Streptozotocin-induced Diabetic Rat Heart Research Articles

Ginsenoside Rb1 reduces oxidative/carbonyl stress damage and dysfunction of RyR2 in the heart of streptozotocin-induced diabetic rats

BackgroundOxidative stress may contribute to cardiac ryanodine receptor (RyR2) dysfunction in diabetic cardiomyopathy. Ginsenoside Rb1 (Rb1) is a major pharmacologically active component of ginseng to treat cardiovascular diseases. Whether Rb1 treat diabetes injured heart remains unknown. This study was to investigate the effect of Rb1 on diabetes injured cardiac muscle tissue and to further investigate its possible molecular pharmacology mechanisms.MethodsMale Sprague-Dawley rats were injected streptozotocin solution for 2 weeks, followed 6 weeks Rb1 or insulin treatment. The activity of SOD, CAT, Gpx, and the levels of MDA was measured; histological and ultrastructure analyses, RyR2 activity and phosphorylated RyR2(Ser2808) protein expression analyses; and Tunel assay were performed.ResultsThere was decreased activity of SOD, CAT, Gpx and increased levels of MDA in the diabetic group from control. Rb1 treatment increased activity of SOD, CAT, Gpx and decreased the levels of MDA as compared with diabetic rats. Neutralizing the RyR2 activity significantly decreased in diabetes from control, and increased in Rb1 treatment group from diabetic group. The expression of phosphorylation of RyR2 Ser2808 was increased in diabetic rats from control, and were attenuated with insulin and Rb1 treatment. Diabetes increased the apoptosis rate, and Rb1 treatment decreased the apoptosis rate. Rb1 and insulin ameliorated myocardial injury in diabetic rats.ConclusionsThese data indicate that Rb1 could be useful for mitigating oxidative damage, reduced phosphorylation of RyR2 Ser2808 and decreased the apoptosis rate of cardiomyocytes in diabetic cardiomyopathy.

Correction to: Basic fibroblast growth factor alleviates metabolic abnormalities in the heart of streptozotocin-induced diabetic rats

Correction to: Basic fibroblast growth factor alleviates metabolic abnormalities in the heart of streptozotocin-induced diabetic rats

Basic fibroblast growth factor alleviates metabolic abnormalities in the heart of streptozotocin-induced diabetic rats

Basic fibroblast growth factor alleviates metabolic abnormalities in the heart of streptozotocin-induced diabetic rats

Exercise and Urtica Dioica extract ameliorate mitochondrial function and the expression of cardiac muscle Nuclear Respiratory Factor 2 and Peroxisome proliferator-activated receptor Gamma Coactivator 1-alpha in STZ-induced diabetic rats

IntroductionDiabetes mellitus can affect and disrupt the levels of PGC1α and NRF2 proteins in the mitochondrial biogenesis pathway. Considering the anti-diabetic properties of Urtica Dioica extract and exercise, this study aimed to investigate the beneficial effects of Urtica Dioica extract and endurance activity on PGC1α and NRF2 protein levels in the streptozotocin-induced diabetic rat heart tissue. Materials and methods58 male Wistar rats were divided into five groups (N = 12) including: healthy control (HC), diabetes control (DC), diabetes Urtica Dioica (D-UD), diabetes exercise training (DT), and diabetes exercise training Urtica Dioica (DT-UD). Diabetes was induced intraperitoneally by STZ (45 mg/kg) injection. Two weeks after the induction of diabetes, the rats were stimulated to carry out the exercise (moderate intensity/5day/week) and the gavage of UD extract (50 mg/kg/day) was administered to the rats for six weeks.In this study, the western blotting method was used to measure the levels of PGC1α and NRF2 proteins. Moreover, cardiography was used to evaluate the functional parameters of the heart (ejection fraction & fractional shortening). Finally, the bioluminescence and ELISA methods were used to determine the content of adenosine triphosphate and citrate synthase. ResultsThe cardiac function parameters, the mitochondrial ATP and the CS content in DC group mice were impaired in comparison with the other study groups and showed a decreasing trend (P < 0.001). The treatment with EX + UD extract was able to minimize the rate of these disorders and acted as a protector of mitochondrial function. There were significant differences in the expression levels of NRF2 (F = 17.7, P = 0.001) and PGC-1α (F = 43.7, P = 0.001) mitochondrial proteins among the different groups. The levels of these proteins were significantly reduced in the DC group in comparison with the HC group (P < 0.001). The treatment with EX or UD extract increased the expression of PGC-1α and NRF2 proteins in the heart muscle of animals in the DT and D-UD groups in comparison with the DC group (P < 0.05). Moreover, the expression of these proteins was more pronounced in the DT-UD group. There was not a significant difference between the DT-UD group and the HC group regarding the expression of these proteins (P > 0.05). ConclusionsThe results of this study showed that treatment with EX and UD extract could treat the disorders which were caused by diabetes in the parameters of cardiac function. Moreover, it was able to improve the expression of the levels of proteins which were involved in mitochondrial biogenesis and its function. Finally, this kind of treatment could attract more attention to the roles of EX and UD extract in the prevention of cardiovascular complications in future studies.

