Sanjeev Francis

PPARs and their metabolic modulation: new mechanisms for transcriptional regulation?

Peroxisome proliferator‐activated receptors (PPARs) as ligand‐activated nuclear receptors involved in the transcriptional regulation of lipid metabolism, energy balance, inflammation, and atherosclerosis are at the intersection of key pathways involved in the pathogenesis of diabetes and cardiovascular disease. Synthetic PPAR agonists like fibrates (PPAR‐α) and thiazolidinediones (PPAR‐γ) are in therapeutic use to treat dyslipidaemia and diabetes. Despite strong encouraging in vitro, animal model, and human surrogate marker studies with these agents, recent prospective clinical cardiovascular trials have yielded mixed results, perhaps explained by concomitant drug use, study design, or a lack of efficacy of these agents on cardiovascular disease (independent of their current metabolic indications). The use of PPAR agents has also been limited by untoward effects. An alternative strategy to PPAR therapeutics is better understanding PPAR biology, the nature of natural PPAR agonists, and how these molecules are generated. Such insight might also provide valuable information about pathways that protect against the metabolic problems for which PPAR agents are currently indicated. This approach underscores the important distinction between the effects of synthetic PPAR agonists and the unequivocal biologic role of PPARs as key transcriptional regulators of metabolic and inflammatory pathways relevant to diabetes and atherosclerosis.

Left Ventricular Mass in Patients With a Cardiomyopathy After Treatment With Anthracyclines

We aimed to describe the cardiac magnetic resonance (CMR) findings and determine the prognostic variables in patients with a cardiomyopathy after treatment with anthracyclines. CMR imaging was performed in 91 patients (58% men, mean age 43 ± 18 years, and mean anthracycline dose of 276 ± 82 mg/m(2)) with a reduced ejection fraction after anthracycline-based chemotherapy. Major adverse cardiovascular events were defined as cardiovascular death, appropriate implantable cardioverter-defibrillator therapy, and admission for decompensated heart failure. Patients presented a median of 88 months (interquartile range 37 to 138) after chemotherapy and were followed for 27 months (interquartile range 22 to 38). Late gadolinium enhancement was an uncommon finding (5 patients, 6%) despite a reduced ejection fraction (36 ± 8%). An inverse association was found between the anthracycline dose and the indexed left ventricular (LV) mass by CMR (r = -0.67, p <0.001). A total of 52 adverse cardiac events occurred (event rate of 22%/year). When the patients were grouped according to the presence or absence of a major adverse cardiovascular event, the indexed LV mass and glomerular filtration rate were lower and the anthracycline dose was greater among the patients who experienced an adverse event. In a multivariate model, the indexed LV mass demonstrated the strongest association with major adverse cardiovascular events (hazard ratio 0.89, chi-square 26, p <0.001). In conclusion, myocardial scar by late gadolinium enhancement-CMR is infrequent in patients with anthracycline-cardiomyopathy despite a reduced ejection fraction, the event rate in patients with established anthracycline-cardiotoxicity is high, and indexed LV mass by CMR imaging is a predictor of adverse cardiovascular events.

Stress myocardial perfusion imaging by CMR provides strong prognostic value to cardiac events regardless of patient's sex.

