Retained Metabolic Flexibility of the Failing Human Heart

BACKGROUND

The failing heart is traditionally described as metabolically inflexible and oxygen starved, causing energetic deficit and contractile dysfunction. Current metabolic modulator therapies aim to increase glucose oxidation to increase oxygen efficiency of adenosine triphosphate production, with mixed results.

METHODS

To investigate metabolic flexibility and oxygen delivery in the failing heart, 20 patients with nonischemic heart failure with reduced ejection fraction (left ventricular ejection fraction 34.9±9.1) underwent separate infusions of insulin+glucose infusion (I+G) or Intralipid infusion. We used cardiovascular magnetic resonance to assess cardiac function and measured energetics using phosphorus-31 magnetic resonance spectroscopy. To investigate the effects of these infusions on cardiac substrate use, function, and myocardial oxygen uptake (MVo2), invasive arteriovenous sampling and pressure-volume loops were performed (n=9).

RESULTS

At rest, we found that the heart had considerable metabolic flexibility. During I+G, cardiac glucose uptake and oxidation were predominant (70±14% total energy substrate for adenosine triphosphate production versus 17±16% for Intralipid; P=0.002); however, no change in cardiac function was seen relative to basal conditions. In contrast, during Intralipid infusion, cardiac long-chain fatty acid (LCFA) delivery, uptake, LCFA acylcarnitine production, and fatty acid oxidation were all increased (LCFA 73±17% of total substrate versus 19±26% total during I+G; P=0.009). Myocardial energetics were better with Intralipid compared with I+G (phosphocreatine/adenosine triphosphate 1.86±0.25 versus 2.01±0.33; P=0.02), and systolic and diastolic function were improved (LVEF 34.9±9.1 baseline, 33.7±8.2 I+G, 39.9±9.3 Intralipid; P<0.001). During increased cardiac workload, LCFA uptake and oxidation were again increased during both infusions. There was no evidence of systolic dysfunction or lactate efflux at 65% maximal heart rate, suggesting that a metabolic switch to fat did not cause clinically meaningful ischemic metabolism.

CONCLUSIONS

Our findings show that even in nonischemic heart failure with reduced ejection fraction with severely impaired systolic function, significant cardiac metabolic flexibility is retained, including the ability to alter substrate use to match both arterial supply and changes in workload. Increasing LCFA uptake and oxidation is associated with improved myocardial energetics and contractility. Together, these findings challenge aspects of the rationale underlying existing metabolic therapies for heart failure and suggest that strategies promoting fatty acid oxidation may form the basis for future therapies.

Investigating myocardial energetic deficit across the spectrum of cardiac disease

Introduction

The phosphocreatine-to-adenosine triphosphate ratio (PCr/ATP) is a sensitive marker of the energetic state of the heart and can be reliably measured non-invasively using 31Phosphorus magnetic resonance spectroscopy (31P-MRS). Derangements in cardiac energetics are a distinctive feature in the pathophysiology of several cardiac diseases, and thus potential therapeutic targets.

Purpose

We sought to compare cardiac PCr/ATP across a range of cardiac pathologies.

Methods

Using a 3D chemical shift 31P spectral acquisition we recorded PCr/ATP in 515 participants: athletes (n=17), healthy controls with normal weight (n=148), overweight (n=67) and with obesity (n=73), diabetes (n=23), heart failure with preserved ejection fraction (HFpEF) (n=33), heart failure with reduced ejection fraction (HFrEF) (n=63), amyloid (n=9), severe aortic stenosis (AS) (n=29), severe mitral regurgitation (MR) (n=18), and hypertrophic cardiomyopathy (HCM) (n=35).

Results

A spectrum of myocardial PCr/ATP exists ranging from normal in athletes (2.23±0.28) and those with normal weight (2.05±0.38) to severely impaired in severe MR (1.56±0.32) and cardiac amyloid (1.34±0.19, Figure 1). Despite normal systolic function (all LVEF &gt;57%) those living with obesity and diabetes have lower PCr/ATP than normal (all p&lt;0.001). In all groups with HF, regardless of aetiology, myocardial energetics were impaired (all p&lt;0.001). Across the whole cohort PCr/ATP was negatively correlated with body mass index (r −0.28, p&lt;0.001), age (r −0.34, p&lt;0.001) and LV mass (r −0.1, p&lt;0.001). PCr/ATP was not related to systolic or diastolic blood pressure in these cohorts.

Conclusions

We demonstrate a spectrum of energetic deficit in cardiac disease and this is affected by not only myocardial pathology but also by obesity and age. Derangements in myocardial energetics are present in myocardial pathologies independent of underlying aetiology.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): We acknowledge support from the British Heart Foundation Oxford Center of Research Excellence.

