Cardiovascular disease burden attributable to dietary risk factors from 1990 to 2019: A systematic analysis of the Global Burden of Disease study.

BACKGROUND AND AIMS: Dietary risks have always been a major risk factor for cardiovascular diseases (CVDs), especially in young people. This article aimed to provide an updated and comprehensive view of the spatial, temporal and sexual heterogeneity in diet-attributable CVD burdens from 1990 to 2019. METHODS AND RESULTS: Data on diet-attributable CVD burdens were extracted from the Global Burden of Disease (GBD) Study 2019. Numbers and age-standardized rates (ASRs) of deaths, disability-adjusted life years (DALYs) and corresponding estimated annual percentage change (EAPC) were determined. Globally, the number of diet-attributable CVD deaths and DALYs in 2019 were 6.9 million and 153.2 million, marking 43.8% and 34.3% increases since 1990, respectively. However, ASRs of death and DALYs have declined over time. The regions with the highest ASRs of diet-related CVD deaths and DALYs were in Central Asia, whereas the lowest ASRs of CVD deaths and DALYs were observed in the high-income Asia Pacific region. Globally, men suffered higher death and DALY burdens than women. Ischemic heart disease and stroke were the leading causes of CVD deaths and DALYs, globally. Regarding the specific diet group, diets low in whole grains, high in sodium, low in fruits, low in nuts and seeds, low in vegetables and low in seafood omega-3 fatty acids contributed to CVD deaths and DALYs the most. Dietary risks accounted for a higher proportion in people aged less than 65 years old. CONCLUSIONS: Diet-attributable CVDs threaten public health, particularly in low SDI countries and younger generations. As diet-related CVDs are nation-specific, the prioritization of public health interventions should be evidence-based.

Application of topic models to a compendium of ChIP-Seq datasets uncovers recurrent transcriptional regulatory modules.

MOTIVATION: The availability of thousands of genome-wide coupling chromatin immunoprecipitation (ChIP)-Seq datasets across hundreds of transcription factors (TFs) and cell lines provides an unprecedented opportunity to jointly analyze large-scale TF-binding in vivo, making possible the discovery of the potential interaction and cooperation among different TFs. The interacted and cooperated TFs can potentially form a transcriptional regulatory module (TRM) (e.g. co-binding TFs), which helps decipher the combinatorial regulatory mechanisms. RESULTS: We develop a computational method tfLDA to apply state-of-the-art topic models to multiple ChIP-Seq datasets to decipher the combinatorial binding events of multiple TFs. tfLDA is able to learn high-order combinatorial binding patterns of TFs from multiple ChIP-Seq profiles, interpret and visualize the combinatorial patterns. We apply the tfLDA to two cell lines with a rich collection of TFs and identify combinatorial binding patterns that show well-known TRMs and related TF co-binding events. AVAILABILITY AND IMPLEMENTATION: A software R package tfLDA is freely available at https://github.com/lichen-lab/tfLDA. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Exendin-4 regulates endoplasmic reticulum stress to protect endothelial progenitor cells from high-glucose damage.

BACKGROUND: High glucose affects the function of endothelial cells by increasing oxidative stress. Studies have found that exendin-4 can improve wound healing in diabetic mice and mice with normal blood glucose. However, the mechanism of exendin-4 in endothelial progenitor cells under high-glucose condition has not been fully elucidated. METHODS: Diabetic mouse models were established to investigate the effects of exendin-4 on endothelial progenitor cells in diabetic mice. Serum superoxide dismutase (SOD) and malondialdehyde (MDA) were determined by WST-8 and thiobarbituric acid (TBA) colorimetry, respectively. Cell viability, apoptosis and reactive oxygen species (ROS) were detected by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and flow cytometry. Gene and protein expressions were determined by Quantitative reverse transcription PCR (qRT-PCR) assay and Western blot (WB). RESULTS: The results showed that in diabetic mice, exendin-4 did not affect blood glucose or body weight, moreover, it improved aortic diastolic function, increased SOD activity and down-regulated malondialdehyde (MDA) level in the mice. In addition, exendin-4 also increased endothelial progenitor cell (EPCs) viability and reduced cell apoptosis through inhibiting p38 MAPK pathway and reducing endoplasmic reticulum stress and ROS. CONCLUSION: Exndin-4 can alleviate diabetes-caused damage to mice, moreover, it reduced endoplasmic reticulum stress and ROS through inhibiting p38 MAPK pathway in MPCs cells under high-glucose condition, thus increasing cell viability and reducing cell apoptosis.

