Cardioprotective Effect of Empagliflozin and Circulating Ketone Bodies During Acute Myocardial Infarction

BACKGROUND

SGLT2i (sodium-glucose cotransporter-2 inhibitors) improve clinical outcomes in patients with heart failure, but the mechanisms of action are not completely understood. SGLT2i increases circulating levels of ketone bodies, which has been demonstrated to enhance myocardial energetics and induce reverse ventricular remodeling. However, the role of SGLT2i or ketone bodies on myocardial ischemia reperfusion injury remains in the dark. The objective of this study is to investigate the cardioprotective potential of empagliflozin and ketone bodies during acute myocardial infarction (MI).

METHODS

We used a nondiabetic porcine model of ischemia reperfusion using a percutaneous occlusion of proximal left anterior descending artery for 45 minutes. Animals received 1-week pretreatment with either empagliflozin or placebo prior to MI induction. Additionally, a third group received intravenous infusion of the ketone body BOHB (beta-hydroxybutyrate) during the MI induction. Acute effects of the treatments were assessed 4-hour post-MI by cardiac magnetic resonance and histology (thioflavin for area at risk, triphenyltetrazolium chloride staining for MI size). All animals were euthanized immediately postcardiac magnetic resonance, and heart samples were collected.

RESULTS

The area at risk was similar in all groups. Empagliflozin treatment increased BOHB levels. Empagliflozin-treated animals showed significantly higher myocardial salvage, smaller MI size (both by cardiac magnetic resonance and histology), less microvascular obstruction, and improved cardiac function (left ventricle ejection fraction and strain). Furthermore, empagliflozin-treated animals demonstrated reduced biomarkers of cardiomyocyte apoptosis and oxidative stress compared with placebo. The BOHB group showed similar results to the empagliflozin group.

CONCLUSIONS

One-week pretreatment with empagliflozin ameliorates ischemia reperfusion injury, reduces MI size and microvascular obstruction, increases myocardial salvage, preserves left ventricle systolic function, and lowers apoptosis and oxidative stress. Periprocedural intravenous infusion of BOHB during myocardial ischemia also induces cardioprotection, suggesting a role for BOHB availability as an additional mechanism within the wide spectrum of actions of SGLT2i.

Cardioprotective effect of empagliflozin in acute myocardial infarction: the role of ketone bodies availability

Background

The cardio-renal benefits of SGLT2i have been clearly established by clinical trials. Of interest, despite not having any effect on the incidence of classic atherothrombotic events (MI and strokes), patients receiving SGLT2i treatment had a higher chance of surviving myocardial infarction (MI).

Purpose

We aim to evaluate the cardioprotective potential of empagliflozin on acute myocardial infarction.

We postulate that the benefits of SGLT2-I are mediated via an increase in circulating ketone bodies (KBs) induced by SGLT2i, and its preferential myocardial utilization energetically benefits the heart to better withstand an ischemic event.

Methods

The study was undertaken in our non-diabetic porcine model of ischemia/reperfusion. Animals were allocated to either one-week pre-treatment with empagliflozin or placebo before MI-induction. A third group received IV infusion of KBs at the time of the MI- induction to serve as positive-control. The acute effects of the treatments were studied 24 hours after MI-induction by Cardiac Magnetic Resonance (CMR). Immediately post-CMR, animals were sacrificed and heart samples collected for molecular analysis.

Results

(see Table and Figure): Despite similar initial ischemic injury (area at risk) in all groups, empagliflozin was associated with a significantly higher myocardial salvage (MSI 23.7±9.7 vs 4.5±3.6%, p<0.001) and better preserved cardiac function (LVEF 41.3±3.1 vs 33±5.5%, p<0.009) compared with placebo. The infusion of KBs replicated in part the beneficial profile of the empagliflozin group (MSI 16.7±8.8 and LVEF 39.1±3.6%). Histological analysis showed less cardiomyocyte apoptosis and less oxidative stress

Conclusions

To the best of our knowledge, this is the first study evaluating in vivo the cardioprotective potential of a SGLT2 inhibitor in a well-stablished porcine translational model. Furthermore, effects are evaluated using the gold standard for visualization and quantification of MI, Cardiac Magnetic Resonance (CMR). Three are the main conclusions:

1. One-week treatment with empagliflozin raises circulating KBs levels and confers significant cardio-protection during a myocardial infarction. Acute post-MI benefits (greater myocardial salvage and better preserved cardiac function) are already seen within 24 hours as compared with placebo.

