scholarly journals Facilitated Ca2+ homeostasis and attenuated myocardial autophagy contribute to alleviation of diabetic cardiomyopathy after bariatric surgery

2018 ◽  
Vol 315 (5) ◽  
pp. H1258-H1268 ◽  
Author(s):  
Xin Huang ◽  
Shaozhuang Liu ◽  
Dong Wu ◽  
Yugang Cheng ◽  
Haifeng Han ◽  
...  
Keyword(s):  
Bariatric Surgery ◽  
Diabetic Cardiomyopathy ◽  
Ventricular Myocytes ◽  
Mammalian Target Of Rapamycin ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Autophagic Flux ◽  
Fk506 Binding Protein ◽  
Plasmic Reticulum ◽  
Chloroquine Treatment

Bariatric surgery has been reported to relieve diabetic cardiomyopathy (DCM) effectively. However, the mechanisms remain largely unknown. To determine the effects of bariatric surgery on DCM via modulation of myocardial Ca2+ homeostasis and autophagy, sleeve gastrectomy (SG), duodenal-jejunal bypass (DJB), and sham surgeries were performed in diabetic rats induced by high-fat diet and a low dose of streptozotocin. Cardiac remodeling was assessed by a series of morphometric and histological analyses. Transthoracic echocardiography and hemodynamic measurements were performed to determine cardiac function. Ca2+ homeostasis was evaluated by measuring Ca2+ transients with fura-2 AM in isolated ventricular myocytes along with detection of the abundance of Ca2+ regulatory proteins in the myocardium. Myocardial autophagic flux was determined by expression of autophagy-related proteins in the absence and presence of chloroquine. Both SG and DJB surgery alleviated DCM morphologically and functionally. Ca2+ transients exhibited a significantly higher amplitude and faster decay after SG and DJB, which could be partially explained by increased expression of ryanodine receptor 2, sarco(endo)plasmic reticulum Ca2+-2ATPase, 12.6-kDa FK506-binding protein, and hyperphosphorylation of phospholamban. In addition, a lower level of light chain 3B and higher level of p62 were detected after both SG and DJB, which was not reversed by chloroquine treatment and associated with activated mammalian target of rapamycin and attenuated AMP-activated protein kinase signaling pathway. Collectively, these results provided evidence that bariatric surgery could alleviate DCM effectively, which may result, at least in part, from facilitated Ca2+ homeostasis and attenuated autophagy, suggesting a potential choice for treatment of DCM when properly implemented. NEW & NOTEWORTHY The present study is the first to investigate the modulation of myocardial Ca2+ homeostasis and autophagy after bariatric surgery and to examine its effects on diabetic cardiomyopathy. Bariatric surgery could facilitate myocardial Ca2+ homeostasis and attenuate myocardial autophagy, contributing to the alleviation of cardiomyopathy morphologically and functionally in a diabetic rat model.

scholarly journals Silencing of PARP2 Blocks Autophagic Degradation

Cells ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 380 ◽  
Author(s):  
Laura Jankó ◽  
Zsanett Sári ◽  
Tünde Kovács ◽  
Gréta Kis ◽  
Magdolna Szántó ◽  
...  
Keyword(s):  
Mammalian Target Of Rapamycin ◽  
C2c12 Cells ◽  
Myoblast Differentiation ◽  
Serum Starvation ◽  
Autophagic Flux ◽  
Embryonic Fibroblasts ◽  
Nicotinamide Riboside ◽  
Chloroquine Treatment ◽  
Autophagic Degradation ◽  
Sirt1 Inhibitor

