The microtubule signature in cardiac disease: etiology, disease stage, and age dependency.

Employing animal models to study heart failure (HF) has become indispensable to discover and test novel therapies, but their translatability remains challenging. Although cytoskeletal alterations are linked to HF, the tubulin signature of common experimental models has been incompletely defined. Here, we assessed the tubulin signature in a large set of human cardiac samples and myocardium of animal models with cardiac remodeling caused by pressure overload, myocardial infarction or a gene defect. We studied levels of total, acetylated, and detyrosinated α-tubulin and desmin in cardiac tissue from hypertrophic (HCM) and dilated cardiomyopathy (DCM) patients with an idiopathic (n = 7), ischemic (n = 7) or genetic origin (n = 59), and in a pressure-overload concentric hypertrophic pig model (n = 32), pigs with a myocardial infarction (n = 28), mature pigs (n = 6), and mice (n = 15) carrying the HCM-associated MYBPC32373insG mutation. In the human samples, detyrosinated α-tubulin was increased 4-fold in end-stage HCM and 14-fold in pediatric DCM patients. Acetylated α-tubulin was increased twofold in ischemic patients. Across different animal models, the tubulin signature remained mostly unaltered. Only mature pigs were characterized by a 0.5-fold decrease in levels of total, acetylated, and detyrosinated α-tubulin. Moreover, we showed increased desmin levels in biopsies from NYHA class II HCM patients (2.5-fold) and the pressure-overload pig model (0.2-0.3-fold). Together, our data suggest that desmin levels increase early on in concentric hypertrophy and that animal models only partially recapitulate the proliferated and modified tubulin signature observed clinically. Our data warrant careful consideration when studying maladaptive responses to changes in the tubulin content in animal models.

Integrated control of coronary blood flow in exercising swine by adenosine, nitric oxide, and KATP channels.

The interplay of mechanisms regulating coronary blood flow (CBF) remains incompletely understood. Previous studies in dogs indicated that CBF regulation by KATP channels, adenosine, and nitric oxide (NO) follows a nonlinear redundancy design and fully accounted for exercise-induced coronary vasodilation. Conversely, in swine, these mechanisms appear to regulate CBF in a linear additive fashion with considerable exercise-induced vasodilation remaining when all three mechanisms are inhibited. A direct comparison between these studies is hampered by the different doses and administration routes (intravenous vs. intracoronary) of drugs inhibiting these mechanisms. Here, we investigated the role of KATP channels, adenosine, and NO in CBF regulation in swine using identical drug regimen as previously employed in dogs. Instrumented swine were exercised on a motor-driven treadmill, before and after blockade of KATP channels (glibenclamide, 50 µg/kg/min ic) and combination of inhibition of NO synthase (Nω-nitro-l-arginine, NLA, 1.5 mg/kg ic) and adenosine receptors (8-phenyltheophylline, 8PT, 5 mg/kg iv) or their combination NLA + 8PT + glibenclamide. Glibenclamide and NLA + 8PT each produced coronary vasoconstriction both at rest and during exercise, whereas the combination of NLA + 8PT + glibenclamide resulted in a small further coronary vasoconstriction compared with NLA + 8PT that was, however, less than the sum of the vasoconstriction produced by NLA + 8PT and glibenclamide, each. Thus, in contrast to previous observations in the dog, 1) the coronary vasoconstrictor effect of glibenclamide was not enhanced in the presence of NLA + 8PT and 2) the exercise-induced increase in CBF was largely maintained. These findings show profound species differences in the mechanisms controlling CBF at rest and during exercise.NEW & NOTEWORTHY The present study demonstrates important species differences in the regulation of coronary blood flow by adenosine, NO, and KATP channels at rest and during exercise. In swine, these mechanisms follow a linear additive design, as opposed to dogs which follow a nonlinear redundant design. Simultaneous blockade of all three mechanisms virtually abolished exercise-induced coronary vasodilation in dogs, whereas a substantial vasodilator reserve could still be recruited during exercise in swine.

Impaired pulmonary vasomotor control in exercising swine with multiple comorbidities.

