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Biomedical subjects

Sanjay Rajagopalan

Publications and source records attributed to Sanjay Rajagopalan.

At least 55 records · Page 3Linked to original sources

Hypertension and triglyceride catabolism: implications for the hemodynamic model of the metabolic syndrome.

OBJECTIVE: We sought to determine if hypertensive adults have a blunted triglyceride catabolic rate (TG K(2)) and if related hemodynamic and vascular alterations are determinants of TG K(2). METHODS: Fasting levels of insulin, glucose, lipoproteins and plasma catecholamines were measured in 10 normotensive and 10 hypertensive adults. TG K(2) was determined by an intravenous fat tolerance test. Forearm blood flow, maximum forearm blood flow and minimal forearm vascular resistance were determined by strain gauge plethysmography. Vascular compliance and systemic hemodynamics were measured by computerized arterial pulse waveform analysis. RESULTS: Compared to normotensives, hypertensives had a significantly elevated blood pressure (145 +/- 8/94 +/- 11 versus 111 +/- 15/74 +/- 14 mm Hg, p < 0.001), systemic vascular resistance (1695 +/- 441 versus 1172 +/- 430 dynes x sec x cm(-5), p = 0.02) and reduced large vessel compliance (11.7 +/- 3.6 versus 15.1 +/- 3.1 ml/mm Hg x 100, p = 0.04). There were no significant group differences in TG K(2) (3.07 +/- 2.01 versus 2.88 +/- 2.12 mg/dL/min, p = 0.85) or other metabolic and anthropometric variables. TG K(2) was not predicted by the forearm vascular measures or the hemodynamic variables, but was correlated to waist/hip ratio (r = -0.71, p = 0.001), fasting triglycerides (r = -0.64, p = 0.003), and male gender (r = 0.56, p = 0.012). An enhanced TG K(2) was independently predicted by a reduced small vessel compliance (r = -0.61, p = 0.006). CONCLUSIONS: Elevated blood pressure per se and hypertension-related hemodynamic and vascular alterations are not associated with reduced TG K(2) or other metabolic abnormalities. Rather, aspects of the insulin resistance syndrome are closely related to abdominal adiposity. The independent association between small vessel compliance and TG K(2) deserves further investigation.

Adult↗

Impact of vitamin E on plasma asymmetric dimethylarginine (ADMA) in chronic kidney disease (CKD): a pilot study.

BACKGROUND: Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase and a proposed cardiovascular risk factor, is elevated in chronic kidney disease (CKD). Pharmacological strategies that lower plasma concentration of ADMA may be expected to increase nitric oxide (NO.) bioavailability and potentially limit atherosclerosis. We hypothesized that the antioxidant alpha-tocopherol (vitamin E) reduces ADMA levels in CKD. METHODS: An open-label pilot interventional study using 800 IU of vitamin E was undertaken in eight stable out-patients with non-diabetic CKD (creatinine clearance <30 ml/min/1.73 m(2)) and six healthy controls, with the objective of measuring plasma ADMA levels at baseline and after 8 weeks of treatment. Plasma ADMA, symmetric dimethylarginine (SDMA) and alpha-tocopherol concentrations were determined at study entry and exit using high-performance liquid chromatography, while plasma total F2-isoprostanes, an index of oxidative stress, were measured using a commercially available enzyme-linked immunosorbent assay kit. RESULTS: ADMA and SDMA concentrations were significantly higher in the plasma of patients compared with that of controls (P </= 0.001). After treatment with vitamin E, ADMA decreased by 23% in six of eight patients (P <0.001). The remaining two patients showed either an increase or no change (overall, P = 0.16). There was no significant change in plasma F2-isoprostanes with vitamin E treatment for 8 weeks. CONCLUSIONS: Antioxidant therapy with vitamin E has the potential to lower ADMA levels in CKD patients, implying increased NO. availability. This strategy merits further exploration in the setting of CKD prior to renal replacement.

Adult↗

Adenoviral-mediated gene transfer of vascular endothelial growth factor in critical limb ischemia: safety results from a phase I trial.

