N-acetylcysteine and allopurinol synergistically enhance cardiac adiponectin content and reduce myocardial reperfusion injury in diabetic rats

Cardioprotective role of oleanolic acid in patients with type 2 diabetes mellitus

Background

Patients with type 2 diabetes mellitus (T2DM) experience a decline in cardiac function, resulting in poor prognosis. Therefore, restoration of cardiac function and improvement of myocardial fibrosis is an important treatment goal for patients with T2DM.

Material and methods

The chemical structure of oleanolic acid(OA) was downloaded from PubChem and uploaded to PharmMapper. GeneCards and OMIM databases were searched for genes related to OA and disease and plotted into a Venn diagram. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed using R software. Then, a mouse model of diabetes mellitus was established, and ELISA, echocardiographic analysis of cardiac function, TUNEL assay, and reactive oxygen species assay were performed.

Results

Network pharmacology analysis identified the related targets and potential molecular mechanisms underlying the effects of OA in T2DM. ELISA, echocardiographic analysis of cardiac function, and TUNEL assay results showed that OA inhibits apoptosis and improves apoptotic indexes in mice with T2DM-induced myocardial injury.

Conclusion

The results demonstrate the myocardial protective effect of OA in this mouse model.

N-acetylcysteine Protects Against Myocardial Ischemia-Reperfusion Injury Through Anti-ferroptosis in Type 1 Diabetic Mice

The hearts of subjects with diabetes are vulnerable to ischemia-reperfusion injury (IRI). In contrast, experimentally rodent hearts have been shown to be more resistant to IRI at the very early stages of diabetes induction than the heart of the non-diabetic control mice, and the mechanism is largely unclear. Ferroptosis has recently been shown to play an important role in myocardial IRI including that in diabetes, while the specific mechanisms are still unclear. Non-diabetic control (NC) and streptozotocin-induced diabetic (DM) mice were treated with the antioxidant N-acetylcysteine (NAC) in drinking water for 4 week starting at 1 week after diabetes induction. Mice were subjected to myocardial IRI induced by occluding the coronary artery for 30 min followed by 2 h of reperfusion, subsequently at 1, 2, and 5 week of diabetes induction. The post-ischemic myocardial infarct size in the DM mice was smaller than that in NC mice at 1 week of diabetes but greater than that in the NC mice at 2 and 5 week of diabetes, which were associated with a significant increase of ferroptosis at 2 and 5 week but a significant reduction of ferroptosis at 1 week of diabetes. NAC significantly attenuated post-ischemic ferroptosis as well as oxidative stress and reduced infarct size at 2 and 5 week of diabetes. Application of erastin, a ferroptosis inducer, reversed the cardioprotective effects of NAC. It is concluded that increased oxidative stress and ferroptosis are the major factors attributable to the increased vulnerability to myocardial IRI in diabetes and that attenuation of ferroptosis represents a major mechanism whereby NAC confers cardioprotection against myocardial IRI in diabetes.

Extraintestinal Manifestations in Induced Colitis: Controversial Effects of N-Acetylcysteine on Colon, Liver, and Kidney

Ulcerative colitis (UC) is a chronic and recurrent inflammatory bowel disease (IBD) characterized by continuous inflammation in the colonic mucosa. Extraintestinal manifestations (EIM) occur due to the disruption of the intestinal barrier and increased permeability caused by redox imbalance, dysbiosis, and inflammation originating from the intestine and contribute to morbidity and mortality. The aim of this study is to investigate the effects of oral N-acetylcysteine (NAC) on colonic, hepatic, and renal tissues in mice with colitis induced by dextran sulfate sodium (DSS). Male Swiss mice received NAC (150 mg/kg/day) in the drinking water for 30 days before and during (DSS 5% v/v; for 7 days) colitis induction. On the 38th day, colon, liver, and kidney were collected and adequately prepared for the analysis of oxidative stress (superoxide dismutase (SOD), catalase (CAT), glutathione reduced (GSH), glutathione oxidized (GSSG), malondialdehyde (MDA), and hydrogen peroxide (H2O2)) and inflammatory biomarkers (myeloperoxidase (MPO) -, tumor necrosis factor alpha - (TNF-α, and interleukin-10 (IL-10)). In colon, NAC protected the histological architecture. However, NAC did not level up SOD, in contrast, it increased MDA and pro-inflammatory effect (increased of TNF-α and decreased of IL-10). In liver, colitis caused both oxidative (MDA, SOD, and GSH) and inflammatory damage (IL-10). NAC was able only to increase GSH and GSH/GSSG ratio. Kidney was not affected by colitis; however, NAC despite increasing CAT, GSH, and GSH/GSSG ratio promoted lipid peroxidation (increased MDA) and pro-inflammatory action (decreased IL-10). Despite some beneficial antioxidant effects of NAC, the negative outcomes concerning irreversible oxidative and inflammatory damage in the colon, liver, and kidney confirm the nonsafety of the prophylactic use of this antioxidant in models of induced colitis, suggesting that additional studies are needed, and its use in humans not yet recommended for the therapeutic routine of this disease.

Propofol postconditioning alleviates diabetic myocardial ischemia‑reperfusion injury via the miR‑200c‑3p/AdipoR2/STAT3 signaling pathway

Myocardial ischemia/reperfusion (MI/RI) syndrome is one of the leading causes of mortality and disability. Propofol postconditioning is known to improve myocardial ischemia/reperfusion injury (MI/RI). The present study aimed to explore the mechanism of propofol postconditioning in diabetic MI/RI. Diabetic MI/RI rat models were established and the rats were treated via propofol postconditioning. Staining with 2,3,5-triphenyl-2H-tetrazolium chloride, H&E staining, TUNEL staining and ELISA were applied to detect infarct size, pathological changes, apoptosis and oxidative stress-related factor and apoptotic factor levels, respectively. Subsequently, the effect of propofol on H9C2 cells was also assessed using the Cell Counting Kit-8 assay. High-glucose hypoxia/reperfusion (H/R) models of H9C2 cardiomyocytes were established. miR-200c-3p overexpression or AdipoR2 silencing combined with propofol postconditioning was performed in H/R-induced H9C2 cells and STAT3 protein expression levels were determined. Propofol postconditioning significantly reduced myocardial infarct size, oxidative stress and apoptosis in diabetic MI/RI models. Furthermore, propofol postconditioning significantly reduced the oxidative stress and apoptosis of H9C2 cells in high-glucose H/R models. Propofol postconditioning also significantly downregulated miR-200c-3p expression levels and promoted AdipoR2 expression levels. miR-200c-3p overexpression or AdipoR2 downregulation significantly reversed the effects of propofol postconditioning on its antioxidation and anti-apoptotic effects in H9C2 cells and on decreasing STAT3 phosphorylation levels. Together, the results of the present study demonstrated that propofol postconditioning inhibited miR-200c-3p, upregulated AdipoR2 and activated the STAT3 signaling pathway, thus alleviating diabetic MI/RI and therefore highlighting its potential as a treatment of diabetic MI/RI.

N-Acetyl Cysteine, Selenium, and Ascorbic Acid Rescue Diabetic Cardiac Hypertrophy via Mitochondrial-Associated Redox Regulators

Metabolic disorders often lead to cardiac complications. Metabolic deregulations during diabetic conditions are linked to mitochondrial dysfunctions, which are the key contributing factors in cardiac hypertrophy. However, the underlying mechanisms involved in diabetes-induced cardiac hypertrophy are poorly understood. In the current study, we initially established a diabetic rat model by alloxan-administration, which was validated by peripheral glucose measurement. Diabetic rats displayed myocardial stiffness and fibrosis, changes in heart weight/body weight, heart weight/tibia length ratios, and enhanced size of myocytes, which altogether demonstrated the establishment of diabetic cardiac hypertrophy (DCH). Furthermore, we examined the expression of genes associated with mitochondrial signaling impairment. Our data show that the expression of PGC-1α, cytochrome c, MFN-2, and Drp-1 was deregulated. Mitochondrial-signaling impairment was further validated by redox-system dysregulation, which showed a significant increase in ROS and thiobarbituric acid reactive substances, both in serum and heart tissue, whereas the superoxide dismutase, catalase, and glutathione levels were decreased. Additionally, the expression levels of pro-apoptotic gene PUMA and stress marker GATA-4 genes were elevated, whereas ARC, PPARα, and Bcl-2 expression levels were decreased in the heart tissues of diabetic rats. Importantly, these alloxan-induced impairments were rescued by N-acetyl cysteine, ascorbic acid, and selenium treatment. This was demonstrated by the amelioration of myocardial stiffness, fibrosis, mitochondrial gene expression, lipid profile, restoration of myocyte size, reduced oxidative stress, and the activation of enzymes associated with antioxidant activities. Altogether, these data indicate that the improvement of mitochondrial dysfunction by protective agents such as N-acetyl cysteine, selenium, and ascorbic acid could rescue diabetes-associated cardiac complications, including DCH.