Hyperbaric oxygen therapy mitigates left ventricular remodeling, upregulates MMP-2 and VEGF, and inhibits the induction of MMP-9, TGF-β1, and TNF-α in streptozotocin-induced diabetic rat heart

AimsHyperbaric oxygen (HBO) therapy has been widely used for the adjunctive treatment of diabetic wounds, and is currently known to influence left ventricular (LV) function. However, morphological and molecular repercussions of the HBO in the diabetic myocardium remain to be described. We aimed to investigate whether HBO therapy would mitigate adverse LV remodeling caused by streptozotocin (STZ)-induced diabetes. Main methodsSixty-day-old Male Wistar rats were divided into four groups: Control (n = 8), HBO (n = 7), STZ (n = 10), and STZ + HBO (n = 8). Diabetes was induced by a single STZ injection (60 mg/kg, i.p.). HBO treatment (100% oxygen at 2.5 atmospheres absolute, 60 min/day, 5 days/week) lasted for 5 weeks. LV morphology was evaluated using histomorphometry. Gene expression analyzes were performed for LV collagens I (Col1a1) and III (Col3a1), matrix metalloproteinases 2 (Mmp2) and 9 (Mmp9), and transforming growth factor-β1 (Tgfb1). The Immunoexpression of cardiac tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) were also quantified. Key findingsHBO therapy prevented LV concentric remodeling, heterogeneous myocyte hypertrophy, and fibrosis in diabetic rats associated with attenuation of leukocyte infiltration. HBO therapy also increased Mmp2 gene expression, and inhibited the induction of Tgfb1 and Mmp9 mRNAs caused by diabetes, and normalized TNF-α and VEGF protein expression. SignificanceHBO therapy had protective effects for the LV structure in STZ-diabetic rats and ameliorated expression levels of genes involved in cardiac collagen turnover, as well as pro-inflammatory and pro-angiogenic signaling.

The Comparison of Antioxidant Effect of Aspirin, Metformin, Atorvastatin and Captopril Co-administration in the Heart and Kidney Tissues of Diabetic Rats.

The present study investigated the effects of co-administration of aspirin, metformin, atorvastatin and captopril on serum lipid profile and oxidative stress in the heart and kidney of streptozotocin-induced diabetic rats. In this study, rats were randomly divided into the following eleven groups: control (Cont.), and diabetic (D), as well as 9 groups that were treated with metformin (M, 300 mg/kg) or aspirin (ASA, 120 mg/kg) alone or in different combinations with captopril (C, 50 mg/kg), or atorvastatin (AT, 40 mg/kg), as follows: (D + M), (D + ASA), (D + M + ASA), (D + M + C), (D + M + AT), (D + M + C + ASA), (D + M + C + AT), (D + M + AT + ASA), and (D + M + C + AT + ASA). The rats in treatment groups daily received drugs by gavage for six weeks. Finally, serum lipid profile and levels of oxidative markers in the heart and kidney tissues were evaluated. In diabetic rats, blood levels of glucose, cholesterol, TG (triglyceride), LDL (low-density lipoprotein), MDA (malondialdehyde) and AIP (atherogenic index of plasma) significantly increased but those of HDL (high-density lipoprotein) and total thiol as well as SOD (superoxide dismutase) and CAT (catalase) activities significantly decreased. Treatment with different combinations of C, ASA, AT and M significantly ameliorated these parameters. This study showed that co-administration of ASA, M, C and AT, could improve glucose and lipid metabolism and oxidative stress markers in the kidneys and heart tissues of diabetic rats more markedly than the administration of these drugs alone.