Critical limb ischemia (CLI) is typified by rest pain and/or tissue necrosis secondary to advanced peripheral arterial disease (PAD) and is characterized by diminution in limb perfusion at rest. We tested the safety of an angiogenic strategy with CI-1023 (Ad(GV)VEGF121.10), a replication-deficient adenovirus encoding human vascular endothelial growth factor isoform 121 in patients with CLI as part of a phase I trial. Fifteen subjects >35 years of age with CLI and angiographic disease involving the infra-inguinal vessels underwent intramuscular injection of CI-1023 (4 x 10(8) to 4 x 10(10) particle units, n = 13) or placebo (n = 2). All of the patients tolerated the injection well and there were no serious complications related to the procedure. Transient edema was noted in one patient. A total of 79 adverse events were reported over the course of one year. One death (day 136) and one malignancy (day 332) occurred in the CI-1023 group. CI-1023 appears to be well tolerated and safe for single-dose administration in patients with critical limb ischemia due to PAD. Further studies are needed to determine the efficacy of this form of therapeutic angiogenesis.

Adenoviridae↗

Rapid-onset endothelial dysfunction with adriamycin: evidence for a dysfunctional nitric oxide synthase.

Adriamycin (ADR) is a commonly used chemotherapeutic agent that is believed to exert its effects through the generation of oxygen free radicals. We hypothesized that administration of a single dose of ADR results in endothelial nitric oxide synthase (eNOS)-dependent generation of superoxide (O2*-) and acute endothelial dysfunction. A single dose of ADR (10 mg/kg i.v.) administered to rabbits resulted in rapid attenuation of agonist-dependent responses to acetylcholine and calcium ionophore (A23187). In vitro exposure of ring segments to ADR for < 30 min resulted in O2*- generation measured by electron spin resonance (ESR) with the spin trap segments 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) that was abolished by endothelial denudation and incubation with diphenyliodonium (DPI) (10 microM) but not L-NMMA (10 microM). Brachial artery flow-mediated dilation (FMD) in patients undergoing chemotherapy with ADR was markedly attenuated after a single dose of ADR (6.5 +/- 1.0 to 2.5 +/- 1.1% (p = 0.0004, time to end of infusion 27 +/- 8 min) while endothelial-independent dilatation with nitroglycerin was unchanged (16.3 +/- 3.1 and 14.33 +/- 2.1% respectively, p = 0.36). Serum nitrite and nitrate concentrations fell from 50 +/- 6 micromol/l pre-ADR to 33 +/- 6 micromol/l post-ADR infusion (p = 0.0005) while serum concentrations of CD141 thrombomodulin and von Willebrand factor (vWF) activity remained unchanged after ADR infusion (36 +/- 13 to 52 +/- 22% ng/ml versus 3.25 +/- 0.98 to 3.01 +/- 0.91%, respectively, p = NS for pre versus post for both). Doppler indices of diastolic function (IVRT, DT and E/A ratios) were not altered in response to ADR. In conclusion, ADR administration results in rapid depletion of systemic NO* levels and attenuation of agonist-dependent responses in rabbits and flow-mediated dilation in the brachial artery of humans. ESR measurements in rabbit ring suggest an endothelial origin for radical production via flavin-containing oxido-reductases such as eNOS or NADPH cytochrome P450 reductase. These findings may have implications for cardiovascular complications noted with ADR.

Animals↗

Interactive effects of the ACE DD polymorphism with the NOS III homozygous G849T (Glu298-->Asp) variant in determining endothelial function in coronary artery disease.