Left ventricular kinetic energy across heart failure subgroups and subclinical diastolic dysfunction

Background

Diastolic dysfunction is a common finding in heart failure with preserved ejection fraction (HFpEF) and is considered a key mechanism for limiting exercise performance. Meanwhile, subclinical diastolic dysfunction (SDD) without heart failure is a growing concern and may be common in the general population [1,5[. The kinetic energy (KE) of intracardiac blood flow reflects the work spent on accelerating blood [3] and may provide a novel window into diastolic filling dynamics [2,4]. Our aim was therefore to quantify left ventricular KE in HFpEF patients and compare with healthy controls, subjects with SDD, and heart failure patients with moderately reduced (HFmrEF) or reduced ejection fraction (HFrEF).

Methods

We studied 12 healthy controls, 22 healthy subjects with 1–2 echocardiographic criteria of diastolic dysfunction (SDD), 16 HFpEF, 9 HFmrEF, and 16 HFrEF patients. All subjects underwent CMR imaging at 1.5T with acquisition of anatomical cines and 4D flow from a box covering the heart. The LV was delineated over the cardiac cycle and KE inside the segmentation calculated as 0.5 × m × v2, where v is the instantaneous velocity vector magnitude and m is blood mass. Group comparisons of peak and average values were performed using Kruskal-Wallis test with Dunn's uncorrected post hoc test. Significance was assigned at p&lt;0.05. Median values are given.

Results

Groups were similar with regard to sex, blood pressure, and body surface area. HFpEF (median 72 years) and HFrEF patients (67 years) were significantly older than subjects with SDD (62 years, p=0.001). Examples of KE are shown in Fig. 1. Systolic peak and average KE did not differ between groups (p=0.81 and p=0.54 respectively, Fig. 2). Diastolic peak KE was higher in all groups of heart failure compared to controls (p&lt;0.03 for all) and diastolic average KE was higher in HFmrEF and HFrEF compared to controls (p&lt;0.02). The standard deviation for SDD was wider than in controls (1.6 mJ vs 0.8 mJ for systolic peaks, 2.7 mJ vs 1.1 mJ for diastolic peaks) and more closely resembled the HFpEF group (2.1 mJ in systole, 2.3 mJ in diastole).

Conclusions

Systolic kinetic energy expenditures are on average similar between controls, subjects with subclinical diastolic dysfunction, and heart failure patients, indicating that cardiac pumping involves approximately the same amount of systolic acceleration for a given afterload. Conversely, diastolic KE was found more dispersed both in heart failure and in asymptomatic individuals with subclinical diastolic dysfunction. Higher peak values of KE were seen in diastole for all types of heart failure including HFpEF, indicating more work is spent filling the ventricle. Measurements of KE in diastole could potentially be a new tool for assessment of heart failure, including early stages of disease development in some individuals with subclinical diastolic dysfunction.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Swedish Heart Lung FoundationRegion of Scania, Sweden

Invasive validation of pressure-volume loops derived from cardiovascular magnetic resonance imaging and brachial blood pressure in heart failure patients

Introduction

Left ventricular (LV) pressure-volume (PV) loops provide gold-standard physiological information but require invasive measurements of ventricular intracavity pressure, limiting clinical and research applications. Recent development has seen the introduction of non-invasively computed PV loops from cardiovascular magnetic resonance (CMR) volumetry and a brachial blood pressure measurement. The approach combines LV volumes with a time-varying elastance function to compute time-resolved LV pressures and was validated on invasive pressure data from a porcine model. The method is readily implemented using standard CMR sequences and provides measures of hemodynamic parameters including stroke work, myocardial efficiency, and contractile state. However, the method remains to be validated in patients using invasive left ventricular pressure recordings.

Purpose

To validate for the first time in human patients the performance of non-invasively computed PV loops against invasive measures.

Methods

Four heart failure patients underwent two subsequent sessions of CMR cine imaging and simultaneous brachial blood pressure measurement, with intravenous administration of two different vasoactive drugs, resulting in two different haemodynamic states for each patient. LV catheterization was then conducted with repeat administration of the same infusions. Pressure-volume loops were computed from CMR volumes combined with 1) a time-varying elastance function scaled to brachial blood pressure and temporally stretched to match volume data, and 2) invasive pressures averaged from multiple sampled beats. Method comparison was conducted using linear regression and Bland-Altman analysis.

Results

Figure 1 shows non-invasively derived PV loop parameters compared to invasive data. The non-invasive method demonstrated strong correlations and low bias for stroke work (R2=0.97, bias 4.6%, p&lt;0.0001), potential energy (R2=0.83, bias 1.5%, p=0.001), end-systolic pressure-volume relationship (R2=0.90, bias 5.4%, p=0.0003), energy per ejected volume (R2=0.93, bias 3.5%, p=0.0001), ventricular efficiency (R2=0.99, bias 1.1%, p&lt;0.0001), arterial elastance (R2=0.87, bias −7.8%, p=0.0006), and mean external power (R2=0.89, bias 4.6%, p=0.0005).

Conclusions

Pressure-volume loops can be precisely and accurately computed from cardiovascular magnetic resonance imaging and brachial cuff blood pressure in humans, and is ready for use in research applications.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Swedish Heart Lung Foundation

Intraventricular hemodynamic forces do not differentiate between healthy controls and heart failure patients with preserved ejection fraction

Background

Hemodynamic force analysis has been proposed as a noninvasive marker of cardiac function. In a recent study, longitudinal (apical-to-basal) hemodynamic forces were derived from anatomical MRI images and found decreased in heart failure with preserved ejection fraction (HFpEF) patients compared to controls, indicating a potential use for prognostication and testing of therapeutic response. This issue has not been investigated using the reference method of measurement.