The Effects of Valsartan on Cardiac Function and Pro-Oxidative Parameters in the Streptozotocin-Induced Diabetic Rat Heart

Abstract Diabetes mellitus is a major risk factor for cardiovascular diseases, while cardiovascular diseases are a leading cause of morbidity and mortality worldwide. The renin–angiotensin– aldosterone system controls renal, cardiovascular, adrenal function and regulates fluid and electrolyte balance as well as blood pressure. Because of his role, inhibition of reninangiotensin-aldosteron system is another therapy approach that reduces the risk of diabetes and cardiovascular disease. In this study, our goal was to evaluate effect of valsartan,as inhibitor of angiotensin II receptor type 1, on cardiac tissue and function, with focus on cardiodynamic and oxidative stress. The present study was carried out on 20 adult male Wistar albino rats (8 week old and with body masses of 180-200 g). Rats were divided randomly into 2 groups (10 animals per group). Healthy animals treated with 1 μM of valsartan and streptozotocin-induced diabetic animals perfused with 1 μM of valsartan 4 weeks after the induction of diabetes. Our results demonstrated that acute application of valsartan has different effect on cardiodynamics in rat heart of diabetic and healthy animals but did not improve cardiac function in hyperglycemia-induced changes. A challenge for further investigations are studies with chronic or acute administration, alone or in combination with other angiotensin-converting-enzyme inhibitor in various models of diabetes.

EFFECT OF REGULAR EXERCISE ON EXPRESSION OF K ATP CHANNELS IN HEART OF DIABETIC RATS

There is abundant evidence that ATP sensitive potassium (KATP) channels play cytoprotective role in cardiac myocytes, allowing the cell to couple metabolic state to electrical activity of the cell membrane. In cardiac myocytes Kir6.2/SUR2A are the major subunits expressed. However, expression or function of KATP channels has been found to be impaired in the presence of persistent hyperglycemia in diabetes mellitus (DM). While regular exercise can improve hyperglycemic status in DM, its impact on the expression of KATP channels subunits in heart is unknown. PURPOSE: To assess the effect of regular exercise on expression of KATP channel subunits in heart of streptozotocin-induced diabetic rats. METHODS: Male Wistar rats (25 days old) were randomly divided into four groups, among them: sedentary control, trained control, sedentary diabetic, trained diabetic. Diabetes was induced by a single streptozotocin injection (100 mg/kg body weight), animals with fasting blood glucose levels ≥ 300 mg/dL were considered as diabetic. Groups with training program performed exercise on a treadmill (30 minutes daily, 5 days/week) for 8 weeks. At the end of the intervention, two subunits of cardiac KATP channel (SUR2A and Kir 6.2) were analyzed as indicators and quantitative analysis of these subunits was achieved with real-time RT–PCR. RESULTS: In control conditions, the regular exercise reduced Kir6.2 subunit mRNA levels significantly (76%; p=0.045) in heart. In diabetes, reduced Kir6.2 expression was also observed, and there was no difference in expression levels between sedentary diabetic and trained diabetic groups (P > 0.05). Otherwise, relative mRNA expression of the subunit SUR2A was increased in both sedentary diabetic and trained diabetic groups (80.33% and 86.08%, respectively). CONCLUSION: Collectively, our data demonstrate that the regular exercise modifies expression of KATP channel subunits of heart only in control conditions. However, the gene expression patterns of KATP channel subunits are different during diabetes, by increased SUR2A and decreased Kir6.2, which was not modified by exercise. These results may provide an opportunity to understand mechanisms leading to diabetic cardiomyopathy during stress and exercise in DM.