The products of nitric oxide synthase (NOS) and angiotensin-converting enzyme (ACE) play a critical role in determining vessel wall structure and function. Polymorphisms in both genes have been independently demonstrated to influence propensity to cardiovascular events. The purpose of this study was to determine the influence of the homozygous G849T (Glu298-->Asp) polymorphism in NOS III on peripheral conduit artery endothelial function and to elucidate the modifier role, if any, of a common ACE polymorphism. Three hundred and ninety-seven consecutive subjects presenting to the cardiac catheterization laboratory of the University of Michigan over a period of 18 months were recruited. DNA was extracted and polymerase chain reaction (PCR) analysis for ACE and NOS polymorphisms performed. Patients with homozygosity for G849T at both loci (TT) who belong to DD and II ACE genotype (groups 1 and 2) and those who are negative for this polymorphism (GG) and belong to either DD or II genotype (groups 3 and 4) were identified. The four groups then underwent determination of conduit endothelial function. Heterozygosity of Glu298-Asp or the ID variant of the ACE were not studied. Median FMD value in the TT-DD group was 0.20 (-3.17, 2.01) compared with 2.23% (-0.29, 4.17) in the GG-II group. Median values in the TT-II and the GG-DD groups were 3.04 (-1.16, 6.61) and 2.46% (-1.83, 6.52) respectively. These values were not statistically significant (p > 0.05 by one-way ANOVA). Median nitroglycerin-mediated dilation in the four groups did not differ between the four groups (p = NS by ANOVA). Atherosclerosis burdens as assessed by angiography were not different across the groups. In conclusion, the homozygous NOS III variant (GG) status does not seem to interact additively with the ACE homozygous DD genotype in determining flow-mediated vasodilation in individuals with established atherosclerosis and pre-existent endothelial dysfunction.

Aged↗

Mineralocorticoid receptor blockade: new insights into the mechanism of action in patients with cardiovascular disease.

Mineralocorticoid receptor (MR) blockade is effective in reducing total mortality and the incidence of heart failure in patients with systolic left ventricular dysfunction (SLVD) associated with chronic heart failure or post myocardial infarction. Pre-clinical and clinical studies in SLVD have shown that MR blockade reduces sudden cardiac death, left ventricular remodelling, left ventricular hypertrophy, endothelial dysfunction, autonomic imbalance, renal dysfunction and improves fibrinolysis. While MR blockade promotes sodium excretion and the combination of an angiotensin-converting enzyme inhibitor and a MR blocker have been shown to be more effective than either alone in causing natriuresis, it is unlikely that their beneficial effects can be explained solely on this basis. Aldosterone has been shown to have a number of adverse effects, including activation of other neurohumeral mediators, stimulation of active reactive oxygen species (ROS), activation of the NF-Greek small letter kappa kappabeta and AP-1 signalling pathways, vascular inflammation and fibrosis, myocardial hypertrophy, autonomic imbalance, and a decrease in fibrinolysis. MR blockade is, however, effective both in situations with and without an increase in serum aldosterone level, since the MR can be occupied and activated by cortisol as well as by aldosterone. In view of these mechanisms, MR blockade may play an important role not only on SLVD, but also in essential hypertension with normal systolic function, diastolic heart failure, valvular heart disease, vascular stiffening with ageing, progression of renal disease, and diabetes mellitus. This hypothesis will, however, require further prospective evaluation.

Animals↗

Calf flow reserve with H(2)(15)O PET as a quantifiable index of lower extremity flow.

UNLABELLED: Objective measures of recruitable blood flow are of importance in angiogenesis trials. We validated a new PET-derived flow reserve (FR) measurement in healthy subjects and subjects with peripheral artery disease (PAD). METHODS: Five healthy volunteers and 5 subjects with PAD underwent cannulation of the femoral artery and vein. Basal and maximal flow (100 micro g/kg/min of adenosine infused intraarterially) in the lower extremity was determined using thermodilution (TD) techniques. Subjects then underwent plethysmography (PL) followed by PET measurements of blood flow at the calf level. For the PET studies, a transmission scan followed by injection of 1.85 GBq (50 mCi) H(2)(15)O and dynamic scanning for 5 min were acquired in five 1-min frames. Regions of interest were drawn on successive PET image slices, and radioactivity was quantified from the first-minute scan after injection. FR for each of the 3 modalities was expressed as the ratio of adenosine to basal flow. RESULTS: PET-derived FR correlated strongly with TD (r = 0.82; P = 0.004) but not with PL (r = 0.17; P = 0.85). The mean average difference in FR between healthy volunteers and PAD subjects was 13.0 with PET and 4.5 with TD. The intra- and intersubject variability for PET expressed as the coefficient of variation was 10.5% and 29.0% for healthy subjects and 7.0% and 52.9% in PAD, respectively. CONCLUSION: As expected, FR was significantly lower in PAD subjects compared with healthy subjects as assessed with TD and PET but not with PL. PET-derived FR appears to be reproducible and generates sharper and higher indices of recruitable flow in healthy subjects and PAD. These findings have implications for the use of PET-derived FR as a sensitive index of recruitable flow in angiogenesis trials.

