Absence of Acute Inhibitory Effect of Insulin on Chylomicron Production in Type 2 Diabetes.
Arterioscler Thromb Vasc Biol. 2012 Feb 2;
Authors: Nogueira JP, Maraninchi M, Béliard S, Padilla N, Duvillard L, Mancini J, Nicolay A, Xiao C, Vialettes B, Lewis GF, Valéro R
Abstract
OBJECTIVE: Overproduction of intestinally derived apoB-48-containing triglyceride-rich lipoproteins (TRLs) (chylomicrons) has recently been described in type 2 diabetes, as is known for hepatic TRL-apoB-100 (very-low-density lipoprotein) production. Furthermore, insulin acutely inhibits both intestinal and hepatic TRL production, whereas this acute inhibitory effect on very-low-density lipoprotein production is blunted in type 2 diabetes. It is not currently known whether this acute effect on chylomicron production is similarly blunted in humans with type 2 diabetes. METHODS AND RESULTS: We investigated the effect of acute hyperinsulinemia on TRL metabolism in 18 type 2 diabetic men using stable isotope methodology. Each subject underwent 1 control (saline infusion [SAL]) lipoprotein turnover study followed by a second study, under 1 of the 3 following clamp conditions: (1) hyperinsulinemic-euglycemic, (2) hyperinsulinemic-hyperglycemic, or (3) hyperinsulinemic-euglycemic plus intralipid and heparin. TRL-apoB-48 and TRL-apoB-100 production and clearance rates were not different between SAL and clamp and between the different clamp conditions, except for significantly lower TRL-apoB-100 clearance and production rates in hyperinsulinemic-euglycemic plus intralipid and heparin clamp compared with SAL. CONCLUSIONS: This is the first demonstration in individuals with type 2 diabetes that chylomicron production is resistant to the normal acute suppressive effect of insulin. This phenomenon may contribute to the highly prevalent dyslipidemia of type 2 diabetes and potentially to atherosclerosis.Clinical Trial Registration-URL: www.clinicaltrials.gov. Unique identifier: NCT00950209.
PMID: 22308041 [PubMed - as supplied by publisher]
Intravascular Optical Coherence Tomography Detection of Atherosclerosis and Inflammation in Murine Aorta.
Arterioscler Thromb Vasc Biol. 2012 Feb 2;
Authors: Tahara S, Morooka T, Wang Z, Bezerra HG, Rollins AM, Simon DI, Costa MA
Abstract
OBJECTIVE: The goal of this study was to evaluate the feasibility of imaging the aorta of apolipoprotein E-deficient (ApoE(-/-)) mice for the detection of atherosclerosis and macrophages using optical coherence tomography (OCT) compared with histology. METHODS AND RESULTS: Atherosclerosis was induced by high-fat diet in 7-week-old ApoE(-/-) mice for 10 (n=7) and 22 (n=7) weeks. Nine-week-old ApoE(-/-) mice (n=7) fed a standard chow diet were used as controls. OCT images of a 10-mm descending aorta in situ were performed in 4 mice for each, and plaque and macrophages were determined at 0.5-mm intervals. Automated detection and quantification of macrophages were performed independently using a customized algorithm. Coregistered histological cross-sections were stained with hematoxylin-eosin, Mac-3, and von Kossa. Three mice in each group had en face OCT imaging to detect macrophages, which were compared with lipid-positive area with Sudan IV. OCT images were successfully acquired in all mice. OCT and histology were able to discriminate macrophages and plaque among the 3 groups and showed excellent correlation for (1) visual detection of plaque (r=0.98) and macrophages (r=0.93), (2) automated detection and quantification of macrophages by OCT versus Mac-3-positive area (r=0.92), and (3) en face OCT detection of macrophages versus Sudan IV-positive area (r=0.92). CONCLUSIONS: Murine intraaortic OCT is feasible and shows excellent correlation with histology for detection of atherosclerotic plaque and macrophages.
