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Metformin is the first-line medication for treatment of type 2 diabetes and has been shown to reduce heart damage and death. However, mechanisms by which metformin protects human heart remain debated. The aim of the study was to evaluate the cardioprotective effect of metformin on cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) and mitochondria isolated from human cardiac tissue. At concentrations ≤2.5 mM, metformin significantly increased oxygen consumption rate (OCR) in the hiPSC-CMs by activating adenosine monophosphate activated protein kinase (AMPK)-dependent signaling and enhancing mitochondrial biogenesis. This effect was abrogated by compound C, an inhibitor of AMPK. At concentrations >5 mM, metformin inhibited the cellular OCR and triggered metabolic reprogramming by enhancing glycolysis and glutaminolysis in the cardiomyocytes. In isolated cardiac mitochondria, metformin did not increase the OCR at any concentrations but inhibited the OCR starting at 1 mM through direct inhibition of electron-transport chain complex I. This was associated with reduction of superoxide production and attenuation of Ca2+-induced mitochondrial permeability transition pore (mPTP) opening in the mitochondria. Thus, in human heart, metformin might improve cardioprotection due to its biphasic effect on mitochondria: at low concentrations, it activates mitochondrial biogenesis via AMPK signaling and increases the OCR; at high concentrations, it inhibits the respiration by directly affecting the activity of complex I, reduces oxidative stress and delays mPTP formation. Moreover, metformin at high concentrations causes metabolic reprogramming by enhancing glycolysis and glutaminolysis. These effects can be a beneficial adjunct to patients with impaired endogenous cardioprotective responses.

Background Age‐related heart diseases are significant contributors to increased morbidity and mortality. Emerging evidence indicates that mitochondria within cardiomyocytes contribute to age‐related increased reactive oxygen species (ROS) generation that plays an essential role in aging‐associated cardiac diseases. Methods and Results The present study investigated differences between ROS production in cardiomyocytes isolated from adult (6 months) and aged (24 months) Fischer 344 rats, and in cardiac tissue of adult (18–65 years) and elderly (>65 years) patients with preserved cardiac function. Superoxide dismutase inhibitable ferricytochrome c reduction assay (1.32±0.63 versus 0.76±0.31 nMol/mg per minute; P =0.001) superoxide and H 2 O 2 production, measured as dichlorofluorescein diacetate fluorescence (1646±428 versus 699±329, P =0.04), were significantly higher in the aged versus adult cardiomyocytes. Similarity in age‐related alteration between rats and humans was identified in mitochondrial‐electron transport chain‐complex‐I‐associated increased oxidative‐stress by MitoSOX fluorescence (53.66±18.58 versus 22.81±12.60; P =0.03) and in 4‐HNE adduct levels (187.54±54.8 versus 47.83±16.7 ng/mg protein, P =0.0063), indicative of increased peroxidation in the elderly. These differences correlated with changes in functional enrichment of genes regulating ROS homeostasis pathways in aged human and rat hearts. Functional merged collective network and pathway enrichment analysis revealed common genes prioritized in human and rat aging‐associated networks that underlay enriched functional terms of mitochondrial complex I and common pathways in the aging human and rat heart. Conclusions Aging sensitizes mitochondrial and extramitochondrial mechanisms of ROS buildup within the heart. Network analysis of the transcriptome highlights the critical elements involved with aging‐related ROS homeostasis pathways common in rat and human hearts as targets.

In adolescence, the solution to the problem of professional self-determination involves making plans for the future and relating them to the present in a time perspective. Young people’s visions of their future give personal meaning to the motivations for their educational activities and social activism. How do young people today see their future? To what extent is the image of the future determined by gender stereotypes and attitudes, educational level, region of residence? Research Objective: To conduct empirical studies of personal preparedness for professional self-determination. Sample characteristics: 160 boys and girls living in industrial regions and Moscow. Research methods: Stanford Time Perspective Questionnaire P. Zimbardo (ZTPI), Problematic Questionnaire. It was concluded that the current early adolescence (16-18 years) is characterized by a contradiction between the aspiration to the future as the most important age pattern and the psychological unwillingness of young people to meet the institutional requirements of adulthood. For today’s high school students, present and future have almost equal value. For school leavers, the future looks less appealing than for the tenth graders, but the anxiety about their future is offset in part by a positive assessment of the past. The findings confirm that there are gender differences in the depth of thinking about the future: boys value their future more than girls.

Aims Fibroblast to myofibroblast trans‐differentiation with altered bioenergetics precedes cardiac fibrosis (CF). Either prevention of differentiation or promotion of de‐differentiation could mitigate CF‐related pathologies. We determined whether 3‐hydroxy‐3‐methyl‐glutaryl‐coenzyme A (HMG‐CoA) reductase inhibitors—statins, commonly prescribed to patients at risk of heart failure (HF)—can de‐differentiate myofibroblasts, alter cellular bioenergetics, and impact the human ventricular fibroblasts (hVFs) in HF patients. Methods and results Either in vitro statin treatment of differentiated myofibroblasts (n = 3–6) or hVFs, isolated from human HF patients under statin therapy (HF + statin) vs. without statins (HF) were randomly used (n = 4–12). In vitro, hVFs were differentiated by transforming growth factor‐β1 (TGF‐β1) for 72 h (TGF‐72 h). Differentiation status and cellular oxygen consumption rate (OCR) were determined by α‐smooth muscle actin (α‐SMA) expression and Seahorse assay, respectively. Data are mean ± SEM except Seahorse (mean ± SD); P

Excessive fibrosis underlies many critical organ dysfunctions.1, 2 Fibrosis emanates from fibroblast trans‐differentiation into myofibroblasts,3 marked by increased α‐smooth muscle actin (α‐SMA) expression and excessive collagen secretion, initiated as a reparative process of normal wound healing and tissue repair in response to injury.4 However, activated myofibroblasts accumulate within pathological lesions of various fibrotic disorders,5 including patchy and interstitial fibrosis in progressive heart failure and cardiac hypertrophy.6 Therefore, attenuation of differentiation to myofibroblasts is expected to mitigate fibrosis. We attempted to find a potential target to extenuate the fibroblast differentiation by analysing the transcription factors in human fibroblasts/myofibroblasts, as transcriptome changes occur in fibroblasts during differentiation.7 Here, we report a novel molecular target, transcription factor AP‐2α (TFAP2A), to reduce fibroblasts trans‐differentiation.