Adenosine↗

Altered tetrahydrobiopterin metabolism in atherosclerosis: implications for use of oxidized tetrahydrobiopterin analogues and thiol antioxidants.

OBJECTIVE: Tetrahydrobiopterin (BH4) is of fundamental importance for the normal function of endothelial NO synthase. The purpose of this study was to investigate the effects of hyperlipidemia on vascular BH4 levels and the effect of supplementation with sepiapterin in the presence and absence of N-acetylcysteine (NAC). METHODS AND RESULTS: New Zealand White rabbits were fed normal chow (normocholesterolemic [NC] group) or hyperlipidemic chow (hyperlipidemic [HL] group) for 8 to 10 weeks. Mean cholesterol levels were 1465+/-333 and 53+/-17 mg/dL in the HL and NC group, respectively. Markedly diminished BH4 levels were found in the HL group compared with the NC group, but these levels could be restored after 6 hours of incubation with sepiapterin. Peak relaxations to acetylcholine and A23187 were impaired in the HL group. Supplementation with sepiapterin resulted in a further diminution of relaxation in the HL but not NC group. Incubation with NAC for 6 hours failed to raise BH4 levels, whereas NAC in conjunction with sepiapterin raised BH4 levels approximately 221-fold. However, this increase did not improve relaxations to A23187 and acetylcholine. CONCLUSIONS: Prolonged exposure to sepiapterin impairs vasorelaxation in hyperlipidemia despite repletion of endogenous BH4. Antioxidant thiols do not correct this impairment. These studies have implications for the use of sepiapterin in the correction of vasomotor tone in atherosclerosis.

Acetylcholine↗

Phase I study of direct administration of a replication deficient adenovirus vector containing the vascular endothelial growth factor cDNA (CI-1023) to patients with claudication.

The long-term safety and efficacy of adenoviral delivery of growth factors in patients with peripheral arterial disease (PAD) is unknown. CI-1023 (Ad(GV)VEGF(121.10)) is a replication-deficient adenovirus encoding human vascular endothelial growth factor isoform 121. In this phase I trial, we investigated the safety and efficacy of CI-1023 in subjects with advanced claudication symptoms secondary to infra-inguinal disease. Eighteen subjects >35 years of age with a median ankle brachial index (ABI) at rest of 0.525 (interquartile range 0.4) and angiographic disease involving the infra-inguinal vessels underwent intramuscular injection of CI-1023 (4 x10(8) to 4 x10(10) particle units, n = 15) or placebo (n = 3). Eleven of 15 patients (73%) who received CI-1023 and 1 of 3 subjects (33%) who received placebo, completed 1 year of follow-up. Edema and rash were the most common early adverse event. One infra-inguinal bypass procedure occurred in each of the placebo and CI-1023 groups at days 29 and 104, respectively. One death (day 160) and 1 malignancy (day 274) occurred in the CI-1023 group. Conclusions on efficacy could not be made due to the small number of patients. However, there were encouraging trends in ABI at rest and peak walking time at follow-up.

Adenoviridae↗

Mineralocorticoid receptor antagonism in experimental atherosclerosis.

BACKGROUND: Aldosterone has been implicated in the effects of angiotensin II in the vasculature. We hypothesized that there is local expression of the mineralocorticoid receptor (MR) in the vasculature and that the use of a selective aldosterone receptor antagonist (SARA) improves endothelial function in early atherosclerosis. METHODS AND RESULTS: New Zealand rabbits were placed on normal chow or 1% cholesterol diets, randomized to placebo or SARA (eplerenone, 50 mg/kg twice daily), and killed at the end of 6 weeks for various studies. In the hyperlipidemic (HL) chow group, there was a 2.3-fold increase in superoxide (O2*-)) generation. SARA normalized O2*- generation in intact aortas and reduced NADH and NADPH oxidase activity to basal levels (0.31+/-0.04 and 0.27+/-0.02 in HL versus 0.16+/-0.05 and 0.07+/-0.02 in HL-SARA, respectively; P<0.01 by ANOVA). This was associated with improvements in peak relaxations to the endothelial-dependent agonist acetylcholine (82+/-6% in HL-SARA versus 61+/-4 in HL; P<0.01 by ANOVA; ED(50) 6.8x10(-8) mol/L in HL-SARA and 1.2x10(-7) mol/L in HL; P=NS) to near-normal levels. Vessels from the HL group demonstrated hyperreactivity to angiotensin II that could not be corrected with SARA. Plasma aldosterone levels by radioimmunoassay demonstrated a 4- to 5-fold increase in response to SARA but no differences with lipid feeding. Real-time reverse transcriptase-polymerase chain reaction studies revealed expression of MR in the aorta of HL rabbits and those of controls. CONCLUSIONS: MR antagonism improves endothelial function and reduces O2*- generation in diet-induced atherosclerosis. Targeting aldosterone by blocking its receptor has potential antiatherosclerotic effects.