PMID: 22308042 [PubMed - as supplied by publisher]
In Vivo Targeting of Inflammation-Associated Myeloid-Related Protein 8/14 Via Gadolinium Immunonanoparticles.
Arterioscler Thromb Vasc Biol. 2012 Feb 2;
Authors: Maiseyeu A, Badgeley MA, Kampfrath T, Mihai G, Deiuliis JA, Liu C, Sun Q, Parthasarathy S, Simon DI, Croce K, Rajagopalan S
Abstract
OBJECTIVE: Myeloid-related protein (Mrp) 8/14 complex (is a highly expressed extra cellularly secreted protein, implicated in atherosclerosis. In this study, we evaluated the feasibility of targeting Mrp in vivo through synthetic immuno-nanoprobes. METHODS AND RESULTS: Anti-Mrp-14 and nonspecific IgG-conjugated gadolinium nanoprobes (aMrp-) were synthesized and characterized. Pharmacokinetics and vascular targeting via MRI of the formulations were assessed in vivo in high fat-fed apolipoprotein E deficient (ApoE(-/-)), ApoE(-/-)/Mrp14(-/-) (double knockout) and chow-fed wild-type (C57BL/6) mice were. Bone marrow-derived myeloid progenitor cells were isolated from both ApoE(-/-) and double knockout mice and differentiated to macrophages and were treated with LPS, with or without Mrp8, Mrp14, or Mrp8/14, and conditioned media was collected and used for in vitro studies. Mrp-activated cells secreted significant amounts of proinflammatory cytokines, which were abolished by pretreatment with aMrp-NP. We show in vitro that aMrp-NP binds endothelial cells previously treated with conditioned media containing Mrp8/14. MRI following intravenous delivery of aMrp-NP revealed prolonged and substantial delineation of plaque in ApoE(-/-) but not double knockout or wild-type animals. Nonspecific IgG-conjugated gadolinium nanoprobe-injected animals in all groups did not show vessel wall enhancement. Flow-cytometric analysis of aortic digesta revealed aMrp-NP presence in Ly-6G(+), CD11b(+), CD11c(+), and CD31(+) cells in ApoE(-/-) but not in double knockout animals. CONCLUSIONS: Targeted imaging with aMrp-NP demonstrates enhancement of plaque with binding to inflammatory cells and reduction in inflammation. This strategy has promise as a theranostic approach for atherosclerosis.
PMID: 22308043 [PubMed - as supplied by publisher]
Sphingosine-1-Phosphate Receptor 3 Promotes Neointimal Hyperplasia in Mouse Iliac-Femoral Arteries.
Arterioscler Thromb Vasc Biol. 2012 Feb 2;
Authors: Shimizu T, De Wispelaere A, Winkler M, D’Souza T, Caylor J, Chen L, Dastvan F, Deou J, Cho A, Larena-Avellaneda A, Reidy M, Daum G
Abstract
OBJECTIVE: The objective of this study was to define a role for sphingosine-1-phosphate receptor 3 (S1PR3) in intimal hyperplasia. METHODS AND RESULTS: A denudation model of the iliac-femoral artery in wild-type and S1PR3-null mice was used to define a role for S1PR3 in the arterial injury response because we found in humans and mice that expression of S1PR3 was higher in these arteries compared with carotid arteries. At 28 days after surgery, wild-type arteries formed significantly larger lesions than S1PR3-null arteries.T Bromodeoxyuridine labeling experiments demonstrated that on injury, wild-type arteries exhibited higher medial as well as intimal proliferation than S1PR3-null arteries. Because S1PR3 expression in vitro was low, we expressed S1PR3 in S1PR3-null smooth muscle cells (SMCs) using retroviral-mediated gene transfer to study the effects of S1PR3 on cell functions and signaling. SMCs expressing S1PR3, but not vector-transfected controls, responded to sphingosine-1-phosphate stimulation with activation of Rac, Erk, and Akt. SMCs expressing S1PR3 also migrated more. CONCLUSIONS: In humans and mice, S1PR3 expression was higher in iliac-femoral arteries compared with carotid arteries. S1PR3 promoted neointimal hyperplasia on denudation of iliac-femoral arteries in mice, likely by stimulating cell migration and proliferation through activation of signaling pathways involving Erk, Akt, and Rac.
