Predictors of very low adherence with medications for osteoporosis: towards development of a clinical prediction rule.

UNLABELLED: We developed a clinical prediction rule score to predict medication non-adherence for women prescribed osteoporosis treatment. When combined into a summative score, 62% with seven or more points on the score demonstrated very low adherence. This compares with 17% subjects with fewer than seven points (c-statistic = 0.74). INTRODUCTION: Medication non-adherence is extremely common for osteoporosis; however, no clear methods exist for identifying patients at risk of this behavior. We developed a clinical prediction rule to predict medication non-adherence for women prescribed osteoporosis treatment. METHODS: Women undergoing bone mineral density testing and fulfilling WHO criteria for osteoporosis were invited to complete a questionnaire and then followed for 1 year. Adjusted logistic regression models were examined to identify variables associated with very low adherence (medication possession ratio <20%). The weighted variables, based on the logistic regression, were summed, and the score was compared with the proportion of subjects with very low adherence. RESULTS: One hundred forty two women participated in the questionnaire and were prescribed an osteoporosis medication. After 1 year, 36% (n = 50) had very low adherence. Variables associated with very low adherence included prior non-adherence with chronic medications, agreement that side effects are concerning, agreement that she is taking too many medications, lack of agreement that osteoporosis is a worry, lack of agreement that a fracture will cause disability, lack of agreement that medications help her stay active, and frequent use of alcohol. When combined into a summative score, 36 of the 58 subjects (62%) with seven or more points on the score demonstrated very low adherence. This compares with 14 of the 84 (17%) subjects with fewer than seven points (c-statistic = 0.74). CONCLUSION: We developed a brief clinical prediction rule that was able to discriminate between women likely (and unlikely) to experience very low adherence with osteoporosis medications.

Nicotine stimulates angiogenesis and promotes tumor growth and atherosclerosis.

We provide anatomic and functional evidence that nicotine induces angiogenesis. We also show that nicotine accelerates the growth of tumor and atheroma in association with increased neovascularization. Nicotine increased endothelial-cell growth and tube formation in vitro, and accelerated fibrovascular growth in vivo. In a mouse model of hind-limb ischemia, nicotine increased capillary and collateral growth, and enhanced tissue perfusion. In mouse models of lung cancer and atherosclerosis, we found that nicotine enhanced lesion growth in association with an increase in lesion vascularity. These effects of nicotine were mediated through nicotinic acetylcholine receptors at nicotine concentrations that are pathophysiologically relevant. The endothelial production of nitric oxide, prostacyclin and vascular endothelial growth factor might have a role in these effects.

Inflammation in subcutaneous adipose tissue: relationship to adipose cell size.

AIMS/HYPOTHESIS: Inflammation is associated with increased body mass and purportedly with increased size of adipose cells. We sought to determine whether increased size of adipose cells is associated with localised inflammation in weight-stable, moderately obese humans. METHODS: We recruited 49 healthy, moderately obese individuals for quantification of insulin resistance (modified insulin suppression test) and subcutaneous abdominal adipose tissue biopsy. Cell size distribution was analysed with a multisizer device and inflammatory gene expression with real-time PCR. Correlations between inflammatory gene expression and cell size variables, with adjustment for sex and insulin resistance, were calculated. RESULTS: Adipose cells were bimodally distributed, with 47% in a 'large' cell population and the remainder in a 'small' cell population. The median diameter of the large adipose cells was not associated with expression of inflammatory genes. Rather, the fraction of small adipose cells was consistently associated with inflammatory gene expression, independently of sex, insulin resistance and BMI. This association was more pronounced in insulin-resistant than insulin-sensitive individuals. Insulin resistance also independently predicted expression of inflammatory genes. CONCLUSIONS/INTERPRETATION: This study demonstrates that among moderately obese, weight-stable individuals an increased proportion of small adipose cells is associated with inflammation in subcutaneous adipose tissue, whereas size of mature adipose cells is not. The observed association between small adipose cells and inflammation may reflect impaired adipogenesis and/or terminal differentiation. However, it is unclear whether this is a cause or consequence of inflammation. This question and whether small vs large adipose cells contribute differently to inflammation in adipose tissue are topics for future research. TRIAL REGISTRATION: ClinicalTrials.gov NCT00285844.

