A closed-loop cholesterol shunt controlling experimental dyslipidemia.

Because the high-density lipoprotein receptor (HDL-R) is a key element in cholesterol homeostasis and a potential therapeutic target for hypercholesterolemic drugs, an understanding of HDL-R regulation is essential. The sterol regulatory element (SRE) binding protein-1a (SREBP-1a) was shown to positively regulate HDL-R gene expression through two SREs. SREBP-1a requires the presence of a coactivator like simian-virus-40-protein-1 (Sp1) to promote maximum activation of the HDL-R promoter. Negative regulatory factors are also known to play a role in cholesterol homeostasis, and the ubiquitous Yin Yang-1 zinc finger transcription factor (YY1) has been shown to repress several sterol-responsive gene promoters. A search of the rat HDL-R promoter revealed two putative YY1 binding sites (distal, -1329 to -1321; proximal, -1211 to -1203). Upon removal of both YY1 binding sites, YY1 was unable to repress HDL-R activation under basal (unstimulated) promoter conditions. However, YY1 was still an efficient transcriptional repressor for SREBP-1a-induced activation. YY1 was able to attenuate the transcriptional synergy caused by the combined actions of SREBP-1a and Sp1. Two-hybrid studies confirmed that YY1 bound with high affinity to SREBP-1a, and mobility shift assays demonstrated that YY1 could disrupt SREBP-1a binding to both SREs. The molecular consequence of YY1 intervention seems to override any positive interactions between Sp-1 and SREBP-1a and results in the disruption of SREBP-1a binding to the SREs in the HDL-R promoter.

Because the high-density lipoprotein receptor (HDL-R) is a key element in cholesterol homeostasis and a potential therapeutic target for hypercholesterolemic drugs, an understanding of HDL-R regulation is essential. The sterol regulatory element (SRE) binding protein-1a (SREBP-1a) was shown to positively regulate HDL-R gene expression through two SREs. SREBP-1a requires the presence of a coactivator like simian-virus-40-protein-1 (Sp1) to promote maximum activation of the HDL-R promoter. Negative regulatory factors are also known to play a role in cholesterol homeostasis, and the ubiquitous Yin Yang-1 zinc finger transcription factor (YY1) has been shown to repress several sterol-responsive gene promoters. A search of the rat HDL-R promoter revealed two putative YY1 binding sites (distal, −1329 to −1321; proximal, −1211 to −1203). Upon removal of both YY1 binding sites, YY1 was unable to repress HDL-R activation under basal (unstimulated) promoter conditions. However, YY1 was still an efficient transcriptional repressor for SREBP-1a-induced activation. YY1 was able to attenuate the transcriptional synergy caused by the combined actions of SREBP-1a and Sp1. Two-hybrid studies confirmed that YY1 bound with high affinity to SREBP-1a, and mobility shift assays demonstrated that YY1 could disrupt SREBP-1a binding to both SREs. The molecular consequence of YY1 intervention seems to override any positive interactions between Sp-1 and SREBP-1a and results in the disruption of SREBP-1a binding to the SREs in the HDL-R promoter.

The LDL receptor (LDLR) plays an essential role in the regulation of plasma (LDL) cholesterol concentrations by virtue of its ability to clear plasma LDL. Down-regulation of the LDLR by proprotein convertase subtilisin/kexin 9 (PCSK9) has recently emerged as a regulatory mechanism that controls plasma LDL cholesterol concentrations. Studies in which PCSK9 is over-expressed in mice, have demonstrated that PCSK9, by enhancing hepatic LDLR degradation, decreases the availability of the LDLR for LDL uptake, resulting in increased plasma LDL cholesterol levels. However, PCSK9 has also recently been shown to mediate down-regulation of surface receptors other than the LDLR, suggesting that it may have much broader roles than initially thought.

The Clinical Efficacy Assessment Subcommittee of the American College of Physicians–American Society of Internal Medicine acknowledges the scientific validity of this product as a background paper and as a review that captures the levels of evidence in the management of patients with chronic stable angina as of November 17, 2002. The American College of Cardiology (ACC)/American Heart Association (AHA) Task Force on Practice Guidelines regularly reviews existing guidelines to determine when an update or a full revision is needed. This process gives priority to areas in which major changes in text, and particularly recommendations, are merited on the basis of new understanding or evidence. Minor changes in verbiage and references are discouraged. The ACC/AHA/American College of Physicians–American Society of Internal Medicine (ACP-ASIM) Guidelines for the Management of Patients With Chronic Stable Angina, which were published in June 1999, have now been updated. The full-text guideline incorporating the updated material is available on the Internet (www.acc.org or www.americanheart.org) in both a track-changes version showing the changes in the 1999 guideline in strike-out (deleted text) and highlighting …