Several studies have been reported in various domains from induction methods to utilities of somatic cell pluripotent reprogramming. However, one of the major struggles facing the research field of induced pluripotent stem cell (iPSC)-derived target cells is the lack of consistency in observations. This could be due to variety of reasons including varied culture periods post-differentiation. The cardiomyocytes (CMs) derived from iPSCs are commonly studied and proposed to be utilized in the comprehensive in vitro proarrhythmia initiative for drug safety screening. As the influence of varied culture periods on the electrophysiological properties of iPSC-CMs is not clearly known, using whole-cell patch clamp technique, we compared two groups of differentiated ventricular-like iPSC-CMs that are cultured for 10 to 15 days (D10–15) and more than 30 days (≥ D30) both under current and voltage clamps. The prolonged culture imparts increased excitability with high-frequency spontaneous action potentials, robust increase in the magnitude of peak Na+ current density, relatively shallow inactivation kinetics of Na+ channels, faster recovery from inactivation, and augmented Ca2+ current density. Quantitative real-time PCR studies of α-subunit transcripts showed enhanced mRNA expression of SCN1A, SCN5A Na+ channel subtypes, and CACNA1C, CACNA1G, and CACNA1I Ca2+ channel subtypes, in ≥ D30 group. Conclusively, the prolonged culture of differentiated iPSC-CMs affects the excitability, single-cell electrophysiological properties, and ion channel expressions. Therefore, following standard periods of culture across research studies while utilizing ventricular-like iPSC-CMs for in vitro health/disease modeling to study cellular functional mechanisms or test high-throughput drugs’ efficacy and toxicity becomes crucial.

Introduction: Acute postoperative heart failure (PoHF) is encountered in 20-35% of elderly patients after cardiac surgery but predictors are not well defined. Circulating microRNAs (miRNAs) predict HF or postoperative atrial fibrillation, yet, their role in identifying those at risk for PoHF with preserved LV function and gender-related differences is not known. Hypothesis: miRNAs involved in CVD can identify patients who develop PoHF in gender-specific manner. Methods: Preoperative blood samples from patients with preserved LV function undergoing cardiac surgery with no prior history of HF, supraventricular, or ventricular tachycardia was used for RNA isolation. Differences in relative plasma levels of miRNA between PoHF vs. No-PoHF were assessed using qPCR. Univariate and multiple logistic regressions were performed to assess risk factors for PoHF. Results: Out of 68 patients (mean age 68.3±12.4), 13 (19%) developed PoHF (54% males; mean age 64.1±15.1; p=0.23), while 55 (51% males; mean age 69.3y ± 11.6) remained free of PoHF. Although all patients had preserved LV function, those who developed PoHF had lower LVEF, (52 vs 58; P Conclusions: The differences in preoperative miRNA expression in pathways involved in ECM turnover in male patients who develop PoHF is suggestive of pathophysiological substrate differences between males and females and identifies a group at risk of PoHF with preserved LV function.

Introduction: Metformin (Metf) is an oral hypoglycemic agent widely used to treat type 2 diabetes. It also lessens myocardial injury and reduces cardiovascular mortality. However, the exact molecular mechanisms of Metf therapeutic action in the human heart remain obscure. The aim of this study was to evaluate the cardioprotective effect of Metf on cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs). Methods: The hiPSC-CMs were derived from an hiPSC line generated from human dermal fibroblasts and treated with Metf (0-20 mM) for 24 hours. Oxygen consumption rate (OCR) was measured using XF96 Extracellular Flux Analyzer. Metabolites were profiled using a liquid chromatography coupled to tandem mass spectrometry. Tukey’s pairwise comparison and one-way ANOVA were applied for comparison between groups. P < 0.05 was considered significant. Results: At concentrations ≤ 2.5 mM, Metf significantly enhanced the cellular OCR (Fig. A) and enhanced mitochondrial biogenesis (Fig. B) via AMPK signaling (Fig. C). This effect was abrogated by compound C, an inhibitor of AMPK. At concentrations > 5 mM, Metf reduced the cellular OCR and activated glycolysis (Fig. D) and glutaminolysis (Fig. E) in the cardiomyocytes. Conclusion: Thus, in the human heart, Metf might improve cardioprotection owing to its dual effect on mitochondria. At low doses, it activates mitochondrial biogenesis via AMPK signaling and increases the OCR. At high doses, it causes metabolic reprogramming by enhancing glycolysis and glutaminolysis as a compensatory mechanism in response to inhibition of the mitochondrial oxidative phosphorylation.

Introduction: Studies have shown that right (RA) and left (LA) have different susceptibilities toward developing atrial fibrillation (AF). However, the molecular basis of these differences are not well characterized. Given these, we hypothesize that AF is associated with dissimilar energetic remodeling in the RA and LA and presence of interatrial differences might be a potential reason for different susceptibility of the atria to AF. Objective: The aim was to compare differences in mitochondrial oxidative phosphorylation system (OXPHOS) between the RA and LA in patients with and without AF (non-AF) and determine whether the same differences in chamber-specific sensitivity toward AF exist in the animal model of AF. Methods: The RA and LA tissue were collected from non-AF and AF dogs and consented patients undergoing elective open-heart surgery. Gene expression profiling of 72 genes involved in OXPHOS was performed using the Mitochondrial Energy Metabolism RT2 Profiler PCR Array. Comparison between the AF and non-AF groups were determined by using a pairwise differential expression analysis. A Venn diagram tool was applied to visualize expressed genes that overlap. Results: Expression of 14 and 25 genes was significantly reduced in the human and dog RA, correspondingly. Unlike, expression of only 2 and 9 genes was significantly reduced in human and dogs LA. The Venn diagram demonstrates the overlaps (common genes) and differences between the genes in patients and dogs with AF (Fig. A, B). Conclusion: AF is associated with different chamber-specific energetic remodeling suggesting that dissimilar mechanisms may contribute to the development and progression of AF.

