Left ventricular dysfunction and remodeling in streptozotocin-induced diabetic rats

The current state of preclinical modeling of human diabetic cardiomyopathy using rodents

The prevalence of diabetic cardiomyopathy (DCM), a specific cardiovascular complication of diabetes mellitus, has recently increased. Its pathogenesis is not fully understood, and no consensus regarding therapeutic options has been reached. Experimental studies on rodents are expected to yield further data at the preclinical stage. The present paper describes and quantitatively compares the experimental protocols intended to mimic human DCM. Experimental articles (conducted between 1990 and 2022) were identified from online electronic databases according to the PRISMA Protocol. The Cochrane Q-test was used to estimate study heterogeneity; the quality of each individual study was assessed using SYRCLE's risk of bias tool for animal studies. Sensitivity analysis was performed according to the leave-one-out method. Publication bias across studies was assessed using Egger's weighted regression and Duval and Tweedie 'trim and fill' method. A wide spectrum of protocols - from 651 papers, was examined (type 1 or 2 diabetes mellitus, as well as obesity models). They were found to vary in their presentation of DCM according to a variety of hemodynamic, echocardiographic, histopathologic and metabolic parameters. Particular attention was paid to comorbid conditions, and cardiac performance featured as systolic, diastolic dysfunction, or refractory heart failure. The majority of models displayed diastolic dysfunction, as well as myocardial fibrosis and left ventricle hypertrophy, which mimics early stage DCM. Unlike in humans, animal DCM rarely progressed to the symptomatic heart failure with reduced ejection fraction (HFrEF). The ability of individual procedures to reflect refractory heart failure or biventricular dysfunction - in the end-stage DCM has remained unclear.

2-Arachidonoylglycerol Attenuates Myocardial Fibrosis in Diabetic Mice Via the TGF-β1/Smad Pathway

PURPOSE

Diabetic cardiomyopathy (DM) is the cause of late cardiac dysfunction in diabetic patients. Myocardial fibrosis is the main pathological mechanism, and it is associated with transforming growth factor-β1(TGF-β1) expression up-regulation. 2-Arachidonoylglycerol (2-AG) is an endogenous cannabinoid that can effectively improve myocardial cell energy metabolism and cardiac function. Here, we evaluated the protective effect of 2-AG on diabetic cardiomyopathy.

METHODS

Male C57BL/6 mice were injected with 2-AG intraperitoneally for 4 weeks (10 micro g/kg/day) after 12 weeks of diabetic modeling. After 4 weeks, heart function was evaluated by echocardiography. Heart structure was assessed by hematoxylin and eosin staining. Cardiac fibrosis was analyzed using immunohistochemistry, Sirius red stain, and western blot.

RESULTS

After modeling in diabetic mice, cardiac ultrasonography showed decreased cardiac function and pathological findings showed myocardial fibrosis. 2-AG could effectively inhibit the up-regulation of TGF-β1 and Smad2/3, reduce myocardial fibrosis, and ultimately improve cardiac function in diabetic mice.

CONCLUSION

2-AG reduces cardiac fibrosis via the TGF-β1/Smad2/3 pathway and is a potential pathway for the treatment of cardiac dysfunction in diabetic mice.

Melatonin ameliorates serobiochemical alterations and restores the cardio-nephro diabetic vascular and cellular alterations in streptozotocin-induced diabetic rats

Melatonin possesses a wide range of pharmacological activities, including antidiabetic properties. Diabetes mellitus (DM) induces several physiopathological changes in body organs, which could be observed lately after systemic failure. In the current study, we aimed to investigate the serobiochemical changes and the histopathological picture in the diabetic heart and the kidney early before chronic complications and highlight the association between hyperglycemia, glomerular alterations, and cardiovascular changes. In addition, the role of melatonin in the treatment of cardio-nephro diabetic vascular and cellular adverse changes in streptozotocin-induced diabetic rats was also studied. A total of 40 mature Wistar albino rats were distributed into five groups; (1) control untreated rats, (2) diabetic mellitus untreated (DM) rats, in which DM was induced by the injection of streptozotocin (STZ), (3) control melatonin-treated (MLT), (4) melatonin-treated diabetic (DM + MLT) rats, in which melatonin was injected (10 mg/kg/day, i.p.) for 4 weeks, and (5) insulin-treated diabetic (DM + INS) rats. The serum biochemical analysis of diabetic STZ rats showed a significant (P < 0.05) increase in the concentrations of blood glucose, total oxidative capacity (TOC), CK-MB, endothelin-1, myoglobin, H-FABP, ALT, AST, urea, and creatinine as compared to control rats. In contrast, there was a significant (P < 0.05) decrease in serum concentration of insulin, total antioxidative capacity (TAC), total nitric oxide (TNO), and total protein level in DM rats vs. the control rats. Significant improvement in the serobiochemical parameters was noticed in both (DM + MLT) and (DM + INS) groups as compared with (DM) rats. The histological examination of the DM group revealed a disorder of myofibers, cardiomyocyte nuclei, and an increase in connective tissue deposits in between cardiac tissues. Severe congestion and dilation of blood capillaries between cardiac muscle fibers were also observed. The nephropathic changes in DM rats revealed various deteriorations in glomeruli and renal tubular cells of the same group. In addition, vascular alterations in the arcuate artery at the corticomedullary junction and interstitial congestion take place. Melatonin administration repaired all these histopathological alterations to near-control levels. The study concluded that melatonin could be an effective therapeutic molecule for restoring serobiochemical and tissue histopathological alterations during diabetes mellitus.

Pregestational diabetes alters cardiac structure and function of neonatal rats through developmental plasticity

Pregestational diabetes (PGDM) leads to developmental impairment, especially cardiac dysfunction, in their offspring. The hyperglycemic microenvironment inside the uterus alters the cardiac plasticity characterized by electrical and structural remodeling of the heart. The altered expression of several transcription factors due to hyperglycemia during fetal development might be responsible for molecular defects and phenotypic changes in the heart. The molecular mechanism of the developmental defects in the heart due to PGDM remains unclear. To understand the molecular defects in the 2-days old neonatal rats, streptozotocin-induced diabetic female rats were bred with healthy male rats. We collected 2-day-old hearts from the neonates and identified the molecular basis for phenotypic changes. Neonates from diabetic mothers showed altered electrocardiography and echocardiography parameters. Transcriptomic profiling of the RNA-seq data revealed that several altered genes were associated with heart development, myocardial fibrosis, cardiac conduction, and cell proliferation. Histopathology data showed the presence of focal cardiac fibrosis and increased cell proliferation in neonates from diabetic mothers. Thus, our results provide a comprehensive map of the cellular events and molecular pathways perturbed in the neonatal heart during PGDM. All of the molecular and structural changes lead to developmental plasticity in neonatal rat hearts and develop cardiac anomalies in their early life.

Sodium–glucose cotransporter-2 inhibitor alleviated atrial remodeling in STZ-induced diabetic rats by targeting TLR4 pathway

Purpose

The mechanism of sodium–glucose cotransporter-2 inhibitor (SGLT-2i) reducing the incidence of atrial fibrillation remains unclear. We hypothesize that sodium–glucose cotransporter-2 inhibitor alleviated atrial remodeling in STZ-induced diabetic rats by targeting TLR4 pathway.