Acetate causes renoprotection like androgen and mineralocorticoid receptors blockade in testosterone-exposed pregnant rats

The kidney plays a critical role in human health and deviation from its normal function can lead to severe morbidity and mortality. Exposure to excess testosterone in women has been linked to several disorders, including kidney disorder and acting undoubtedly through androgen receptor (AR), whereas the involvement of mineralocorticoid receptor (MR) is unclear. Likewise, the renal effect of sodium acetate (SAc) during late gestational exposure to testosterone is not well known. We hypothesized that SAc or MR blockade would protect the kidney of testosterone-exposed pregnant rats against glutathione and adenosine depletion. Twenty-five pregnant Wistar rats were treated (sc) with olive oil, testosterone propionate (0.5 mg/kg) singly or in combination with SAc (200 mg/kg; p.o.), androgen receptor (AR) blocker, flutamide (Flu; 7.5 mg/kg; p.o.) or (MR) blocker, eplerenone (Eple; 0.5 mg/kg) between gestational days 14 and 19. Glutathione, adenosine and nitric oxide were decreased while uric acid (UA), xanthine oxidase (XO), malondialdehyde (MDA), lactate dehydrogenase activity and free fatty acids were increased in the kidneys of gestational rats exposed to testosterone. Also, plasma urea and creatinine were elevated. SAc and Eple reversed tested testosterone-induced effects in gestational rats. The exposure to testosterone impairs renal antioxidant defense via AR and MR during late gestation in pregnant rats. The study also provides evidence that sodium acetate protects the kidneys of gestational testosterone-exposed rats against defective antioxidant defense in like manner as MR or AR antagonist.

Adiponectin Facilitates Postconditioning Cardioprotection through Both AMPK-Dependent Nuclear and AMPK-Independent Mitochondrial STAT3 Activation

Myocardial ischemic postconditioning- (IPo-) mediated cardioprotection against myocardial ischemia-reperfusion (IR) injury needs the activation of signal transducer and activator of transcription 3 (STAT3), which involves adiponectin (APN). APN confers its biological effects through AMP-activated protein kinase- (AMPK-) dependent and AMPK-independent pathways. However, the role of AMPK in APN-mediated STAT3 activation in IPo cardioprotection is unknown. We hypothesized that APN-mediated STAT3 activation in IPo is AMPK-independent and that APN through AMPK-dependent STAT3 activation facilitates IPo cardioprotection. Here, Sprague-Dawley rats were subjected to myocardial IR without or with IPo and/or APN. APN or IPo significantly improved postischemic cardiac function and reduced myocardial injury and oxidative stress, and their combination further attenuated postischemic myocardial injuries. APN or its combination with IPo but not IPo alone significantly increased AMPK activation and both nuclear and mitochondrial STAT3 activation, while IPo significantly enhanced mitochondrial but not nuclear STAT3 activation. In primarily isolated cardiomyocytes, recombined globular APN (gAd), hypoxic postconditioning (HPo), or their combination significantly attenuated hypoxia/reoxygenation-induced cell injury and increased nuclear and/or mitochondrial STAT3 activation. STAT3 inhibition had no impact on gAd or gAd in combination with HPo-induced AMPK activation but abolished their cellular protective effects. AMPK inhibition did not affect HPo cardioprotection but abolished gAd cardioprotection and disabled gAd to facilitate/enhance HPo cardioprotection and STAT3 activation. These results suggest that APN confers cardioprotection through AMPK-dependent and AMPK-independent STAT3 activation, while IPo confers cardioprotection through AMPK-independent mitochondrial STAT3 activation. Joint use of APN and IPo synergistically attenuated myocardial IR injury by activating STAT3 via distinct signaling pathways.

An Update on the Multifaceted Roles of STAT3 in the Heart

Signal transducer and activator of transcription 3 (STAT3) is a signaling molecule and transcription factor that plays important protective roles in the heart. The protection mediated by STAT3 is attributed to its genomic actions as a transcription factor and other non-genomic roles targeting mitochondrial function and autophagy. As a transcription factor, STAT3 upregulates genes that are anti-oxidative, anti-apoptotic, and pro-angiogenic, but suppresses anti-inflammatory and anti-fibrotic genes. Its suppressive effects on gene expression are achieved through competing with other transcription factors or cofactors. STAT3 is also linked to the modification of mRNA expression profiles in cardiac cells by inhibiting or inducing miRNA. In addition to these genomic roles, STAT3 is suggested to function protectively in mitochondria, where it regulates ROS production, in part by regulating the activities of the electron transport chain complexes, although our recent evidence calls this role into question. Nonetheless, STAT3 is a key player known to be activated in the cardioprotective ischemic conditioning protocols. Through these varied roles, STAT3 participates in various mechanisms that contribute to cardioprotection against different heart pathologies, including myocardial infarction, hypertrophy, diabetic cardiomyopathy, and peripartum cardiomyopathy. Understanding how STAT3 is involved in the protective mechanisms against these different cardiac pathologies could lead to novel therapeutic strategies to treat them.

Effects of Cardiovascular Risk Factors on Cardiac STAT3

Nuclear, mitochondrial and cytoplasmic signal transducer and activator of transcription 3 (STAT3) regulates many cellular processes, e.g., the transcription or opening of mitochondrial permeability transition pore, and its activity depends on the phosphorylation of Tyr705 and/or Ser727 sites. In the heterogeneous network of cardiac cells, STAT3 promotes cardiac muscle differentiation, vascular element formation and extracellular matrix homeostasis. Overwhelming evidence suggests that STAT3 is beneficial for the heart, plays a role in the prevention of age-related and postpartum heart failure, protects the heart against cardiotoxic doxorubicin or ischaemia/reperfusion injury, and is involved in many cardioprotective strategies (e.g., ischaemic preconditioning, perconditioning, postconditioning, remote or pharmacological conditioning). Ischaemic heart disease is still the leading cause of death worldwide, and many cardiovascular risk factors contribute to the development of the disease. This review focuses on the effects of various cardiovascular risk factors (diabetes, aging, obesity, smoking, alcohol, depression, gender, comedications) on cardiac STAT3 under non-ischaemic baseline conditions, and in settings of ischaemia/reperfusion injury with or without cardioprotective strategies.

A Systematic Review on the Protective Effect of N-Acetyl Cysteine Against Diabetes-Associated Cardiovascular Complications

INTRODUCTION

Heart failure is the leading cause of death in patients with diabetes. No treatment currently exists to specifically protect these patients at risk of developing cardiovascular complications. Accelerated oxidative stress-induced tissue damage due to persistent hyperglycemia is one of the major factors implicated in deteriorated cardiac function within a diabetic state. N-acetyl cysteine (NAC), through its enhanced capacity to endogenously synthesize glutathione, a potent antioxidant, has displayed abundant health-promoting properties and has a favorable safety profile.

OBJECTIVE

An increasing number of experimental studies have reported on the strong ameliorative properties of NAC. We systematically reviewed the data on the cardioprotective potential of this compound to provide an informative summary.

METHODS

Two independent reviewers systematically searched major databases, including PubMed, Cochrane Library, Google scholar, and Embase for available studies reporting on the ameliorative effects of NAC as a monotherapy or in combination with other therapies against diabetes-associated cardiovascular complications. We used the ARRIVE and JBI appraisal guidelines to assess the quality of individual studies included in the review. A meta-analysis could not be performed because the included studies were heterogeneous and data from randomized clinical trials were unavailable.

RESULTS

Most studies support the ameliorative potential of NAC against a number of diabetes-associated complications, including oxidative stress. We discuss future prospects, such as identification of additional molecular mechanisms implicated in diabetes-induced cardiac damage, and highlight limitations, such as insufficient studies reporting on the comparative effect of NAC with common glucose-lowering therapies. Information on the comparative analysis of NAC, in terms of dose selection, administration mode, and its effect on different cardiovascular-related markers is important for translation into clinical studies.

CONCLUSIONS

NAC exhibits strong potential for the protection of the diabetic heart at risk of myocardial infarction through inhibition of oxidative stress. The effect of NAC in preventing both ischemia and non-ischemic-associated cardiac damage is also of interest. Consistency in dose selection in most studies reported remains important in dose translation for clinical relevance.