Background: Advancements in cardiac surgical techniques have led to decreasing operative risk. However, postoperative heart failure (PoHF) continues to be a major risk factor for adverse cardiac events in 20-35% of patients after cardiac surgery, with a 10-fold increase in 30-day mortality. Prediction of PoHF is challenging, particularly in patients with preserved ventricular function. Circulating microRNAs (miRNAs) recently were identified to predict HF or AF after surgery, but their role in predicting PoHF is not known. This study aimed to find novel noninvasive circulating biomarkers along with clinical factors that can identify patients at risk of developing PoHF immediately after surgery. Methods: Patients undergoing CABG surgery with no previous history of HF, ventricular or supraventricular tachycardia were recruited, and preoperative blood assessed for circulating levels of protein biomarkers using ELISA. Differences in relative plasma levels of 13 miRNAs between the PoHF and no-PoHF groups were assessed by qPCR. Preoperative echocardiography was obtained. SAS was used for statistical analysis and ROC curve. Results: Out of 68 patients, 13 developed PoHF (19.1%, mean age 64.1±11.6y, 53.8% males), whereas 55 (mean age 68.3±12.4y) remained free of HF. Patients who developed PoHF had lower LVEF (51.4±13.7 vs 58.2±9.9, P1. PC cluster2 consisted of miR-23a, -23b, -25 and -26a2, principally involved in oxidatives stress, fibrosis and contractility, and had the strongest association (AUC=0.797; P Conclusion: Our study demonstrates that miR-23a, -23b, -25 and -26a2 may be useful predictors of PoHF. Circulating miRNA as biomarkers may have diagnostic potential to preoperatively, noninvasively identify patients at risk of developing PoHF.

Background Excessive cardiac fibrosis due to maladaptive remodeling leads to progression of cardiac dysfunction and is modulated by TGF-β1-activated intracellular phospho-SMAD signaling effectors and transcription regulators. SMAD2/3 phosphorylation, regulated by protein-phosphatases, has been studied in different cell types, but its role in human ventricular fibroblasts (hVFs) is not defined as a target to reduce cytokine-mediated excessive fibrotic response and adverse cardiac remodeling. Statins are a class of drugs reported to reduce cardiac fibrosis, although underlying mechanisms are not completely understood. We aimed to assess whether simvastatin-mediated reduction in TGF-β1-augmented profibrotic response involves reduction in phospho-SMAD2/3 owing to activation of protein-phosphatase in hVFs. Methods and results Cultures of hVFs were used. Effect of simvastatin on TGF-β1-treated hVF proliferation, cytotoxicity, myofibroblast differentiation/activation, profibrotic gene expression and protein-phosphatase activity was assessed. Simvastatin (1 μM) reduced effect of TGF-β1 (5 ng/mL) on hVF proliferation, myofibroblast differentiation (reduced α-smooth muscle actin [α-SMA-expression]) and activation (decreased procollagen-peptide release). Simvastatin also reduced TGF-β1-stimulated time-dependent increases in SMAD2/3 phosphorylation and nuclear translocation, mediated through catalytic activation of protein-phosphatases PPM1A and PP2A, which physically interact with SMAD2/3, thereby promoting their dephosphorylation. Effect of simvastatin on TGF-β1-induced fibroblast activation was annulled by okadaic acid, an inhibitor of protein-phosphatase. Conclusions This proof-of-concept study using an in vitro experimental cell culture model identifies the protective role of simvastatin against TGF-β1-induced hVF transformation into activated myofibroblasts through activation of protein phosphatase, a novel target that can be therapeutically modulated to curb excessive cardiac fibrosis associated with maladaptive cardiac remodeling.

Energy production in myocardial cells occurs mainly in the mitochondrion. Although alterations in mitochondrial functions in the senescent heart have been documented, the molecular bases for the aging-associated decline in energy metabolism in the human heart are not fully understood. In this study, we examined transcription profiles of genes coding for mitochondrial proteins in atrial tissue from aged (≥65 years old) and comorbidities-matched adult (

Background: Postoperative atrial fibrillation (PoAF) is a common complication occurring in 35-50% patients within 2-3 days after cardiac surgery. Identification of patients, especially those with no prior history of atrial fibrillation before surgery, is a challenge. A pre-existing atrial substrate appears to be an important factor in the development of PoAF. The aim of this study was to assess the role of biomarkers in identifying patients at risk of PoAF in a pathophysiology-based risk predictive model by combining clinical and biochemical risk factors. Methods: Preoperative blood from patients undergoing cardiac surgery with no previous history of AF was assessed for circulating levels of biomarkers reflecting collagen synthesis/degradation and extracellular matrix remodeling using ELISA. Reverse transcriptase polymerase chain reaction assessed microRNA29 in the serum and correlated to extent of atrial fibrosis. Echocardiographic evaluation of LA mechanics was performed preoperatively using M-mode, 2D Doppler, and 3D Speckle tracking. Results: Out of 55 patients, 31 patients (56.4%) who developed PoAF after surgery during their hospital stay were older in age (70.0 ± 4.0 years vs.63.4±9.9; p Conclusion: Our study developed a noninvasive tool to identify those who are at risk for new-onset PoAF in patients with no previous history of AF when combining age, biomarkers of collagen synthesis and microRNA-29a.

Background Postoperative atrial fibrillation (PoAF) is a common complication after cardiac surgery. A pre-existing atrial substrate appears to be important in postoperative development of dysrhythmia, but its preoperative estimation is challenging. We tested the hypothesis that a combination of clinical predictors, noninvasive surrogate markers for atrial fibrosis defining abnormal left atrial (LA) mechanics, and biomarkers of collagen turnover is superior to clinical predictors alone in identifying patients at-risk for PoAF. Methods In patients without prior AF undergoing coronary artery bypass grafting, concentrations of biomarkers reflecting collagen synthesis and degradation, extracellular matrix, and regulatory microRNA-29s were determined in serum from preoperative blood samples and correlated to atrial fibrosis extent, alteration in atrial deformation properties determined by 3D speckle-tracking echocardiography, and AF development. Results Of 90 patients without prior AF, 34 who developed PoAF were older than non-PoAF patients (72.04 ± 10.7 y; P = 0.043) with no significant difference in baseline comorbidities, LA size, or ventricular function. Global (P = 0.007) and regional longitudinal LA strain and ejection fraction (P = 0.01) were reduced in PoAF vs. non-PoAF patients. Preoperative amino-terminal-procollagen-III-peptide (PIIINP) (103.1 ± 39.7 vs. 35.1 ± 19.3; P = 0.041) and carboxy-terminal-procollagen-I-peptide levels were elevated in PoAF vs. non-PoAF patients with a reduction in miR-29 levels and correlated with atrial fibrosis extent. Combining age as the only significant clinical predictor with PIIINP and miR-29a provided a model that identified PoAF patients with higher predictive accuracy. Conclusions In patients without a previous history of AF, using age and biomarkers of collagen synthesis and regulation, a noninvasive tool was developed to identify those at risk for new-onset PoAF.

