Mineralocorticoid receptor antagonism attenuates cardiac hypertrophy and prevents oxidative stress in uremic rats

Chronic renal failure causes left ventricular hypertrophy, but the molecular mechanisms involved remain unknown. We, therefore, investigated whether the mineralocorticoid receptor is implicated in the cardiac hypertrophy observed in uremic rats and whether mineralocorticoid receptor blockade could be protective in chronic renal failure. Experimental groups were: control rats, uremic rats (NPX) with 5/6 nephrectomy (5 weeks), and NPX rats fed with spironolactone for 5 weeks. Systolic blood pressure was increased in both NPX rats and NPX rats fed with spironolactone for 5 weeks. Echocardiography revealed concentric left ventricular hypertrophy in uremia, which was attenuated by spironolactone. Enlarged cardiomyocyte size was observed in both left and right ventricles of NPX rats, an effect that was prevented by spironolactone. Mineralocorticoid receptor antagonism attenuated the increase of ventricular brain natriuretic peptide mRNA levels induced by nephrectomy. Left ventricular gene expressions of aldosterone synthase, mineralocorticoid receptor, and hydroxysteroid dehydrogenase type 2 were the same in the 3 groups, whereas gene expression of the glucocorticoid receptor was significantly diminished in chronic renal failure rats. No significant differences in cardiac aldosterone were observed between control rats and NPX rats, although NPX rats fed with spironolactone for 5 weeks showed increased plasma aldosterone levels. However, a significant increase in serum and glucocorticoid-inducible kinase-1 mRNA expression and protein was present in the NPX group; spironolactone treatment significantly reduced serum and glucocorticoid-inducible kinase-1 mRNA and protein in the left ventricle. Uremic rats exhibited a significant increase of superoxide production and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunits expression (NOX-2, NOX-4, and p47(phox)) in the left ventricle, which was prevented by the mineralocorticoid receptor antagonist. Our findings provide evidence of the beneficial effects of spironolactone in cardiac hypertrophy and cardiac oxidative stress in chronic renal failure.     

Prevention of disabling and fatal strokes by successful carotid endarterectomy in patients without recent neurological symptoms: randomized controlled trial. MRC asymptomatic carotid surgery trial (ACST) collaborative group. Lancet 2004; 363: 1491-502

QUESTION: Is carotid endarterectomy (CEA) an effective and safe treatment for the prevention of stroke among patients with >60% internal carotid artery stenosis who had no neurologic symptoms in the previous 6 months. POPULATION: Men and women with severe (>60%) unilateral or bilateral carotid artery stenosis not associated with neurologic symptoms in the past 6 months, where both doctor and patient were uncertain whether to choose or to defer immediate CEA. DESIGN AND METHODS: During 1993-2003, 3120 asymptomatic patients with >60% carotid stenosis were randomized equally to immediate CEA versus indefinite deferral of CEA, and were followed for up to 5 years. The primary end point was risk of stroke or death at 5 years. Analysis was by intention to treat. The treatment of patients with antiplatelet agents, antihypertensive and lipid-lowering therapies was left to the discretion of the clinician. RESULTS: Among patients randomized to immediate CEA (50% had CEA by 1 month, 88% by 1 year) versus deferred, the incidence of stroke or death at 5 years was 6.4% versus 11.8% (95% CI: 3.0-7.7, p < 0.0001); 3.5% versus 6.1% for fatal or disabling strokes (95% CI: 0.8-4.3, p = 0.004), and 2.1% versus 4.2% for fatal strokes (95% CI: 0.6-3.6, p = 0.006). The perioperative stroke incidence was marginally higher in the delayed group versus the immediate group (4.5% versus 2.8%) and overall the risk per CEA of perioperative stroke or death was 3.1%. After excluding the perioperative events from the analysis, the 5-year stroke risks were 3.8% versus 11% (95% CI: 5.0-9.4], p < 0.0001). Surgery primarily prevented carotid territory ischemic strokes (2.7% vs 9.5%; gain 6.8% [4.8-8.8], p < 0.0001). The impact of immediate surgery was consistent in all age groups, among men and women, and across the spectrum of carotid stenosis (i.e. 70%, 80% and 90% carotid stenosis). CONCLUSION: In asymptomatic patients younger than 75 years of age with carotid stenosis of 70% or more on ultrasound, immediate CEA reduces the 5-year incidence of stroke and death.     

Management of risk in peripheral artery disease: recent therapeutic advances

Peripheral artery disease (PAD) is a problem frequently encountered by physicians who care for patients with coronary heart disease, diabetes mellitus, renal insufficiency, congestive heart failure, or stroke. Patients with PAD are at heightened risk of myocardial infarction and stroke and are 6 times more likely to die of cardiovascular causes than persons without the disease. There is an urgent need for therapies that reduce the incidence of vascular complications among patients with PAD. In recent years, a number of risk-lowering therapies have been validated by randomized controlled trials enrolling large numbers of patients with PAD. The available evidence supports aggressive lifestyle modification as well as the provision of an antiplatelet agent, an HMGCoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitor, and an angiotensin-converting enzyme inhibitor for cardiovascular protection in patients with PAD. As a result of their high baseline risk and the proven effectiveness of these interventions, most patients with PAD will benefit substantially from aggressive medical therapy.     