Poly(ADP-Ribose) polymerases (PARPs) are enzymes that metabolize NAD+. PARP1 and PARP10 were previously implicated in the regulation of autophagy. Here we showed that cytosolic electron-dense particles appear in the cytoplasm of C2C12 myoblasts in which PARP2 is silenced by shRNA. The cytosolic electron-dense bodies resemble autophagic vesicles and, in line with that, we observed an increased number of LC3-positive and Lysotracker-stained vesicles. Silencing of PARP2 did not influence the maximal number of LC3-positive vesicles seen upon chloroquine treatment or serum starvation, suggesting that the absence of PARP2 inhibits autophagic breakdown. Silencing of PARP2 inhibited the activity of AMP-activated kinase (AMPK) and the mammalian target of rapamycin complex 2 (mTORC2). Treatment of PARP2-silenced C2C12 cells with AICAR, an AMPK activator, nicotinamide-riboside (an NAD+ precursor), or EX-527 (a SIRT1 inhibitor) decreased the number of LC3-positive vesicles cells to similar levels as in control (scPARP2) cells, suggesting that these pathways inhibit autophagic flux upon PARP2 silencing. We observed a similar increase in the number of LC3 vesicles in primary PARP2 knockout murine embryonic fibroblasts. We provided evidence that the enzymatic activity of PARP2 is important in regulating autophagy. Finally, we showed that the silencing of PARP2 induces myoblast differentiation. Taken together, PARP2 is a positive regulator of autophagic breakdown in mammalian transformed cells and its absence blocks the progression of autophagy.

Intracellular protons inhibit transient outward K+ current in ventricular myocytes from diabetic rats

1996 ◽  
Vol 271 (5) ◽  
pp. H2154-H2161 ◽  
Author(s):  
Z. Xu ◽  
K. P. Patel ◽  
G. J. Rozanski
Keyword(s):  
Ventricular Myocytes ◽  
External Solution ◽  
Cell Voltage ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Intracellular Acidosis ◽  
K Current ◽  
Acid Load ◽  
Dimethyl Amiloride ◽  
And Control

This study examined the effects of protons on cardiac ion channel function in early stages of diabetes mellitus. Transient outward (I(to)) and inward rectifier K+ (IK1) currents were recorded by the whole cell, voltage-clamp technique in ventricular myocytes isolated from hearts of streptozotocin-induced diabetic and control rats. Proton concentration was controlled by independently varying the pH of buffered external or pipette (pHp) solutions. External acidification did not alter I(to) in diabetic rat myocytes when initiated after intracellular dialysis with standard pHp 7.2, but when these cells were dialyzed with acidic pHp (6.6 or 6.0), I(to) density was significantly reduced. Low pHp also reduced I(to) density more in cells from diabetic rats than in controls, whereas alkaline pHp had no effect on either group of cells compared with standard pHp 7.2. In control myocytes dialyzed with pHp 6.0, block of Na+/H+ exchange with 5-(N,N-dimethyl)-amiloride (DMA) or Na(+)-free external solution further reduced I(to) density compared with pHp 6.0 alone, whereas these treatments had less effect on acid-dialyzed cells from diabetic rats. Dialysis with pHp to 6.0 did not alter IK1 in either group of cells compared with standard pHp 7.2, but when done in the presence of DMA or Na(+)-free conditions, IK1 density in both groups was significantly reduced by nearly the same amount. We conclude that intracellular protons inhibit I(to) channels in ventricular myocytes from diabetic and control rats, but that for a given acid load, inhibition is markedly greater in diabetics. This difference may be explained by a diabetes-induced decrease in Na+/H+ exchange that limits proton extrusion during intracellular acidosis. Moreover, acidosis may differentially suppress I(to) and IK1, suggesting that these K+ channels exhibit dissimilar sensitivities to intracellular protons.

Metabolic basis of decreased transient outward K+ current in ventricular myocytes from diabetic rats

1996 ◽  
Vol 271 (5) ◽  
pp. H2190-H2196 ◽  
Author(s):  
Z. Xu ◽  
K. P. Patel ◽  
G. J. Rozanski
Keyword(s):  
Ventricular Myocytes ◽  
Cell Voltage ◽  
Diabetic Rats ◽  
K Channel ◽  
Diabetic Rat ◽  
Channel Function ◽  
Early Stages ◽  
Metabolic Basis ◽  
External Glucose

