bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of Lipid Deposits Around Aortic Branches of Mice Lacking LDL Receptors and Apolipoprotein E
Authors: McGillicuddy Christopher J. , Carrier Martin J. , Weinberg Peter D.
Published: September 2007

Abstract
—Mice with inactivated genes are increasingly used as models of human atherosclerosis. The aim of the present study was to determine whether the characteristic age-related distributions of lipid deposition seen around human arterial branches are replicated in such mice. Lesions occur downstream of branch ostia in immature human aortas, but these regions are spared in adult vessels, with lesions occurring more frequently at the sides or upstream of the branches. We determined the pattern of lipid staining around 102 intercostal branch ostia from apolipoprotein E/low density lipoprotein receptor double-knockout mice aged 9 to 20 weeks by using en face microscopy and a frequency-mapping technique. Lesion prevalence was high in the ostium and the region immediately surrounding it. Frequencies were 2.12±0.30 (mean±SEM, n=11) times higher upstream than downstream (
P
<0.01), but the pattern did not resemble the adult human pattern: there were no peaks in frequency at the sides or upstream of the branch, and there was no sparing downstream. Furthermore, a patch of sparing upstream of the branch was seen, which has not been reported for human vessels, and there was no trend toward a more upstream pattern with age. We conclude that knockout mice may not be a suitable model in which to investigate localizing factors.
Discrimination of Human Coronary Artery Atherosclerotic Lipid-Rich Lesions by Time-Resolved Laser-Induced Fluorescence Spectroscopy
Authors: Marcu Laura , Fishbein Michael C. , Maarek Jean-Michel I. , Grundfest Warren S.
Published: September 2007

Abstract
—Lesion composition plays a significant role in atherosclerotic lesion instability and rupture. Current clinical techniques cannot fully characterize lesion composition or accurately identify unstable lesions. This study investigates the use of time-resolved fluorescence spectroscopy for unstable atherosclerotic lesion diagnosis. The fluorescence of human coronary artery samples was induced with nitrogen laser and detected in the 360- to 510-nm wavelength range. The samples were sorted into 7 groups according to the AHA classification: normal wall and types I, II
a
(fatty streaks), III (preatheroma), IV (atheroma), V
a
(fibrous), and V
b
(calcified) lesions. Spectral intensities and time-dependent parameters [average lifetime τ
f
; decay constants: τ
1
(fast-term), τ
2
(slow-term), A
1
(fast-term amplitude contribution)] derived from the time-resolved spectra of coronary samples were used for tissue characterization. We determined that a few intensity values at longer wavelengths (>430 nm) and time-dependent parameters at peak emission region (390 nm) discriminate between all types of arterial samples except between normal wall and type I lesions. The lipid-rich lesions (more unstable) can be discriminated from fibrous lesions (more stable) on the basis of time-dependent parameters (lifetime and fast-term decay). We inferred that features of lipid fluorescence are reflected on lipid-rich lesion emission. Our results demonstrate that analysis of the time-resolved spectra may be used to enhance the discrimination between different grades of atherosclerotic lesions and provide a means of discrimination between lipid-rich and fibrous lesions.
Changes in Plasma Triglyceride Levels Shift Lipoprotein(a) Density in Parallel With That of LDL Independently of Apolipoprotein(a) Size
Authors: Nakajima Kei , Hinman Janet , Pfaffinger Ditta , Edelstein Celina , Scanu Angelo M.
Published: September 2007

Abstract
—Lipoprotein(a) [Lp(a)] represents a class of low density lipoprotein (LDL) particles that have as a protein moiety apolipoprotein B-100–linked covalently to a single molecule of apolipoprotein(a) [apo(a)], a specific multikringle protein of the plasminogen family. Lp(a) is polymorphic in density because of either the density heterogeneity of constitutive LDL, apo(a) size, or both. Authentic LDL also represents a set of heterogeneous particles whose density is affected by metabolic events. Whether in vivo these events may also affect Lp(a) density is not clearly established. To this effect, we studied 75 subjects with plasma Lp(a) protein levels between 7 and 50 mg/dL and containing a single apo(a) size isoform. We used density gradient ultracentrifugation to simultaneously monitor the changes in the peak density of LDL and Lp(a) at entry and during the course of treatments directed at reducing plasma triglyceride levels. In each case, we found that at entry, Lp(a) peak density was correlated with LDL peak density (
r
=0.71,
P
<0.0001) and that during treatment, changes in plasma triglycerides were associated with shifts of Lp(a) peak density that paralleled those of LDL peak density. A high correlation (
r
=0.94,
P
<0.0001) was particularly evident in subjects with initial plasma triglycerides in the 300-mg/dL range. In vitro assembly studies showed that an apo(a) isoform containing 14 kringle IV type 2 repeats, exhibited, on incubation with LDL, a comparable degree of incorporation into LDL species varying in density between 1.035 and 1.057 g/mL Taken together, our results indicate that metabolically dependent changes in the peak density of Lp(a) can occur independently of apo(a) size. These changes may have to be taken into account in assessing the cardiovascular pathogenicity of this lipoprotein particle in hypertriglyceridemic subjects.
Do Total and High Density Lipoprotein Cholesterol and Triglycerides Act Independently in the Prediction of Ischemic Heart Disease?
Authors: Yarnell J.W.G. , Patterson C.C. , Sweetnam P.M. , Thomas H.F. , Bainton D. , Elwood P.C. , Bolton C.H. , Miller N.E.
Published: September 2007

