Browsing by Author "Tune, Johnathan D."
Now showing 1 - 10 of 49
Results Per Page
Sort Options
Item Biphasic alterations in coronary smooth muscle Ca2+ regulation in a repeat cross-sectional study of coronary artery disease severity in metabolic syndrome(Elsevier, 2016-06) McKenney-Drake, Mikaela L.; Rodenbeck, Stacey D.; Owen, Meredith K.; Schultz, Kyle A.; Alloosh, Mouhamad; Tune, Johnathan D.; Sturek, Michael; Department of Cellular and Integrative Physiology, School of MedicineBACKGROUND AND AIMS: Coronary artery disease (CAD) is progressive, classified by stages of severity. Alterations in Ca(2+) regulation within coronary smooth muscle (CSM) cells in metabolic syndrome (MetS) have been observed, but there is a lack of data in relatively early (mild) and late (severe) stages of CAD. The current study examined alterations in CSM Ca(2+) regulation at several time points during CAD progression. METHODS: MetS was induced by feeding an excess calorie atherogenic diet for 6, 9, or 12 months and compared to age-matched lean controls. CAD was measured with intravascular ultrasound (IVUS). Intracellular Ca(2+) was assessed with fura-2. RESULTS: IVUS revealed that the extent of atherosclerotic CAD correlated with the duration on atherogenic diet. Fura-2 imaging of intracellular Ca(2+) in CSM cells revealed heightened Ca(2+) signaling at 9 months on diet, compared to 6 and 12 months, and to age-matched lean controls. Isolated coronary artery rings from swine fed for 9 months followed the same pattern, developing greater tension to depolarization, compared to 6 and 12 months (6 months = 1.8 ± 0.6 g, 9 months = 5.0 ± 1.0 g, 12 months = 0.7 ± 0.1 g). CSM in severe atherosclerotic plaques showed dampened Ca(2+) regulation and decreased proliferation compared to CSM from the wall. CONCLUSIONS: These CSM Ca(2+) regulation data from several time points in CAD progression and severity help to resolve the controversy regarding up-vs. down-regulation of CSM Ca(2+) regulation in previous reports. These data are consistent with the hypothesis that alterations in sarcoplasmic reticulum Ca(2+) contribute to progression of atherosclerotic CAD in MetS.Item CARDIOVASCULAR AND HEMODYNAMIC EFFECTS OF GLUCAGON-LIKE PEPTIDE-1(Springer US, 2014-09) Goodwill, Adam G.; Mather, Kieren J.; Conteh, Abass M.; Sassoon, Daniel; Noblet, Jillian N.; Tune, Johnathan D.; Department of Cellular & Integrative Physiology, School of MedicineGlucagon-like peptide-1 (GLP-1) is an incretin hormone that has been shown to have hemodynamic and cardioprotective capacity in addition to its better characterized glucoregulatory actions. Because of this, emerging research has focused on the ability of GLP-1 based therapies to drive myocardial substrate selection, enhance cardiac performance and regulate heart rate, blood pressure and vascular tone. These studies have produced consistent and reproducible results amongst numerous laboratories. However, there are obvious disparities in findings obtained in small animal models versus those of higher mammals. This species dependent discrepancy calls to question, the translational value of individual findings. Moreover, few studies of GLP-1 mediated cardiovascular action have been performed in the presence of a pre-existing comorbidities (e.g. obesity/diabetes) which limits interpretation of the effectiveness of incretin-based therapies in the setting of disease. This review addresses cardiovascular and hemodynamic potential of GLP-1 based therapies with attention to species specific effects as well as the interaction between therapies and disease.Item Cardiovascular consequences of metabolic syndrome(Elsevier, 2017-05) Tune, Johnathan D.; Goodwill, Adam G.; Sassoon, Daniel J.; Mather, Kieren J.; Cellular and Integrative Physiology, School of MedicineThe metabolic syndrome (MetS) is defined as the concurrence of obesity-associated cardiovascular risk factors including abdominal obesity, impaired glucose tolerance, hypertriglyceridemia, decreased HDL cholesterol, and/or hypertension. Earlier conceptualizations of the MetS focused on insulin resistance as a core feature, and it is clearly coincident with the above list of features. Each