Pharmacological postconditioning with atorvastatin calcium attenuates myocardial ischemia/reperfusion injury in diabetic rats by phosphorylating GSK3β

Diabetes is an independent risk factor for myocardial ischemia, and many epidemiological data and laboratory studies have revealed that diabetes significantly exacerbated myocardial ischemia/reperfusion injury and ameliorated protective effects. The present study aimed to determine whether pharmacological postconditioning with atorvastatin calcium lessened diabetic myocardial ischemia/reperfusion injury, and investigated the role of glycogen synthase kinase (GSK3β) in this. A total of 72 streptozotocin-induced diabetic rats were randomly divided into six groups, and 24 age-matched male non-diabetic Sprague-Dawley rats were randomly divided into two groups. Rats all received 40 min myocardial ischemia followed by 180 min reperfusion, except sham-operated groups. Compared with the non-diabetic ischemia/reperfusion model group, the diabetic ischemia/reperfusion group had a comparable myocardial infarct size, but a higher level of serum cardiac troponin I (cTnI) and morphological alterations to their myocardial cells. Compared with the diabetic ischemia/reperfusion group, the group that received pharmacological postconditioning with atorvastatin calcium had smaller myocardial infarct sizes, lower levels of cTnI, reduced morphological alterations to myocardial cells, higher levels of p-GSK3β, heat shock factor (HSF)-1 and heat shock protein (HSP)70. The cardioprotective effect conferred by atorvastatin calcium did not attenuate myocardial ischemia/reperfusion injury following application of TDZD-8, which phosphorylates and inactivates GSK3β. Pharmacological postconditioning with atorvastatin calcium may attenuate diabetic heart ischemia/reperfusion injury in the current context. The phosphorylation of GSK3β serves a critical role during the cardioprotection in diabetic rats, and p-GSK3β may accelerate HSP70 production partially by activating HSF-1 during myocardial ischemic/reperfusion injury.

N-Acetylcysteine Attenuates Diabetic Myocardial Ischemia Reperfusion Injury through Inhibiting Excessive Autophagy

Background. Excessive autophagy is a major mechanism of myocardial ischemia reperfusion injury (I/RI) in diabetes with enhanced oxidative stress. Antioxidant N-acetylcysteine (NAC) reduces myocardial I/RI. It is unknown if inhibition of autophagy may represent a mechanism whereby NAC confers cardioprotection in diabetes. Methods and Results. Diabetes was induced in Sprague-Dawley rats with streptozotocin and they were treated without or with NAC (1.5 g/kg/day) for four weeks before being subjected to 30-minute coronary occlusion and 2-hour reperfusion. The results showed that cardiac levels of 15-F2t-Isoprostane were increased and that autophagy was evidenced as increases in ratio of LC3 II/I and protein P62 and AMPK and mTOR expressions were significantly increased in diabetic compared to nondiabetic rats, concomitant with increased postischemic myocardial infarct size and CK-MB release but decreased Akt and eNOS activation. Diabetes was also associated with increased postischemic apoptotic cell death manifested as increases in TUNEL positive cells, cleaved-caspase-3, and ratio of Bax/Bcl-2 protein expression. NAC significantly attenuated I/RI-induced increases in oxidative stress and cardiac apoptosis, prevented postischemic autophagy formation in diabetes, and reduced postischemic myocardial infarction (all p < 0.05). Conclusions. NAC confers cardioprotection against diabetic heart I/RI primarily through inhibiting excessive autophagy which might be a major mechanism why diabetic hearts are less tolerant to I/RI.

Allopurinol Protective Effect of Renal Ischemia by Downregulating TNF-α, IL-1β, and IL-6 Response

Allopurinol is a well-known antioxidant that protects tissue against ischemia and reperfusion injury, blocking purine catabolism, and possibly reducing TNF-α and other cytokines. It also plays a significant role in reducing the inflammatory processes by inhibiting chemotaxis and other inflammatory mediators. The objective of this study was to define the role of allopurinol regarding kidney ischemic injury particularly as to its effect on inflammatory molecules such as TNF-α, IL-1β, and IL-6 response. One hundred and twenty five rats were subjected to warm renal ischemia. Five more animals were included as sham. Animal survival and plasma levels of lipid peroxidation, myeloperoxidase, lactate dehydrogenase, glutathione, urea, creatinine, and cytokines were determined. Inflammatory parameters (TNF-α, IL-1β, and IL-6) were measured in all groups by quantitative immunosorbent assay. Further, immunohistological and histopathological studies were carried out on animals treated prior to, or following reperfusion with 10 and 50 mg/kg of Allopurinol. The statistical analysis included ANOVA and Fisher test as well as χ² test. Significance was reached at a p < 0.05. The results of this study indicated that Allopurinol protected against kidney ischemia-reperfusion injury since significantly better results of survival, biochemical analysis, and histopathological testing were observed in treated animals as compared to ischemic controls. In conclusion, Allopurinol protected ischemic kidneys through a mechanism associated with downregulation of TNF-α, IL-1 β, and IL-6, in addition to other well-known effects such as decreased lipid peroxidation and neutrophil activity. It also increased antioxidant capacity and diminished endogenous peroxidase stain in renal ischemic tissue. Therefore, this experiment showed an effectiveness of allopurinol protection against proteomic and morphological damage.

Hyperglycemia Aggravates Hepatic Ischemia Reperfusion Injury by Inducing Chronic Oxidative Stress and Inflammation

Aim. To investigate whether hyperglycemia will aggravate hepatic ischemia reperfusion injury (HIRI) and the underlying mechanisms. Methods. Control and streptozotocin-induced diabetic Sprague-Dawley rats were subjected to partial hepatic ischemia reperfusion. Liver histology, transferase, inflammatory cytokines, and oxidative stress were assessed accordingly. Similarly, BRL-3A hepatocytes were subjected to hypoxia/reoxygenation (H/R) after high (25 mM) or low (5.5 mM) glucose culture. Cell viability, reactive oxygen species (ROS), and activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB) were determined. Results. Compared with control, diabetic rats presented more severe hepatic injury and increased hepatic inflammatory cytokines and oxidative stress. HIRI in diabetic rats could be ameliorated by pretreatment of N-acetyl-L-cysteine (NAC) or apocynin. Excessive ROS generation and consequent Nrf2 and NF-κB translocation were determined after high glucose exposure. NF-κB translocation and its downstream cytokines were further increased in high glucose cultured group after H/R. While proper regulation of Nrf2 to its downstream antioxidases was observed in low glucose cultured group, no further induction of Nrf2 pathway by H/R after high glucose culture was identified. Conclusion. Hyperglycemia aggravates HIRI, which might be attributed to chronic oxidative stress and inflammation and potential malfunction of antioxidative system.

Transcriptomic alterations in the heart of non-obese type 2 diabetic Goto-Kakizaki rats

Background

There is a spectacular rise in the global prevalence of type 2 diabetes mellitus (T2DM) due to the worldwide obesity epidemic. However, a significant proportion of T2DM patients are non-obese and they also have an increased risk of cardiovascular diseases. As the Goto-Kakizaki (GK) rat is a well-known model of non-obese T2DM, the goal of this study was to investigate the effect of non-obese T2DM on cardiac alterations of the transcriptome in GK rats.

Methods

Fasting blood glucose, serum insulin and cholesterol levels were measured at 7, 11, and 15 weeks of age in male GK and control rats. Oral glucose tolerance test and pancreatic insulin level measurements were performed at 11 weeks of age. At week 15, total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 41,012 genes, and then expression of selected genes was confirmed by qRT-PCR. Gene ontology and protein–protein network analyses were performed to demonstrate potentially characteristic gene alterations and key genes in non-obese T2DM.

Results

Fasting blood glucose, serum insulin and cholesterol levels were significantly increased, glucose tolerance and insulin sensitivity were significantly impaired in GK rats as compared to controls. In hearts of GK rats, 204 genes showed significant up-regulation and 303 genes showed down-regulation as compared to controls according to microarray analysis. Genes with significantly altered expression in the heart due to non-obese T2DM includes functional clusters of metabolism (e.g. Cyp2e1, Akr1b10), signal transduction (e.g. Dpp4, Stat3), receptors and ion channels (e.g. Sln, Chrng), membrane and structural proteins (e.g. Tnni1, Mylk2, Col8a1, Adam33), cell growth and differentiation (e.g. Gpc3, Jund), immune response (e.g. C3, C4a), and others (e.g. Lrp8, Msln, Klkc1, Epn3). Gene ontology analysis revealed several significantly enriched functional inter-relationships between genes influenced by non-obese T2DM. Protein–protein interaction analysis demonstrated that Stat is a potential key gene influenced by non-obese T2DM.

Conclusions

Non-obese T2DM alters cardiac gene expression profile. The altered genes may be involved in the development of cardiac pathologies and could be potential therapeutic targets in non-obese T2DM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0424-3) contains supplementary material, which is available to authorized users.