Mechanisms by which metformin (Mtf) protects human heart in type 2 diabetes remain debated. We hypothesize that Mtf has a biphasic effect on mitochondria: it causes activation of respiration at low doses via AMPK signaling and inhibition at high doses by directly affecting the activity of complex I and reducing oxidative stress. Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) and mitochondria isolated from human cardiac tissue were exposed to different doses of Mtf (0-20 mM) for 24h and acutely. Oxygen consumption rate (OCR) was assessed in the cells and mitochondria energized by glutamate and malate (complex I substrates) using XF96 Extracellular Flux Analyzer. Superoxide production was measured by monitoring changes in fluorescence intensity of dihydroethidium (DHE). At low doses (0.1 - 1 mM), Mtf significantly increased OCR in hiPSC-CMs (Fig. 1A). The highest OCR was observed at 0.5 mM Mtf. This effect was abrogated by compound C, an inhibitor of AMP-kinase (Fig. 1A). Mtf did not increase OCR in isolated mitochondria (Fig. 1B). At higher doses (1-20 mM), it inhibited OCR both in the cells and isolated mitochondria. This was associated with reduction of superoxide production in the mitochondria (Fig. 1C). In the human heart, Mtf improves cardioprotection due to its biphasic effect on mitochondria. This can be a beneficial alternative to patients with impaired endogenous cardioprotective responses. Disclosure L. Emelyanova: None. X. Bai: None. T. Rudic: None. C. Warner: None. F. Rizvi: None. G. Ross: None. D. Kress: None. A. Jahangir: None. Funding Aurora Health Care (N-570-3657)

Objective Metformin (Metf), an oral antihyperglycemic agent, is widely used to treat type 2 diabetes mellitus. The primary action of the drug is to lower hepatic glucose synthesis and enhance perip...

PurposeHigh calorie intake leads to obesity, a global socio-economic and health problem, reaching epidemic proportion in children and adolescents. Saturated and monounsaturated fatty acids from animal (lard) fat are major components of the western-pattern diet and its regular consumption leads to obesity, a risk factor for cardiovascular disease. However, no clear evidence exists whether consumption of diet rich in saturated (SFAs) and monounsaturated (MUFAs) fatty acids has detrimental effects on cardiac structure and energetics primarily due to excessive calories. We, therefore, sought to determine the impact of high calories versus fat content in diet on cardiac structure and mitochondrial energetics.MethodsSix-week-old C57BL/6J mice were fed with high calorie, high lard fat-based diet (60% fat, HFD), high-calorie and low lard fat-based diet (10% fat, LFD), and lower-calorie and fat diet (standard chow, 12% fat, SCD) for 10 weeks.ResultsThe HFD- and LFD-fed mice had higher body weight, ventricular mass and thickness of posterior and septal wall with increased cardiomyocytes diameter compared to the SCD-fed mice. These changes were associated with a reduction in the mitochondrial oxidative phosphorylation (OXPHOS) complexes I and III activity compared to the SCD-fed mice without significant differences between the HFD- and LFD-fed animals. The HFD-fed animals had higher level of malondialdehyde (MDA) than LFD and SCD-fed mice.ConclusionsWe assume that changes in cardiac morphology and selective reduction of the OXPHOS complexes activity observed in the HFD- and LFD-fed mice might be related to excessive calories with additional effect of fat content on oxidative stress.

Purpose: Excessive fibrosis has been suggested to result from persistence of fibroblasts in injured tissue due to impaired apoptosis, but signaling pathways are not fully defined. Methods: Suppression of apoptotic cell death following transforming growth factor-β1 (TGF-β1) exposure was studied using the culture of NIH/3T3 mouse embryonic fibroblasts. Caspase-3 activity, propidium iodide staining and annexin V binding induced by Fas-ligand (FasL) in NIH/3T3 fibroblasts in the absence and presence of TGF-β1 was determined, and relative contribution of signaling through Smad2/3 and noncanonical Erk1/2 and Akt pathways was dissected by assessing phosphorylation status of these kinases and caspase activity in the absence and presence of specific inhibitors (SB431542, PD0325901 and LY294002), respectively. Results: TGF-β1 treatment suppressed FasL-mediated fibroblasts apoptosis with a greater than threefold reduction of caspase-3 activity (from 894 ± 186 to 195 ± 56 nmol AFC/min/106 cells at 250 ng/mL of FasL) and reductions in cleaved caspase-8 and caspase-3 by 3.2-fold and 4.3-fold, respectively. The reduction in caspase activation was accompanied by a decrease in annexin V-positive cells by ~80%. TGF-β1 treatment phosphorylated Smad2/3, Erk1/2 and Akt, which were reduced by their selective inhibitors. Inhibition of Smad2/3 and Erk1/2 alone partially reduced the protective effect of TGF-β1 on caspase-3 activation, whereas inhibition of the Akt pathway had no significant effect. Concomitant inhibition of Smad2/3 and Erk1/2 completely reversed the protection by TGF-β1. Conclusions: TGF-β1-mediated suppression of apoptosis in fibroblasts involves both Smad2/3 and Erk1/2 pathways, but not the Akt pathway. A combined approach inhibiting Smad2/3 and Erk1/2 pathways can completely reverse the protective effect of TGF-β1 on apoptosis. These findings are proof of concept to help define strategies to reduce progression of fibrosis and resultant morbidities associated with conditions causing excessive fibrosis, including but not limited to keloid formation, transplant fibrosis and aging-associated fibrosis of the heart.

Fibroblasts, the most abundant cells in the heart, contribute to cardiac fibrosis, the substrate for the development of arrythmogenesis, and therefore are potential targets for preventing arrhythmic cardiac remodeling. A chamber-specific difference in the responsiveness of fibroblasts from the atria and ventricles toward cytokine and growth factors has been described in animal models, but it is unclear whether similar differences exist in human cardiac fibroblasts (HCFs) and whether drugs affect their proliferation differentially. Using cardiac fibroblasts from humans, differences between atrial and ventricular fibroblasts in serum-induced proliferation, DNA synthesis, cell cycle progression, cyclin gene expression, and their inhibition by simvastatin were determined. The serum-induced proliferation rate of human atrial fibroblasts was more than threefold greater than ventricular fibroblasts with faster DNA synthesis and higher mRNA levels of cyclin genes. Simvastatin predominantly decreased the rate of proliferation of atrial fibroblasts, with inhibition of cell cycle progression and an increase in the G0/G1 phase in atrial fibroblasts with a higher sensitivity toward inhibition compared with ventricular fibroblasts. The DNA synthesis and mRNA levels of cyclin A, D, and E were significantly reduced by simvastatin in atrial but not in ventricular fibroblasts. The inhibitory effect of simvastatin on atrial fibroblasts was abrogated by mevalonic acid (500 μM) that bypasses 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibition. Chamber-specific differences exist in the human heart because atrial fibroblasts have a higher proliferative capacity and are more sensitive to simvastatin-mediated inhibition through HMG-CoA reductase pathway. This mechanism may be useful in selectively preventing excessive atrial fibrosis without inhibiting adaptive ventricular remodeling during cardiac injury.

