Bioequivalence and food effect of a fixed-dose combination of macitentan and tadalafil: Adaptive design in the COVID-19 pandemic

The COVID‐19 pandemic has forced clinical studies to accommodate imposed limitations. In this study, the bioequivalence part could not be conducted as planned. Thus, the aim was to demonstrate bioequivalence, using an adaptive study design, of tadalafil in fixed‐dose combination (FDC) tablets of macitentan/tadalafil with single macitentan and tadalafil (Canadian‐sourced) tablets and assess the effect of food on FDC tablets in healthy subjects. This Phase 1, single‐center, open‐label, single‐dose, two‐part, two‐period, randomized, crossover study enrolled 62 subjects. Tadalafil bioequivalence as part of FDC of macitentan/tadalafil (10/40 mg) with single‐component tablets of macitentan (10 mg) and tadalafil (40 mg) was determined by pharmacokinetic (PK) assessment under fasted conditions. The effect of food on FDC was evaluated under fed and fasted conditions. Fasted 90% confidence intervals (CIs) for geometric mean ratios (GMRs) were within bioequivalence limits for tadalafil and macitentan. Fed and fasted 90% CIs for area under the curve (AUC) GMR were within bioequivalence limits. However, 90% CIs for maximum plasma concentration (C_max) GMR for macitentan and tadalafil were outside bioequivalence limits. One FDC‐treated subject experienced a serious adverse event of transient ischemic attack (bioequivalence part). To address pandemic‐imposed limitations, an adaptive study design was implemented to demonstrate that the FDC tablet was bioequivalent to the free combination of macitentan and tadalafil (Canadian‐sourced). No clinically significant differences in PK were determined between fed and fasted conditions; the FDC formulation could be taken irrespective of meals. The FDC formulation under fasted and fed conditions was well tolerated with no clinically relevant differences in safety profiles between the treatment groups.

NCT Number: NCT04235270.

Diagnostic delay and characterization of the clinical prodrome in AL amyloidosis among 1523 US adults diagnosed between 2001 and 2019

Light-chain (AL) amyloidosis is a multisystem disorder with a high early mortality and diagnostic delays of >1 year from symptom onset. This retrospective observational study sought to characterize the clinical prodrome and diagnostic delay to inform early detection. We identified 1523 adults with newly diagnosed AL amyloidosis in the Optum de-identified Clinformatics^® Datamart US healthcare claims database as those with ≥2 new diagnosis codes for AL or other amyloidosis in 90 days with ≥1 multiple myeloma treatment within 730 days, excluding patients with prior hereditary or secondary amyloidosis and Familial Mediterranean Fever. We considered 34 signs/symptoms using diagnosis codes in all observable time on or before AL amyloidosis diagnosis. Sign/symptom prevalence was compared to that of 1:4 matched population controls. The overlap and sequence of signs/symptoms and the median time from first sign/symptom to AL amyloidosis diagnosis were explored. Healthcare utilization was summarized. The most common individual AL amyloidosis signs/symptoms were malaise/fatigue (61%) and dyspnea (59%). Cardiac signs/symptoms were observed in 77% of patients, followed by renal (62%) and neurologic (59%) signs/symptoms. Multisystem involvement (≥3 systems) was present in 54%. Monoclonal gammopathy was detected in 29% before diagnosis. Median time from symptom onset to AL amyloidosis diagnosis was 2.7 years. Healthcare utilization was high between first AL amyloidosis signs/symptoms and diagnosis, with 50% visiting ≥5 physician types. AL amyloidosis patients have a lengthy and complex clinical prodrome. Novel approaches to early diagnosis are needed to improve outcomes.

Safety and Pharmacokinetics of DS-1040 Drug-Drug Interactions With Aspirin, Clopidogrel, and Enoxaparin

DS-1040, a novel low-molecular-weight inhibitor of activated thrombin-activatable fibrinolysis inhibitor, is under development for the treatment of thromboembolic diseases including venous thromboembolism and acute ischemic stroke. Here we describe the results of 3 studies that evaluated the safety and tolerability of DS-1040 along with the effect on DS-1040 pharmacokinetic (PK) parameters, when dosed alone or when coadministered with aspirin (NCT02071004), clopidogrel (NCT02560688), or enoxaparin in healthy subjects. Concomitant administration of single-dose DS-1040 with multiple-dose aspirin, multiple-dose clopidogrel, or single-dose enoxaparin, consistent with clinically relevant dose regimens, was safe and well tolerated with no serious treatment-emergent adverse events (TEAEs), TEAEs leading to discontinuation, bleeding-related TEAEs, and no significant changes in coagulation parameters. DS-1040 did not prolong bleeding time when administered concomitantly with aspirin or clopidogrel. In the aspirin study, DS-1040 PK was evaluated following the concomitant administration with multiple-dose aspirin, where the plasma DS-1040 exposure (peak plasma concentration [C_max ] and area under the concentration-time curve [AUC_inf ]) was to be similar to the data previously published in the first-in-human study of DS-1040 in healthy subjects. The PK parameters of DS-1040 coadministered with clopidogrel were similar to those of DS-1040 alone, with small increases in geometric means for C_max (7%) and AUC_last (9%). When coadministered with enoxaparin, the PK parameters of DS-1040 were not affected (1.1% and 1.5% decreases in geometric means for C_max and AUC_last , respectively). Therefore, concomitant administration of DS-1040 and clopidogrel or enoxaparin did not demonstrate PK drug-drug interactions.

First-in-Human Study to Assess the Safety, Pharmacokinetics, and Pharmacodynamics of an Oral Formulation of DS-1040, an Inhibitor of the Activated Form of Thrombin-Activatable Fibrinolysis Inhibitor, in Healthy Subjects

DS-1040, a low-molecular-weight imidazole derivative, inhibits the enzymatic activity of thrombin-activatable fibrinolysis inhibitor (TAFIa), enhancing endogenous tissue plasminogen activator-triggered fibrinolysis. This first-in-human, randomized, placebo-controlled, phase 1 study evaluated the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of an oral formulation of DS-1040. Healthy adults (aged 20-45 years; N = 56) were randomized 3:1 to receive DS-1040 orally administered as single ascending doses (50, 100, 200, or 400 mg) or placebo, or DS-1040 multiple ascending doses (100 mg once daily, 200 mg once daily, or 150 mg twice daily) or placebo for 14 days. Safety, PK, and PD parameters were assessed. All doses of DS-1040 were well tolerated; no serious/severe adverse events (AEs) or discontinuations due to AEs occurred. DS-1040 had no effect on coagulation parameters, and no treatment-related trends in the bleeding time were observed. DS-1040 exposure (peak concentration and area under the concentration-time curve) increased in a dose-proportional manner across the single-dose range. With multiple doses, steady state was achieved by day 7 with minimal accumulation (mean accumulation ratio 1.15-1.25), and the PK was time-independent. After 72 hours, approximately 10% of the DS-1040 400-mg single dose was recovered in urine as intact parent drug. The mean terminal half-life ranged from 17.2 to 24.9 hours, which was similar to previous intravenous administration data. Dose-dependent inhibition of total TAFIa activity was observed following single and multiple doses of oral DS-1040. The safety and PK/PD profiles of oral DS-1040 in healthy subjects support further clinical development.

Coadministration of probenecid and cimetidine with mirogabalin in healthy subjects: A phase 1, randomized, open-label, drug-drug interaction study

AIMS

The primary aim of this study was to assess the individual effects of probenecid and cimetidine on mirogabalin exposure.

METHODS

This phase 1, open-label, crossover study randomized healthy adults to receive three treatment regimens, each separated by ≥5-day washout: a single oral dose of mirogabalin 15 mg on day 2, mirogabalin 15 mg on day 2 plus probenecid 500 mg every 6 h from days 1 to 4, and mirogabalin 15 mg on day 2 plus cimetidine 400 mg every 6 h from days 1 to 4.