Several studies have suggested that men with raised plasma triglycerides (TGs) in combination with adverse levels of other lipids may be at special risk of subsequent ischemic heart disease (IHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein cholesterol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and reexamined them at intervals during a 10-year follow-up. Major IHD events (death from IHD, clinical myocardial infarction, or ECG-defined myocardial infarction) were recorded. Five hundred thirty-three major IHD events occurred. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 3
3
) by the tertiles of TGs, TC, and HDLC. The number of events observed in each group was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confounding variables. The incidence of IHD was 22.6% in the group with the lipid risk factor combination with the highest expected risk (high TGs, high TC, and low HDLC) and 4.7% in the group with the lowest expected risk (
P
<0.01). A comparison of the predicted number of events in the 27 groups with the number of events observed showed that a logistic regression provided an adequate fit without the need to incorporate interactions between lipids in the model. Conclusions are as follows: (1) Serum TGs, TC, and HDLC are independently predictive of IHD at 10 years of follow-up. (2) Combinations of adverse levels of the 3 major lipid risk factors have no greater impact on IHD than that expected from their individual contributions in a logistic regression model. There was no evidence that men with low HDL/raised TGs were at significantly greater risk than that predicted from the independent effects of the 2 lipids considered individually.
ACE Genotype and Endothelium-Dependent Vasodilation of Conduit Arteries and Forearm Microcirculation in Humans
Authors: Arcaro Guido , Solini Anna , Monauni Tiziano , Cretti Anna , Brunato Barbara , Lechi Alessandro , Fellin Renato , Caputo Marco , Cocco Claudio , Bonora Enzo , Muggeo Michele , Bonadonna Riccardo C.
Published: September 2007

The ACE gene is a candidate gene for cardiovascular disease. Endothelial dysfunction is considered an intermediate phenotype in the pathogenesis of hypertension and atherosclerosis. We evaluated the role of ACE gene polymorphism in endothelial function of young healthy humans. We assessed ACE genotype (deletion [D]/insertion [I] polymorphism) in 92 young healthy individuals. In 88 of them, endothelium-dependent (flow-mediated) vasodilation and endothelium-independent (nitroglycerin-induced) vasodilation were measured in the common femoral artery and in the brachial (n=84) artery by echo Doppler technique. In 35 subjects, we also applied the forearm perfusion technique to quantify the responses of the forearm vascular bed to 3 increasing doses of 2 endothelium-dependent vasodilators (acetylcholine and bradykinin) and 1 endothelium-independent vasodilator (sodium nitroprusside). The D allele of the ACE gene was associated with a significant blunting (Δ≈26%) of endothelium-dependent vasodilation in the femoral artery (
P
=0.02) but not in the brachial artery (
P
=0.55) or in the forearm microcirculation (
P
=0.70 to 0.80). Endothelium-independent vasodilation was unaffected by the ACE genotype. In young healthy humans, the D allele of the ACE gene is associated with selective endothelial dysfunction of the femoral artery. It remains to be determined whether this association discloses a causal role in vascular, particularly peripheral artery, disease.
Increased Expression of Heme Oxygenase-1 and Bilirubin Accumulation in Foam Cells of Rabbit Atherosclerotic Lesions
Authors: Nakayama Masaharu , Takahashi Kazuhiro , Komaru Tatsuya , Fukuchi Mitsumasa , Shioiri Hiroki , Sato Ko-ichi , Kitamuro Tomomi , Shirato Kunio , Yamaguchi Tokio , Suematsu Makoto , Shibahara Shigeki
Published: September 2007

Heme oxygenase-1 (HO-1) catalyzes the regiospecific oxidative degradation of heme to biliverdin IXα, iron, and carbon monoxide. Biliverdin IXα is subsequently reduced to bilirubin IXα by biliverdin reductase. HO-1 expression is induced under various disease conditions, including atherosclerosis, but it is unknown whether HO-1 catalyzes heme breakdown in the regions at risk. Using hypercholesterolemic rabbits fed a cholesterol-enriched diet, we attempted to demonstrate the involvement of HO-1 induction and bilirubin IXα production in atherosclerotic regions. Expression levels of HO-1 mRNA were elevated in the aortas of hypercholesterolemic rabbits. In situ hybridization and immunohistochemistry revealed that mRNA and protein of HO-1 are induced in endothelial cells and foam cells (lipid-filled macrophages) in atherosclerotic lesions. Furthermore, immunohistochemistry with the use of an anti-bilirubin-IXα monoclonal antibody, 24G7, demonstrated accumulation of bilirubin IXα in foam cells, indicating that heme is actually degraded in atherosclerotic lesions. Remarkably, bilirubin IXα, like HO-1 protein, is predominantly accumulated in the perinuclear regions of foam cells. These results provide the first in vivo evidence of the colocalization of HO-1 and bilirubin IXα in foam cells, suggesting a role of HO-1 induction in the modulation of macrophage activation in atherosclerosis.
In Vivo Anti-Inflammatory Effect of Statins Is Mediated by Nonsterol Mevalonate Products
Authors: Diomede Luisa , Albani Diego , Sottocorno Marcello , Donati Maria Benedetta , Bianchi Marco , Fruscella Paolo , Salmona Mario
Published: September 2007