2. Periprocedural IV infusion of KBs induces similar benefits than the SGLT2-I group.

3. These observations strongly support our hypothesis that SGLT2 inhibition is associated with increased circulating KBs and its selective use as preferential myocardial source of energy as a potential mechanism of action involved in the cardio-renal benefits observed with SGLT2i.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Spanish Society of Cardiology. Research Fellowship Grant.

The Bottleneck Simulator: A Model-Based Deep Reinforcement Learning Approach

Deep reinforcement learning has recently shown many impressive successes. However, one major obstacle towards applying such methods to real-world problems is their lack of data-efficiency. To this end, we propose the Bottleneck Simulator: a model-based reinforcement learning method which combines a learned, factorized transition model of the environment with rollout simulations to learn an effective policy from few examples. The learned transition model employs an abstract, discrete (bottleneck) state, which increases sample efficiency by reducing the number of model parameters and by exploiting structural properties of the environment. We provide a mathematical analysis of the Bottleneck Simulator in terms of fixed points of the learned policy, which reveals how performance is affected by four distinct sources of error: an error related to the abstract space structure, an error related to the transition model estimation variance, an error related to the transition model estimation bias, and an error related to the transition model class bias. Finally, we evaluate the Bottleneck Simulator on two natural language processing tasks: a text adventure game and a real-world, complex dialogue response selection task. On both tasks, the Bottleneck Simulator yields excellent performance beating competing approaches.

SGLT2 is not expressed in pancreatic α- and β-cells, and its inhibition does not directly affect glucagon and insulin secretion in rodents and humans

Objective

Sodium-glucose cotransporter 2 (SGLT2) inhibitors (SGLT2i), or gliflozins, are anti-diabetic drugs that lower glycemia by promoting glucosuria, but they also stimulate endogenous glucose and ketone body production. The likely causes of these metabolic responses are increased blood glucagon levels, and decreased blood insulin levels, but the mechanisms involved are hotly debated. This study verified whether or not SGLT2i affect glucagon and insulin secretion by a direct action on islet cells in three species, using multiple approaches.

Methods

We tested the in vivo effects of two selective SGLT2i (dapagliflozin, empagliflozin) and a SGLT1/2i (sotagliflozin) on various biological parameters (glucosuria, glycemia, glucagonemia, insulinemia) in mice. mRNA expression of SGLT2 and other glucose transporters was assessed in rat, mouse, and human FACS-purified α- and β-cells, and by analysis of two human islet cell transcriptomic datasets. Immunodetection of SGLT2 in pancreatic tissues was performed with a validated antibody. The effects of dapagliflozin, empagliflozin, and sotagliflozin on glucagon and insulin secretion were assessed using isolated rat, mouse and human islets and the in situ perfused mouse pancreas. Finally, we tested the long-term effect of SGLT2i on glucagon gene expression.

Results

SGLT2 inhibition in mice increased the plasma glucagon/insulin ratio in the fasted state, an effect correlated with a decline in glycemia. Gene expression analyses and immunodetections showed no SGLT2 mRNA or protein expression in rodent and human islet cells, but moderate SGLT1 mRNA expression in human α-cells. However, functional experiments on rat, mouse, and human (29 donors) islets and the in situ perfused mouse pancreas did not identify any direct effect of dapagliflozin, empagliflozin or sotagliflozin on glucagon and insulin secretion. SGLT2i did not affect glucagon gene expression in rat and human islets.

Conclusions

The data indicate that the SGLT2i-induced increase of the plasma glucagon/insulin ratio in vivo does not result from a direct action of the gliflozins on islet cells.

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Gliflozins (SGLT2 and SGLT1/2 inhibitors) increase plasma glucagon/insulin ratio.

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SGLT2 is not expressed in rodent and human pancreatic α- and β-cells.

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SGLT1 is however expressed in human α-cells.