Novel vascular molecule involved in monocyte adhesion to aortic endothelium in models of atherogenesis.

Adhesion of monocytes to the endothelium in lesion-prone areas is one of the earliest events in fatty streak formation leading to atherogenesis. The molecular basis of increased monocyte adhesion is not fully characterized. We have identified a novel vascular monocyte adhesion-associated protein, VMAP-1, that plays a role in adhesion of monocytes to activated endothelium. Originally selected for its ability to block binding of a mouse monocyte-like cell line (WEHI78/24) to cytokine- or LPS-stimulated cultured mouse endothelial cells in vitro, antiVMAP-1 mAb LM151 cross-reacts with rabbit endothelium and blocks binding of human monocytes to cultured rabbit aortic endothelial cells stimulated with minimally modified low density lipoprotein, thought to be a physiologically relevant atherogenic stimulus. Most importantly, LM151 prevents adhesion of normal monocytes and monocytoid cells to intact aortic endothelium from cholesterol-fed rabbits in an ex vivo assay. VMAP-1 is a 50-kD protein. Immunohistology of vessels reveals focal constitutive expression in aorta and other large vessels. VMAP-1 is thus a novel vascular adhesion-associated protein that appears to play a critical role in monocyte adhesion to aortic endothelial cells in atherogenesis in vivo.

Mediation of cardioprotection by transforming growth factor-beta.

Myocardial ischemia causes heart injury that is characterized by an increase in circulating tumor necrosis factor (TNF), the local production of superoxide anions, the loss of coronary vasodilation (relaxation) in response to agents that release endothelial cell relaxation factor, and cardiac tissue damage. Ischemic injury can be mimicked by TNF. When given before or immediately after ischemic injury, transforming growth factor-beta (TGF-beta) reduced the amount of superoxide anions in the coronary circulation, maintained endothelial-dependent coronary relaxation, and reduced injury mediated by exogenous TNF. Thus, TGF-beta prevented severe cardiac injury, perhaps by alleviating damage mediated by increases in circulating TNF.

Insulin resistance is associated with a modest increase in inflammation in subcutaneous adipose tissue of moderately obese women.

AIMS/HYPOTHESIS: We have previously described differences in adipose cell size distribution and expression of genes related to adipocyte differentiation in subcutaneous abdominal fat obtained from insulin-sensitive (IS) and -resistant (IR) persons, matched for degree of moderate obesity. To determine whether other biological properties also differ between IR and IS obese individuals, we quantified markers of inflammatory activity in adipose tissue from overweight IR and IS individuals. METHODS: Subcutaneous abdominal tissue was obtained from moderately obese women, divided into IR (n = 14) and IS (n = 19) subgroups by determining their steady-state plasma glucose (SSPG) concentrations during the insulin suppression test. Inflammatory activity was assessed by comparing expression of nine relevant genes and by immunohistochemical quantification of CD45- and CD68-containing cells. RESULTS: SSPG concentrations were approximately threefold higher in IR than in IS individuals. Expression levels of CD68, EMR1, IL8, IL6 and MCP/CCL2 mRNAs were modestly but significantly increased (p < 0.05) in IR compared with IS participants. Results of immunohistochemical staining were consistent with gene expression data, demonstrating modest differences between IR and IS individuals. Crown-like structures, in which macrophages surround single adipocytes, were rarely seen in tissue from either subgroup. CONCLUSIONS/INTERPRETATION: A modest increase in inflammatory activity was seen in subcutaneous adipose tissue from IR compared with equally obese IS individuals. Together with previous evidence of impaired adipose cell differentiation in IR vs equally obese individuals, it appears that at least two biological processes in subcutaneous adipose tissue characterize the insulin-resistant state independent of obesity per se.

