Physiological and pathological roles of a multi-ligand receptor CD36 in atherogenesis; insights from CD36-deficient patients
Department of Internal Medicine and Molecular Science, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. Molecular and Cellular Biochemistry
(Impact Factor: 2.39).
06/2007; 299(1-2):19-22. DOI: 10.1007/s11010-005-9031-4
Oxidized low density lipoprotein (LDL) (Ox-LDL) plays an important role in the pathogenesis of atherosclerosis. Oxidized LDL is taken up by macrophages via scavenger receptors. CD36 is an 88 kDa glycoprotein expressed on platelets, monocyte-macrophages, microvascular endothelial cells, adipose tissue, skeletal muscles and heart. We found patients with CD36 deficiency and identified several mutations in the CD36 gene. We also reported that CD36-deficient macrophages showed a 50% reduction in the binding of Ox-LDL, suggesting that CD36 is one of the major receptors for Ox-LDL. CD36 was expressed on macrophages in the atherosclerotic lesions of human aorta and coronary arteries especially on foamed macrophages. The distribution of CD36 expression was slightly different from that of scavenger receptor class A types I and II. The expression of CD36 on macrophages was up-regulated by Ox-LDL and down-regulated by interferon gamma. Since CD36 is a transporter of long-chain fatty acids (LCFA), CD36-deficient patients showed a defect in the uptake of an LCFA analog, BMIPP, by the heart. Furthermore, the secretion of IL-1beta and TNF-alpha from monocyte-derived macrophages induced by Ox-LDL was markedly reduced and the activation of NF-kappaB was attenuated in CD36-deficient subjects compared with controls, suggesting that CD36-mediated signaling is also impaired in CD36 deficiency. To elucidate the roles of CD36 in vivo, we characterized the clinical profile of CD36-deficient patients. Most of them were accompanied by hyperlipidemia (mainly hypertriglyceridemia), increased remnant lipoproteins and mild elevation of fasting plasma glucose level and blood pressure. Glucose clamp technique revealed mean whole body glucose uptake was reduced in CD36-deficient patients, indicating the presence of insulin resistance. The frequency of CD36 deficiency was higher in patients with coronary heart disease (CHD) than in control subjects. Taken together, CD36 deficiency is accompanied by (1) hyperlipidemia and increased remnant lipoproteins, (2) impaired glucose metabolism based upon insulin resistance, and (3) mild hypertension, and comprises one of the genetic backgrounds of the metabolic syndrome, leading to the development of CHD.
Available from: PubMed Central
- "OxLDL via CD36 induces the activation of other mitogen-activated kinases such as p38 mitogen-activated kinase and ERK 1/2.38 Signaling mediated by CD36 activates nuclear factor kappa beta. CD36-deficient macrophages have reduced nuclear factor kappa beta activation and reduced the release of interleukin (IL)-1β and tumor necrosis factor-α.39 "
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ABSTRACT: CD36 is a membrane glycoprotein that is present on various types of cells, including monocytes, macrophages, microvascular endothelial cells, adipocytes and platelets. Macrophage CD36 participates in atherosclerotic arterial lesion formation through its interaction with oxidized low-density lipoprotein (oxLDL), which triggers signaling cascades for inflammatory responses. CD36 functions in oxLDL uptake and foam cell formation, which is the initial critical stage of atherosclerosis. In addition, oxLDL via CD36 inhibits macrophage migration, which may be a macrophage-trapping mechanism in atherosclerotic lesions. The role of CD36 was examined in in vitro studies and in vivo experiments, which investigated various functions of CD36 in atherosclerosis and revealed that CD36 deficiency reduces atherosclerotic lesion formation. Platelet CD36 also promotes atherosclerotic inflammatory processes and is involved in thrombus formation after atherosclerotic plaque rupture. Because CD36 is an essential component of atherosclerosis, defining the function of CD36 and its corresponding signaling pathway may lead to a new treatment strategy for atherosclerosis.
Available from: Tsuyoshi Goto
- "Therefore, PPAR activation is considered to be valuable for prevention and improvement of metabolic syndrome. High serum lipid levels under fasting conditions have been considered a risk of cardiovascular diseases . Many studies have revealed that serum lipid levels under postprandial conditions, rather than under fasting conditions, strongly correlate with the risk of cardiovascular diseases . "
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ABSTRACT: Activation of peroxisome proliferator-activated receptor (PPAR)-α which regulates lipid metabolism in peripheral tissues such as the liver and skeletal muscle, decreases circulating lipid levels, thus improving hyperlipidemia under fasting conditions. Recently, postprandial serum lipid levels have been found to correlate more closely to cardiovascular diseases than fasting levels, although fasting hyperlipidemia is considered an important risk of cardiovascular diseases. However, the effect of PPARα activation on postprandial lipidemia has not been clarified. In this study, we examined the effects of PPARα activation in enterocytes on lipid secretion and postprandial lipidemia. In Caco-2 enterocytes, bezafibrate, a potent PPARα agonist, increased mRNA expression levels of fatty acid oxidation-related genes, such as acyl-CoA oxidase, carnitine palmitoyl transferase, and acyl-CoA synthase, and oxygen consumption rate (OCR) and suppressed secretion levels of both triglycerides and apolipoprotein B into the basolateral side. In vivo experiments revealed that feeding high-fat-diet containing bezafibrate increased mRNA expression levels of fatty acid oxidation-related genes and production of CO(2) and acid soluble metabolites in enterocytes. Moreover, bezafibrate treatment suppressed postprandial lipidemia after oral administration of olive oil to the mice. These findings indicate that PPARα activation suppresses postprandial lipidemia through enhancement of fatty acid oxidation in enterocytes, suggesting that intestinal lipid metabolism regulated by PPARα activity is a novel target of PPARα agonist for decreasing circulating levels of lipids under postprandial conditions.
Available from: David D Roberts
- "Mutations resulting in CD36 deficiency occur in humans and some strains of spontaneously hypertensive rats. Humans with CD36 deficiency exhibit hyperlipidemia, increased remnant lipoproteins, impaired glucose metabolism based upon insulin resistance, and mild hypertension . Based on our observation that Aβ impairs the fatty acid translocase activity of CD36, the accumulation of vascular-associated Aβ in Alzheimer's disease could cause a local functional CD36 deficiency by blocking lipid and, potentially, oxidized lipoprotein uptake via this receptor. "
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ABSTRACT: Amyloid-β interacts with two cell surface receptors, CD36 and CD47, through which the matricellular protein thrombospondin-1 inhibits soluble guanylate cyclase activation. Here we examine whether amyloid-β shares this inhibitory activity. Amyloid-β inhibited both drug and nitric oxide-mediated activation of soluble guanylate cyclase in several cell types. Known cGMP-dependent functional responses to nitric oxide in platelets and vascular smooth muscle cells were correspondingly inhibited by amyloid-β. Functional interaction of amyloid-β with the scavenger receptor CD36 was indicated by inhibition of free fatty acid uptake via this receptor. Both soluble oligomer and fibrillar forms of amyloid-β were active. In contrast, amyloid-β did not compete with the known ligand SIRPα for binding to CD47. However, both receptors were necessary for amyloid-β to inhibit cGMP accumulation. These data suggest that amyloid-β interaction with CD36 induces a CD47-dependent signal that inhibits soluble guanylate cyclase activation. Combined with the pleiotropic effects of inhibiting free fatty acid transport via CD36, these data provides a molecular mechanism through which amyloid-β can contribute to the nitric oxide signaling deficiencies associated with Alzheimer's disease.
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