Methods

A total of 42 rats were randomly assigned into three groups: control group (CON group); diabetes group (DM group): diabetes mellitus rats were established by 65 mg/kg streptozotocin (STZ) intraperitoneal injection; and diabetes + dapagliflozin group (DM + DAPA group): diabetic rats were given DAPA gavage administration (DAPA 2mg/kg/d for 4 weeks by gavage administration), 14 rats in each group. Epicardial multiple-lead recording and intracardiac electrophysiology studies were performed to investigate the electrical remodeling in the heart and the atrial fibrillation inducibility in each group. Western blot analysis and real-time PCR were used to determine the protein and mRNA expression of toll-like receptor 4 (TLR4), interleukin receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), nuclear factor-kappa B (NF-κB), and type I collagen (collagen I).

Results

Compared with rats in CON group, rats in DM group showed marked myocardial fibrosis, ectopic pacing excitement, reduced conduction velocity, decreased cardiac function. TLR4/IRAK1/TRAF6/NF-κB, collagen I proteins expressions and incidence of atrial fibrillation (27.3%) were increased in DM group. Parts of these changes were reversed by treatment of DAPA. Incidence of atrial fibrillation was decreased in DM + DAPA group (2.8%).

Conclusions

SGLT-2i dapagliflozin may prevent diabetic rats' atrial remodeling and reduce the inducibility of atrial fibrillation partly by targeting TLR4/IRAK1/TRAF6/NF-κB inflammatory pathway.

Renoprotective Effect of Liraglutide Is Mediated via the Inhibition of TGF-Beta 1 in an LLC-PK1 Cell Model of Diabetic Nephropathy

Background: Recently published research demonstrated direct renoprotective effects of the glucagon-like peptide-1 receptor agonist GLP 1 RA, but the relevant molecular mechanisms are still not clear. The aim of this research was to assess the effects of Liraglutide in a cell culture model of diabetic nephropathy on cell viability, antioxidant (GSH) and transforming growth factor beta 1 (TGF- β1) levels and extracellular matrix (ECM) expression. The metabolic activity in hyperglycemic conditions and the effect of Liraglutide treatment were assessed by measuring Akt, pAkt, GSK3β, pGSK3β, pSTAT3, SOCS3, iNOS and NOX4 protein expression with Western blot. F actin distribution was used to assess the structural changes of the cells upon treatment. Materials and methods: The cells were exposed to high glucose (HG30 mM) followed by 0.5 mM H2O2 and a combination of glucose and H2O2 during 24 h. Subsequently, the cells were treated with different combinations of HG30, H2O2 and Liraglutide. Cell viability was determined by an MTT colorimetric test, and the GSH, TGF-β1 concentration and ECM expression were measured using a spectrophotometric/microplate reader assay and an ELISA kit, respectively. Western blotting was used to detect the protein level of Akt, pAkt, GSK3β, pGSK3β, pSTAT3, SOCS3, iNOS and NOX4. The F-actin cytoskeleton was visualized with Phalloidin stain and subsequently quantified. Results: Cell viability was decreased as well as GSH levels in cells treated with a combination of HG30/H2O2, and HG30 alone (p < 0.001). The addition of Liraglutide improved the viability in cells treated with HG30, but it did not affect the cell viability in the cell treated with the addition of H2O2. GSH increased with the addition of Liraglutide in HG30/H2O2 (p < 0.001) treated cells, with no effect in cells treated only with HG30. TGF-β1 levels (p < 0.001) were significantly increased in HG30 and HG30/H2O2. The addition of Liraglutide significantly decreased the TGF-β1 levels (p < 0.01; p < 0.05) in all treated cells. The synthesis of collagen was significantly increased in HG30/H2O2 (p < 0.001), while the addition of Liraglutide in HG30/H2O2 significantly decreased collagen (p < 0.001). Akt signaling was not significantly affected by treatment. The GSK3b and NOX4 levels were significantly reduced (p < 0.01) after the peroxide and glucose treatment, with the observable restoration upon the addition of Liraglutide suggesting an important role of Liraglutide in oxidative status regulation and mitochondrial activity. The treatment with Liraglutide significantly upregulated STAT3 (p < 0.01) activity, with no change in SOCS3 indicating a selective regulation of the STAT 3 signaling pathway in glucose and the oxidative overloaded environment. A significant reduction in the distribution of F-actin was observed in cells treated with HG30/H2O2 (p < 0.01). The addition of Liraglutide to HG30-treated cells led to a significant decrease of distribution of F-actin (p < 0.001). Conclusion: The protective effect of Liraglutide is mediated through the inhibition of TGF beta, but this effect is dependent on the extent of cellular damage and the type of toxic environment. Based on the WB analysis we have revealed the signaling pathways involved in cytoprotective and cytotoxic effects of the drug itself, and further molecular studies in vitro and vivo are required to elucidate the complexity of the pathophysiological mechanisms of Liraglutide under conditions of hyperglycemia and oxidative stress.

The effect of combination of functional and nonfunctional acrylic polymers on transdermal patches of : in vitro permeation, in vivo evaluation using biochemical parameters, and stability studies

Background

A double-layer transdermal drug-in-adhesive patch of carvedilol was developed using functional and nonfunctional grades of acrylic adhesives, DURO-TAK® 387-2051, DURO-TAK® 387-2510, and DURO-TAK® 87-4098. The patch was designed to provide adequate permeation of the drug up to 2 days, with effective adhesion attributes. An optimized formulation was selected, the effect of the combination was studied and a 180° peel strength test was performed to evaluate adhesive properties. Further, the patch was assessed for in vivo studies on basis of biochemical parameters, skin irritation, and stability studies. The stability study was carried out on optimized fresh (S1) and 6 months old patches stored at room, and accelerated condition (40 ± 2 °C/75 ± 5% RH) using FTIR, DSC, and SEM techniques.

Result

It was studied that the steady-state flux (Jss) or permeation rate of the drug through excised rat skin has relied on the nature of acrylic and the combination of acrylic polymers. The TDDS containing –OH functional group DT 387-2510 with nonfunctional pressure-sensitive adhesives (PSAs) DT 87-4098, with Span 80 as penetration enhancer exhibited maximum flux (19.12 ± 0.64 μg/cm2/h) and form homogeneous and stable blends, controlling permeation of drug at a desired steady rate for 48 h. The data obtained from in vivo studies using biochemical parameters suggested that there were no statistical differences observed in results for the control and treated group while analyzing observations for serum creatinine, glucose test, sodium test, albumin, and potassium (p > 0.05). Also, the optimized formulation showed no sign of localized reactions and was confirmed by a skin histological study indicating the formulation was safe and compatible with the skin. A significant shift of peaks was not observed in FTIR spectra and DSC thermograms of the patches after the stability period.

Conclusion

The investigation reveals that the drug-in-adhesive patch of carvedilol, by a combination of functional and nonfunctional PSAs, provides a good and effective option for controlled delivery of carvedilol. From our findings, it has been concluded that drug in the adhesive patch has been able to provide satisfactory adhesion, drug uniformity, drug permeation, marked positive biochemical results, and good stability.