Pulmonary hypertension is common in heart failure with preserved ejection fraction (HFpEF). Here, we tested the hypothesis that comorbidities [diabetes mellitus (DM, streptozotocin), hypercholesterolemia (HC, high-fat diet) and chronic kidney disease (CKD, renal microembolization)] directly impair pulmonary vasomotor control in a DM + HC + CKD swine model. 6 months after induction of DM + HC + CKD, pulmonary arterial pressure was similar in chronically instrumented female DM + HC + CKD (n = 19) and Healthy swine (n = 18). However, cardiac output was lower both at rest and during exercise, implying an elevated pulmonary vascular resistance (PVR) in DM + HC + CKD swine (153 ± 10 vs. 122 ± 9 mmHg∙L-1∙min∙kg). Phosphodiesterase 5 inhibition and endothelin receptor antagonism decreased PVR in DM + HC + CKD (- 12 ± 12 and - 22 ± 7 mmHg∙L-1∙min∙kg) but not in Healthy swine (- 1 ± 12 and 2 ± 14 mmHg∙L-1∙min∙kg), indicating increased vasoconstrictor influences of phosphodiesterase 5 and endothelin. Inhibition of nitric oxide synthase produced pulmonary vasoconstriction that was similar in Healthy and DM + HC + CKD swine, but unmasked a pulmonary vasodilator effect of endothelin receptor antagonism in Healthy (- 56 ± 26 mmHg∙L-1∙min∙kg), whereas it failed to significantly decrease PVR in DM + HC + CKD, indicating loss of nitric oxide mediated inhibition of endothelin in DM + HC + CKD. Scavenging of reactive oxygen species (ROS) had no effect on PVR in either Healthy or DM + HC + CKD swine. Cardiovascular magnetic resonance imaging, under anesthesia, showed no right ventricular changes. Finally, despite an increased contribution of endogenous nitric oxide to vasomotor tone regulation in the systemic vasculature, systemic vascular resistance at rest was higher in DM + HC + CKD compared to Healthy swine (824 ± 41 vs. 698 ± 35 mmHg∙L-1∙min∙kg). ROS scavenging induced systemic vasodilation in DM + HC + CKD, but not Healthy swine. In conclusion, common comorbidities directly alter pulmonary vascular control, by enhanced PDE5 and endothelin-mediated vasoconstrictor influences, well before overt left ventricular backward failure or pulmonary hypertension develop.

Reduced nitric oxide bioavailability impairs myocardial oxygen balance during exercise in swine with multiple risk factors.

In the present study, we tested the hypothesis that multiple risk factors, including diabetes mellitus (DM), dyslipidaemia and chronic kidney disease (CKD) result in a loss of nitric oxide (NO) signalling, thereby contributing to coronary microvascular dysfunction. Risk factors were induced in 12 female swine by intravenous streptozotocin injections (DM), a high fat diet (HFD) and renal artery embolization (CKD). Female healthy swine (n = 13) on normal diet served as controls (Normal). After 5 months, swine were chronically instrumented and studied at rest and during exercise. DM + HFD + CKD swine demonstrated significant hyperglycaemia, dyslipidaemia and impaired kidney function compared to Normal swine. These risk factors were accompanied by coronary microvascular endothelial dysfunction both in vivo and in isolated small arteries, due to a reduced NO bioavailability, associated with perturbations in myocardial oxygen balance at rest and during exercise. NO synthase inhibition caused coronary microvascular constriction in exercising Normal swine, but had no effect in DM + HFD + CKD animals, while inhibition of phosphodiesterase 5 produced similar vasodilator responses in both groups, indicating that loss of NO bioavailability was principally responsible for the observed coronary microvascular dysfunction. This was associated with an increase in myocardial 8-isoprostane levels and a decrease in antioxidant capacity, while antioxidants restored the vasodilation to bradykinin in isolated coronary small arteries, suggesting that oxidative stress was principally responsible for the reduced NO bioavailability. In conclusion, five months of combined exposure to DM + HFD + CKD produces coronary endothelial dysfunction due to impaired NO bioavailability, resulting in impaired myocardial perfusion at rest and during exercise.

Endothelial Dysfunction, Atherosclerosis, and Increase of von Willebrand Factor and Factor VIII: A Randomized Controlled Trial in Swine.