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SGLT2 and SGLT1/2 inhibitors do not directly affect glucagon and insulin secretion.

Modelling the asthma phenotype: impact of cigarette smoke exposure

Background

Asthmatics that are exposed to inhaled pollutants such as cigarette smoke (CS) have increased symptom severity. Approximately 25% of adult asthmatics are thought to be active smokers and many sufferers, especially in the third world, are exposed to high levels of inhaled pollutants. The mechanism by which CS or other airborne pollutants alter the disease phenotype and the effectiveness of treatment in asthma is not known. The aim of this study was to determine the impact of CS exposure on the phenotype and treatment sensitivity of rodent models of allergic asthma.

Methods

Models of allergic asthma were configured that mimicked aspects of the asthma phenotype and the effect of CS exposure investigated. In some experiments, treatment with gold standard asthma therapies was investigated and end-points such as airway cellular burden, late asthmatic response (LAR) and airway hyper-Reactivity (AHR) assessed.

Results

CS co-exposure caused an increase in the LAR but interestingly attenuated the AHR. The effectiveness of LABA, LAMA and glucocorticoid treatment on LAR appeared to be retained in the CS-exposed model system. The eosinophilia or lymphocyte burden was not altered by CS co-exposure, nor did CS appear to alter the effectiveness of glucocorticoid treatment. Steroids, however failed to reduce the neutrophilic inflammation in sensitized mice exposed to CS.

Conclusions

These model data have certain parallels with clinical findings in asthmatics, where CS exposure did not impact the anti-inflammatory efficacy of steroids but attenuated AHR and enhanced symptoms such as the bronchospasm associated with the LAR. These model systems may be utilised to investigate how CS and other airborne pollutants impact the asthma phenotype; providing the opportunity to identify novel targets.

Tiotropium bromide exerts anti-inflammatory effects during resistive breathing, an experimental model of severe airway obstruction

Introduction

Resistive breathing (RB), a hallmark of obstructive airway diseases, is characterized by strenuous contractions of the inspiratory muscles that impose increased mechanical stress on the lung. RB is shown to induce pulmonary inflammation in previous healthy animals. Tiotropium bromide, an anticholinergic bronchodilator, is also shown to exert anti-inflammatory effects. The effect of tiotropium on RB-induced pulmonary inflammation is unknown.

Methods

Adult rats were anesthetized, tracheostomized and breathed spontaneously through a two-way non-rebreathing valve. Resistances were connected to the inspiratory and/or expiratory port, to produce inspiratory resistive breathing (IRB) of 40% or 50% P_i/P_i,max (40% and 50% IRB), expiratory resistive breathing (ERB) of 60% P_e/P_e,max (60% ERB) or combined resistive breathing (CRB) of both 40% P_i/P_i,max and 60% P_e/P_e,max (40%/60% CRB). Tiotropium aerosol was inhaled prior to RB. After 6 h of RB, mechanical parameters of the respiratory system were measured and bronchoalveolar lavage (BAL) was performed. IL-1β and IL-6 protein levels were measured in lung tissue. Lung injury was estimated histologically.

Results

In all, 40% and 50% IRB increased macrophage and neutrophil counts in BAL and raised IL-1β and IL-6 lung levels, tissue elasticity, BAL total protein levels and lung injury score. Tiotropium attenuated BAL neutrophil number, IL-1β, IL-6 levels and lung injury score increase at both 40% and 50% IRB. The increase in macrophage count and protein in BAL was only reversed at 40% IRB, while tissue elasticity was not affected. In all, 60% ERB raised BAL neutrophil count and total protein and reduced macrophage count. IL-1β and IL-6 levels and lung injury score were increased. Tiotropium attenuated these alterations, except for the decrease in macrophage count and the increase in total protein level. In all, 40%/60% CRB increased macrophage and neutrophil count in BAL, IL-1β and IL-6 levels, tissue elasticity, total protein in BAL and histological injury score. Tiotropium attenuated the aforementioned alterations.

Conclusion

Tiotropium inhalation attenuates RB-induced pulmonary inflammation.