This study set out to clarify whether the inhibition of sterol or nonsterol derivatives arising from mevalonate biotransformation plays a major role in the in vivo anti-inflammatory action of statins. Hepatic synthesis of all these derivatives was inhibited in mice by administered statins, whereas squalestatin inhibited only sterol derivatives. Using a short-term treatment schedule, we found that statins reduced the hepatic activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase without affecting blood cholesterol. This treatment inhibited lipopolysaccharide- and carrageenan-induced pouch leukocyte recruitment and the exudate production of interleukin-6, monocyte chemotactic protein-1, and RANTES. Coadministration of mevalonate reversed the effect of statin on leukocyte recruitment. The inhibition of sterol synthesis by squalestatin did not have any anti-inflammatory effect, indicating that the biosynthesis of nonsterol compounds arising from mevalonate is crucial for the in vivo regulation of cytokine and chemokine production by statins. Their inhibition by statins may account for the reported anti-inflammatory effects of these drugs and may provide a biochemical basis for the recently reported effects of statins in the prevention of cardiovascular disease and mortality.
Differential Metabolism of Human VLDL According to Content of ApoE and ApoC-III
Authors: Tomiyasu Koji , Walsh Brian W. , Ikewaki Katsunori , Judge Helena , Sacks Frank M.
Published: September 2007

We studied the metabolism of very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL) particles that did or did not have apolipoprotein E (apoE) in 12 normolipidemic women by endogenously labeling plasma apolipoprotein B. The plasma was separated into bound (E+) and unbound (E−) fractions by use of a monoclonal antibody (1D7), and the fractions were ultracentrifuged to yield E+ and E− subfractions of light and dense VLDL and IDL. VLDL E+ and IDL E+ were produced mainly by the liver. VLDL E+ and IDL E+ had lower fractional catabolic rates and much higher apolipoprotein C-III (apoC-III) content than did the corresponding E− particles. Most light VLDL apoE+ underwent lipolysis to dense VLDL E+ with reduced apoC-III content, which was removed from the circulation without conversion to IDL. In contrast, most light VLDL apoE−, poor in apoC-III, was removed from the circulation, and a smaller proportion underwent lipolysis to dense VLDL E−. Most dense VLDL E− underwent lipolysis to IDL E−. The rate constant for lipolysis of dense VLDL to IDL was greater for E− than for E+, and the rate constant for clearance from plasma was greater for dense VLDL E+ than for E−. In conclusion, metabolism of human VLDL particles is influenced by their content of apoE, further modulated by the coexistence of apoC-III.
LR11, a Mosaic LDL Receptor Family Member, Mediates the Uptake of ApoE-Rich Lipoproteins In Vitro
Authors: Taira Kouichi , Bujo Hideaki , Hirayama Satoshi , Yamazaki Hiroyuki , Kanaki Tatsuro , Takahashi Kazuo , Ishii Itsuko , Miida Takashi , Schneider Wolfgang Johann , Saito Yasushi
Published: September 2007

Since the molecular identification of the low density lipoprotein receptor (LDLR), an ever increasing number of related proteins have been discovered. These receptors belonging to the LDLR family are thought to play key roles in lipoprotein metabolism in a variety of tissues, including the arterial wall. We have discovered that the expression of a 250-kDa mosaic LDLR-related protein, which we termed LR11 for the presence of 11 LDLR ligand–binding repeats, is markedly induced in smooth muscle cells in the hyperplastic intima of animal models used for the study of atherosclerosis. Here, we demonstrate that the human LR11, when overexpressed in hamster cells, binds and internalizes 39-kDa receptor–associated protein (RAP), an in vitro ligand for all receptors belonging to the LDLR family. Furthermore, LR11 binds the apolipoprotein E (apoE)-rich lipoproteins, β-very low density lipoproteins (VLDLs), with a high affinity similar to that of other members, such as the LDLR and VLDL receptor. RAP and β-VLDL compete with each other; however, other serum lipoproteins are not able to inhibit their binding. LR11 shows specific binding of apoE-enriched HDL prepared from human cerebrospinal fluid as well as of β-VLDL, suggesting that the apoE content of lipoproteins is most likely important for mediating the high-affinity binding to the receptor. LR11-overexpressing cells are able to internalize and degrade the bound β-VLDL; these cells also show increased accumulation of cholesteryl esters when incubated with β-VLDL. Incubation for 48 hours with β-VLDL of LR11-overexpressing cells, but not of control cells, promotes the appearance of numerous intracellular lipid droplets. Taken together, LR11, a mosaic LDLR family member whose expression in smooth muscle cells is markedly induced in atheroma, has all the properties of a receptor for the endocytosis of lipoproteins, particularly for the incorporation of apoE-rich lipoproteins.
Postprandial Increase of Complement Component 3 in Normolipidemic Patients With Coronary Artery Disease
Authors: Halkes C.J.M. , van Dijk H. , de Jaegere P.P.T. , Plokker H.W.M. , van der Helm Y. , Erkelens D.W. , Castro Cabezas M.
Published: September 2007