PMID: 22308044 [PubMed - as supplied by publisher]
TGF-β1 Downregulates AT1 Receptor Expression via PKC-δ-Mediated Sp1 Dissociation From KLF4 and Smad-Mediated PPAR-γ Association with KLF4.
Arterioscler Thromb Vasc Biol. 2012 Jan 26;
Authors: Zhang XH, Zheng B, Gu C, Fu JR, Wen JK
Abstract
OBJECTIVE: Cardiovascular effects of angiotensin II are primarily mediated via the angiotensin II type 1 receptor (AT1R). Krüppel-like factor 4 (KLF4), a transcription factor that binds to the transforming growth factor (TGF)-β control element (TCE), regulates a variety of receptor expression in vascular smooth muscle cells. In the present study, we investigated the mechanisms of TGF-β-mediated KLF4 regulation of AT1R expression. METHODS AND RESULTS: Coimmunoprecipitation, chromatin immunoprecipitation, and luciferase assays were performed, with the results suggesting that Sp1 forms a complex with KLF4 bound to the TCE of the AT1R promoter and cooperatively activates AT1R transcription in vascular smooth muscle cells under basal conditions. On activation of TGF-β1 signaling, Sp1 is dissociated from the KLF4-Sp1 complex through PKC-δ-mediated KLF4 phosphorylation at Thr401, downregulating AT1R expression. Simultaneously, TGF-β1 facilitates KLF4-PPAR-γ complex formation and its binding to the TCE of the AT1R promoter through Smad-mediated KLF4 phosphorylation at Ser470, subsequently leading to inhibition of AT1R transcription. CONCLUSIONS: KLF4 functions as a protein platform that is able to bind to the TCE of the AT1R promoter. On activation of TGF-β signaling, KLF4 mediates Sp1 dissociation from, and PPAR-γ association with, the AT1R promoter, leading to downregulation of AT1R expression in VSMCs.
PMID: 22282354 [PubMed - as supplied by publisher]
OBJECTIVE: We investigated the stability, pharmacokinetic, and pharmacodynamic profile of the 2(nd) generation anti-von Willeband factor aptamer ARC15105. METHODS AND RESULTS: Platelet plug formation was measured by collagen/adenosine diphosphate-induced closure time with the platelet function analyzer-100 and platelet aggregation by multiple electrode aggregometry. Platelet adhesion was measured on denuded porcine aortas and in a flow chamber. Aptamer stability was assessed by incubation in nuclease rich human, monkey, and rat serum for up to 72 hours. Pharmacokinetic and pharmacodynamic profiles were tested in cynomolgus monkeys after IV and SC administration. The median IC(100) and IC(50) to prolong collagen/adenosine diphosphate-induced closure timewere 27 nmol/L and 12 nmol/L, respectively. ARC15105 (1.3 μmol/L) completely inhibited ristocetin-induced platelet aggregation in whole blood (P<0.001), but also diminished collagen, ADP, arachidonic acid, and thrombin receptor activating peptide-induced platelet aggregation to some extent (P<0.05). ARC15105 (40 nmol/L) decreased platelet adhesion by >90% on denuded porcine aortas (P<0.001), which was comparable to the degree of inhibition obtained with abciximab. ARC15105 (100 nmol/L) also inhibited platelet adhesion to collagen under arterial shear in a flow chamber by >90% (P<0.001). The IV and SC terminal half-lives in cynomolgus monkeys were 67 and 65 hours, respectively, and the SC bioavailability was ≈98%. Allometric scaling estimates the human T(1/2) would be ≈217 hours. Pharmacodynamic analysis confirms that ARC15105 inhibits von Willeband factor activity >90% in blood samples taken 300 hours after a 20 mg/kg IV or SC dose in monkeys. CONCLUSIONS: The potency, pharmacokinetic profile, and SC bioavailability of ARC15105 support its clinical investigation for chronic inhibition of von Willeband factor -mediated platelet activation.
