SGLT2 inhibitor ertugliflozin decreases elevated intracellular sodium, and improves energetics and contractile function in diabetic cardiomyopathy.

BACKGROUND: Elevated myocardial intracellular sodium ([Na+]i) was shown to decrease mitochondrial calcium ([Ca2+]MITO) via mitochondrial sodium/calcium exchanger (NCXMITO), resulting in decreased mitochondrial ATP synthesis. The sodium-glucose co-transporter 2 inhibitor (SGLT2i) ertugliflozin (ERTU) improved energetic deficit and contractile dysfunction in a mouse model of high fat, high sucrose (HFHS) diet-induced diabetic cardiomyopathy (DCMP). As SGLT2is were shown to lower [Na+]i in isolated cardiomyocytes, we hypothesized that energetic improvement in DCMP is at least partially mediated by a decrease in abnormally elevated myocardial [Na+]i. METHODS: Forty-two eight-week-old male C57BL/6J mice were fed a control or HFHS diet for six months. In the last month, a subgroup of HFHS-fed mice was treated with ERTU. At the end of the study, left ventricular contractile function and energetics were measured simultaneously in isolated beating hearts by 31P NMR (Nuclear Magnetic Resonance) spectroscopy. A subset of untreated HFHS hearts was perfused with vehicle vs. CGP 37157, an NCXMITO inhibitor. Myocardial [Na+]i was measured by 23Na NMR spectroscopy. RESULTS: HFHS hearts showed diastolic dysfunction, decreased contractile reserve, and impaired energetics as reflected by decreased phosphocreatine (PCr) and PCr/ATP ratio. Myocardial [Na+]i was elevated > 2-fold in HFHS (vs. control diet). ERTU reversed the impairments in HFHS hearts to levels similar to or better than control diet and decreased myocardial [Na+]i to control levels. CGP 37157 normalized the PCr/ATP ratio in HFHS hearts. CONCLUSIONS: Elevated myocardial [Na+]i contributes to mitochondrial and contractile dysfunction in DCMP. Targeting myocardial [Na+]i and/or NCXMITO may be an effective strategy in DCMP and other forms of heart disease associated with elevated myocardial [Na+]i.

A soft robotic sleeve mimicking the haemodynamics and biomechanics of left ventricular pressure overload and aortic stenosis.

Preclinical models of aortic stenosis can induce left ventricular pressure overload and coarsely control the severity of aortic constriction. However, they do not recapitulate the haemodynamics and flow patterns associated with the disease. Here we report the development of a customizable soft robotic aortic sleeve that can mimic the haemodynamics and biomechanics of aortic stenosis. By allowing for the adjustment of actuation patterns and blood-flow dynamics, the robotic sleeve recapitulates clinically relevant haemodynamics in a porcine model of aortic stenosis, as we show via in vivo echocardiography and catheterization studies, and a combination of in vitro and computational analyses. Using in vivo and in vitro magnetic resonance imaging, we also quantified the four-dimensional blood-flow velocity profiles associated with the disease and with bicommissural and unicommissural defects re-created by the robotic sleeve. The design of the sleeve, which can be adjusted on the basis of computed tomography data, allows for the design of patient-specific devices that may guide clinical decisions and improve the management and treatment of patients with aortic stenosis.

Effects of Sodium-Glucose Linked Transporter 2 Inhibition With Ertugliflozin on Mitochondrial Function, Energetics, and Metabolic Gene Expression in the Presence and Absence of Diabetes Mellitus in Mice.