RESULTS

Coadministration of mirogabalin with probenecid or cimetidine increased the maximum and total mirogabalin exposure. The geometric mean ratios of Cmax and AUC(0-t) (90% CI) with and without coadministration of probenecid were 128.7% (121.9-135.7%) and 176.1% (171.9-180.3%), respectively. The geometric mean ratios of Cmax and AUC(0-t) (90% CI) with and without coadministration of cimetidine were 117.1% (111.0-123.6%) and 143.7% (140.3-147.2%), respectively. Mean (standard deviation) renal clearance of mirogabalin (l h-1 ) was substantially slower after probenecid [6.67 (1.53)] or cimetidine [7.17 (1.68)] coadministration, compared with mirogabalin alone [11.3 (2.39)]. Coadministration of probenecid or cimetidine decreased mirogabalin mean (standard deviation) apparent total body clearance [10.5 (2.33) and 12.8 (2.67) l h-1 , respectively, vs. 18.4 (3.93) for mirogabalin alone].

CONCLUSIONS

A greater magnitude of change in mirogabalin exposure was observed when coadministered with a drug that inhibits both renal and metabolic clearance (probenecid) vs. a drug that only affects renal clearance (cimetidine). However, as the increase in exposure is not clinically significant (>2-fold), no a priori dose adjustment is recommended.

Tolerability, pharmacokinetics, and pharmacodynamics of mirogabalin in healthy subjects: Results from phase 1 studies

Three phase 1 pharmacokinetic (PK)/pharmacodynamics (PD) studies were conducted in healthy men and women to further characterize the safety, tolerability, and PK/PD of mirogabalin administration with or without food and to guide the dose selection and regimen for phase 2 and 3 clinical development. The 3 studies included 2 randomized, double-blind, placebo-controlled, single- and multiple-ascending-dose studies, and 1 open-label, crossover study to evaluate the PK of mirogabalin administered under fasting and fed (high-fat meal) conditions. Forty-eight and 47 healthy volunteers completed the single- and multiple-dose studies, respectively. Thirty subjects were enrolled and completed the food effect study. Mirogabalin was well tolerated in the fed and fasted states. The most frequent treatment-emergent adverse events (TEAEs)-dizziness and somnolence-were expected based on mirogabalin's mechanism of action. Subjects receiving the highest mirogabalin doses (50 and 75 mg single dose) showed greater dizziness and sedation and higher rates of TEAEs than subjects receiving 3-30 mg. After oral administration, mirogabalin was rapidly absorbed (time to maximum concentration, ∼1 hour) and eliminated through urine unchanged (61%-72% urinary excretion). Exposure increased in a dose-proportional manner after single or multiple mirogabalin doses. No significant accumulation occurred with multiple doses over 14 days. After single doses of mirogabalin (15 mg), the bioavailability was considered equivalent in the fed and fasted states, indicating that mirogabalin can be taken without food restrictions. Based on these data, mirogabalin 15 mg twice daily was selected as the highest target dose for further clinical development.

A Randomized, Placebo-Controlled, Double-Blind Study of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single and Repeated Doses of Mirogabalin in Healthy Asian Volunteers

Mirogabalin is a novel, preferentially selective α₂ δ-1 ligand under investigation to treat neuropathic pain. The purpose of this study was to evaluate the safety, tolerability, and pharmacokinetics of various doses of mirogabalin in healthy subjects of different ethnicities. This randomized, placebo-controlled, double-blind, sequential, ascending-dose study evaluated single (10-40 mg) and repeated (10, 15 mg twice a day) doses of mirogabalin in Japanese subjects, and a single dose of mirogabalin in Korean, Chinese, and white subjects. Mirogabalin was rapidly absorbed, with a median time to maximum plasma concentration of 1 hour, and rapidly eliminated, with a mean elimination half-life of 2 to 3 hours. Single-dose mirogabalin pharmacokinetic parameters were comparable between Asian and white subjects. Exposure increased proportionally as mirogabalin dose increased in Japanese subjects. Mean mirogabalin steady-state clearance and volume of distribution values were comparable across dose levels. No accumulation of mirogabalin was observed on repeated dosing in Japanese subjects. Mirogabalin had an acceptable safety and tolerability profile in Asian and white subjects at doses up to 15 mg twice a day for 7 days. The most common treatment-emergent adverse events (somnolence, headache, and dizziness) were consistent with the known mechanism of action and safety profile of mirogabalin.

Pharmacokinetics, safety, and tolerability of edoxaban in end-stage renal disease subjects undergoing haemodialysis

Edoxaban is an oral, direct, once-daily, factor Xa inhibitor developed for stroke prevention in patients with atrial fibrillation and for the treatment and secondary prevention of recurrent thromboembolism in patients with acute symptomatic venous thromboembolism. Among elderly patients who require anticoagulation therapies, some may have end-stage renal disease (ESRD). This open-label, phase 1, randomised, two-way crossover study was conducted to evaluate the pharmacokinetics of edoxaban in 10 subjects on haemodialysis. Eligible subjects with ESRD on chronic haemodialysis received a single, oraldose of edoxaban 15 mg 2 hours (h) prior to (on-dialysis) or in between (off-dialysis) haemodialysis sessions. Haemodialysis resulted in a minor decrease in mean total exposure (AUC0-∞; 676.2 ng⋅h/ml) as compared with that observed in subjects off-dialysis (691.7 ng⋅h/ml). Mean maximum observed plasma concentration (Cmax) values were comparable between on-dialysis and off-dialysis treatments (53.3 vs 56.3 ng/ml, respectively). Mean apparent total body clearance (CL/F) values were 24.1 and 22.5 l/h during the on-dialysis and off-dialysis treatment periods, respectively. Dialyser clearance was 5.7 l/h and haemodialysis clearance was 6.1 l/h. Haemodialysis clearance was only 6.1 l/h, suggesting that it only accounts for one-fourth of the total clearance in these subjects. A single, oral dose of 15 mg of edoxaban was well tolerated by subjects with ESRD. In conclusion, based on these single-dose PK data, a supplementary dose of edoxaban may not be required following a haemodialysis session. Importantly, haemodialysis is not an effective mechanism for removal of edoxaban from the blood.

A first-in-human study of DS-1040, an inhibitor of the activated form of thrombin-activatable fibrinolysis inhibitor, in healthy subjects

Essentials DS-1040 inhibits the activated form of thrombin-activatable fibrinolysis inhibitor (TAFIa). Infusion of DS-1040 was safe and well tolerated in healthy young and elderly subjects. DS-1040 substantially decreased TAFIa activity but had no impact on bleeding time. DS-1040 may provide an option of safer thrombolytic therapy.

SUMMARY

Background Current treatments for acute ischemic stroke and venous thromboembolism, such as recombinant tissue-type plasminogen activator and thrombectomy, are limited by a narrow time window and the risk of bleeding. DS-1040 is a novel low molecular weight compound that inhibits the activated form of thrombin-activatable fibrinolysis inhibitor (TAFIa), and was developed as a fibrinolysis enhancer for the treatment of thromboembolic diseases. Objectives This first-in-human, randomized, placebo-controlled, three-part, phase 1 study was conducted to evaluate the safety, pharmacokinetics and pharmacodynamics of DS-1040 in healthy subjects. Subjects/Methods Young (18-45 years) or elderly (65-75 years) subjects (N = 103) were randomized to receive single ascending doses of DS-1040 ranging from 0.1 mg to 40 mg, or placebo, administered either as a 0.5-h intravenous infusion or as a 24-h continuous infusion. Results All doses of DS-1040 were tolerated, and no serious adverse events (AEs) or discontinuations resulting from AEs occurred during the study. Bleeding time remained within the normal range for all doses tested in all subjects. Plasma exposure of DS-1040 increased proportionally with increase in dose. Elderly subjects had higher exposures to DS-1040 and prolonged elimination times, probably because of decreased renal clearance. DS-1040 caused a substantial dose-dependent and time-dependent decrease in TAFIa activity and in 50% clot lysis time. The levels of D-dimer, indicative of endogenous fibrinolysis, increased in some individuals following DS-1040 treatment. No effects of DS-1040 on coagulation parameters or platelet aggregation were observed. Conclusions The novel fibrinolysis-enhancing agent DS-1040 has favorable pharmacokinetic/pharmacodynamic properties and a favorable safety profile, warranting further clinical development.