In this study, we examined the insertion/deletion (Ins/Del) and XbaI polymorphisms of the apolipoprotein B (APOB) gene and the -36delG polymorphism in the sterol regulatory element binding protein-1a (SREBP-1a) gene in 298 patients with non-diabetic angiographically assessed coronary artery disease (CAD), and 188 healthy controls, from a Brazilian population of European descent. Del/X+ haplotype carriers had higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in patients (TC, p = 0.05; LDL-C, p = 0.049) and controls (TC, p = 0.004; LDL-C, p = 0.013). No association was detected between the SREBP-1a-36delG polymorphism and lipid levels, but a significant interaction effect between APOB and SREBP-1a polymorphisms was observed in the patient sample on TC (p = 0.005) and on LDL-C (p = 0.019) levels. Carriers of the APOB Del/X+ haplotype and SREBP-1a G-G- genotype showed the highest levels of these lipid parameters. This effect of interaction was not observed in the control sample. Despite the associations with lipids, these polymorphisms were not associated with CAD risk or severity in this sample.

In this issue of Circulation , Noda et al1 report an association between low levels of low-density lipoprotein cholesterol (LDL-C) and an increase in the risk of fatal intraparenchymal intracerebral hemorrhage in a Japanese population-based cohort. The relationship between lipid levels and stroke is complex. The Prospective Studies Collaboration conducted a meta-analysis evaluating the association between blood cholesterol and vascular mortality based on data from 61 prospective cohort studies including nearly 900 000 persons free of vascular disease at baseline (11.6 million person-years at risk).2 Lower levels of usual total cholesterol were strongly associated with lower risk of fatal ischemic heart disease; every 1 mmol/L lower cholesterol was associated with a 56% reduction (hazard ratio [HR], 0.44; 95% CI, 0.42 to 0.48) in those 40 to 49 years of age, a 34% reduction (HR, 0.66; 95% CI, 0.65 to 0.68) in those 50 to 69 years of age, and a 17% reduction (HR, 0.83; 95% CI, 0.81 to 0.85) in those 70 to 89 years of age. In contrast to death resulting from ischemic heart disease, there was only a weak relationship between usual total cholesterol and death caused by stroke in those 40 to 59 years of age (HR, 0.90; 95% CI, 0.84 to 0.97 for every 1 mmol/L lower cholesterol) and no relationship for older age groups after accounting for blood pressure. An analysis combing the data for the Prospective Studies Collaboration with data from the Multiple Risk Factors Intervention Trial (MRFIT) also found that lower usual total cholesterol was associated with a lower risk of fatal stroke in those 40 to 49 years of age (HR, 0.87; 95% CI, 0.76 to 1.00 per 1 mmol/L lower total cholesterol), with similar reductions in those 50 to 59 (HR, 0.91; 95% CI, 0.85 to 0.97) and 60 …

Anti-Inflammatory Effects of Statins Beyond Cholesterol Lowering

Identifying the Vulnerable Patient with Rupture-Prone Plaque

We studied the relationship of apolipoprotein E (apoE) isoforms and coronary artery disease (CAD) in 224 African Americans and 326 Caucasians undergoing diagnostic coronary angiography. The presence of CAD was defined as >50% stenosis in at least one artery. ApoE allele frequencies were 0.12, 0.62, and 0.26 for epsilon 2, epsilon 3, and epsilon 4, respectively, in African Americans and 0.08, 0.78, and 0.14 for epsilon 2, epsilon 3, and epsilon 4, respectively, in Caucasians. Among African Americans, CAD was present in 9 of 34 epsilon 2 carriers (26%), significantly smaller (P < 0.05) in proportion compared with 39 of 82 epsilon 3 carriers and 43 of 92 epsilon 4 carriers (48% and 47%, respectively), suggesting a protective effect of the epsilon 2 allele. No such difference was seen in Caucasians. In African Americans but not Caucasians, LDL cholesterol was lower in epsilon 2 carriers than in epsilon 3 and epsilon 4 carriers (106 vs. 127 and 134 mg/dl, respectively; P < 0.005). After adjusting for lipid levels, the association between apoE2 and CAD was no longer significant. Thus, the protective effect of apoE2 seen in African Americans could be explained by a favorable lipid profile in epsilon 2 carriers, whereas in Caucasians, the absence of such a protective effect could be attributable to the lack of effect of apoE2 on the lipid profile.