PMID: 22282355 [PubMed - as supplied by publisher]
Flow Cytometric Identification and Functional Characterization of Immature and Mature Circulating Endothelial Cells.
Arterioscler Thromb Vasc Biol. 2012 Jan 26;
Authors: Mund JA, Estes ML, Yoder MC, Ingram DA, Case J
Abstract
OBJECTIVE: We sought to identify and characterize 2 distinct populations of bona fide circulating endothelial cells, including the endothelial colony-forming cell (ECFC), by polychromatic flow cytometry (PFC), colony assays, immunomagnetic selection, and electron microscopy. METHODS AND RESULTS: Mononuclear cells from human umbilical cord blood and peripheral blood were analyzed using our recently published PFC protocol. A population of cells containing both ECFCs and mature circulating endothelial cells was determined by varying expressions of CD34, CD31, and CD146 but not AC133 and CD45. After immunomagnetic separation, these cells failed to form hematopoietic colonies, yet clonogenic endothelial colonies with proliferative potential were obtained, thus verifying their identity as ECFCs. The frequency of ECFCs were increased in cord blood and were extremely rare in the peripheral blood of healthy adults. We also detected another mature endothelial cell population in the circulation that was apoptotic. Finally, when comparing this new protocol with a prior method, we determined that the present protocol identifies circulating endothelial cells, whereas the earlier protocol identified extracellular vesicles. CONCLUSIONS: Two populations of circulating endothelial cells, including the functionally characterized ECFC, are now identifiable in human cord blood and peripheral blood by PFC.
PMID: 22282356 [PubMed - as supplied by publisher]
Design and Validation of a Specific Scavenger Receptor Class AI Binding Peptide for Targeting the Inflammatory Atherosclerotic Plaque.
Arterioscler Thromb Vasc Biol. 2012 Jan 26;
Authors: Segers FM, Yu H, Molenaar TJ, Prince P, Tanaka T, van Berkel TJ, Biessen EA
Abstract
OBJECTIVE: Scavenger receptor A (SR-A) is abundantly expressed by macrophage and plays a critical role in foam cell formation and atherogenesis. In search of selective SR-AI antagonists, we have used affinity selection of a phage displayed peptide library on the synthetic extracellular domain of SR-AI. METHODS AND RESULTS: Phage selection led to an almost 1,000-fold enrichment of SR-AI binding phage, which bound avidly to human THP-1. A 15-mer corresponding to the peptide insert of the major SR-AI binding phage (PP1) displaced phage binding to SR-AI. Peptides, docked to a streptavidin scaffold, were effectively internalized by macrophages in an SR-AI-dependent manner. The enriched phage pool and streptavidin bound PP1 exhibited marked uptake by hepatic macrophages in mice. Importantly, PP1 significantly increased streptavidin as well as particulate accumulation in advanced aortic plaques, and in particular intraplaque macrophage, of apolipoprotein E(-/-) mice. CONCLUSIONS: We have identified a novel peptide antagonist selective for SR-AI; this antagonist could be a valuable tool in SR-AI targeted imaging of atherosclerotic lesions.
PMID: 22282357 [PubMed - as supplied by publisher]
HNF4α Increases Liver-Specific Human ATP-Binding Cassette Transporter A1 Expression and Cholesterol Efflux to Apolipoprotein A-I in Response to Cholesterol Depletion.