Background Inhibitors of the sodium-glucose linked transporter 2 improve cardiovascular outcomes in patients with or without type 2 diabetes mellitus, but the effects on cardiac energetics and mitochondrial function are unknown. We assessed the effects of sodium-glucose linked transporter 2 inhibition on mitochondrial function, high-energy phosphates, and genes encoding mitochondrial proteins in hearts of mice with and without diet-induced diabetic cardiomyopathy. Methods and Results Mice fed a control diet or a high-fat, high-sucrose diet received ertugliflozin mixed with the diet (0.5 mg/g of diet) for 4 months. Isolated mitochondria were assessed for functional capacity. High-energy phosphates were assessed by 31P nuclear magnetic resonance spectroscopy concurrently with contractile performance in isolated beating hearts. The high-fat, high-sucrose diet caused myocardial hypertrophy, diastolic dysfunction, mitochondrial dysfunction, and impaired energetic response, all of which were prevented by ertugliflozin. With both diets, ertugliflozin caused supernormalization of contractile reserve, as measured by rate×pressure product at high work demand. Likewise, the myocardial gene sets most enriched by ertugliflozin were for oxidative phosphorylation and fatty acid metabolism, both of which were enriched independent of diet. Conclusions Ertugliflozin not only prevented high-fat, high-sucrose-induced pathological cardiac remodeling, but improved contractile reserve and induced the expression of oxidative phosphorylation and fatty acid metabolism gene sets independent of diabetic status. These effects of sodium-glucose linked transporter 2 inhibition on cardiac energetics and metabolism may contribute to improved structure and function in cardiac diseases associated with mitochondrial dysfunction, such as heart failure.

Differential Effects of Sacubitril/Valsartan on Diastolic Function in Mice With Obesity-Related Metabolic Heart Disease.

Mice with obesity and metabolic heart disease (MHD) due to a high-fat, high-sucrose diet were treated with placebo, a clinically relevant dose of sacubitril (SAC)/valsartan (VAL), or an equivalent dose of VAL for 4 months. There were striking differences between SAC/VAL and VAL with regard to: 1) diastolic dysfunction; 2) interstitial fibrosis; and to a lesser degree; 3) oxidative stress-all of which were more favorably affected by SAC/VAL. SAC/VAL and VAL similarly attenuated myocardial hypertrophy and improved myocardial energetics. In mice with obesity-related MHD, neprilysin inhibition exerts favorable effects on diastolic function.

Redox-Resistant SERCA [Sarco(endo)plasmic Reticulum Calcium ATPase] Attenuates Oxidant-Stimulated Mitochondrial Calcium and Apoptosis in Cardiac Myocytes and Pressure Overload-Induced Myocardial Failure in Mice.

BACKGROUND: SERCA [sarco(endo)plasmic reticulum calcium ATPase] is regulated by oxidative posttranslational modifications at cysteine 674 (C674). Because sarcoplasmic reticulum (SR) calcium has been shown to play a critical role in mediating mitochondrial dysfunction in response to reactive oxygen species, we hypothesized that SERCA oxidation at C674 would modulate the effects of reactive oxygen species on mitochondrial calcium and mitochondria-dependent apoptosis in cardiac myocytes. METHODS: Adult rat ventricular myocytes expressing wild-type SERCA2b or a redox-insensitive mutant in which C674 is replaced by serine (C674S) were exposed to H2O2 (100 µmol/Lµ). Free mitochondrial calcium concentration was measured in adult rat ventricular myocytes with a genetically targeted fluorescent probe, and SR calcium content was assessed by measuring caffeine-stimulated release. Mice with heterozygous knock-in of the SERCA C674S mutation were subjected to chronic ascending aortic constriction. RESULTS: In adult rat ventricular myocytes expressing wild-type SERCA, H2O2 caused a 25% increase in mitochondrial calcium concentration that was associated with a 50% decrease in SR calcium content, both of which were prevented by the ryanodine receptor inhibitor tetracaine. In cells expressing the C674S mutant, basal SR calcium content was decreased by 31% and the H2O2-stimulated rise in mitochondrial calcium concentration was attenuated by 40%. In wild-type cells, H2O2 caused cytochrome c release and apoptosis, both of which were prevented in C674S-expressing cells. In myocytes from SERCA knock-in mice, basal SERCA activity and SR calcium content were decreased. To test the effect of C674 oxidation on apoptosis in vivo, SERCA knock-in mice were subjected to chronic ascending aortic constriction. In wild-type mice, ascending aortic constriction caused myocyte apoptosis, LV dilation, and systolic failure, all of which were inhibited in SERCA knock-in mice. CONCLUSIONS: Redox activation of SERCA C674 regulates basal SR calcium content, thereby mediating the pathologic reactive oxygen species-stimulated rise in mitochondrial calcium required for myocyte apoptosis and myocardial failure.