Single-dose ciraparantag safely and completely reverses anticoagulant effects of edoxaban

Of the new direct oral anticoagulants, direct factor Xa inhibitors are limited by the absence of a proven reversal agent. We assessed the safety, tolerability and impact on anticoagulation reversal of ciraparantag (PER977) alone and following a 60 mg dose of the FXa inhibitor edoxaban. Escalating, single IV doses of ciraparantag were administered alone and following a 60 mg oral dose of edoxaban in a double-blind, placebo-controlled fashion to healthy subjects. Serial assessments of the pharmacokinetics and pharmacodynamic effects of ciraparantag were performed. Eighty male subjects completed the study. Following edoxaban (60 mg), a single IV dose of ciraparantag (100 to 300 mg) demonstrated full reversal of anticoagulation within 10 minutes and sustained for 24 hours. Fibrin diameter within clots was restored to normal 30 minutes after a single dose of 100 to 300 mg ciraparantag as determined by scanning electron microscopy and change in fibrin diameter quantified by automated image analysis. Potentially related adverse events were periorbital and facial flushing and cool sensation following IV injection of ciraparantag. Renal excretion of ciraparantag metabolite was the main elimination route. There was no evidence of procoagulant activity following ciraparantag as assessed by D-dimer, prothrombin fragments 1.2, and tissue factor pathway inhibitor levels. In conclusion, ciraparantag in healthy subjects is safe and well tolerated with minor, non-dose limiting adverse events. Baseline haemostasis was restored from the anticoagulated state with doses of 100 to 300 mg ciraparantag within 10-30 minutes of administration and sustained for at least 24 hours.

The impact of a three-factor prothrombin complex concentrate on the anticoagulatory effects of the factor Xa inhibitor edoxaban

BACKGROUND

Edoxaban, a direct factor Xa inhibitor, is a once-daily, non-vitamin K antagonist oral anticoagulant. There is no established method to reverse the activity of non-vitamin K oral anticoagulants in cases of hemorrhage or urgent surgery. This study evaluated the ability of a 3-factor prothrombin complex concentrate (3F-PCC) to reverse the anticoagulatory effects of edoxaban.

METHODS

In this phase 1 study, 24 healthy subjects were randomly assigned to receive a single dose of 60 or 180mg edoxaban, followed by placebo, 25IU/kg 3F-PCC, or 50IU/kg 3F-PCC. Edoxaban pharmacokinetics and pharmacodynamics, including the primary endpoint of prothrombin time (PT) and endogenous thrombin potential (ETP), were assessed. D-dimer and prothrombin fragment 1 and 2 (F1+2) were also measured.

RESULTS

Overall, there were no apparent consistent effects of 3F-PCC on edoxaban pharmacokinetics. Administration of 3F-PCC 25 or 50IU/kg with edoxaban 60 or 180mg did not substantially accelerate the return of PT to baseline levels. However, infusion of 3F-PCC 25 and 50IU/kg did substantially accelerate return to baseline of ETP compared with placebo. D-dimer and F1+2 data did not indicate any lasting procoagulant effects of 3F-PCC infusion, although a transient increase in F1+2 was noted during and after 3F-PCC infusion. Edoxaban and 3F-PCC co-administration was well tolerated in normal healthy subjects.

CONCLUSIONS

There was no apparent reversal of PT prolongation with 3F-PCC following edoxaban infusion, but ETP was completely reversed. Co-administration of 3F-PCC was well tolerated, but a dose-dependent increase in F1+2 may reflect a procoagulant risk.

Edoxaban effects on bleeding following punch biopsy and reversal by a 4-factor prothrombin complex concentrate

BACKGROUND

The oral factor Xa inhibitor edoxaban has demonstrated safety and efficacy in stroke prevention in patients with atrial fibrillation and in the treatment and secondary prevention of venous thromboembolism. This study investigated the reversal of edoxaban's effects on bleeding measures and biomarkers by using a 4-factor prothrombin complex concentrate (4F-PCC).

METHODS AND RESULTS

This was a phase 1 study conducted at a single site. This was a double-blind, randomized, placebo-controlled, 2-way crossover study to determine the reversal effect of descending doses of 4F-PCC on bleeding duration and bleeding volume following edoxaban treatment. A total of 110 subjects (17 in part 1, 93 in part 2) were treated. Intravenous administration of 4F-PCC 50, 25, or 10 IU/kg following administration of edoxaban (60 mg) dose-dependently reversed edoxaban's effects on bleeding duration and endogenous thrombin potential, with complete reversal at 50 IU/kg. Effects on prothrombin time were partially reversed at 50 IU/kg. A similar trend was seen for bleeding volume.

CONCLUSIONS

The 4F-PCC dose-dependently reversed the effects of edoxaban (60 mg), with complete reversal of bleeding duration and endogenous thrombin potential and partial reversal of prothrombin time following 50 IU/kg. Edoxaban alone and in combination with 4F-PCC was safe and well tolerated in these healthy subjects. A dose of 50 IU/kg 4F-PCC may be suitable for reversing edoxaban anticoagulation.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT02047565.

Pharmacokinetics and pharmacodynamics of MK-5046, a bombesin receptor subtype-3 (BRS-3) agonist, in healthy patients

MK-5046 is an orally active, potent, selective agonist of the orphan G protein-coupled receptor bombesin receptor subtype-3 (BRS-3) that is under evaluation for treatment of obesity. We report the safety, tolerability, pharmacokinetics, and pharmacodynamics of oral doses of MK-5046 (10-160 mg) in a double-blind, randomized, placebo-controlled study in healthy and obese male volunteers. MK-5046 exposure increased dose proportionally, and MK-5046 was eliminated with an apparent terminal half-life of 1.5 to 3.5 hours. Single doses transiently increased blood pressure. Patients reported adverse events (erections and feeling hot, cold, and/or jittery) that coincided with time of occurrence (T(max)) and increased with increasing dose. No changes were observed in body temperature, heart rate, plasma glucose levels, or feelings of hunger/satiety. The blood pressure and thermal experiences attenuated with a second dose 6 hours after the first. Additionally, the erections suggest a possible, unanticipated, role for BRS-3 in reproductive physiology. Oral administration of MK-5046 achieves plasma concentrations that are projected to activate BRS-3 and therefore should be suitable for exploring its biological role in humans.

The effects of laropiprant, a selective prostaglandin D₂ receptor 1 antagonist, on the antiplatelet activity of clopidogrel or aspirin

Laropiprant (LRPT) is being developed in combination with Merck's extended-release niacin (ERN) formulation for the treatment of dyslipidemia. LRPT, an antagonist of the prostaglandin PGD₂ receptor DP1, reduces flushing symptoms associated with ERN. LRPT also has affinity for the thromboxane A₂ receptor TP (approximately 190-fold less potent at TP compared with DP1). Aspirin and clopidogrel are two frequently used anti-clotting agents with different mechanisms of action. Since LRPT may potentially be co-administered with either one of these agents, these studies were conducted to assess the effects of steady-state LRPT on the antiplatelet activity of steady-state clopidogrel or aspirin. Bleeding time at 24 h post-dose (trough) was pre-specified as the primary pharmacodynamic endpoint in both studies. Two separate, double-blind, randomized, placebo-controlled, crossover studies evaluated the effects of multiple-dose LRPT on the pharmacodynamics of multiple-dose clopidogrel or aspirin. Healthy subjects were randomized to once-daily oral doses of LRPT 40 mg or placebo to LRTP co-administered with clopidogrel 75 mg or aspirin 81 mg for 7 days with at least a 21-day washout between treatments. In both studies, bleeding time and platelet aggregation were assessed 4 and 24 hours post-dose on Day 7. Comparability was declared if the 90% confidence interval for the estimated geometric mean ratio ([LRPT+clopidogrel]/clopidogrel alone or [LRPT+aspirin]/aspirin alone) for bleeding time at 24 hours post-dose on Day 7 was contained within (0.66, 1.50). Concomitant daily administration of LRPT 40 mg with clopidogrel 75 mg or aspirin 81 mg resulted in an approximate 4-5% increase in bleeding time at 24 hours after the last dose vs. bleeding time after treatment with clopidogrel or aspirin alone, demonstrating that the treatments had comparable effects on bleeding time. Percent inhibition of platelet aggregation was not significantly different between LRPT co-administered with clopidogrel or aspirin vs. clopidogrel or aspirin alone at 24 hours post-dose at steady state. At 4 hours after the last dose, co-administration of LRPT 40 mg resulted in 3% and 41% increase in bleeding time vs. bleeding time after treatment with aspirin or clopidogrel alone, respectively. Co-administration of LPRT with clopidogrel or aspirin was generally well tolerated in healthy subjects. Co-administration of multiple doses of LRPT 40 mg and clopidogrel 75 mg or aspirin 81 mg had no clinically important effects on bleeding time or platelet aggregation.