It is well known that high von Willebrand factor (VWF) and factor VIII (FVIII) levels are associated with an increased risk of cardiovascular disease. It is still debated whether VWF and FVIII are biomarkers of endothelial dysfunction and atherosclerosis or whether they have a direct causative role. Therefore, we aimed to unravel the pathophysiological pathways of increased VWF and FVIII levels associated with cardiovascular risk factors. First, we performed a randomized controlled trial in 34 Göttingen miniswine. Diabetes mellitus (DM) was induced with streptozotocin and hypercholesterolemia (HC) via a high-fat diet in 18 swine (DM + HC), while 16 healthy swine served as controls. After 5 months of follow-up, FVIII activity (FVIII:C) was significantly higher in DM + HC swine (5.85 IU/mL [5.00-6.81]) compared with controls (4.57 [3.76-5.40], p = 0.010), whereas VWF antigen (VWF:Ag) was similar (respectively 0.34 IU/mL [0.28-0.39] vs. 0.34 [0.31-0.38], p = 0.644). DM + HC swine had no endothelial dysfunction or atherosclerosis during this short-term follow-up. Subsequently, we performed a long-term (15 months) longitudinal cohort study in 10 Landrace-Yorkshire swine, in five of which HC and in five combined DM + HC were induced. VWF:Ag was higher at 15 months compared with 9 months in HC (0.37 [0.32-0.42] vs. 0.27 [0.23-0.40], p = 0.042) and DM + HC (0.33 [0.32-0.37] vs. 0.25 [0.24-0.33], p = 0.042). Both long-term groups had endothelial dysfunction compared with controls and atherosclerosis after 15 months. In conclusion, short-term hyperglycemia and dyslipidemia increase FVIII, independent of VWF. Long-term DM and HC increase VWF via endothelial dysfunction and atherosclerosis. Therefore, VWF seems to be a biomarker for advanced cardiovascular disease.

Mechanobiology of Microvascular Function and Structure in Health and Disease: Focus on the Coronary Circulation.

The coronary microvasculature plays a key role in regulating the tight coupling between myocardial perfusion and myocardial oxygen demand across a wide range of cardiac activity. Short-term regulation of coronary blood flow in response to metabolic stimuli is achieved via adjustment of vascular diameter in different segments of the microvasculature in conjunction with mechanical forces eliciting myogenic and flow-mediated vasodilation. In contrast, chronic adjustments in flow regulation also involve microvascular structural modifications, termed remodeling. Vascular remodeling encompasses changes in microvascular diameter and/or density being largely modulated by mechanical forces acting on the endothelium and vascular smooth muscle cells. Whereas in recent years, substantial knowledge has been gathered regarding the molecular mechanisms controlling microvascular tone and how these are altered in various diseases, the structural adaptations in response to pathologic situations are less well understood. In this article, we review the factors involved in coronary microvascular functional and structural alterations in obstructive and non-obstructive coronary artery disease and the molecular mechanisms involved therein with a focus on mechanobiology. Cardiovascular risk factors including metabolic dysregulation, hypercholesterolemia, hypertension and aging have been shown to induce microvascular (endothelial) dysfunction and vascular remodeling. Additionally, alterations in biomechanical forces produced by a coronary artery stenosis are associated with microvascular functional and structural alterations. Future studies should be directed at further unraveling the mechanisms underlying the coronary microvascular functional and structural alterations in disease; a deeper understanding of these mechanisms is critical for the identification of potential new targets for the treatment of ischemic heart disease.

A direct comparison of natural and acoustic-radiation-force-induced cardiac mechanical waves.