A novel tracer for in vivo optical imaging of fatty acid metabolism in the heart and brown adipose tissue.

Multiplexed imaging is essential for the evaluation of substrate utilization in metabolically active organs, such as the heart and brown adipose tissue (BAT), where substrate preference changes in pathophysiologic states. Optical imaging provides a useful platform because of its low cost, high throughput and intrinsic ability to perform composite readouts. However, the paucity of probes available for in vivo use has limited optical methods to image substrate metabolism. Here, we present a novel near-infrared (NIR) free fatty acid (FFA) tracer suitable for in vivo imaging of deep tissues such as the heart. Using click chemistry, Alexa Fluor 647 DIBO Alkyne was conjugated to palmitic acid. Mice injected with 0.05 nmol/g bodyweight of the conjugate (AlexaFFA) were subjected to conditions known to increase FFA uptake in the heart (fasting) and BAT [cold exposure and injection with the ß3 adrenergic agonist CL 316, 243(CL)]. Organs were subsequently imaged both ex vivo and in vivo to quantify AlexaFFA uptake. The blood kinetics of AlexaFFA followed a two-compartment model with an initial fast compartment half-life of 0.14 h and a subsequent slow compartment half-life of 5.2 h, consistent with reversible protein binding. Ex vivo fluorescence imaging after overnight cold exposure and fasting produced a significant increase in AlexaFFA uptake in the heart (58 ± 12%) and BAT (278 ± 19%) compared to warm/fed animals. In vivo imaging of the heart and BAT after exposure to CL and fasting showed a significant increase in AlexaFFA uptake in the heart (48 ± 20%) and BAT (40 ± 10%) compared to saline-injected/fed mice. We present a novel near-infrared FFA tracer, AlexaFFA, that is suitable for in vivo quantification of FFA metabolism and can be applied in the context of a low cost, high throughput, and multiplexed optical imaging platform.

Increasing mitochondrial ATP synthesis with butyrate normalizes ADP and contractile function in metabolic heart disease.

Metabolic heart disease (MHD), which is strongly associated with heart failure with preserved ejection fraction, is characterized by reduced mitochondrial energy production and contractile performance. In this study, we tested the hypothesis that an acute increase in ATP synthesis, via short chain fatty acid (butyrate) perfusion, restores contractile function in MHD. Isolated hearts of mice with MHD due to consumption of a high fat high sucrose (HFHS) diet or on a control diet (CD) for 4 months were studied using 31 P NMR spectroscopy to measure high energy phosphates and ATP synthesis rates during increased work demand. At baseline, HFHS hearts had increased ADP and decreased free energy of ATP hydrolysis (ΔG~ATP ), although contractile function was similar between the two groups. At high work demand, the ATP synthesis rate in HFHS hearts was reduced by over 50%. Unlike CD hearts, HFHS hearts did not increase contractile function at high work demand, indicating a lack of contractile reserve. However, acutely supplementing HFHS hearts with 4mM butyrate normalized ATP synthesis, ADP, ΔG~ATP and contractile reserve. Thus, acute reversal of depressed mitochondrial ATP production improves contractile dysfunction in MHD. These findings suggest that energy starvation may be a reversible cause of myocardial dysfunction in MHD, and opens new therapeutic opportunities.

Energetic Dysfunction Is Mediated by Mitochondrial Reactive Oxygen Species and Precedes Structural Remodeling in Metabolic Heart Disease.