Several studies have been reported in various domains from induction methods to utilities of somatic cell pluripotent reprogramming. However, one of the major struggles facing the research field of induced pluripotent stem cell (iPSC)-derived target cells is the lack of consistency in observations. This could be due to variety of reasons including varied culture periods post-differentiation. The cardiomyocytes (CMs) derived from iPSCs are commonly studied and proposed to be utilized in the comprehensive in vitro proarrhythmia initiative for drug safety screening. As the influence of varied culture periods on the electrophysiological properties of iPSC-CMs is not clearly known, using whole-cell patch clamp technique, we compared two groups of differentiated ventricular-like iPSC-CMs that are cultured for 10 to 15 days (D10-15) and more than 30 days (≥ D30) both under current and voltage clamps. The prolonged culture imparts increased excitability with high-frequency spontaneous action potentials, robust increase in the magnitude of peak Na

Background: Circulating microRNAs have recently been identified as biomarkers predicting A-Fib and heart failure. Yet, their role in identifying those at risk for postoperative atrial fibrillation (PoAF) in a gender-specific manner has not been studied. Methods: Preoperative blood from patients undergoing cardiac surgery with no prior history of AF, supraventricular/ventricular tachycardia was used for RNA isolation. Differences in the relative levels of miRNA between those who did/did not develop PoAF were assessed using qPCR. Principal component analysis and receiver operative characteristics were performed to predict miRNA associated with PoAF. Results: Out of 56 patients, 29 developed PoAF (52%, mean age 70.4± 9y, 51% males), while 27 (mean age 63y ± 10) remained free of AF. Patients who developed PoAF were older (P Conclusion: This indicates the existence of different substrate/precipitating factors reflected in miRNAs profile in male and female patients who developed PoAF. Gender differences exist in circulatory miRNA levels can help in predicting the development of new-onset AF after cardiac surgery.

Introduction: Right and left atria have different susceptibilities toward developing atrial fibrillation (AF). The molecular bases of these differences are not well characterized. Given the complexity of AF development and progression, understanding AF-associated changes in myocardial energetics between the atria will help improve mechanistic insights and therapeutics for better clinical management of AF. The aim was to compare changes in mitochondrial oxidative phosphorylation system (OXPHOS), glycolysis and Krebs cycle metabolites in right atrial (RAA) and left atrial (LAA) appendage tissue from patients with (AF) and without (non-AF) AF. Methods: RAA and LAA from well-matched AF (n=54) and non-AF (n=58) patients undergoing elective open heart surgery was collected. Functional activity of OXPHOS complexes I-V was measured spectrophotometrically. Protein expression level of OXPHOS complexes was determined by Western blot. OXPHOS gene expression level was performed using RT-PCR. Metabolites were profiled using high performance liquid chromatography coupled to tandem mass spectrometry. Comparison between groups was done applying the 2 sample t - and Wilcoxon rank sum tests with 5% level of significance. Results: The most significant AF-associated alterations in myocardial energetics were observed in RAA. In AF patients, out of 84 OXPHOS genes, expression of 14 genes was significantly reduced in RAA (p+ (p=0.03), GDP (p=0.05), citrate (p=0.03), total pool of adenine nucleotides (p=0.02) and glutathione (p=0.03) level in RAA without changes in LAA. Conclusion: AF is associated with different energetic remodeling in right and left atria, suggesting that dissimilar mechanisms may contribute to development and progression of AF.

Background: Cardiomyocytes (CM), derived from human induced-pluripotent stem cells (iPSC-CM), are promising tools for in vitro proarrhythmia screening for drug safety. However, among various challenges with interpretation of iPSC-CM experimental results, the influence of varied culture periods post-differentiation on the electrophysiological properties of iPSC-CMs is unclear. Objective: To test the hypothesis that prolonged post-differentiation culture of iPSC-CMs will influence the biophysical characteristics of Na + - and Ca 2+ -channels. Methods: Using whole-cell patch clamp, we compared the electrophysiological properties of differentiated ventricular-like iPSC-CMs (APD 30-40 /APD 70-80 >1.5) cultured for 10 to 15 days (D10-15) to those cultured for more than 30 days (≥ D30) both under current- and voltage- clamp configurations. Quantitative real-time PCR was used to quantify the mRNA expression of voltage-gated Na channel subunits SCN1A, SCN5A and Ca channel subunits CACNA1C, CACNA1G and CACNA1I. Fold change was calculated by 2 -ΔΔCt method. Data were analyzed by Student’s t test, and P value Results: Post-differentiation prolonged culture imparts increased cellular excitability with high frequency spontaneous action potentials, robust increase in the magnitude of peak Na + -current level, relatively shallow inactivation kinetics of Na + channels, faster recovery from inactivation, and augmented Ca 2+ current density compared to early cultured iPSC-CM. This was associated with a greatly enhanced mRNA expression of α-subunit transcripts of SCN1A (7.5 fold) and SCN5A (38 fold) Na channel subtypes while less robust elevation in the mRNA expression of CACNA1C (0.5 fold), CACNA1G (2 fold) and CACNA1I (2 fold) subunits in prolonged culture compared to early cultured iPSC-CM. Conclusion: Prolonged culture of ventricular-like iPSC-CMs affects the excitability, single-cell electrophysiological properties and differential ion channels subunit expression. Standardization of post-differentiation period for ventricular-like iPSC-CMs culture is crucial for in vitro proarrhythmia screening, health/disease modelling to study cellular mechanisms or test high-throughput drugs’ efficacy and toxicity.