Functional and biochemical rationales for the 24-hour-long duration of action of olodaterol

β(2)-Adrenoceptor (β(2)-AR) agonists are powerful bronchodilators and play a pivotal role in the management of pulmonary obstructive diseases, such as asthma and chronic obstructive pulmonary disease. Although these agents first were used many years ago, progress in drug development has resulted in better tolerated, long-acting β(2)-AR agonists (LABAs), such as formoterol and salmeterol. Although LABAs have been on the market for several years, relatively little is known on the rationale(s) behind their long duration of action. In this study, we focused on olodaterol (previously known as BI1744CL), a novel inhaled LABA, which provides a bronchodilating effect lasting 24 h and is currently in Phase III clinical trials. To understand the rationale behind its long duration of action, different aspects of olodaterol were analyzed (i.e., its lipophilicity and propensity to accumulate in the lipid bilayer as well as its tight binding to the β(2)-AR). In line with its physicochemical properties, olodaterol associated moderately with lipid bilayers. Instead, kinetic as well as equilibrium binding studies indicated the presence of a stable [(3)H]olodaterol/β(2)-AR complex with a dissociation half-life of 17.8 h due to ternary complex formation. The tight binding of olodaterol to the human β(2)-AR and stabilization of the ternary complex were confirmed in functional experiments monitoring adenylyl cyclase activity after extensive washout. Taken together, binding, kinetic, and functional data support the existence of a stable complex with the β(2)-AR that, with a dissociation half-life >17 h, might indeed be a rationale for the 24-h duration of action of olodaterol.

Long-term follow-up of the randomised controlled trial to evaluate the safety and efficacy of the zotarolimus-eluting driver coronary stent in de novo native coronary artery lesions: five year outcomes in the ENDEAVOR II study

AIMS

We report here the final 5-year follow-up results from the ENDEAVOR II trial, which was the first randomised trial evaluating the Endeavor(tm) zotarolimus-eluting stent (ZES) compared with a bare metal stent (BMS) in patients with single, de novo coronary artery lesions.

METHODS AND RESULTS

Eligible patients were randomised 1:1 to receive ZES or BMS and were followed by telephone or clinic visit up to five years. We evaluated TVF and its components (target vessel revascularisation [TVR], Q-wave or non Q-wave myocardial infarction, or cardiac death attributed to the target vessel) at five years. Additionally, we report rates of MACE, TLR, and stent thrombosis (protocol- and ARC-defined) through five years. ENDEAVOR II enrolled 1,197 patients (598 ZES, 599 BMS). At five years of follow-up, the rates of TVF (15.4% vs 24.4%), TVR (10.7% vs 20.1%), MACE (15.4% vs 24.6%), and TLR (7.5% vs 16.3%) remained significantly lower in ZES patients compared with BMS patients. ARC definite and probable very late (>1 year) stent thrombosis remained low (0.2% ZES and 0.3% BMS) through five years.

CONCLUSIONS

After five years of follow-up, ZES demonstrated significantly improved clinical outcomes with sustained safety compared with BMS in patients with obstructive coronary artery disease.

The dynamic nature of coronary artery lesion morphology assessed by serial virtual histology intravascular ultrasound tissue characterization

OBJECTIVES

We used virtual histology intravascular ultrasound (VH-IVUS) to investigate the natural history of coronary artery lesion morphology.

BACKGROUND

Plaque stability is related to its histological composition.

METHODS

We performed serial (baseline and 12-month follow-up) VH-IVUS studies and examined 216 nonculprit lesions (plaque burden >or=40%) in 99 patients. Lesions were classified into pathological intimal thickening (PIT), VH-IVUS-derived thin-capped fibroatheroma (VH-TCFA), thick-capped fibroatheroma (ThCFA), fibrotic plaque, and fibrocalcific plaque.