Natural and active shear wave elastography (SWE) are potential ultrasound-based techniques to non-invasively assess myocardial stiffness, which could improve current diagnosis of heart failure. This study aims to bridge the knowledge gap between both techniques and discuss their respective impacts on cardiac stiffness evaluation. We recorded the mechanical waves occurring after aortic and mitral valve closure (AVC, MVC) and those induced by acoustic radiation force throughout the cardiac cycle in four pigs after sternotomy. Natural SWE showed a higher feasibility than active SWE, which is an advantage for clinical application. Median propagation speeds of 2.5-4.0 m/s and 1.6-4.0 m/s were obtained after AVC and MVC, whereas ARF-based median speeds of 0.9-1.2 m/s and 2.1-3.8 m/s were reported for diastole and systole, respectively. The different wave characteristics in both methods, such as the frequency content, complicate the direct comparison of waves. Nevertheless, a good match was found in propagation speeds between natural and active SWE at the moment of valve closure, and the natural waves showed higher propagation speeds than in diastole. Furthermore, the results demonstrated that the natural waves occur in between diastole and systole identified with active SWE, and thus represent a myocardial stiffness in between relaxation and contraction.

Cellular, mitochondrial and molecular alterations associate with early left ventricular diastolic dysfunction in a porcine model of diabetic metabolic derangement.

The prevalence of diabetic metabolic derangement (DMetD) has increased dramatically over the last decades. Although there is increasing evidence that DMetD is associated with cardiac dysfunction, the early DMetD-induced myocardial alterations remain incompletely understood. Here, we studied early DMetD-related cardiac changes in a clinically relevant large animal model. DMetD was established in adult male Göttingen miniswine by streptozotocin injections and a high-fat, high-sugar diet, while control animals remained on normal pig chow. Five months later left ventricular (LV) function was assessed by echocardiography and hemodynamic measurements, followed by comprehensive biochemical, molecular and histological analyses. Robust DMetD developed, evidenced by hyperglycemia, hypercholesterolemia and hypertriglyceridemia. DMetD resulted in altered LV nitroso-redox balance, increased superoxide production-principally due to endothelial nitric oxide synthase (eNOS) uncoupling-reduced nitric oxide (NO) production, alterations in myocardial gene-expression-particularly genes related to glucose and fatty acid metabolism-and mitochondrial dysfunction. These abnormalities were accompanied by increased passive force of isolated cardiomyocytes, and impaired LV diastolic function, evidenced by reduced LV peak untwist velocity and increased E/e'. However, LV weight, volume, collagen content, and cardiomyocyte cross-sectional area were unchanged at this stage of DMetD. In conclusion, DMetD, in a clinically relevant large-animal model results in myocardial oxidative stress, eNOS uncoupling and reduced NO production, together with an altered metabolic gene expression profile and mitochondrial dysfunction. These molecular alterations are associated with stiffening of the cardiomyocytes and early diastolic dysfunction before any structural cardiac remodeling occurs. Therapies should be directed to ameliorate these early DMetD-induced myocardial changes to prevent the development of overt cardiac failure.

Perturbations in myocardial perfusion and oxygen balance in swine with multiple risk factors: a novel model of ischemia and no obstructive coronary artery disease.

Comorbidities of ischemic heart disease, including diabetes mellitus (DM), hypercholesterolemia (HC) and chronic kidney disease (CKD), are associated with coronary microvascular dysfunction (CMD). Increasing evidence suggests that CMD may contribute to myocardial 'Ischemia and No Obstructive Coronary Artery disease' (INOCA). In the present study, we tested the hypothesis that CMD results in perturbations in myocardial perfusion and oxygen delivery using a novel swine model with multiple comorbidities. DM (streptozotocin), HC (high-fat diet) and CKD (renal embolization) were induced in 10 female swine (DM + HC + CKD), while 12 healthy female swine on a normal diet served as controls (Normal). After 5 months, at a time when coronary atherosclerosis was still negligible, myocardial perfusion, metabolism, and function were studied at rest and during treadmill exercise. DM + HC + CKD animals showed hyperglycemia, hypercholesterolemia, and impaired kidney function. During exercise, DM + HC + CKD swine demonstrated perturbations in myocardial blood flow and oxygen delivery, necessitating a higher myocardial oxygen extraction-achieved despite reduced capillary density-resulting in lower coronary venous oxygen levels. Moreover, myocardial efficiency was lower, requiring higher oxygen consumption for a given level of myocardial work. These perturbations in myocardial oxygen balance were associated with lower myocardial lactate consumption, stroke volume, and LVdP/dtmax, suggestive of myocardial ischemia and dysfunction. Further analyses showed a reduction in adenosine-recruitable coronary flow reserve, but this was exclusively the result of an increase in basal coronary blood flow, while maximal coronary flow per gram of myocardium was maintained; the latter was consistent with the unchanged arteriolar wall/lumen ratio, arteriolar density and peri-arteriolar collagen content. However, isolated small arteries displayed selective blunting of endothelium-dependent vasodilation in response to bradykinin in DM + HC + CKD swine, suggesting that changes in coronary microvascular function rather than in structure contributed to the perturbations in myocardial oxygen delivery. In conclusion, common comorbidities in swine result in CMD, in the absence of appreciable atherosclerosis, which is severe enough to produce perturbations in myocardial oxygen balance, particularly during exercise, resembling key features of INOCA.