Introduction: Although generations of reactive oxygen species and mitochondrial dysfunction have been implicated in pathogenesis of alcoholic cardiomyopathy (ACM), molecular target(s) responsible for myocardial dysfunction in ACM are not well known. Objective: To determine the impact of chronic alcohol exposure on mitochondrial oxidative phosphorylation system (OXPHOS), permeability transition pore (mPTP) opening, and oxidative stress using a rat model of ACM. Methods: Sprague Dawley male rats (1 mo old) were exposed to alcohol (7.5% ethanol) for 3 months to develop ACM. Activity of OXPHOS was assessed enzymatically and by measuring mitochondrial oxygen consumption rate (OCR). The mPTP opening was determined by monitoring abrupt release of Ca 2+ after exposure of mitochondria to Ca 2+ . Western blot and RT-PCR were used to assess the expression of OXPHOS and mPTP protein components and corresponding genes. Malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were determined in heart tissue homogenates. Results: There was no significant change in OCR or activity of OXPHOS complexes I-V, despite a decrease in complex V protein and Atp6v1e2 gene expression (-1.7-fold, p2+ -induced mPTP opening. This was associated with increase in protein expression level of adenine nucleotide translocase 1/2 and voltage dependent anion channel 1. There was no difference in MDA or 4-HNE levels. Conclusion: Increased sensitivity of mitochondria to mPTP opening during long-term alcohol consumption may compromise cardiac energetic reserves and contractility, leading to ACM development and progression.

Background: AF, a common sustained arrhythmia that predisposes heart failure and stroke, is associated with cardiac fibrosis and oxidative stress. Peroxisome proliferator-activated receptor (PPAR)-α, important for ROS and lipid degradation, is reported to negatively correlate with kidney, liver, and lung fibrosis, but its role in cardiac fibrosis is less clear. We hypothesize that reduced expression of PPARα in AF contributes to oxidative stress and interferes with TGFβ signaling, a cytokine implicated in cardiac fibrosis. Methods: Myocardial fibrosis was detected (Masson trichrome) in right atrial appendages of AF and non-AF patients. Levels of 4-hydroxynonenal (4-HNE) (ELISA) and superoxide production (MitoSOX) were assayed in patients’ atrial tissue homogenates and cardiac myofibers respectively. Using atrial fibroblasts (hAF) from AF and non-AF patients, α-SMA, COL1A1 and c-Jun/c-Fos expressions were determined (RT-PCR and/or Western Blot) in the absence and presence of TGF-β (5 ng) with or without ciprofibrate (200 μM), a PPARα agonist. Results: Increased atrial fibrosis, levels of 4-HNE (101.7 vs 7.4 ng/mg protein; p=0.02(n=6)) and oxidative stress (8.7 fold; p=0.04) correlated with reduced PPAR-α mRNA (2.1 fold; p Conclusion: Reduced expression of PPARα is associated with impaired cardiac mitochondrial metabolism and promotes TGFβ-induced profibrotic pathway. Preliminary data suggest PPARα agonist might confer therapeutic benefits for patients with cardiac fibrosis and oxidative stress in AF.

Excessive cardiac fibrosis, characterized by increased collagen-rich extracellular matrix (ECM) deposition, is a major predisposing factor for mechanical and electrical dysfunction in heart failure (HF). The human ventricular fibroblast (hVF) remodeling mechanisms that cause excessive collagen deposition in HF are unclear, although reports suggest a role for [Ca2+]i in fibrosis. Therefore, we determined the association of differences in cellular Ca2+ dynamics and collagen secretion/deposition between hVFs from failing and normal (control) hearts. Histology of left ventricle sections (Masson trichrome) confirmed excessive fibrosis in HF vs normal. In vitro, hVFs from HF showed increased secretion/deposition of soluble collagen in 48 hours of culture compared with control [85.9±7.4 μg/106 vs 58.5±8.8 μg/106 cells, P

Introduction: Excessive cardiac fibrosis (CF) underlies mechanical and electrical dysfunction in heart failure (HF). However, the underlying mechanisms of increased CF are unclear. Recently, we reported increased Orai1 expression and I CRAC (calcium release-activated channels) -Ca 2+ influx in failing heart ventricular fibroblasts (hVF). Therefore, we studied the magnitude of collagen secretion/deposition by hVF from failing hearts and the involvement of Ca 2+ influx through I CRAC channels in this process. Hypothesis: We tested the hypothesis that collagen secretion/deposition by hVFs from failing hearts will be high and sensitive to inhibition of I CRAC channels, compared to normal hearts. Methods: Primary cultures of hVF obtained from HF patients undergoing LV assist device implantation (n=9) were compared to non-diseased hVF from trauma victims (n=4). The degree of fibrosis was analyzed by histology of LV tissue sections (5μm) with Masson’s trichrome staining. Collagen secretion/deposition after 48 h culture of hVFs from failing or normal hearts in the presence or absence of I CRAC inhibitor, YM-58483(10 μM), was assayed calorimetrically using Sircol™ kit. Data were analyzed by unpaired Student’s t-test. Results: Histology of the failing heart LV sections with Masson’s trichome staining showed severe fibrosis compared to control sections. The percentage of positive staining area to total area, measured using custom-developed ImageJ macro, was significantly (p6 cells) than normal heart hVF (58.4±8.8 μg/10 6 cells). Incubation of fibroblasts with the I CRAC inhibitor YM58486 (10 μM) for 48 h eliminated the increase in collagen secretion of HF fibroblasts (55.8± 7 μg/10 6 cells vs 66.8± 6 μg/10 6 cells, p=0.27). Conclusion: LV fibrosis is severe in HF patients. The magnitude of pro-fibrotic collagen secretion/deposition by hVF from HF patients is significantly high but sensitive to I CRAC inhibition. Selective targeting of fibroblast I CRAC may be a potential therapeutic tool to mitigate progression of CF and HF.

Introduction: Although alterations in mitochondrial function have been observed in senescent hearts, the molecular basis for aging-associated decline in energy metabolism in the human heart is not fully understood. Objective: To determine aging-related changes in functional activity and protein expression level of mitochondrial oxidative phosphorylation (OXPHOS) complexes and expression of genes regulating mitochondrial energetics in the human heart. Methods: Right atrial appendages from well-matched adult (29-57 y.o., n=19) and aged (65-85 y.o., n=22) patients undergoing elective CABG surgery were used. Functional activity of OXPHOS complexes was measured spectrophotometrically. Protein expression level of corresponding OXPHOS protein subunits was determined by Western blot. Gene expression profiling was performed using Affymetrix Human Genome U133 Plus 2.0 microarrays. Results: Mitochondria from senescent hearts demonstrated a significant decrease in complex I and V functional activity without significant changes in the rest of the complexes (Fig. A). At the protein expression level, there was reduction in complex I, III, and IV (Fig. B). This was associated with downregulation of the majority (86%, 90 of 105) of genes coding mitochondrial proteins (Fig. C). Forty-six percent (41 of 90) of the downregulated genes were confined to pathways regulating mitochondrial energetics. Conclusion: With aging, the functional activity of OXPHOS is reduced due to supression of protein expression and downregulation of genes regulating mitochondrial energetics. This provides a substrate for reduced energetic efficiency associated with senescence in the human atria.