component of the MetS is an independent risk factor for cardiovascular disease and the combination of these risk factors elevates rates and severity of cardiovascular disease, related to a spectrum of cardiovascular conditions including microvascular dysfunction, coronary atherosclerosis and calcification, cardiac dysfunction, myocardial infarction, and heart failure. While advances in understanding the etiology and consequences of this complex disorder have been made, the underlying pathophysiological mechanisms remain incompletely understood, and it is unclear how these concurrent risk factors conspire to produce the variety of obesity-associated adverse cardiovascular diseases. In this review, we highlight current knowledge regarding the pathophysiological consequences of obesity and the MetS on cardiovascular function and disease, including considerations of potential physiological and molecular mechanisms that may contribute to these adverse outcomes.Item Combination GLP-1 and Insulin Treatment Fails to Alter Myocardial Fuel Selection Versus Insulin Alone in Type 2 Diabetes(Oxford, 2018-07) Mather, Kieren J.; Considine, Robert V.; Hamilton, LaTonya; Patel, Niral A.; Mathias, Carla; Territo, Wendy; Goodwill, Adam; Tune, Johnathan D.; Green, Mark A.; Hutchins, Gary D.; Medicine, School of MedicineContext Glucagon-like peptide-1 (GLP-1) and the clinically available GLP-1 agonists have been shown to exert effects on the heart. It is unclear whether these effects occur at clinically used doses in vivo in humans, possibly contributing to CVD risk reduction. Objective To determine whether liraglutide at clinical dosing augments myocardial glucose uptake alone or in combination with insulin compared to insulin alone in metformin-treated Type 2 diabetes mellitus. Design Comparison of myocardial fuel utilization after 3 months of treatment with insulin detemir, liraglutide, or combination detemir+liraglutide. Setting Academic hospital Participants Type 2 diabetes treated with metformin plus oral agents or basal insulin. Interventions Insulin detemir, liraglutide, or combination added to background metformin Main Outcome Measures Myocardial blood flow, fuel selection and rates of fuel utilization evaluated using positron emission tomography, powered to demonstrate large effects. Results We observed greater myocardial blood flow in the insulin-treated groups (median[25th, 75th percentile]: detemir 0.64[0.50, 0.69], liraglutide 0.52[0.46, 0.58] and detemir+liraglutide 0.75[0.55, 0.77] mL/g/min, p=0.035 comparing 3 groups and p=0.01 comparing detemir groups to liraglutide alone). There were no evident differences between groups in myocardial glucose uptake (detemir 0.040[0.013, 0.049], liraglutide 0.055[0.019, 0.105], detemir+liraglutide 0.037[0.009, 0.046] µmol/g/min, p=0.68 comparing 3 groups). Similarly there were no treatment group differences in measures of myocardial fatty acid uptake or handling, and no differences in total oxidation rate. Conclusions These observations argue against large effects of GLP-1 agonists on myocardial fuel metabolism as mediators of beneficial treatment effects on myocardial function and ischemia protection.Item Comparison of isoflurane and α-chloralose in an anesthetized swine model of acute pulmonary embolism producing right ventricular dysfunction(American Association for Laboratory Animal Science, 2015-02) Beam, Daren M.; Neto-Neves, Evandro M.; Stubblefield, William B.; Alves, Nathan J.; Tune, Johnathan D.; Kline, Jeffrey A.; Department of Emergency Medicine, IU School of MedicinePulmonary embolism (PE) is a leading cause of sudden cardiac death, and a model is needed for testing potential treatments. In developing a model, we compared the hemodynamic effects of isoflurane and α-chloralose in an acute swine model of PE because the choice of anesthesia will likely affect the cardiovascular responses of an animal to PE. At baseline, swine that received α-chloralose (n = 6) had a lower heart rate and cardiac output and higher SpO2, end-tidal CO2, and mean arterial pressure than did those given isoflurane (n = 9). After PE induction, swine given α-chloralose compared with isoflurane exhibited a