Recombinant human hepcidin expressed in Escherichia coli isolates as an iron containing protein

Hepcidin is a small peptide that acts as a regulator of systemic iron homeostasis. To study some of its functional properties, a synthetic cDNA for the minimal, 20-amino-acid, form of human hepcidin was cloned into different constructs for expression in Escherichia coli. The fusion ferritin-hepcidin produced molecules retaining most of ferritin structural and functional properties, including ferroxidase and iron incorporation activities. However, it showed spectroscopic properties compatible with the presence of iron-sulfur complexes on the hepcidin moiety, which was buried into protein cavity. Similar complexes were reconstituted by in vitro incubation of the iron-free protein with iron and sulfide salts. Two other unrelated fusion products were constructed, which, when expressed in E. coli, formed insoluble aggregates retaining a large proportion of total bacterial iron. Analysis of the solubilized preparations showed them to contain iron-sulfur complexes. We concluded that the cysteine-rich hepcidin acts as an iron-sequestering molecule during expression in E. coli. This may have implications for the biological functions of this key protein of iron metabolism.     

Exhaled nitric oxide and bronchial responsiveness to adenosine 5'-monophosphate in subjects with allergic rhinitis

STUDY OBJECTIVES: To determine differences in exhaled nitric oxide (ENO) between subjects with allergic rhinitis with and without increased responsiveness to direct and indirect bronchoconstrictor agents. STUDY DESIGN: Cross-sectional study with the order of challenge tests randomized. SETTING: Specialist allergy unit in a university hospital. PATIENTS: Thirty-eight subjects without asthma with allergic rhinitis and 10 healthy nonatopic control subjects. MEASUREMENTS AND RESULTS: Participants were challenged with increasing concentrations of adenosine 5'monophosphate (AMP) and methacholine. ENO was measured with the single-exhalation method. A positive response to both bronchoconstrictor agents was detected in nine subjects with allergic rhinitis, whereas four subjects showed increased responsiveness to AMP but not to methacholine. The geometric mean (range) ENO values were significantly higher in subjects with allergic rhinitis with increased responsiveness to either methacholine or AMP than in subjects with normal responsiveness to both agonists: 51.3 parts per billion (ppb) [22.0 to 108.5 ppb] vs 25.1 ppb (5.7 to 102.9 ppb, respectively; p = 0.007) and healthy control subjects (11.2 ppb [5.0 to 31.9 ppb], p < 0.001). Subjects with allergic rhinitis with normal responsiveness to both agonists also had higher concentrations of ENO than healthy control subjects (p = 0.007). No correlation was found between ENO and either of the provocative concentrations of methacholine or AMP causing a 20% fall in FEV(1). CONCLUSIONS: In subjects without asthma but with allergic rhinitis, the presence of bronchoconstriction in response to methacholine or AMP is associated with increased ENO concentrations. However, elevated concentrations of ENO are detected even in subjects with allergic rhinitis without airway hyperresponsiveness. These results suggest that the presence of airway hyperresponsiveness is not the only factor that determines the increased NO levels detected in subjects with allergic rhinitis.     

Percutaneous suture-mediated closure of femoral access sites deployed through the procedure sheath: initial clinical experience with a novel vascular closure device.

The objective of this study was to assess the initial safety and feasibility of a novel suture-mediated device for closure of femoral access sites immediately after diagnostic or interventional cardiac catheterization. In a prospective study, 150 patients (mean age, 61.5 years; 109 male) underwent femoral access closure with a novel suture closure device (Superstitch, Sutura) immediately after diagnostic (n = 106) or interventional (n = 44) catheterization procedures, independently of the coagulation status. All patients were monitored for 24 hr after the procedure. The closure device was successfully deployed in 92% of patients. Immediate hemostasis was achieved in 77% of patients with no differences between patients undergoing diagnostic catheterization or coronary interventions (79% vs. 73%; P = 0.659). After 2 min of additional light manual compression, hemostasis was achieved in 92% of patients. There was one major complication requiring vascular surgery (0.7%). The novel suture closure device is a safe and effective device that allows for immediate closure of femoral puncture sites after both diagnostic and interventional procedures with a low rate of major complications.     