Background: Ventricular fibrosis leads to progressive cardiac dysfunction and heart failure (HF). Statins are reported to reduce cardiac fibrosis through the cholesterol-independent pathway, but mechanisms remain elusive. We hypothesize simvastatin reduced TGF-β1-induced ventricular fibrosis through activation of SMAD protein phosphatase Mg 2+ /Mn 2+ -1A (PPM1A), -2A (PP2A). Methods: In the absence and presence of TGF-β1 (5ng) with or without simvastatin (1μM), the rate of fibroblast proliferation (doubling time), myofibroblast differentiation (ICC), α-SMA mRNA (RT-PCR) and protein expression (Western blot) and the release of collagen synthesis markers, pro-collagen type I C-terminal peptide (PICP) and pro-collagen type III N-terminal peptide (PIIINP), in the media (ELISA) were determined along with protein interaction between SMAD2/3 and PPM1A or PP2A (Co-IP) and SMAD2/3 phosphorylation (Western blot). Results: Simvastatin reduced the effect of TGF-β1 on hVF proliferation by 47% (50000 to 26500), p Conclusion: Involvement of PPM1A and PP2A in the anti-fibrotic effect of simvastatin reveals novel signaling mediators that may be selectively targeted for prevention of myocardial injury-induced ventricular fibrosis and HF.

Mitochondria are critical for maintaining normal cardiac function, and a deficit in mitochondrial energetics can lead to the development of the substrate that promotes atrial fibrillation (AF) and its progression. However, the link between mitochondrial dysfunction and AF in humans is still not fully defined. The aim of this study was to elucidate differences in the functional activity of mitochondrial oxidative phosphorylation (OXPHOS) complexes and oxidative stress in right atrial tissue from patients without (non-AF) and with AF (AF) who were undergoing open-heart surgery and were not significantly different for age, sex, major comorbidities, and medications. The overall functional activity of the electron transport chain (ETC), NADH:O2 oxidoreductase activity, was reduced by 30% in atrial tissue from AF compared with non-AF patients. This was predominantly due to a selective reduction in complex I (0.06 ± 0.007 vs. 0.09 ± 0.006 nmol·min−1·citrate synthase activity−1, P = 0.02) and II (0.11 ± 0.012 vs. 0.16 ± 0.012 nmol·min−1·citrate synthase activity−1, P = 0.003) functional activity in AF patients. Conversely, complex V activity was significantly increased in AF patients (0.21 ± 0.027 vs. 0.12 ± 0.01 nmol·min−1·citrate synthase activity−1, P = 0.005). In addition, AF patients exhibited a higher oxidative stress with increased production of mitochondrial superoxide (73 ± 17 vs. 11 ± 2 arbitrary units, P = 0.03) and 4-hydroxynonenal level (77.64 ± 30.2 vs. 9.83 ± 2.83 ng·mg−1 protein, P = 0.048). Our findings suggest that AF is associated with selective downregulation of ETC activity and increased oxidative stress that can contribute to the progression of the substrate for AF.

Objectivs Cytokine-dependent activation of fibroblasts to myofibroblasts, a key event in fibrosis, is accompanied by phenotypic changes with increased secretory and contractile properties dependent on increased energy utilization, yet changes in the energetic profile of these cells are not fully described. We hypothesize that the TGF-β1-mediated transformation of myofibroblasts is associated with an increase in mitochondrial content and function when compared to naive fibroblasts. Methods Cultured NIH/3T3 mouse fibroblasts treated with TGF-β1, a profibrotic cytokine, or vehicle were assessed for transformation to myofibroblasts (appearance of α-smooth muscle actin [α-SMA] stress fibers) and associated changes in mitochondrial content and functions using laser confocal microscopy, Seahorse respirometry, multi-well plate reader and biochemical protocols. Expression of mitochondrial-specific proteins was determined using western blotting, and the mitochondrial DNA quantified using Mitochondrial DNA isolation kit. Results Treatment with TGF-β1 (5 ng/mL) induced transformation of naive fibroblasts into myofibroblasts with a threefold increase in the expression of α-SMA (6.85 ± 0.27 RU) compared to cells not treated with TGF-β1 (2.52 ± 0.11 RU). TGF-β1 exposure increased the number of mitochondria in the cells, as monitored by membrane potential sensitive dye tetramethylrhodamine, and expression of mitochondria-specific proteins; voltage-dependent anion channels (0.54 ± 0.05 vs. 0.23 ± 0.05 RU) and adenine nucleotide transporter (0.61 ± 0.11 vs. 0.22 ± 0.05 RU), as well as mitochondrial DNA content (530 ± 12 μg DNA/106 cells vs. 307 ± 9 μg DNA/106 cells in control). TGF-β1 treatment was associated with an increase in mitochondrial function with a twofold increase in baseline oxygen consumption rate (2.25 ± 0.03 vs. 1.13 ± 0.1 nmol O2/min/106 cells) and FCCP-induced mitochondrial respiration (2.87 ± 0.03 vs. 1.46 ± 0.15 nmol O2/min/106 cells). Conclusions TGF-β1 induced differentiation of fibroblasts is accompanied by energetic remodeling of myofibroblasts with an increase in mitochondrial respiration and mitochondrial content.

Background: HMG-CoA reductase inhibitors (statins) have been shown to reduce the incidence of atrial fibrillation (AF) and its progression but the underlying mechanisms are not fully elucidated. Since atrial fibrosis plays a major role in the development of the substrate for AF progression, we hypothesized that statins antagonize the effect of profibrotic cytokines, reducing their stimulatory effect on fibroblast proliferation, differentiation and activation. Methods: The effect of TGF-β1, a major profibrotic cytokine, on fibroblast proliferation and activation of myofibroblasts was assessed by expression of alpha smooth muscle actin (α-SMA) message (qPCR) and proteins (western and immunofluorocytochemistry) in the presence and absence of simvastatin (1-10μM). The inhibitory effect of simvastatin on SMAD 2/3 phosphorylation (western) and its nuclear translocation by TGF-β1 (5ng) was determined by immunofluorescence antibodies using fluorescent microscopy. Results: TGF-β1 treatment increased fibroblast proliferation (cell count) by 63% compared to control (p Conclusion: Simvastatin inhibits TGFβ-1-mediated cardiac fibroblast proliferation and myofibroblast differentiation by antagonizing SMAD phosphorylation and its translocation into the nucleus.