Laropiprant in combination with extended-release niacin does not alter urine 11-dehydrothromboxane B2, a marker of in vivo platelet function, in healthy, hypercholesterolemic, and diabetic subjects

Laropiprant, an antagonist of the PGD(2) receptor, DP1, is effective in reducing the flushing symptoms associated with extended-release (ER) niacin and thereby improves the tolerability of niacin therapy for dyslipidemia. Because PGD(2) has been reported to inhibit platelet aggregation in vitro, it has been speculated that antagonism of DP1 may enhance platelet reactivity. Three clinical studies evaluated the potential effect of laropiprant, with or without coadministration of ER niacin, on in vivo platelet function in healthy subjects and hypercholesterolemic or diabetic subjects by measuring urinary levels of 11-dehydrothromboxane B(2) (11-dTxB(2)), a marker of in vivo platelet activation. Following 7 days of multiple-dose administration, coadministration of laropiprant with ER niacin did not increase urinary 11-dTxB(2) levels compared to ER niacin alone in healthy, hypercholesterolemic, or diabetic subjects. In hypercholesterolemic and diabetic subjects, laropiprant did not increase urinary 11-dTxB(2) levels compared to placebo. These results demonstrate that laropiprant does not enhance in vivo platelet reactivity, either alone or in combination with niacin.

Effects of aspirin when added to the prostaglandin D2 receptor antagonist laropiprant on niacin-induced flushing symptoms

Niacin is an effective lipid-modifying therapy whose use has been limited by suboptimal tolerability. The adverse effect of flushing is due to prostaglandin D2 (PGD2)-mediated cutaneous vasodilation. Adjunctive treatment with the PGD2 receptor antagonist laropiprant significantly reduces the incidence and severity of niacin-induced flushing. The objective of this study was to assess the effect of aspirin pretreatment on flushing symptoms with extended-release (ER) niacin/laropiprant in healthy volunteers. A randomized, double-blind, placebo-controlled crossover study compared patient-rated flushing following pretreatment with aspirin 325 mg versus placebo administered 30 minutes before ER niacin 2 g/laropiprant 40 mg. Flushing responses were assessed using participant-reported overall symptom severity score (OSSS), including individual characteristics of redness, warmth, tingling, or itching. The overall incidence and severity of flushing were comparable for participants receiving aspirin or placebo before ER niacin 2 g/laropiprant 40 mg. The difference in 3-day average OSSS between treatments was 0.2 (P=.180). Profiles of flushing severity, frequency, and bothersomeness were comparable for the aspirin/ER niacin/laropiprant and ER niacin/laropiprant regimens. All treatments were safe and well tolerated. Coadministration of aspirin 325 mg daily with ER niacin 2 g/laropiprant 40 mg does not further reduce residual flushing symptoms associated with ER niacin 2 g/laropiprant 40 mg alone.

Endothelial function in systemic lupus erythematosus: relationship to disease activity, cardiovascular risk factors, corticosteroid therapy, and coronary calcification

Objectives

Endothelial dysfunction is frequently present in patients with systemic lupus erythematosus and may increase their risk of premature coronary artery disease. In this pilot study we have characterized the relationship between endothelial function, measures of disease activity, and cardiovascular risk factors in patients with lupus.

Methods

Clinical characteristics and cardiovascular risk factors were evaluated in 20 patients with lupus. Flow-mediated dilation of the brachial artery was measured using high resolution ultrasound and the presence or absence of coronary calcification determined by electronbeam computed tomography. The relationship between these variables and flow-mediated dilation was determined using Spearman correlation coefficients (RHO) and Mann Whitney-Wilcoxon tests.

Results

Twenty patients (17 female) median age (interquartile range) 42.5 (32.0–47.5) years were studied. The median flow-mediated vasodilation was 3.6% (1.7%–7.7%). In patients with coronary calcification (n = 6), flow-mediated dilation was 2.1% (−0.42%–3.6%) compared with 4.0% (3.5%–8.3%) in those without (p = 0.12). There was no significant relationship between flow-mediated dilation and markers of disease activity, duration of disease, and cardiovascular risk factors. Lower flow-mediated dilation was associated with duration of corticosteroid therapy (RHO = −0.44, p = 0.05).

Conclusions

In these preliminary results, endothelial dysfunction is associated with longterm exposure to corticosteroids.

The effect of simvastatin, ezetimibe and their combination on the lipid profile, arterial stiffness and inflammatory markers

OBJECTIVE

Arterial stiffness and highly sensitive C-reactive protein (hsCRP) serum level predict the risk for cardiovascular events. The most commonly used drugs for lowering cholesterol levels, the statins, also have anti-inflammatory effects and can decrease arterial stiffness. Ezetimibe is the first drug of a new class of cholesterol absorption inhibitors in common use and, to date, its effect on arterial stiffness has not yet been studied. The aim of this study was to compare the effect of simvastatin and ezetimibe, both singly and in combination, on arterial stiffness and hsCRP serum concentration in hypercholesterolemic patients.

METHODS

Forty hypercholesterolemic patients were studied. Group1 comprised previously untreated patients, who received simvastatin at doses of 40 mg/day during the study; group 2 comprised patients previously treated with simvastatin at 40 mg/day, who received simvastatin at 80 mg/day during the study; group 3 consisted of patients previously untreated, who received ezetimibe at doses of 10 mg/day during the study; group 4 comprised patients previously treated with simvastatin at 40 mg/day, who received simvastatin at 40 mg/day and ezetimibe at 10 mg/day during the study. Arterial stiffness expressed as the Augmentation Index (AIx) (assessed by pulse wave analysis), the lipid profile and the hsCRP level were measured at baseline and after 3 months of treatment.

RESULTS

The reduction in low-density lipoprotein (LDL) after treatment was significantly greater in groups 1 and 4 (39.9 and 35.7%) than in groups 2 and 3 (17.7 and 16.9%; p = 0.005). The AIx decreased significantly only in group 1 patients, from 30.2 +/- 8.3% before treatment to 21.6 +/- 6.5% after treatment (p < 0.001). Changes in hsCRP paralleled the changes in AIx, with a significant decrease in patients in group 1 only, from 2.8 +/- 2.5 mg/L before treatment to 1.6 +/- 1.5 mg/L after treatment (p = 0.016).

CONCLUSION

Ezetimibe as a monotherapy had no effect on arterial stiffness or hsCRP, while the administration of simvastatin at 40 mg per day improved arterial stiffness and CRP. However, increasing the dose of simvastatin or administering ezetimibe in combination with simvastatin had no beneficial effects on arterial stiffness.

Serious Consequences to the Use of Cephalosporins as the First Line of Antimicrobial Therapy Administered in Hemodialysis Units

BACKGROUND

The dramatic spread of vancomycin-resistant enterococci (VRE) among hemodialysis (HD) patients led to the replacement of vancomycin with cephalosporins as part of the primary empiric therapy for bacterial infections in HD units. The aim of the study was to examine the effects of this new regimen on the colonization rate of resistant bacteria among HD patients.

METHODS

Rectal swabs were taken from 105 HD patients and 91 control hospitalized patients. Groups were matched for age, sex, nursing home residency and background diseases. Enterococci were tested for vancomycin resistance, Staphylococcus aureus isolates were tested for methicillin resistance (MRSA), and Enterobacteriaceae were tested for extended-spectrum beta-lactamase (ESBL) activity.

RESULTS

In the HD group 1 VRE, 1 MRSA and 9 ESBL-producing organisms were isolated compared to 1 MRSA and 1 ESBL organism in the control group (p = 0.018 for ESBL). In the year prior to the study, the use of cephalosporins had been enhanced in the HD group compared to the control group (p < 0.001), and in the HD ESBL-positive patients compared to the HD ESBL-negative ones (p = 0.007). The overall use of antibiotics in the control group was the same as in the HD group. In a subanalysis of the HD group alone, the ESBL carriers were older, sicker, used more antibiotics, were hospitalized frequently and had a higher mortality rate, compared to noncarriers.