Experimental animal models of coronary microvascular dysfunction.

Coronary microvascular dysfunction (CMD) is commonly present in patients with metabolic derangements and is increasingly recognized as an important contributor to myocardial ischaemia, both in the presence and absence of epicardial coronary atherosclerosis. The latter condition is termed 'ischaemia and no obstructive coronary artery disease' (INOCA). Notwithstanding the high prevalence of INOCA, effective treatment remains elusive. Although to date there is no animal model for INOCA, animal models of CMD, one of the hallmarks of INOCA, offer excellent test models for enhancing our understanding of the pathophysiology of CMD and for investigating novel therapies. This article presents an overview of currently available experimental models of CMD-with an emphasis on metabolic derangements as risk factors-in dogs, swine, rabbits, rats, and mice. In all available animal models, metabolic derangements are most often induced by a high-fat diet (HFD) and/or diabetes mellitus via injection of alloxan or streptozotocin, but there is also a wide variety of spontaneous as well as transgenic animal models which develop metabolic derangements. Depending on the number, severity, and duration of exposure to risk factors-all these animal models show perturbations in coronary microvascular (endothelial) function and structure, similar to what has been observed in patients with INOCA and comorbid conditions. The use of these animal models will be instrumental in identifying novel therapeutic targets and for the subsequent development and testing of novel therapeutic interventions to combat ischaemic heart disease, the number one cause of death worldwide.

Chronic Kidney Disease as a Risk Factor for Heart Failure With Preserved Ejection Fraction: A Focus on Microcirculatory Factors and Therapeutic Targets.

Heart failure (HF) and chronic kidney disease (CKD) co-exist, and it is estimated that about 50% of HF patients suffer from CKD. Although studies have been performed on the association between CKD and HF with reduced ejection fraction (HFrEF), less is known about the link between CKD and heart failure with preserved ejection fraction (HFpEF). Approximately, 50% of all patients with HF suffer from HFpEF, and this percentage is projected to rise in the coming years. Therapies for HFrEF are long established and considered quite successful. In contrast, clinical trials for treatment of HFpEF have all shown negative or disputable results. This is likely due to the multifactorial character and the lack of pathophysiological knowledge of HFpEF. The typical co-existence of HFpEF and CKD is partially due to common underlying comorbidities, such as hypertension, dyslipidemia and diabetes. Macrovascular changes accompanying CKD, such as hypertension and arterial stiffening, have been described to contribute to HFpEF development. Furthermore, several renal factors have a direct impact on the heart and/or coronary microvasculature and may underlie the association between CKD and HFpEF. These factors include: (1) activation of the renin-angiotensin-aldosterone system, (2) anemia, (3) hypercalcemia, hyperphosphatemia and increased levels of FGF-23, and (4) uremic toxins. This review critically discusses the above factors, focusing on their potential contribution to coronary dysfunction, left ventricular stiffening, and delayed left ventricular relaxation. We further summarize the directions of novel treatment options for HFpEF based on the contribution of these renal drivers.

Pulmonary microvascular remodeling in chronic thrombo-embolic pulmonary hypertension.