Introduction: Atrial fibrosis alters myocardial electrophysiological properties, increasing susceptibility to postoperative atrial fibrillation (PoAF); however, its estimation is problematic. We hypothesized that a noninvasive approach using history of AF (HxAF), LA mechanics and serum biomarkers of collagen turnover provides a surrogate for the extent of interstitial atrial fibrosis to identify patients at risk for PoAF. Methods: In patients undergoing cardiac surgery from April-Dec 2013, concentrations of biomarkers reflecting collagen synthesis/degradation and extracellular matrix remodeling were determined in serum from preoperative blood using an enzyme-linked immunosorbent assay, and echocardiographic evaluation was performed using M-mode, 2D, Doppler and 3D speckle tracking. Results: Of 66 patients (68 ±11 y, 67% men), 15 had HxAF and 11 of 51 with no HxAF (22%) developed new onset PoAF. In patients with HxAF, biomarkers for collagen turnover were elevated (Fig A) and correlated with a reduction in LA ejection fraction and global and regional relaxation of the LA wall (p=0.01, Fig B). In patients with no HxAF, procollagen type III (PIIINP) was significantly different in those who developed PoAF (p=0.01) and correlated with reduction in contractility in the posterior LA roof (p= Conclusion: Surrogate serum and imaging biomarkers correlate with the substrate abnormality that promotes AF. These results need to be validated in larger cohorts to assess the power of these parameters in predicting new onset PoAF.

Introduction: Cardiac injury results in the death of cardiac myocytes and subsequent scar formation through extracellular matrix (ECM) deposition by fibroblasts (FB) and myofibroblasts (myoFB). Excessive fibrosis results in pathological scarring that predisposes to arrhythmogenesis and heart failure, particularly in the elderly. Strategies to limit adverse ECM remodeling are urgently needed to curtail the growing epidemic of atrial fibrillation and heart failure in the aging population. Persistence of myoFB and resistance to apoptotic cell death has been proposed to underlie the mechanism of excessive fibrosis, yet is not fully characterized. Methods: Cultured NIH/3T3 cells (control and TGF-β1 treated) have been challenged with activators of extrinsic (FAS-Ligand, 1 μg/mL) or intrinsic (Thapsigargin 10 μM and Staurosporine 5 μM) apoptotic pathways and Caspase-3 activity was measured in cellular lysate. Results: FAS-L exposure induced ~40-fold suppression of Caspase-3 activity in TGF-β1 treated cells as compared with control (17±12 vs 686±5 nmol AMC/min/106 cells, respectively). Similarly, Staurosporine activated Caspase-3 in TGF-β1 treated cells ~3-fold (171±38 vs 536±29 nmol AMC/min/106 cells), and Thapsigargin ~10-fold (73±33 vs 742±8 nmol AMC/min/106 cells). Conclusion: TGF-β1 treatment increased the sensitivity of NIH/3T3 cells toward extrinsic and intrinsic apoptotic stimuli. Although, TGF-β1 treatment increased overall resistance of NIH/3T3 cells to apoptosis, the responsiveness of cells to extrinsic vs intrinsic pathways was differentially affected. This data support the hypothesis that persistence of myoFB results in pathological scarring.

Background: Type II diabetes mellitus is a major health problem contributing to increased morbidity and mortality with associated cardiovascular diseases. Metformin, an oral antidiabetic agent, has cardioprotective properties independent of their glucose lowering effect; however, mechanisms underlying cardioprotection remain poorly defined. We hypothesized that the cardioprotective effect of metformin appears to be associated with inhibition of mitochondrial permability transition pore (mPTP) that could be beneficial in diabetic hearts with attenuated endogenous cardioprotective responses. Purpose: The aim of the study was to determine the protective effect of metformin on mPTP opening in mitochondria from human myocardium.. Methods: Mitochondria freshly isolated from the left atrial appendage of nondiabetic patients undergoing cardiac surgery were loaded with calcium- (fluo-3) and membrane potential-sensitive (Safranin-O) fluorescent dyes and challenged with sequential pulses of Ca2+ (10 μM every 3 m) in the absence and presence of different concentrations of metformin (2.5, 5, 10 mM). The sensitivity of mitochondria toward mPTP opening was assessed by abrupt release of mitochondrial Ca2+ (fluo-5N fluorescence), with simultaneous dissipation of mitochondrial membrane potential (safranin O fluorescence) and mitochondrial swelling (decrease in light scattering). Results: Metformin caused a dose-dependent inhibition of Ca2+-induced mPTP opening with delayed mitochondrial Ca2+ release, depolarization and swelling. The tolerance of metformin-treated mitochondria to Ca2+-induced mPTP opening when compared to controls was increased from 457±71 to 600±74 nmol/mg protein at 2.5mM, 674±10 nmol/mg protein at 5 mM and 750±77 nmol/mg protein at 10 mM. Cyclosporin A (1 μM), a known mPTP inhibitor, has marginal incremental effect on metformin-induced inhibition of mPTP opening. Conclusion: In human cardiac mitochondria, metformin inhibited calcium-overload-mediated mPTP opening that otherwise leads to mitochondrial energetic failure and cell death. Thus, metformin may help restore attenuated cardioprotection in diabetic hearts by increasing tolerance to stress-induced mPTP opening and, thus, preventing cell death.

This article presents the results of comprehensive research the migration situation in the region and the practices of migration management in the framework of risk theory within modern society studies. The key target group of the study are the migrants who have arrived to the region within the Federal Repatriation Programme. The work is based on numerous expert interviews of migration officials. The article analyses written queries to regional ministries on the assessment of local recruiting needs and the opportunities for the arrival and adaptation of compatriots. The authors discuss migration and economic statistics, and propose a forecast for human resources development with and without taking accounting for the migration. The article identifies both the opportunities relating to the implementation of the Federal Repatriation Programme in the Kaliningrad region in view of the current social and economic situation and the risks associated with the first stage of the programme implementation (2007—2013). Possible migration risks are considered from the perspective of cultural studies and management research.

Cardiac chamber-specific differences in the responsiveness of fibroblasts to pathogenic stimuli have been described in animal models, but it is unclear if disease states affect the structure and function of fibroblasts, especially in the human heart. Fibroblasts from human atrial appendage tissue

The diabetic heart exhibits a reduced tolerance to metabolic stress resulting in higher susceptibility to injury and heart failure yet the underlying mechnisms of reduced tolerance are not fully defined. We hypothesized that impairment in oxidative phosphorylation (OXPHOS) and increased oxidative