Kolaviron attenuates cardiovascular injury in fructose-streptozotocin induced type-2 diabetic male rats by reducing oxidative stress, inflammation, and improving cardiovascular risk markers

The prevalence of cardiovascular disease among type-2 diabetic patients has become a source of major concern world over. This study explored the protective effect of kolaviron, a bioflavonoid, against oxidative cardiovascular injury in fructose- streptozotocin-induced type 2 diabetic male Sprague Dawley rats. After acclimatization, induction, and confirmation of type-2 diabetes, kolaviron was administered for 28days, after which the animals were anesthetized with Isofor and euthanized. Blood from each rat were collected, and blood samples were then centrifuged for serum and plasma. Cardiac troponin I (cTnI), creatine kinase myocardial band (CK-MB), Creatine phosphokinase (CK), and insulin levels were immediately determined in serum, while remaining samples (serum, plasma, and organs) were stored in the bio-freezer at - 80 °C and 10% formalin for enzyme-link immunosorbent assay (ELISA), biochemical, molecular, and histopathological studies. The results show that type-2 diabetes induction with fructose and streptozotocin led to increased blood glucose levels, decreased insulin levels and cardiac antioxidant enzyme activities, increased malondialdehyde levels, cardiac biomarkers and pro-inflammatory cytokines levels, resulted in abnormal lipid profile, increased blood pressure and angiotensin-converting enzyme (ACE) activity, and decreased plasma endothelial nitric oxide synthase (eNOS) concentration. The histopathological examination of the cardiac tissue revealed severe lesion, hypertrophy, and myofibrils degeneration. However, administration of kolaviron for 28days remarkably improved these conditions. Hence the result from the study validates the potency of kolaviron, and suggests it could serve as an alternative to existing remedy in ameliorating or protecting against cardiovascular injury in type-2 diabetes.

STZ-diabetic rat heart maintains developed tension amplitude by increasing sarcomere length and crossbridge density

New Findings

What is the central question of this study?

In the papillary muscle from type I diabetic rats, does diabetes‐associated altered ventricular function result from changes of acto‐myosin interactions and are these modifications attributable to a possible sarcomere rearrangement?

What is the main finding and its importance?

For the first time, we showed that type‐I diabetes altered sarcomeric ultrastructure, as seen by transmission electron microscopy, consistent with physiological parameters. The diabetic condition induced slower timing parameters, which is compatible with a diastolic dysfunction. At the sarcomeric level, augmented β‐myosin heavy chain content and increased sarcomere length and crossbridges' number preserve myocardial stroke and could concur to maintain the ejection fraction.

Abstract

We investigated whether diabetes‐associated altered ventricular function, in a type I diabetes animal model, results from a modification of acto‐myosin interactions, through the in vitro recording of left papillary muscle mechanical parameters and examination of sarcomere morphology by transmission electron microscopy (TEM). Experiments were performed on streptozotocin‐induced diabetic and age‐matched control female Wistar rats. Mechanical isometric and isotonic indexes and timing parameters were determined. Using Huxley's equations, we calculated mechanics, kinetics and energetics of myosin crossbridges. Sarcomere length and A‐band length were measured on TEM images. Type I and III collagen and β‐myosin heavy chain (MHC) expression were determined by immunoblotting. No variation in resting and developed tension or maximum extent of shortening was evident between groups, but diabetic rats showed lower maximum shortening velocity and prolonged timing parameters. Compared to controls, diabetics also displayed a higher number of crossbridges with lower unitary force. Moreover, no change in type I and III collagen was associated to diabetes, but pathological rats showed a two‐fold enhancement of β‐MHC content and longer sarcomeres and A‐band, detected by ultrastructural morphometry. Overall, these data address whether a preserved systolic function accompanied by an altered diastolic phase results from a recruitment of super‐relaxed myosin heads or the phosphorylation of the regulatory light chain site in myosin. Although the early signs of diabetic cardiomyopathy were well expressed, the striking finding of our study was that, in diabetics, sarcomere modification may be a possible compensatory mechanism that preserves systolic function.

Retinoid X receptor agonists attenuates cardiomyopathy in streptozotocin-induced type 1 diabetes through LKB1-dependent anti-fibrosis effects

Diabetic cardiac fibrosis increases ventricular stiffness and facilitates the occurrence of diastolic dysfunction. Retinoid X receptor (RXR) plays an important role in cardiac development and has been implicated in cardiovascular diseases. In the present study, we investigated the effects of RXR agonist treatment on streptozotocin (STZ)-induced diabetic cardiomyopathy (DCM) and the underlying mechanism. Sprague-Dawley (SD) rats induced by STZ injection were treated with either RXR agonist bexarotene (Bex) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Cardiac fibroblasts (CFs) were treated with high glucose (HG) with or without the indicated concentration of Bex or the RXR ligand 9-cis-retinoic acid (9-cis-RA). The protein abundance levels were measured along with collagen, body weight (BW), blood biochemical indexes and transforming growth factor-β (TGF-β) levels. The effects of RXRα down-regulation by RXRα small interfering RNA (siRNA) were examined. The results showed that bexarotene treatment resulted in amelioration of left ventricular dysfunction by inhibiting cardiomyocyte apoptosis and myocardial fibrosis. Immunoblot with heart tissue homogenates from diabetic rats revealed that bexarotene activated liver kinase B1 (LKB1) signaling and inhibited p70 ribosomal protein S6 kinase (p70S6K). The increased collagen levels in the heart tissues of DCM rats were reduced by bexarotene treatment. Treatment of CFs with HG resulted in significantly reduced LKB1 activity and increased p70S6K activity. RXRα mediated the antagonism of 9-cis-RA on HG-induced LKB1/p70S6K activation changes in vitro. Our findings suggest that RXR agonist ameliorates STZ-induced DCM by inhibiting myocardial fibrosis via modulation of the LKB1/p70S6K signaling pathway. RXR agonists may serve as novel therapeutic agents for the treatment of DCM.

Hesperidin ameliorates signs of the metabolic syndrome and cardiac dysfunction via IRS/Akt/GLUT4 signaling pathway in a rat model of diet-induced metabolic syndrome

BACKGROUND

Hesperidin has been reported to have biological activities such as antihypertensive, hypoglycemic, and antioxidant effects. This study investigated whether hesperidin could improve signs of the metabolic syndrome and cardiac function in a high-fat diet (HFD) induced metabolic syndrome (MS) in rats.

METHODS

Male Sprague-Dawley rats were fed HFD and 15% fructose for 16 weeks and treated with hesperidin (15 or 30 mg/kg, based on signs of MS from a preliminary study) or metformin, a positive control agent, (100 mg/kg) for the final four weeks. Cardiac function, blood pressure, fasting blood glucose, oral glucose tolerance, serum insulin, and lipid profiles were measured. Histomorphometrics of left ventricles, epidydimal fat pads and liver were evaluated. Expressions of phosphorylate insulin receptor substrate1(p-IRS1), p-Akt and GLUT4 in cardiac tissue were determined.

RESULTS

Hesperidin and metformin attenuated MS in HFD rats (p < 0.05). The accumulation of visceral fat pads and fatty liver associated with increases in liver lipid contents and liver enzymes were found in MS rats that were alleviated in hesperidin or metformin-treated groups (p < 0.05). Hesperidin and metformin improved cardiac dysfunction and hypertrophy observed in MS rats (p < 0.05). Restoration of the insulin signaling pathway, IRS/Akt/GLUT4 protein expression, was demonstrated in hesperidin and metformin-treated groups (p < 0.05). Hesperidin (30 mg/kg) was more effective than the lower dose.