Antibody to CD-18 exerts endothelial and cardiac protective effects in myocardial ischemia and reperfusion.

We studied the effects of MAbR15.7, an antibody directed against the common beta-chain (CD-18) of a family of neutrophil adherence glycoproteins, on endothelial dysfunction and myocardial injury in a model of myocardial ischemia and reperfusion in cats. Pentobarbital-anesthetized cats were subjected to 1.5 h occlusion of the left anterior descending coronary artery (LAD) and 4.5 h of reperfusion. MI + R resulted in severe myocardial injury and endothelial dysfunction, including significant elevation of plasma creatine kinase (CK) activity, marked myocardial necrosis, high cardiac myeloperoxidase (MPO) activity in ischemic cardiac tissue, and loss of response of LAD coronary rings to the endothelium-dependent vasodilators, acetylcholine (ACh) and A-23187. In contrast, MAbR15.7-treated cats exhibited a lower plasma CK activity at every time point observed after 2 h, a reduced area of cardiac necrosis (2 +/- 1 vs. 30.8 +/- 2.5% of area-at-risk, P less than 0.001), lower MPO activity in the ischemic region (P less than 0.01), and significantly preserved vasorelaxant responses of LAD coronary rings to endothelium-dependent vasodilators, ACh (P less than 0.001), and A-23187 (P less than 0.001). These results indicate that myocardial ischemia and reperfusion induces significant myocardial injury and endothelial dysfunction in the cat involving a CD18-dependent neutrophil adherence mechanism. Inhibition of neutrophil adherence to the endothelium exerts significant protective effects in this model of reperfusion injury.

Antiatherogenic effects of L-arginine in the hypercholesterolemic rabbit.

The purpose of this study was to determine if chronic administration of L-arginine, the precursor of endothelium-derived relaxing factor (EDRF), normalizes endothelium-dependent relaxation and decreases atherosclerosis in hypercholesterolemic animals. Male rabbits were fed (a) normal rabbit chow; (b) 1% cholesterol diet; or (c) 1% cholesterol diet supplemented by 2.25% L-arginine HCl in drinking water. Arginine supplementation doubled plasma arginine levels without affecting serum cholesterol values. After 10 wk, the thoracic aorta was harvested for studies of vascular reactivity and histomorphometry. Endothelium-dependent relaxations (to acetylcholine and calcium ionophore A23187) were significantly impaired in thoracic aortae from animals fed a 1% cholesterol diet. By contrast, vessels from hypercholesterolemic animals receiving L-arginine supplementation exhibited significantly improved endothelium-dependent relaxations. Responses to norepinephrine or nitroglycerin were not affected by either dietary intervention. Histomorphometric analysis revealed a reduction in lesion surface area and intimal thickness in thoracic aortae from arginine-supplemented animals compared to those from untreated hypercholesterolemic rabbits. This is the first study to demonstrate that supplementation of dietary L-arginine, the EDRF precursor, improves endothelium-dependent vasorelaxation. More importantly, we have shown that this improvement in EDRF activity is associated with a reduction in atherogenesis.

Cell cycle inhibition preserves endothelial function in genetically engineered rabbit vein grafts.

We have recently shown that ex vivo gene therapy of rabbit autologous vein grafts with antisense oligodeoxynucleotides (AS ODN) blocking cell cycle regulatory gene expression inhibits not only neointimal hyperplasia, but also diet-induced, accelerated graft atherosclerosis. We observed that these grafts remained free of macrophage invasion and foam cell deposition. Since endothelial dysfunction plays an important role in vascular disease, the current study examined the effect of this genetic engineering strategy on graft endothelial function and its potential relationship to the engineered vessels' resistance to atherosclerosis. Rabbit vein grafts transfected with AS ODN against proliferating cell nuclear antigen (PCNA) and cell division cycle 2 (cdc2) kinase elaborated significantly more nitric oxide and exhibited greater vasorelaxation to both calcium ionophore and acetylcholine than did untreated or control ODN-treated grafts. This preservation of endothelial function was associated with a reduction in superoxide radical generation, vascular cell adhesion molecule-1 (VCAM-1) expression, and monocyte binding activity in grafts in both normal and hypercholesterolemic rabbits. Our data demonstrate that AS ODN arrest of vascular cell cycle progression results in the preservation of normal endothelial phenotype and function, thereby influencing the biology of the vessel wall towards a reduction of its susceptibility to occlusive disease.