OBJECTIVES The major aim of this study is to test the hypothesis that stress cardiac magnetic resonance (CMR) imaging can provide robust prognostic value in women presenting with suspected ischemia, to the same extent as in men. BACKGROUND Compelling evidence indicates that women with coronary artery disease (CAD) experience worse outcomes than men owing to a lack of early diagnosis and management. Numerous clinical studies have shown that stress CMR detects evidence of myocardial ischemia and infarction at high accuracy. Compared to nuclear scintigraphy, CMR is free of ionizing radiation, has high spatial resolution for imaging small hearts, and overcomes breast attenuation artifacts, which are substantial advantages when imaging women for CAD. METHODS We performed stress CMR in 405 patients (168 women, mean age 58 ± 14 years) referred for ischemia assessment. CMR techniques included cine cardiac function, perfusion imaging during vasodilating stress, and late gadolinium enhancement imaging. All patients were followed for major adverse cardiac events (MACE). RESULTS At a median follow-up of 30 months, MACE occurred in 36 patients (9%) including 21 cardiac deaths and 15 acute myocardial infarctions. In women, CMR evidence of ischemia (ISCHEMIA) demonstrated strong association with MACE (unadjusted hazard ratio: 49.9, p < 0.0001). While women with ISCHEMIA(+) had an annual MACE rate of 15%, women with ISCHEMIA(-) had very low annual MACE rate (0.3%), which was not statistically different from the low annual MACE rate in men with ISCHEMIA(-) (1.1%). CMR myocardial ischemia score was the strongest multivariable predictor of MACE in this cohort, for both women and men, indicating robust cardiac prognostication regardless of sex. CONCLUSIONS In addition to avoiding exposure to ionizing radiation, stress CMR myocardial perfusion imaging is an effective and robust risk-stratifying tool for patients of either sex presenting with possible ischemia.

Leukotriene E4 Activates Peroxisome Proliferator-activated Receptor γ and Induces Prostaglandin D2 Generation by Human Mast Cells

Cysteinyl leukotrienes (cys-LTs) are potent inflammatory lipid mediators, of which leukotriene (LT) E4 is the most stable and abundant in vivo. Although only a weak agonist of established G protein-coupled receptors (GPCRs) for cys-LTs, LTE4 potentiates airway hyper-responsiveness (AHR) by a cyclooxygenase (COX)-dependent mechanism and induces bronchial eosinophilia. We now report that LTE4 activates human mast cells (MCs) by a pathway involving cooperation between an MK571-sensitive GPCR and peroxisome proliferator-activated receptor (PPAR)γ, a nuclear receptor for dietary lipids. Although LTD4 is more potent than LTE4 for inducing calcium flux by the human MC sarcoma line LAD2, LTE4 is more potent for inducing proliferation and chemokine generation, and is at least as potent for upregulating COX-2 expression and causing prostaglandin D2 (PGD2) generation. LTE4 caused phosphorylation of extracellular signal-regulated kinase (ERK), p90RSK, and cyclic AMP-regulated-binding protein (CREB). ERK activation in response to LTE4, but not to LTD4, was resistant to inhibitors of phosphoinositol 3-kinase. LTE4-mediated COX-2 induction, PGD2 generation, and ERK phosphorylation were all sensitive to interference by the PPARγ antagonist GW9662 and to targeted knockdown of PPARγ. Although LTE4-mediated PGD2 production was also sensitive to MK571, an antagonist for the type 1 receptor for cys-LTs (CysLT1R), it was resistant to knockdown of this receptor. This LTE4-selective receptor-mediated pathway may explain the unique physiologic responses of human airways to LTE4 in vivo.

Effect of Omega-3 Acid Ethyl Esters on Left Ventricular Remodeling After Acute Myocardial Infarction: The OMEGA-REMODEL Randomized Clinical Trial.