RESULTS

At baseline, 20 lesions were VH-TCFAs; during follow-up, 15 (75%) VH-TCFAs "healed," 13 became ThCFAs, 2 became fibrotic plaque, and 5 (25%) VH-TCFAs remained unchanged. Compared with VH-TCFAs that healed, VH-TCFAs that remained VH-TCFAs located more proximally (values are median [interquartile range]) (16 mm [15 to 18 mm] vs. 31 mm [22 to 47 mm], p = 0.013) and had larger lumen (9.1 mm(2) [8.2 to 10.7 mm(2)] vs. 6.9 mm(2) [6.0 to 8.2 mm(2)], p = 0.021), vessel (18.7 mm(2) [17.3 to 28.6 mm(2)] vs. 15.5 mm(2) [13.3 to 16.6 mm(2)]; p = 0.010), and plaque (9.7 mm(2) [9.6 to 15.7 mm(2)] vs. 8.4 mm(2) [7 to 9.7 mm(2)], p = 0.027) areas; however, baseline VH-IVUS plaque composition did not differ between VH-TCFAs that healed and VH-TCFAs that remained VH-TCFAs. Conversely, 12 new VH-TCFAs developed; 6 late-developing VH-TCFAs were PITs, and 6 were ThCFAs at baseline. In addition, plaque area at minimum lumen sites increased significantly in PITs (7.8 mm(2) [6.2 to 10.0 mm(2)] to 9.0 mm(2) [6.5 to 12.0 mm(2)], p < 0.001), VH-TCFAs (8.6 mm(2) [7.3 to 9.9 mm(2)] to 9.5 mm(2) [7.8 to 10.8 mm(2)], p = 0.024), and ThCFAs (8.6 mm(2) [6.8 to 10.2 mm(2)] to 8.8 mm(2) [7.1 to 11.4 mm(2)], p < 0.001) with a corresponding decrease lumen areas, but not in fibrous or fibrocalcific plaque.

CONCLUSIONS

Most VH-TCFAs healed during 12-month follow-up, whereas new VH-TCFAs also developed. PITs, VH-TCFAs, and ThCFAs showed significant plaque progression compared with fibrous and fibrocalcific plaque.

Clinical efficacy and safety of enoxaparin in unselected Swiss patients undergoing primary or elective percutaneous coronary intervention: analysis of the RIVIERA study

BACKGROUND

Appropriate antithrombotic therapy during percutaneous coronary intervention (PCI) reduces major cardiovascular events and bleeding complications. The objective of the present analysis of the multinational, prospective, observational Registry on IntraVenous anticoagulation In the Elective and primary Real world of Angioplasty (RIVIERA) was to prospectively evaluate in-hospital death, myocardial infarction (MI), major and minor bleeding, and angiographic complications of enoxaparin-guided primary or elective PCI.

METHODS

In Switzerland, 255 consecutive patients from the Herz-Neuro-Zentrum Bodensee Kreuzlingen were enrolled in the RIVIERA study. The mean age of the patients was 64 years and 77% were men; 18% had primary PCI for acute ST-segment elevation myocardial infarction.The mean dose of intravenous enoxaparin was 1 mg/kg.

RESULTS

The in-hospital mortality rate was 1.2%; MI occurred in 5.5% patients, and major and minor bleeding 0.8% and 2.7%, respectively.Angiographic complications occurred in 8.6% of patients, mainly coronary dissection (3.9%) and thrombus at the treated lesion site (1.6%).

CONCLUSIONS

In a real-world setting, the clinical efficacy and safety of intravenous enoxaparin during acute and elective PCI in a Swiss heart centre is comparable with the results of randomized controlled trials.

A randomized placebo-controlled study on the effect of nifedipine on coronary endothelial function and plaque formation in patients with coronary artery disease: the ENCORE II study

AIMS

Endothelial dysfunction and plaque formation are features of atherosclerosis. Inhibition of L-type calcium channels or HMG-CoA pathway improves endothelial function and reduces plaque size. Thus, we investigated in stable coronary artery disease (CAD) the effects of a calcium antagonist on coronary endothelial function and plaque size.

METHODS AND RESULTS

In 454 patients undergoing PCI, acetylcholine (10(-6) to 10(-4) M) was infused in a coronary segment without significant CAD. Changes in coronary diameter were measured and an intravascular ultrasound examination (IVUS) was performed. On top of statin therapy, patients were randomized in a double-blind fashion to placebo or nifedipine GITS 30-60 mg/day and followed for 18-24 months. Blood pressure was lower on nifedipine than on placebo by 5.8/2.1 mmHg (P < 0.001) as was total and LDL cholesterol (4.8 mg/dL; P = 0.495), while HDL was higher (3.6 mg/dL; P = 0.026). In the most constricting segment, nifedipine reduced vasoconstriction to acetylcholine (14.0% vs. placebo 7.7%; P < 0.0088). The percentage change in plaque volume with nifedipine and placebo, respectively, was 1.0 and 1.9%, ns.