Altered mRNA Expression of ATP-Sensitive and Inward Rectifier Potassium Channel Subunits in Streptozotocin-Induced Diabetic Rat Heart and Aorta

Altered mRNA Expression of ATP-Sensitive and Inward Rectifier Potassium Channel Subunits in Streptozotocin-Induced Diabetic Rat Heart and Aorta

Polyphenol-enriched azuki bean (Vina angularis) extract reduces the oxidative stress and prevents DNA oxidation in the hearts of streptozotocin-induced early diabetic rats

We examined the changes in the heart of rats at the early stages of streptozotocin (STZ)-induced diabetes, and whether azuki bean extract (ABE) could influence these changes. The experimental diabetic rats received 0 or 40 mg/kg of ABE orally for 4 weeks, whereas the control group rats received distilled water. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) and expression of proteins associated with peroxisomal FA β-oxidation as well as oxidative stress markers were examined. The levels of peroxisomal ACOX1 and catalase of the diabetic groups were significantly higher than those in the control group. The levels of p62, phosphorylated-p62 (p-p62) and HO-1 in the STZ group were significantly higher than those in the control group, and the levels of p-p62, HO-1, and 8-OHdG were significantly lower by ABE administration. The STZ-induced early diabetes increases the levels of proteins related to peroxisomal FA β-oxidation and oxidative stress markers in hearts. ABE protects diabetic hearts from oxidative damage.

Sevoflurane postconditioning is not mediated by ferritin accumulation and cannot be rescued by simvastatin in isolated streptozotocin-induced diabetic rat hearts.

Sevoflurane postconditioning (sevo postC) is an attractive and amenable approach that can protect the myocardium against ischemia/reperfusion (I/R)-injury. Unlike ischemic preconditioning (IPC), sevo postC does not require additional induced ischemic periods to a heart that is already at risk. IPC was previously shown to generate myocardial protection against I/R-injury through regulation of iron homeostasis and de novo ferritin synthesis, a process found to be impaired in the diabetic state. The current study investigated whether alterations in iron homeostasis and ferritin mRNA and protein accumulation are also involved in the cardioprotective effects generated by sevo postC. It was also investigated whether the protective effects of sevo postC in the diabetic state can be salvaged by simvastatin, through inducing nitric oxide (NO) bioavailability/activity, in isolated streptozotocin (STZ)-induced diabetic hearts (DH). Isolated rat hearts from healthy Controls and diabetic animals were retrogradely perfused using the Langendorff configuration and subjected to prolonged ischemia and reperfusion, with and without (2.4 and 3.6%) sevo postC and/or pre-treatment with simvastatin (0.5 mg/kg). Sevo postC significantly reduced infarct size and improved myocardial function in healthy Controls but not in isolated DH. The sevo postC mediated myocardial protection against I/R-injury was not associated with de novo ferrtin synthesis. Furthermore, simvastatin aggravated myocardial injury after sevo postC in STZ-induced DHs, likely due to increasing NO levels. Despite the known mechanistic overlaps between PC and postC stimuli, distinct differences underlie the cardioprotective interventions against myocardial I/R-injury and are impaired in the DH. Sevo postC mediated cardioprotection, unlike IPC, does not involve de novo ferritin accumulation and cannot be rescued by simvastatin in STZ-induced DHs.

High Glucose-Induced Cardiomyocyte Death May Be Linked to Unbalanced Branched-Chain Amino Acids and Energy Metabolism.

High glucose-induced cardiomyocyte death is a common symptom in advanced-stage diabetic patients, while its metabolic mechanism is still poorly understood. The aim of this study was to explore metabolic changes in high glucose-induced cardiomyocytes and the heart of streptozotocin-induced diabetic rats by 1H-NMR-based metabolomics. We found that high glucose can promote cardiomyocyte death both in vitro and in vivo studies. Metabolomic results show that several metabolites exhibited inconsistent variations in vitro and in vivo. However, we also identified a series of common metabolic changes, including increases in branched-chain amino acids (BCAAs: leucine, isoleucine and valine) as well as decreases in aspartate and creatine under high glucose condition. Moreover, a reduced energy metabolism could also be a common metabolic characteristic, as indicated by decreases in ATP in vitro as well as AMP, fumarate and succinate in vivo. Therefore, this study reveals that a decrease in energy metabolism and an increase in BCAAs metabolism could be implicated in high glucose-induced cardiomyocyte death.