Background: Omega-3 fatty acids from fish oil have been associated with beneficial cardiovascular effects, but their role in modifying cardiac structures and tissue characteristics in patients who have had an acute myocardial infarction while receiving current guideline-based therapy remains unknown. Methods: In a multicenter, double-blind, placebo-controlled trial, participants presenting with an acute myocardial infarction were randomly assigned 1:1 to 6 months of high-dose omega-3 fatty acids (n=180) or placebo (n=178). Cardiac magnetic resonance imaging was used to assess cardiac structure and tissue characteristics at baseline and after study therapy. The primary study endpoint was change in left ventricular systolic volume index. Secondary endpoints included change in noninfarct myocardial fibrosis, left ventricular ejection fraction, and infarct size. Results: By intention-to-treat analysis, patients randomly assigned to omega-3 fatty acids experienced a significant reduction of left ventricular systolic volume index (–5.8%, P=0.017), and noninfarct myocardial fibrosis (–5.6%, P=0.026) in comparison with placebo. Per-protocol analysis revealed that those patients who achieved the highest quartile increase in red blood cell omega-3 index experienced a 13% reduction in left ventricular systolic volume index in comparison with the lowest quartile. In addition, patients in the omega-3 fatty acid arm underwent significant reductions in serum biomarkers of systemic and vascular inflammation and myocardial fibrosis. There were no adverse events associated with high-dose omega-3 fatty acid therapy. Conclusions: Treatment of patients with acute myocardial infarction with high-dose omega-3 fatty acids was associated with reduction of adverse left ventricular remodeling, noninfarct myocardial fibrosis, and serum biomarkers of systemic inflammation beyond current guideline-based standard of care. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00729430.

Pioglitazone Suppresses Inflammation In Vivo in Murine Carotid Atherosclerosis Novel Detection by Dual-Target Fluorescence Molecular Imaging

Objective—To investigate the effects of pioglitazone (PIO), a peroxisome proliferator-activated receptor &ggr; agonist, on plaque matrix metalloproteinase (MMP) and macrophage (Mac) responses in vivo in a molecular imaging study. Methods and Results—In vitro, PIO suppressed MMP-9 protein expression in murine peritoneal Macs (P<0.05). To assess PIOs effects on plaque inflammation, nondiabetic apolipoprotein E−/− mice receiving a high-cholesterol diet (HCD) were administered an MMP-activatable fluorescence imaging agent and a spectrally distinct Mac-avid fluorescent nanoparticle. After 24 hours, mice underwent survival dual-target intravital fluorescence microscopy of carotid arterial plaques. These mice were then randomized to HCD or HCD plus 0.012% PIO for 8 weeks, followed by a second intravital fluorescence microscopy study of the same carotid plaque. In the HCD group, in vivo MMP and Mac target-to-background ratios increased similarly (P<0.01 versus baseline). In contrast, PIO reduced MMP and Mac target-to-background ratios (P<0.01) versus HCD. Changes in MMP and Mac signals correlated strongly (r ≥0.75). Microscopy demonstrated MMP and Mac reductions in PIO-treated mice and a PIO-modulated increase in plaque collagen. Conclusion—Serial optical molecular imaging demonstrates that plaque MMP and Mac activity in vivo intensify with hypercholesterolemia and are reduced by PIO therapy.

Stress Cardiac Magnetic Resonance Imaging Provides Effective Cardiac Risk Reclassification in Patients With Known or Suspected Stable Coronary Artery Disease

Background— A recent large-scale clinical trial found that an initial invasive strategy does not improve cardiac outcomes beyond optimized medical therapy in patients with stable coronary artery disease. Novel methods to stratify at-risk patients may refine therapeutic decisions to improve outcomes. Methods and Results— In a cohort of 815 consecutive patients referred for evaluation of myocardial ischemia, we determined the net reclassification improvement of the risk of cardiac death or nonfatal myocardial infarction (major adverse cardiac events) incremental to clinical risk models, using guideline-based low (<1%), moderate (1% to 3%), and high (>3%) annual risk categories. In the whole cohort, inducible ischemia demonstrated a strong association with major adverse cardiac events (hazard ratio=14.66; P<0.0001) with low negative event rates of major adverse cardiac events and cardiac death (0.6% and 0.4%, respectively). This prognostic robustness was maintained in patients with previous coronary artery disease (hazard ratio=8.17; P<0.0001; 1.3% and 0.6%, respectively). Adding inducible ischemia to the multivariable clinical risk model (adjusted for age and previous coronary artery disease) improved discrimination of major adverse cardiac events (C statistic, 0.81–0.86; P=0.04; adjusted hazard ratio=7.37; P<0.0001) and reclassified 91.5% of patients at moderate pretest risk (65.7% to low risk; 25.8% to high risk) with corresponding changes in the observed event rates (0.3%/y and 4.9%/y for low and high risk posttest, respectively). Categorical net reclassification index was 0.229 (95% confidence interval, 0.063–0.391). Continuous net reclassification improvement was 1.11 (95% confidence interval, 0.81–1.39). Conclusions— Stress cardiac magnetic resonance imaging effectively reclassifies patient risk beyond standard clinical variables, specifically in patients at moderate to high pretest clinical risk and in patients with previous coronary artery disease. Clinical Trial Registration:— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01821924.