lower heart rate (63 ± 10 compared with 116 ± 15 bpm) and peripheral arterial pressure (52 ± 12 compared with 61 ± 12 mm Hg); higher SpO2 (98% ± 3% compared with 95% ± 1%), end-tidal CO2 (35 ± 4 compared with 32 ± 5), and systolic blood pressure (121 ± 8 compared with 104 ± 20 mm Hg); and equivalent right ventricular:left ventricular ratios (1.32 ± 0.50 compared with 1.23 ± 0.19) and troponin I mean values (0.09 ± 0.07 ng/mL compared with 0.09 ± 0.06 ng/mL). Isoflurane was associated with widely variable fibrinogen and activated partial thromboplastin time. Intraexperiment mortality was 0 of 6 animals for α-chloralose and 2 of 9 swine for isoflurane. All swine anesthetized with α-chloralose survived with sustained pulmonary hypertension, RV-dilation-associated cardiac injury without the confounding vasodilatory or coagulatory effects of isoflurane. These data demonstrate the physiologic advantages of α-chloralose over isoflurane for anesthesia in a swine model of severe submassive PE.Item Contribution of electromechanical coupling between KV and CaV1.2 channels to coronary dysfunction in obesity(Springer, 2013) Berwick, Zachary C.; Dick, Gregory M.; O’Leary, Heather A.; Bender, Shawn B.; Goodwill, Adam G.; Moberly, Steven P.; Kohr Owen, Meredith; Miller, Steven J.; Obukhov, Alexander G.; Tune, Johnathan D.; Cellular and Integrative Physiology, School of MedicinePrevious investigations indicate that diminished functional expression of voltage-dependent K(+) (KV) channels impairs control of coronary blood flow in obesity/metabolic syndrome. The goal of this investigation was to test the hypothesis that KV channels are electromechanically coupled to CaV1.2 channels and that coronary microvascular dysfunction in obesity is related to subsequent increases in CaV1.2 channel activity. Initial studies revealed that inhibition of KV channels with 4-aminopyridine (4AP, 0.3 mM) increased intracellular [Ca(2+)], contracted isolated coronary arterioles and decreased coronary reactive hyperemia. These effects were reversed by blockade of CaV1.2 channels. Further studies in chronically instrumented Ossabaw swine showed that inhibition of CaV1.2 channels with nifedipine (10 μg/kg, iv) had no effect on coronary blood flow at rest or during exercise in lean swine. However, inhibition of CaV1.2 channels significantly increased coronary blood flow, conductance, and the balance between coronary flow and metabolism in obese swine (P < 0.05). These changes were associated with a ~50 % increase in inward CaV1.2 current and elevations in expression of the pore-forming subunit (α1c) of CaV1.2 channels in coronary smooth muscle cells from obese swine. Taken together, these findings indicate that electromechanical coupling between KV and CaV1.2 channels is involved in the regulation of coronary vasomotor tone and that increases in CaV1.2 channel activity contribute to coronary microvascular dysfunction in the setting of obesity.Item Contribution of hydrogen sulfide to the control of coronary blood flow(Wiley, 2014-02) Casalini, Eli D.; Goodwill, Adam G.; Owen, Meredith K.; Moberly, Steven P.; Berwick, Zachary C.; Tune, Johnathan D.; Department of Cellular & Integrative Physiology, IU School of MedicineThis study examined the mechanisms by which H2S modulates coronary microvascular resistance and myocardial perfusion at rest and in response to cardiac ischemia. Experiments were conducted in isolated coronary arteries and in open-chest anesthetized dogs. We found that the H2S substrate L-cysteine (1-10 mM) did not alter coronary tone of isolated arteries in vitro or coronary blood flow in vivo. In contrast, intracoronary (ic) H2S (0.1-3 mM) increased coronary flow from 0.49 ± 0.08 to 2.65 ± 0.13 ml/min/g (P□0.001). This increase in flow was unaffected by inhibition of Kv channels with 4-aminopyridine (P=0.127) but was attenuated (0.23 ± 0.02 to 1.13 ± 0.13 ml/min/g) by the KATP channel antagonist glibenclamide (P□0.001). Inhibition of NO synthesis (L-NAME) did not attenuate coronary responses to H2S. Immunohistochemistry revealed expression of cystathionine gamma-lyase (CSE), an endogenous H2S enzyme, in myocardium. Inhibition of CSE with β-cyano-L-alanine (10 µM) had no effect on baseline coronary flow or responses to a 15 sec coronary occlusion (P=0.82). These findings demonstrate that exogenous H2S induces potent, endothelial-independent dilation of the coronary microcirculation predominantly through the activation of KATP channels, however, our data do not support a functional role for endogenous H2S in the regulation of coronary microvascular resistance.Item Contribution of K+ Channels to Coronary Dysfunction in Metabolic Syndrome(2009-06-24T12:58:39Z) Watanabe, Reina; Tune, Johnathan D.Coronary microvascular function is markedly impaired by the onset of the metabolic syndrome and may be an important contributor to the increased cardiovascular events associated with this mutlifactorial disorder. Despite increasing appreciation for the role of coronary K+ channels in regulation of coronary microvascular function, the contribution of K+ channels to the deleterious influence of metabolic syndrome has not been determined. Accordingly, the overall goal of this investigation was to delineate the mechanistic contribution of K+ channels to coronary microvascular dysfunction in metabolic syndrome. Experiments were performed on Ossabaw miniature swine fed a normal maintenance diet or an excess calorie atherogenic diet that induces the classical clinical features of metabolic syndrome including obesity, insulin resistance, impaired glucose tolerance, dyslipidemia, hyperleptinemia, and atherosclerosis. Experiments involved in vivo studies of coronary blood flow in open-chest anesthetized swine as well as conscious, chronically instrumented swine and in vitro studies in isolated coronary arteries, arterioles, and vascular smooth muscle cells. We found that coronary microvascular dysfunction in the metabolic syndrome significantly impairs coronary vasodilation in response to metabolic as well as ischemic stimuli. This impairment was directly related to decreased membrane trafficking and functional expression of BKCa channels in vascular smooth muscle cells that was accompanied by augmented L-type Ca2+ channel activity and increased intracellular Ca2+ concentration. In addition, we discovered that impairment of coronary vasodilation in the metabolic syndrome is mediated by reductions in the functional contribution of voltage-dependent K+ channels to the dilator response. Taken together, findings from this investigation demonstrate that the metabolic syndrome markedly attenuates coronary microvascular function via the diminished contribution of K+ channels to the overall control of coronary blood flow. Our data implicate impaired functional expression of coronary K+ channels as a critical mechanism underlying the increased incidence of cardiac arrhythmias, infarction and sudden cardiac death in obese patients with the metabolic syndrome.Item Contribution of Perivascular Adipose Tissue to Coronary Vascular Dysfunction(2011-03-10) Payne, Gregory Allen; Tune, Johnathan D.; Bohlen, H. Glenn; Considine, Robert V.; Sturek, Michael StephenThe epidemic of obesity and associated cardiovascular complications continues to grow at an alarming rate. Currently, obesity is thought to initiate a state of chronic inflammation, which if unresolved potentially causes cardiovascular dysfunction and disease. Although poorly understood, release of inflammatory mediators and other cytokines from adipose tissue (adipocytokines) has been proposed to be the molecular link between obesity and coronary artery disease. Furthermore, the anatomic location of adipose has been increasingly recognized as a potential contributor to vascular disease. Importantly, the development of coronary atherosclerosis, a key component of heart disease, is typically found in segments of coronary arteries surrounded by perivascular adipose tissue. Accordingly, the goal of this project was to determine how perivascular adipose tissue affects coronary artery function and elucidate the critical mechanisms involved. Initial studies assessing arterial function were conducted with and without perivascular adipose tissue. Preliminary results demonstrated that factors released by perivascular adipose tissue effectively impaired coronary