Aims: Metabolic syndrome is associated with metabolic heart disease (MHD) that is characterized by left ventricular (LV) hypertrophy, interstitial fibrosis, contractile dysfunction, and mitochondrial dysfunction. Overexpression of catalase in mitochondria (transgenic expression of catalase targeted to the mitochondria [mCAT]) prevents the structural and functional features of MHD caused by a high-fat, high-sucrose (HFHS) diet for ≥4 months. However, it is unclear whether the effect of mCAT is due to prevention of reactive oxygen species (ROS)-mediated cardiac remodeling, a direct effect on mitochondrial function, or both. To address this question, we measured myocardial function and energetics in mice, with or without mCAT, after 1 month of HFHS, before the development of cardiac structural remodeling. Results: HFHS diet for 1 month had no effect on body weight, heart weight, LV structure, myocyte size, or interstitial fibrosis. Isolated cardiac mitochondria from HFHS-fed mice produced 2.2- to 3.8-fold more H2O2, and 16%-29% less adenosine triphosphate (ATP). In isolated beating hearts from HFHS-fed mice, [phosphocreatine (PCr)] and the free energy available for ATP hydrolysis (ΔG∼ATP) were decreased, and they failed to increase with work demands. Overexpression of mCAT normalized ROS and ATP production in isolated mitochondria, and it corrected myocardial [PCr] and ΔG∼ATP in the beating heart. Innovation: This is the first demonstration that in MHD, mitochondrial ROS mediate energetic dysfunction that is sufficient to impair contractile function. Conclusion: ROS produced and acting in the mitochondria impair myocardial energetics, leading to slowed relaxation and decreased contractile reserve. These effects precede structural remodeling and are corrected by mCAT, indicating that ROS-mediated energetic impairment, per se, is sufficient to cause contractile dysfunction in MHD.

Galectin-3 Is Associated With Stage B Metabolic Heart Disease and Pulmonary Hypertension in Young Obese Patients.

Background Obesity is a precursor to heart failure with preserved ejection fraction. Biomarkers that identify preclinical metabolic heart disease ( MHD ) in young obese patients would help identify high-risk individuals for heart failure prevention strategies. We assessed the predictive value of GAL3 (galectin-3), FSTL3 (follistatin-like 3 peptide), and NT-proBNP (N-terminal pro-B-type natriuretic peptide) to identify stage B MHD in young obese participants free of clinically evident cardiovascular disease. Methods and Results Asymptomatic obese patients (n=250) and non-obese controls (n=21) underwent echocardiographic cardiac phenotyping. Obese patients were classified as MHD positive ( MHD - POS ; n=94) if they had abnormal diastolic function or left ventricular hypertrophy and had estimated pulmonary artery systolic pressure ≥35 mm Hg. Obese patients without such abnormalities were classified as MHD negative (MHD-NEG; n=52). Serum biomarkers timed with echocardiography. MHD - POS and MHD-NEG individuals were similarly obese, but MHD - POS patients were older, with more diabetes mellitus and metabolic syndrome. Right ventricular coupling was worse in MHD - POS patients ( P<0.001). GAL 3 levels were higher in MHD - POS versus MHD -NEG patients (7.7±2.3 versus 6.3±1.9 ng/mL, respectively; P<0.001). Both GAL 3 and FSTL 3 levels correlated with diastolic dysfunction and increased pulmonary artery systolic pressure but not with left ventricular mass. In multivariate models including all 3 biomarkers, only GAL 3 remained associated with MHD (odds ratio: 1.30; 95% CI , 1.01-1.68; P=0.04). Conclusions In young obese individuals without known cardiovascular disease, GAL 3 is associated with the presence of preclinical MHD . GAL 3 may be useful in screening for preclinical MHD and identifying individuals with increased risk of progression to obesity-related heart failure with preserved ejection fraction.

Fusion of deep learning models of MRI scans, Mini-Mental State Examination, and logical memory test enhances diagnosis of mild cognitive impairment.

INTRODUCTION: Our aim was to investigate if the accuracy of diagnosing mild cognitive impairment (MCI) using the Mini-Mental State Examination (MMSE) and logical memory (LM) test could be enhanced by adding MRI data. METHODS: Data of individuals with normal cognition and MCI were obtained from the National Alzheimer Coordinating Center database (n = 386). Deep learning models trained on MRI slices were combined to generate a fused MRI model using different voting techniques to predict normal cognition versus MCI. Two multilayer perceptron (MLP) models were developed with MMSE and LM test results. Finally, the fused MRI model and the MLP models were combined using majority voting. RESULTS: The fusion model was superior to the individual models alone and achieved an overall accuracy of 90.9%. DISCUSSION: This study is a proof of principle that multimodal fusion of models developed using MRI scans, MMSE, and LM test data is feasible and can better predict MCI.