Purpose

To investigate whether intraventricular hemodynamic forces computed using gold-standard cardiac magnetic resonance flow maps can reproducibly differentiate between healthy controls and HFpEF patients.

Methods

4D flow data were acquired in 59 subjects through cardiac magnetic resonance imaging using a 1.5T scanner (Siemens Healthcare, Erlangen, Germany). Hemodynamic forces within the LV were computed across the cardiac cycle using the Navier-Stokes equation to find the global pressure gradient, which was then integrated over the LV volume to produce the instantaneous hemodynamic force (unit: Newton) and subsequently normalized to ventricular volume, resulting in a force-volume index (N/l). Average longitudinal forces (root mean square, FRMS) were quantified over the entire cardiac cycle, with and without volume normalization.

Results

We studied 33 healthy subjects, 14 patients with HFpEF, 6 patients with HFmEF and 6 patients with HFrEF. Groups were similar with regards to sex, cardiac output, heart rate, systolic and diastolic blood pressure, and body surface area.

Volume-normalized FRMS did not differ between controls and HFpEF (0.86±0.19 vs. 0.75±0.19 N/l, p=0.08) while lower values were found in HFmEF (0.60±0.19 N/l, p=0.004) and HFrEF (0.38±0.15 N/l, p&lt;0.0001) compared to controls (Figure 1A). There was a significant positive correlation between EF and FRMS, both for the entire population (R2 = 0.54, Figure 1B) and for patients (R2 = 0.67, p&lt;0.0001 for both). Importantly, non-normalized FRMS did not differ between controls (Figure 1C, 0.10±0.03 N) and HFpEF (0.09±0.03 N, p=0.25), HFmEF (0.11±0.02 N, p=0.18) or HFrEF (0.09±0.02 N, p=0.67). Moreover, no correlation was seen between non-normalized FRMS and EF (Figure 1D).

Conclusions

Hemodynamic forces computed from reference standard 4D flow CMR data do not differentiate between healthy controls and HFpEF patients regardless of whether volume normalization is used or not. Our findings do not support a role for hemodynamic forces in HFpEF assessment.

Figure 1. (A) Volume-normalized hemodynamic forces over the entire cardiac cycle (lines: average values, shaded area: ±1SD for HFpEF), and (B) variation of volume-normalized average force, FRMS, with left ventricular ejection fraction (LVEF). (C), (D): When indexing to LV volume was not performed, the differences between groups was attenuated, and no correlation was seen between EF and FRMS.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swedish Heart and Lung Foundation, Region of Scania

Validation and reproducibility of cardiovascular 4D-flow MRI from two vendors using 2 × 2 parallel imaging acceleration in pulsatile flow phantom and in vivo with and without respiratory gating

Background

4D-flow magnetic resonance imaging (MRI) is increasingly used.

Purpose

To validate 4D-flow sequences in phantom and in vivo, comparing volume flow and kinetic energy (KE) head-to-head, with and without respiratory gating.

Material and Methods

Achieva dStream (Philips Healthcare) and MAGNETOM Aera (Siemens Healthcare) 1.5-T scanners were used. Phantom validation measured pulsatile, three-dimensional flow with 4D-flow MRI and laser particle imaging velocimetry (PIV) as reference standard. Ten healthy participants underwent three cardiac MRI examinations each, consisting of cine-imaging, 2D-flow (aorta, pulmonary artery), and 2 × 2 accelerated 4D-flow with (Resp+) and without (Resp−) respiratory gating. Examinations were acquired consecutively on both scanners and one examination repeated within two weeks. Volume flow in the great vessels was compared between 2D- and 4D-flow. KE were calculated for all time phases and voxels in the left ventricle.

Results

Phantom results showed high accuracy and precision for both scanners. In vivo, higher accuracy and precision (P < 0.001) was found for volume flow for the Aera prototype with Resp+ (–3.7 ± 10.4 mL, r = 0.89) compared to the Achieva product sequence (–17.8 ± 18.6 mL, r = 0.56). 4D-flow Resp− on Aera had somewhat larger bias (–9.3 ± 9.6 mL, r = 0.90) compared to Resp+ (P = 0.005). KE measurements showed larger differences between scanners on the same day compared to the same scanner at different days.

Conclusion

Sequence-specific in vivo validation of 4D-flow is needed before clinical use. 4D-flow with the Aera prototype sequence with a clinically acceptable acquisition time (<10 min) showed acceptable bias in healthy controls to be considered for clinical use. Intra-individual KE comparisons should use the same sequence.