CONCLUSIONS

The use of cephalosporins as first-line therapy in HD patients in central Israel reduced the prevalence of VRE colonization but may have contributed to the emergence of ESBL-producing organisms through induction of selection pressure. This may lead to serious complications in the management of these patients.

The effect of losartan and losartan/hydrochlorothiazide fixed-combination on magnesium, zinc, and nitric oxide metabolism in hypertensive patients: a prospective open-label study

BACKGROUND

Thiazide diuretics and angiotensin-converting enzyme inhibitors can cause excessive urinary zinc (Zn) loss and Zn depletion. Thiazides may also induce magnesium (Mg) deficiency, which may exacerbate hypertension. Data on the effects of angiotensin receptor blockers on Zn and Mg homeostasis are scarce.

METHODS

Seventeen hypertensive patients were studied (ten men and seven women, age 50 +/- 3 years, blood pressure 158 +/- 5 / 95 +/- 3 mm Hg). Patients were treated with losartan 50 mg/day for 4 weeks followed by a fixed combination of 50 mg losartan and 12.5 mg hydrochlorothiazide for 4 weeks more. Blood and 24-h urine were collected at baseline and after each study period. Zinc and Mg levels were measured in serum, urine, and peripheral blood mononuclear cells. Nitric oxide metabolites were measured in urine.

RESULTS

Treatment with losartan resulted in a significant increase in the urinary Zn/creatinine ratio (from 0.020 +/- 0.004 microg/mg to 0.034 +/- 0.005 microg/mg, P = .02), which was further increased by the losartan/hydrochlorothiazide combination (from 0.034 +/- 0.005 microg/mg to 0.053 +/- 0.008 microg/mg, P = .03). Serum Zn levels were significantly decreased after losartan/hydrochlorothiazide (from 80.0 +/- 4.0 microg/dL at baseline to 74.0 +/- 3.0 microg/dL, P = .007). Peripheral blood mononuclear Zn concentrations were decreased also, but this was not statistically significant. Serum, urinary, and peripheral blood mononuclear Mg levels were not significantly affected by treatment. Nitric oxide urinary metabolites were unchanged throughout the study.

CONCLUSIONS

Treatment with losartan causes an increase in urinary Zn excretion and induces Zn deficiency in patients with hypertension. The addition of hydrochlorothiazide has an additive effect. Magnesium and nitric oxide metabolism are not affected by either treatment.

Beta2-adrenoceptor Thr164Ile polymorphism is associated with markedly decreased vasodilator and increased vasoconstrictor sensitivity in vivo

BACKGROUND

The uncommon Thr164Ile polymorphism of the beta2-adrenoceptor is associated with profoundly altered responses to agonist in vitro; however its effects on vascular responses in vivo are not known. Altered adrenergic vascular sensitivity may contribute to the decreased survival observed in patients with congestive heart failure carrying the Ile164 allele.

METHODS AND RESULTS

We used the linear variable differential transformer dorsal hand vein technique to compare vasodilation in response to the beta-adrenergic receptor agonist, isoproterenol, and vasoconstriction in response to the alpha-adrenergic receptor agonist, phenylephrine, in healthy homozygous (Thr164/Thr164) (n = 21) and heterozygous Thr164/Ile164 (n = 5) women. The dose of isoproterenol required to achieve 50% venodilation (geometric mean; 95% CI) was significantly higher in women with the Ile164 allele (82.5 ng/min; 17.3-394 ng/min) than those without (15.8 ng/min; 11-25 ng/min; P = 0.004). The maximum response to isoproterenol was not different (102 +/- 1% and 102 +/- 3%, respectively, P = 0.9). The dose of phenylephrine needed to induce 50% venoconstriction was significantly lower in women with the Ile164 allele (151 ng/min; 42-543 ng/min) than those without (540 ng/min; 350-835 ng/min; P = 0.02).

CONCLUSIONS

The Thr164Ile polymorphism of the beta2-adrenergic receptor is associated with a five-fold reduction in sensitivity to beta2 receptor agonist-mediated vasodilation; vasoconstrictor sensitivity is increased. The overall effect of the Thr164Ile polymorphism is to shift the balance of adrenergic vascular tone toward vasoconstriction. This suggests a mechanistic explanation for the clinical observation of decreased survival in patients with congestive heart failure heterozygous for the Thr164Ile polymorphism.

N-Acetylcysteine ameliorates lithium-induced renal failure in rats

BACKGROUND

Prolonged lithium treatment may induce progressive deterioration of renal function in humans and experimental animals. N-Acetylcysteine (NAC) has been shown to be effective in the prevention of hypoperfusion and toxin-induced renal failure, but its effect on lithium nephrotoxicity has not been evaluated yet. The purpose of this study was to examine a possible renoprotective effect of NAC against lithium-induced renal failure in a rat model.

METHODS

Moderate renal failure was induced in 40 Sprague-Dawley rats using a 5 week protocol including 3 weeks of lithium chloride administration in the drinking water. The animals were divided randomly into two equal groups receiving either 10 mg/kg NAC or saline by two daily intraperitoneal injections. In week 6, the glomerular filtration rate (GFR) was assessed by 99mTechnetium diethylene triaminepentaacetic acid, and serum creatinine, blood urea nitrogen (BUN) and 24 h urinary protein and osmolarity were measured. Kidneys were excised for pathological evaluation.

RESULTS

At the end of the lithium protocol, the GFR was significantly higher in the NAC-treated group compared with the control group, 0.92+/-0.35 vs 0.56+/-0.25 ml/min/100 g, respectively, P = 0.002. Serum creatinine and BUN were also significantly lower in the NAC-treated group 1.009+/-0.107 vs 1.143+/-0.118 mg/dl, P = 0.001, and 83.9+/-6.8 vs 88.95+/-7.1 mg/dl, P = 0.28, respectively. The percentages of tubular necrosis and tubular lumen obstruction, evaluated by light microscopy, were significantly lower in the NAC-treated group, P = 0.002 and P = 0.007, respectively.

CONCLUSIONS

NAC treatment has a renoprotective effect against lithium-induced renal failure in a rat model.

The effect of sildenafil on gastric emptying in patients with end-stage renal failure and symptoms of gastroparesis

BACKGROUND

Delayed gastric emptying is a common disorder among patients with end-stage renal failure (ESRF). Pyloric relaxation, a major determinant of gastric emptying, is a nitric oxide (NO)-mediated process. NO-induced smooth muscle relaxation is mediated through its second messenger cyclic guanosine monophosphate, which is broken by tissue phosphodiesterases (PDEs). Thus the inhibition of cyclic guanosine monophosphate breakdown by PDE inhibitors can potentiate NO-mediated responses and facilitate pyloric relaxation. In an animal model of diabetes mellitus, treatment with sildenafil (a PDE-5 inhibitor) restored NO-mediated pyloric relaxation and improved gastric emptying. The aim of our study was to examine the hypothesis that sildenafil may improve gastric emptying in patients with ESRF and symptoms of gastric paresis.

METHODS

We studied 12 patients with ESRF (6 men; age range, 54-80 years; 5 with diabetic nephropathy; 4 +/- 1 years receiving long-term renal replacement therapy) after either placebo or a 25-mg tablet of sildenafil (Viagra; Pfizer Inc). Gastric emptying of a solid meal (one medium-sized fried egg mixed with 37 MBq [1 mCi] technetium Tc 99m phytate plus 1 slice of bread and 150 mL of water at the end of the meal) was assessed 1 hour after dosing by use of a single-headed camera. Images were acquired every 30 seconds for 90 minutes immediately after patients ate.

RESULTS

The gastric emptying rate was decreased at baseline (after placebo), to 33% +/- 6% (normal, > or =50%). Treatment with sildenafil had no effect on gastric emptying rates after 90 minutes (from 33% +/- 6% after placebo to 30% +/- 6% after sildenafil, P =.9).