CONCLUSION

The ENCORE II trial demonstrates in a multi-centre setting that calcium channel blockade with nifedipine for up to 2 years improves coronary endothelial function on top of statin treatment, but did not show an effect of nifedipine on plaque volume.

[Performance-related middle management in medical teaching. Attractiveness of incentive tools from the perspective of the teachers]

BACKGROUND AND OBJECTIVE

German medical schools are increasingly challenged by the competition for public funds and talented students. Therefore. many curriculum planners, deans and school administrators plan to implement a systematic and comprehensive awarding system for good teaching. The OBJECTIVE of this study was to elaborate which specific incentives would be most effective to increase the motivation and enthusiasm for teaching among basic scientists as well as residents and attendings involved in medical education. In addition, a cost-effective model should be developed, which could be used as an adjustable blue-print for an awarding system.

METHODS

Based on literature search, existing approaches to rewards and incentives for medical teachers were analysed by an interdisciplinary committee in coordination with the members' department heads. According to german teaching methods and available resources, a catalogue of specific incentives has been designed and ranked by a representative sample of 200 medical teachers / faculty at two universities. Thus, a variety of favourite rewarding instruments could be elaborated, which were preferred by teachers in theoretical versus clinical disciplines.

RESULTS

The majority of the medical teachers prefer heterogeneously monetary incentives and additional protected time, followed by career-effective incentives (tenure & promotion). The discussion reflects on a transferable catalogue of different rewarding instruments, including a cost-/benefit-analysis and prerequisite students' evaluation data.

CONCLUSION

A single alteration of departmental teaching budgets does not seem to be sufficient. It seems rather advisable, also to strive for a variety of different incentives on a level that predominantly affects individual teaching personnel. Even with comparatively small amounts of money, significant effects on teachers' motivation can be achieved.

Comparison of the chondrosarcoma cell line SW1353 with primary human adult articular chondrocytes with regard to their gene expression profile and reactivity to IL-1beta

OBJECTIVE

In this study, the human chondrosarcoma cell line SW1353 was investigated by gene expression analysis in order to validate it as an in vitro model for primary human (adult articular) chondrocytes (PHCs).

METHODS

PHCs and SW1353 cells were cultured as high density monolayer cultures with and without 1ng/ml interleukin-1beta (IL-1beta). RNA was isolated and assayed using a custom-made oligonucleotide microarray representing 312 chondrocyte-relevant genes. The expression levels of selected genes were confirmed by real-time polymerase chain reaction and the gene expression profiles of the two cell types, both with and without IL-1beta treatment, were compared.

RESULTS

Overall, gene expression profiling showed only very limited similarities between SW1353 cells and PHCs at the transcriptional level. Similarities were predominantly seen with respect to catabolic effects after IL-1beta treatment. In both cell systems matrix metalloproteinase-1 (MMP-1), MMP-3 and MMP-13 were strongly induced by IL-1beta, without significant induction of MMP-2. IL-6 was also found to be up-regulated by IL-1beta in both cellular models. On the other hand, intercellular mediators such as leukemia inhibitory factor (LIF) and bone morphogenetic protein-2 (BMP-2) were not induced by IL-1beta in SW1353 cells, but significantly up-regulated in PHCs. Bioinformatical analysis identified nuclear factor kappa-B (NFkappaB) as a common transcriptional regulator of IL-1beta induced genes in both SW1353 cells and PHCs, whereas other transcription factors were only found to be relevant for individual cell systems.

CONCLUSION

Our data characterize SW1353 cells as a cell line with only a very limited potential to mimic PHCs, though SW1353 cells can be of value to study the induction of protease expression within cells, a phenomenon also seen in chondrocytes.