CONCLUSION

Hesperidin was effective in reducing signs of MS and alterations of LV hypertrophy and function. These beneficial effects on the heart were associated with the restoration of the cardiac insulin signaling pathway in MS rats.

Diabetes induces differences in the F-actin spatial organization of striated muscles

Studies have shown the cytoskeleton disorganization produced by diabetes and quantified F-actin fluorescence in the striated muscles of diabetic animals. However, at present, there are no studies that have quantified F-actin spatial organization (F-actin-SO). Through our research, we analyzed the effect of diabetes on F-actin-SO in the cardiac and skeletal muscles of a mouse model. The muscle samples were labeled with phalloidin-rhodamine and analyzed with confocal microscopy. The analysis was done in two dimensions using four approaches: quantitation of (a) phalloidin-occupied areas; (b) number of F-actin-unoccupied areas per muscular fiber; (c) F-actin filament discontinuity; and (d) costamere periodicity. Our results showed that both the cardiac and skeletal muscles of the control mice had more phalloidin-occupied areas than the diabetic mice. The skeletal muscles had a significantly higher number of F-actin-unoccupied areas per muscular fiber and more F-actin discontinuities. Additionally, using western blot analyses, we showed that those differences were not due to α-actin protein expression. Finally, we considered the importance of these findings in dysfunctional contraction, disassembly in cell-cell communication, conduction of muscle impulse, and changes in cell nanomechanics. Our results quantitatively demonstrated that diabetes severely affects F-actin-SO in striated muscles.

The Potential Role of Undercarboxylated Osteocalcin Upregulation in Microvascular Insufficiency in a Rat Model of Diabetic Cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is accompanied by microvascular complications that lead to myocardial dysfunction and heart failure. Most conventional therapies cannot ameliorate the microvascular insufficiency in DCM. In this study, we tested the hypothesis that undercarboxylated osteocalcin (ucOC) may be a new adjuvant therapy against the progression of DCM and its underlying microvascular pathology.

MATERIALS AND METHODS

Diabetes was induced in Wistar rats with a high-fat diet combined with streptozotocin injections, and ucOC was upregulated after warfarin administration in the treated group. After 8 weeks, cardiac functions were assessed using a Langendorff apparatus. Cardiac tissue samples were also extracted to assess the ucOC receptor and vascular endothelial growth factor (VEGF) for histopathological studies.

RESULTS

Both the systolic and the diastolic dysfunction observed in the DCM group were significantly improved after the increase in ucOC blood levels. Significant improvement in VEGF and CD31 expression after warfarin injection was associated with increased capillary density, neovascularization, and decreased myocardial fibrosis together with the reestablishment of myocardial structural and ultrastructural patterns.

CONCLUSION

Undercarboxylated osteocalcin may have a promising effect in improving microvascular insufficiency and myocardial dysfunction in DCM.

Carvacrol Attenuates Diabetic Cardiomyopathy by Modulating the PI3K/AKT/GLUT4 Pathway in Diabetic Mice

Background: Diabetic cardiomyopathy (DCM), a common complication of diabetes mellitus, eventually leads to heart failure. Carvacrol is a food additive with diverse bioactivities. We aimed to study the protective effects and mechanisms of carvacrol in DCM.

Methods: We used a streptozotocin-induced and db/db mouse model of types 1 and 2 diabetes mellitus (T1DM and T2DM), respectively. Both study groups received daily intraperitoneal injections of carvacrol for 6 weeks. Cardiac remodeling was evaluated by histological analysis. We determined gene expression of cardiac remodeling markers (Nppa and Myh7) by quantitative real-time PCR and cardiac function by echocardiography. Changes of PI3K/AKT signaling were determined with Western blotting. GLUT4 translocation was evaluated by Western blotting and immunofluorescence staining.

Results: Compared with control mice, both T1DM and T2DM mice showed cardiac remodeling and left ventricular dysfunction. Carvacrol significantly reduced blood glucose levels and suppressed cardiac remodeling in mice with T1DM and T2DM. At the end of the treatment period, both T1DM and T2DM mice showed lesser cardiac hypertrophy, Nppa and Myh7 mRNA expressions, and cardiac fibrosis, compared to mice administered only the vehicle. Moreover, carvacrol significantly restored PI3K/AKT signaling, which was impaired in mice with T1DM and T2DM. Carvacrol increased levels of phosphorylated PI3K, PDK1, AKT, and AS160 and inhibited PTEN phosphorylation in mice with T1DM and T2DM. Carvacrol treatment promoted GLUT4 membrane translocation in mice with T1DM and T2DM. Metformin was used as the positive drug control in T2DM mice, and carvacrol showed comparable effects to that of metformin on cardiac remodeling and modulation of signaling pathways.

Conclusion: Carvacrol protected against DCM in mice with T1DM and T2DM by restoring PI3K/AKT signaling-mediated GLUT4 membrane translocation and is a potential treatment of DCM.

The Effects of Folic Acid Administration on Cardiac Oxidative Stress and Cardiovascular Biomarkers in Diabetic Rats

The aim of this study was to examine the effects of folic acid administration on the antioxidant enzyme (superoxide dismutase (SOD) and catalase (CAT)) activities, lactate and malate dehydrogenase (LDH and MDH) activities, and certain LDH and MDH isoform distribution in the cardiac tissue of diabetic Wistar male rats. Diabetes mellitus (DM) was induced by streptozotocin (STZ). There were five groups: C1-control (physiological saline 1 ml/kg, i.p. one day), C2-control with daily physiological saline treatment (1 ml/kg, i.p. 28 days), DM-diabetes mellitus (STZ 100 mg/kg in physiological saline, i.p. one day), FA-folic acid (5 mg/kg in physiological saline, i.p. 28 days), and DM+FA-diabetes mellitus and folic acid group (STZ 100 mg/kg in physiological saline, i.p. one day, and folic acid 5 mg/kg in physiological saline, i.p. 28 days). After four weeks, animal hearts were isolated for measurement of enzyme activities, as well as for histomorphometry analyses. An elevated glucose level and a decreased insulin level were obtained in the DM group. SOD, CAT, and MDH activities were elevated in the DM group, while there was no difference in LDH activity among the groups. In all tested groups, four LDH and three MDH isoforms were detected in the heart tissue, but with differences in their relative activities among the groups. Left ventricular cardiomyocyte transversal diameters were significantly smaller in both diabetic groups. Folic acid treatment of diabetic rats induced a reduced glucose level and reduced CAT, SOD, and MDH activities and alleviated the decrease in cardiomyocyte diameters. In conclusion, increased activities of antioxidant enzymes and MDH may be the consequence of oxidative stress caused by DM. Administration of the folic acid has a protective effect since it leads to reduction in glycemia and activities of the certain examined enzymes in the rats with experimentally induced DM.

