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Scarring and remodeling of the left ventricle (LV) after myocardial infarction (MI) results in ischemic cardiomyopathy with reduced contractile function. Regional differences related to persisting ischemia may exist. We investigated the hypothesis that mitochondrial function and structure is altered in the myocardium adjacent to MI with reduced perfusion (MIadjacent) and less so in the remote, nonischemic myocardium (MIremote). We used a pig model of chronic coronary stenosis and MI (n = 13). Functional and perfusion MR imaging 6 wk after intervention showed reduced ejection fraction and increased global wall stress compared with sham-operated animals (Sham; n = 14). Regional strain in MIadjacent was reduced with reduced contractile reserve; in MIremote strain was also reduced but responsive to dobutamine and perfusion was normal compared with Sham. Capillary density was unchanged. Cardiac myocytes isolated from both regions had reduced basal and maximal oxygen consumption rate, as well as through complex I and II, but complex IV activity was unchanged. Reduced respiration was not associated with detectable reduction of mitochondrial density. There was no significant change in AMPK or glucose transporter expression levels, but glycogen content was significantly increased in both MIadjacent and MIremote. Glycogen accumulation was predominantly perinuclear; mitochondria in this area were smaller but only in MIadjacent where also subsarcolemmal mitochondria were smaller. In conclusion, after MI reduction of mitochondrial respiration and glycogen accumulation occur in all LV regions suggesting that reduced perfusion does not lead to additional specific changes and that increased hemodynamic load is the major driver for changes in mitochondrial function. [ABSTRACT FROM AUTHOR]

Reducing the open probability of the ryanodine receptor (RyR) has been proposed to have beneficial effects in heart failure. We investigated whether conditional FKBP12.6 overexpression at the time of myocardial infarction (MI) could improve cardiac remodelling and cell Ca2+ handling. Wild-type (WT) mice and mice overexpressing FKBP12.6 (Tg) were studied on average 7.5 ± 0.2 weeks after MI and compared with sham-operated mice for in vivo, myocyte function and remodelling. At baseline, unloaded cell shortening in Tg was not different from WT. The [Ca2+]i transient amplitude was similar, but sarcoplasmic reticulum (SR) Ca2+ content was larger in Tg, suggesting reduced fractional release. Spontaneous spark frequency was similar despite the increased SR Ca2+ content, consistent with a reduced RyR channel open probability in Tg. After MI, left ventricular dilatation and myocyte hypertrophy were present in both groups, but more pronounced in Tg. Cell shortening amplitude was unchanged with MI in WT, but increased with MI in Tg. The amplitude of the [Ca2+]i transient was not affected by MI in either genotype, but time to peak was increased; this was most pronounced in Tg. The SR Ca2+ content and Na+- Ca2+ exchanger function were not affected by MI. Spontaneous spark frequency was increased significantly after MI in Tg, and larger than in WT (at 4 Hz, 2.6 ± 0.4 sparks (100 μm)−1 s−1 in Tg MI versus 1.6 ± 0.2 sparks (100 μm)−1 s−1 in WT MI; P < 0.05). We conclude that FKPB12.6 overexpression can effectively reduce RyR open probability with maintained cardiomyocyte contraction. However, this approach appears insufficient to prevent and reduce post-MI remodelling, indicating that additional pathways may need to be targeted. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated the effects of 17β-estradiol (E2) on gene regulation in human cardiac tissues. We hypothesized that a candidate E2 effect is cardiomyocyte (CM)- and sex-specific, conserved between humans and mice, and that E2 impairs contractile function in male CMs only. Background: Both men and women produce E2 locally from androgenic precursors. E2 regulates cardiovascular function, but specific mechanisms, protective or harmful, are not fully understood. Methods: We performed genome-wide expression profiling of E2-treated cardiac tissues from men and women, and studied gene expression and function in CMs from hearts of male and female E2-treated mice. Results: We found 36 E2-dependent genes regulated in a sex-specific manner. Of these, after E2 exposure, the myosin regulatory light chain interacting protein (MYLIP) gene was induced in tissues of men only. Focusing on Mylip and employing isolated mouse CMs, we confirmed our hypotheses that the E2 effect is CM- and sex-specific and conserved between humans and mice. The E2-treatment led to impaired contractile function in male CMs only, which was characterized by increased Mylip mRNA and protein levels, and decreased myosin regulatory light chain (Mrlc) protein. Our report is the first to our knowledge to show that cardiac Mrlc is an in vivo substrate for Mylip, leading to augmented Mrlc ubiquitination. Of relevance, we found that MYLIP expression levels rise with increasing age in hearts of men. Conclusions: E2 directly influences cardiac gene regulation, and E2 actions may be different between the sexes. Since E2 levels rise in older and/or obese men, pharmacological targeting of MYLIP in men with elevated E2 levels could possibly decrease their risk for the development or progression of cardiovascular disease. [Copyright &y& Elsevier]

Aims: Exercise started early after myocardial infarction (MI) improves in vivo cardiac function and myofilament responsiveness to Ca2+. We investigated whether this represents partial or complete reversal of cellular remodelling. Methods and results: Mice with MI following left coronary ligation were given free access to a running wheel (MIEXE, N = 22) or housed sedentary (MISED, N = 18) for 8 weeks and compared with sedentary sham-operated animals (SHAM, N = 11). Myocytes were enzymatically isolated from the non-infarcted left ventricle. Myocytes in MI were significantly longer and even more so with exercise (165 ± 3 μm in MIEXE vs. 148 ± 3 μm in MISED and 136 ± 2 μm in SHAM; P < 0.05, mean ± SEM); cell width was not different. Contraction was measured during electrical field stimulation at 1, 2, and 4 Hz. Unloaded cell shortening was significantly reduced in MISED (at 1 Hz, L/L0=4.4 ± 0.3% vs. 6.7 ± 0.4% in SHAM; P < 0.05, also at 2 and 4 Hz). Exercise restored cell shortening to SHAM values (MIEXE, L/L0=6.4 ± 0.5%). Membrane currents and [Ca2+]i were measured via whole-cell patch clamping, with Fluo-3 as Ca2+ indicator, all at 30°C. Ca2+ transient amplitude, ICaL and sarcoplasmic reticulum Ca2+ content were not different between the three groups. Diastolic Ca2+ levels at 4 Hz were significantly elevated in MISED only, with a trend to increased spontaneous Ca2+ release events (sparks). Action potential duration was increased and transient outward K+ currents significantly reduced after MI; this was unaffected by exercise. Conclusions: Early voluntary exercise training after MI restores cell contraction to normal values predominantly because of changes in the myofilament Ca2+ response and has a beneficial effect on diastolic Ca2+ handling. However, the beneficial effect is not a complete reversal of remodelling as hypertrophy and loss of repolarizing K+ currents are not affected. [ABSTRACT FROM PUBLISHER]