Cardiac apoptosis induced under high glucose condition involves activation of IGF2R signaling in H9c2 cardiomyoblasts and streptozotocin-induced diabetic rat hearts

The insulin-like growth factor type 2 receptor (IGF2R) overexpression has been implicated in heart disease progression. Unregulated IGF2R signaling triggers cardiac hypertrophy, apoptosis, and cardiomyopathies. The present study investigated the role of IGF2R in cardiomyocyte apoptosis under high glucose (HG) levels and in streptozotocin (STZ) induced diabetic rat hearts. We found that IGF2 and IGF2R protein expression were highly upregulated under high glucose condition in H9c2 cells as well as in STZ induced diabetic rat hearts. Using immunoblotting and TUNEL assay, we found that elevated glucose condition induced IGF2R expression leads to activation of Gαq mediated calcineurin-dependent signaling pathway, which further leads to downstream activation and expression of cardiac hypertrophy related proteins, ANP and BNP. Further, we found that glucose-induced IGF2R expression downregulated survival protein p-Akt, p-Bad (Ser 155) and enhanced the expression of apoptosis-inducing proteins cytochrome c and cleaved Caspase-3. Our results suggested that hyperglycemic condition leads to cellular cardiomyocyte apoptosis both in vitro and in vivo models, via abnormally increased activation of the IGF2R signaling pathway.

Effects of a standardized extract of Rheum turkestanicum Janischew root on diabetic changes in the kidney, liver and heart of streptozotocin-induced diabetic rats

Numerus studies highlighted benefits of natural flavonoids in the management of diabetes. The present study was aimed to investigate the effects of a high flavonoids containing extract of Rheum turkestanicum on diabetic changes in different tissues. Male Wistar rats were divided into normal and streptozotocin-induced diabetic groups received saline or hydroalcoholic extract of R. turkestanicum root (100, 200 and 300mg/kg) through orogastric gavage for 4 weeks. Serum glucose, HbA1c, lipids, creatinine, uric acid, liver enzymes (alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase), and cardiac enzymes (lactate dehydrogenase and creatine phosphokinase) in diabetic control group were significantly higher compared to normal control group (p<0.001). The extract significantly reduced these factors, increased body weight, and improved both glucosurea and proteinuria. Lipid peroxidation was high in the liver of diabetic rats compared to normal rats (p<0.001) and reverted toward control values by R. turkestanicum. Also, the extract significantly protected the liver, kidney, and heart of diabetic rats against histopathological changes. In conclusion, R. turkestanicum inhibited the development of nephropathy, liver injury, and myocardial damage in diabetes by lowering the serum levels of glucose and lipids, and by inhibiting oxidative stress mediated lipid peroxidation.

The effects of zofenopril on cardiac function and pro-oxidative parameters in the streptozotocin-induced diabetic rat heart.

Diabetes mellitus is a chronic condition that continues to increase in both incidence and prevalence. Renin-Angiotensin-Aldosterone System is one of the main modulators of chronic hyperglycaemia and, thus, its influence on tissues. Hyperglycaemia-induced oxidative stress is an important factor in diabetic cardiomyopathy. The present study was carried out on 24 adult male Wistar albino rats (8-week-old and with body masses of 190±10g). We evaluated the influence of acute administration of zofenopril on ex vivo myocardial function from rats with streptozotocin-induced diabetes mellitus, with a special emphasis on cardiodynamic and oxidative stress parameters in diabetic rat hearts. Rats were divided randomly into two groups (12 animals per group): control non-diabetic animals (C) were healthy rats perfused with 1.5µM of zofenopril, and STZ-treated diabetic animals (DM) were diabetic animals perfused with 1.5µM of zofenopril 4weeks after the induction of diabetes. Our results demonstrated that diabetic rats are characterized by a depressed cardiac performance and that oxidative markers are related to alterations in cardiac function in rats with 4weeks of STZ-induced diabetes. Additionally, the use of zofenopril as a monotherapy slightly diminished cardiac damage induced by chronic hyperglycaemia. However, long-term follow-up intervention trials are necessary to fully demonstrate the benefit of zofenopril in this context. A challenge for future investigations will be to identify the effects of chronic administration or combination therapy with angiotensin-converting enzyme inhibitors in various models of diabetes.