Activation of nuclear β-catenin/c-Myc axis promotes oxidative stress injury in streptozotocin-induced diabetic cardiomyopathy

Myocardial oxidative stress injury plays a crucial role in the pathogenesis of diabetic cardiomyopathy (DCM). Wnt/β-catenin signaling has been reported to involve in various heart diseases. However, the underlying mechanism associated with β-catenin in DCM remains elusive. This study intended to explore the effect of β-catenin on oxidative damage of DCM by establishing streptozotocin (STZ)-induced diabetic mouse model and hydrogen peroxide (H₂O₂)-treated myocardial cell model. Cardiac oxidative stress in DCM was detected by measurements of lipid peroxidation and anti-oxidative enzyme activities as well as DHE staining. Nuclear β-catenin activity and oxidative damage degree were measured by western blotting, qPCR, MTT assay and TUNEL staining. Cardiac function and morphology were evaluated by echocardiography and histopathology. Under diabetic oxidative stress or H₂O₂ stimulation, nuclear β-catenin accumulation upregulated downstream c-Myc and further facilitated DNA damage and p53-mediated apoptosis as well as cell viability reduction, followed by phenotypic changes of cardiac dysfunction, interstitial fibrosis deposition and myocardial atrophy. Conversely, through directly inhibiting nuclear β-catenin/c-Myc axis, not only did siRNA knockdown of β-catenin or c-Myc attenuate cell injury in H₂O₂-stimulated cardiomyocytes, but also diabetic cardiac-specific β-catenin-knockout mice displayed the same prevention of heart injury as insulin-treated diabetic mice. The present study demonstrated that activated nuclear β-catenin/c-Myc axis was responsible for oxidative cardiac impairment of DCM. Therefore, repressing functional nuclear β-catenin may provide a hopeful therapeutic strategy for DCM.

Insulin replacement limits progression of diabetic cardiomyopathy in the low-dose streptozotocin-induced diabetic rat

Diabetic cardiomyopathy is a major contributor to the increasing burden of heart failure globally. Effective therapies remain elusive, in part due to the incomplete understanding of the mechanisms underlying diabetes-induced myocardial injury. The objective of this study was to assess the direct impact of insulin replacement on left ventricle structure and function in a rat model of diabetes. Male Sprague-Dawley rats were administered streptozotocin (55 mg/kg i.v.) or citrate vehicle and were followed for 8 weeks. A subset of diabetic rats were allocated to insulin replacement (6 IU/day insulin s.c.) for the final 4 weeks of the 8-week time period. Diabetes induced the characteristic systemic complications of diabetes (hyperglycaemia, polyuria, kidney hypertrophy) and was accompanied by marked left ventricle remodelling (cardiomyocyte hypertrophy, left ventricle collagen content) and diastolic dysfunction (transmitral E/A, left ventricle-dP/dt). Importantly, these systemic and cardiac impairments were ameliorated markedly following insulin replacement, and moreover, markers of the diabetic cardiomyopathy phenotype were significantly correlated with the extent of hyperglycaemia. In summary, these data suggest that poor glucose control directly contributes towards the underlying features of experimental diabetic cardiomyopathy, at least in the early stages, and that adequate replacement ameliorates this.

Metabolic and Biochemical Stressors in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) or diabetes-induced cardiac dysfunction is a direct consequence of uncontrolled metabolic syndrome and is widespread in US population and worldwide. Despite of the heterogeneous and distinct features of DCM, the clinical relevance of DCM is now becoming established. DCM progresses to pathological cardiac remodeling with the higher risk of heart attack and subsequent heart failure in diabetic patients. In this review, we emphasize lipid substrate quality and the phenotypic, metabolic, and biochemical stressors of DCM in the rodent and human pathophysiology. We discuss lipoxygenase signaling in the inflammatory pathway with multiple contributing and confounding factors leading to DCM. Additionally, emerging biochemical pathways are emphasized to make progress toward therapeutic advancement to treat DCM.

Novel therapeutic effects of sesamin on diabetes-induced cardiac dysfunction

Diabetes is a risk factor that increases the occurrence and severity of cardiovascular events. Cardiovascular complications are the leading cause of mortality of 75% of patients with diabetes >40 years old. Sesamin, the bioactive compound extracted from Sesamum indicum, is a natural compound that has diverse beneficial effects on hypoglycemia and reducing cholesterol. The aim of this study is to investigate sesamin effects to diabetes-inducing cardiac hypertrophy. In the present study bioinformatics analysis demonstrated cardiac hypertrophy signaling may be the most important pathway for upregulating genes in sesamin-treated groups. To verify the bioinformatics prediction, sesamin was used as the main bioactive compound to attenuate the impact of diabetes induced by streptozotocin (STZ) on cardiac function in a rat model. The results revealed that oral administration of sesamin for 4 weeks (100 and 200 mg/kg body weight) marginally improved blood glucose levels, body weight and significantly ameliorated the effects on heart rate and blood pressure in rats with type 1 diabetes relative to control rats. The QT interval of sesamin was also reduced relative to the control group. The findings indicated that sesamin has potential cardioprotective effects in the STZ-induced diabetes model. This suggested that this can be used as a novel treatment for patients with diabetes with cardiac dysfunction complication.

The Antioxidant Potential of Azadirachta indica Ameliorates Cardioprotection Following Diabetic Mellitus-Induced Microangiopathy

BACKGROUND

Cardiac complications associated with diabetes mellitus have become major cause of concern. Antidiabetic drugs, with varied mode of action, are although available, apprehensions exist for their limited action or side effects upon prolonged use. Efforts are therefore inclined toward finding other alternatives. The present study was, thus, undertaken to evaluate the cardioprotective effect of Azadirachta indica (AI) on microangiopathic changes in rat model of diabetes.

MATERIALS AND METHODS

Diabetes was induced in male rats by single intraperitoneal injection of streptozotocin (60 mg/kg body weight). Seven days after glucose levels are stabilized, aqueous leaf extract of AI (ALE) (600 mg/kg(1) body weight) was administered orally to diabetic animals every day for 7 days.

RESULTS

High blood glucose characterizing diabetes in these animals was found to show increased lipid peroxidation (LPO), altered antioxidant biomarkers together with microangiopathic alterations. The treatment of diabetic rats with ALE reduced the levels of blood glucose, LPO, and restored the activities of antioxidant enzyme. Light and transmission electron microscopic analysis revealed reduced necrotic areas and inflammation in tissue architecture of ALE treated heart in comparison to untreated diabetic group.

CONCLUSION

AI provides cardioprotection by ameliorating oxidative stress in rat model of diabetic mellitus.

SUMMARY

The streptozotocin (STZ) treatment (60 mg/kg body weight) to animals induced diabetic changes such as elevated blood glucose levels, decreased body weight, altered lipid profiles together with development of proxidant state evidenced by elevated levels of lipid peroxidation (LPO), depletion in reduced glutathione (GSH) levels and altered antioxidant enzymes with consequent microangiopathic alterations in heart tissue evinced by localization of necrotic and inflamed areas in heart tissueThe treatment of animals with Azadirachta indica leaf extract (ALE) (600 mg/kg body weight) post-STZ treatment significantly reversed the adverse effects witnessed by normalized blood glucose levels, improvement in reduced body weight and stabilized lipid profilesFurther, ALE treatment also significantly reduced the LPO indices, improvement in GSH content and restoration of antioxidant enzyme activities, suggesting antioxidatant potential of ALEThe microangiopathic changes in the heart tissue consequent to induction of diabetes and oxidative stress by STZ as reiterated through light microscopy and transmission electron microscopy were found to be reversed by ALE treatment. These observations pointed toward cardiopreventive effects of ALE following microangiopathic changes as seen following induction of diabetes mellitus. Abbreviations used: AI: Azadirachta indica, ALE: Azadirachta indica Leaves Extract. STZ: Streptozotocin, LPO Lipid per oxidation, GSH: Glutathione, GSSG: Glutathione disulphide, SOD: Superoxide dismutase, GP: Glutathione peroxidase, GR: Glutathione reductase.