Endothelial Lipase Is a Critical Determinant of High-Density Lipoprotein–Stimulated Sphingosine 1-Phosphate–Dependent Signaling in Vascular Endothelium

Objective—In addition to an extensively characterized role of high-density lipoprotein (HDL) in reverse cholesterol transport, bioactive lipids bound to HDL can also exert diverse vascular effects. Despite this, integration of HDL action in the vasculature with pathways that metabolize HDL and release bioactive lipids has been much less explored. The effects of HDL on endothelial cells are mediated in part by HDL-associated sphingosine 1-phosphate (S1P), which binds to S1P1 receptors and promotes activation of endothelial NO synthase (eNOS) and the kinase Akt. In these studies, we characterized the role of endothelial lipase (EL) in the control of endothelial signaling and biology, including those mediated by HDL-associated S1P. Approach and Results—HDL-induced angiogenesis in aortic rings from EL-deficient (EL−/−) mice was markedly decreased compared with wild-type controls. In cultured endothelial cells, small interfering RNA–mediated knockdown of EL abrogated HDL-promoted endothelial cell migration and tube formation. Small interfering RNA–mediated EL knockdown also attenuated HDL-induced phosphorylation of eNOS1179 and Akt473. S1P stimulation restored HDL-induced endothelial migration and Akt/eNOS phosphorylation that had been blocked by small interfering RNA–mediated EL knockdown. HDL-induced endothelial cell migration and Akt/eNOS phosphorylation were completely inhibited by the S1P1 antagonist W146 but not by the S1P3 antagonist CAY10444. Conclusions—EL is a critical determinant of the effects of HDL on S1P-mediated vascular responses and acts on HDL to promote activation of S1P1, leading to Akt/eNOS phosphorylation and subsequent endothelial migration and angiogenesis. The role of EL in HDL-associated S1P effects provides new insights into EL action, the responses seen through EL and HDL interaction, and S1P signaling.

Heart Failure and Breast Cancer Therapies: Moving Towards Personalized Risk Assessment

Cardio-oncology, a new clinical discipline focused on the cardiovascular care of cancer patients, represents a new avenue for interdisciplinary collaboration between clinical oncologists and cardiologists as well as between basic scientists and clinical investigators.[1][1] Many of these

Cost-effectiveness analysis for imaging techniques with a focus on cardiovascular magnetic resonance

With the need for healthcare cost-containment, increased scrutiny will be placed on new medical therapeutic or diagnostic technologies. Several challenges exist for a new diagnostic test to demonstrate cost-effectiveness. New diagnostic tests differ from therapeutic procedures due to the fact that diagnostic tests do not generally directly affect long-term patient outcomes. Instead, the results of diagnostic tests can influence management decisions for patients and by this route, diagnostic tests indirectly affect long-term outcomes. The benefits from a specific diagnostic technology depend therefore not only on its performance characteristics, but also on other factors such as prevalence of disease, and effectiveness of existing treatments for the disease of interest. We review the concepts and theories of cost-effectiveness analyses (CEA) as they apply to diagnostic tests in general. The limitations of CEA across different study designs and geographic regions are discussed, and we also examine the strengths and weakness of the existing publications where CMR was the focus of CEA compared to other diagnostic options.