Takotsubo cardiomyopathy and pituitary apoplexy: a case report.

BACKGROUND: Takotsubo cardiomyopathy (TTC) has been widely recognized in recent decades and is triggered by either physical or psychological stressors. CASE PRESENTATION: A 70-year-old woman presented to the Emergency Department due to confusion, hypotension, fever, chills, and cough. She had a one-year history of diabetes insipidus. Pituitary function examination at admission revealed decreased thyroid, sex and adrenal hormones. Pituitary MRI displayed findings suggestive of nonhemorrhagic pituitary apoplexy. Electrocardiogram (ECG) revealed T-wave inversion and extended QT interval. Transthoracic echocardiogram (TTE) showed left ventricular apical dysplasia and ballooning, accompanied by reduced left ventricular ejection fraction. Coronary angiography (CAG) revealed no obvious coronary arterial stenosis. The left ventriculogram demonstrated an octopus clathrate appearance. Most ECG and TTE changes recovered 10 days later. CONCLUSIONS: To the best of our knowledge, this is the first report of newly diagnosed TTC associated with pituitary apoplexy.

Cardiac rupture complicating acute myocardial infarction: the clinical features from an observational study and animal experiment.

BACKGROUND: Cardiac rupture (CR) is a fatal complication of ST-elevation myocardial infarction (STEMI) with its incidence markedly declined in the recent decades. However, clinical features of CR patients now and the effect of reperfusion therapy to CR remain unclear. We investigated the clinical features of CR in STEMI patients and the effect of reperfusion therapy to CR in mice. METHODS: Two studies were conducted. In clinical study, data of 1456 STEMI patients admitted to the First Hospital, Xi'an Jiaotong University during 2015.12. ~ 2018.12. were analyzed. In experimental study, 83 male C57BL/6 mice were operated to induce MI. Of them, 39 mice were permanent MI (group-1), and remaining mice received reperfusion after 1 h ischemia (21 mice, group-2) or 4 h ischemia (23 mice, group-3). All operated mice were monitored up to day-10. Animals were inspected three times daily for the incidence of death and autopsy was done for all mice found died to determine the cause of death. RESULTS: CR was diagnosed in 40 patients: free-wall rupture in 17, ventricular septal rupture in 20, and combined locations in 3 cases. CR presented in 19 patients at admission and diagnosed in another 21 patients during 1 ~ 14 days post-STEMI, giving an in-hospital incidence of 1.4%. The mortality of CR patients was high during hospitalization accounting for 39% of total in-hospital death. By multivariate logistic regression analysis, older age, peak CK-MB and peak hs-CRP were independent predictors of CR post-STEMI. In mice with non-reperfused MI, 17 animals (43.6%) died of CR that occurred during 3-6 days post-MI. In MI mice received early or delayed reperfusion, all mice survived to the end of experiment except one mouse died of acute heart failure. CONCLUSION: CR remains as a major cause of in-hospital death in STEMI patients. CR patients are characterized of being elderly, having larger infarct and more server inflammation. Experimentally, reperfusion post-MI prevented CR.

Correction to: Cardiac rupture complicating acute myocardial infarction: the clinical features from an observational study and animal experiment.

An amendment to this paper has been published and can be accessed via the original article.

U-shaped association between plasma sphingosine-1-phosphate levels and mortality in patients with chronic systolic heart failure: a prospective cohort study.