The purpose of this study was to examine the mechanisms of alterations in cardiac K+ channel function in early stages of experimental diabetes mellitus induced by streptozotocin. Transient outward (Ito) and inward rectifier (IK1) K+ currents were recorded by the whole cell voltage-clamp technique in ventricular myocytes isolated from hearts of 2- to 4-wk diabetic and age-matched control rats. Ito density in myocytes from diabetic rats was approximately 30% less than control (at +60 mV; P < 0.01) under basal recording conditions in the presence of 18 mM external glucose, whereas IK1 density was not different between groups. When external glucose concentration was decreased to 5 mM for 4-6 h, basal Ito density was not changed in either group of myocytes. To further examine the possible metabolic basis of reduced Ito density in myocytes from diabetic rats, we separately tested three structurally different compounds that affect substrate utilization in cardiac myocytes: insulin (0.1 microM), dichloroacetate (1.5 mM), and L-carnitine (10 mM). Each compound completely normalized Ito density in myocytes from diabetic rats treated in vitro for 4-6 h. The same agents had no effect on Ito density in control myocytes, nor was IK1 altered in either group of cells. These data provide the first evidence to support the hypothesis that there is a metabolic basis for decreased Ito density in diabetic rat ventricular myocytes in early stages of this model. Furthermore, our data suggest that depressed glucose metabolism in the diabetic heart may be a key factor underlying changes in Ito channel function, because agents that increase glucose utilization normalize Ito density within a short time period.

Altered Ca2+ handling in ventricular myocytes isolated from diabetic rats

1996 ◽  
Vol 270 (5) ◽  
pp. H1529-H1537 ◽  
Author(s):  
D. Lagadic-Gossmann ◽  
K. J. Buckler ◽  
K. Le Prigent ◽  
D. Feuvray
Keyword(s):  
Plasma Membrane ◽  
Electrical Stimulation ◽  
Sarcoplasmic Reticulum ◽  
Diabetic Cardiomyopathy ◽  
Time Course ◽  
Ventricular Myocytes ◽  
Diabetic Rats ◽  
Significant Prolongation ◽  
Streptozotocin Induced Diabetes ◽  
Isolated Rat

It has been suggested that alterations in intracellular Ca2+ homeostasis may be responsible for the development of diabetic cardiomyopathy. We have studied the effects of streptozotocin-induced diabetes on intracellular Ca2+ concentration ([Ca2+]i) in enzymically isolated rat ventricular myocytes. [Ca2+]i was measured using indo 1 or fluo 3. Both diastolic and peak systolic [Ca2+]i were reduced in diabetic compared with normal myocytes (by 52 and 43%, respectively). The decay phase of the systolic [Ca2+]i transient was slower in the diabetic myocyte compared with normal (time constant = 89.6 +/- 3.4 ms, n = 23, normal vs. 105.2 +/- 4.05 ms, n = 20, diabetic; P < 0.01). This led to a significant prolongation of the [Ca2+]i transient duration in the diabetic myocyte. In both normal and diabetic myocytes, increasing the frequency of electrical stimulation decreased peak systolic [Ca2+]i.The relationship between stimulation frequency and normalized peak systolic [Ca2+]i was the same for both normal and diabetic myocytes. We also found that the caffeine-induced Ca2+ release [used as an index of sarcoplasmic reticulum (SR) Ca2+ content] was significantly reduced in diabetic myocytes. These data indicate that SR Ca2+ content is decreased by diabetes. In the presence of thapsigargin (2.5 microM, an inhibitor of SR Ca(2+)-adenosinetriphosphatase), the magnitude and time course of stimulus-evoked [Ca2+]i transients were identical in both groups of myocytes, suggesting that Ca2+ influx and/or efflux across the plasma membrane is not significantly affected in diabetes. We conclude that 1) diabetes is associated with significant alterations in [Ca2+]i homeostasis and 2) the decrease in systolic [Ca2+]i and lengthening of the systolic [Ca2+]i transient result primarily from dysfunction of the SR.

scholarly journals High-Intensity Exercise Reduces Cardiac Fibrosis and Hypertrophy but Does Not Restore the Nitroso-Redox Imbalance in Diabetic Cardiomyopathy