Improved Coronary Risk Assessment With Electron Beam Computed Tomography in an Asymptomatic Female With Familial Hypercholesterolemia

Select Articles Published on the Topic of Coronary Heart Disease in 2013

<i>Circulation</i> Editors' Picks

Since its market launch in the early 2000s, ezetimibe has had a stormy history of acceptance and use by the clinical community. Ezetimibe’s initial approval by regulatory bodies was based primarily on its low side effect profile together with its ability to consistently reduce low-density lipoprotein (LDL) cholesterol by ≈20% either as monotherapy or as an additive to statin therapy. Notably, approval was granted despite the absence from ezetimibe’s portfolio of studies, demonstrating reductions in hard clinical cardiovascular outcomes, such as myocardial infarction or stroke. By 2006, ezetimibe accounted for >15% of all prescriptions for lipid-lowering medications in the United States,1 reflecting that era’s stout faith in the reliability of LDL cholesterol as a surrogate marker for clinical end points, together with practitioners’ positive real-world experiences with ezetimibe’s biochemical efficacy and good tolerability. It was tacitly anticipated that the pending cardiovascular outcome studies would be positive, eventually vindicating the early confidence that clinicians placed in the drug. However, the waters grew rough for ezetimibe in 2008. First, the Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression (ENHANCE) trial conducted for 24 months in 720 patients with familial hypercholesterolemia showed that combined therapy with ezetimibe and simvastatin did not significantly change carotid intima–media thickness when compared with simvastatin alone, despite decreased levels of LDL cholesterol.2 Next, the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) trial conducted for 52 months in 1873 elderly nondiabetic patients with aortic stenosis showed that ezetimibe plus simvastatin did not reduce the composite outcome of combined aortic valve events and ischemic events.3 To add insult to injury, the 2009 Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol-6-HDL and LDL Treatment Strategies in Atherosclerosis (ARBITER 6-HALTS) study demonstrated that when combined with a statin, extended-release niacin caused a significant …

Lipoprotein(a) [Lp(a)] has enhanced atherothrombotic properties. The ability of Lp(a) levels to predict adverse cardiovascular outcomes in patients undergoing coronary angiography has not been examined. The relationship between serum Lp(a) levels and both the extent of angiographic disease and 3-year incidence of major adverse cardiovascular events (MACE: death, myocardial infarction, stroke, and coronary revascularization) was investigated in 2,769 patients who underwent coronary angiography [median Lp(a) 16.4 mg/dl, elevated levels (≥30 mg/dl) in 38%]. An elevated Lp(a) was associated with a 2.3-fold [95% confidence interval (CI), 1.7-3.2, P < 0.001] greater likelihood of having a significant angiographic stenosis and 1.5-fold (95 CI, 1.3-1.7, P < 0.001) greater chance of three-vessel disease. Lp(a)≥30 mg/dl was associated with a greater rate of MACE (41.8 vs. 35.8%, P = 0.005), primarily due to a greater need for coronary revascularization (30.9 vs. 26.0%, P = 0.02). A relationship between Lp(a) levels and cardiovascular outcome was observed in patients with an LDL cholesterol (LDL-C) ≥70-100 mg/dl (P = 0.049) and >100 mg/dl (P = 0.02), but not <70 mg/dl (P = 0.77). Polymorphisms of Lp(a) were also associated with both plasma Lp(a) levels and coronary stenosis, but not a greater rate of MACE. Lp(a) levels correlate with the extent of obstructive disease and predict the need for coronary revascularization in subjects with suboptimal LDL-C control. This supports the need to intensify lipid management in patients with elevated Lp(a) levels.

This statement examines the cardiovascular complications of diabetes mellitus and considers opportunities for their prevention. These complications include coronary heart disease (CHD), stroke, peripheral arterial disease, nephropathy, retinopathy, and possibly neuropathy and cardiomyopathy. Because of the aging of the population and an increasing prevalence of obesity and sedentary life habits in the United States, the prevalence of diabetes is increasing. Thus, diabetes must take its place alongside the other major risk factors as important causes of cardiovascular disease (CVD). In fact, from the point of view of cardiovascular medicine, it may be appropriate to say, “diabetes is a cardiovascular disease.” The most prevalent form of diabetes mellitus is type 2 diabetes. This disorder typically makes its appearance later in life. The underlying metabolic causes of type 2 diabetes are the combination of impairment in insulin-mediated glucose disposal (insulin resistance) and defective secretion of insulin by pancreatic β-cells. Insulin resistance develops from obesity and physical inactivity, acting on a substrate of genetic susceptibility.1 2 Insulin secretion declines with advancing age,3 4 and this decline may be accelerated by genetic factors.5 6 Insulin resistance typically precedes the onset of type 2 diabetes and is commonly accompanied by other cardiovascular risk factors: dyslipidemia, hypertension, and prothrombotic factors.7 8 The common clustering of these risk factors in a single individual has been called the metabolic syndrome. Many patients with the metabolic syndrome manifest impaired fasting glucose (IFG)9 even when they do not have overt diabetes mellitus.10 The metabolic syndrome commonly precedes the development of type 2 diabetes by many years11 ; of great importance, the risk factors that constitute this syndrome contribute independently to CVD risk. Recently, new criteria have been accepted for the diagnosis of diabetes.9 The upper threshold of fasting plasma glucose for the …