx2, and Msx2) and nuclear phospho-Smad1/5, and increased collagen and calcium accumulation.

CONCLUSIONS:

Dkk1 enhances endothelial-mesenchymal transition in aortic ECs, whereas Wnt7b and Msx2 signals preserve EC phenotype. EC responses to Dkk1, Wnt7b, and Msx2 are the opposite of mesenchymal responses, coupling EC phenotypic stability with osteofibrogenic predilection during arteriosclerosis.

OBJECTIVE:

Dysregulated angiotensin II (Ang II) signaling induces local vascular interleukin-6 (IL-6) secretion, producing leukocyte infiltration and life-threatening aortic dissections. Precise mechanisms by which IL-6 signaling induces leukocyte recruitment remain unknown. T-helper 17 lymphocytes (Th17) have been implicated in vascular pathology, but their role in the development of aortic dissections is poorly understood. Here, we tested the relationship of IL-6-signal transducer and activator of transcription-3 signaling with Th17-induced inflammation in the formation of Ang II-induced dissections in C57BL/6 mice. APPROACH AND

RESULTS:

Ang II infusion induced aortic dissections and CD4(+)-interleukin 17A (IL-17A)-expressing Th17 cell accumulation in C57BL/6 mice. A blunted local Th17 activation, macrophage recruitment, and reduced incidence of aortic dissections were seen in IL-6(-/-) mice. To determine the pathological roles of Th17 lymphocytes, we treated Ang II-infused mice with IL-17A-neutralizing antibody or infused Ang II in genetically deficient IL-17A mice and found decreased aortic chemokine monocytic chemotactic protein-1 production and macrophage recruitment, leading to a reduction in aortic dissections. This effect was independent of blood pressure in IL-17A-neutralizing antibody experiment. Application of a cell-permeable signal transducer and activator of transcription-3 inhibitor to downregulate the IL-6 pathway decreased aortic dilation and Th17 cell recruitment. We also observed increased aortic Th17 infiltration and IL-17 mRNA expression in patients with thoracic aortic dissections. Finally, we found that Ang II-mediated aortic dissections occurred independent of blood pressure changes.

CONCLUSIONS:

Our results indicate that the IL-6-signal transducer and activator of transcription-3 signaling pathway converges on Th17 recruitment and IL-17A signaling upstream of macrophage recruitment, mediating aortic dissections.

OBJECTIVE:

Current guidelines do not support the use of genetic profiles in risk assessment of coronary heart disease (CHD). However, new single nucleotide polymorphisms associated with CHD and intermediate cardiovascular traits have recently been discovered. We aimed to compare several multilocus genetic risk score (MGRS) in terms of association with CHD and to evaluate clinical use. APPROACH AND

RESULTS:

We investigated 6 Swedish prospective cohort studies with 10 612 participants free of CHD at baseline. We developed 1 overall MGRS based on 395 single nucleotide polymorphisms reported as being associated with cardiovascular traits, 1 CHD-specific MGRS, including 46 single nucleotide polymorphisms, and 6 trait-specific MGRS for each established CHD risk factors. Both the overall and the CHD-specific MGRS were significantly associated with CHD risk (781 incident events; hazard ratios for fourth versus first quartile, 1.54 and 1.52; P<0.001) and improved risk classification beyond established risk factors (net reclassification improvement, 4.2% and 4.9%; P=0.006 and 0.017). Discrimination improvement was modest (C-index improvement, 0.004). The polygene MGRS performed worse than the CHD-specific MGRS. We estimate that 1 additional CHD event for every 318 people screened at intermediate risk could be saved by measuring the CHD-specific genetic score in addition to the established risk factors.

CONCLUSIONS:

Our results indicate that genetic information could be of some clinical value for prediction of CHD, although further studies are needed to address aspects, such as feasibility, ethics, and cost efficiency of genetic profiling in the primary prevention setting.

OBJECTIVE:

To elucidate the functions of sister-of-mammalian grainyhead (SOM1) and SOM3 in endothelial cells. APPROACH AND

RESULTS:

Overexpression of SOM1 in primary human endothelial cells induced migration, phosphorylation of Akt1 and endothelial nitric oxide synthase, and protected against apoptosis, whereas SOM3 had opposite effects; isoform-specific knockdowns confirmed the disparate effects on apoptosis. After reporter assays demonstrated that both are active transcription factors, microarray analyses revealed that they induce different target genes, which could explain the different cellular effects. Overexpression of SOM3 in zebrafish embryos resulted in increased lethality and severe deformations, whereas SOM1 had no deleterious effect.

CONCLUSIONS:

Our data demonstrate that the splice variant-derived isoforms SOM1 and SOM3 induce opposing effects in primary human endothelial cells and in a whole animal model, most likely through the induction of different target genes.