Abstract PR467

Background & Objectives: Isoflurane postconditioning (IsoPostC) against myocardial ischemia reperfusion injury (IRI) is significantly decreased in diabetes. The underlying mechanism is unclear. Signal transducer and activator of transcription 3 (STAT3) is critical in ischemic postconditioning cardioprotection which is reduced in diabetic hearts as well as decreased expressions of cardiac Brahma-related gene 1 (Brg1) and nuclear factor-erythroid 2-related factor 2 (Nrf2). We hypothesized that Brg1/Nrf2 and STAT3 activation may play a critical role in IsoPostC-mediated cardioprotection in normal and diabetic hearts. Materials & Methods: Non-diabetic (C) and 8-week streptozotocin-induced type-1 diabetic (D) rat hearts were perfused ex vivo using Langendorff-perfused model. Rat hearts were subjected to 30 minutes global ischemia and 120 minutes of reperfusion with or without IsoPostC. IsoPostC was achieved by administrating emulsified isoflurane(2.0%, v/v) at the onset of reperfusion for 10 min. Left ventricular (LV) function was assessed throughout the experiment. Myocardial infarct size (IS) in relation to the area at risk (AAR) was used to measure the extent of myocardial injury. Cell injury was assessed by quantification of lactate dehydrogenase (LDH). Cardiac Nrf2, STAT3 and Brg1 protein expressions were measured using western blot. Results: (1)IsoPostC reduced myocardial IS in normal but not diabetic rats. (2) IsoPostC attenuated myocardial dysfunction in normal but not diabetic rats. (3) Brg1, Nrf2 and STAT3 protein expressions were enhanced in normal but decreased in diabetic rats. (4) The beneficial effects of IsoPostC were abolished by Brg1, Nrf2 or STAT3 gene knockdown.Conclusion: Our results indicate that IsoPostC confers cardioprotection through Brg1/Nrf2/STAT3 signaling, and impairment of this pathway may be responsible for the loss of sensitivity to IsoPostC cardioprotectio in type 1 diabetes.

The Loss of Myocardial Benefit following Ischemic Preconditioning Is Associated with Dysregulation of Iron Homeostasis in Diet-Induced Diabetes.

Whether the diabetic heart benefits from ischemic preconditioning (IPC), similar to the non-diabetic heart, is a subject of controversy. We recently proposed new roles for iron and ferritin in IPC-protection in Type 1-like streptozotocin-induced diabetic rat heart. Here, we investigated iron homeostasis in Cohen diabetic sensitive rat (CDs) that develop hyperglycemia when fed on a high-sucrose/low-copper diet (HSD), but maintain normoglycemia on regular-diet (RD). Control Cohen-resistant rats (CDr) maintain normoglycemia on either diet. The IPC procedure improved the post-ischemic recovery of normoglycemic hearts (CDr-RD, CDr-HSD and CDs-RD). CDs-HSD hearts failed to show IPC-associated protection. The recovery of these CDs-HSD hearts following I/R (without prior IPC) was better than their RD controls. During IPC ferritin levels increased in normoglycemic hearts, and its level was maintained nearly constant during the subsequent prolonged ischemia, but decayed to its baseline level during the reperfusion phase. In CDs-HSD hearts the baseline levels of ferritin and ferritin-saturation with iron were notably higher than in the controls, and remained unchanged during the entire experiment. This unique and abnormal pattern of post-ischemic recovery of CDs-HSD hearts is associated with marked changes in myocardial iron homeostasis, and suggests that iron and iron-proteins play a causative role/s in the etiology of diabetes-associated cardiovascular disorders.

Effects of pomegranate seed oil on oxidative stress markers, serum biochemical parameters and pathological findings in kidney and heart of streptozotocin-induced diabetic rats

Purpose: Oxidative stress due to hyperglycemia is a major cause of diabetes complications. The aim of this study was to evaluate the effects of pomegranate seed oil (PSO) on serum biochemical parameters, cardiomyopathy and nephropathy induced by diabetes mellitus.Method: W/A adult rats were divided into four groups (12 each): group 1, received saline (1 mL/kg), group 2, received streptozotocin (STZ, 65 mg/kg, a single dose as i.p.), groups 3 and 4, received STZ + PSO (0.4 and 0.8 mL/kg, daily by gavage, respectively). After three weeks, six rats of each group and one week later the remaining animals were anesthetized, blood samples were taken for measuring serum biochemical parameters. Sections of heart and kidneys were used for histopathological studies and the remaining tissues were homogenized for measuring malondialdehyde (MDA) and total sulfhydryl groups.Results: Significant elevation of serum creatinine and urea, LDL, triglyceride, glucose levels as well as urine markers, MDA levels in tissue homogenates and a significant decrease in total thiol content and serum HDL were observed in STZ-treated group as compared with control group. PSO treatment resulted in a significant decrease in tissue MDA content, serum creatinine and urea levels as well as urine markers as compared with STZ-treated group. Lipid profile was ameliorated with PSO treatment. PSO also significantly reversed STZ-induced depletion in thiol content and histological abnormality. Effect of PSO was more specific at 28th than 21th days of study.Conclusion: The results showed that PSO has a protective effect against diabetes complications in rats.