Altered biventricular hemodynamic forces in patients with repaired tetralogy of Fallot and right ventricular volume overload because of pulmonary regurgitation

Intracardiac hemodynamic forces have been proposed to influence remodeling and be a marker of ventricular dysfunction. We aimed to quantify the hemodynamic forces in patients with repaired tetralogy of Fallot (rToF) to further understand the pathophysiological mechanisms as this could be a potential marker for pulmonary valve replacement (PVR) in these patients. Patients with rToF and pulmonary regurgitation (PR) > 20% ( n = 18) and healthy control subjects ( n = 15) underwent MRI, including four-dimensional flow. A subset of patients ( n = 8) underwent PVR and MRI after surgery. Time-resolved hemodynamic forces were quantified using 4D-flow data and indexed to ventricular volume. Patients had higher systolic and diastolic left ventricular (LV) hemodynamic forces compared with control subjects in the lateral-septal/LV outflow tract ( P = 0.011 and P = 0.0031) and inferior-anterior ( P < 0.0001 and P < 0.0001) directions, which are forces not aligned with blood flow. Forces did not change after PVR. Patients had higher RV diastolic forces compared with control subjects in the diaphragm-right ventricular (RV) outflow tract (RVOT; P < 0.001) and apical-basal ( P = 0.0017) directions. After PVR, RV systolic forces in the diaphragm-RVOT direction decreased ( P = 0.039) to lower levels than in control subjects ( P = 0.0064). RV diastolic forces decreased in all directions ( P = 0.0078, P = 0.0078, and P = 0.039) but were still higher than in control subjects in the diaphragm-RVOT direction ( P = 0.046). In conclusion, patients with rToF and PR had LV hemodynamic forces less aligned with intraventricular blood flow compared with control subjects and higher diastolic RV forces along the regurgitant flow direction in the RVOT and that of tricuspid inflow. Remaining force differences in the LV and RV after PVR suggest that biventricular pumping does not normalize after surgery. NEW & NOTEWORTHY Biventricular hemodynamic forces in patients with repaired tetralogy of Fallot and pulmonary regurgitation were quantified for the first time. Left ventricular hemodynamic forces were less aligned to the main blood flow direction in patients compared with control subjects. Higher right ventricular forces were seen along the pulmonary regurgitant and tricuspid inflow directions. Differences in forces versus control subjects remain after pulmonary valve replacement, suggesting that altered biventricular pumping does not normalize after surgery.

Differential effects of fluticasone and montelukast on allergen-induced asthma

Early asthmatic responses (EAR) and late asthmatic responses (LAR) to allergen are induced by the local release of a series of bronchoconstrictor mediators, including leukotrienes and histamine. Both anti-leukotrienes and other anti-asthma drugs, such as inhaled glucocorticoids, have been shown to reduce both EAR and LAR. The aim of the present study was to directly compare the effects of regular treatment with an oral anti-leukotriene, montelukast (Mont; 10 mg once daily, for 8 days), and an inhaled glucocorticoid [fluticasone propionate (FP) 250 microg twice daily for 8 days] on the EAR and LAR to an inhaled allergen challenge. Patients with a documented EAR and LAR at a screening visit were randomized to these treatments, or placebo, in a double-blind, double-dummy, crossover fashion. Allergen challenge at a dose causing both an EAR and LAR was given on the eighth day of treatment. The maximum fall in FEV1 during the EAR was 17.8% during placebo treatment, 8.3% during Mont and 16.3% during FP (P <0.05 for Mont vs placebo). The maximum fall during the EAR was 13.8% during placebo treatment, 11.8% during Mont and 2% during FP treatment (P <0.05 for FP vs placebo and FP vs Mont). PC20 methacholine was significantly higher 24 h after allergen challenge during FP-treatment compared with Mont (P <0.05). Both montelukast and fluticasone reduced the relative amount of sputum eosinophils after allergen compared with placebo treatment. This study shows that anti-leukotrienes are effective to attenuate the EAR, whereas inhaled glucocorticoids are more effective than anti-leukotrienes in attenuating the EARs and improves bronchial hyperresponsiveness to a greater extent. In conclusion, inhaled glucocorticoids have overall greater efficacy than oral anti-leukotrienes to attenuate allergen-induced airway responses in mild asthmatic patients.

Bronchodilation by an inhaled VPAC(2) receptor agonist in patients with stable asthma

BACKGROUND

The synthetic vasoactive intestinal peptide (VIP) analogue Ro 25-1553 is a selective VIP-PACAP type 2 (VPAC(2)) receptor agonist that causes a bronchodilatory effect in guinea pigs in vivo. The effect of Ro 25-1553 given by inhalation to patients with asthma was studied and compared with that of a long acting beta(2) adrenoceptor agonist.

METHODS

Twenty four patients with moderate stable asthma participated in a double blind, randomised, placebo controlled, crossover study. The primary variable was bronchodilatory effect (increase in forced expiratory volume in 1 second, FEV(1)) after inhalation of Ro 25-1553 (100 microg or 600 microg) and formoterol (4.5 microg), respectively. Putative side effects were characterised by monitoring sitting blood pressure, serum potassium, electrocardiography and echocardiography.