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Ulises Novoa ◽  
Diego Arauna ◽  
Marisol Moran ◽  
Madelaine Nuñez ◽  
Sebastián Zagmutt ◽  
...  
Keyword(s):  
Diabetic Cardiomyopathy ◽  
High Intensity ◽  
Diabetic Rats ◽  
High Intensity Exercise ◽  
Reverse Remodeling ◽  
Cardiomyocyte Hypertrophy ◽  
Diabetic Rat ◽  
Chronic Exercise ◽  
Redox Imbalance ◽  
Altered Glucose

Diabetic cardiomyopathy refers to the manifestations in the heart as a result of altered glucose homeostasis, reflected as fibrosis, cellular hypertrophy, increased oxidative stress, and apoptosis, leading to ventricular dysfunction. Since physical exercise has been indicated as cardioprotective, we tested the hypothesis that high-intensity exercise training could reverse the cardiac maladaptations produced by diabetes. For this, diabetes was induced in rats by a single dose of alloxan. Diabetic rats were randomly assigned to a sedentary group or submitted to a program of exercise on a treadmill for 4 weeks at 80% of maximal performance. Another group of normoglycemic rats was used as control. Diabetic rat hearts presented cardiomyocyte hypertrophy and interstitial fibrosis. Chronic exercise reduced both parameters but increased apoptosis. Diabetes increased the myocardial levels of the mRNA and proteins of NADPH oxidases NOX2 and NOX4. These altered levels were not reduced by exercise. Diabetes also increased the level of uncoupled endothelial nitric oxide synthase (eNOS) that was not reversed by exercise. Finally, diabetic rats showed a lower degree of phosphorylated phospholamban and reduced levels of SERCA2 that were not restored by high-intensity exercise. These results suggest that high-intensity chronic exercise was able to reverse remodeling in the diabetic heart but was unable to restore the nitroso-redox imbalance imposed by diabetes.

Restoration of diabetes-induced abnormal local Ca2+ release in cardiomyocytes by angiotensin II receptor blockade

2007 ◽  
Vol 292 (2) ◽  
pp. H912-H920 ◽  
Author(s):  
Nazmi Yaras ◽  
Ayca Bilginoglu ◽  
Guy Vassort ◽  
Belma Turan
Keyword(s):  
Renin Angiotensin System ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Receptor Blockade ◽  
Angiotensin Ii Receptor ◽  
Rat Cardiomyocytes ◽  
Fk506 Binding Protein ◽  
Protein Levels ◽  
Release Mechanisms

Stimulation of local renin-angiotensin system and increased levels of oxidants characterize the diabetic heart. Downregulation of ANG II type 1 receptors (AT1) and enhancement in PKC activity in the heart point out the role of AT1 blockers in diabetes. The purpose of this study was to evaluate a potential role of an AT1 blocker, candesartan, on abnormal Ca2+ release mechanisms and its relationship with PKC in the cardiomyocytes from streptozotocin-induced diabetic rats. Cardiomyocytes were isolated enzymatically and then incubated with either candesartan or a nonspecific PKC inhibitor bisindolylmaleimide I (BIM) for 6–8 h at 37°C. Both candesartan and BIM applied on diabetic cardiomyocytes significantly restored the altered kinetic parameters of Ca2+ transients, as well as depressed Ca2+ loading of sarcoplasmic reticulum, basal Ca2+ level, and spatiotemporal properties of the Ca2+ sparks. In addition, candesartan and BIM significantly antagonized the hyperphosphorylation of cardiac ryanodine receptor (RyR2) and restored the depleted protein levels of both RyR2 and FK506 binding protein 12.6 (FKBP12.6). Furthermore, candesartan and BIM also reduced the increased PKC levels and oxidized protein thiol level in membrane fraction of diabetic rat cardiomyocytes. Taken together, these data demonstrate that AT1 receptor blockade protects cardiomyocytes from development of cellular alterations typically associated with Ca2+ release mechanisms in diabetes mellitus. Prevention of these alterations by candesartan may present a useful pharmacological strategy for the treatment of diabetic cardiomyopathy.

scholarly journals Endoplasmic reticulum stress is involved in myocardial apoptosis of streptozocin-induced diabetic rats