BACKGROUND: The endogenous lipid molecule sphingosine-1-phosphate (S1P) has received attention in the cardiovascular field due to its significant cardioprotective effects, as revealed in animal studies. The purpose of our study was to identify the distribution characteristics of S1P in systolic heart failure patients and the prognostic value of S1P for long-term prognosis. METHODS: We recruited 210 chronic systolic heart failure patients from June 2014 to December 2015. Meanwhile 54 healthy people in the same area were selected as controls. Plasma S1P was measured by liquid chromatography-tandem mass spectrometry. Patients were grouped according to the baseline S1P level quartiles, and restricted cubic spline plots described the association between S1P and all-cause death. Cox proportional hazard analysis was used to determine the relationship between category of S1P and all-cause death. RESULTS: Compared with the control group, the plasma S1P in chronic heart failure patients demonstrated a higher mean level (1.269 µmol/L vs 1.122 µmol/L, P = 0.006) and a larger standard deviation (0.441 vs 0.316, P = 0.022). Based on multivariable Cox regression with restricted cubic spline analysis, a non-linear and U-shaped association between S1P levels and the risk of all-cause death was observed. After a follow-up period of 31.7 ± 10.3 months, the second quartile (0.967-1.192 µml/L) with largely normal S1P levels had the lowest all-cause mortality and either an increase (adjusted HR = 2.368, 95%CI 1.006-5.572, P = 0.048) or a decrease (adjusted HR = 0.041, 95%CI 0.002-0.808, P = 0.036) predicted a worse prognosis. The survival curves showed that patients in the lowest quartile and highest quartile were at a higher risk of death. CONCLUSIONS: Plasma S1P levels in systolic heart failure patients are related to the long-term all-cause mortality with a U-shaped correlation. TRIAL REGISTRATION: CHiCTR, ChiCTR-ONC-14004463. Registered 20 March 2014.

Subclinical thyroid dysfunction is associated with adverse prognosis in heart failure patients with reduced ejection fraction.

BACKGROUND: Subclinical thyroid dysfunction whose typical patterns include subclinical hypothyroidism and subclinical hyperthyroidism, has been indicated to be associated with an increased risk of heart failure (HF). However, the relationship between subclinical thyroid dysfunction and the clinical outcomes of HF patients is uncertain. This meta-analysis was conducted to assess the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients. METHODS: Pubmed, Embase, Web of Science and Cochrane Central Register of Clinical Trials were searched for eligible studies published up to August 1, 2018 which reported the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients. The pooled hazard ratio (HR) with the corresponding 95% confidence interval (CI) was used to assess the association. RESULTS: Fourteen studies met the eligibility criteria and a total of 21,221 patients with heart failure were included in the meta-analysis. Compared with HF patients with euthyroidism, the pooled HR of subclinical hypothyroidism for all-cause mortality was 1.45 (95% CI 1.26-1.67) in a randomized effects model with mild heterogeneity (I2 = 40.1, P = 0.073). The pooled HR of subclinical hypothyroidism for cardiac death and/or hospitalization was 1.33 (1.17-1.50) in a randomized effects model with moderate heterogeneity (I2 = 69.4, P < 0.001). Subclinical hyperthyroid can increase the risk of all-cause mortality without heterogeneity (HR 1.31, 95% CI 1.10-1.55, I2 = 25.5%, P = 0.225) but have no influence on the risk of cardiac death and/or hospitalization (HR 1.03, 95% CI 0.87-1.23, I2 = 0.0%, P = 0.958). These significant adverse associations were also retained in subgroup analysis. Sensitivity analysis demonstrated the stability of the results of our meta-analysis. CONCLUSIONS: Both subclinical hypothyroidism and subclinical hyperthyroidism are associated with adverse prognosis in patients with HF. Subclinical thyroid dysfunction may be a useful and promising predictor for the long-term prognosis in HF patients.

Lack of influence of sex hormones on Brugada syndrome-associated mutant Nav1.5 sodium channel.

Brugada syndrome (BS) is an autosomal dominant disease. The most common causes of BS are loss-of-function mutations occur in the SCN5A gene which encodes the sodium channel protein Nav1.5. BS has a higher incidence rate in males and the underlying mechanisms of the gender inequality are not yet fully understood. Considering sex hormones are among the most important factors behind gender differences and have previously been shown to regulate the activity of multiple cardiac ion channels, we hypothesized that sex hormones also affect Nav1.5 function which lead to BS predominantly affecting males. In this study, we investigate the protein expression level and current of Nav1.5 in the HEK293 cells cotransfected with SCN5A and sex hormone receptor plasmids using both wild-type SCN5A and BS-associated SCN5A channel mutants R878C and R104W. Our findings showed that sex hormones have no effects on the protein expression level and current of the wild-type Nav1.5, neither does it affect the protein expression level and current of BS-associated Nav1.5 mutants R878C and R104W, regardless of homozygous or heterozygous state. Our results suggest that the male preponderance of BS does not arise from the effects of the sex hormones on Nav1.5. Further studies are needed to explain the male preponderance of this disease.