In the cardiac dyad, sarcolemmal L-type Ca2+ channels (LCCs) and sarcoplasmic reticulum (SR) Ca2+ release channels (RyR) are structurally in close proximity. This organization provides for an efficient functional coupling, tuning SR Ca2+ release for optimal contraction of the myocyte. Given that LCC are regulated by the prevailing [Ca2+], this structural organization is the setting for feedback mechanisms and crosstalk. A defective coupling of Ca2+ influx via LCC to activation of RyR has been implicated in reduced SR Ca2+ release in heart failure. Both functional changes in LCC properties and structural re-organization of LCC in T-tubules could be involved. LCC are regulated by cytosolic Ca2+, and crosstalk with SR Ca2+ handling occurs on a long-term basis, i.e. during steady-state changes in heart rate, on an intermediate-term basis, i.e. on a beat-to-beat basis during sudden rate changes, and on a very short- or immediate-term basis, i.e. during a single heartbeat. We review the properties and consequences of these different feedback mechanisms and the changes in heart failure and cardiac hypertrophy that have thus far been studied. [ABSTRACT FROM PUBLISHER]

Objectives: During cardiac excitation–contraction coupling, Ca2+ release from the sarcoplasmic reticulum (SR) occurs at the junctional complex with the T-tubules, containing the L-type Ca2+ channels. A partial loss of T-tubules has been described in myocytes from failing canine and human hearts. We examined how graded reduction of T-tubule density would affect the synchrony of Ca2+ release. Methods: Adult pig ventricular myocytes were isolated and cultured for 24 and 72 h. T-tubules, visualized with di-8-ANEPPS, and [Ca2+]i transients (Fluo-3) were recorded during confocal line scan imaging. Results: Cultured cardiomyocytes exhibited a progressive reduction in T-tubule density. [Ca2+]i transients showed small areas of delayed Ca2+ release which gradually increased in number and size with loss of T-tubules. Local [Ca2+]i transients in the delayed regions were reduced. Due to these changes, loss of T-tubules resulted in an overall slowing of the rise of [Ca2+] along the entire line scan and transient magnitude tended to be reduced, but there was no change in SR Ca2+ content. Human myocytes isolated from failing hearts had a T-tubule density comparable to that of freshly isolated pig myocytes. The size, but not the number, of delayed release areas tended to be larger. The overall rate of rise of [Ca2+]i was significantly faster than in pig myocytes with low T-tubule density. Conclusions: Loss of T-tubules reduces the synchrony of SR Ca2+ release. This could contribute to reduced efficiency of excitation–contraction coupling in heart failure, though dyssynchrony in human failing cells appears to be modest. [Copyright &y& Elsevier]

Chronically increased levels of high molecular weight advanced glycation end products (HMW-AGEs) are known to induce cardiovascular dysfunction. Whether an acute increase in HMW-AGE levels affects vascular function remains unknown. In this study, we examined whether acute exposure to HMW-AGEs disturbs aortic vasomotor function. Aortae were obtained from healthy male rats and were acutely pre-treated with HMW-AGEs in organ baths. Aortic relaxation responses to cumulative doses of acetylcholine (ACh), in the presence or absence of superoxide dismutase (SOD), were measured after precontraction with phenylephrine (PE). Furthermore, levels of 3-nitrotyrosine were evaluated on aortic paraffine sections. In our study, we show that acute exposure to HMW-AGEs significantly decreases the aortic relaxation response to ACh. SOD pre-treatment prevents acute HMW-AGEs-induced impairment by limiting superoxide formation. In conclusion, our data demonstrate that acute exposure to HMW-AGEs causes adverse vascular remodelling, characterised by disturbed vasomotor function due to increased oxidative stress. These results create opportunities for future research regarding the acute role of HMW-AGEs in cardiovascular dysfunction. [ABSTRACT FROM AUTHOR]

Individuals with type 2 diabetes mellitus (T2DM) are at an increased risk for heart failure, yet preventive cardiac care is suboptimal in this population. Pyridoxamine (PM), a vitamin B6 analog, has been shown to exert protective effects in metabolic and cardiovascular diseases. In this study, we aimed to investigate whether PM limits adverse cardiac remodeling and dysfunction in rats who develop T2DM. Male rats received a standard chow diet or Western diet (WD) for 18 weeks to induce prediabetes. One WD group received additional PM (1 g/L) via drinking water. Glucose tolerance was assessed with a 1 h oral glucose tolerance test. Cardiac function was evaluated using echocardiography and hemodynamic measurements. Histology on left ventricular (LV) tissue was performed. Treatment with PM prevented the increase in fasting plasma glucose levels compared to WD-fed rats (p < 0.05). LV cardiac dilation tended to be prevented using PM supplementation. In LV tissue, PM limited an increase in interstitial collagen deposition (p < 0.05) seen in WD-fed rats. PM tended to decrease 3-nitrotyrosine and significantly lowered 4-hydroxynonenal content compared to WD-fed rats. We conclude that PM alleviates interstitial fibrosis and oxidative stress in the hearts of WD-induced prediabetic rats. [ABSTRACT FROM AUTHOR]

Microglia activity can drive excessive synaptic loss during the prodromal phase of Alzheimer's disease (AD) and is associated with lowered cyclic adenosine monophosphate (cAMP) due to cAMP phosphodiesterase 4B (PDE4B). This study aimed to investigate whether long-term inhibition of PDE4B by A33 (3 mg/kg/day) can prevent synapse loss and its associated cognitive decline in APPswe/PS1dE9 mice. This model is characterized by a chimeric mouse/human APP with the Swedish mutation and human PSEN1 lacking exon 9 (dE9), both under the control of the mouse prion protein promoter. The effects on cognitive function of prolonged A33 treatment from 20 days to 4 months of age, was assessed at 7–8 months. PDE4B inhibition significantly improved both the working and spatial memory of APPswe/PSdE9 mice after treatment ended. At the cellular level, in vitro inhibition of PDE4B induced microglial filopodia formation, suggesting that regulation of PDE4B activity can counteract microglia activation. Further research is needed to investigate if this could prevent microglia from adopting their 'disease-associated microglia (DAM)' phenotype in vivo. These findings support the possibility that PDE4B is a potential target in combating AD pathology and that early intervention using A33 may be a promising treatment strategy for AD. [ABSTRACT FROM AUTHOR]