Downregulation of G protein-coupled receptors.

Major advances have been made in understanding mechanisms mediating downregulation of G protein-coupled receptors. Recent studies emphasize the role of multiple proteolytic mechanisms in downregulation. A specific mechanism of downregulation, mediated by endocytosis of receptors via clathrin-coated pits followed by sorting to lysosomes, has been examined in detail. Specific protein interactions that control the specificity of G-protein-coupled receptor trafficking in this pathway are beginning to be elucidated.

eNOS activity is reduced in senescent human endothelial cells: Preservation by hTERT immortalization.

Advanced age is associated with endothelial dysfunction and increased risk for atherosclerosis. However, the mechanisms for these observed effects are not clear. To clarify the association between aging and loss of endothelial function, young human aortic endothelial cells (HAECs), senescent HAECs transfected with control vector, and immortalized HAECs containing human telomerase reverse transcriptase (hTERT) were compared for expression of endothelial nitric oxide synthase (eNOS) and production of NO. To investigate a specific function modulated by endothelial NO, adhesion of monocytes under basal conditions as well as after exposure to TNF-alpha was assessed. A decrease in eNOS mRNA, protein, and activity was observed in endothelial cells at senescence as compared with young HAEC; this effect was blunted in hTERT cells. In all cells, shear stress induced a greater increase in the expression of eNOS protein with the final result being higher levels in hTERT compared with senescent cells. Basal monocyte binding was significantly elevated on aged endothelial cells compared with parental and hTERT cells. Exposure of TNF-alpha resulted in a 2-fold increase in monocyte adhesion in senescent cells, whereas this effect was reduced in cells transfected with hTERT. Prior exposure to fluid flow significantly reduced subsequent monocyte adhesion in all groups. These studies demonstrate that replicative aging results in decreased endothelial expression of eNOS accompanied by enhanced monocyte binding. Stable expression of hTERT results in endothelial cells with a younger phenotype with greater amount of eNOS and NO activity. Thus, telomerase transfection may have important functional consequences on endothelial cells.

Diabetes mellitus enhances vascular matrix metalloproteinase activity: role of oxidative stress.

Diabetes mellitus (DM) is a primary risk factor for cardiovascular disease. Although recent studies have demonstrated an important role for extracellular matrix metalloproteinases (MMPs) in atherosclerosis, little is known about the effects of hyperglycemia on MMP regulation in vascular cells. Gelatin zymography and Western blot analysis revealed that the activity and expression of 92-kDa (MMP-9) gelatinase, but not of 72 kDa (MMP-2) gelatinase, were significantly increased in vascular tissue and plasma of two distinct rodent models of DM. Bovine aortic endothelial cells (BAECs) grown in culture did not express MMP-9 constitutively; however, chronic (2-week) incubation with high glucose medium induced MMP-9 promoter activity, mRNA and protein expression, and gelatinase activity in BAECs. On the other hand, high glucose culture did not change MMP-9 activity from vascular smooth muscle cells or macrophages. Electron paramagnetic resonance studies indicate that BAECs chronically grown in high glucose conditions produce 70% more ROS than do control cells. Enhanced MMP-9 activity was significantly reduced by treatment with the antioxidants polyethylene glycol-superoxide dismutase and N-acetyl-L-cysteine but not by inhibitors of protein kinase C. In conclusion, vascular MMP-9 activity is increased in DM, in part because of enhanced elaboration from vascular endothelial cells, and oxidative stress plays an important role. This novel mechanism of redox-sensitive MMP-9 expression by hyperglycemia may provide a rationale for antioxidant therapy to modulate diabetic vascular complications.