Animals↗

Inhalation of fine particulate air pollution and ozone causes acute arterial vasoconstriction in healthy adults.

BACKGROUND: Fine particulate air pollution and ozone are associated with increased cardiovascular events. To help explain the mechanism behind these observations, we investigated the effect of air pollution exposure on vascular function. METHODS AND RESULTS: Twenty-five healthy adults underwent a randomized, double-blind, crossover study comparing the vascular response to the 2-hour inhalation of approximately 150 microg/m(3) of concentrated ambient fine particles (CAP) plus ozone (120 ppb) versus the response to the inhalation of filtered air. High-resolution vascular ultrasonography was used to measure alterations in brachial artery diameter, endothelial-dependent flow-mediated dilatation (FMD) and endothelial-independent nitroglycerin-mediated dilatation (NMD). Exposure to CAP plus ozone caused a significant brachial artery vasoconstriction compared with filtered air inhalation (-0.09+/-0.15 mm versus +0.01+/-0.18 mm, P=0.03). There were no significant differences in FMD (+0.29+/-4.11% versus -0.03+/-6.63%, P=0.88), NMD (+3.87+/-5.43% versus +3.46+/-7.92%, P=0.83), or blood pressure responses between exposures. CONCLUSIONS: Short-term inhalation of fine particulate air pollution and ozone at concentrations that occur in the urban environment causes acute conduit artery vasoconstriction.

Adult↗

Effect of losartan in aging-related endothelial impairment.

Aging is associated with progressive deterioration in endothelial function. We hypothesized that losartan may represent a useful therapeutic strategy to ameliorate endothelial function in aged subjects. Eighteen healthy older subjects (mean age 75 +/- 3 years) were prospectively randomized in a double-blind, crossover fashion to receive either losartan 50 mg/day or placebo for 6 weeks. Subjects were switched to the opposite arm after a 2- week washout period. Flow-mediated dilation (FMD) in the brachial artery and plasma levels of vascular cell adhesion molecule-1, intercellular adhesion molecule (ICAM), moncocyte chemoattractant 1 protein, and E-selectin were measured in both arms at the beginning and end of the 6-week period. Losartan resulted in a 6-mm Hg decrease in systolic blood pressure (from 130 +/- 12 to 124 +/- 13 mm Hg), which was no different from placebo (132 +/- 12 to 127 +/- 13 mm Hg). FMD increased from 3.1 +/- 0.6% to 3.9 +/- 0.6% after losartan, and decreased from 3.3 +/- 0.3% to 2.4 +/- 0.6% after placebo (p = NS for both). In contrast, losartan reduced circulating concentrations of vascular cell adhesion molecule 1 (750 +/- 73 to 572 +/- 39), ICAM (405 +/- 26 to 196 +/- 10), and moncocyte chemoattractant 1 protein (560 +/- 56 to 423 +/- 35) (p <0.01 for all by analysis of variance), but not E-selectin. On univariate analyses, the strongest predictor of baseline endothelial function and change in FMD with losartan was low-density lipoprotein. There was a negative correlation between baseline endothelial function and change in FMD in response to losartan (r(2) = -0.75, p = 0.0003). Baseline ICAM levels alone significantly correlated with low-density lipoprotein cholesterol (r(2) = 0.54, p = 0.02) and weakly correlated with total cholesterol (r(2) = 0.47, p = 0.05). Thus, administration of losartan for a duration of 6 weeks has favorable effects on inflammatory markers in healthy older subjects, but does not alter peripheral conduit endothelial function.