Doxorubicin (DOX) is commonly used in cancer treatment but associated with cardiotoxicity. Pyridoxamine (PM), a vitamin B6 derivative, could be a cardioprotectant. This study investigated the effect of PM on DOX cardiotoxicity and DOX antitumor effectiveness. Sprague Dawley rats were treated intravenously with DOX (2 mg/kg/week) or saline over eight weeks. Two other groups received PM via oral intake (1 g/L in water bottles) next to DOX or saline. Echocardiography was performed after eight weeks. PM treatment significantly attenuated the DOX-induced reduction in left ventricular ejection fraction (72 ± 2% vs. 58 ± 3% in DOX; p < 0.001) and increase in left ventricular end-systolic volume (0.24 ± 0.02 µL/cm2 vs. 0.38 ± 0.03 µL/cm2 in DOX; p < 0.0001). Additionally, LA7 tumor cells were exposed to DOX, PM, or DOX and PM for 24 h, 48 h, and 72 h. Cell viability, proliferation, cytotoxicity, and apoptosis were assessed. DOX significantly reduced LA7 cell viability and proliferation (p < 0.0001) and increased cytotoxicity (p < 0.05) and cleaved caspase-3 (p < 0.001). Concomitant PM treatment did not alter the DOX effect on LA7 cells. In conclusion, PM attenuated DOX-induced cardiomyopathy in vivo without affecting the antitumor effect of DOX in vitro, highlighting PM as a promising cardioprotectant for DOX-induced cardiotoxicity. [ABSTRACT FROM AUTHOR]

Advanced glycation end products (AGEs) are a group of proteins and lipids becoming glycated and oxidized after persistent contact with reducing sugars or short-chain aldehydes with amino group and/or high degree of oxidative stress. The accumulation of AGEs in the body is a natural process that occurs with senescence, when the turnover rate of proteins is reduced. However, increased circulating AGEs have been described to arise at early lifetime and are associated with adverse outcome and survival, in particular in settings of cardiovascular diseases. AGEs contribute to the development of cardiac dysfunction by two major mechanisms: cross-linking of proteins or binding to their cell surface receptor. Recently, growing evidence shows that high-molecular weight AGEs (HMW-AGEs) might be as important as the characterized low-molecular weight AGEs (LMW-AGEs). Here, we point out the targets of AGEs in the heart and the mechanisms that lead to heart failure with focus on the difference between LMW-AGEs and the less characterized HMW-AGEs. As such, this review is a compilation of relevant papers in the form of a useful resource tool for researchers who want to further investigate the role of HMW-AGEs on cardiac disorders and need a solid base to start on this specific topic. [ABSTRACT FROM AUTHOR]

Background The development of heart failure (HF) secondary to hypertension is a complex process related to a series of physiological and molecular factors including glucose dysregulation. The overall objective of this study was to investigate whether exercise training could improve cardiac function and insulin resistance in a rat model of hypertensive HF. Methods Seven week old Dahl salt-sensitive rats received either 8% NaCl (n = 30) or 0.3% NaCl (n = 18) diet. After a 5-week diet, animals were randomly assigned to exercise training (treadmill running at 18 m/min, 5% inclination for 60 min, 5 days/week) or kept sedentary for 6 additional weeks. 2D echocardiography was used to calculate left ventricular (LV) dimensions, volumes and global functional parameters. LV global deformation parameters were measured with speckle tracking echocardiography. Insulin resistance was assessed using 1 h oral glucose tolerance testing. Results High salt diet led to cardiac hypertrophy and HF, characterized by increased wall thicknesses and LV volumes as well as reduced deformation parameters. In addition, high salt diet was associated with the development of insulin resistance. Exercise training improved cardiac function, reduced the extent of interstitial fibrosis and reduced insulin levels 60 min post-glucose administration. Conclusions Even if not fully reversed, exercise training in HF animals improved cardiac function and insulin resistance. Adjusted modalities of exercise training might offer new insights not only as a preventive strategy, but also as a treatment for HF patients. [ABSTRACT FROM AUTHOR]

Purpose: Exercise training improves exercise capacity in type 2 diabetes mellitus (T2DM). It remains to be elucidated whether such improvements result from cardiac or peripheral muscular adaptations, and whether these are intensity dependent. Methods: 27 patients with T2DM [without known cardiovascular disease (CVD)] were randomized to high-intensity interval training (HIIT, n = 15) or moderate-intensity endurance training (MIT, n = 12) for 24 weeks (3 sessions/week). Exercise echocardiography was applied to investigate cardiac output (CO) and oxygen (O2) extraction during exercise, while exercise capacity [( V ˙ O 2 peak (mL/kg/min)] was examined via cardiopulmonary exercise testing at baseline and after 12 and 24 weeks of exercise training, respectively. Changes in glycaemic control (HbA1c and glucose tolerance), lipid profile and body composition were also evaluated. Results: 19 patients completed 24 weeks of HIIT (n = 10, 66 ± 11 years) or MIT (n = 9, 61 ± 5 years). HIIT and MIT similarly improved glucose tolerance (pTime = 0.001, pInteraction > 0.05), V ˙ O 2 peak (mL/kg/min) (pTime = 0.001, pInteraction > 0.05), and exercise performance (Wpeak) (pTime < 0.001, pInteraction > 0.05). O2 extraction increased to a greater extent after 24 weeks of MIT (56.5%, p1 = 0.009, pTime = 0.001, pInteraction = 0.007). CO and left ventricular longitudinal strain (LS) during exercise remained unchanged (pTime > 0.05). A reduction in HbA1c was correlated with absolute changes in LS after 12 weeks of MIT (r = − 0.792, p = 0.019, LS at rest) or HIIT (r = − 0.782, p = 0.038, LS at peak exercise). Conclusion: In patients with well-controlled T2DM, MIT and HIIT improved exercise capacity, mainly resulting from increments in O2 extraction capacity, rather than changes in cardiac output. In particular, MIT seemed highly effective to generate these peripheral adaptations. Trial Registration: NCT03299790, initially released 09/12/2017. [ABSTRACT FROM AUTHOR]

Cardiomyocytes from failing hearts exhibit reduced levels of the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA) and/or increased activity of the endogenous SERCA inhibitor phospholamban. The resulting reduction in the Ca2+ affinity of SERCA impairs SR Ca2+ cycling in this condition. We have previously investigated the physiological impact of increasing the Ca2+ affinity of SERCA by substituting SERCA2a with the higher affinity SERCA2b pump. When phospholamban was also ablated, these double knockouts (DKO) exhibited a dramatic reduction in total SERCA levels, severe hypertrophy, and diastolic dysfunction. We presently examined the role of cardiomyocyte Ca2+ homeostasis in both functional and structural remodeling in these hearts. Despite the low SERCA levels in DKO, we observed near-normal Ca2+ homeostasis with rapid Ca2+ reuptake even at high Ca2+ loads and stimulation frequencies. Well-preserved global Ca2+ homeostasis in DKO was paradoxically associated with marked activation of the Ca2+- dependent nuclear factor of activated T-cell-calcineurin pathway known to trigger hypertrophy. No activation of the MAP kinase signaling pathway was detected. These findings suggest that local changes in Ca2+ homeostasis may play an important signaling role in DKO, perhaps due to reduced microdomain Ca2+ buffering by SERCA2b. Furthermore, alterations in global Ca2+ homeostasis can also not explain impaired in vivo diastolic function in DKO. Taken together, our results suggest that normalizing global cardiomyocyte Ca2+ homeostasis does not necessarily protect against hypertrophy and heart failure development and that excessively increasing SERCA Ca2+ affinity may be detrimenta. [ABSTRACT FROM AUTHOR]

