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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Atherosclerosis is an inflammatory process triggered by the presence of lipids in the vascular wall and encompasses a complex interaction between inflammatory cells, vascular elements and lipoproteins through the expression of several adhesion molecules and cytokines. Activation of the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR-alpha) has been demonstrated to modulate many aspects of lipoprotein metabolism and inflammation in vitro as well as in animal and human studies. The tissue distribution of PPAR-alpha is extensive and it is abundantly present in the vascular wall where it may mediate many of anti-inflammatory and antiatherogenic effects. Major clinical trials, such as the Veterans Affairs High-Density Lipoprotein Intervention Trial, the Helsinki Heart Study and the Diabetes Atherosclerosis Intervention Study, have demonstrated the beneficial effects of synthetic agonists of PPAR-alpha, specifically fibric acid derivatives, on cardiovascular disease outcome. Although fibric acid trials have reported cardiovascular risk reduction in patients with dyslipidemia, the favorable alterations in plasma lipids can only partially explain the reduction in cardiovascular events in these studies. One common link among these trials was a cohort with a high prevalence of insulin resistance or diabetes, conditions associated with heightened systemic inflammation and increased risk for development and progression of atherosclerosis. In this paper, we will review the many antiatherogenic effects of PPAR-alpha ligands and evidence from fibric acid trials that individuals with insulin resistance or diabetes benefit the most from these drugs, consistent with their anti-inflammatory and antithrombotic properties.
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PMID:Peroxisome proliferator-activated receptor-alpha and atherosclerosis: from basic mechanisms to clinical implications. 1552 94

Members of the nuclear receptor gene family act as biological rheostats to maintain metabolic homeostasis in response to endocrine and nutritional changes. The liver X (LXR) and thyroid hormone (TR) receptors have been shown to regulate overlapping but distinct metabolic pathways important for overall lipid homeostasis. Dyslipidemia is one out of four key determinants for cardiovascular risk and both LXRs and TRs may provide attractive targets for intervention of cardiovascular disease. In this review we will compare the two receptor systems to highlight similarities and differences in structure and function with implications for development of novel treatments for dyslipidemia and atherosclerosis.
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PMID:Convergence of lipid homeostasis through liver X and thyroid hormone receptors. 1554 66

Peroxisome proliferator activated receptors (PPARs) are transcriptional factors belonging to the ligand-activated nuclear receptor superfamily. They are ubiquitously expressed throughout the body. On activation by endogenously secreted prostaglandins and fatty acids, they initiate transcription of an array of genes that are involved in energy homeostasis. So far, three major types have been identified, namely PPAR-alpha, PPAR-beta/delta and PPAR-gamma. PPAR-alpha and PPAR-gamma are crucial for lipid and glucose metabolism, respectively. Although limited information is available on PPAR-beta biological functions, recent studies have shown that PPAR-beta also regulates glucose metabolism and fatty acid oxidation. The discovery of PPAR-alpha agonists such as fibrates and PPAR-gamma agonists such as thiozolidinediones enables recognition of the mechanisms involved in ameliorating the adverse effects of chronic disorders such as atherosclerosis and diabetes. In addition, PPARs are also involved in the regulation of various types of tumours, inflammation, cardiovascular diseases and infertility. The importance of these transcription factors in physiology and pathophysiology has instigated much research in this field. In this article, structural features of PPARs, their gene transcription mechanisms and recent developments in the discovery of their biological functions are reviewed.
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PMID:An overview on biological mechanisms of PPARs. 1562 53