Arterioscler Thromb Vasc Biol. 2012 Jan 26;
Authors: Ohoka N, Okuhira K, Cui H, Wu W, Sato R, Naito M, Nishimaki-Mogami T
Abstract
OBJECTIVE: Hepatic ATP-binding cassette transporter A1 (ABCA1) plays the major role in maintaining plasma high-density lipoprotein levels by producing cholesterol-accepting nascent high-density lipoprotein, whereas peripheral ABCA1 is responsible for releasing cellular cholesterol. We previously reported that in rodents, cholesterol depletion reduces ABCA1 expression in peripheral but not hepatic cells by increasing a liver-specific ABCA1 transcript via the sterol regulatory element-binding protein-2 system. However, the regulatory element is not conserved in humans. Here we investigated the mechanism of sterol-regulated human hepatic ABCA1 gene expression. METHODS AND RESULTS: ABCA1 mRNA variant type L3 is a novel and human-liver-specific transcript accounting for ≈25% of total ABCA1 mRNA in the liver and is induced by cellular cholesterol depletion. Specific knockdown or forced expression revealed that type L3 produces functional ABCA1 protein in cholesterol efflux. We identified a regulatory enhancer element for L3 expression lying within intron 3 of the human ABCA1 gene, to which HNF4α binds in response to cholesterol depletion. HNF4α knockdown abolished induction of liver-specific L3 and L2b transcripts (and consequently the liver-type response of ABCA1 expression to cellular cholesterol status) and diminished cholesterol efflux activity. CONCLUSIONS: These findings indicate that HNF4α regulates human hepatic ABCA1 expression in response to cholesterol depletion.
PMID: 22282358 [PubMed - as supplied by publisher]
Sympathetic Nervous System Regulates Bone Marrow-Derived Cell Egress Through Endothelial Nitric Oxide Synthase Activation: Role in Postischemic Tissue Remodeling.
Arterioscler Thromb Vasc Biol. 2012 Jan 19;
Authors: Récalde A, Richart A, Guérin C, Cochain C, Zouggari Y, Yin KH, Vilar J, Drouet I, Lévy B, Varoquaux O, Silvestre JS
Abstract
OBJECTIVE: Catecholamines have been shown to control bone marrow (BM)-derived cell egress, yet the cellular and molecular mechanisms involved in this effect and their subsequent participation to postischemic vessel growth are poorly understood. METHODS AND RESULTS: Tyrosine hydroxylase mRNA levels, as well as dopamine (DA) and norepinephrine (NE) contents, were increased in the ischemic BM of mice with right femoral artery ligation. Angiographic score, capillary density, and arteriole number were markedly increased by treatments with DA (IP, 50 mg/kg, 5 days) or NE (IP, 2.5 mg/kg, 5 days). Using chimeric mice lethally irradiated and transplanted with BM-derived cells from green fluorescent protein mice, we showed that DA and NE enhanced by 70% (P<0.01) and 62% (P<0.001), respectively, the number of green fluorescent protein-positive BM-derived cells in ischemic tissue and promoted their ability to differentiate into cells with endothelial and inflammatory phenotypes. Similarly, both DA and NE increased the in vitro differentiation of cultured BM-derived cells into cells with endothelial phenotype. This increase was blunted by the nitric oxide synthase inhibitor N(ω)-nitro-l-arginine methyl ester. DA and NE also upregulated the number of CD45-positive cells in blood 3 days after ischemia and that of macrophages in ischemic tissue 21 days after ischemia. Of interest, DA and NE increased BM endothelial nitric oxide synthase (eNOS) mRNA levels and were unable to promote BM-derived cell mobilization in chimeric eNOS-deficient mice lethally irradiated and transplanted with BM-derived cells from wild-type animals. Furthermore, administration of a β2 adrenergic agonist (clenbuterol, IP, 2 mg/kg, 5 days) and that of a dopaminergic D1/D5 receptor agonist (SKF-38393, IP, 2.5 mg/kg, 5 days) also enhanced BM-derived cell mobilization and subsequently postischemic vessel growth. CONCLUSIONS: These results unravel, for the first time, a major role for the sympathetic nervous system in BM-derived cell egress through stromal eNOS activation.
PMID: 22267478 [PubMed - as supplied by publisher]
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