Factors affecting growth factor activity in goat milk.

Growth factors that are present in goat milk may be responsible for its beneficial effects on the digestive system as described in ancient Chinese medical texts. To develop a nutraceutical product rich in growth factors for promoting gastrointestinal health, it is essential to collect milk with consistently high growth factor activity. Therefore, we investigated the factors affecting growth factor activity in goat milk. Among the 5 breeds of dairy goats tested, milk from Nubian goats had the highest growth factor activity. Tight-junction leakage induced by a 24-h milking interval did not increase growth factor activity in the milk. Milk collected from pregnant does had a significantly higher growth factor activity than milk collected postpartum. Growth factor activity decreased during the first 8 wk of lactation, fluctuated thereafter, and then increased dramatically after natural mating. During wk 1 to 8, growth factor activity was inversely correlated with milk yield and week of lactation. No correlation was observed during wk 9 to 29. After natural mating of the goats, the growth factor activity in the milk correlated significantly with somatic cell count and conductivity (a measure of membrane permeability), and correlated inversely with milk yield. Based on the above data, goat milk with higher growth factor activity could be selectively collected from Nubian pregnant does.

Homocysteine impairs the nitric oxide synthase pathway: role of asymmetric dimethylarginine.

BACKGROUND: Hyperhomocysteinemia is a putative risk factor for cardiovascular disease, which also impairs endothelium-dependent vasodilatation. A number of other risk factors for cardiovascular disease may exert their adverse vascular effects in part by elevating plasma levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase. Accordingly, we determined if homocysteine could increase ADMA levels. METHODS AND RESULTS: When endothelial or nonvascular cells were exposed to DL-homocysteine or to its precursor L-methionine, ADMA concentration in the cell culture medium increased in a dose- and time-dependent fashion. This effect was associated with the reduced activity of dimethylarginine dimethylaminohydrolase (DDAH), the enzyme that degrades ADMA. Furthermore, homocysteine-induced accumulation of ADMA was associated with reduced nitric oxide synthesis by endothelial cells and segments of pig aorta. The antioxidant pyrrollidine dithiocarbamate preserved DDAH activity and reduced ADMA accumulation. Moreover, homocysteine dose-dependently reduced the activity of recombinant human DDAH in a cell free system, an effect that was due to a direct interaction between homocysteine and DDAH. CONCLUSION: Homocysteine post-translationally inhibits DDAH enzyme activity, causing ADMA to accumulate and inhibit nitric oxide synthesis. This may explain the known effect of homocysteine to impair endothelium-mediated nitric oxide-dependent vasodilatation.

Novel mechanism for endothelial dysfunction: dysregulation of dimethylarginine dimethylaminohydrolase.

BACKGROUND: Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS). Plasma levels of ADMA are elevated in individuals with hypercholesterolemia or atherosclerosis. We postulated that reduced degradation of ADMA may play a role in the accumulation of ADMA in these individuals. Accordingly, we studied the effects of oxidized LDL (oxLDL) or tumor necrosis factor-alpha (TNF-alpha) on the accumulation of ADMA by transformed human umbilical vein endothelial cells (ECV304) and on the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which degrades ADMA. METHODS AND RESULTS: ECV304 were incubated with or without native LDL (100 micrograms/mL), oxLDL (100 micrograms/mL), or TNF-alpha (250 U/mL) for 48 hours. The concentration of ADMA in the conditioned medium was determined by high-performance liquid chromatography. Western blotting was performed to evaluate DDAH expression. We assayed DDAH activity by determining L-citrulline formation from ADMA. The addition of oxLDL or TNF-alpha to ECV304 significantly increased the level of ADMA in the conditioned medium. The effect of oxLDL or TNF-alpha was not due to a change in DDAH expression but rather to the reduction of DDAH activity. To determine whether dysregulation of DDAH also occurred in vivo, New Zealand White rabbits were fed normal chow or a high-cholesterol diet. Hypercholesterolemia significantly reduced aortic, renal, and hepatic DDAH activity. CONCLUSIONS: These results suggest that the endothelial vasodilator dysfunction observed in hypercholesterolemia may be due to reduced degradation of ADMA, the endogenous inhibitor of NOS.