CONCLUSIONS

Sildenafil did not improve gastric emptying in patients with ESRF and gastric paresis. Sildenafil may have opposing effects on gastric peristalsis (causing gastric relaxation) compared with its effects on pyloric relaxation. Studies combining sildenafil with prokinetic drugs are of interest.

The effect of N-acetylcysteine on renal function, nitric oxide, and oxidative stress after angiography

BACKGROUND

Renal failure induced by radiographic contrast agents is a known complication of coronary angiography, especially among patients with chronic renal failure. Recently, treatment with N-acetylcysteine (NAC) has been shown to have a protective effect but the mechanisms are unknown. We examined the hypothesis that NAC protected against contrast-induced renal impairment through effects on nitric oxide metabolism and oxidative stress.

METHODS

Patients with a serum creatinine concentration above 10(6) micromol/L undergoing coronary angiography were randomly assigned to receive either NAC 1 g (N= 24) or placebo (N= 29) twice daily 24 hours before and after angiography with 0.45% saline hydration in a double-blind study. Creatinine clearance was calculated and urinary nitric oxide and F2-isoprostane excretion were measured at baseline, 24 and 96 hours after angiography.

RESULTS

Treatment with NAC significantly improved the effect of contrast media on creatinine clearance, and maximal beneficial effect was observed 24 hours after angiography. Creatinine clearance (mL/min) was 59.5 +/- 4.4, 64.7 +/- 5.8, and 58.7 + 3.9 at baseline, 24, and 96 hours after angiography in the NAC group, respectively, and 65.2 +/- 3.2, 51.5 +/- 3.7, and 53.6 +/- 3.9 in the placebo group, respectively (P < 0.0001). NAC treatment prevented the reduction in urinary nitric oxide after angiography. The urinary nitric oxide/creatinine ratio (micromol/mg) was 0.0058 +/- 0.0004, 0.0057 +/- 0.0004, and 0.0052 +/- 0.0004 at baseline, 24, and 96 hours after angiography in NAC group, respectively, and 0.0057 +/- 0.0007, 0.0031 +/- 0.0005, and 0.0039 +/- 0.0005 in the placebo group, respectively (P= 0.013). NAC had no significant effect on urinary F2-isoprostanes.

CONCLUSION

NAC treatment has renoprotective effect in patients with mild chronic renal failure undergoing coronary angiography that may be mediated in part by an increase in nitric oxide production.

$alpha;1A-adrenergic receptor polymorphism and vascular response*1, *2

OBJECTIVE

The alpha(1A)-adrenergic receptor is highly expressed in human vasculature including resistance arteries and veins, and its stimulation is primarily responsible for adrenergically mediated smooth muscle contraction. Variability in sensitivity to phenylephrine, an alpha(1A) adrenergic agonist, has a large genetic component. We examined the hypothesis that a common polymorphism of alpha(1A)-adrenergic receptor (Arg347Cys) affects in vivo response.

METHODS

We measured vascular sensitivity to phenylephrine using the dorsal hand vein linear variable differential transformer technique and determined alpha(1A)-adrenergic receptor genotype in 74 healthy, nonsmoking adults (28 Arg/Arg, 30 Arg/Cys, and 16 Cys/Cys).

RESULTS

Sensitivity to phenylephrine, expressed as the dose of phenylephrine resulting in 50% venoconstriction (Phe(50)), was not significantly different in subjects with the 3 alpha(1A) adrenergic receptor genotypes: Phe(50) geometric mean (95% confidence interval) was 513 ng/min (287-918 ng/min) for Arg/Arg, 431 ng/min (274-680 ng/min) for Arg/Cys, and 471 ng/min (197-1124 ng/min) for Cys/Cys (P =.90).

CONCLUSION

We conclude that the Arg347Cys receptor polymorphism does not alter agonist-mediated venoconstriction in vivo.

No association of the Asp298 variant of the endothelial nitric oxide synthase gene with preeclampsia

BACKGROUND

Preeclampsia, the most common serious complication of pregnancy, is characterized by vasoconstriction, dysfunction of the vascular endothelium, and hypertension. Unidentified genetic factors and impaired nitric oxide (NO)-mediated vasodilation are thought to contribute to the development of the syndrome. Polymorphisms of the endothelial nitric oxide synthase (eNOS) gene affect NO production and have been associated with hypertension and preeclampsia in a Japanese population.

METHODS

We compared the frequency of the Glu298Asp eNOS polymorphism in 397 Hispanic and white normotensive pregnant control subjects with the gene frequencies in 64 women with preeclampsia (systolic blood pressure >140 mm Hg or diastolic blood pressure >90 mm Hg, on at least two occasions 6 hours apart, and proteinuria >0.3 g/L or a dipstick proteinuria reading of 2+).

RESULTS

Preeclampsia was not associated with the presence of Asp at position 298 of eNOS.

CONCLUSIONS

In contrast to the findings in Japanese women, preeclampsia was not associated with the Asp variant of eNOS in an American population.

Sildenafil does not improve nitric oxide-mediated endothelium-dependent vascular responses in smokers

AIMS

To examine the hypothesis that sildenafil, a phosphodiesterase type 5 inhibitor that inhibits cGMP breakdown, could enhance nitric oxide-mediated vasodilation and reverse endothelial dysfunction in chronic smokers.

METHODS

Flow-mediated dilation of the brachial artery and forearm postischemic reactive hyperemia (both nitric oxide-mediated responses) were measured before and after sildenafil 50 mg and placebo in a double-blind, randomized, crossover study in 9 men who were chronic smokers (21 +/- 3 pack years).

RESULTS

There was no significant change in flow-mediated dilation after either sildenafil (0.18%, 95%CI -1.7-2%) or placebo (0.24%, 95%CI -2.8-3.3%) (P = 0.88 and 0.8, respectively). Sildenafil had no significant effect on resting forearm blood flow or postischemic reactive hyperemia (P = 0.39 and 0.7, respectively). Resting heart rate and blood pressure were unaffected by sildenafil.

CONCLUSIONS

Acute sildenafil administration did not improve endothelial function in chronic smoking men.

G-protein beta(3) subunit 825 C/T polymorphism is associated with weight gain during pregnancy

A common polymorphism (C825T) of the gene encoding the G-protein beta(3) subunit has been associated with obesity. We examined the hypothesis that this polymorphism affected weight gain during pregnancy. Two hundred and ninety-four women with uncomplicated term deliveries of singleton pregnancies were genotyped. Women homozygous for the T allele (TT) gained significantly more weight than women carrying the C allele (CC and CT groups) (P = 0.006) and had a significantly higher pre-pregnancy body mass index (P = 0.02). The C825T polymorphism of the G-protein beta(3) subunit gene, known to be associated with obesity, is a determinant of weight gain during pregnancy.

A common beta1-adrenergic receptor polymorphism (Arg389Gly) affects blood pressure response to beta-blockade

BACKGROUND

A common polymorphism of the beta(1)-adrenergic receptor Arg389Gly markedly affects function in vitro, but little is known about its in vivo significance.

METHODS AND RESULTS

Resting and exercise hemodynamic responses were measured in subjects homozygous for Arg389 (n = 21) or Gly389 (n = 13) alleles before and 3 hours after administration of a beta-blocker, atenolol. Demographic characteristics and atenolol concentrations were similar in the two genotypic groups. Genotype had a marked effect on resting hemodynamic responses to atenolol, with Arg389-homozygous subjects having a larger decrease in resting systolic blood pressure (8.7 +/- 1.3 mm Hg versus 0.2 +/- 1.7 mm Hg, P < .001) and mean arterial blood pressure (7.2 +/- 1.0 mm Hg versus 2.0 +/- 1.7 mm Hg, P = .009). Attenuation of exercise-induced hemodynamic responses by atenolol was not affected by genotype.

CONCLUSIONS

There is reduced sensitivity of Gly389 homozygotes to a beta-adrenergic receptor antagonist, and this polymorphism may be an important determinant of variability in response to beta-blockade.

Nitric oxide production decreases after salt loading but is not related to blood pressure changes or nitric oxide-mediated vascular responses

BACKGROUND

Nitric oxide production is a homeostatic mechanism that may regulate blood pressure during salt loading. Salt-sensitive hypertension in animal models and in humans is characterized by increased blood pressure and decreased nitric oxide production after salt loading. It is not known if this impaired nitric oxide production is the result of hypertension or is a mechanism contributing to the blood pressure response to salt.