MYH7 Gene-Related Mutation p.V878L Identified in a Chinese Family with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiovascular diseases and possesses a high risk for sudden cardiac death. Although mutations in more than 20 genes have been reported to be associated with HCM thus far, the genetic backgrounds of most HCM patients are not fully understood. We performed a genetic analysis in a Chinese family that presented with HCM using next-generation sequencing (NGS). Clinical data, family histories, and blood samples were collected from the proband and family members. Five patients showed typical clinical symptoms of HCM. One subject was the victim of sudden cardiac death. By NGS, we determined that these subjects with HCM symptoms carried a missense heterozygous genetic mutation c.2632C>A (p.V878L) in the myosin heavy chain 7 (MYH7) gene with an autosomal dominant pattern of inheritance. Individuals without this mutation showed no symptoms or cardiac structural abnormalities related to HCM. Bioinformatics evaluation predicted this mutant as "damaging" and "disease causing". Additionally, sequence alignment showed that this mutant is located in an evolutionarily conserved region of MYH7 in multiple species. Our results describe a potentially pathogenic mutation associated with HCM, which may extend the spectrum of HCM phenotypes related to MYH7 gene mutations.

Heterogeneity of transverse-axial tubule system in mouse atria: Remodeling in atrial-specific Na+-Ca2+ exchanger knockout mice.

Transverse-axial tubules (TATs) are commonly assumed to be sparse or absent in atrial myocytes from small animals. Atrial myocytes from rats, cats and rabbits lack TATs, which results in a characteristic "V"-shaped Ca release pattern in confocal line-scan recordings due to the delayed rise of Ca in the center of the cell. To examine TAT expression in isolated mouse atrial myocytes, we loaded them with the membrane dye Di-4-ANEPPS to label TATs. We found that >80% of atrial myocytes had identifiable TATs. Atria from male mice had a higher TAT density than female mice, and TAT density correlated with cell width. Using the fluorescent Ca indicator Fluo-4-AM and confocal imaging, we found that wild type (WT) mouse atrial myocytes generate near-synchronous Ca transients, in contrast to the "V"-shaped pattern typically reported in other small animals such as rat. In atrial-specific Na-Ca exchanger (NCX) knockout (KO) mice, which develop sinus node dysfunction and atrial hypertrophy with dilation, we found a substantial loss of atrial TATs in isolated atrial myocytes. There was a greater loss of transverse tubules compared to axial tubules, resulting in a dominance of axial tubules. Consistent with the overall loss of TATs, NCX KO atrial myocytes displayed a "V"-shaped Ca transient with slower and reduced central (CT) Ca release and uptake in comparison to subsarcolemmal (SS) Ca release. We compared chemically detubulated (DT) WT cells to KO, and found similar slowing of CT Ca release and uptake. However, SS Ca transients in the WT DT cells had faster uptake kinetics than KO cells, consistent with the presence of NCX and normal sarcolemmal Ca efflux in the WT DT cells. We conclude that the remodeling of NCX KO atrial myocytes is accompanied by a loss of TATs leading to abnormal Ca release and uptake that could impact atrial contractility and rhythm.

Resistin may be an independent predictor of subclinical atherosclerosis formale smokers.

To investigate whether resistin is associated with early atherosclerosis in male smokers. The present study consecutively enrolled 50 male smokers. Their serum resistin contents were detected with enzyme linked immunosorbent assay (ELISA), and subclinical atherosclerosis indices, including carotid inner middle thickness (IMT) and arterial elasticity indices (C1 and C2), were measured. The association between serum resistin levels and IMT, C1 and C2 were respectively evaluated with the Pearson's correlation coefficient method. The results showed that the serum resistin level had a positive association with IMT (r = 0.307, p = .030), but were both inversely associated with C1 (r = -0.440, p = .001) and C2 (r = -0.381, p = .006). These associations remained significant even after adjustment for cardiovascular confounders. In conclusion, serum resistin concentration was independently associated with early atherosclerosis in male smokers.

Admission hyperglycemia and adverse outcomes in diabetic and non-diabetic patients with non-ST-elevation myocardial infarction undergoing percutaneous coronary intervention.