Plasma concentrations of the third complement component (C3) predict the risk of myocardial infarction. Because chylomicrons stimulate C3 production by adipocytes in vitro, we investigated plasma C3 changes in vivo after an oral fat load. Thirty-seven subjects (20 normolipidemic patients with coronary artery disease [CAD] and 17 healthy control subjects) underwent an oral fat load (50 g/m
2
). C3 was measured at baseline and at 2-hour intervals after fat intake for 10 hours. The effects of lipid lowering by simvastatin were evaluated in 16 patients. Fasting plasma C3 was 1.06±0.26 and 0.90±0.12 g/L in CAD patients and control subjects, respectively. Fasting C3 was correlated with several parameters associated with insulin resistance. The best determinant of fasting C3 was waist circumference (adjusted
R
2
=0.48, β=0.71,
P
<0.001); the addition of postprandial triglyceridemia to the model improved it (adjusted
R
2
=0.63). Plasma C3 levels at 2, 4, and 6 hours after fat ingestion were significantly higher than fasting levels in patients and control subjects. C3 increased maximally to 1.39±0.33 g/L in patients and to 1.11±0.18 g/L in control subjects (
P
<0.01 for patients versus control subjects). Total postprandial triglyceridemia was the best determinant of maximal C3 increase (adjusted
R
2
=0.47, β=0.70;
P
<0.001). Treatment with simvastatin decreased fasting and postprandial C3 by 6% and 39%, respectively (
P
<0.05 for both versus no treatment). Postprandial plasma C3 concentrations increase in CAD patients and control subjects. Fasting C3 is associated with waist circumference, but postprandial C3 increment is associated with postprandial lipemia. Fasting and postprandial C3 concentrations decrease after treatment with simvastatin.
Relationship of Clinical Presentation and Calcification of Culprit Coronary Artery Stenoses
Authors: Beckman Joshua A. , Ganz Jason , Creager Mark A. , Ganz Peter , Kinlay Scott
Published: September 2007

Coronary artery calcification is increased in the presence of atherosclerosis. However, there is great variability in the calcification of individual coronary stenoses, and the clinical significance of this finding remains unknown. We tested the hypothesis that culprit lesions associated with myocardial infarction or unstable angina are less calcified than are stenoses associated with stable angina. The study consisted of 78 patients who underwent intravascular ultrasound imaging of culprit stenoses after the placement of a stent. Seventeen patients presented with stable angina; 43, with unstable angina; and 18, with myocardial infarction. The extent of coronary calcification was measured by the angle of its arc and was quantified with a computer-based protractor. The arc of calcium was measured in the stented area at the point of maximal calcification and also as an average of the calcification found at proximal, middle, and distal stent segments. The maximal arc of calcium decreased progressively from patients with stable angina (91±10°) to those with unstable angina (59±8°) and to those with myocardial infarction (49±11°,
P
=0.014). Similarly, the average arc of calcium was greatest (32±7°) in patients with stable angina, less (15±4°) in patients with unstable angina, and least (10±5°) in patients with acute myocardial infarction (
P
=0.014). These associations remained significant after adjustment for other factors that potentially affect arterial calcification. Acute coronary syndromes are associated with a relative lack of calcium in the culprit stenoses compared with stenoses of patients with stable angina. These findings have implications for the understanding of the biology of acute coronary syndromes as well as for the identification of coronary stenoses by methods that rely solely on the presence of calcium.
Variation in Human Platelet Glycoprotein VI Content Modulates Glycoprotein VI–Specific Prothrombinase Activity
Authors: Furihata Kenichi , Clemetson Kenneth J. , Deguchi Hiroshi , Kunicki Thomas J.
Published: September 2007

Glycoprotein VI (GPVI) is a platelet-specific receptor for collagen that figures prominently in signal transduction. An addition to binding to type I and III collagens, GPVI is also bound specifically by collagen-related peptide and convulxin (CVX), a snake venom protein. We developed a quantitative assay of platelet GPVI in which biotin-conjugated CVX binds selectively to GPVI in separated total platelet proteins by a ligand blot procedure. Using this approach, we have documented a 5-fold range in platelet GPVI content among 23 normal healthy subjects. In addition, we have determined that CVX-induced or collagen-related peptide–induced prothrombinase activity is directly proportional to the platelet content of GPVI. A statistically significant correlation was observed at 2 CVX concentrations: 14.7 ng/mL (
R
2
=0.854 and
P
<0.001, n=11) and 22 ng/mL (
R
2
=0.776 and
P
<0.001, n=12). In previous studies, we established a similar range of expression of the integrin collagen receptor α
2
β
1
on platelets of normal subjects. Among 15 donors, there is a direct correlation between platelet α
2
β
1
density and GPVI content (
R
2
=0.475 and
P
=0.004). In view of the well-documented association of GPVI with platelet procoagulant activity, this study suggests that the variation in GPVI content is a potential risk factor that may predispose individuals to hemorrhagic or thromboembolic disorders.
Thrombin Upregulates Tissue Transglutaminase in Endothelial Cells
Authors: Auld Gillian C. , Ritchie Helen , Robbie Linda A. , Booth Nuala A.
Published: September 2007

Abstract—

Atherosclerosis is characterized by thickening of the vessel wall, smooth muscle cell proliferation, macrophage infiltration, and deposition of a fibrin network. Transglutaminases are a family of enzymes catalyzing the formation of stable covalent cross-links between proteins. Here, we show that tissue transglutaminase (tTG) synthesis by human umbilical vein endothelial cells is upregulated by thrombin, the serine protease that causes fibrin formation and many cellular inflammatory effects. Thrombin upregulated tTG 2-fold at the mRNA and protein level. Cellular cross-linking activity was increased to an even greater extent; antibody to tTG neutralized the increased activity. The effect on tTG expression required active thrombin and was mediated mainly through protease-activated receptor-1, a thrombin receptor. Increased tTG antigen and activity were evident in human umbilical vein endothelial cells and extracellular matrix in situ. Thrombin treatment also led to a cellular redistribution of tTG. Normal vessel wall stained positively for tTG in the smooth muscle cells and in the subendothelium. The intensity of staining increased in vessel walls with plaque, where there was a striking increase in tTG in the smooth muscle cells immediately below the plaque. These studies indicate a role for tTG in the stabilization of atherosclerotic plaques and suggest that its local expression can be controlled by thrombin.
Catecholamines Abrogate Antimitogenic Effects of 2-Hydroxyestradiol on Human Aortic Vascular Smooth Muscle Cells
Authors: Zacharia Lefteris C. , Jackson Edwin K. , Gillespie Delbert G. , Dubey Raghvendra K.
Published: September 2007