Remifentanil Preconditioning Reduces Postischemic Myocardial Infarction and Improves Left Ventricular Performance via Activation of the Janus Activated Kinase-2/Signal Transducers and Activators of Transcription-3 Signal Pathway and Subsequent Inhibition of Glycogen Synthase Kinase-3β in Rats

OBJECTIVES

Remifentanil preconditioning attenuates myocardial ischemia reperfusion injury, but the underlying mechanism is incompletely understood. The Janus activated kinase-2 (JAK2)/signal transducers and activators of transcription-3 (STAT3) and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways are critical in both ischemic and pharmacologic preconditioning cardioprotection, which involve the inactivation of glycogen synthase kinase-3β. We hypothesized that remifentanil preconditioning confers cardioprotection via the JAK2/STAT3 and/or PI3K/Akt activation-mediated glycogen synthase kinase-3β inhibition.

DESIGN

Pharmacologic intervention.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

In vivo and in vitro treatments.

MEASUREMENTS AND MAIN RESULTS

Male Sprague-Dawley rats (n = 6 per group) were sham operated or subjected to myocardial ischemia reperfusion injury. The JAK2 inhibitor AG490 (3 mg/kg), the PI3K inhibitor wortmannin (15 μg/kg), or the glycogen synthase kinase-3β inhibitor SB216763 (600 μg/kg) were given before inducing in vivo myocardial ischemia reperfusion injury achieved by occluding coronary artery for 30 minutes followed by 120 minutes of reperfusion in the absence or presence of remifentanil preconditioning (6 μg/kg/min). Also, isolated rat hearts were Langendorff perfused and subjected to 30 minutes of global ischemia and 120 minutes of reperfusion without or with remifentanil preconditioning (100 ng/mL) in the presence or absence of AG490 and/or SB216763. Isolated rat cardiomyocytes and H9C2 cells were subjected to hypoxia/reoxygenation alone or in combination with AG490 (100 μM), wortmannin (100 nM), or SB216763 (3 μM) without or with remifentanil preconditioning (2.5 μM). Remifentanil preconditioning reduced postischemic myocardial infarction and hemodynamic dysfunction induced by myocardial ischemia reperfusion injury concomitant with increased phosphorylation of STAT3 at tyr-705 (p-STAT3) and glycogen synthase kinase-3β but not Akt. AG490 but not wortmannin cancelled remifentanil preconditioning cardioprotection, and SB216763 restored it despite the presence of AG490. In Langendorff-perfused hearts, AG490-mediated cancellation of remifentanil preconditioning cardioprotection in attenuating postischemic myocardial infarction and creatinine kinase-MB release was reverted by concomitant administration of SB216763. Remifentanil preconditioning also attenuated posthypoxic cardiomyocyte injury and increased p-STAT3 and glycogen synthase kinase-3β in isolated primary cardiomyocytes and H9C2 cells. STAT3 gene knockdown with specific synthetic RNA cancelled remifentanil preconditioning cardioprotection, whereas glycogen synthase kinase-3β gene knockdown, which per se did not affect STAT3 under hypoxia/reoxygenation condition, preserved remifentanil preconditioning cardioprotection regardless of STAT3 abrogation.

CONCLUSIONS

Remifentanil preconditioning confers cardioprotection primarily via activation of JAK2/STAT3 signaling that can function independent of PI3K/Akt activation. Glycogen synthase kinase-3β is a critical downstream effector of remifentanil preconditioning cardioprotection.

Propofol ameliorates hyperglycemia-induced cardiac hypertrophy and dysfunction via heme oxygenase-1/signal transducer and activator of transcription 3 signaling pathway in rats

OBJECTIVES

Heme oxygenase-1 is inducible in cardiomyocytes in response to stimuli such as oxidative stress and plays critical roles in combating cardiac hypertrophy and injury. Signal transducer and activator of transcription 3 plays a pivotal role in heme oxygenase-1-mediated protection against liver and lung injuries under oxidative stress. We hypothesized that propofol, an anesthetic with antioxidant capacity, may attenuate hyperglycemia-induced oxidative stress in cardiomyocytes via enhancing heme oxygenase-1 activation and ameliorate hyperglycemia-induced cardiac hypertrophy and apoptosis via heme oxygenase-1/signal transducer and activator of transcription 3 signaling and improve cardiac function in diabetes.

DESIGN

Treatment study.

SETTING

Research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

In vivo and in vitro treatments.

MEASUREMENTS AND MAIN RESULTS

At 8 weeks of streptozotocin-induced type 1 diabetes in rats, myocardial 15-F2t-isoprostane was significantly increased, accompanied by cardiomyocyte hypertrophy and apoptosis and impaired left ventricular function that was coincident with reduced heme oxygenase-1 activity and signal transducer and activator of transcription 3 activation despite an increase in heme oxygenase-1 protein expression as compared to control. Propofol infusion (900 μg/kg/min) for 45 minutes significantly improved cardiac function with concomitantly enhanced heme oxygenase-1 activity and signal transducer and activator of transcription activation. Similar to the changes seen in diabetic rat hearts, high glucose (25 mmol/L) exposure for 48 hours led to cardiomyocyte hypertrophy and apoptosis, both in primary cultured neonatal rat cardiomyocytes and in H9c2 cells compared to normal glucose (5.5 mmol/L). Hypertrophy was accompanied by increased reactive oxygen species and malondialdehyde production and caspase-3 activity. Propofol, similar to the heme oxygenase-1 inducer cobalt protoporphyrin, significantly increased cardiomyocyte heme oxygenase-1 and p-signal transducer and activator of transcription protein expression and heme oxygenase-1 activity and attenuated high-glucose-mediated cardiomyocyte hypertrophy and apoptosis and reduced reactive oxygen species and malondialdehyde production (p < 0.05). These protective effects of propofol were abolished by heme oxygenase-1 inhibition with zinc protoporphyrin and by heme oxygenase-1 or signal transducer and activator of transcription 3 gene knockdown.

CONCLUSIONS

Heme oxygenase-1/signal transducer and activator of transcription 3 signaling plays a critical role in propofol-mediated amelioration of hyperglycemia-induced cardiomyocyte hypertrophy and apoptosis, whereby propofol improves cardiac function in diabetic rats.

Cardioprotection from emulsified isoflurane postconditioning is lost in rats with streptozotocin-induced diabetes due to the impairment of Brg1/Nrf2/STAT3 signalling

IsoPostC confers cardioprotection against myocardial IRI in non-diabetic rats but loses its effectiveness in diabetes, which may be mainly due to the impairment/reduction of Brg1/Nrf2/STAT3.

Hyperglycemia Abrogates Ischemic Postconditioning Cardioprotection by Impairing AdipoR1/Caveolin-3/STAT3 Signaling in Diabetic Rats

Signal transducer and activator of transcription 3 (STAT3) activation is key for ischemic postconditioning (IPo) to attenuate myocardial ischemia-reperfusion injury (MIRI), but IPo loses cardioprotection in diabetes in which cardiac STAT3 activation is impaired and adiponectin (APN) reduced. We found that IPo increased postischemic cardiomyocyte-derived APN, activated mitochondrial STAT3 (mitoSTAT3), improved mitochondrial function, and attenuated MIRI in wild-type but not in APN knockout (Adipo(-/-)) mice subjected to 30 min coronary occlusion, followed by 2 or 24 h of reperfusion. Hypoxic postconditioning-induced protection against hypoxia/reoxygenation injury was lost in Adipo(-/-) cardiomyocytes but restored by recombinant APN, but this APN beneficial effect was abolished by specific STAT3 or APN receptor 1 (AdipoR1) gene knockdown, or caveolin-3 (Cav3) disruption. APN activated cardiac STAT3 and restored IPo cardioprotection in 4-week diabetic rats where AdipoR1 and Cav3 were functionally interactive but not in 8-week diabetic rats whose cardiac Cav3 was severely reduced and AdipoR1/Cav3 signaling impaired. We concluded that IPo activates mitoSTAT3 through APN/AdipoR1/Cav3 pathway to confer cardioprotection, whereas in diabetes, IPo loses cardioprotection due to impaired APN/AdipoR1/Cav3 signaling. Therefore, effective means that may concomitantly activate APN and repair APN signaling (i.e., AdipoR1/Cav3) in diabetes may represent promising avenues in the treatment of MIRI in diabetes.