BACKGROUND: The association between admission hyperglycemia and adverse outcomes in patients with non-ST-segment elevation myocardial infarction (NSTEMI) undergoing percutaneous coronary intervention (PCI) has not been well studied, and the optimal plasma glucose cut-off values for prognosis for NSTEMI patients with and without diabetes have not been determined. METHODS: According to glucose level and diabetes status, consecutive NSTEMI patients undergoing PCI (n = 890) were divided into four groups: without diabetes mellitus (DM) and admission plasma glucose (APG) <144 or ≥144 mg/dL; or with DM and APG <180 or ≥180 mg/dL. All patients were followed up at 30 days and 3 years after discharge, and the outcomes were assessed. RESULTS: Admission hyperglycemia was found in 44 and 28% of the DM and non-DM patients, respectively. Multivariable analyses showed that the APG level was an independent predictor of 30-day and 3-year MACEs. Receiver operating characteristic curve analysis revealed that the appropriate cut-off values were 178 and 145 mg/dL for patients with and without DM, respectively, or 157 mg/dL for all patients. CONCLUSIONS: Admission hyperglycemia may be used to predict 30-day and 3-year MACEs in patients with NSTEMI undergoing PCI, irrespective of diabetes status. However, the optimal admission glucose cut-off values for predicting prognosis differ for patients with or without DM.

Reduced expression of HCN channels in the sinoatrial node of streptozotocin-induced diabetic rats.

Diabetes mellitus (DM) is associated with an electrical remodeling of the heart, increasing the risk of arrhythmias. However, knowledge of electrical remodeling in the sinoatrial node (SAN) by DM is limited. We investigated the expression of HCN channel isoforms, HCN1-HCN4, in SAN from streptozotocin (STZ)-induced diabetic rats and the age-matched controls. We found that the STZ-induced diabetic rats have a lower intrinsic heart rate, a lengthened sinoatrial conduction time, and rate-corrected maximal sinoatrial node recovery time in vivo as well as a longer cycle length (CL) in vitro, as compared with the control. Optical mapping of the SAN demonstrated an inferior leading pacemaker site, reduced SAN conduction velocity and diastolic depolarization slope, and a longer action potential duration in the STZ-induced diabetic rats than in the control. The transcripts and proteins of HCN2 and HCN4 in diabetic SAN were reduced. Specific blockade of HCN channels by 3 µmol/L ivabradine significantly prolonged the CL of a Langendorff heart by 18% in the diabetic rats and 26% in the control. The reduced expression of HCN channel isoforms in the SAN of the STZ-induced diabetic rat may be an important contributor to the reduced SAN function in DM.

NS1643 enhances ionic currents in a G604S-WT hERG co-expression system associated with long QT syndrome 2.

Loss of function mutations in the human ether-a-go-go-related gene (hERG) cause long QT syndrome type 2 (LQT2). Most LQT2 patients are heterozygous mutation carriers in which the mutant hERG exerts potent dominant-negative effects. 1, 3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea (NS1643) is known to enhance IKr in WT-hERG. We investigated its actions following lipofectamine-induced expression of both mutant G604S- and WT-hERG in the heterologous HEK293 expression system. Cells transfected with pcDNA3-G604S-hERG did not lead to any expression of detectable currents whether before or following NS1643 challenge. Cells transfected with both pcDNA3-WT-hERG and pcDNA3-G604S-hERG showed reduced hERG currents compared to those transfected with pcDNA3-G604S-hERG consistent with the reduced trafficking and formation of modified heteromeric WT-G604S channels reported on earlier occasions. Nevertheless, NS1643 then continued to produce concentration- and voltage-dependent increases in hERG current amplitude. It did not affect the voltage dependence of activation, recovery from inactivation and deactivation. However, NS1643 (30 µmol/L) slowed steady state inactivation and shifted the steady state half maximal activation voltage (V1/2 ) of the inactivation curve by +10 mV, and significantly increased the time constants of inactivation. Our present experimental results suggest that NS1643 significantly increases ion current and attenuates its inactivation in cells co-expressing G604S-hERG and WT-hERG. These findings raise the possibility that hERG channel activators offer potential treatment strategies for inherited LQT2.

Ultra-high pressure liquid chromatography-tandem mass spectrometry method for the determination of omarigliptin in rat plasma and its application to a pharmacokinetic study in rats.