Alterations in RyR2 function have been proposed as a major pathophysiological mechanism of arrhythmias and heart failure (HF). Cardiac FKBP12.6 overexpression protects against myocardial infarction-induced HF and catecholamine-promoted ventricular arrhythmias. We tested the hypothesis that FKBP12.6 overexpression protects against maladaptive LVH and triggered ventricular arrhythmias following transverse aorta constriction (TAC) in the mouse. The TAC-associated mortality rate was significantly lower in male transgenic (DT) than in Ctr mice ( p < 0.05). TAC-associated maladaptive hypertrophy was blunted in DT mice especially 1 month post-TAC and their SERCA2a/PLB ratio remained unchanged 1 and 2 months post-TAC. Two months after TAC, trains of 30 stimuli (burst pacing) performed following isoproterenol injection (0.2 mg/kg, ip), induced VT in 50% of the TAC-Ctr and in none of the TAC-DT mice ( p = 0.022). The increase in myocyte shortening and Ca spark frequency observed in sham-operated Ctr mice in response to 50 nM isoproterenol was reduced in DT mice, and abolished in TAC-DT mice. NCX1 function was reduced in Sham-DT and TAC-DT compared with Sham-Ctr and TAC-Ctr mice, respectively ( p < 0.05 for the 2 comparisons). In mice killed after isoproterenol injection and burst pacing, RyR2 S2814 phosphorylation was decreased by 50% in TAC-DT versus TAC-Ctr mice ( p < 0.05), with no change in RyR2 S2808 and PLB S16 and T17 phosphorylation. Cardiac FKBP12.6 overexpression in the mouse blunts pressure overload-induced maladaptive LV remodelling and protects against catecholamine-promoted burst pacing-induced ventricular tachycardia by decreasing cardiac sensitivity to adrenergic stress and RyR2 S2814 phosphorylation, and decreasing NCX1 activity. [ABSTRACT FROM AUTHOR]

Abstract: N-(p-amylcinnamoyl)anthranilic acid (ACA), a phospholipase A2 (PLA2) inhibitor, is structurally-related to non-steroidal anti-inflammatory drugs (NSAIDs) of the fenamate group and may also modulate various ion channels. We used the whole-cell, patch-clamp technique at room temperature to investigate the effects of ACA on the Ca2+-activated chloride current (I Cl(Ca)) and other chloride currents in isolated pig cardiac ventricular myocytes. ACA reversibly inhibited I Cl(Ca) in a concentration-dependent manner (IC50 =4.2μM, nHill =1.1), without affecting the L-type Ca2+ current. Unlike ACA, the non-selective PLA2 inhibitor bromophenacyl bromide (BPB; 50μM) had no effect on I Cl(Ca). In addition, the analgesic NSAID structurally-related to ACA, diclofenac (50μM) also had no effect on I Cl(Ca), whereas the current in the same cells could be suppressed by chloride channel blockers flufenamic acid (FFA; 100μM) or 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS;100μM). Besides I Cl(Ca), ACA (50μM) also suppressed the cAMP-activated chloride current, but to a lesser extent. It is proposed that the inhibitory effects of ACA on I Cl(Ca) are PLA2-independent and that the drug may serve as a useful tool in understanding the nature and function of cardiac anion channels. [ABSTRACT FROM AUTHOR]

Background and Purpose: The development of myocardial fibrosis is a major complication of Type 2 diabetes mellitus (T2DM), impairing myocardial deformation and, therefore, cardiac performance. It remains to be established whether abnormalities in longitudinal strain (LS) exaggerate or only occur in well-controlled T2DM, when exposed to exercise and, therefore, cardiac stress. We therefore studied left ventricular LS at rest and during exercise in T2DM patients vs. healthy controls.Methods and Results: Exercise echocardiography was applied with combined breath-by-breath gas exchange analyses in asymptomatic, well-controlled (HbA1c: 6.9 ± 0.7%) T2DM patients (n = 36) and healthy controls (HC, n = 23). Left ventricular LS was assessed at rest and at peak exercise. Peak oxygen uptake (V̇O2peak) and workload (Wpeak) were similar between groups (p > 0.05). Diastolic (E, e's, E/e') and systolic function (left ventricular ejection fraction) were similar at rest and during exercise between groups (p > 0.05). LS (absolute values) was significantly lower at rest and during exercise in T2DM vs. HC (17.0 ± 2.9% vs. 19.8 ± 2% and 20.8 ± 4.0% vs. 23.3 ± 3.3%, respectively, p < 0.05). The response in myocardial deformation (the change in LS from rest up to peak exercise) was similar between groups (+ 3.8 ± 0.6% vs. + 3.6 ± 0.6%, in T2DM vs. HC, respectively, p > 0.05). Multiple regression revealed that HDL-cholesterol, fasted insulin levels and exercise tolerance accounted for 30.5% of the variance in response of myocardial deformation in the T2DM group (p = 0.002).Conclusion: Myocardial deformation is reduced in well-controlled T2DM and despite adequate responses, such differences persist during exercise.Trial Registration: NCT03299790, initially released 09/12/2017. [ABSTRACT FROM AUTHOR]

Stem cell-based regenerative therapies hold great promises to treat a wide spectrum of diseases. However, stem cell engraftment and survival are still challenging due to an unfavorable transplantation environment. Advanced glycation end-products (AGEs) can contribute to the generation of these harmful conditions. AGEs are a heterogeneous group of glycated products, nonenzymatically formed when proteins and/or lipids become glycated and oxidized. Our typical Western diet as well as cigarettes contain high AGEs content. AGEs are also endogenously formed in our body and accumulate with senescence and in pathological situations. Whether AGEs have an impact on stem cell viability in regenerative medicine remains unclear, and research on the effect of AGEs on stem cell proliferation and apoptosis is still ongoing. Therefore, this systematic review provides a clear overview of the effects of glycated proteins on cell viability in various types of primary isolated stem cells used in regenerative medicine. [ABSTRACT FROM AUTHOR]