METHODS AND RESULTS

The effects of salt loading on blood pressure, nitric oxide-mediated vasodilation and nitric oxide production were measured in 25 normotensive subjects after 6 days on either a high (400 mmol/day) or low (10 mmol/day) sodium, low nitrate diet. Mean arterial pressure increased during the high-salt diet [4 +/- 1 mmHg (mean +/- SEM)] in 12 subjects and remained unchanged or decreased (-4 +/- 1 mmHg) in 13 subjects. Plasma nitrite and nitrate, a measure of nitric oxide production, decreased significantly from 39 +/- 3.3 micromol/l during the low-salt diet to 22.4 +/- 2.4 micromol/l during the high-salt diet (P = 0.0001). However, changes in mean arterial pressure from low- to high-salt diet did not correlate with changes in plasma nitrite and nitrate (r = 0.14, P = 0.51). Forearm blood flow increased significantly (P <0.0001) in response to mental stress, a nitric oxide-mediated response, but was not affected by sodium intake (from 7.8 +/- 0.9 to 11.2 +/- 1.4 ml/min per 100 ml during low salt versus 8.5 +/- 1.2 to 10.4 +/- 1.3 ml/min per 100 ml during high salt,P = 0.3).

CONCLUSIONS

Salt loading results in a decrease in nitric oxide production in both salt-sensitive and salt-resistant normotensive subjects, which is independent of changes in blood pressure and does not affect the nitric oxide-mediated vascular response to mental stress. In contrast to salt-resistant animal models, salt loading in healthy subjects does not increase nitric oxide production. Therefore, the increased blood pressure response to salt loading may occur through mechanisms other than nitric oxide, or salt-sensitive individuals are more sensitive to the reduced nitric oxide production that occurs after salt loading in both salt-sensitive and salt-resistant subjects.

beta2-Adrenergic receptor genotype and preterm delivery

OBJECTIVE

Our purpose was to determine whether the functional genetic polymorphisms of the beta(2)-adrenergic receptor (beta(2)AR) that result in changes in amino acid residues 16 and 27 are associated with preterm delivery.

STUDY DESIGN

A case-control study comparing the distribution of beta(2)AR genotype between 251 Hispanic women delivered at term and 28 Hispanic women delivered preterm. Preterm delivery was defined as spontaneous onset of labor resulting in delivery before 37 weeks of gestation, in a singleton pregnancy, with no apparent etiology for preterm labor and delivery. Genomic DNA was isolated from peripheral blood, and beta( 2)AR alleles were identified by established techniques.

RESULTS

Only one woman (4%) with preterm labor was homozygous for Arg16 versus 79 (31%) in the control group (P =.01, odds ratio 0.08). There was no association of preterm labor with genotype at position 27.

CONCLUSION

Our data demonstrate that homozygosity for Arg16, which in vitro is associated with decreased down-regulation of the beta(2)AR, protects from preterm delivery.

ACE inhibitors and survival of hemodialysis patients

BACKGROUND

Cardiovascular disease is a leading cause of death in patients with end-stage renal disease (ESRD). Hypertension is a major risk factor for cardiovascular complications in these patients. Angiotensin-converting enzyme (ACE) inhibitors are an effective treatment for hypertension in patients with ESRD and are known to improve prognosis in patients with chronic renal failure. We investigated their effect on mortality in patients undergoing long-term hemodialysis therapy.

METHODS

Clinical data for patients on hemodialysis therapy between 1994 and 2000 were reviewed. Patients were grouped according to whether they had been treated with ACE inhibitors.

RESULTS

Sixty patients had been treated with ACE inhibitors (treated group) and 66 patients had not (untreated group). Blood pressure reduction was not significantly different between the treated and untreated groups. Nevertheless, comparing the treated group with the untreated group, mortality was decreased significantly in the treated group, with a risk reduction of 52% (rate ratio [RR], 0.482; confidence interval [CI], 0.25 to 0.91; P < 0.0019). In treated patients 65 years or younger, the absolute risk reduction of mortality was 79% (RR, 0.211; CI, 0.08 to 0.58; P < 0.0006).

CONCLUSION

Although further research is needed, these preliminary findings suggest that ACE inhibitors, independently of their antihypertensive effect, may dramatically reduce mortality among chronic hemodialysis patients 65 years or younger.

Disproportionate decrease in alpha- compared with beta-adrenergic sensitivity in the dorsal hand vein in pregnancy favors vasodilation

BACKGROUND

Altered vascular responses to adrenergic agonists during pregnancy are thought to play an important role in the regulation of blood pressure and placental blood flow. Because alpha1-adrenergic and beta2-adrenergic sensitivity act in opposing directions to determine vascular tone, we simultaneously evaluated alpha-adrenergic-mediated vasoconstriction and beta-adrenergic-mediated vasodilation in dorsal hand veins during and after pregnancy.

METHODS AND RESULTS

Twenty healthy pregnant women were studied at 32 to 37 weeks of gestation and again 12 weeks after delivery. Vascular response to phenylephrine (PE) and isoproterenol (ISO) was measured in a dorsal hand vein using the linear variable differential transformer technique. The dose of PE resulting in 50% constriction (CD50) was determined. The response to ISO was measured after the PE preconstriction. Pregnant and postpartum values, expressed as geometric mean (95% CI), were compared by paired t test. alpha-Adrenergic sensitivity during pregnancy (CD50 2.7 micro g/min [95% CI, 1.5 to 5.0]) was markedly decreased, approximately 7-fold, compared with postpartum (0.4 micro g/min [95% CI, 0.3 to 0.7] [P<0.01]). beta-Adrenergic vasodilation was also attenuated during pregnancy. The ED50 of ISO (dose of ISO resulting in 50% of the maximal response, E(max)) was greater during pregnancy (20 ng/min [95% CI, 11 to 35]) than postpartum (8 ng/min [95% CI, 5 to 12]) (P<0.05). ISO E(max) was also significantly less during pregnancy (81% [95% CI, 65 to 97] compared with postpartum (105% [95% CI, 97 to 113]) (P<01.01).

CONCLUSIONS

Normal pregnancy is characterized by decreased venous sensitivity to both alpha1-adrenoceptor-mediated vasoconstriction and beta2-adrenoceptor-mediated vasodilation. The greater decrease in alpha1 compared with beta2 response may contribute to the vasodilated state characteristic of human pregnancy.

In-vivo effects of Glu298Asp endothelial nitric oxide synthase polymorphism

Endothelial nitric oxide synthase catalyses the formation of the vasodilator nitric oxide, a major regulator of vascular tone. The Asp298 polymorphism of the nitric oxide synthase gene is associated with altered function and expression of the enzyme in vitro and myocardial infarction and coronary artery spasm in vivo. We examined the effect of the Glu298Asp polymorphism on: (1) local vascular responses to phenylephrine, acetylcholine, glyceryl trinitrate and prostaglandin E1 in the dorsal hand vein; (2) changes in forearm blood flow during mental stress, a measure of nitric oxide-mediated effect on resistance vessels; (3) excretion of urinary nitrite/nitrate as a measure of total body nitric oxide production; and (4) F2-isoprostane metabolite, a measure of oxidative stress, in healthy Glu298 (n = 12) and Asp298 (n = 13) homozygotes. There were no significant differences in acetylcholine dose responses (P = 0.29) in Glu298 and Asp298 homozygotes. Responses to glyceryl trinitrate, prostaglandin E1 and the alpha-adrenergic agonist phenylephrine did not differ by genotype. Forearm blood flow was similar at rest and increased significantly (from 7.5 ml/min/100 ml to 12.2 ml/min/100 ml; P = 0.003), but similarly (P = 0.2), during mental stress in both genotypes. Asp298 homozygotes excreted significantly less nitrate/nitrite than Glu298 homozygotes (nitrate + nitrite/creatinine ratio 0.05 +/- 0.01 vs. 0.09 +/- 0.01, respectively; P < 0.005). Urinary F2-isoprostane metabolite excretion did not differ (Glu298, 2.04 +/- 0.25 ng/mg creatinine; Asp298, 1.85 +/- 0.37 ng/mg creatinine; P = 0.7). We conclude that in healthy volunteers the Glu298Asp polymorphism affects endogenous nitric oxide production without affecting nitric oxide-mediated vascular responses. This polymorphism may only have clinical significance in the presence of endothelial dysfunction.