Multiplexed Optical Imaging of Energy Substrates Reveals That Left Ventricular Hypertrophy Is Associated With Brown Adipose Tissue Activation.

BACKGROUND: Substrate utilization in tissues with high energetic requirements could play an important role in cardiometabolic disease. Current techniques to assess energetics are limited by high cost, low throughput, and the inability to resolve multiple readouts simultaneously. Consequently, we aimed to develop a multiplexed optical imaging platform to simultaneously assess energetics in multiple organs in a high throughput fashion. METHODS AND RESULTS: The detection of 18F-Fluordeoxyglucose uptake via Cerenkov luminescence and free fatty acid uptake with a fluorescent C16 free fatty acid was tested. Simultaneous uptake of these agents was measured in the myocardium, brown/white adipose tissue, and skeletal muscle in mice with/without thoracic aortic banding. Within 5 weeks of thoracic aortic banding, mice developed left ventricular hypertrophy and brown adipose tissue activation with upregulation of ß3AR (ß3 adrenergic receptors) and increased natriuretic peptide receptor ratio. Imaging of brown adipose tissue 15 weeks post thoracic aortic banding revealed an increase in glucose (P<0.01) and free fatty acid (P<0.001) uptake versus controls and an increase in uncoupling protein-1 (P<0.01). Similar but less robust changes were seen in skeletal muscle, while substrate uptake in white adipose tissue remained unchanged. Myocardial glucose uptake was increased post-thoracic aortic banding but free fatty acid uptake trended to decrease. CONCLUSIONS: A multiplexed optical imaging technique is presented that allows substrate uptake to be simultaneously quantified in multiple tissues in a high throughput manner. The activation of brown adipose tissue occurs early in the onset of left ventricular hypertrophy, which produces tissue-specific changes in substrate uptake that may play a role in the systemic response to cardiac pressure overload.

Decreased ATP production and myocardial contractile reserve in metabolic heart disease.

Metabolic syndrome is a cluster of obesity-related metabolic abnormalities that lead to metabolic heart disease (MHD) with left ventricular pump dysfunction. Although MHD is thought to be associated with myocardial energetic deficiency, two key questions have not been answered. First, it is not known whether there is a sufficient energy deficit to contribute to pump dysfunction. Second, the basis for the energy deficit is not clear. To address these questions, mice were fed a high fat, high sucrose (HFHS) 'Western' diet to recapitulate the MHD phenotype. In isolated beating hearts, we used 31P NMR spectroscopy with magnetization transfer to determine a) the concentrations of high energy phosphates ([ATP], [ADP], [PCr]), b) the free energy of ATP hydrolysis (∆G~ATP), c) the rate of ATP production and d) flux through the creatine kinase (CK) reaction. At the lowest workload, the diastolic pressure-volume relationship was shifted upward in HFHS hearts, indicative of diastolic dysfunction, whereas systolic function was preserved. At this workload, the rate of ATP synthesis was decreased in HFHS hearts, and was associated with decreases in both [PCr] and ∆G~ATP. Higher work demands unmasked the inability of HFHS hearts to increase systolic function and led to a further decrease in ∆G~ATP to a level that is not sufficient to maintain normal function of sarcoplasmic Ca2+-ATPase (SERCA). While [ATP] was preserved at all work demands in HFHS hearts, the progressive increase in [ADP] led to a decrease in ∆G~ATP with increased work demands. Surprisingly, CK flux, CK activity and total creatine were normal in HFHS hearts. These findings differ from dilated cardiomyopathy, in which the energetic deficiency is associated with decreases in CK flux, CK activity and total creatine. Thus, in HFHS-fed mice with MHD there is a distinct metabolic phenotype of the heart characterized by a decrease in ATP production that leads to a functionally-important energetic deficiency and an elevation of [ADP], with preservation of CK flux.