Swimming training attenuates the morphological reorganization of the myocardium and local inflammation in the left ventricle of growing rats with untreated experimental diabetes

Diabetic cardiomyopathy is associated with cardiac remodeling, myocardial dysfunction, low-grade inflammation, and reduced cardiac adiponectin in patients with type 1 diabetes mellitus (T1DM). Alternatively, physical exercise is an important strategy for the management of diabetes. This study aimed to investigate the influence of low-intensity swimming training in cardiac cytokines, structural remodeling, and cardiomyocyte contractile dysfunction in growing rats with untreated experimental DM. Thirty-day-old male Wistar rats were divided into four groups (n=14, per group): sedentary control (SC), exercised control (EC), sedentary diabetic (SD), and exercised diabetic (ED). Diabetes was induced by streptozotocin (60 mg kg(-1), i.p.). Animals from exercised groups swam (5 days/week, 90 min/day, loading up to 5% body weight around the animal's chest) for 8 weeks. The left ventricle (LV) was removed for molecular, morphological, and cardiomyocyte mechanical analysis. Diabetic animals presented cardiac remodeling with myocardial histoarchitectural disorganization, fibrosis, and necrosis. The capillary density was lower in diabetic animals. LV cardiomyocytes from diabetic animals exhibited more prolonged time to the peak of contraction and time to half relaxation than those from control animals. The cardiac levels of interleukin 10, nitric oxide, and total and high molecular weight (HMW) adiponectin were significantly decreased in diabetic animals. Exercise training reduced the level of TNF-α, increased capillary density, and attenuated the histopathological parameters assessed in diabetic rats. In conclusion, the cardiac structural remodeling coexists with reduced levels of total and HMW adiponectin, inflammation, and cardiomyocyte contractility dysfunction in experimental DM. More important, low-intensity swimming training attenuates part of these pathological changes, indicating the beneficial role for exercise in untreated T1DM.

N-Acetylcysteine Restores Sevoflurane Postconditioning Cardioprotection against Myocardial Ischemia-Reperfusion Injury in Diabetic Rats

The effect of sevoflurane postconditioning (sevo-postC) cardioprotection is compromised in diabetes which is associated with increased oxidative stress. We hypothesized that antioxidant N-Acetylcysteine may enhance or restore sevo-postC cardioprotection in diabetes. Control or streptozotocin-induced Type 1 diabetic rats were either untreated or treated with N-Acetylcysteine for four weeks starting at five weeks after streptozotocin injection and were subjected to myocardial ischemia-reperfusion injury (IRI), in the absence or presence of sevo-postC. Diabetes showed reduction of cardiac STAT3 activation (p-STAT3) and adiponectin with concomitantly increase of FoxO1 and CD36, which associated with reduced sevo-postC cardioprotection. N-Acetylcysteine and sevo-postC synergistically reduced the infarct size in diabetic groups. N-Acetylcysteine remarkably increased cardiac p-STAT3 which was further enhanced by sevo-postC. N-Acetylcysteine but not sevo-postC decreased myocardial FoxO1 while sevo-postC but not N-Acetylcysteine significantly increased myocardiac adiponectin in diabetic rats. It is concluded that late stage diabetic rats displayed reduction of cardiac p-STAT3, adiponectin deficiency, and increase of FoxO1 and CD36 expression, which may be responsible for the loss of myocardial responsiveness to sevo-postC cardioprotection. N-Acetylcysteine restored Sevo-postC cardioprotection in diabetes possibly through enhancing cardiac p-STAT3 and adiponectin and reducing Fox1 and CD36.

Melatonin prevents hyperglycemia in a model of sleep apnea

OBJECTIVE

Obstructive sleep apnea is a common disorder associated with aging and obesity. Apneas cause repeated arousals, intermittent hypoxia, and oxidative stress. Changes in glucolipidic profile occur in apnea patients, independently of obesity. Animal models of sleep apnea induce hyperglycemia. This study aims to evaluate the effect of the antioxidants melatonin and N-acetylcysteine on glucose, triglyceride, and cholesterol levels in animals exposed to intermittent hypoxia.

MATERIALS AND METHODS

Two groups of Balb/c mice were exposed to intermittent hypoxia (n = 36) or sham intermittent hypoxia (n = 36) for 35 days. The intermittent hypoxia group underwent a total of 480 cycles of 30 seconds reducing the inspired oxygen fraction from 21% to 7 ± 1% followed by 30 seconds of normoxia, during 8 hours daily. Melatonin or N-acetylcysteine were injected intraperitonially daily from day 21 on.

RESULTS

At day 35, glucose levels were significantly higher in the intermittent hypoxia group than in the control group. The intermittent hypoxia groups receiving N-acetylcysteine and vehicle showed higher glucose levels than the group receiving melatonin. The lipid profile was not affected by intermittent hypoxia or antioxidant administration.

CONCLUSIONS

The present results suggest that melatonin prevents the well-recognized increase in glucose levels that usually follows exposure to intermittent hypoxia. Further exploration of the role of melatonin in sleep apnea is warranted.

Protective effects of fish oil, allopurinol, and verapamil on hepatic ischemia-reperfusion injury in rats

Background:

The major aim of this work was to study the protective effects of fish oil (FO), allopurinol, and verapamil on hepatic ischemia-reperfusion (IR)-induced injury in experimental rats.

Materials and Methods:

Sixty male Wistar albino rats were randomly assigned to six groups of 10 rats each. Group 1 served as a negative control. Group 2 served as hepatic IR control injury. Groups 3, 4, 5, and 6 received N-acetylcysteine (standard), FO, allopurinol, and verapamil, respectively, for 3 consecutive days prior to ischemia. All animals were fasted for 12 h, anesthetized and underwent midline laparotomy. The portal triads were clamped by mini-artery clamp for 30 min followed by reperfusion for 30 min. Blood samples were withdrawn for estimation of serum alanine transaminase (ALT) and aspartate transaminase (AST) activities as well as hepatic thiobarbituric acid reactive substances, reduced glutathione, myeloperoxidase, and total nitrate/nitrite levels, in addition to histopathological examination.

Results:

Fish oil, allopurinol, and verapamil reduced hepatic IR injury as evidenced by significant reduction in serum ALT and AST enzyme activities. FO and verapamil markedly reduced oxidative stress as compared to control IR injury. Levels of inflammatory biomarkers in liver were also reduced after treatment with FO, allopurinol, or verapamil. In accordance, a marked improvement of histopathological findings was observed with all of the three treatments.

Conclusion:

The findings of this study prove the benefits of FO, allopurinol, and verapamil on hepatic IR-induced liver injury and are promising for further clinical trials.

Inhibition of PKCβ2 overexpression ameliorates myocardial ischaemia/reperfusion injury in diabetic rats via restoring caveolin-3/Akt signaling

Activation of PKCβ (protein kinase Cβ) plays a critical role in myocardial I/R (ischaemia/reperfusion) injury in non-diabetic rodents. In the myocardium of diabetes, PKCβ2 overexpression is associated with increased vulnerability to post-ischaemic I/R injury with concomitantly impaired cardiomyocyte Cav (caveolin)-3 and Akt signalling compared with non-diabetic rats. We hypothesized that myocardial PKCβ overexpression in diabetes exacerbates myocardial I/R injury through impairing Cav-3/Akt signalling. Streptozotocin-induced diabetic rats were treated with the selective PKCβ inhibitor ruboxistaurin (RBX, 1 mg/kg per day) for 4 weeks, starting from 1 week after diabetes induction, before inducing myocardial I/R achieved by occluding the left descending coronary artery followed by reperfusion. Cardiac function was measured using a pressure-volume conductance system. In an in vitro study, cardiac H9C2 cells were exposed to high glucose (30 mmol/l) and subjected to hypoxia followed by reoxygenation (H/R) in the presence or absence of the selective PKCβ2 inhibitor CGP53353 (1 μmol/l), siRNAs of PKCβ2 or Cav-3 or Akt. Cell apoptosis and mitochondrial membrane potential were assessed by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) and JC-1 staining respectively. RBX significantly decreased post-ischaemic myocardial infarct size (35±5% compared with 49±3% in control, P<0.05) and attenuated cardiac dysfunction, and prevented the reduction in cardiac Cav-3 and enhanced phosphorylated/activated Akt (p-Akt) in diabetic rats (P<0.05). H/R increased cardiomyocyte injury under high glucose conditions as was evident by increased TUNEL-positive and increased JC-1 monomeric cells (P<0.05 compared with control), accompanied with increased PKCβ2 phosphorylation/activation and decreased Cav-3 expression. Either CGP53353 or PKCβ2 siRNA significantly attenuated all of these changes and enhanced p-Akt. Cav-3 gene knockdown significantly reduced p-Akt and increased post-hypoxic cellular and mitochondrial injury despite a concomitant reduction in PKCβ2 phosphorylation. PKCβ2 inhibition with RBX protects diabetic hearts from myocardial I/R injury through Cav-3-dependent activation of Akt.