Catechol-
O
-methyltransferase (COMT)-mediated methylation of 2-hydroxyestradiol (endogenous estradiol metabolite) to 2-methoxyestradiol (angiogenesis inhibitor) may be responsible for the antimitogenic effects of 2-hydroxyestradiol on vascular smooth muscle cells (VSMCs). Catecholamines are also substrates for COMT, and increased levels of catecholamines are associated with vasoocclusive disorders. We hypothesize that catecholamines may abrogate the vasoprotective effects of 2-hydroxyestradiol by competing for COMT and inhibiting 2-methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic effects of 0.001 to 0.1 μmol/L of 2-hydroxyestradiol on human aortic VSMC proliferation (cell number and DNA synthesis), collagen synthesis, and migration in the presence and absence of catecholamines. Norepinephrine, epinephrine, and isoproterenol concentration-dependently abrogated the inhibitory effects of 2-hydroxyestradiol on cell number, DNA synthesis, collagen synthesis, and cell migration. These modulatory/attenuating effects of catecholamines were not abrogated in the presence of the α- and β-adrenergic receptor antagonists, phentolamine mesylate and propranolol, respectively. In contrast to 2-hydroxyestradiol, the antimitogenic effects of 2-methoxyestradiol (0.1 μmol/L) were not attenuated by isoproterenol (1 μmol/L) or quercetin (competitive inhibitor of COMT, 10 μmol/L). Norepinephrine, epinephrine, and isoproterenol concentration-dependently (10 to 500 μmol/L) inhibited the metabolism of 2-hydroxyestradiol (0.25 to 2 μmol/L) to 2-methoxyestradiol, and the potency of the catecholamines to reverse 2-hydroxyestradiol-induced inhibition of VSMC proliferation, collagen synthesis, and migration was correlated with their ability to inhibit 2-methoxyestradiol formation. Our findings suggest that catecholamines within the vasculature may abrogate the anti-vaso-occlusive effects of estradiol and 2-hydroxyestradiol by blocking 2-methoxyestradiol formation.
Osteoprotegerin Inhibits Artery Calcification Induced by Warfarin and by Vitamin D
Authors: Price Paul A. , June Helen H. , Buckley Jessica R. , Williamson Matthew K.
Published: September 2007

The present experiments were carried out to test the hypothesis that arterial calcification is linked to bone resorption by determining whether the selective inhibition of bone resorption with osteoprotegerin will inhibit arterial calcification. In the first test, arterial calcification was induced by treating 22-day-old male rats with warfarin, a procedure that inhibits the γ-carboxylation of matrix Gla protein and causes extensive calcification of the arterial media. Compared with rats treated for 1 week with warfarin alone, rats treated with warfarin plus osteoprotegerin at a dose of 1 mg/kg per day had dramatically reduced alizarin red staining for calcification in the aorta and in the carotid, hepatic, mesenteric, renal, and femoral arteries, and they had 90% lower levels of calcium and phosphate in the abdominal aorta (
P
<0.001) and in tracheal ring cartilage (
P
<0.01). More rapid arterial calcification was induced by treating 49-day-old male rats with toxic doses of vitamin D. Treatment for 96 hours with vitamin D caused widespread alizarin red staining for calcification in the aorta and the femoral, mesenteric, hepatic, renal, and carotid arteries, and osteoprotegerin completely prevented calcification in each of these arteries and reduced the levels of calcium and phosphate in the abdominal aorta to control levels (
P
<0.001). Treatment with vitamin D also caused extensive calcification in the lungs, trachea, kidneys, stomach, and small intestine, and treatment with osteoprotegerin reduced or prevented calcification in each of these sites. Measurement of serum levels of cross-linked N-teleopeptides showed that osteoprotegerin dramatically reduced bone resorption activity in each of these experiments (
P
<0.001). Therefore, we conclude that doses of osteoprotegerin that inhibit bone resorption are able to potently inhibit the calcification of arteries that is induced by warfarin treatment and by vitamin D treatment. These results support the hypothesis that arterial calcification is linked to bone resorption.
Role of Arterial Wall Antioxidant Defense in Beneficial Effects of Exercise on Atherosclerosis in Mice
Authors: Meilhac Olivier , Ramachandran Sumathi , Chiang Kenneth , Santanam Nalini , Parthasarathy Sampath
Published: September 2007