Mononuclear cell adherence to cultured endothelium is enhanced by hypertension and insulin resistance in healthy nondiabetic volunteers.

BACKGROUND: This study was initiated to compare the adherence to cultured endothelial cells of mononuclear cells isolated from normotensive and hypertensive individuals. METHODS AND RESULTS: Mononuclear cell binding to endothelium was greater in patients with hypertension (32+/-1 versus 25+/-2; P<0.001) than in normal volunteers. There was a significant relationship (r=0.42, P<0. 01) between mononuclear cell binding and mean arterial pressure, independent of differences in age, sex, and body mass index. A significant relationship also existed between insulin resistance (estimated by the steady-state plasma glucose concentration during the insulin suppression test) and mononuclear cell binding in both the normotensive (r=0.86, P<0.001) and hypertensive (r=0.74, P<0. 001) groups. Furthermore, multiple regression analysis demonstrated an independent relationship (P<0.001) between mononuclear cell binding and both steady-state plasma glucose and hypertensive status. CONCLUSIONS: These results indicate that both hypertension and insulin resistance lead to changes in mononuclear cells that increase their adherence to cultured endothelial cells.

Stent-based delivery of sirolimus reduces neointimal formation in a porcine coronary model.

BACKGROUND: The purpose of this study was to determine the efficacy of stent-based delivery of sirolimus (SRL) alone or in combination with dexamethasone (DEX) to reduce in-stent neointimal hyperplasia. SRL is a potent immunosuppressive agent that inhibits SMC proliferation by blocking cell cycle progression. METHODS AND RESULTS: Stents were coated with a nonerodable polymer containing 185 microgram SRL, 350 microgram DEX, or 185 microgram SRL and 350 microgram DEX. Polymer biocompatibility studies in the porcine and canine models showed acceptable tissue response at 60 days. Forty-seven stents (metal, n=13; SRL, n=13; DEX, n=13; SRL and DEX, n=8) were implanted in the coronary arteries of 16 pigs. The tissue level of SRL was 97+/-13 ng/artery, with a stent content of 71+/-10 microgram at 3 days. At 7 days, proliferating cell nuclear antigen and retinoblastoma protein expression were reduced 60% and 50%, respectively, by the SRL stents. After 28 days, the mean neointimal area was 2.47+/-1.04 mm(2) for the SRL alone and 2.42+/-1.04 mm(2) for the combination of SRL and DEX compared with the metal (5.06+/-1.88 mm(2), P<0.0001) or DEX-coated stents (4.31+/-3.21 mm(2), P<0.001), resulting in a 50% reduction of percent in-stent stenosis. CONCLUSIONS: Stent-based delivery of SRL via a nonerodable polymer matrix is feasible and effectively reduces in-stent neointimal hyperplasia by inhibiting cellular proliferation.

Role of endocytosis in mediating downregulation of G-protein-coupled receptors.

Many G-protein-coupled receptors (GPCRs) undergo agonist-induced endocytosis. Such endocytosis has been implicated in diverse processes of receptor regulation, including reversible sequestration of receptors in endosomes and proteolytic downregulation of receptors in lysosomes. The precise relationships between membrane pathways that mediate receptor sequestration and downregulation remain controversial. Recent studies suggest that GPCRs can be segregated within distinct microdomains of the plasma membrane before endocytosis occurs, and others suggest that certain GPCRs are sorted between divergent membrane pathways after endocytosis by clathrin-coated pits. Furthermore, emerging data implicate a specific role of the actin cytoskeleton and receptor phosphorylation in controlling endocytic sorting of a particular GPCR. In this article, recent research into endocytosis of GPCRs will be discussed together with some important and unresolved questions regarding the diversity and specificity of mechanisms that mediate downregulation of GPCRs.