Nuclear receptors are ligand-dependent transcription factors that recently have been shown to play important roles in the metabolism of cholesterol and bile acids. Cholesterol homeostasis is maintained by de novo synthesis, absorption from diet, catabolism to bile acids and other steroids, and excretion into bile. Dysregulation of this mechanism leads to atherosclerosis and its life-threatening coronary and cerebrovascular sequelae. Conversion of cholesterol to bile acids in the liver is positively regulated by liver X receptor (LXR) alpha, a nuclear receptor for oxysterols. LXRalpha and LXRbeta, a second oxysterol receptor, regulate intestinal absorption and biliary excretion of cholesterol by inducing target gene expression. LXRs stimulate reverse cholesterol transport from peripheral tissues and exhibit antiatherogenic activity. Farnesoid X receptor (FXR), a bile acid receptor, represses bile acid synthesis and import in hepatocytes, stimulates bile acid export from cells, and protects hepatocytes from bile acid toxicity. Pregnane X receptor (PXR) and vitamin D receptor (VDR) respond to secondary bile acids and induce their catabolism. Thus, nuclear receptors play important roles in regulation of cholesterol and bile acid metabolism.
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PMID:Nuclear receptors as targets for drug development: regulation of cholesterol and bile acid metabolism by nuclear receptors. 1572 1

Peroxisome proliferator-activated receptor alpha (PPARalpha) is the nuclear receptor responsible for regulating genes that control lipid homeostasis. Because of this role, PPARalpha has become a target of interest for the development of drugs to treat diseases such as dyslipidemia, obesity, and atherosclerosis. Assays currently employed to determine potency and efficacy of potential drug candidates typically utilize a truncated form of the native receptor, one which lacks the entire N-terminal region of the protein. The amino terminus, containing the regions that encode the ligand-independent activation function AF-1 and DNA binding domains, is highly structured and contributes significantly to the overall tertiary structure of the native protein. We report that differences in PPARalpha full-length and ligand binding domain constructs result in differences in binding affinity for coactivator peptides but have little effect on potency of agonists in both cell-free and cell-based nuclear receptor assays.
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PMID:Comparison of full-length versus ligand binding domain constructs in cell-free and cell-based peroxisome proliferator-activated receptor alpha assays. 1576 18

Peroxisome proliferator-activated receptors (PPARs) are transcription factors belonging to the nuclear receptor superfamily. PPARs have three isoforms, alpha, beta (or delta) and gamma. It has been conceived that PPARgamma is expressed predominantly in adipose tissue and promotes adipocyte differentiation and glucose homeostasis. Recently, synthetic antidiabetic thiazolidinediones and natural prostaglandin D2 (PGD2) metabolite, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), have been identified as ligands for PPARgamma. Following demonstration that PPARgamma is present in a variety of cell types, further study of PPARgamma has been conducted. Although activation of PPARgamma appears to have beneficial effects on atherosclerosis and heart failure, it is still largely uncertain whether PPARgamma ligands prevent the development of cardiovascular diseases. Recent evidence suggests that some benefit from the antidiabetic agents known as thiazolidinediones may occur through PPARgamma-independent mechanisms. In this review, we report on the latest developments concerning the study of PPARs and summarize the roles of the PPARgamma-dependent pathway in cardiovascular diseases.
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PMID:The role of PPARgamma-dependent pathway in the development of cardiac hypertrophy. 1583 32

Hypertension commonly occurs as part of a genetically complex disorder of carbohydrate and lipid metabolism known as the metabolic syndrome. Most current antihypertensive drugs appear ineffective against the metabolic syndrome, which is a strong predictor of cardiovascular disease and death in affected patients. Angiotensin II can influence the activity of certain genes and cellular and biochemical pathways that may contribute to the pathogenesis of the metabolic syndrome. However, as a class, angiotensin II receptor blockers (ARBs) have proven only minimally to modestly effective in ameliorating the disturbances in carbohydrate and lipid metabolism that characterise the metabolic syndrome. Recent preclinical studies indicate that the ARB telmisartan acts as a selective peroxisome proliferators-activated receptor-gamma (PPARgamma) modulator when tested at concentrations that might be achievable with oral doses recommended for treatment of hypertension; this property does not appear to be shared by other ARBs. PPARgamma is a nuclear receptor that influences the expression of multiple genes involved in carbohydrate and lipid metabolism and is an attractive therapeutic target for the prevention and control of insulin resistance, type 2 diabetes and atherosclerosis. In cellular transactivation assays, telmisartan functioned as a partial agonist of PPARgamma and achieved 25-30% of maximal receptor activation attained with conventional PPARgamma ligands. Preclinical and clinical studies indicate that administration of telmisartan can improve carbohydrate and lipid metabolism without causing the side effects that accompany full PPARgamma activators. If the preliminary data are supported by the results of ongoing large-scale clinical studies, telmisartan could have a central role in the prevention and treatment of metabolic syndrome, diabetes and atherosclerosis.
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PMID:Treating the metabolic syndrome: telmisartan as a peroxisome proliferator-activated receptor-gamma activator. 1586 21