Pulmonary vascular remodeling in pulmonary arterial hypertension involves perturbations in the nitric oxide (NO) and endothelin-1 (ET-1) pathways. However, the implications of pulmonary vascular remodeling and these pathways remain unclear in chronic thrombo-embolic pulmonary hypertension (CTEPH). The objective of the present study was to characterize changes in microvascular morphology and function, focussing on the ET-1 and NO pathways, in a CTEPH swine model. Swine were chronically instrumented and received up to five pulmonary embolizations by microsphere infusion, whereas endothelial dysfunction was induced by daily administration of the endothelial NO synthase inhibitor Nω-nitro-l-arginine methyl ester until 2 wk before the end of study. Swine were subjected to exercise, and the pulmonary vasculature was investigated by hemodynamic, histological, quantitative PCR, and myograph experiments. In swine with CTEPH, the increased right-ventricular afterload, decreased cardiac index, and mild ventilation-perfusion-mismatch were exacerbated during exercise. Pulmonary microvascular remodeling was evidenced by increased muscularization, which was accompanied by an increased maximal vasoconstriction. Although ET-1-induced vasoconstriction was increased in CTEPH pulmonary small arteries, the ET-1 sensitivity was decreased. Moreover, the contribution of the ETA receptor to ET-1 vasoconstriction was increased, whereas the contribution of the ETB receptor was decreased and the contribution of Rho-kinase was lost. A reduction in endogenous NO production was compensated in part by a decreased phosphodiesterase 5 (PDE5) activity resulting in an apparent increased NO sensitivity in CTEPH pulmonary small arteries. These findings suggest that pulmonary microvascular remodeling with a reduced activity of PDE5 and Rho-kinase may contribute to the lack of therapeutic efficacy of PDE5 inhibitors and Rho-kinase inhibitors in CTEPH.

Multiple common comorbidities produce left ventricular diastolic dysfunction associated with coronary microvascular dysfunction, oxidative stress, and myocardial stiffening.

Aims: More than 50% of patients with heart failure have preserved ejection fraction characterized by diastolic dysfunction. The prevalance of diastolic dysfunction is higher in females and associates with multiple comorbidities such as hypertension (HT), obesity, hypercholesterolemia (HC), and diabetes mellitus (DM). Although its pathophysiology remains incompletely understood, it has been proposed that these comorbidities induce systemic inflammation, coronary microvascular dysfunction, and oxidative stress, leading to myocardial fibrosis, myocyte stiffening and, ultimately, diastolic dysfunction. Here, we tested this hypothesis in a swine model chronically exposed to three common comorbidities. Methods and results: DM (induced by streptozotocin), HC (produced by high fat diet), and HT (resulting from renal artery embolization), were produced in 10 female swine, which were followed for 6 months. Eight female healthy swine on normal pig-chow served as controls. The DM + HC + HT group showed hyperglycemia, HC, hypertriglyceridemia, renal dysfunction and HT, which were associated with systemic inflammation. Myocardial superoxide production was markedly increased, due to increased NOX activity and eNOS uncoupling, and associated with reduced NO production, and impaired coronary small artery endothelium-dependent vasodilation. These abnormalities were accompanied by increased myocardial collagen content, reduced capillary/fiber ratio, and elevated passive cardiomyocyte stiffness, resulting in an increased left ventricular end-diastolic stiffness (measured by pressure-volume catheter) and a trend towards a reduced E/A ratio (measured by cardiac MRI), while ejection fraction was maintained. Conclusions: The combination of three common comorbidities leads to systemic inflammation, myocardial oxidative stress, and coronary microvascular dysfunction, which associate with myocardial stiffening and LV diastolic dysfunction with preserved ejection fraction.

Cardiovascular Function of Modern Pigs Does not Comply with Allometric Scaling Laws.

Growing concerns have been expressed regarding cardiovascular performance in modern farm pigs, which has been proposed as a critical factor contributing to the reduced adaptability of modern pigs to stress. Here we tested the hypothesis that cardiac dimensions and pump function in modern heavy farm pigs are disproportionally low for their body weight, and investigated potential underlying mechanisms. The results from the present study indeed demonstrate disproportionally low values for stroke volume and cardiac output in pigs with bodyweights over 150 kg. Importantly, these low values were not the result of impaired left ventricular (LV) systolic contractile function, but were due to a disproportionally small LV end-diastolic volume. The latter was associated with changes in determinants of LV passive stiffness, including (i) an increase in LV myocardial collagen, (ii) a shift from the compliant N2BA titin isoform towards the stiff N2B, and (iii) a marked elevation of aortic blood pressure. Taken together, these results demonstrate reduced pumping capacity of the hearts of heavy modern pigs, due to structural abnormalities in the LV myocardium.