Propofol Attenuates Small Intestinal Ischemia Reperfusion Injury through Inhibiting NADPH Oxidase Mediated Mast Cell Activation

Both oxidative stress and mast cell (MC) degranulation participate in the process of small intestinal ischemia reperfusion (IIR) injury, and oxidative stress induces MC degranulation. Propofol, an anesthetic with antioxidant property, can attenuate IIR injury. We postulated that propofol can protect against IIR injury by inhibiting oxidative stress subsequent from NADPH oxidase mediated MC activation. Cultured RBL-2H3 cells were pretreated with antioxidant N-acetylcysteine (NAC) or propofol and subjected to hydrogen peroxide (H2O2) stimulation without or with MC degranulator compound 48/80 (CP). H2O2 significantly increased cells degranulation, which was abolished by NAC or propofol. MC degranulation by CP further aggravated H2O2 induced cell degranulation of small intestinal epithelial cell, IEC-6 cells, stimulated by tryptase. Rats subjected to IIR showed significant increases in cellular injury and elevations of NADPH oxidase subunits p47(phox) and gp91(phox) protein expression, increases of the specific lipid peroxidation product 15-F2t-Isoprostane and interleukin-6, and reductions in superoxide dismutase activity with concomitant enhancements in tryptase and β-hexosaminidase. MC degranulation by CP further aggravated IIR injury. And all these changes were attenuated by NAC or propofol pretreatment, which also abrogated CP-mediated exacerbation of IIR injury. It is concluded that pretreatment of propofol confers protection against IIR injury by suppressing NADPH oxidase mediated MC activation.

Adiponectin ameliorates hyperglycemia-induced cardiac hypertrophy and dysfunction by concomitantly activating Nrf2 and Brg1

Hyperglycemia-induced oxidative stress is implicated in the development of cardiomyopathy in diabetes that is associated with reduced adiponectin (APN) and heme oxygenase-1 (HO-1). Brahma-related gene 1 (Brg1) assists nuclear factor-erythroid-2-related factor-2 (Nrf2) to activate HO-1 to increase myocardial antioxidant capacity in response to oxidative stress. We hypothesized that reduced adiponectin (APN) impairs HO-1 induction which contributes to the development of diabetic cardiomyopathy, and that supplementation of APN may ameliorate diabetic cardiomyopathy by activating HO-1 through Nrf2 and Brg1 in diabetes. Control (C) and streptozotocin-induced diabetic (D) rats were untreated or treated with APN adenovirus (1×10(9) pfu) 3 weeks after diabetes induction and examined and terminated 1 week afterward. Rat left ventricular functions were assessed by a pressure-volume conductance system, before the rat hearts were removed to perform histological and biochemical assays. Four weeks after diabetes induction, D rats developed cardiac hypertrophy evidenced as increased ratio of heart weight to body weight, elevated myocardial collagen I content, and larger cardiomyocyte cross-sectional area (all P<0.05 vs C). Diabetes elevated cardiac oxidative stress (increased 15-F2t-isoprostane, 4-hydroxynonenal generation, 8-hydroxy-2'-deoxyguanosine, and superoxide anion generation), increased myocardial apoptosis, and impaired cardiac function (all P<0.05 vs C). In D rats, myocardial HO-1 mRNA and protein expression were reduced which was associated with reduced Brg1 and nuclear Nrf2 protein expression. All these changes were either attenuated or prevented by APN. In primarily cultured cardiomyocytes (CMs) isolated from D rats or in the embryonic rat cardiomyocytes cell line H9C2 cells incubated with high glucose (HG, 25 mM), supplementation of recombined globular APN (gAd, 2μg/mL) reversed HG-induced reductions of HO-1, Brg1, and nuclear Nrf2 protein expression and attenuated cellular oxidative stress, myocyte size, and apoptotic cells. Inhibition of HO-1 by ZnPP (10μM) or small interfering RNA (siRNA) canceled all the above gAd beneficial effects. Moreover, inhibition of Nrf2 (either by the Nrf2 inhibitor luteolin or siRNA) or Brg1 (by siRNA) canceled gAd-induced HO-1 induction and cellular protection in CMs and in H9C2 cells incubated with HG. In summary, our present study demonstrated that APN reduced cardiac oxidative stress, ameliorated cardiomyocyte hypertrophy, and prevented left ventricular dysfunction in diabetes by concomitantly activating Nrf2 and Brg1 to facilitate HO-1 induction.

Amelioration of lipid peroxidation in vivo and in vitro by Satureja khozestanica essential oil in alloxan-induced diabetic rats

Background

We examined possible protective effect of Satureja khozestanica essential oil (SKE) on in vivo and in vitro lipid peroxidation in alloxan-induced Type 1 diabetic rats.

Methods

Thirty Sprage-dawley male rats were divided into three groups randomly; group one as control, group two diabetic untreatment, and group three treatments with SKE by 500 ppm in drinking water, respectively. Diabetes was induced in the second and third groups by alloxan injection subcutaneously. After 8 weeks, animals were anaesthetized, livers and kidneys were then removed immediately and used fresh or kept frozen until their lipid peroxidation analysis. Lipid peroxidation was determined by measurement of thiobarbituric acid reactive substances (TBARS). Blood samples were also collected before killing to measure the levels of fasting blood suger (FBS) and lipid peroxidation.

Results

SKE significantly inhibited the levels of FBS, TBARS serum and kidney content in treated group compared with the diabetic untreated group. Also the levels of malonedialdehyde liver content unaltered in treated group. SKE significantly inhibited LDL oxidation in vitro.

Conclusions

The findings showed that SKE exerts beneficial effects on the lipid peroxidation in alloxan-induced Type 1 diabetic rats.

N-acetylcysteine reduces oxidative stress, nuclear factor‑κB activity and cardiomyocyte apoptosis in heart failure

The roles of oxidative stress on nuclear factor (NF)‑κB activity and cardiomyocyte apoptosis during heart failure were examined using the antioxidant N‑acetylcysteine (NAC). Heart failure was established in Japanese white rabbits with intravenous injections of doxorubicin, with ten rabbits serving as a control group. Of the rabbits with heart failure, 12 were not treated (HF group) and 13 received NAC (NAC group). Cardiac function was assessed using echocardiography and hemodynamic analysis. Myocardial cell apoptosis, apoptosis‑related protein expression, NF‑κBp65 expression and activity, total anti‑oxidative capacity (tAOC), 8‑iso‑prostaglandin F2α (8‑iso‑PGF2α) expression and glutathione (GSH) expression levels were determined. In the HF group, reduced tAOC, GSH levels and Bcl‑2/Bax ratios as well as increased 8‑iso‑PGF2α levels and apoptosis were observed (all P<0.05), which were effects that were attenuated by the treatment with NAC. NF‑κBp65 and iNOS levels were significantly higher and the P‑IκB‑α levels were significantly lower in the HF group; expression of all three proteins returned to pre‑HF levels following treatment with NAC. Myocardial cell apoptosis was positively correlated with left ventricular end-diastolic pressure (LVEDP), NF‑κBp65 expression and 8‑iso‑PGF2α levels, but negatively correlated with the maximal and minimal rates of increase in left ventricular pressure (+dp/dtmax and ‑dp/dtmin, respectively) and the Bcl‑2/Bax ratio (all P<0.001). The 8‑iso‑PGF2α levels were positively correlated with LVEDP and negatively correlated with +dp/dtmax and ‑dp/dtmin (all P<0.001). The present study demonstrated that NAC increased the antioxidant capacity, decreased the NF‑κB activation and reduced myocardial cell apoptosis in an in vivo heart failure model.

The role of adiponectin signaling in metabolic syndrome and cancer

The increased prevalence of obesity has mandated extensive research focused on mechanisms responsible for associated clinical complications. Emerging from the focus on adipose tissue biology as a vitally important adipokine is adiponectin which is now believed to mediate anti-diabetic, anti-atherosclerotic, anti-inflammatory, cardioprotective and cancer modifying actions. Adiponectin mediates these primarily beneficial effects via direct signaling effects and via enhancing insulin sensitivity via crosstalk with insulin signaling pathways. Reduced adiponectin action is detrimental and occurs in obesity via decreased circulating levels of adiponectin action or development of adiponectin resistance. This review will focus on cellular mechanisms of adiponectin action, their crosstalk with insulin signaling and the resultant role of adiponectin in cardiovascular disease, diabetes and cancer and reviews data from in vitro cell based studies through animal models to clinical observations.

Direct effects of adipokines on the heart: focus on adiponectin

Cardiovascular disease, including heart failure, is a principal cause of death in individuals with obesity and diabetes. However, the mechanisms of obesity- and diabetes-induced heart disease are multifaceted and remain to be clearly defined. Of relevance to this review, there is currently great research and clinical interest in the endocrine effects of adipokines on the myocardium and their role in heart failure. We will discuss the potential significance of adipokines in the pathogenesis of heart failure via their ability to regulate remodeling events including metabolism, hypertrophy, fibrosis, and cell death. As an excellent example, we will first focus on adiponectin which is best known to confer numerous cardioprotective effects. However, we comprehensively discuss the existing literature that highlights it would be naive to assume that this was always the case. We also focus on lipocalin-2 which mediates pro-inflammatory and pro-apoptotic effects. It is important when studying actions of adipokines to integrate cellular and mechanistic analyses and translate these to physiologically relevant in vivo models and clinical studies. However, assimilating studies on numerous cardiac remodeling events which ultimately dictate cardiac dysfunction into a unifying conclusion is challenging. Nevertheless, there is undoubted potential for the use of adipokines as robust biomarkers and appropriate therapeutic targets in heart failure.