Role of ZIP7 in Regulation of Cytosolic Free Zn2+ Level in Mammalian Cardiomyocytes

Zinc (as Zn2+), increasingly recognized as an important trace element, has physiological role in mammalian cell function. Resting intracellular free Zn2+ level ([Zn2+]i) can be greatly increased by thiol-reactive oxidants or high glucose that contributes to oxidant-induced alterations in EC-coupling of cardiomyocytes. Since Zn2+ is important in cellular physiology, very little is known how [Zn2+]i is controlled and stored intracellularly in cardiomyocytes. Therefore, in the present study we aimed to investigate the role of ZIP7 on regulation of [Zn2+]i in cardiomycoytes. We first used newly-developed genetically-encoded FRET-based sensors to monitor cytosolic (CYS), mitochondrial (MitC) and endoplasmic reticulum (ER) [Zn2+]. Our data showed that [Zn2+] levels in these compartments were about 0.5, 5.0 and 0.2 nM, respectively in isolated left ventricular cardiomyocytes. Since expression but not location of ZIP7 has been shown in the heart tissue, inhere, we tested whether Zn2+ transport from ER into cytosol by a transporter ZIP7 thereby responsible for cytosolic/S(E)R Zn2+ homeostasis in cardiomyocytes under pathological condition. Our data have shown that both protein level and expression of ZIP7 increased in either cardiomyocytes isolated from streptozotocin-induced diabetic rat heart or high glucose (25mM; 24-hours) incubated H9c2 cells. Our immunofluorescence analysis also demonstrated that ZIP7 is localised in ER but not in Golgi apparatus in these cells. Furthermore, ZIP7 knocked-down in cardiomycoytes induced a significant reduction of cytosolic [Zn2+]. All experimental data showed that ER is a Zn2+ pool and ZIP7 has a crucial role in regulation of cytosolic Zn2+ in mammalian cardiomyocytes (Supported by TUBITAK SBAG-113S466, COST Action TD1304, EFSD Fellowships).

Association Between β3-Adrenoceptor Activation and Intracellular Free Zinc Ion Increase Contributes to Hyperglycemia-Induced Cardiac ER-Stress

The Zn2+ release during cardiac cycle results mostly intracellular free Zn2+ ([Zn2+]i) increases via triggering production of reactive oxygen/nitrogen species (ROS/RNS). However, it is not clearly known whether there are relationships between increased ROS/RNS production and [Zn2+]i changes under hyperglycemic conditions in cardiomyocytes. Thus, herein, we monitored [Zn2+]i changes and ROS/RNS production by using specific fluorescence dyes, such as FluoZin-3, DAF and DCDFA, respectively, in hyperglycemic cardiomyocytes from streptozotocin-induced diabetic rat heart by using confocal imaging. We have shown that acute increases in either ROS or RNS could induce marked increases in [Zn2+]i of freshly isolated cardiomyocytes, which could be reversed by a thiol reducing agent DTT. The basal ROS/RNS-induced [Zn2+]i levels were found to be significantly higher in hyperglycemic cardiomyocytes compared to the controls. Our Western blot analysis showed that hyperglycemia induced marked phosphorylation in some members of macromolecular protein complex of cardiac ryanodine receptors such as PKA, CaMKII and PP2A, which were also hyperphosphorylated with high [Zn2+]. Furthermore, other important factors, which have important role in glucose metabolism and are activated with cytosolic [Zn2+], such as a transcription factor NF-κB and GSK-3 and Akt in cardiomyocytes were phophosylated markedly with high glucose incubation. Overall, the present data demonstrated that there are cross-relationships between increased production of ROS/RNS and increased [Zn2+]i level in hyperglycemic cardiomyocytes, which is mediated with several protein phosphatases and kinases and underlies, in part, diabetes-induced cardiac dysfunction. (Supported by grant of TUBITAK (SBAG-113S466 & SBAG-214S254).