Functional and anatomical characterization of brown adipose tissue in heart failure with blood oxygen level dependent magnetic resonance.

Recent studies have suggested that brown adipose tissue (BAT) plays an important role in obesity, insulin resistance and heart failure. The characterization of BAT in vivo, however, has been challenging. No technique to comprehensively image BAT anatomy and function has been described. Moreover, the impact on BAT of the neuroendocrine activation seen in heart failure has only recently begun to be evaluated in vivo. The aim of this study was to use MRI to characterize the impact of heart failure on the morphology and function of BAT. Mice subjected to permanent ligation of the left coronary artery were imaged with MRI 6 weeks later. T2 weighted MRI of BAT volume and blood oxygen level dependent MRI of BAT function were performed. T2 * maps of BAT were obtained at multiple time points before and after administration of the ß3 adrenergic agonist CL 316 243 (CL). Blood flow to BAT was studied after CL injection using the flow alternating inversion recovery (FAIR) approach. Excised BAT tissue was analyzed for lipid droplet content and for uncoupling protein 1 (UCP1) mRNA expression. BAT volume was significantly lower in heart failure (51 ± 1 mm(3) versus 65 ± 3 mm(3) ; p < 0.05), and characterized by a reduction in lipid globules and a fourfold increase in UCP1 mRNA (p < 0.05). CL injection increased BAT T2 * in healthy animals but not in mice with heart failure (24 ± 4% versus 6 ± 2%; p < 0.01), consistent with an increase in flow in control BAT. This was confirmed by a significant difference in the FAIR response in BAT in control and heart failure mice. Heart failure results in the chronic activation of BAT, decreased BAT lipid stores and decreased BAT volume, and it is associated with a marked decrease in ability to respond to acute physiological stimuli. This may have important implications for substrate utilization and overall metabolic homeostasis in heart failure. Copyright © 2016 John Wiley & Sons, Ltd.

Contrast-Enhanced Ultrasound: A Novel Noninvasive, Nonionizing Method for the Detection of Brown Adipose Tissue in Humans.

BACKGROUND: Brown adipose tissue (BAT) consumes glucose when it is activated by cold exposure, allowing its detection in humans by (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) with computed tomography (CT). The investigators recently described a novel noninvasive and nonionizing imaging method to assess BAT in mice using contrast-enhanced ultrasound (CEUS). Here, they report the application of this method in healthy humans. METHODS: Thirteen healthy volunteers were recruited. CEUS was performed before and after cold exposure in all subjects using a continuous intravenous infusion of perflutren gas-filled lipid microbubbles and triggered imaging of the supraclavicular space. The first five subjects received microbubbles at a lower infusion rate than the subsequent eight subjects and were analyzed as a separate group. Blood flow was estimated as the product of the plateau (A) and the slope (ß) of microbubble replenishment curves. All underwent (18)F-FDG PET/CT after cold exposure. RESULTS: An increase in the acoustic signal was noted in the supraclavicular adipose tissue area with increasing triggering intervals in all subjects, demonstrating the presence of blood flow. The area imaged by CEUS colocalized with BAT, as detected by ¹8F-FDG PET/CT. In a cohort of eight subjects with an optimized CEUS protocol, CEUS-derived BAT blood flow increased with cold exposure compared with basal BAT blood flow in warm conditions (median Aß = 3.3 AU/s [interquartile range, 0.5-5.7 AU/s] vs 1.25 AU/s [interquartile range, 0.5-2.6 AU/s]; P = .02). Of these eight subjects, five had greater than twofold increases in blood flow after cold exposure; these responders had higher BAT activity measured by (18)F-FDG PET/CT (median maximal standardized uptake value, 2.25 [interquartile range, 1.53-4.57] vs 0.51 [interquartile range, 0.47-0.73]; P = .02). CONCLUSIONS: The present study demonstrates the feasibility of using CEUS as a noninvasive, nonionizing imaging modality in estimating BAT blood flow in young, healthy humans. CEUS may be a useful and scalable tool in the assessment of BAT and BAT-targeted therapies.