The mechanism(s) by which exercise reduces atherogenic risk remains unknown. This study tested the hypothesis that sustained exercise-induced oxidative stress may increase antioxidant defense in the arterial wall. Acute exercise induced an increase in antibodies to oxidatively modified proteins and catalase in the aortic walls of normal mice compared with sedentary control mice. In male atherogenic diet-fed low density lipoprotein (LDL) receptor-deficient mice, exercise lowered plasma cholesterol (15%) and decreased atherosclerotic lesions by 40% compared with values in sedentary control mice, with a concomitant increase in arterial catalase and endothelial NO synthase. Because these mice lack the LDL receptor, the results indicate that the LDL receptor might not be responsible for the exercise-induced lowering of plasma cholesterol. Vitamin E supplementation to exercising LDL receptor-deficient mice did not reduce atherosclerotic lesion formation significantly as opposed to lesion formation in untreated exercised mice. Moreover, vitamin E counteracted the beneficial effects of exercise by preventing the induction of aortic catalase activity and endothelial NO synthase expression. These results might indicate that although vitamin E might have prevented the exercise-induced oxidative stress, its availability in the artery was insufficient to prevent the atherosclerotic process. These results indicate that exercise-induced plasma oxidative stress could be responsible for the prevention of atherosclerosis by stimulating arterial antioxidant response. Furthermore, vitamin E supplementation could be deleterious in exercisers by inhibiting antioxidant enzyme buildup in the arterial wall.
Effect of Statins on Bone Mineral Density and Bone Histomorphometry in Rodents
Authors: Maritz Frans J. , Conradie Maria M. , Hulley Philippa A. , Gopal Razeen , Hough Stephen
Published: September 2007

Statins have been postulated to affect bone metabolism. We investigated the effects of different doses of simvastatin (1, 5, 10, and 20 mg · kg
−1
· d
−1
), atorvastatin (2.5 mg · kg
−1
· d
−1
), and pravastatin (10 mg · kg
−1
· d
−1
) administered orally for 12 weeks to intact female Sprague-Dawley rats and the effect of 20 mg · kg
−1
· d
−1
simvastatin in sham-operated and ovariectomized rats on femoral bone mineral density (BMD) and quantitative bone histomorphometry (QBH) and compared them with controls. BMD was decreased by 1 mg · kg
−1
· d
−1
simvastatin (
P
=0.042), atorvastatin (
P
=0.0002), and pravastatin (
P
=0.002). The effect on QBH parameters differed with different doses of simvastatin (ANOVA,
P
=0.00012). QBH parameters of both bone formation and resorption were equivalently and markedly increased by 20 mg · kg
−1
· d
−1
simvastatin in 2 separate groups of intact rats and were reflected by a relatively unchanged BMD. At lower doses, 1 mg · kg
−1
· d
−1
simvastatin decreased bone formation while increasing bone resorption, as reflected by a marked decrease in BMD. Ovariectomized animals receiving 20 mg · kg
−1
· d
−1
simvastatin showed no change in BMD relative to the untreated, ovariectomized controls; their increase in bone formation was smaller than in sham-operated rats receiving simvastatin, and there was no change in bone resorption. Dose-response curves of simvastatin for bone formation and resorption differed. These studies indicate that (1) statins decrease BMD in rodents, (2) high-dose simvastatin increases bone formation and resorption, (3) low-dose simvastatin decreases bone formation and increases bone resorption, (4) the effects of simvastatin on QBH differ at different dosages, (5) the effects of simvastatin seen in intact rats are not observed in ovariectomized rats, and (6) simvastatin is unable to prevent bone loss caused by ovariectomy.
Genome Scan for Quantitative Trait Loci Linked to High-Density Lipoprotein Cholesterol
Authors: Peacock James M. , Arnett Donna K. , Atwood Larry D. , Myers Richard H. , Coon Hilary , Rich Stephen S. , Province Michael A. , Heiss Gerardo
Published: September 2007

We conducted a genome-wide linkage scan for quantitative trait loci influencing total HDL-cholesterol (HDL-C) concentration in a sample of 1027 whites from 101 families participating in the NHLBI Family Heart Study. To maximize the relative contribution of genetic components of variance to the total variance of HDL-C, the HDL-C phenotype was adjusted for age, age
2
, body mass index, and Family Heart Study field center, and standardized HDL-C residuals were created separately for men and women. All analyses were completed by the variance components method, as implemented in the program GENEHUNTER using 383 anonymous markers typed at the NHLBI Mammalian Genotyping Service in Marshfield, Wis. Evidence for linkage of residual HDL-C was detected near marker D5S1470 at location 39.9 cM from the p-terminal of chromosome 5 (LOD=3.64). Suggestive linkage was detected near marker D13S1493 at location 27.5 cM on chromosome 13 (LOD=2.36). We conclude that at least 1 genomic region is likely to harbor a gene that influences interindividual variation in HDL cholesterol.
Vascular Endothelial Cell Growth Factor-Driven Endothelial Tube Formation Is Mediated by Vascular Endothelial Cell Growth Factor Receptor-2, a Kinase Insert Domain-Containing Receptor
Authors: Yang Suya , Xin Xiaohua , Zlot Constance , Ingle Gladys , Fuh Germaine , Li Bing , Moffat Barbara , de Vos Abraham M. , Gerritsen Mary E.
Published: September 2007

Abstract
—

Vascular endothelial cell growth factor (VEGF) binds to 2 related receptor tyrosine kinases, known as kinase insert domain-containing receptor (KDR) and
fms
-like tyrosine kinase (Flt-1). The KDR has been shown to mediate VEGF-stimulated endothelial cell mitogenesis, migration, and permeability. The Flt-1 receptor has been suggested to mediate VEGF-stimulated endothelial branching morphogenesis, a process whereby endothelial cells, in the presence of a 3D milieu composed of extracellular matrix components and a mixture of growth factors, undergo a morphological transition into a tubular network with many lumina. In the present study, we have used 2 independent endothelial cell tube formation models and highly selective VEGF mutants for the KDR and Flt-1 receptors. We demonstrate that KDR, not Flt-1, stimulation is responsible for the induction of endothelial tubulogenesis. In addition, we demonstrate a modulatory role for Flt-1 in VEGF-mediated tube formation. We also report that VEGF-driven endothelial tube formation is inhibited by selective inhibitors of mitogen-activated protein kinase activation and p38 protein kinase.
Vascular Outcome in Patients With Homocystinuria due to Cystathionine β-Synthase Deficiency Treated Chronically
Authors: Yap Sufin , Boers Godfried H.J. , Wilcken Bridget , Wilcken David E.L. , Brenton David P. , Lee Philip J. , Walter John H. , Howard Pamela M. , Naughten Eileen R.
Published: September 2007