Polymorphism G80A in the reduced folate carrier gene and its relationship to methotrexate plasma levels and outcome of childhood acute lymphoblastic leukemia

Methotrexate (MTX) is a key compound of chemotherapeutic regimens used in the treatment of childhood acute lymphoblastic leukemia (ALL). Resistance to this drug may arise by, among other factors, altered cellular uptake that may hamper the efficacy of the treatment. Recently, a G(80)A polymorphism has been described in the reduced folate carrier gene (RFC1), which encodes the major MTX transporter. Here, we assessed the association between the genetic polymorphisms G(80)A and both MTX plasma levels and childhood ALL outcome. Children with the A(80) variant had worse prognoses than patients with the GG genotype (P =.04), as shown by event-free survival estimates. Patients homozygous for A(80) had higher levels of MTX (P =.004) than the other genotype groups. Possible explanations for observed associations are discussed; however, additional experiments are required to achieve understanding of the underlying mechanism.     

Rosiglitazone enhances glucose tolerance by mechanisms other than reduction of fatty acid accumulation within skeletal muscle

We hypothesized that improved glucose tolerance with rosiglitazone treatment would coincide with decreased levels of i.m. triacylglycerol (IMTG), diacylglycerol, and ceramide. Obese Zucker rats were randomly divided into two experimental groups: control (n = 9) and rosiglitazone (n = 9), with lean Zucker rats (n = 9) acting as a control group for obese controls. Rats received either vehicle or 3 mg/kg rosiglitazone for 6 wk. Glucose tolerance was impaired (P < 0.01) in obese compared with lean rats, but was normalized after rosiglitazone treatment. IMTG content was higher in obese compared with lean rats (70.5 +/- 5.1 vs. 27.5 +/- 2.0 micromol/g dry mass; P < 0.05) and increased an additional 30% (P < 0.05) with rosiglitazone treatment. Intramuscular fatty acid composition shifted toward a higher proportion of monounsaturates (P < 0.05) in obese rosiglitazone-treated rats due to an increase in palmitoleate (16:1; P < 0.05). Rosiglitazone treatment increased (P < 0.05) skeletal muscle diacylglycerol and ceramide levels by 65% and 100%, respectively, compared with obese rats, but elevated muscle diacylglycerol was not associated with changes in the total or membrane contents of the diacylglycerol-sensitive protein kinase C isoforms theta;, delta, alpha, and beta. In summary, we observed a disassociation among skeletal muscle IMTG, diacylglycerol and ceramide content, and glucose tolerance with rosiglitazone treatment in obese Zucker rats. Our data suggest, therefore, that rosiglitazone enhances glucose tolerance by mechanisms other than reduction of fatty acid accumulation within skeletal muscle.     

Defective activation of skeletal muscle and adipose tissue lipolysis in type 1 diabetes mellitus during hypoglycemia

The increased risk of hypoglycemia during intensified treatment of type 1 diabetes mellitus (T1DM) patients, who have a deficient glucagon secretory response, is largely attributed to the development of suppressed adrenomedullary responses. A consequence of this impairment of catecholamine secretion might be reduced lipolysis in major target tissues (muscle and adipose) and, in turn, increased glucose metabolism. To test this hypothesis, we used microdialysis to monitor glycerol (index of lipolysis) in the extracellular fluid of skeletal muscle and adipose tissue and assessed whole-body glucose use by measuring [6,6-(2)H(2)]glucose enrichment in plasma in seven intensively treated T1DM patients and eight nondiabetic subjects who received a 3-h insulin infusion (0.8 mU/kg.min) on two occasions: during mild-moderate hypoglycemia or euglycemia. In the hypoglycemic study, the rise in plasma epinephrine was approximately 50% less in the T1DM patients despite a greater fall in plasma glucose (to 3.0 vs. 3.5 mM in controls; P < 0.05). Moreover, the rate of glucose flux and the plasma-extracellular fluid glucose gradient in muscle was increased during hypoglycemia in T1DM subjects compared with controls. Glycerol levels in muscle, adipose, and plasma fell similarly in both groups in the first hour. Thereafter, tissue glycerol remained suppressed in the T1DM patients but rebounded significantly (P < 0.01) in the control subjects. The glycerol response in muscle and adipose tissue was significantly correlated with plasma epinephrine concentration (r = 0.73, P = 0.002; and r = 0.52, P = 0.04, respectively), and inversely correlated with whole-body glucose disposal (r = -0.51, P = 0.05; and r = -0.50, P = 0.05). To determine whether the absence of the lipolytic response is limited to deficient catecholamine release, we perfused muscle and adipose tissue in situ with the selective beta(2)-agonist terbutaline during hyperinsulinemic euglycemia. Local addition of agonist increased glycerol and blood flow in both muscle and adipose (P < 0.01 and P < 0.05, respectively) similarly in T1DM and control subjects. We conclude that deficient release of (rather than impaired responsiveness to) catecholamines in T1DM prevents the local fat breakdown within muscle and adipose tissue that normally occurs during mild-moderate hypoglycemia. This defect within peripheral tissues may lead to a delayed increase in glucose disposal that could contribute to the severity of hypoglycemia when it is prolonged.