Diosmin pretreatment improves cardiac function and suppresses oxidative stress in rat heart after ischemia/reperfusion

Reperfusion of ischemic tissue leads to the generation of oxygen derived free radicals which plays an important role in cellular damage. Objective of the current study is to evaluate the cardio-protective and antioxidant effect of diosmin on ischemia-reperfusion related cardiac dysfunction, oxidative stress and apoptosis. Diosmin (50 and 100 mg/kg body weight (bw)) was given every day to the rats orally throughout the experimental period. Ischemia/reperfusion protocol was carried out ex vivo using langendorff perfusion method and the cardiac functional recovery was assessed in terms of percentage rate pressure product. Coronary effluents of LDH and CK-MB activities, antioxidant enzyme activities, lipid peroxidation products, activity of TCA cycle enzymes were evaluated. Moreover, in vitro superoxide anion and hydroxyl radical scavenging potential of diosmin was also quantified. Finally, quantitative real-time PCR was used for assessing Bcl-2 mRNA expression in heart. Cardiac functional recovery was impaired after reperfusion compared with continuously perfused heart. It was significantly prevented by diosmin treatment. Impaired antioxidant enzyme activities and elevated lipid peroxidation products level were also significantly suppressed. The activity of TCA cycle enzymes was protected against reperfusion stress. Down regulated Bcl-2 was also significantly increased. This study concluded that diosmin pretreatment prevents all the impaired patterns including cardiac function, oxidative stress and apoptosis associated with reperfusion in control heart by its antioxidant role.

The mechanism of sevoflurane preconditioning-induced protections against small intestinal ischemia reperfusion injury is independent of mast cell in rats

The study aimed to investigate whether sevoflurane preconditioning can protect against small intestinal ischemia reperfusion (IIR) injury and to explore whether mast cell (MC) is involved in the protections provided by sevoflurane preconditioning. Sprague-Dawley rats exposed to sevoflurane or treated with MC stabilizer cromolyn sodium (CS) were subjected to 75-minute superior mesenteric artery occlusion followed by 2-hour reperfusion in the presence or absence of MC degranulator compound 48/80 (CP). Small intestinal ischemia reperfusion resulted in severe intestinal injury as demonstrated by significant elevations in intestinal injury scores and p47^phox and gp91^phox, ICAM-1 protein expressions and malondialdehyde and IL-6 contents, and MPO activities as well as significant reductions in SOD activities, accompanied with concomitant increases in mast cell degranulation evidenced by significant increases in MC counts, tryptase expression, and β-hexosaminidase concentrations, and those alterations were further upregulated in the presence of CP. Sevoflurane preconditioning dramatically attenuated the previous IIR-induced alterations except MC counts, tryptase, and β-hexosaminidase which were significantly reduced by CS treatment. Furthermore, CP exacerbated IIR injury was abrogated by CS but not by sevoflurane preconditioning. The data collectively indicate that sevoflurane preconditioning confers protections against IIR injury, and MC is not involved in the protective process.

N-Acetylcysteine and allopurinol up-regulated the Jak/STAT3 and PI3K/Akt pathways via adiponectin and attenuated myocardial postischemic injury in diabetes

N-Acetylcysteine (NAC) and allopurinol (ALP) synergistically reduce myocardial ischemia reperfusion (MI/R) injury in diabetes. However, the mechanism is unclear. We postulated that NAC and ALP attenuated diabetic MI/R injury by up-regulating phosphatidylinositol 3-kinase/Akt (PI3K/Akt) and Janus kinase 2/signal transducer and activator of transcription-3 (JAK2/STAT3) pathways subsequent to adiponectin (APN) activation. Control (C) or streptozotocin-induced diabetic rats (D) were untreated or treated with NAC and ALP followed by MI/R. D rats displayed larger infarct size accompanied by decreased phosphorylation of Akt, STAT3 and decreased cardiac nitric oxide (NO) and APN levels. NAC and ALP decreased MI/R injury in D rats, enhanced phosphorylation of Akt and STAT3, and increased NO and APN. High glucose and hypoxia/reoxygenation exposure induced cell death and Akt and STAT3 inactivation in cultured cardiomyocytes, which were prevented by NAC and ALP. The PI3K inhibitor wortmannin and Jak2 inhibitor AG490 abolished the protection of NAC and ALP. Similarly, APN restored posthypoxic Akt and STAT3 activation and decreased cell death in cardiomyocytes. Gene silencing with AdipoR2 siRNA or STAT3 siRNA but not AdipoR1 siRNA abolished the protection of NAC and ALP. In conclusion, NAC and ALP prevented diabetic MI/R injury through PI3K/Akt and Jak2/STAT3 and cardiac APN may serve as a mediator via AdipoR2 in this process.

Susceptibility to myocardial ischemia reperfusion injury at early stage of type 1 diabetes in rats

Background

Large body of evidences accumulated in clinical and epidemiological studies indicate that hearts of diabetic subjects are more sensitive to ischemia reperfusion injury (IRI), which results in a higher rate of mortality at post-operation than that of non-diabetes. However, experimental results are equivocal and point to either increased or decreased susceptibility of the diabetic hearts to IRI, especially at the early stage of the disease. The present study was designed to test the hypothesis that the duration/severity of the indexed ischemia is a major determinant of the vulnerability to myocardial IRI at early stage of diabetes.

Methods

Four weeks streptozotocin (STZ)-induced diabetic (D) and non-diabetic (C) Sprague–Dawley rats were randomly assigned to receive 30 or 45 min of left anterior descending artery ligation followed by 2 or 3 hours of reperfusion, respectively. Cardiac function was recorded by using Pressure-Volume (PV) conduction system. Myocardial infarct size was determined with triphenyltetrazolium chloride staining. Plasma Creatine kinase-MB (CK-MB), Lactate dehydrogenase (LDH) release, myocardial nitric oxide(NO) content and nitrotyrosine formation, 15-F_2t-Isoprostane and plasma superoxide dismutase (SOD) were measured with colorimetric assays. Cardiomyocyte apoptosis was assessed by TUNEL staining. Myocardial TNFα, Caspase-3, STAT3, Akt, and GSK-3β were determined by Western blotting.

Results

Prolongation of ischemia but not reperfusion from 30 min to 45 min significantly increased infarct size in D compared to C rats (P < 0.05), accompanied with significantly increased plasma CK-MB (P < 0.05). Prolongation of the duration of either ischemia or reperfusion significantly increased plasma LDH release and myocardial 15-F_2t-Isoprostane and reduced plasma SOD activity, with concomitant reduction of myocardial NO and increase of nitrotyrosine formation in D relative to C (P < 0.05). Prolongation of ischemia and reperfusion significantly reduced left ventricular ejection fraction and increased the peak rate of pressure, accompanied with increased end systolic pressure in D relative to C rats (P < 0.05) but reduced phosphorylations of myocardial STAT3 at site Ser727 and Akt at site Ser473 as well as GSK-3β at Ser 9 (P < 0.05).

Conclusions

Diabetic hearts, even at early stage of the disease are more sensitive to IRI, and this increased severity of post-ischemic myocardial injury depends more on the duration of ischemia than that of reperfusion.

Adiponectin: mechanisms and new therapeutic approaches for restoring diabetic heart sensitivity to ischemic post-conditioning

Systemic inflammatory response following myocardial ischemia-reperfusion injury (IRI) to a specific organ may cause injuries. Ischemic post-conditioning (IPostC) has emerged as a promising method for myocardial protection against IRI both in experimental and in clinical settings. Enhancement of endogenous nitric oxide (NO) is one of the major mechanisms by which IPostC confers cardioprotection. However, the sensitivity of the diabetic heart to IPostC is impaired and the underlying mechanism is unknown. Adiponectin (APN) is an adipocytederived plasma protein with anti-diabetic and anti-inflammatory properties. Plasma levels of APN are decreased in obese subjects and in patients with type 2 diabetes. APN supplementation has been shown to increase NO production and attenuate myocardial IRI in normal (non-diabetic) animals. However, the effect of APN on myocardial injury in diabetic subjects, especially its potential in restoring the sensitivity of the diabetic heart to IPostC has not been investigated. In the current paper, we discussed the possible reasons why the myocardium of diabetic subjects loses sensitivity to IPostC and also highlighted the potential effectiveness and mechanism of APN in restoring IPostC cardioprotection in diabetes. This review proposes to conduct studies that may facilitate the development of novel and optimal therapies to enhance cardioprotection in patients with severe diseases such as diabetes.