Growing evidence supports the role of advanced glycation end products (AGEs) in the development of diabetic vascular complications and cardiovascular diseases (CVDs). We have shown that high-molecular-weight AGEs (HMW-AGEs), present in our Western diet, impair cardiac function. Whether HMW-AGEs affect vascular function remains unknown. In this study, we aimed to investigate the impact of chronic HMW-AGEs exposure on vascular function and structure. Adult male Sprague Dawley rats were daily injected with HMW-AGEs or control solution for 6 weeks. HMW-AGEs animals showed intracardiac pressure overload, characterized by increased systolic and mean pressures. The contraction response to PE was increased in aortic rings from the HMW-AGEs group. Relaxation in response to ACh, but not SNP, was impaired by HMW-AGEs. This was associated with reduced plasma cyclic GMP levels. SOD restored ACh-induced relaxation of HMW-AGEs animals to control levels, accompanied by a reduced half-maximal effective dose (EC50). Finally, collagen deposition and intima-media thickness of the aortic vessel wall were increased with HMW-AGEs. Our data demonstrate that chronic HMW-AGEs exposure causes adverse vascular remodelling. This is characterised by disturbed vasomotor function due to increased oxidative stress and structural changes in the aorta, suggesting an important contribution of HMW-AGEs in the development of CVDs. [ABSTRACT FROM AUTHOR]

Background/Aims: High-molecular-weight advanced glycation end-products (HMW-AGEs) are abundantly present in our Western diet. There is growing evidence reporting that HMWAGEs contribute to the development of cardiovascular dysfunction in vivo, next to the wellknown low-molecular-weight AGEs. The goal of our study is to assess the ultrastructure and function of cardiomyocytes after chronic exposure to HMW-AGEs. A better understanding of underlying mechanisms is essential to create new opportunities for further research on the specific role of HMW-AGEs in the development and progression of cardiovascular diseases. Methods: Adult male rats were randomly assigned to daily intraperitoneal injection for six weeks with either HMW-AGEs (20 mg/kg/day) or a control solution. Hemodynamic measurements were performed at sacrifice. Single cardiomyocytes from the left ventricle were obtained by enzymatic dissociation through retrograde perfusion of the aorta. Unloaded cell shortening, time to peak and time to 50% relaxation were measured during field stimulation and normalized to diastolic length. L-type Ca2+ current density (ICaL) and steady-state inactivation of ICaL were measured during whole-cell ruptured patch clamp. Myofilament functional properties were measured during whole-cell ruptured patch clamp. Myofilament functional properties were measured in membrane-permeabilized cardiomyocytes. Ultrastructural examination of cardiac tissue was performed using electron microscopy. Results: Rats injected with HMW-AGEs displayed in vivo cardiac dysfunction, characterized by significant changes in left ventricular peak rate pressure rise and decline accompanied with an increased heart mass. Single cardiomyocytes isolated from the left ventricle revealed concentric hypertrophy, indicated by the increase in cellular width. Unloaded fractional cell shortening was significantly reduced in cells derived from the HMW-AGEs group and was associated with slower kinetics. Peak L-type Ca2+ current density was significantly decreased in the HMW-AGEs group. L-type Ca2+ channel availability was significantly shifted towards more negative potentials after HMW-AGEs injection. The impact of HMW-AGEs on myofilament function was measured in membrane-permeabilized cardiomyocytes showing a reduction in passive force, maximal Ca2+ activated force and rate of force development. Ultrastructural examination of cardiac tissue demonstrated adverse structural remodeling in HMW-AGEs group characterized by a disruption of the cyto-architecture, a decreased mitochondrial density and altered mitochondrial function. Conclusion: Our data indicate that HMW-AGEs induce structural and functional cellular remodeling via a different working mechanism as the well-known LMW-AGEs. Results of our research open the door for new strategies targeting HMW-AGEs to improve cardiac outcome. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?Does acute exposure to high molecular weight advanced glycation end products (HMW‐AGEs) alter cardiomyocyte contractile function?What is the main finding and its importance?Ventricular cardiomyocytes display reduced Ca2+ influx, resulting in reduced contractile capacity, after acute exposure to HMW‐AGEs, independent of activation of their receptor. Given that HMW‐AGEs are abundantly present in our Western diet, a better understanding of underlying mechanisms, especially in patients already displaying altered cardiac function, should be gained for these compounds. Sustained elevated levels of high molecular weight advanced glycation end products (HMW‐AGEs) are known to promote cardiac dysfunction. Recent data suggest that acutely elevated levels of AGEs occur in situations of increased oxidative stress. Whether this increase might have detrimental effects on cardiac function remains unknown. In this study, we investigated whether acute exposure to HMW‐AGEs affects cardiomyocyte function via activation of their receptor (RAGE) signalling pathway. Single cardiomyocytes from the left ventricle of adult male rats were obtained by enzymatic dissociation through retrograde perfusion of the aorta. Functional experiments were performed in cardiomyocytes pre‐incubated with or without an anti‐RAGE antibody. Unloaded cell shortening and L‐type Ca2+ current amplitude were evaluated in the presence or absence of HMW‐AGEs (200 μg ml−1). Expression of RAGE, c‐Jun N‐terminal kinase (JNK) and phosphorylated JNK (pJNK) were assessed by western blot. Experiments were performed at room temperature. After 4 min application of HMW‐AGEs, unloaded cell shortening was significantly reduced. This impaired contractile function was related to reduced Ca2+ influx. These alterations were also observed in cardiomyocytes pre‐incubated with anti‐RAGE antibody. Our study demonstrates that acute exposure to elevated levels of HMW‐AGEs leads to direct and irreversible cardiomyocyte dysfunction, independent of RAGE activation. [ABSTRACT FROM AUTHOR]

Background: The effect of exercise on cardiac function/structure in type 2 diabetes mellitus (T2DM) with or without diabetic cardiomyopathy (DCM) is not yet completely understood. To date, results of studies have been controversial with variable outcomes due to the variety of exercise modalities.Objectives: The aim of the present review was to examine the impact of exercise intervention, and different types of exercise, on cardiac function and structure in T2DM through a systematic literature review, combining both pre-clinical and clinical studies.Methods: A systematic literature search was performed on PubMed, Web of Science, and PEDro to identify studies up to 2 April 2018. Articles were included when well-defined exercise protocols were provided, and cardiac function in T2DM patients or validated animal models was examined.Results: In diabetic animals, improvements in both diastolic and systolic function through exercise therapy were mainly attributed to reduced collagen deposition. In T2DM patients, improvements were observed in diastolic function, but not consistently in systolic function, after endurance (and combined resistance) exercise training. Different exercise intervention modalities and exercise types seemed equally effective in improving cardiac structure and function.Conclusion: Exercise training elicits significant improvements in diastolic function and beneficial remodeling in T2DM and DCM animal models, but not necessarily improvements in systolic function and left ventricular structure, regardless of exercise type. Therefore, exercise intervention should be a cornerstone in the treatment of T2DM patients not only to improve glycemic control but also to specifically enhance cardiac function. [ABSTRACT FROM AUTHOR]