Genistein ameliorates cardiac inflammation and oxidative stress in streptozotocin-induced diabetic cardiomyopathy in rats

The present study was undertaken to evaluate the protective effects of genistein against cardiac inflammation and oxidative stress in streptozotocin (STZ) (45 mg/kg body weight)-induced diabetic rats. genistein (300 mg/kg/day) was administered orally for 24 weeks to STZ-induced diabetic rats. The effects of genistein on blood glucose, % glycosylated hemoglobin (HbA1c), C-reactive protein, tumor necrosis factor (TNF- α), transforming growth factor (TGF-β1), and total antioxidant were studied. Ultrastructural and histopathological assessment of injury were also undertaken using transmission electron microscope. STZ-induced diabetes resulted in significant increase in the levels of blood glucose, HbA1c, C-reactive protein, TNF- α and TGF-β1, and a decline in total antioxidant reserve of the myocardium. Administration of genistein to diabetic rats resulted in a decrease in blood glucose (p < 0.001), % HbA1c (p < 0.0001), C-reactive protein (p < 0.001), and expression of TNF- α (p < 0.001) and TGF-β1 (p < 0.0001) proteins. In addition, genistein treatment results in augmentation of total antioxidant (p < 0.01) reserve of the hearts. The above findings were supported by histological as well as immunohistochemical localization of NF-κB (p65) in the heart. Genistein treatment ameliorated the ultrastructural degenerative changes in the cardiac tissues as compared to the diabetic control. The result demonstrates that genistein restored the integrity of the diabetic myocardium by virtue of its anti-inflammatory and antioxidant effects.

Updating experimental models of diabetic cardiomyopathy

Diabetic cardiomyopathy entails a serious cardiac dysfunction induced by alterations in structure and contractility of the myocardium. This pathology is initiated by changes in energy substrates and occurs in the absence of atherothrombosis, hypertension, or other cardiomyopathies. Inflammation, hypertrophy, fibrosis, steatosis, and apoptosis in the myocardium have been studied in numerous diabetic experimental models in animals, mostly rodents. Type I and type II diabetes were induced by genetic manipulation, pancreatic toxins, and fat and sweet diets, and animals recapitulate the main features of human diabetes and related cardiomyopathy. In this review we update and discuss the main experimental models of diabetic cardiomyopathy, analysing the associated metabolic, structural, and functional abnormalities, and including current tools for detection of these responses. Also, novel experimental models based on genetic modifications of specific related genes have been discussed. The study of specific pathways or factors responsible for cardiac failures may be useful to design new pharmacological strategies for diabetic patients.

Morphological restructuring of myocardium during the early phase of experimental diabetes mellitus

The purpose of this study was to determine the specific features of the morphological restructuring of the myocardium in the early stage of experimental diabetes mellitus (DM). Experimental type 1 DM rat model was developed by intraperitoneal injection of alloxan solution at a dose of 30 mg per 100 g body mass. After 1 month, 3 mL of blood was drawn by heart puncture and the plasma separated by centrifugation for biochemical analysis. Plasma glucose, insulin, and glycosylated haemoglobin in whole blood were determined. Light microscopy and morphometric studies were conducted of histological slices of the hearts of experimental animals. The investigation of heart morphology showed a statistically significant alteration in chamber wall thickness in the right auricle in rats with alloxan-induced DM. A change in cardiomyocyte diameter in myocardium slices was observed in all chambers of DM rats except for the left ventricle. Average cardiomyocyte diameter in rats with experimental DM increased by 26.6% and 15.5% in the right auricle and right ventricle, respectively, while average cardiomyocyte diameter in the left auricle decreased by 20.8%. Histological investigation of the heart following alloxan injection demonstrated, under the epicardium, distended vessels of the venous collecting microcirculatory system. Aggregation and agglutination of red blood cells and endothelial cell destruction were found in some vessels. In the early stage of DM development, structural alterations in the microcirculatory channels and myocardiocytes can be observed in the heart. These structural alterations were most evident in the right chambers of the heart.

Diabetes increases stiffness of live cardiomyocytes measured by atomic force microscopy nanoindentation

Stiffness of live cardiomyocytes isolated from control and diabetic mice was measured using the atomic force microscopy nanoindentation method. Type 1 diabetes was induced in mice by streptozotocin administration. Histological images of myocardium from mice that were diabetic for 3 mo showed disorderly lineup of myocardial cells, irregularly sized cell nuclei, and fragmented and disordered myocardial fibers with interstitial collagen accumulation. Phalloidin-stained cardiomyocytes isolated from diabetic mice showed altered (i.e., more irregular and diffuse) actin filament organization compared with cardiomyocytes from control mice. Sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2a) pump expression was reduced in homogenates obtained from the left ventricle of diabetic animals compared with age-matched controls. The apparent elastic modulus (AEM) for live control or diabetic isolated cardiomyocytes was measured using the atomic force microscopy nanoindentation method in Tyrode buffer solution containing 1.8 mM Ca(2+) and 5.4 mM KCl (physiological condition), 100 nM Ca(2+) and 5.4 mM KCl (low extracellular Ca(2+) condition), or 1.8 mM Ca(2+) and 140 mM KCl (contraction condition). In the physiological condition, the mean AEM was 112% higher for live diabetic than control isolated cardiomyocytes (91 ± 14 vs. 43 ± 7 kPa). The AEM was also significantly higher in diabetic than control cardiomyocytes in the low extracellular Ca(2+) and contraction conditions. These findings suggest that the material properties of live cardiomyocytes were affected by diabetes, resulting in stiffer cells, which very likely contribute to high diastolic LV stiffness, which has been observed in vivo in some diabetes mellitus patients.

Morphology and Contractility of Cardiac Myocytes in Early Stages of Streptozotocin-Induced Diabetes Mellitus in Rats

Diabetic cardiomyopathy is the leading cause of mortality in type 1 diabetes. Thus study of cardiomyocyte morphology and function during early stages of diabetes using modern analytical methods is of critical importance. Therefore, using confocal microscopy, we determined metric parameters, volumes and contractility, with calcium transients in isolated left-ventricular myocytes at one week after induction of diabetes in rats. Myocyte volume analysis from 3D confocal scans was performed using an automated contour detection algorithm that took the actual shape of the myocytes into account. We showed a significant reduction in myocyte volume in diabetic animals. We also showed a significant reduction in length and width but not in thickness of the myocytes, which suggests disproportional reorganization of the structure of the heart tissue during short-term diabetes. From a functional point of view, we observed a significant decrease in cell shortening at a stimulation frequency of 0.5 Hz. This was accompanied by a decrease in calcium transient amplitude. Together, these data suggest that impaired calcium handling is one of the factors that contributes to the observed decrease in myocyte shortening during early stages of streptozotocin-induced diabetes in rats.