N-acetylcysteine and allopurinol confer synergy in attenuating myocardial ischemia injury via restoring HIF-1α/HO-1 signaling in diabetic rats

OBJECTIVES

To determine whether or not the antioxidants N-acetylcysteine (NAC) and allopurinol (ALP) confer synergistic cardioprotection against myocardial ischemia/reperfusion (MI/R) injury by stabilizing hypoxia inducible factor 1α (HIF-1α)/heme oxygenase 1 (HO-1) signaling in diabetic myocardium.

METHODS

Control or diabetic [streptozotocin (STZ)-induced] Sprague Dawley rats received vehicle or NAC, ALP or their combination for four weeks starting one week after STZ injection. The animals were then subjected to thirty minutes of coronary artery occlusion followed by two hours reperfusion in the absence or presence of the selective HO-1 inhibitor, tin protoporphyrin-IX (SnPP-IX) or the HIF-1α inhibitor 2-Methoxyestradiol (2ME2). Cardiomyocytes exposed to high glucose were subjected to hypoxia/re-oxygenation in the presence or absence of HIF-1α and HO-1 achieved by gene knock-down with related siRNAs.

RESULTS

Myocardial and plasma levels of 15-F2t-isoprostane, an index of oxidative stress, were significantly increased in diabetic rats while cardiac HO-1 protein and activity were reduced; this was accompanied with reduced cardiac protein levels of HIF-1α, and increased post-ischemic myocardial infarct size and cellular injury. NAC and ALP given alone and in particular their combination normalized cardiac levels of HO-1 and HIF-1α protein expression and prevented the increase in 15-F2t-isoprostane, resulting in significantly attenuated post-ischemic myocardial infarction. NAC and ALP also attenuated high glucose-induced post-hypoxic cardiomyocyte death in vitro. However, all the above protective effects of NAC and ALP were cancelled either by inhibition of HO-1 or HIF-1α with SnPP-IX and 2ME2 in vivo or by HO-1 or HIF-1α gene knock-down in vitro.

CONCLUSION

NAC and ALP confer synergistic cardioprotection in diabetes via restoration of cardiac HIF-1α and HO-1 signaling.

Hyperglycemia-induced protein kinase C β2 activation induces diastolic cardiac dysfunction in diabetic rats by impairing caveolin-3 expression and Akt/eNOS signaling

Protein kinase C (PKC)β2 is preferably overexpressed in the diabetic myocardium, which induces cardiomyocyte hypertrophy and contributes to diabetic cardiomyopathy, but the underlying mechanisms are incompletely understood. Caveolae are critical in signal transduction of PKC isoforms in cardiomyocytes. Caveolin (Cav)-3, the cardiomyocyte-specific caveolar structural protein isoform, is decreased in the diabetic heart. The current study determined whether PKCβ2 activation affects caveolae and Cav-3 expression. Immunoprecipitation and immunofluorescence analysis revealed that high glucose (HG) increased the association and colocalization of PKCβ2 and Cav-3 in isolated cardiomyocytes. Disruption of caveolae by methyl-β-cyclodextrin or Cav-3 small interfering (si)RNA transfection prevented HG-induced PKCβ2 phosphorylation. Inhibition of PKCβ2 activation by compound CGP53353 or knockdown of PKCβ2 expression via siRNA attenuated the reductions of Cav-3 expression and Akt/endothelial nitric oxide synthase (eNOS) phosphorylation in cardiomyocytes exposed to HG. LY333531 treatment (for a duration of 4 weeks) prevented excessive PKCβ2 activation and attenuated cardiac diastolic dysfunction in rats with streptozotocin-induced diabetes. LY333531 suppressed the decreased expression of myocardial NO, Cav-3, phosphorylated (p)-Akt, and p-eNOS and also mitigated the augmentation of O2(-), nitrotyrosine, Cav-1, and iNOS expression. In conclusion, hyperglycemia-induced PKCβ2 activation requires caveolae and is associated with reduced Cav-3 expression in the diabetic heart. Prevention of excessive PKCβ2 activation attenuated cardiac diastolic dysfunction by restoring Cav-3 expression and subsequently rescuing Akt/eNOS/NO signaling.

Nano-titanium dioxide induced cardiac injury in rat under oxidative stress

Heart diseases, which are related to oxidative stress (OS), negatively affect millions of people from kids to the elderly. Titanium dioxide (TiO2) has widespread applications in our daily life, especially nanoscale TiO2. Compared to the high risk of particulate matter (≤2.5μm) in air to heart disease patients, related research of TiO2 on diseased body is still unknown, which suggest us to explore the potential effects of nanoscale and microscale TiO2 to heart under OS conditions. Here, we used alloxan to induce OS conditions in rat, and investigated the response of heart tissue to TiO2 in healthy and alloxan treated rats. Compared with NMs treatment only, the synergistic interaction between OS conditions and nano-TiO2 significantly reduced the heart-related function indexes, inducing pathological changes of myocardium with significantly increased levels of cardiac troponin I and creatine kinase-MB. In contrast with the void response of micro-TiO2 to heart functions in alloxan treated rats, aggravation of OS conditions might play an important role in cardiac injury after alloxan and nano-TiO2 dual exposure. Our results demonstrated that OS conditions enhanced the adverse effects of nano-TiO2 to heart, suggesting that the use of NMs in stressed conditions (e.g., drug delivery) needs to be carefully monitored.

Antioxidant N-acetylcysteine attenuates the reduction of Brg1 protein expression in the myocardium of type 1 diabetic rats

Brahma-related gene 1 (Brg1) is a key gene in inducing the expression of important endogenous antioxidant enzymes, including heme oxygenase-1 (HO-1) which is central to cardioprotection, while cardiac HO-1 expression is reduced in diabetes. It is unknown whether or not cardiac Brg1 expression is reduced in diabetes. We hypothesize that cardiac Brg1 expression is reduced in diabetes which can be restored by antioxidant treatment with N-acetylcysteine (NAC). Control (C) and streptozotocin-induced diabetic (D) rats were treated with NAC in drinking water or placebo for 4 weeks. Plasma and cardiac free15-F2t-isoprostane in diabetic rats were increased, accompanied with increased plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6), while cardiac Brg1, p-STAT3 and HO-1 protein expression levels were significantly decreased. Left ventricle weight/body weight ratio was higher, while the peak velocities of early (E) and late (A) flow ratio was lower in diabetic than in C rats. NAC normalized tissue and plasma levels of 15-F2t-isoprostane, significantly increased cardiac Brg1, HO-1 and p-STAT3 protein expression levels and reduced TNF-alpha and IL-6, resulting in improved cardiac function. In conclusion, myocardial Brg1 is reduced in diabetes and enhancement of cardiac Brg1 expression may represent a novel mechanism whereby NAC confers cardioprotection.

Adipose tissue as regulator of vascular tone

Adipokines secreted by visceral, subcutaneous, and perivascular adipocytes are involved in the regulation of vascular tone by acting as circulatory hormones (leptin, adiponectin, omentin, visfatin, angiotensin II, resistin, tumor necrosis factor-α, interleukin-6, apelin) and/or via local paracrine factors (perivascular adipocyte-derived relaxing and contractile factors). Vascular tone regulation by adipokines is compromised in obesitas and obesity-related disorders. Hypoxia created in growing adipose tissue dysregulates synthesis of vasoactive adipokines in favor of harmful proinflammatory adipokines, while the levels of the cardioprotective adipokines adiponectin and omentin decrease. Considering the potential of the role of adipokines in obesity-related vascular diseases, strategies to counter these diseases by targeting the adipokines are discussed.

Adiponectin: anti-inflammatory and cardioprotective effects

Adipose tissue is an endocrine organ that plays an essential role in regulating several metabolic functions through the secretion of biological mediators called "adipokines". Dysregulation of adipokines plays a crucial role in obesity-related diseases. Adiponectin (APN) is the most abundant adipokine accounting for the 0.01% of total serum protein, and is involved in a wide variety of physiological processes including energy metabolism, inflammation, and vascular physiology. APN plasma levels are reduced in individuals with obesity, type 2 diabetes and coronary artery disease, all traits with low-grade chronic inflammation. It is has been suggested that the absence of APN anti-inflammatory effects may be a contributing factor to this inflammation. APN inhibits the expression of tumor necrosis factor-α-induced endothelial adhesion molecules, macrophage-to-foam cell transformation, tumor necrosis factor-α expression in macrophages and adipose tissue, and smooth muscle cell proliferation. It also has anti-apoptotic and anti-oxidant effects, which play a role in its cardioprotective action. This review will focus on APN as an anti-inflammatory, anti-atherogenic and cardioprotective plasma protein.