Diabetes mellitus (DM) is a major problem worldwide. Within this patient group, cardiovascular diseases are the biggest cause of morbidity and mortality. Diabetic cardiomyopathy (DCM) is defined as diabetes-associated structural and functional changes in the myocardium, not directly attributable to other confounding factors such as coronary artery disease or hypertension. Pathophysiology of DCM remains unclear due to a lack of adequate animal models reflecting the current pandemic of diabetes, associated with a high increased sugar intake and the 'Western' lifestyle. The aim of this study was to develop an animal model mimicking this 'Western' lifestyle causing a human-like phenotype of DCM. Twenty-four Sprague-Dawley rats were randomly assigned into a normal or a 'Western' diet group for 18 weeks. Glucose and insulin levels were measured with an OGTT. Heart function was assessed by echocardiography and hemodynamic measurements in vivo. Cardiac fibrosis and inflammation were investigated in vitro. 'Western' diet given to healthy rats for 18 weeks induced hyperglycemia together with increased AGEs levels, insulin levels and hypertriglyceridemia. Heart function was altered with increased end-diastolic pressure, left ventricle hypertrophy. Changes in vivo were associated with increased collagen deposition and increased PAI-1 levels in the heart. High-sugar diet or 'Western' diet causes T2DM and the hallmarks of DCM in rats, reflecting the phenotype of the disease seen in patients. Using this new model of T2DM with DCM might open new insight in understanding the pathophysiology of DCM and on a long term, test targeted therapies for T2DM with DCM patients. [ABSTRACT FROM AUTHOR]

Background Several clinical and experimental studies have demonstrated that advanced glycation end products (AGEs) are associated with adverse cardiac outcome. Growing evidence shows that high molecular weight AGEs (HMW-AGEs) might be as important as the characterized low molecular weight AGEs. To date, the role of HMW-AGEs in the pathogenesis of cardiac remodeling remains unknown. In this study, we investigated whether HMW-AGEs are involved in cardiac dysfunction. Methods Healthy rats were daily ip injected with 20 mg/kg BSA-derived HMW-AGEs or, as a control, unmodified BSA, during 6 weeks. Cardiac function was assessed with echocardiography. Plasma levels of glucose, AGEs and soluble RAGE (sRAGE) were measured. AGEs, RAGE and lysyl oxidase (LOX) expression were determined by western blot. Results After 6 weeks, animals displayed a sustained increase in circulating total AGEs without hyperglycemia. HMW-AGEs injections induced cardiac dysfunction characterized by wall hypertrophy, increased heart sphericity, reduced strain and strain rate with preserved ejection fraction. Plasma sRAGE levels were significantly higher compared to control and correlated significantly with decreased strain. RAGE expression, TNF-α and IL-6 remained unchanged. Finally, HMW-AGEs induced prominent cardiac fibrosis associated with an increased LOX expression. Conclusion Our data demonstrate that rather than via a specific activation of RAGE, the deleterious effects of HMW-AGEs are likely mediated via an increased collagen cross-linking responsible for the observed cardiac stiffness. Additionally, we show that in the setting of elevated HMW-AGEs, increased sRAGE levels are markers of altered cardiac function. [ABSTRACT FROM AUTHOR]

Background This study assessed whether autologous transplantation of cardiac atrial appendage stem cells (CASCs) preserves cardiac function after myocardial infarction (MI) in a minipig model. Methods and results CASCs were isolated from right atrial appendages of Göttingen minipigs based on high aldehyde dehydrogenase activity and expanded. MI was induced by a 2 h snare ligation of the left anterior descending coronary artery. Upon reperfusion, CASCs were intramyocardially injected under NOGA guidance (MI-CASC, n = 10). Non-transplanted pigs (MI, n = 8) received sham treatment. 3D electromechanical mapping (EMM) and cardiac MRI were performed to assess left ventricular (LV) function. MI pigs developed LV dilatation at 2 months (2 M), while in the MI-CASC group volumes remained stable. Global LV ejection fraction decreased by 16 ± 8% in MI animals vs 3 ± 10% in MI-CASC animals and regional wall thickening in border areas was better preserved in the MI-CASC group. EMM showed decreased viability and wall motion in the LV for both groups POST-MI, whereas at 2 M these parameters only improved in the MI-CASC. Substantial cell retention was accompanied by cardiomyogenic differentiation in 98 ± 1% of the transplanted CASCs, which functionally integrated. Second harmonic generation microscopy confirmed the formation of mature sarcomeres in transplanted CASCs. Absence of cardiac arrhythmias indicated the safety of CASC transplantation. Conclusion CASCs preserve cardiac function by extensive engraftment and cardiomyogenic differentiation. Our data indicate the enormous potential of CASCs in myocardial repair. [ABSTRACT FROM AUTHOR]

Recently, a supramolecular model was developed for predicting striated skeletal muscle intensity profiles obtained by label-free second harmonic generation (SHG) microscopy. This model allows for a quantitative determination of the length of the thick filament antiparallel range or M-band (M), and results in M = 0.12 μm for single-band intensity profiles when fixing the A-band length (A) to A = 1.6 μm, a value originating from electron microscopy (EM) observations. Using simulations and experimental data sets, we showed that the objective numerical aperture (NA) and the refractive index (RI) mismatch (Δn = n2ω - nω) between the illumination wave (ω) and the second harmonic wave (2ω) severely affect the simulated sarcomere intensity profiles. Therefore, our recovered filament lengths did not match with those observed by EM. For an RI mismatch of Δn = 0.02 and a moderate illumination NA of 0.8, analysis of single-band SHG intensity profiles with freely adjustable A- and M-band sizes yielded A = 1.40 ± 0.04 μm and M = 0.07 ± 0.05 μm for skeletal muscle. These lower than expected values were rationalized in terms of the myosin density distribution along the myosin thick filament axis. Our data provided new and practical insights for the application of the supramolecular model to study SHG intensity profiles in striated muscle. [ABSTRACT FROM AUTHOR]

Aims Melusin is a muscle-specific chaperone protein whose expression is required for a compensatory hypertrophy response to pressure overload. Here, we evaluated the consequences of melusin overexpression in the setting of myocardial infarction (MI) using a comprehensive multicentre approach. Methods and results Mice overexpressing melusin in the heart (TG) and wild-type controls (WT) were subjected to permanent LAD ligation and both the acute response (Day 3) and subsequent remodelling (2 weeks) were examined. Mortality in wild-type mice was significant between Days 3 and 7, primarily due to cardiac rupture, but melusin's overexpression strongly reduced mortality (43.2% in wild-type vs. 27.3% in melusin-TG, P = 0.005). At Day 3 after MI, a time point preceding the mortality peak, TG hearts had increased heat shock protein 70 expression, increased ERK1/2 signalling, reduced cardiomyocyte hyper-contractility and inflammatory cell infiltrates, and increased matricellular protein expression in the infarcted area. Conclusions Consistent with its function as a chaperone protein, melusin overexpression exerts a dual protective action following MI reducing an array of maladaptive processes. In the early phase after MI, reduced inflammation and myocyte remodelling protect against cardiac rupture. Chronically, reduced myocyte loss and matrix remodelling, with preserved myocyte contractility, confer adaptive LV remodelling. [ABSTRACT FROM AUTHOR]