An inborn error of metabolism, homocystinuria due to cystathionine β-synthase deficiency, results in markedly elevated levels of circulating homocysteine. Premature vascular events are the main life-threatening complication. Half of all untreated patients have a vascular event by 30 years of age. We performed a multicenter observational study to assess the effectiveness of long-term homocysteine-lowering treatment in reducing vascular risk in 158 patients. Vascular outcomes were analyzed and effectiveness of treatment in reducing vascular risk was evaluated by comparison of actual to predicted number of vascular events, with the use of historical controls from a landmark study of 629 untreated patients with cystathionine β-synthase deficiency. The 158 patients had a mean (range) age of 29.4 (4.5 to 70) years; 57 (36%) were more than 30 years old, and 10 (6%) were older than 50 years. There were 2822 patient-years of treatment, with an average of 17.9 years per patient. Plasma homocysteine levels were markedly reduced from pretreatment levels but usually remained moderately elevated. There were 17 vascular events in 12 patients at a mean (range) age of 42.5 (18 to 67) years: pulmonary embolism (n=3), myocardial infarction (n=2), deep venous thrombosis (n=5), cerebrovascular accident (n=3), transient ischemic attack (n=1), sagittal sinus thrombosis (n=1), and abdominal aortic aneurysm (n=2). Without treatment, 112 vascular events would have been expected, for a relative risk of 0.09 (95% CI 0.036 to 0.228;
P
<0.0001). Treatment regimens designed to lower plasma homocysteine significantly reduce cardiovascular risk in cystathionine β-synthase deficiency despite imperfect biochemical control. These findings may be relevant to the significance of mild hyperhomocysteinemia that is commonly found in patients with vascular disease.
Estrogen Replacement and Brachial Artery Flow-Mediated Vasodilation in Older Women
Authors: Herrington David M. , Espeland Mark A. , Crouse John R. , Robertson Julia , Riley Ward A. , McBurnie Mary Ann , Burke Gregory L.
Published: September 2007

It remains unclear whether estrogen therapy (with or without progestin) improves endothelial function in older postmenopausal women with or at risk for coronary heart disease. To address this issue, we analyzed brachial artery flow-mediated vasodilation in the Cardiovascular Health Study, a longitudinal study of cardiovascular risk factors in subjects over 65 years of age. At the tenth annual Cardiovascular Health Study examination, 1662 women returned for follow-up. Eighteen percent (n=291) were current users of estrogen replacement, most of whom (75.9%, n=221) took unopposed estrogen. Brachial artery ultrasound examinations measuring vasodilation in response to a flow stimulus (hyperemia) were performed on 1636 women. There were no statistical differences in brachial flow-mediated vasodilator responses between users and nonusers, even after adjustment for potential confounders. Absence of an effect was most notable in women over 80 years old and in those with established cardiovascular disease. However, among women without clinical or subclinical cardiovascular disease or its risk factors, there was a significant association between hormone replacement therapy use and flow-mediated vasodilator responses (
P
=0.01). Among older postmenopausal women, favorable vascular effects of estrogen may be limited to those who have not yet developed atherosclerotic vascular disease. These data emphasize the importance of ongoing efforts to determine the role of hormone replacement therapy for primary prevention of cardiovascular disease.
Association of Multiple Risk Factors and Insulin Resistance With Increased Prevalence of Asymptomatic Coronary Artery Disease by an Electron-Beam Computed Tomographic Study
Authors: Arad Yadon , Newstein David , Cadet Fredrick , Roth Marguerite , Guerci Alan D.
Published: September 2007

The insulin resistance syndrome, consisting of resistance to insulin and several metabolic abnormalities, is associated with an increased risk of symptomatic coronary artery disease. Asymptomatic persons with increased coronary calcification have increased coronary plaque and an increased likelihood of future cardiovascular events. Electron-beam computed tomography–derived coronary artery calcium scores, metabolic and anthropometric parameters, and fasting and stimulated concentrations of glucose and insulin were measured in 1160 asymptomatic men and women. Coronary artery calcium scores were positively correlated with glucose, insulin, and homeostasis model assessment (HOMA) insulin resistance. Calcium scores were positively correlated with intra-abdominal adiposity, age, total cholesterol/high density lipoprotein (HDL) ratio, low density lipoprotein, triglycerides, blood pressure, and HOMA beta cell function and inversely correlated with HDL and peripheral fat. These correlations, except for 2-hour glucose, remained significant for all subjects with fasting serum glucose <126 mg/dL or all subjects with fasting serum glucose 110 mg/dL. In a multivariate analysis, age, sex, family history of premature coronary artery disease, intra-abdominal adiposity, low density lipoprotein, and smoking independently predicted calcium scores. Blood pressure, HDL, triglycerides, glucose, insulin, and HOMA insulin resistance or beta cell function were not independently correlated with coronary artery calcium scores. Asymptomatic individuals with insulin resistance have elevated coronary calcium scores. The association between insulin resistance and coronary calcification persists with impaired glucose tolerance and normal fasting serum glucose. Central/visceral adiposity may be a determinant of insulin resistance and atherosclerosis even in asymptomatic nondiabetic persons.
Renal Cyclooxygenase-2
Authors: Leon Carmen G. , Marchetti Jeannine , Vio Carlos P.
Published: September 2007