The effect of common polymorphisms of the beta2-adrenergic receptor on agonist-mediated vascular desensitization

BACKGROUND

With continuous exposure to beta2-adrenergic agonists, vascular tissue becomes desensitized to agonist-mediated vasodilatation. We studied the effects of two common polymorphisms of the beta2-adrenergic receptor, one at codon 16 and one at codon 27, on agonist-mediated vasodilatation and desensitization in the vascular bed.

METHODS

We studied 26 healthy subjects who were selected to represent three genotypes: 7 were homozygous for the alleles encoding Arg16 and Gln27, 8 were homozygous for the alleles encoding Gly16 and Gln27, and 11 were homozygous for the alleles encoding Gly16 and Glu27. Vascular responses were assessed by measuring changes in the diameter of a dorsal hand vein. A dose-response curve of the effect of the beta2-adrenergic-receptor agonist isoproterenol was constructed (dose range, 4 to 480 ng per minute). Desensitization was then induced by a 2-hour continuous infusion of isoproterenol, and venodilatation was measured 30, 60, 90, and 120 minutes after the start of the infusion.

RESULTS

Subjects who were homozygous for Arg16 had almost complete desensitization; venodilatation in response to isoproterenol in this group decreased from a mean (+/-SE) of 44+/-11 percent to 8+/-4 percent (P=0.006). In contrast, subjects who were homozygous for Gly16 did not have significant desensitization, irrespective of the amino acid encoded by codon 27. Subjects who were homozygous for Glu27 had higher maximal venodilatation in response to isoproterenol than those who were homozygous for Gln27 (86+/-13 percent vs. 54+/-8 percent, P=0.03).

CONCLUSIONS

The Arg16 polymorphism of the beta2-adrenergic receptor is associated with enhanced agonist-mediated desensitization in the vasculature, and the Glu27 polymorphism is associated with increased agonist-mediated responsiveness. Therefore, polymorphisms of the beta2-adrenergic receptor are potentially important determinants of the vascular response to stress.

The effect of sildenafil on nitric oxide-mediated vasodilation in healthy men

BACKGROUND

Sildenafil, a treatment for erectile dysfunction, is a specific phosphodiesterase type 5 (PDE 5) inhibitor that enhances nitric oxide (NO)-mediated vasodilation in the corpus cavernosum by inhibiting cyclic guanosine monophosphate breakdown. Since PDE 5 is widely expressed in the vasculature, we examined the hypothesis that sildenafil could enhance NO-mediated vasodilation in other vascular beds and improve endothelial function.

METHODS

NO-mediated responses to acetylcholine (endothelium-dependent) and nitroglycerin (endothelium-independent) were measured in healthy men in the dorsal hand vein (n = 13), after the administration of either sildenafil 50 mg or placebo. Flow-mediated dilation of the brachial artery and forearm postischemic reactive hyperemia were measured before and after sildenafil 50 mg, isosorbide dinitrate 5 mg, and placebo in a double-blind, randomized, crossover study (n = 11).

RESULTS

In the hand vein, sildenafil administration increased sensitivity to local nitroglycerin. The 50% effective dose decreased approximately 4-fold from 13.5 ng/min (range, 6.9-26.6 ng/min) to 2.7 ng/min (range, 1.1-6.4 ng/min) (P =.025). Sildenafil decreased the maximum venoconstriction induced by phenylephrine from 81% +/- 3% to 74% +/- 3% (P =.025). Sildenafil did not significantly affect the maximal venodilatory response to acetylcholine (35% +/- 7% after placebo versus 32% +/- 8% after sildenafil) (P =.7). In the arterial vasculature, flow-mediated dilation before (2.4% +/- 1%) and after (2.8% +/- 1.4%) sildenafil (P =.8) and postischemic reactive hyperemia area under the curve before (1807 +/- 393 mL. min. s/100 mL) and after (1467 +/- 257 mL. min. s/100 mL) sildenafil were not different (P =.8). Resting heart rate, blood pressure, and resting brachial artery diameter were unchanged after sildenafil administration. Isosorbide dinitrate, an endothelium-independent vasodilator, caused a significant increase in resting brachial artery diameter from 0.53 +/- 0.01 cm to 0.56 +/- 0.02 cm (P =.005), without altering flow-mediated dilation.

CONCLUSIONS

In healthy men sildenafil increased sensitivity to nitroglycerin, an exogenous NO donor, approximately 4-fold but did not affect endothelium-dependent, NO-mediated responses in either the hand vein or forearm vasculature. Differential vascular responses to sildenafil may localize its enhancement of endogenous NO-mediated vasodilation to vascular beds such as the corpus cavernosum.

Arg389Gly beta 1-adrenoceptor polymorphism varies in frequency among different ethnic groups but does not alter response in vivo

There are marked interethnic differences in beta 1-adrenoceptor-mediated responsiveness, with sensitivity decreased in African-Americans and increased in Chinese compared with Caucasians. Therefore, the frequency of a common naturally occurring polymorphism of the human beta 1-adrenoceptor gene (Arg389Gly), which has functional importance in vitro, was determined in 194 African-Americans, 316 Caucasian-Americans, 221 Hispanic-Americans and 142 Chinese. African-Americans were found to have a significantly lower frequency of the Arg389 allele than the other three ethnic groups (all P < 0.01). In the populations studied, the order of the distribution of the Arg389 allele was: Chinese (74%) > Caucasians (72%) > Hispanics (67%) > African-Americans (58%). To determine the functional significance of the Arg389Gly beta 1-adrenoceptor polymorphism, in-vivo heart rate responses to exercise were compared in healthy subjects homozygous for the Arg (n = 9) and Gly (n = 8) alleles. Heart rate response to exercise was not affected by genotype (P = 0.4). Although ethnic differences in the frequency of the beta 1-adrenoceptor Arg389Gly polymorphism exist, the polymorphism does not appear to have functional significance in healthy subjects and therefore may not contribute to ethnic differences in response to drugs acting through the beta 1-adrenoceptor.

Human beta2-adrenergic receptor polymorphisms: no association with essential hypertension in black or white Americans

BACKGROUND AND OBJECTIVES

The most common polymorphisms of the human beta2-adrenergic receptor--Arg16-->Gly and Gln27-->Glu--are associated with alterations in beta2-adrenergic receptor responses, both in vitro and in vivo. beta2-Adrenergic receptor-mediated vascular responses are affected by ethnicity, blood pressure, and genotype. We tested the hypothesis that these two common beta2-adrenergic receptor genetic variants are associated with essential hypertension in black or white Americans.

SUBJECTS AND METHODS

In a population-based case-control association study, the relationship between beta2-adrenergic receptor genotypes and hypertension was examined in 307 normotensive subjects (128 black and 179 white) and 356 hypertensive subjects (155 black and 201 white). A polymerase chain reaction-based single-stranded conformational polymorphism method with direct sequencing of the bands of interest was used to detect the two frequently occurring beta2-adrenergic receptor variants (Arg16-->Gly, Gln27-->Glu).

RESULTS

No significant differences in the distributions of alleles and genotypes of the tested beta2-adrenergic receptor variants were found between normotensive and hypertensive groups from either black or white Americans (all P > .05). There was a marked interethnic difference in the frequency of the Gln27-->Glu beta2-adrenergic receptor polymorphism in both normotensive and hypertensive subjects. In normotensive white subjects, the variant Glu27 allele (35.2% versus 18.0%; P < .0001) and Glu27 homozygous genotype (14.0% versus 4.7%; P < .01) were more common than in black subjects. Similarly, in hypertensive white subjects, the variant Glu27 allele (35.8% versus 18.4%; P < .0001) and the Glu27 homozygous genotype (15.9% versus 2.6%; P < .0001) were more common than in black subjects.

CONCLUSIONS

These data suggest that although there are marked ethnic differences in their distribution, the common genetic polymorphisms of the human beta2-adrenergic receptor gene do not cosegregate with the presence of hypertension in either black or white Americans.