Rationale: In ventricular myocytes of large mammals, not all ryanodine receptor (RyR) clusters are associated with T-tubules (TTs); this fraction increases with cellular remodeling after myocardial infarction (MI). Objective: To characterize RyR functional properties in relation to TT proximity, at baseline and after MI. Methods: Myocytes were isolated from left ventricle of healthy pigs (CTRL) or from the area adjacent to a myocardial infarction (MI). Ca2+ transients were measured under whole-cell voltage clamp during confocal linescan imaging (fluo-3) and segmented according to proximity of TTs (sites of early Ca2+ release, F>F50 within 20 ms) or their absence (delayed areas). Spontaneous Ca2+ release events during diastole, Ca2+ sparks, reflecting RyR activity and properties, were subsequently assigned to either category. Results: In CTRL, spark frequency was higher in proximity of TTs, but spark duration was significantly shorter. Block of Na+/Ca2+ exchanger (NCX) prolonged spark duration selectively near TTs, while block of Ca2+ influx via Ca2+ channels did not affect sparks properties. In MI, total spark mass was increased in line with higher SR Ca2+ content. Extremely long sparks (>47.6 ms) occurred more frequently. The fraction of near-TT sparks was reduced; frequency increased mainly in delayed sites. Increased duration was seen in near-TT sparks only; Ca2+ removal by NCX at the membrane was significantly lower in MI. Conclusion: TT proximity modulates RyR cluster properties resulting in intracellular heterogeneity of diastolic spark activity. Remodeling in the area adjacent to MI differentially affects these RyR subpopulations. Reduction of the number of sparks near TTs and reduced local NCX removal limit cellular Ca2+ loss and raise SR Ca2+ content, but may promote Ca2+ waves. [ABSTRACT FROM AUTHOR]

Abstract: In the setting of regional ischemia, the “at-risk” myocardium exhibits a flow-related reduction in systolic thickening with a concomitant development of abnormal thickening after aortic valve closure (postsystolic thickening [PST]). With the introduction of high time–resolution ultrasonic-based strain/strain-rate imaging, this short lived phenomenon can be measured accurately in the clinical setting. The mechanisms underlying this ischemia-related PST are poorly understood and both active and passive etiologies have been proposed. This study aims at elucidating the potential mechanisms behind PST in the intact heart. A theoretical model, describing active force development, elasticity and segment interaction has been developed to simulate radial deformation during systole and iso-volumetric relaxation. Simulation results have been compared with experimental deformation curves obtained from postero-basal segments of a pig model undergoing varying controlled ischemic challenges. Three forms of regional ischemia could be simulated by varying the model parameters of the ischemic segments: (i) chronic regional hypo-perfusion (reduced and prolonged active force development; preserved elasticity); (ii) acute short-lived ischemia—temporary vessel occlusion (no active force development; preserved elasticity); and (iii) chronic myocardial infarction (no active force development; decreased elasticity). For all ischemic substrates, the simulated curves closely correlate to the deformation measured in the corresponding porcine models without the need for active force development during the occurrence of PST. This suggests that segment interaction is the key determinant in the development of PST. Thus, in all instances, at the time of its manifestation, ischemia-related PST could be explained in a unified way as a passive phenomenon that was the result of elastic segment interaction. Its occurrence originates from the end-systolic inhomogeneous state where neighboring segments have a different wall thickness. The occurrence of these differences at end-systole depends on the presence of regional differences within the ventricle in the magnitude and duration of the developed contraction force during the first part of systole, the elasticity of the ischemic segment and the left-ventricular pressure. (E-mail: Piet.Claus@med.kuleuven.be) [Copyright &y& Elsevier]

Torsades de pointes (TdP) ventricular tachycardia typically occurs in the setting of early afterdepolarizations; it contributes to arrhythmias and sudden death in congenital and acquired heart disease. Window L-type Ca2+ current ( ICaL) has a central role in the arrhythmogenesis and may be particularly important under β-adrenergic stimulation. We studied the properties of ICaL in myocytes from the dog with chronic atrioventricular block (cAVB) that has cardiac hypertrophy and an increased susceptibility to TdP. Peak ICaL densities at baseline (K+- and Na+-free solutions, 10 mmol l−1[EGTA]pip) in cAVB were comparable to control, but inactivation was shifted to the right, resulting in a larger window current area in cAVB. Under β-adrenergic stimulation, the window current area was increased and shifted to the left, but less so in cAVB (maximum at −27 mV, versus−32 mV in control). ICaL during a step to −35 mV showed a transient reduction immediately after the peak. Test steps to 0 mV, simultaneous recording of [Ca2+]i and manipulation of sarcoplasmic reticulum (SR) Ca2+ release showed that this resulted from inhibition and fast recovery of ICaL with SR Ca2+ release. The extent of this dynamic modulation was larger in cAVB than in control (23 ± 2% of the initially available current, versus 13 ± 3%; P < 0.05). Early afterdepolarizations (EADs) in cAVB myocytes under β-adrenergic stimulation typically occurred in the window current voltage range and after decline of [Ca2+]i. In conclusion, in cAVB, the larger window current, its rightward shift and enhanced dynamic modulation by SR Ca2+ release may contribute to an increased incidence of EADs in cAVB under β-adrenergic stimulation. [ABSTRACT FROM AUTHOR]

Abstract: Reduced Ca2+ release from the sarcoplasmic reticulum (SR) and a negative force–frequency relation characterize end-stage human heart failure. The MLP–/– mouse with dilated cardiomyopathy is used as a model to explore novel therapeutic interventions but the alterations in Ca2+ handling in MLP–/– remain incompletely understood. We studied [Ca2+]i in left ventricular myocytes from MLP–/– and WT mice (3–4 months old; whole-cell voltage clamp, 30 °C). At 1 Hz stimulation, the amplitude of [Ca2+]i transients was similar. However, in contrast to WT, at higher frequencies the [Ca2+]i transient amplitude declined in MLP–/– and there was no increase in SR Ca2+ content. Unexpectedly, the decline of [Ca2+]i was faster in MLP–/– than in WT (at 1 Hz, τ of 80 ± 9 vs. 174 ± 29 ms, P < 0.001) and the frequency-dependent acceleration of the decline was abolished suggesting an enhanced basal SERCA activity. Indeed, the Ca2+ affinity of SR Ca2+ uptake in homogenates was higher in MLP–/–, with the maximal uptake rate similar to WT. Phosphorylation of phospholamban in MLP–/– was increased (2.3-fold at Ser16 and 2.9-fold at the Thr17 site, P < 0.001) with similar SERCA and total phospholamban protein levels. On increasing stimulation frequency to 4 Hz, WT, but not MLP–/–, myocytes had a net gain of Ca2+, suggesting inadequate Ca2+ sequestration in MLP–/–. In conclusion, increased baseline phosphorylation of phospholamban in MLP–/– leads to a reduced reserve for frequency-dependent increase of Ca2+ release. This represents a novel paradigm for altered Ca2+ handling in heart failure, underscoring the importance of phosphorylation pathways. [Copyright &y& Elsevier]