Abstract
—

— Prostaglandins participate in the regulation of sodium and water renal excretion. They are synthesized by cyclooxygenases (COX): the constitutive isoform and the enzyme regulated by physiological stimuli (COX-2). Our previous immunohistochemical studies have demonstrated the presence of COX-2 in a subset of thick ascending limb (TAL) of Henle cells and its induction during the postnatal period and after adrenalectomy. Previous results suggested that this induction phenomenon proceeds by recruitment of TAL cells from the cortex to the outer medulla. The present work aimed to specifically address these preliminary observations by using immunohistochemical techniques in single microdissected nephron segments. Normal adult rats, adrenalectomized rats, adrenalectomized rats on dexamethasone and 5, 10, and 15 days postnatal age were used (Sprague-Dawley rats, n= 5 each group). Glomeruli and different segments of nephron were microdissected from collagenase-treated kidney tissue. Tubules were immunostained with specific antibodies against COX-2. We confirmed that COX-2 was localized exclusively in TAL segments; it was induced after adrenalectomy and during postnatal age, peaking at 15 days after birth. We provided morphological evidence that the induction of COX-2 along TAL proceeded in a defined pattern by recruitment of cells from the cortical portion close to the glomeruli toward the outer medulla. No COX-2 was observed in the post-macula densa portion of the segments. Our results provide the anatomical basis for the contribution of COX-2 in physiological mechanisms such as renin secretion, tubuloglomerular feedback, and the interaction with neuronal NO synthase at the juxtaglomerular apparatus.
Functional Assessment of the Circulation of the Single Kidney
Authors: Lerman Lilach O. , Rodriguez-Porcel Martin
Published: September 2007

Abstract
—

— Functional alterations in the renal circulation that can contribute to abnormal renal perfusion have been demonstrated in various models of renal injury. To detect impairments in renal vascular function, renal flow reserve can be determined by repeated measurements of renal blood flow (RBF) during pharmacological challenge with short-acting vasodilators that should increase RBF in kidneys that are not severely damaged structurally. Among the invasive techniques for such measurements, the most readily available is probably the intravascular Doppler, which can be employed during renal angiography for rapid evaluation of changes in RBF during intrarenal injections of vasoactive substances. High-resolution tomographic imaging techniques, like electron-beam x-ray computed tomography, further offer the potential for noninvasive measurements of renal parenchymal perfusion and function, in association with either intrarenal or systemic injections of vasoactive substances. Acetylcholine is a potent short-acting renal vasodilator that can be useful to assess the response of the renal microcirculation, define renal flow reserve, and examine the endothelium-dependent responses of RBF. Such assessments of the function of the renal circulation can assist in evaluation of patients with systemic or renal disease for early detection and monitoring of renovascular injury.
Altered Cellular Magnesium Responsiveness to Hyperglycemia in Hypertensive Subjects
Authors: Barbagallo Mario , Dominguez Ligia J. , Bardicef Orit , Resnick Lawrence M.
Published: September 2007

Abstract
—

— Previous studies by our group have identified ionic aspects of insulin resistance in hypertension, in which cellular responses to insulin were influenced by the basal intracellular ionic environment—the lower the cytosolic free magnesium (Mg
i
), the less Mg
i
increased following insulin stimulation. To investigate whether this ionic insulin resistance represents a more general abnormality of cellular responsiveness in hypertension, we studied Mg
i
responses to nonhormonal signals such as hyperglycemia (15 mmol/L) and used
31
P-nuclear magnetic resonance (NMR) spectroscopy to measure Mg
i
in erythrocytes from normal (NL, n=14) and hypertensive (HTN, n=12) subjects before and 30, 60, 120, and 180 minutes after in vitro glucose incubations. Basal Mg
i
levels were significantly lower in HTN subjects than in NL subjects (169±10 versus 205±8 μmol·L
−1
,
P
<0.01). In NL cells, hyperglycemia significantly lowered Mg
i
, from 205±8 μmol·L
−1
(basal, T=0) to 181±8, 162±6, 152±7, and 175±9 μmol·L
−1
(T=30, 60, 120, and 180, respectively;
P
<0.005 versus T=0 at all times). In HTN cells, maximal Mg
i
responses to hyperglycemia were blunted, from 169±10 μmol·L
−1
(basal, T=0) to 170±11, 179±12, 181±14, and 173±15 μmol·L
−1
(T=30, 60, 120, and 180, respectively;
P
=NS versus T=0 at all times). For all subjects, Mg
i
responses to hyperglycemia were closely related to basal Mg
i
levels: the higher the Mg
i
, the greater the response (n=26,
r
=0.620,
P
<0.001). Thus, (1) erythrocytes from hypertensive vis-à-vis normotensive subjects are resistant to the ionic effects of extracellular hyperglycemia on Mg
i
levels, and (2) cellular ionic responses to glucose depend on the basal Mg
i
environment. Altogether, these data support a role for altered extracellular glucose levels in regulating cellular magnesium metabolism and also suggest the importance of ionic factors in determining cellular responsiveness to nonhormonal as well as hormonal signals.