Functional brown adipose tissue limits cardiomyocyte injury and adverse remodeling in catecholamine-induced cardiomyopathy.

Brown adipose tissue (BAT) has well recognized thermogenic properties mediated by uncoupling protein 1 (UCP1); more recently, BAT has been demonstrated to modulate cardiovascular risk factors. To investigate whether BAT also affects myocardial injury and remodeling, UCP1-deficient (UCP1(-/-)) mice, which have dysfunctional BAT, were subjected to catecholamine-induced cardiomyopathy. At baseline, there were no differences in echocardiographic parameters, plasma cardiac troponin I (cTnI) or myocardial fibrosis between wild-type (WT) and UCP1(-/-) mice. Isoproterenol infusion increased cTnI and myocardial fibrosis and induced left ventricular (LV) hypertrophy in both WT and UCP1(-/-) mice. UCP1(-/-) mice also demonstrated exaggerated myocardial injury, fibrosis, and adverse remodeling, as well as decreased survival. Transplantation of WT BAT to UCP1(-/-) mice prevented the isoproterenol-induced cTnI increase and improved survival, whereas UCP1(-/-) BAT transplanted to either UCP1(-/-) or WT mice had no effect on cTnI release. After 3 days of isoproterenol treatment, phosphorylated AKT and ERK were lower in the LV's of UCP1(-/-) mice than in those of WT mice. Activation of BAT was also noted in a model of chronic ischemic cardiomyopathy, and was correlated to LV dysfunction. Deficiency in UCP1, and accompanying BAT dysfunction, increases cardiomyocyte injury and adverse LV remodeling, and decreases survival in a mouse model of catecholamine-induced cardiomyopathy. Myocardial injury and decreased survival are rescued by transplantation of functional BAT to UCP1(-/-) mice, suggesting a systemic cardioprotective role of functional BAT. BAT is also activated in chronic ischemic cardiomyopathy.

Interpreting the interpretations: the use of structured reporting improves referring clinicians' comprehension of coronary CT angiography reports.

BACKGROUND: Efficiency of coronary CT angiography (CCTA) in clinical practice depends on precise reporting and accurate result interpretation. OBJECTIVE: We sought to assess referring clinicians' understanding of patients' coronary artery disease (CAD) severity and to compare satisfactions of the free-form impression (FFI) with satisfactions of the structured impression (SI) section of CCTA reports. MATERIALS AND METHODS: Fifty clinical CCTA reports from May 2011 to April 2012 were retrospectively selected (25 FFI and 25 SI), to include cases with the entire spectrum of CAD (6 categories encompassing normal, minimal, mild, moderate, severe stenosis, and occlusion). A survey containing only randomized blinded impressions was distributed to 4 cardiologists and 2 cardiac imaging specialists. Clinician interpretation was examined regarding (Q1) worst stenosis severity, (Q2) number of vessels with significant stenosis, and (Q3) the presence of nonevaluable segments. Agreement proportions and Cohen's kappa were evaluated between FFI versus SI. Satisfactions were measured with respect to content, clarity, and clinical effectiveness. RESULTS: Q1 agreement was excellent for both FFI and SI (by 6 categories: 80% versus 85%; P > .05; kappa: 0.87 versus 0.89; by no CAD versus nonsignificant versus significant CAD: 99% versus 97%; P > .05; kappa: 0.99 versus 0.94). Q2 agreement improved from fair to moderate (53% versus 68%; P = .04; kappa 0.31 versus 0.52). Q3 agreement was moderate (90% versus 87%; P > .05; kappa 0.57 versus 0.58). Satisfactions with impressions were high and similar for FFI and SI for clinicians. CONCLUSION: Structured impressions were shown to improve result interpretation agreement from fair to moderate with regard to the number of vessels with significant stenosis.

Abnormal function and glucose metabolism in the type-2 diabetic db/db mouse heart.