Dietary arginine prevents atherogenesis in the coronary artery of the hypercholesterolemic rabbit.

OBJECTIVES: This study was designed to test the hypothesis that long-term oral supplementation of dietary L-arginine (to provide a sustained elevation of nitric oxide activity) would inhibit atherogenesis in hypercholesterolemic rabbits, as assessed by histomorphometric measurements. BACKGROUND: Endothelium-derived nitric oxide inhibits a number of processes that are critical in atherogenesis. Hypercholesterolemia reduces endothelial nitric oxide activity, and we postulate that this may promote atherogenesis. This reduction in nitric oxide activity can be reversed acutely by intravenous infusion of L-arginine, the precursor of nitric oxide. We show that dietary supplementation of L-arginine abrogates the development of coronary atheroma in hypercholesterolemic rabbits. METHODS: Male New Zealand White rabbits were fed normal rabbit chow, 1% cholesterol chow or 1% cholesterol chow with dietary arginine or methionine supplementation to increase their intake of these amino acids sixfold. After 1 or 10 weeks of dietary intervention, the left main and left anterior descending coronary arteries were harvested for histologic study. Plasma cholesterol measurements were elevated to the same degree in all groups of rabbits receiving the 1% cholesterol diet, whereas plasma arginine levels were doubled in the arginine-treated group. High density lipoprotein (HDL) cholesterol values were not affected by arginine treatment. RESULTS: In rabbits receiving the 1% cholesterol diet, with or without methionine supplementation, light and electron microscopy revealed a marked increase from 1 to 10 weeks in the intimal accumulation of macrophages, associated with an increase in the intimal area of the left main coronary artery. By contrast, in arginine-treated hypercholesterolemic rabbits, there was a near absence of adherent monocytes and tissue macrophages and no progression of intimal thickness from 1 to 10 weeks. CONCLUSIONS: Dietary supplements of L-arginine prevent intimal thickening in the coronary arteries of hypercholesterolemic rabbits. This antiatherogenic effect is not due to an alteration in plasma total cholesterol, HDL cholesterol or caloric or nitrogen balance. The data are consistent with the hypothesis that nitric oxide has antiatherogenic properties.

Arginine restores nitric oxide activity and inhibits monocyte accumulation after vascular injury in hypercholesterolemic rabbits.

OBJECTIVES: This study sought to determine whether the alterations in vascular function and structure after balloon injury in hypercholesterolemic rabbits could be inhibited by dietary arginine. BACKGROUND: Administration of arginine (the nitric oxide [NO] precursor) restores vascular NO activity in hypercholesterolemic animals. We and other investigators have shown that enhancement of vascular NO activity can inhibit myointimal hyperplasia after vascular injury in normocholesterolemic animals. METHODS: Twenty-eight New Zealand White rabbits received either normal rabbit chow, 0.5% cholesterol diet or 0.5% cholesterol diet plus L-arginine hydrochloride (2.25% wt/vol) in the drinking water. After 6 weeks of dietary intervention, the left iliac artery of each animal was subjected to a balloon injury. Four weeks later, the iliac arteries were harvested for vascular reactivity studies and immunohistochemical analysis. RESULTS: Vascular injury induced intimal thickening that was largely composed of vascular smooth muscle cells and extracellular matrix. In the setting of hypercholesterolemia, vascular injury induced an exuberant myointimal lesion that was augmented by the accumulation of lipid-laden macrophages. Dietary arginine reduced intimal thickening in the injured vessels of hypercholes-terolemic animals and substantially inhibited the accumulation of macrophages in the lesion (from 28% to 5% of the lesion area, p < 0.001). CONCLUSIONS: We report that lesions induced by vascular injury in hypercholesterolemic animals are markedly reduced by oral administration of arginine. Moreover, we find that the nature of the lesion is altered, with a striking reduction in the percentage of macrophages comprising the lesion.