2007 ◽  
Vol 196 (3) ◽  
pp. 565-572 ◽  
Author(s):  
Zhenhua Li ◽  
Tao Zhang ◽  
Hongyan Dai ◽  
Guanghui Liu ◽  
Haibin Wang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Diabetic Cardiomyopathy ◽  
Critical Role ◽  
Diabetic Rats ◽  
Diabetic Heart ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Diabetic Rat ◽  
Mrna Levels ◽  
Diabetic Myocardium

Apoptosis plays a critical role in the diabetic cardiomyopathy, and endoplasmic reticulum stress (ERS) is one of the intrinsic apoptosis pathways. Previous studies have shown that the endoplasmic reticulum becomes swollen and dilated in diabetic myocardium, and ERS is involved in heart failure and diabetic kidney. This study is aimed to demonstrate whether ERS is induced in myocardium of streptozotocin (STZ)-induced diabetic rats. We established a type 1 diabetic rat model, used echocardiographic evaluation, hematoxylin–eosin staining, and the terminal deoxynucleotidyl transferase-mediated DNA nick-end labeling staining to identify the existence of diabetic cardiomyopathy and enhanced apoptosis in the diabetic heart. We performed immunohistochemistry, western blot, and real-time PCR to analyze the hallmarks of ERS that include glucose-regulated protein 78, CCAAT/enhancer-binding protein homologous protein (CHOP) and caspase12. We found these hallmarks to have enhanced expression in protein and mRNA levels in diabetic myocardium. Also, another pathway that can lead to cell death of ERS, c-Jun NH2-terminal kinase-dependent pathway, was also activated in diabetic heart. Those results suggested that ERS was induced in STZ-induced diabetic rats' myocardium, and ERS-associated apoptosis occurred in the pathophysiology of diabetic cardiomyopathy.

Anti-diabetic activity of diphenhydramine in diabetic rats

2020 ◽  
Vol 11 (4) ◽  
pp. 5067-5070
Author(s):  
Pang Jyh Chayng ◽  
Nurul Ain ◽  
Kaswandi Md Ambia ◽  
Rahim Md Noah
Keyword(s):  
Blood Glucose ◽  
Blood Glucose Level ◽  
Glucose Level ◽  
Fasting Blood Glucose ◽  
Insulin Level ◽  
Diabetic Rats ◽  
Group Iv ◽  
Diabetic Rat ◽  
Control Group ◽  
Group I

The purpose of this project is to study the anti-diabetic effect of on a diabetic rat model. A total of Twenty male Sprague rats were used and it randomly distributed into four groups which are Group I: , Group II: negative control, Group III: and Group IV: and . In diabetic model were induced with via injection at the dosage of 65mg/kg. and FBG (Fasting Blood Glucose) level of diabetic rats were assessed every three days. Blood was collected via cardiac puncture at day 21 after the induction of treatment. Insulin level of the rats was assessed with the Mercodia Rat Insulin ELISA kit. FBG level of group I (12.16 ±3.96, p&lt;0.05) and group IV (11.34 ±3.67, p&lt;0.05) were significantly decreased. Meanwhile, the for all rats did not show any significant increase. However, the insulin level was escalated in group IV (0.74+0.25, p&lt;0.05) significantly. The present study shows that the and the combination of and lowered blood glucose level and enhanced insulin secretion.

Exercise and Stevia Rebaudiana (R) Extracts Attenuate Diabetic Cardiomyopathy in Type 2 Diabetic Rats: Possible Underlying Mechanisms

2020 ◽  
Vol 20 (7) ◽  
pp. 1117-1132
Author(s):  
Abdelaziz M. Hussein ◽  
Elsayed A. Eid ◽  
Ismaeel Bin-Jaliah ◽  
Medhat Taha ◽  
Lashin S. Lashin
Keyword(s):  
Oxidative Stress ◽  
Blood Glucose ◽  
Diabetic Cardiomyopathy ◽  
Caspase 3 ◽  
Stevia Rebaudiana ◽  
Diabetic Rats ◽  
Control Group ◽  
Underlying Mechanisms ◽  
Type 2 Diabetic