RESULTS

Inhalation of 600 microg Ro 25-1553 caused a rapid bronchodilatory effect (geometric mean increase in FEV(1) compared with placebo) within 3 minutes of 6% (95% CI 4 to 9), as did inhalation of formoterol (8% (95% CI 5 to 10)). The corresponding maximum bronchodilatory effect during 24 hours was similar for 600 microg Ro 25-1553 (7% (95% CI 4 to 10)) and the reference bronchodilator formoterol (10% (95% CI 7 to 12)). However, for both doses of Ro 25-1553 the bronchodilatory effect was attenuated 5 hours after inhalation whereas formoterol still had a bronchodilatory effect 12 hours after inhalation. Neither Ro 25-1553 nor formoterol produced any clinically relevant side effects. No drug related difference in adverse events was observed.

CONCLUSION

Inhalation of a synthetic selective VPAC(2) receptor agonist constitutes a promising approach for bronchodilation in patients with asthma.

The therapeutic ratio of R-albuterol is comparable with that of RS-albuterol in asthmatic patients

BACKGROUND

It has been suggested that R-albuterol produces bronchodilation that is comparable with that of racemic albuterol (RS-albuterol) on a 4:1 dose-for-dose basis but systemic side effects on a 2:1 basis, implying better therapeutic ratio for R-albuterol.

OBJECTIVE

We sought to carefully compare the bronchodilating and systemic effects of R- and RS-albuterol by using a crossover study design.

METHODS

Twenty asthmatic patients (15.1%-28.7% FEV(1) reversibility) were given R-albuterol (6.25-1600 microg), S-albuterol (6.25-1600 microg), RS-albuterol (12.5-3200 microg), or placebo in a crossover, double-blind, placebo-controlled fashion. Cumulative doses were given with a Mefar dosimeter, and FEV(1), heart rate, and plasma K(+) levels were measured 20 minutes after each dose.

RESULTS

Both R- and RS-albuterol produced dose-related improvement in FEV(1) and, at higher doses, increased heart rate and decreased plasma K(+) levels. Neither placebo nor S-albuterol had any significant effect. Individual estimates of the potency ratio for R-albuterol/RS-albuterol were calculated and summarized across all subjects. The geometric mean potency ratio for effects on FEV(1) was 1.9 (95% CI, 1.3-2.8), on HR of 1.9 (95% CI, 1.3-2.9), and on K(+) level of 1.7 (95% CI, 1.3-2.1).

CONCLUSION

All pharmacologic effects of RS-albuterol reside with the R-enantiomer, and S-albuterol is clinically inactive. The R-albuterol/RS-albuterol potency ratios for local (FEV(1)) and systemic effects (heart rate and K(+)) are similar, suggesting a comparable therapeutic ratio for R-albuterol and RS-albuterol in asthmatic subjects.

Exudation of plasma and production of thromboxane in human bronchi after local bradykinin challenge

Plasma exudation has been suggested to be an important component of the inflammatory response in asthma. Bradykinin elicits many of the features of asthma, including bronchoconstriction, cough, plasma exudation and mucus secretion. In an attempt to quantify local plasma exudation, we have employed a novel low-trauma technique with the aim of challenging and lavaging a central part of the bronchial tree, by selecting a medium sized bronchus. A fibreoptic bronchoscopy was performed in non-smoking healthy volunteers. The instrument was placed proximally in the right upper lobe bronchus. A plastic catheter, equipped with an inflatable latex balloon, was inflated with air (2-4 cmH2O). A solution (100 microl of either two different concentrations of bradykinin: 0.09 and 0.9 mg ml(-1) or normal saline) was instilled through the catheter and distal to the balloon. Eight minutes later a lavage procedure with 10 ml of saline was performed through the catheter. The procedure was then repeated twice, with the other solutions, but from the lingular and middle lobe bronchi. All solutions were given in a blinded fashion, and two different studies were performed. Lavage concentrations of albumin and IgG were quantified as measurements of plasma exudation. In our first study we found that bradykinin challenge significantly increased concentrations of albumin and IgG. In study two, there was no numeric increase in plasma proteins after local bradykinin challenge, but the concentration of thromboxane was significantly increased in lavages from bradykinin-challenged bronchi. Thus, local bronchial administration of bradykinin has the capacity to induce exudation of large plasma macromolecules into the bronchial lumen, as well as local thromboxane production.

Onset of bronchodilation of budesonide/formoterol vs. salmeterol/fluticasone in single inhalers

Combinations of inhaled glucocorticoids and long-acting beta2-agonists in the same inhaler device have become available in recent years. In this double-blind, randomized, placebo-controlled and crossover study we have evaluated the onset of action of budesonide and formoterol in a single inhaler (Symbicort Turbuhaler) and that of the fixed combination of salmeterol and fluticasone (Seretide Diskus). Thirty patients with a mean FEV1 of 2.54 l (range: 1.48-4.28) and a mean inclusion reversibility in FEV1 of 19.1% were included. Single doses of budesonide/formoterol 160/4.5 microg and 2x (160/4.5) microg, salmeterol/fluticasone 50/250 microg, or placebo were given. Serial measurements of FEV1 were performed over 3 h. The combination of one or two inhalations of budesonide/formoterol showed a faster onset of action than salmeterol/fluticasone, both evaluated as mean FEV1 at 3 min (2.74, 2.75 and 2.56 l respectively P<0.001 for both doses of budesonide/formoterol), or as average FEV1 from 0 to 15 min (2.80, 2.83 and 2.67 l respectively P<0.001 for both doses of budesonide/formoterol). For placebo, mean FEV1 at 3 min was 2.46 l, and the average FEV1 at 0-15 min was 2.50 l. Furthermore, budesonide/formoterol at both doses resulted in higher FEV1 than salmeterol/fluticasone at 3 h. We conclude that the combination of budesonide/formoterol has a faster onset of action than salmeterol/fluticasone.