Direct stenting with the Bx VELOCITY balloon-expandable stent mounted on the Raptor rapid exchange delivery system versus predilatation in a European randomized Trial: the VELVET trial

AIMS

This study examined the six-month angiographic results of direct coronary stenting, and compared the nine-month safety, efficacy and cost of this strategy versus stenting after balloon predilatation.

METHODS

In phase I of VELVET, 122 patients (mean age = 62.3 +/- 10.1 years, 77% male, 11% with diabetes) with angina pectoris or myocardial ischemia resulting from a single de novo 51% to 95% coronary stenosis underwent direct stenting. The endpoints of phase I included angiographic findings and rates of major adverse cardiac events up to six months of follow-up. In phase II, 401 patients (mean age = 61.3 +/- 10.8 years, 79% male, 16% with diabetes) with angina pectoris or documented myocardial ischemia resulting from single or multiple, de novo or restenotic, coronary lesions were randomized between direct stenting and stenting after predilatation. The immediate angiographic results, and clinical outcomes and costs associated with the two treatment strategies up to nine months of follow-up were compared.

RESULTS

In phase I the mean diameter stenosis immediately before and after the procedure, and at six months was 61.7+/-9.4%, 13.5+/-6.3%, and 33.6+/-16.2%, respectively. The six-month binary restenosis rate was 11%. The overall rate of major adverse cardiac events, including two non-cardiac deaths, was 9.8%. In phase II, the success rates of the intended delivery strategies were 87.9% and 97.9% for direct stenting and predilatation, respectively (p < 0.001), while the procedural success rates were similar (93.9% vs 96.5%). Over a follow-up period of nine months, major adverse cardiac events rates were 12.0% and 10.9% in patients randomized to direct stenting and predilatation, respectively (non-significant). Analyses of the costs incurred up to nine months in each treatment group revealed a mean saving of e362 per patient in favor of the direct stenting strategy (non-significant).

CONCLUSIONS

Compared with a strategy of stenting preceded by balloon dilatation, direct stenting was associated with an equivalent procedural success rate, equivalent clinical results up to nine months of follow-up, and a reduction in procedural and in-hospital costs (p < 0.0001 and p < 0.001, respectively), that was no longer significant after nine months.

Modulation of the catalytic activity of neutrophil collagenase MMP-8 on bovine collagen I. Role of the activation cleavage and of the hemopexin-like domain

The cleavage of bovine collagen I by neutrophil collagenase MMP-8 has been followed at pH 7.4, 37 degrees C. The behavior of the whole enzyme molecule (whMMP-8), displaying both the catalytic domain and the hemopexin-like domain, has been compared under the same experimental conditions with that of the catalytic domain only. The main observation is that whMMP-8 cleaves bovine collagen I only at a single specific site, as already reported by many others (Mallya, S. K., Mookhtiar, K. A., Gao, Y., Brew, K., Dioszegi, M., Birkedal-Hansen, H., and van Wart, H. E. (1990) Biochemistry 29, 10628-10634; Knäuper, V., Osthues, A., DeClerk, Y. A., Langley, K. A., Bläser, J., and Tschesche, H. (1993) Biochem. J. 291, 847-854; Marini, S., Fasciglione, G. F., De Sanctis, G., D'Alessio, S., Politi, V., and Coletta, M. (2000) J. Biol. Chem. 275, 18657-18663), whereas the catalytic domain lacks this specificity and cleaves the collagen molecule at multiple sites. Furthermore, a meaningful difference is observed for the cleavage features displayed by two forms of the catalytic domain, which differ for the N terminus resulting from the activation process (i.e. the former Met(80) of the proenzyme (MetMMP-8) and the former Phe(79) of the proenzyme (PheMMP-8)). Thus, the PheMMP-8 species is characterized by a much faster k(cat)/K(m), fully attributable to a lower K(m), suggesting that the conformation of the catalytic domain, induced by the insertion of this N-terminal residue in a specific pocket (Reinemer, P., Grams, F., Huber, R., Kleine, T., Schnierer, S., Piper, M., Tschesche, H., and Bode, W. (1994) FEBS Lett. 338, 227-233), brings about a better, although less discriminatory, recognition process of cleavage site(s) on bovine collagen I.