endothelial function both in vitro and in vivo. This observation was determined to be caused by direct inhibition of nitric oxide synthase (NOS), a critical enzyme for the production nitric oxide. Attenuation of endothelium-dependent vasodilation was independent of changes in superoxide production, smooth muscle response, or peroxide-mediated vasodilation. Additional studies revealed that perivascular adipose-induced impairment of NOS was due to increased inhibitory regulation by the β isoform of protein kinase C (PKC-β). Specifically, perivascular adipose-derived factors caused site specific phosphorylation of nitric oxide synthase at Thr-495. Additional experiments investigated how perivascular adipose-derived factors contributed to coronary artery disease in an animal model of obesity. Results from these studies indicated that perivascular adipose-derived leptin markedly exacerbated underlying endothelial dysfunction, and significantly contributed to coronary endothelial dysfunction through a PKC-β dependent mechanism. Findings from this project confirm epicardial perivascular adipose tissue as a local source of harmful adipocytokines. In addition, perivascular adipose-derived leptin was demonstrated to be a critical mediator of coronary vascular dysfunction in obesity. Together, the results strongly suggest that perivascular adipose tissue is a key contributor to coronary artery disease in obesity.Item Coronary artery disease in metabolic syndrome: a role for the sarcoplasmic reticulum Ca2+ ATPase(2016-05-10) Rodenbeck, Stacey Dineen; Sturek, Michael S.; Day, Richard N.; Evans-Molina, Carmella; Mather, Kieren; Tune, Johnathan D.Coronary artery disease (CAD) is a leading cause of death among Americans and is fueled by underlying metabolic syndrome (MetS). The prevalence and lethality of CAD necessitates rigorous investigations into its underlying mechanisms and to facilitate the development of effective treatment options. Coronary smooth muscle (CSM) phenotypic modulation from quiescent to synthetic, proliferative, and osteogenic phenotypes is a key area of investigation, with underlying mechanisms that remain poorly understood. Using a well-established pre-clinical model of CAD and MetS, the Ossabaw miniature swine, we established for the first time the time course of Ca2+ dysregulation during MetS-induced CAD progression. In particular, we used the fluorescent Ca2+ dye, fura-2, to examine alterations in CSM intracellular Ca2+ regulation during CAD progression, as perturbations in intracellular Ca2+ regulation are implicated in several cellular processes associated with CAD pathology, including CSM contractile responses and proliferative pathways. These studies revealed that the function of several CSM Ca2+ handling proteins is elevated in early CAD, followed by loss of function in severe atherosclerotic plaques. Decreased intracellular Ca2+ regulation occurred concurrently with reductions in CSM proliferation, measured with Ki-67 staining. In particular, alterations in sarcoplasmic reticulum (SR) Ca2+ store together with altered function of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) were associated with induction of proliferation. Organ culture of coronary arterial segments revealed that culture-induced medial thickening was prevented by SERCA inhibition with cyclopiazonic acid (CPA). Activation of SERCA with the small molecule activator, CDN1163, increased CSM proliferation, which was attenuated by treatment with CPA, thus establishing upregulated SERCA function as a proximal inducer of CSM proliferation. Further, we demonstrated that in vitro treatment of CSM from lean Ossabaw swine with the glucagon-like peptide-1 (GLP-1) receptor agonist, exenatide, increased SERCA function. However, in vivo treatment of Ossabaw swine with MetS with the GLP-1 receptor agonist, AC3174, had no effect on CAD progression and in vitro examination revealed resistance of SERCA to GLP-1 receptor agonism in MetS. These findings further implicate SERCA in CAD progression. Collectively, these are the first data directly linking SERCA dysfunction to CSM proliferation and CAD progression, providing a key mechanistic step in CAD progression.