Polymer versus monomer as displacer in immobilized metal affinity chromatography

Successful immobilized metal affinity chromatography (IMAC) of proteins on Cu2+-iminodiacetic acid Sepharose has been carried out in a displacement mode using a synthetic copolymer of vinyl imidazole and vinyl caprolactam [poly(VI-VCL)] as a displacer. Vinyl caprolactam renders the co-polymer with the thermosensitivity, e.g., property of the co-polymer to precipitate nearly quantitatively from aqueous solution on increase of the temperature to 48 degrees C. A thermostable lactate dehydrogenase from the thermophilic bacterium Bacillus stearothermophilus modified with a (His)6-tag [(His)6-LDH] has been purified using an IMAC column. For the first time it was clearly demonstrated that a polymeric displacer [poly(VI-VCL)] was more efficient compared to a monomeric displacer (imidazole) of the same chemical nature, probably due to the multipoint interaction of imidazole groups within the same macromolecule with one Cu2+ ion. Complete elution of bound (His)6-LDH has been achieved at 3.7 mM concentration of imidazole units of the co-polymer (5 mg/ml), while this concentration of free imidazole was sufficient to elute only weakly bound proteins. Complete elution of (His)6-LDH by the free imidazole was achieved only at concentrations as high as 160 mM. Thus, it was clearly demonstrated, that the efficiency of low-molecular-mass displacer could be improved significantly by converting it into a polymeric displacer having interacting groups of the same chemical nature.

Protein displacement in dye-ligand chromatography using neutral and charged polymers

Displacement chromatography was demonstrated to perform separations efficiently under mass-overloaded conditions, offering advantages such as increased product recovery and purity, superior resolving power, and concentration and purification in a single processing step. The use of water-soluble polymers for protein displacement in dye-ligand chromatography was initiated in our laboratory. The polymers for displacement were selected using differences spectroscopy to monitor their interactions with a dye-ligand in solution. Non-charged polymers such as poly(N-vinyl pyrrolidone) and poly(N-vinyl caprolactam) efficiently displaced lactate dehydrogenase from porcine muscle from a Blue Sepahrose column. The latter polymer, being thermosensitive, could be easily removed from the eluate and recovered by precipitation at 45 degrees C and low-speed centrifugation. The positively charged polymer poly(ethylene imine) proved to be an even more efficient displacer. The dye-ligand column could be regenerated after application of displacer either by washing with a solution of the soluble ligand Cibacron Blue (in the case of non-charged polymers) or by washing with highly alkaline solutions containing polyanions (in the case of poly(ethylene imine)) The latter formed a soluble complex with poly(ethylene imine) and stripped the column from the polymer.

Equivalent therapeutic ratio of salbutamol given by Turbuhaler and Diskus

Some inhalers have been claimed to give better deposition, resulting in higher efficacy. In a previous study we did not find any evidence of different potency of salbutamol given either via pMDI or Turbuhaler. The aim of the present study was to compare the efficacy and safety of salbutamol given via Diskus or Turbuhaler. Twenty-five asthmatics with step-wise reversible airflow obstruction (total reversibility of at least 15%) were included in a randomized, double-dummy, placebo-controlled cross-over study. On each study day, the patients were given placebo repeatedly, or cumulative doses of 200, 400, 800, 1600 and 3200 microg salbutamol given via either device (double-blind, placebo-controlled). Salbutamol caused a dose-related increase in FEV1 when given by Diskus or Turbuhaler. The improvement in FEV1 was similar regardless of whether salbutamol was given via Diskus or Turbuhaler, at equivalent microgram doses. After a total cumulative dose of 3200 microg, mean FEV1 for Diskus was 2.46 l (change from baseline of 20.5%), for Turbuhaler 2.50 l (change from baseline 24.6%) and for placebo 2.11 l (3% change from baseline). After correcting for different baseline differences, the percentage difference between Diskus and Turbuhaler was -1.8% (P = 0.2). Systemic effects (potassium and heart rate) did not differ between Diskus or Turbuhaler. We conclude that the efficacy of salbutamol given at equivalent microgram doses, as well as side-effects, are comparable when the drug is given via Diskus or Turbuhaler. The present data shows that salbutamol given by these devices have similar therapeutic ratios.

Similar bronchodilation with formoterol delivered by aerolizer or turbuhaler

BACKGROUND

In many countries, two dry powder formulations of inhaled formoterol are available for clinical use; one uses a single-dose device (Foradil, Aerolizer), and the other uses a multiple-dose device (Oxis, Turbuhaler).