Effect of Piper sarmentosum Extract on the Cardiovascular System of Diabetic Sprague-Dawley Rats: Electron Microscopic Study

Although Piper sarmentosum (PS) is known to possess the antidiabetic properties, its efficacy towards diabetic cardiovascular tissues is still obscured. The present study aimed to observe the electron microscopic changes on the cardiac tissue and proximal aorta of experimental rats treated with PS extract. Thirty-two male Sprague-Dawley rats were divided into four groups: untreated control group (C), PS-treated control group (CTx), untreated diabetic group (D), and PS-treated diabetic group (DTx). Intramuscular injection of streptozotocin (STZ, 50 mg/kg body weight) was given to induce diabetes. Following 28 days of diabetes induction, PS extract (0.125 g/kg body weight) was administered orally for 28 days. Body weight, fasting blood glucose, and urine glucose levels were measured at 4-week interval. At the end of the study, cardiac tissues and the aorta were viewed under transmission electron microscope (TEM). DTx group showed increase in body weight and decrease in fasting blood glucose and urine glucose level compared to the D group. Under TEM study, DTx group showed lesser ultrastructural degenerative changes in the cardiac tissues and the proximal aorta compared to the D group. The results indicate that PS restores ultrastructural integrity in the diabetic cardiovascular tissues.

S100B: role in cardiac remodeling and function following myocardial infarction in diabetes

AIM

S100B plays a role in cardiac remodeling following myocardial infarction (MI) and in diabetic vascular complications but not examined in diabetic myocardium. We thus examined the effects of targeted deletion of S100B gene on post-MI hearts.

MAIN METHODS

Coronary artery ligation or sham was performed 15 weeks after streptozotocin (STZ) or vehicle injection in wild-type (WT) and S100B knock-out (BKO) mice. Left ventricular (LV) structural and functional remodeling was studied 35 days after induction of MI.

KEY FINDINGS

In diabetes, post-MI remodeling exhibited an attenuated increase in LV mass, dilation, and myocyte hypertrophy in association with increased apoptosis and fibrosis and reduced matrix metalloproteinase-2 (MMP-2) activity. Despite reduced LV dilation, impairment of cardiac function was similar to non-diabetic controls. Both diabetes and MI alone induced myocardial S100B and its canonical receptor for advanced glycation end product (RAGE) expression. By contrast, in post-MI diabetic myocardium, S100B expression was attenuated. Diabetic BKO, following MI demonstrated increased ventricular dilation compared to WT, in association with greater impairment of cardiac function, GLUT4 expression and systemic AGE levels.

SIGNIFICANCE

These data suggest that S100B expression may serve to modulate cardiac metabolism and adverse consequences of AGE in diabetic post-MI remodeling and function.

Glycoxidative stress and cardiovascular complications in experimentally-induced diabetes: effects of antioxidant treatment

Diabetes mellitus (DM) is a common metabolic disease, representing a serious risk factor for the development of cardiovascular complications, such as coronary heart disease, peripheral arterial disease and hypertension. Oxidative stress (OS), a feature of DM, is defined as an increase in the steady-state levels of reactive oxygen species (ROS) and may occur as a result of increased free radical generation and/or decreased anti-oxidant defense mechanisms. Increasing evidence indicates that hyperglycemia is the initiating cause of the tissue damage in DM, either through repeated acute changes in cellular glucose metabolism, or through long-term accumulation of glycated biomolecules and advanced glycation end products (AGEs). AGEs are formed by the Maillard process, a non-enzymatic reaction between ketone group of the glucose molecule or aldehydes and the amino groups of proteins that contributes to the aging of proteins and to the pathological complications of DM. In the presence of uncontrolled hyperglycemia, the increased formation of AGEs and lipid peroxidation products exacerbate intracellular OS and results in a loss of molecular integrity, disruption in cellular signaling and homeostasis, followed by inflammation and tissue injury such as endothelium dysfunction, arterial stiffening and microvascular complications. In addition to increased AGE production, there is also evidence of multiple pathways elevating ROS generation in DM, including; enhanced glucose auto-oxidation, increased mitochondrial superoxide production, protein kinase C-dependent activation of NADPH oxidase, uncoupled endothelial nitric oxide synthase (eNOS) activity, increased substrate flux through the polyol pathway and stimulation of eicosanoid metabolism. It is, therefore, not surprising that the correction of these variables can result in amelioration of diabetic cardiovascular abnormalities. A linking element between these phenomena is cellular redox imbalance due to glycoxidative stress (GOS). Thus, recent interest has focused on strategies to prevent, reverse or retard GOS in order to modify the natural history of diabetic cardiovascular abnormalities. This review will discuss the links between GOS and diabetes-induced cardiovascular disorders and the effect of antioxidant therapy on altering the development of cardiovascular complications in diabetic animal models.

Evaluation of contractile function and inotropic reserve with tissue velocity, strain and strain rate imaging in streptozotocin-induced diabetes

AIMS

The aim of the present study was to evaluate left ventricular (LV) function and contractile reserve (CR) with Doppler myocardial imaging (DMI) in a small animal model for type 1 diabetes.

METHODS AND RESULTS

Cardiac function was assessed in anaesthetized Wistar rats 6 and 8 weeks after injection of 60 mg/kg of streptozotocin. At 6 weeks of diabetes, colour DMI echocardiography was performed at rest and during incremental dosages of dobutamine (5, 10, 20 microg/kg/min). Left ventricular fractional shortening was decreased after 8 weeks of follow-up [36 +/- 5 (D) vs. 41 +/- 4% (C); P = 0.049]. After 6 weeks of diabetes, DMI measurements were reduced in the diabetic rats in the inferolateral wall at rest [systolic velocity: 2.5 +/- 0.4 (D) vs. 4.4 +/- 0.3 (C) cm/s; P < 0.001; systolic strain rate: 12.2 +/- 3.4 (D) vs. 17.4 +/- 3.2 (C) 1/s; P = 0.012] and during inotropic stimulation [delta velocity (cm/s): 0.2 +/- 0.1 (D) vs. 0.5 +/- 0.3 (C)/5 microg dobutamine; P = 0.002; delta strain rate (1/s): 1.4 +/- 0.9 (D) vs. 3.3 +/- 2.2 (C)/5 microg dobutamine; P = 0.049]. Furthermore, the intraventricular delay in time-to-peak systolic strain was larger in diabetes [20 +/- 18 (D) vs. 10 +/- 7 (C) ms; P= 0.01]. Systolic mitral annular velocity was also lower in the diabetic rats at rest [2.7 +/- 0.4 (D) vs. 3.5 +/- 0.4 (C) cm/s; P < 0.001] and in response to dobutamine [delta velocity (cm/s): 0.1 +/- 0.1 (D) vs. 0.3 +/- 0.2 (C)/5 microg dobutamine; P = 0.013].

CONCLUSION

In experimental diabetes, a reduction in radial and longitudinal LV function and CR can be detected with DMI before the onset of a reduced global LV function.

Wideband high-frequency echocardiography to evaluate myocardial infarct size

OBJECTIVE

This study was designed to validate the feasibility of wideband high-frequency ultrasound imaging to resolve in vivo the degree, location, and morphologic changes of myocardial infarction (MI) in a rat model.

METHODS

The left anterior descending coronary artery was ligated in the test group (n = 41), and the sham control group did not have ligation (n = 7). The rats were examined with 10- to 22-MHz echocardiography to evaluate the MI size, location, and geometric formation.