Early detection of left ventricular diastolic dysfunction using conventional and speckle tracking echocardiography in a large animal model of metabolic dysfunction.

Left ventricular (LV) diastolic dysfunction is one of the important mechanisms responsible for symptoms in patients with heart failure. The aim of the current study was to identify parameters that may be used to detect early signs of LV diastolic dysfunction in diabetic pigs on a high fat diet, using conventional and speckle tracking echocardiography. The study population consisted of 16 healthy Göttingen minipigs and 18 minipigs with experimentally induced metabolic dysfunction. Echocardiography measurements were performed at baseline and 3-month follow-up. The ratio of peak early (E) and late filling velocity (E/A ratio) and the ratio of E and the velocity of the mitral annulus early diastolic wave (E/Em ratio) did not change significantly in both groups. Peak untwisting velocity decreased in the metabolic dysfunction group (- 30.1 ± 18.5 vs. - 23.4 ± 15.5 °/ms) but not in controls (- 38.1 ± 23.6 vs. - 42.2 ± 23.0 °/ms), being significantly different between the groups at the 3-month time point (p < 0.05). In conclusion, whereas E/A ratio and E/Em ratio did not change significantly after 3 months of metabolic dysfunction, peak untwisting velocity was significantly decreased. Hence, peak untwisting velocity may serve as an important marker to detect early changes of LV diastolic dysfunction.

The effect of bioresorbable vascular scaffold implantation on distal coronary endothelial function in dyslipidemic swine with and without diabetes.

BACKGROUND: We studied the effect of bioresorbable vascular scaffold (BVS) implantation on distal coronary endothelial function, in swine on a high fat diet without (HFD) or with diabetes (DM+HFD). METHODS: Five DM+HFD and five HFD swine underwent BVS implantation on top of coronary plaques, and were studied six months later. Conduit artery segments >5mm proximal and distal to the scaffold and corresponding segments of non-scaffolded coronary arteries, and segments of small arteries within the flow-territory of scaffolded and non-scaffolded arteries were harvested for in vitro vasoreactivity studies. RESULTS: Conduit segments proximal and distal of the BVS edges showed reduced endothelium-dependent vasodilation as compared to control vessels (p≤0.01), with distal segments being most prominently affected(p≤0.01). Endothelial dysfunction was only observed in DM±HFD swine and was principally due to a loss of NO. Endothelium-independent vasodilation and vasoconstriction were unaffected. Surprisingly, segments from the microcirculation distal to the BVS showed enhanced endothelium-dependent vasodilation (p<0.01), whereas endothelium-independent vasodilation and vasoconstriction were unaltered. This enhanced vasorelaxation was only observed in DM+HFD swine, and did not appear to be either NO- or EDHF-mediated. CONCLUSIONS: Six months of BVS implantation in DM+HFD swine causes NO-mediated endothelial dysfunction in nearby coronary segments, which is accompanied by a, possibly compensatory, increase in endothelial function of the distal microcirculation. Endothelial dysfunction extending into coronary conduit segments beyond the implantation-site, is in agreement with recent reports expressing concern for late scaffold thrombosis and of early BVS failure in diabetic patients.

Neoatherosclerosis development following bioresorbable vascular scaffold implantation in diabetic and non-diabetic swine.