OBJECTIVES

To study the bronchodilating effect of formoterol 12 mg when delivered via the Aerolizer and Turbuhaler devices over 12 h.

STUDY DESIGN

Randomized, double-blind, placebo controlled crossover study. Forced expiratory volume in one second (FEV1) was monitored during a 12 h period.

PATIENTS

Nineteen nonsmoking asthma patients were included in the trial on the basis of reversibility of symptoms in response to inhaled salbutamol (either 200 or 400 mg given cumulatively; minimum reversibility 15%).

RESULTS

There were no significant differences between the two dry powder devices regarding the change from baseline of FEV1 over 12 h, the area under the curve of FEV1 over 12 h or the maximum value of FEV1. The improvement in FEV1 with formoterol 12 mg versus placebo was highly significant for both devices.

CONCLUSIONS

Formoterol is similarly effective when used as a dry powder when given by either Aerolizer or the Turbuhaler.

Equivalent bronchodilation with salbutamol given via pMDI or turbuhaler

Several breath-activated multidose powder devices for inhaled anti-asthma drugs are now available. Some of these inhalers have been argued to give higher drug deposition in the airways than conventional pressurized metered dose inhalers (pMDI). The aim of the present study was to compare the efficacy and safety of salbutamol given via pMDI or Turbuhaler (both 100 microgram per inhalation). Adult asthmatic patients of either sex (n = 22) and with reversible airflow obstruction were included in a randomized, placebo-controlled study. On the study days, salbutamol was given with increasing doses (200 to 3,200 microgram cumulative) or placebo, via pMDI or Turbuhaler. A dose-related increase in FEV1 was observed after administration of salbutamol given via either device, versus placebo. The improvement in FEV1 was similar whether salbutamol was given via pMDI or Turbuhaler, at microgram equivalent doses. After a total cumulative dose of 3,200 microgram, mean FEV1 for Turbuhaler was 2.98 (change from baseline of 23.1%), for pMDI 2.93 (change from baseline of 23.6%), and for placebo 2.36 (change from baseline of 0. 42%). Changes in potassium, glucose, and heart rate did not show any significant differences between pMDI and Turbuhaler. We conclude that the efficacy of salbutamol is comparable when the drug is given via the Turbuhaler or pMDI.

Analysis of nonpolar heterocyclic amines in cooked foods and meat extracts using gas chromatography-mass spectrometry

Heat processing of muscle foods gives rise to the formation of mutagenic and carcinogenic heterocyclic amines, often at ng/g levels. A gas chromatographic-mass spectrometric (GC-MS) technique was introduced for the analysis of nonpolar heterocyclic amines in common cooked meats, pan residues, and meat extracts after solid-phase extraction. The mutagenic heterocyclic amines 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-9H-pyrido[2,3-b]indole (A alpha C) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alpha C) were identified in several samples in amounts up to 8 ng/g. Also the comutagenic substances 1-methyl-9H-pyrido [3,4-b]indole (harman) and 9H-pyrido[3,4-b]indole (norharman) were detected in the samples in amounts up to almost 200 ng/g. The GC-MS method can be applied without derivatisation of the sample. The technique offers high chromatographic efficiency, yielding detection limits for pure references in the range 0.1-2 ng per injection.

Purification of proteins by the use of hydrophobic zeolite Y

Hydrophobic zeolite Y can be used as a fast and efficient and inexpensive matrix in the purification of proteins from crude extracts. Preferably the zeolite can be used in the first purification step, replacing the commonly used precipitation techniques with (NH4)2SO4 or ethanol. The time required for the zeolite prefractionation was a few hours compared to the much more time consuming precipitation procedure which demands centrifugation and subsequent dialysis. Proteins can be absorbed on the zeolite either in order to remove undesired proteins or to be subsequently eluted from the zeolite in order to achieve purification and concentration. Removal of undesired proteins is exemplified by the purification of horseradish peroxidase from a crude extract. The zeolite procedure enhanced the specific activity five times and provided a yield similar to that which was obtained by the use of standard procedures, (NH4)2SO4 fractionation and ion-exchange chromatography. Binding and subsequent elution of proteins from the zeolite is exemplified by the purification of monoclonal antibodies from hybridoma culture supernatants. Proteins were desorbed from the zeolite by the use of polyethylene glycol 600 and this procedure yielded a purification factor of 5.