This study examined cardiac function and glucose metabolism in the 6-month-old db/db mouse, a model of type-2 diabetes. Cine magnetic resonance spectroscopy (MRI) was used to measure cardiac function in vivo. The db/db mice had decreased heart rates (17%, p<0.01) and stroke volumes (21%, p<0.05) that resulted in lower cardiac output (35%, p<0.01) than controls. Although there was no difference in ejection fraction between the 2 groups, db/db mouse hearts had a 35% lower maximum rate of ejection (p<0.01) than controls. In a protocol designed to assess maximal insulin-independent glucose uptake, hearts were isolated and perfused in Langendorff mode and subjected to 0.75 mL.min(-1).(g wet mass)(-1) low flow ischemia for 32 min. Glucose uptake during ischemia was 21% lower than in controls, and post-ischemic recovery of cardiac function was decreased by 30% in db/db mouse hearts (p<0.05). Total cardiac GLUT 4 protein was 56% lower (p<0.01) in db/db mice than in controls. In summary, the db/db mouse has abnormal left ventricular function in vivo, with impaired glucose uptake during ischemia, leading to increased myocardial damage.

Plasma free fatty acids and peroxisome proliferator-activated receptor alpha in the control of myocardial uncoupling protein levels.

Diabetic patients have abnormal cardiac energy metabolism associated with high plasma free fatty acid (FFA) concentrations. We investigated whether high plasma FFAs increase mitochondrial uncoupling protein (UCP) levels in the mouse heart by activating the nuclear transcription factor peroxisome proliferator-activated receptor (PPAR)alpha. We used Western blotting to measure UCP protein levels in isolated cardiac mitochondria from PPARalpha-/- and diabetic mice. Cardiac UCP2 and UCP3 were significantly lower in the PPARalpha-/- mouse than in the wild type. Treatment with the PPARalpha-specific agonist, WY-14,643, increased cardiac UCP2 and UCP3 levels in wild-type mice but did not alter UCP levels in PPARalpha-/- mice. Inhibition of beta-oxidation with etomoxir increased cardiac UCP2 and UCP3 levels in wild-type mice and UCP2 levels in PPARalpha-/- mice but did not alter UCP3 levels in PPARalpha-/- mice. Streptozotocin treatment, which increased circulating FFAs by 91%, did not alter cardiac UCP2 levels in wild-type or PPARalpha-/- mice but increased UCP3 levels in wild-type, and not in PPARalpha-/-, mice. The diabetic db/db mouse had 50% higher plasma FFA concentrations and elevated cardiac UCP2 and UCP3 protein levels. We conclude that high plasma FFAs activated PPARalpha to increase cardiac UCP3 levels, but cardiac UCP2 levels changed via PPARalpha-dependent and -independent mechanisms.

PPAR-alpha activation required for decreased glucose uptake and increased susceptibility to injury during ischemia.

The transcription of key metabolic regulatory enzymes in the heart is altered in the diabetic state, yet little is known of the underlying mechanisms. The aim of this study was to investigate the role of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) in modulating cardiac insulin-sensitive glucose transporter (GLUT-4) protein levels in altered metabolic states and to determine the functional consequences by assessing cardiac ischemic tolerance. Wild-type and PPAR-alpha-null mouse hearts were isolated and perfused 6 wk after streptozotocin administration or after 14 mo on a high-fat diet or after a 24-h fast. Myocardial d-[2-(3)H]glucose uptake was measured during low-flow ischemia, and differences in GLUT-4 protein levels were quantified using Western blotting. In wild-type mice in all three metabolic states, elevated plasma free fatty acids were associated with lower total cardiac GLUT-4 protein levels and decreased glucose uptake during ischemia, resulting in poor postischemic functional recovery. Although PPAR-alpha-null mice also had elevated plasma free fatty acids, they had neither decreased cardiac GLUT-4 levels nor decreased glucose uptake during ischemia and, consequently, did not have poor recovery during reperfusion. We conclude that elevated plasma free fatty acids are associated with increased injury during ischemia due to decreased cardiac glucose uptake resulting from lower cardiac GLUT-4 protein levels, the levels of GLUT-4 being regulated, probably indirectly, through PPAR-alpha activation.