Omarigliptin is a novel long-acting dipeptidyl peptidase-4 inhibitor used for the treatment of type 2 diabetes. In this work, a sensitive and selective ultra-high pressure liquid chromatography tandem mass spectrometry method was developed and validated for the determination of omarigliptin in rat plasma. Sample preparation was performed by protein precipitation with acetonitrile. Chromatographic separation of analytes was achieved on an RRHD Eclipse Plus C18 column (2.1 × 50 mm, 1.8 µm), using gradient mobile phase (0.1% formic acid-acetonitrile) at a flow rate of 0.4 mL/min. Detection was performed in multiple reaction monitoring mode, with target fragment ions m/z 399.1 → 152.9 for omarigliptin and m/z 237.1 → 194 for the internal standard. The total run time was 4 min. Retention time of omarigliptin and internal standard was 1.25 and 2.12 min, respectively. Relative standard deviation (%) of the intra- and inter-day precision was below 10.0%, and accuracy was between 97.9% and 105.3%. Calibration curve was established over the range 2-5000 ng/mL with good linearity. The lower limit of quantification and limit of detection of omarigliptin were 2 and 0.25 ng/mL, respectively. Mean recoveries were in the range 87.3-95.1% for omarigliptin. No matrix effect was observed in this method. This novel method has been successfully applied to a pharmacokinetic study of omarigliptin in rats. The absolute bioavailability of omarigliptin was identified as high as 87.31%.

Clenbuterol Attenuates hERG Channel by Promoting the Mature Channel Degradation.

Clenbuterol, a ß2-selective adrenergic receptor agonist, is illicitly used in weight loss and performance enhancement and animal production. Increasing evidence demonstrates that clenbuterol induces various kinds of arrhythmias and QTc interval prolongation. However, little is known about the underlying mechanism. Most drugs are associated with QTc prolongation through interfering with human ether-a-go-go-related gene (hERG) K+ channels. The present study aims to investigate the effects and underlying mechanisms of clenbuterol on the hERG channel. HEK 293 cells were transfected with wild type and Y652A or F656A mutants of the hERG channel and treated with clenbuterol. The hERG current was recorded using whole-cell patch-clamp technique, and protein level was evaluated by Western blot. We found that clenbuterol decreases the mature form of the hERG protein at the cell membrane in a concentration- and time-dependent manner, without affecting the immature form. Correspondingly, clenbuterol chronic treatment reduced hERG current to a greater extent compared to acute treatment. In the presence of Brefeldin A (BFA), which was used to block hERG channel trafficking to cell membrane, clenbuterol reduced hERG on plasma membrane to a greater extent than BFA alone. In addition, the hERG channel's drug binding sites mutant Y652A and F656A abolished clenbuterol-mediated hERG reduction and current blockade. In conclusion, clenbuterol reduces hERG channel expression and current by promoting the channel degradation. The effect of clenbuterol on the hERG channel is related to the drug-binding sites, Tyr-652 and Phe-656, located on the S6 domain. This biophysical mechanism may underlie clenbuterol-induced QTc prolongation or arrhythmia.

Antioxidant catalase rescues against high fat diet-induced cardiac dysfunction via an IKKß-AMPK-dependent regulation of autophagy.

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a variety of biological processes including obesity. However, the precise mechanism of action behind obesity-induced changes in autophagy still remains elusive. This study was designed to examine the role of the antioxidant catalase in high fat diet-induced changes in cardiac geometry and function as well as the underlying mechanism of action involved with a focus on autophagy. Wild-type (WT) and transgenic mice with cardiac overexpression of catalase were fed low or high fat diet for 20 weeks prior to assessment of myocardial geometry and function. High fat diet intake triggered obesity, hyperinsulinemia, and hypertriglyceridemia, the effects of which were unaffected by catalase transgene. Myocardial geometry and function were compromised with fat diet intake as manifested by cardiac hypertrophy, enlarged left ventricular end systolic and diastolic diameters, fractional shortening, cardiomyocyte contractile capacity and intracellular Ca²âº mishandling, the effects of which were ameliorated by catalase. High fat diet intake promoted reactive oxygen species production and suppressed autophagy in the heart, the effects of which were attenuated by catalase. High fat diet intake dampened phosphorylation of inhibitor kappa B kinase ß(IKKß), AMP-activated protein kinase (AMPK) and tuberous sclerosis 2 (TSC2) while promoting phosphorylation of mTOR, the effects of which were ablated by catalase. In vitro study revealed that palmitic acid compromised cardiomyocyte autophagy and contractile function in a manner reminiscent of fat diet intake, the effect of which was significantly alleviated by inhibition of IKKß, activation of AMPK and induction of autophagy. Taken together, our data revealed that the antioxidant catalase counteracts against high fat diet-induced cardiac geometric and functional anomalies possibly via an IKKß-AMPK-dependent restoration of myocardial autophagy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