Objective and subjective bronchodilation over 12 hours after inhaled formoterol: individual responses

The aim of the present study was to compare the duration of bronchodilation obtained with 12 micrograms formoterol and 24 micrograms formoterol with that of 200 micrograms salbutamol over 12 hr. Thirteen stable asthmatics (mean age 59 years, asthma duration 7 years, mean FEV1 56% predicted, and reversibility to beta-adrenoceptor stimulation 36%) were studied in a double-blind crossover study. Lung function test (FEV1 and FVC), heart rate, tremor, and subjective effects were recorded before and 30 min after the test doses and every hour up to 12 hr. The test doses were randomized and given double-blindly as two puffs using a spacer. The median duration of effect, defined as time when FEV1 fell below 20% the maximum bronchodilating capacity, was longer than 12 hr for both formoterol doses, whereas it was 7 hr for salbutamol (p < 0.01). No difference between the two doses of formoterol was seen. The median of the patients' subjective evaluation of the duration of effect was 12 hr, more than 12 hr for 12 and 24 micrograms formoterol, respectively, and 8 hr for salbutamol (p < 0.01). Only 1 patient needed rescue medication on the 2 formoterol days. However, 6 patients inhaled rescue medication during treatment with salbutamol. There were no differences with regard to heart rate, blood pressure, subjective tremor, or palpitations. Formoterol, 12 micrograms and 24 micrograms, was shown to produce at least 12 hr of bronchodilating effect in most patients. However, there was considerable individual variation in duration of effect.

Inhaled formoterol during one year in asthma: a comparison with salbutamol

Eighteen patients, who had previously taken part in a 2 wk cross-over comparison between formoterol and salbutamol, now took part in a one year double-blind study comparing salbutamol 200 micrograms b.i.d. with formoterol 12 micrograms b.i.d. Additional doses were taken when needed and were recorded. Ten patients were started on formoterol and eight on salbutamol. After one month, the patients were allowed to shift to the alternative drug. Two patients withdrew from the study. At the end of the study, 13 of 16 patients were on formoterol, thus showing a long-lasting preference for this drug. Forced expiratory volume in one second (FEV1) dose-response curves for inhaled salbutamol were repeatedly recorded during the study, and no tachyphylaxis was found. One patient stopped taking inhaled steroids but continued taking formoterol and theophylline. He deteriorated with a decreased response to salbutamol. After re-introduction of inhaled steroids his condition improved. This case indicates that effective bronchodilator therapy may mask the deterioration of asthma.

Inhaled formoterol during one year in asthma: a comparison with salbutamol

Eighteen patients, who had previously taken part in a 2 wk cross-over comparison between formoterol and salbutamol, now took part in a one year double-blind study comparing salbutamol 200 micrograms b.i.d. with formoterol 12 micrograms b.i.d. Additional doses were taken when needed and were recorded. Ten patients were started on formoterol and eight on salbutamol. After one month, the patients were allowed to shift to the alternative drug. Two patients withdrew from the study. At the end of the study, 13 of 16 patients were on formoterol, thus showing a long-lasting preference for this drug. Forced expiratory volume in one second (FEV1) dose-response curves for inhaled salbutamol were repeatedly recorded during the study, and no tachyphylaxis was found. One patient stopped taking inhaled steroids but continued taking formoterol and theophylline. He deteriorated with a decreased response to salbutamol. After re-introduction of inhaled steroids his condition improved. This case indicates that effective bronchodilator therapy may mask the deterioration of asthma.

Formoterol, a new long-acting bronchodilator for inhalation

The aim of this study was to evaluate if treatment with inhaled formoterol is appreciated by asthmatics and whether it causes tachyphylaxis. Twenty stable asthmatics were included in a randomized, double-blind, crossover study. They were treated for two weeks either with formoterol or salbutamol, with one week washout inbetween. They were given 12 micrograms formoterol or 200 micrograms salbutamol twice daily and instructed to use additional spray doses on demand. On a diary card they recorded the number of doses, asthma symptoms and peak expiratory flow rate (PEFR) before every dose. Forced expiratory volume in one second (FEV1) dose-response curves for salbutamol (total dose 1.3 mg) were performed before and after each treatment period to evaluate development of tachyphylaxis. There was a significant difference in favour of formoterol concerning symptoms, PEFR recordings, spray consumption, and preference. Fifteen patients preferred formoterol and two salbutamol. The dose-response curves before formoterol and before, as well as after salbutamol were almost identical. After formoterol the curve had changed; both basal and maximum values were higher than before. Thus, no evidence of tachyphylaxis was found, compared to the ordinary beta-stimulant treatment.

Formoterol, a new long-acting bronchodilator for inhalation

The aim of this study was to evaluate if treatment with inhaled formoterol is appreciated by asthmatics and whether it causes tachyphylaxis. Twenty stable asthmatics were included in a randomized, double-blind, crossover study. They were treated for two weeks either with formoterol or salbutamol, with one week washout inbetween. They were given 12 micrograms formoterol or 200 micrograms salbutamol twice daily and instructed to use additional spray doses on demand. On a diary card they recorded the number of doses, asthma symptoms and peak expiratory flow rate (PEFR) before every dose. Forced expiratory volume in one second (FEV1) dose-response curves for salbutamol (total dose 1.3 mg) were performed before and after each treatment period to evaluate development of tachyphylaxis. There was a significant difference in favour of formoterol concerning symptoms, PEFR recordings, spray consumption, and preference. Fifteen patients preferred formoterol and two salbutamol. The dose-response curves before formoterol and before, as well as after salbutamol were almost identical. After formoterol the curve had changed; both basal and maximum values were higher than before. Thus, no evidence of tachyphylaxis was found, compared to the ordinary beta-stimulant treatment.