Myocardial infarction (MI) occurs when the coronary blood supply is interrupted. As a consequence, cardiomyocytes are irreversibly damaged and lost. Unfortunately, current therapies for MI are unable to prevent progression towards heart failure. As the renewal rate of cardiomyocytes is minimal, the optimal treatment should achieve effective cardiac regeneration, possibly with stem cells transplantation. In that context, our research group identified the cardiac atrial appendage stem cells (CASCs) as a new cellular therapy. However, CASCs are transplanted into a hostile environment, with elevated levels of advanced glycation end products (AGEs), which may affect their regenerative potential. In this study, we hypothesize that pyridoxamine (PM), a vitamin B6 derivative, could further enhance the regenerative capacities of CASCs transplanted after MI by reducing AGEs' formation. Methods and Results: MI was induced in rats by ligation of the left anterior descending artery. Animals were assigned to either no therapy (MI), CASCs transplantation (MI + CASCs), or CASCs transplantation supplemented with PM treatment (MI + CASCs + PM). Four weeks post-surgery, global cardiac function and infarct size were improved upon CASCs transplantation. Interstitial collagen deposition, evaluated on cryosections, was decreased in the MI animals transplanted with CASCs. Contractile properties of resident left ventricular cardiomyocytes were assessed by unloaded cell shortening. CASCs transplantation prevented cardiomyocyte shortening deterioration. Even if PM significantly reduced cardiac levels of AGEs, cardiac outcome was not further improved. Conclusion: Limiting AGEs' formation with PM during an ischemic injury in vivo did not further enhance the improved cardiac phenotype obtained with CASCs transplantation. Whether AGEs play an important deleterious role in the setting of stem cell therapy after MI warrants further examination. [ABSTRACT FROM AUTHOR]

Background: During myocardial infarction (MI), billions of cardiomyocytes are lost. The optimal therapy should effectively replace damaged cardiomyocytes, possibly with stem cells able to engraft and differentiate into adult functional cardiomyocytes. As such, cardiac atrial appendage stem cells (CASCs) are suitable candidates. However, the presence of elevated levels of advanced glycation end products (AGEs) in cardiac regions where CASCs are transplanted may affect their regenerative potential. In this study, we examine whether and how AGEs alter CASCs properties in vitro. Methods and Results: CASCs in culture were exposed to ranging AGEs concentrations (50 µg/mL to 400 µg/mL). CASCs survival, proliferation, and migration capacity were significantly decreased after 72 h of AGEs exposure. Apoptosis significantly increased with rising AGEs concentration. The harmful effects of these AGEs were partially blunted by pre-incubation with a receptor for AGEs (RAGE) inhibitor (25 µM FPS-ZM1), indicating the involvement of RAGE in the observed negative effects. Conclusion: AGEs have a time- and concentration-dependent negative effect on CASCs survival, proliferation, migration, and apoptosis in vitro, partially mediated through RAGE activation. Whether anti-AGEs therapies are an effective treatment in the setting of stem cell therapy after MI warrants further examination. [ABSTRACT FROM AUTHOR]

Human cardiac stem cells isolated from atrial appendages based on aldehyde dehydrogenase activity (CASCs) can be expanded in vitro and differentiate into mature cardiomyocytes. In this study, we assess whether Wnt activation stimulates human CASC proliferation, whereas Wnt inhibition induces cardiac maturation. CASCs were cultured as described before. Conventional PCR confirmed the presence of the Frizzled receptors. Small-molecule inhibitors (IWP2, C59, XAV939, and IWR1-endo) and activator (CHIR99021) of the Wnt/β -catenin signaling pathway were applied, and the effect on β-catenin and target genes for proliferation and differentiation was assessed by Western blot and RT-qPCR. CASCs express multiple early cardiac differentiation markers and are committed toward myocardial differentiation. They express several Frizzled receptors, suggesting a role for Wnt signaling in clonogenicity, proliferation, and differentiation. Wnt activation increases total and active β-catenin levels. However, this does not affect CASC proliferation or clonogenicity. Wnt inhibition upregulated early cardiac markers but could not induce mature myocardial differentiation. When CASCs are committed toward myocardial differentiation, the Wnt pathway is active and can be modulated. However, despite its role in cardiogenesis and myocardial differentiation of pluripotent stem-cell populations, our data indicate that Wnt signaling has limited effects on CASC clonogenicity, proliferation, and differentiation. [ABSTRACT FROM AUTHOR]

Introduction: Type 2 Diabetes Mellitus (T2DM) is affecting more than 400 million people worldwide and leads to diabetic cardiomyopathy. Exercise intervention is a low cost and safe approach in reducing the adverse effects of diabetic cardiomyopathy. Moderate intensity training (MIT) has been so far the most preferred exercise therapy in the clinic, however high-intensity-interval training (HIIT) is gaining interest as a potentially more efficient therapy. In this study, we examined the effect of both training modalities on the cardiac function in a rat model of T2DM. Methods: Rats were randomly assigned into control (chow diet, N=10) or high sugar diet (Western diet, N=22) for 18 weeks to induce T2DM. After 18 weeks, diabetic rats were assigned to the 3 different training modalities, i.e. sedentary (SED, N=8), MIT (N=7) or HIIT (N=7) for 12 additional weeks. Animals undergoing chow diet were kept sedentary and used as controls. Blood samples, echocardiography and hemodynamic measurements were evaluated to assess cardiac function and lipid profile. Inflammation and fibrosis were measured from LV tissue homogenates and tissue sections respectively. Results: After 30 weeks, diabetic animals displayed hypertrophy and altered lipid homeostasis. Both exercise modalities were able to significantly improve all these parameters. However, only HIIT was capable to normalize circulating free fatty acid levels. Exercise training normalized both glucose and insulin levels, independent of training modality. End-diastolic pressure was increased in sedentary diabetic animals, but normalized after exercise training. In addition, both training modalities were able to reduce the increased collagen deposition observed in diabetic animals, as well as pathological LV wall hypertrophy. Finally, fractional shortening only improved with MIT where inflammation status in cardiac tissue was reduced. Conclusion: Despite very different training modalities, both exercise interventions reversed to the same extent adverse remodeling in diabetic cardiomyopathy. MIT seems however to additionally reduce cardiac inflammation. [ABSTRACT FROM AUTHOR]