The RyR2-P2328S mutation downregulates Nav1.5 producing arrhythmic substrate in murine ventricles.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) predisposes to ventricular arrhythmia due to altered Ca(2+) homeostasis and can arise from ryanodine receptor (RyR2) mutations including RyR2-P2328S. Previous reports established that homozygotic murine RyR2-P2328S (RyR2 (S/S)) hearts show an atrial arrhythmic phenotype associated with reduced action potential (AP) conduction velocity and sodium channel (Nav1.5) expression. We now relate ventricular arrhythmogenicity and slowed AP conduction in RyR2 (S/S) hearts to connexin-43 (Cx43) and Nav1.5 expression and Na(+) current (I Na). Stimulation protocols applying extrasystolic S2 stimulation following 8 Hz S1 pacing at progressively decremented S1S2 intervals confirmed an arrhythmic tendency despite unchanged ventricular effective refractory periods (VERPs) in Langendorff-perfused RyR2 (S/S) hearts. Dynamic pacing imposing S1 stimuli then demonstrated that progressive reductions of basic cycle lengths (BCLs) produced greater reductions in conduction velocity at equivalent BCLs and diastolic intervals in RyR2 (S/S) than WT, but comparable changes in AP durations (APD90) and their alternans. Western blot analyses demonstrated that Cx43 protein expression in whole ventricles was similar, but Nav1.5 expression in both whole tissue and membrane fractions were significantly reduced in RyR2 (S/S) compared to wild-type (WT). Loose patch-clamp studies similarly demonstrated reduced I Na in RyR2 (S/S) ventricles. We thus attribute arrhythmogenesis in RyR2 (S/S) ventricles resulting from arrhythmic substrate produced by reduced conduction velocity to downregulated Nav1.5 reducing I Na, despite normal determinants of repolarization and passive conduction. The measured changes were quantitatively compatible with earlier predictions of linear relationships between conduction velocity and the peak I Na of the AP but nonlinear relationships between peak I Na and maximum Na(+) permeability.

Lin28a protects against postinfarction myocardial remodeling and dysfunction through Sirt1 activation and autophagy enhancement.

BACKGROUND: Myocardial remodeling and cardiac dysfunction prevention may represent a therapeutic approach to reduce mortality in patients with myocardial infarction (MI). We investigated the effects of Lin28a in experimental MI models, as well as the mechanisms underlying these effects. METHODS: Left anterior descending (LAD) coronary artery ligation was used to construct an MI-induced injury model. Neonatal cardiomyocytes were isolated and cultured to investigate the mechanisms underlying the protective effects of Lin28a against MI-induced injury. RESULTS: Lin28a significantly inhibited left ventricular remodeling and cardiac dysfunction after MI, as demonstrated via echocardiography and hemodynamic measurements. Lin28a reduced cardiac enzyme and inflammatory marker release in mice subjected to MI-induced injury. The mechanisms underlying the protective effects of Lin28a against MI-induced injury were associated with autophagy enhancements and apoptosis inhibition. Consistent with these findings, Lin28a knockdown aggravated cardiac remodeling and dysfunction after MI-induced injury. Lin28a knockdown also inhibited cardiomyocyte autophagy and increased cardiomyocyte apoptosis in mice subjected to MI-induced injury. Interestingly, Sirt1 knockdown abolished the protective effects of Lin28a against cardiac remodeling and dysfunction after MI, and Lin28a failed to increase the numbers of GFP-LC3-positive punctae and decrease aggresome and p62 accumulation in Sirt1-knockdown neonatal cardiomyocytes subjected to hypoxia-induced injury. CONCLUSIONS: Lin28a inhibits cardiac remodeling, improves cardiac function, and reduces cardiac enzyme and inflammatory marker release after MI. Lin28a also up-regulates cardiomyocyte autophagy and inhibits cardiomyocyte apoptosis through Sirt1 activation.