Fibrinogen is a plasma protein synthesized by the liver. It is composed of three chains (alpha, beta, gamma). In addition to its main function as a coagulation factor, this acute phase protein is also a risk marker for atherosclerosis. Retinoic acid receptor-related orphan receptor (ROR)alpha is a nuclear receptor modulating physiopathological processes such as cerebellar ataxia, inflammation, atherosclerosis, and angiogenesis. In this study, we identified RORalpha as a regulator of fibrinogen-beta gene expression in human hepatoma cells and in mouse liver. A putative RORalpha response element (RORE) was identified in the human fibrinogen-beta promoter. EMSA showed that RORalpha binds specifically to this RORE, and cotransfection experiments in HepG2 hepatoma cells indicated that this RORE confers RORalpha-dependent transcriptional activation to both the human fibrinogen-beta and the thymidine kinase promoters. Stable transfection experiments in HepG2 and Hep3B hepatoma cells demonstrated that overexpression of RORalpha specifically increases endogenous fibrinogen-beta mRNA levels. Chromatin immunoprecipitation experiments revealed that the fibrinogen-beta RORE is occupied by RORalpha in HepG2 cells. Thus, the human fibrinogen-beta gene is a direct target for RORalpha. Furthermore, fibrinogen-beta mRNA levels in liver and plasma fibrinogen concentrations are specifically decreased in staggerer mice, which are homozygous for a deletion invalidating the Rora gene. Taken together, these data add further evidence for an important role of RORalpha in the control of liver gene expression with potential pathophysiological consequences on coagulation and cardiovascular risk.
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PMID:The gene encoding fibrinogen-beta is a target for retinoic acid receptor-related orphan receptor alpha. 1594 50

Atherosclerosis is a vascular disease, appearing early in life, and developing gradually and progressively, from the initial local inflammatory lesions, a stage at which endothelial dysfunction is already present, to the ultimate stage, culminating in atherosclerotic plaque rupture followed by thrombogenesis. Glitazones, specific agonists for the nuclear receptor PPARgamma, act at each stage of the atherogenesis process, and therefore are likely to convey cardioprotective activities in type 2 diabetic patients as well as in non-diabetic patients at high cardiovascular risk (glucose intolerant subjects with or without associated metabolic syndrome). In this review, we summarize the main stages of atherosclerosis progression and their pathophysiological mechanisms, and the results of studies carried out with glitazones, either in in vitro experimental models or in vivo in various animal models, as well as results of recent studies in type 2 diabetic patients, which support the concept for a cardioprotective action of glitazones.
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PMID:[Glitazones and atherosclerosis]. 1595 2

Numerous mechanisms contribute to impaired arterial wall in insulin resistant subjects and in type 2 diabetic patients. Endothelial dysfunction appears at an early stage of atherosclerosis progression, an accelerated process in diabetic patients. At a more advanced stage, arterial stiffness and thickening contribute to development of macroangiopathies. Inflammation plays a key role in these phenomena, particularly through growth factors and cytokines secretion in arterial wall cells. Thiazolidinediones, are pharmacological ligands of nuclear receptor PPARgamma and appear to act favorably on several pathophysiological mechanisms involved in these vascular dysfunctions and complications. Thiazolidinediones decrease plasma levels of C reactive protein, possess antiinflammatory effects through a reduction of inflammatory cytokines production, decrease free fatty acids levels, antagonize angiotensin II effects, increase adiponectin expression and production, etc. Pathophysiological mechanisms leading to vascular function impairment and their evaluation techniques are described, as well as the main thiazolidinediones beneficial effects on these mechanisms, which may lead to vascular prevention and/or protection in high cardiovascular risk insulin resistant and/or type 2 diabetic patients.
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PMID:[Arterial wall and glitazones]. 1595 8


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