Aged↗

Carotid stenosis: medical and surgical aspects.

Medical treatment for carotid disease is similar to the treatment of atherosclerosis, with some recent data suggesting that there is a benefit to an aspirin-dipyridamole combination. CEA has revolutionized the treatment of symptomatic and asymptomatic carotid stenosis. This approach remains the gold standard for the surgical treatment of carotid artery stenosis, against which emerging modalities such as percutaneous carotid stenting should be compared. Higher-risk, asymptomatic patients can safely undergo CEA in high-volume centers for stenosis greater than 80% as defined by ultrasound.

Carotid Stenosis↗

Upper extremity arterial disease.

Upper extremity arterial disease is much less common than lower extremity involvement and typically presents as arm claudication, Raynaud's syndrome, rest pain, ischemic ulcerations, or gangrene. The disease can reflect an underlying systemic disorder. In addition to clinical examination, diagnostic studies include noninvasive vascular studies, serologic, immunologic, and hematologic studies (when indicated), and selective arteriography. Atherosclerotic disease is the most common cause of large vessel obstruction, but it can also cause small vessel obstruction by atheromatous embolization or thromboembolism. Treatment varies from pharmacological therapy for vasospastic and vasculitic syndromes to operative approaches for endarterectomy or bypass of focal lesions. Angioplasty and stent techniques also can provide an effective treatment option.

Arm↗

Magnetic resonance angiographic techniques for the diagnosis of arterial disease.

Magnetic resonance angiography (MRA) techniques use inherent magnetization properties of tissues in combination with pharmacologic contrast agents, such as gadolinium, that shorten T1 relaxation time. The availability of powerful magnetic field gradients along with a variety of post-processing algorithms make MRA possible. MRA is widely used for the diagnosis of disease in a variety of vessels, including aorta, carotids, renals, mesenteric, and peripheral vessels. Performance of high-quality 3D contrast MRA requires appropriate understanding of MRA methodologies, including the critical dependence of bolus timing and ways to optimize it. Additionally, recognition of artifacts and learning to avoid them is important.

Aorta, Abdominal↗

Management of intermittent claudication.

Medical management of PAD is a considerable challenge. Although patients typically present with IC, there is a substantial pool of subclinical PAD patients. PAD, whether symptomatic or not, confers a marked cardiovascular risk; with affected patients dying of heart attack or stroke, identification of index patients and aggressive medical treatment can offer health benefits far in excess of improvement in IC or related symptoms. Management of risk factors, lifestyle interventions, and pharmacologic treatment with agents to provide symptomatic relief have a central role in improving function and quality of life and slowing the progression to advanced endpoints, such as the rest pain, nonhealing ulcers, gangrene, and cardiac death. Surgical or percutaneous revascularization for aorto-iliac disease provides durable treatment for individuals with disabling symptoms. Newer treatments, such as angiogenic growth factor treatments, are being tested in clinical trials and seem promising. There are limited treatment choices for individuals with predominant infra-popliteal disease. In the future, the availability of newer stents and therapies to prevent re-stenosis may extend the applicability of endovascular treatment to difficult-to-treat infra-inguinal lesions.

Disease Susceptibility↗

Management of chronic critical limb ischemia.

The patient with CLI is challenging and requires a multi-disciplinary approach to effective management that involves a team of individuals proficient in various aspects of vascular disease. Fig. 4 details the approach at the University of Michigan's comprehensive vascular medicine program.

Algorithms↗

Circadian blood pressure overswinging in a physically fit, normotensive African American woman.

Ambulatory blood pressure (BP) and heart rate (HR) were measured in a physically fit, normotensive postmenopausal African American woman, before and after 15 weeks of aerobic training. Mean BP, HR, and HR variability were normal at the outset and were further improved by training. Training had no effect on circadian BP variation, which exceeded gender- and age-specified limits, indicative of circadian hyperamplitude tension (CHAT). A 12-week treatment with the beta1-adrenoceptor blocker atenolol, 14 months post-training, normalized CHAT and HR variability and further reduced BP and HR. These results suggest beta1-adrenergic mediation of CHAT and its refractoriness to exercise training.

Adrenergic beta-Antagonists↗