Background and Aims: In the current work, we studied the effects of exercise and stevia rebaudiana (R) extracts on diabetic cardiomyopathy (DCM) in type 2 diabetic rats and their possible underlying mechanisms. Methods: : Thirty-two male Sprague Dawley rats were randomly allocated into 4 equal groups; a) normal control group, b) DM group, type 2 diabetic rats received 2 ml oral saline daily for 4 weeks, c) DM+ Exercise, type 2 diabetic rats were treated with exercise for 4 weeks and d) DM+ stevia R extracts: type 2 diabetic rats received methanolic stevia R extracts. By the end of the experiment, serum blood glucose, HOMA-IR, insulin and cardiac enzymes (LDH, CK-MB), cardiac histopathology, oxidative stress markers (MDA, GSH and CAT), myocardial fibrosis by Masson trichrome, the expression of p53, caspase-3, α-SMA and tyrosine hydroxylase (TH) by immunostaining in myocardial tissues were measured. Results: T2DM caused a significant increase in blood glucose, HOMA-IR index, serum CK-MB and LDH, myocardial damage and fibrosis, myocardial MDA, myocardial α-SMA, p53, caspase-3, Nrf2 and TH density with a significant decrease in serum insulin and myocardial GSH and CAT (p< 0.05). On the other hand, treatment with either exercise or stevia R extracts significantly improved all studied parameters (p< 0.05). Moreover, the effects of stevia R was more significant than exercise (p< 0.05). Conclusion: Both exercise and methanolic stevia R extracts showed cardioprotective effects against DCM and Stevia R offered more cardioprotective than exercise. This cardioprotective effect of these lines of treatment might be due to attenuation of oxidative stress, apoptosis, sympathetic nerve density and fibrosis and upregulation of the antioxidant transcription factor, Nrf2.

Effect of atorvastatin on the angiogenic responsiveness of coronary endothelial cells in normal and streptozotocin (STZ) induced diabetic rats

2014 ◽  
Vol 92 (4) ◽  
pp. 338-349 ◽  
Author(s):  
Kiranj K. Chaudagar ◽  
Anita A. Mehta
Keyword(s):  
Endothelial Cells ◽  
Low Dose ◽  
Ischemia Reperfusion ◽  
Late Phase ◽  
Diabetic Rats ◽  
Lipid Lowering ◽  
Diabetic Rat ◽  
High Dose ◽  
Atorvastatin Treatment ◽  
Coronary Endothelial Cells

Atorvastatin, a lipid lowering agent, possesses various pleiotropic vasculoprotective effects, but its role in coronary angiogenesis is still controversial. Our objective was to study the effects of atorvastatin on the angiogenic responsiveness of coronary endothelial cells (cEC) from normal and diabetic rats. Male Wistar rats were distributed among 9 groups; (i) normal rats, (ii) 30 day diabetic rats, (iii) 60 day diabetic rats, (iv) normal rats administered a low dose of atorvastatin (1 mg/kg body mass, per oral (p.o.), for 15 days); (v) 30 day diabetic rats administered a low dose of atorvastatin; (vi) 60 day diabetic rats administered a low dose of atorvastatin; (vii) normal rats administered a high dose of atorvastatin (5 mg/kg, p.o., for 15 days); (viii) 30 day diabetic rats administered a high dose of atorvastatin; (ix) 60 day diabetic rats administered a high dose of atorvastatin. Each group was further divided into 2 subgroups, (i) sham ischemia–reperfusion and (ii) rats hearts that underwent ischemia–reperfusion. Angiogenic responsiveness the and nitric oxide (NO) releasing properties of the subgroups of cECs were studied using a chorioallantoic membrane assay and the Griess method, respectively. Atorvastatin treatment significantly increased VEGF-induced angiogenic responsiveness and the NO-releasing properties of cECs from all of the subgroups, compared with their respective non-treated subgroups except for the late-phase diabetic rat hearts that underwent ischemia–reperfusion, and the high dose of atorvastatin treatment groups. These effects of atorvastatin were significantly inhibited by pretreatment of cECs with l-NAME, wortmannin, and chelerythrine. Thus, treatment with a low dose of atorvastatin improves the angiogenic responsiveness of the cECs from normal and diabetic rats, in the presence of VEGF, via activation of eNOS–NO release.

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