BACKGROUND: DM remains a risk factor for poor outcome after stent-implantation, but little is known if and how DM affects the vascular response to BVS. AIM: The aim of our study was to examine coronary responses to bioresorbable vascular scaffolds (BVS) in swine with and without diabetes mellitus fed a 'fast-food' diet (FF-DM and FF-NDM, respectively) by sequential optical coherence tomography (OCT)-imaging and histology. METHODS: Fifteen male swine were evaluated. Eight received streptozotocin-injection to induce DM. After 9 months (M), 32 single BVS were implanted in epicardial arteries with a stent to artery (S/A)-ratio of 1.1:1 under quantitative coronary angiography (QCA) and OCT guidance. Lumen, scaffold, neointimal coverage and composition were assessed by QCA, OCT and near-infrared spectroscopy (NIRS) pre- and/or post-procedure, at 3M and 6M. Additionally, polarization-sensitive (PS)-OCT was performed in 7 swine at 6M. After sacrifice at 3M and 6M, histology and polymer degradation analysis were performed. RESULTS: Late lumen loss was high (~60%) within the first 3M after BVS-implantation (P<0.01 FF-DM vs. FF-NDM) and stabilized between 3M and 6M (<5% change in FF-DM, ~10% in FF-NDM; P>0.20). Neointimal coverage was highly heterogeneous in all swine (DM vs. NDM P>0.05), with focal lipid accumulation, irregular collagen distribution and neointimal calcification. Likewise, polymer mass loss was low (~2% at 3M, ~5% at 6M;P>0.20) and not associated with DM or inflammation. CONCLUSION: Scaffold coverage showed signs of neo-atherosclerosis in all FF-DM and FF-NDM swine, scaffold polymer was preserved and the vascular response to BVS was not influenced by diabetes.

The microcirculation: a key player in obesity-associated cardiovascular disease.

It is increasingly recognized that obesity is a risk factor for microvascular disease, involving both structural and functional changes in the microvasculature. This review aims to describe how obesity impacts the microvasculature of a variety of tissues, including visceral adipose tissue, skeletal muscle, heart, brain, kidneys, and lungs. These changes involve endothelial dysfunction, which in turn (i) impacts control of vascular tone, (ii) contributes to development of microvascular insulin resistance, (iii) alters secretion of paracrine factors like nitric oxide and endothelin, but (iv) also influences vascular structure and perivascular inflammation. In concert, these changes impair organ perfusion and organ function thereby contributing to altered release and clearance of neurohumoral factors, such as adipokines and inflammatory cytokines. Global microvascular dysfunction in obese subjects is therefore a common pathway that not only explains exercise-intolerance but also predisposes to development of chronic kidney disease, microvascular dementia, coronary microvascular angina, heart failure with preserved ejection fraction, chronic obstructive pulmonary disease, and pulmonary hypertension.

Altered purinergic signaling in uridine adenosine tetraphosphate-induced coronary relaxation in swine with metabolic derangement.

We previously demonstrated that uridine adenosine tetraphosphate (Up4A) induces potent and partially endothelium-dependent relaxation in the healthy porcine coronary microvasculature. We subsequently showed that Up4A-induced porcine coronary relaxation was impaired via downregulation of P1 receptors after myocardial infarction. In view of the deleterious effect of metabolic derangement on vascular function, we hypothesized that the coronary vasodilator response to Up4A is impaired in metabolic derangement, and that the involvement of purinergic receptor subtypes and endothelium-derived vasoactive factors (EDVFs) is altered. Coronary small arteries, dissected from the apex of healthy swine and swine 6 months after induction of diabetes with streptozotocin and fed a high-fat diet, were mounted on wire myographs. Up4A (10-9-10-5 M)-induced coronary relaxation was maintained in swine with metabolic derangement compared to normal swine, despite impaired endothelium-dependent relaxation to bradykinin and despite blunted P2X7 receptor and NO-mediated vasodilator influences of Up4A. Moreover, a thromboxane-mediated vasoconstrictor influence was unmasked. In contrast, an increased Up4A-mediated vasodilator influence via P2Y1 receptors was observed, while, in response to Up4A, cytochrome P450 2C9 switched from producing vasoconstrictor to vasodilator metabolites in swine with metabolic derangement. Coronary vascular expression of A2A and P2X7 receptors as well as eNOS, as assessed with real-time PCR, was reduced in swine with metabolic derangement. In conclusion, although the overall coronary vasodilator response to Up4A was maintained in swine with metabolic derangement, the involvement of purinergic receptor subtypes and EDVF was markedly altered, revealing compensatory mechanisms among signaling pathways in Up4A-mediated coronary vasomotor influence in the early phase of metabolic derangement. Future studies are warranted to investigate the effects of severe metabolic derangement on coronary responses to Up4A.