RESULTS

The endocardial chamber shape was deformed, with enlargement of the anteroposterior dimension and fractional shortening, and was comparable with the degree of MI both in short- and long-axis sections of the left ventricle. Histologic analysis showed remodeling to different extents corresponding to different MI sizes (small, medium, and large).

CONCLUSIONS

The results suggest that this technique can be used in vivo to evaluate the MI location, size, and morphologic changes corresponding to the extent of the injury.

Regulation of VASP phosphorylation in cardiac myocytes: differential regulation by cyclic nucleotides and modulation of protein expression in diabetic and hypertrophic heart

Vasodilator-stimulated phosphoprotein (VASP) is a major substrate for cyclic nucleotide-dependent kinases that has been implicated in cardiac pathology, yet many aspects of VASP's molecular regulation in cardiomyocytes are incompletely understood. In these studies, we explored the role of VASP, both in signaling pathways in isolated murine myocytes, as well as in a model of cardiac hypertrophy in VASP(null) mice. We found that the beta-adrenergic agonist isoproterenol promotes the rapid and reversible phosphorylation of VASP at Ser157 and Ser239. Forskolin and the cAMP analog 8-(4-chlorophenylthio)-cAMP promote a similar pattern of VASP phosphorylation at both sites. The effects of isoproterenol are blocked by atenolol and by compound H-89, an inhibitor of the cAMP-dependent protein kinase. By contrast, phosphorylation of VASP only at Ser239 is seen following activation of particulate guanylate cyclase by atrial natriuretic peptide, or following activation of soluble guanylate cyclase by sodium nitroprusside, or following treatment of myocytes with cGMP analog. We found that basal and isoproterenol-induced VASP phosphorylation is entirely unchanged in cardiomyocytes isolated from either endothelial or neuronal nitric oxide synthase knockout mice. In cardiomyocytes isolated from diabetic mice, only basal VASP phosphorylation is increased, whereas, in cells isolated from mice subjected to ascending aortic constriction (AAC), we found a significant increase in basal VASP expression, along with an increase in VASP phosphorylation, compared with cardiac myocytes isolated from sham-operated mice. Moreover, there is further increase in VASP phosphorylation in cells isolated from hypertrophic hearts following isoproterenol treatment. Finally, we found that VASP(null) mice subjected to transverse aortic constriction develop cardiac hypertrophy with a pattern similar to VASP(+/+) mice. Our findings establish differential receptor-modulated regulation of VASP phosphorylation in cardiomyocytes by cyclic nucleotides. Furthermore, these studies demonstrate for the first time that VASP expression is upregulated in hypertrophied heart.

Impairment of insulin-stimulated Akt/GLUT4 signaling is associated with cardiac contractile dysfunction and aggravates I/R injury in STZ-diabetic rats

In this study, we established systemic in-vivo evidence from molecular to organism level to explain how diabetes can aggravate myocardial ischemia-reperfusion (I/R) injury and revealed the role of insulin signaling (with specific focus on Akt/GLUT4 signaling molecules). The myocardial I/R injury was induced by the left main coronary artery occlusion for 1 hr and then 3 hr reperfusion in control, streptozotocin (STZ)-induced insulinopenic diabetes, and insulin-treated diabetic rats. The diabetic rats showed a significant decrease in heart rate, and a prolonged isovolumic relaxation (tau) which lead to decrease in cardiac output (CO) without changing total peripheral resistance (TPR). The phosphorylated Akt and glucose transporter 4 (GLUT 4) protein levels were dramatically reduced in both I/R and non-I/R diabetic rat hearts. Insulin treatment in diabetes showed improvement of contractile function as well as partially increased Akt phosphorylation and GLUT 4 protein levels. In the animals subjected to I/R, the mortality rates were 25%, 65%, and 33% in the control, diabetic, and insulin-treated diabetic group respectively. The I/R-induced arrhythmias and myocardial infarction did not differ significantly between the control and the diabetic groups. Consistent with its anti-hyperglycemic effects, insulin significantly reduced I/R-induced arrhythmias but had no effect on I/R-induced infarctions. Diabetic rat with I/R exhibited the worse hemodynamic outcome, which included systolic and diastolic dysfunctions. Insulin treatment only partially improved diastolic functions and elevated P-Akt and GLUT 4 protein levels. Our results indicate that cardiac contractile dysfunction caused by a defect in insulin-stimulated Akt/GLUT4 may be a major reason for the high mortality rate in I/R injured diabetic rats.

Diabetic cardiomyopathy

Diabetic cardiomyopathy is a distinct primary disease process, independent of coronary artery disease, which leads to heart failure in diabetic patients. Epidemiological and clinical trial data have confirmed the greater incidence and prevalence of heart failure in diabetes. Novel echocardiographic and MR (magnetic resonance) techniques have enabled a more accurate means of phenotyping diabetic cardiomyopathy. Experimental models of diabetes have provided a range of novel molecular targets for this condition, but none have been substantiated in humans. Similarly, although ultrastructural pathology of the microvessels and cardiomyocytes is well described in animal models, studies in humans are small and limited to light microscopy. With regard to treatment, recent data with thiazoledinediones has generated much controversy in terms of the cardiac safety of both these and other drugs currently in use and under development. Clinical trials are urgently required to establish the efficacy of currently available agents for heart failure, as well as novel therapies in patients specifically with diabetic cardiomyopathy.

Interaction of diet and diabetes on cardiovascular function in rats

Genetic rodent models of type 2 diabetes are routinely utilized in studies of diabetes-related cardiovascular disease; however, these models frequently exhibit abnormalities that are not consistent with diabetic complications. The aim of this study was to develop a model of type 2 diabetes that exhibits evidence of cardiovascular dysfunction commonly seen in patients with diabetes with minimal nondiabetes-related pathologies. Young male rats received either control (Con), high-fat (HF; 60%), or Western (Wes; 40% fat, 45% carbohydrate) diets for 2 wk after which streptozotocin (2 x 35 mg/kg ip 24 h apart) was administered to induce diabetes (Dia). Blood glucose levels were higher in Con + Dia and Wes + Dia groups compared with the HF + Dia group (25 +/- 1, 25 +/- 2, and 15 +/- 1 mmol/l, respectively; P < 0.05) group. Liver, kidney, and pancreatic dysfunction and cardiomyocyte lipid accumulation were found in all diabetic animals. Despite lower heart rates in Con + Dia and HF + Dia groups, arterial and left ventricular pressures were not different between any of the experimental groups. All three diabetic groups had diastolic dysfunction, but only HF + Dia and Wes + Dia groups exhibited elevated diastolic wall stress, arterial stiffness (augmentation index), and systolic dysfunction (velocity of circumferential shortening, systolic wall stress). Surprisingly, we found that left ventricular dysfunction and arterial stiffness were more pronounced in the HF + Dia than the Con + Dia group and was similar to the Wes + Dia group despite significantly lower levels of hyperglycemia compared with either group. In conclusion, the HF + Dia group exhibited a stable, modest level of hyperglycemia, which was associated with cardiac dysfunction comparable with that seen in moderate to advanced stages of human type 2 diabetes.

Effect of streptozotocin-induced diabetes on myocardial blood flow reserve assessed by myocardial contrast echocardiography in rats

The role of structural and functional abnormalities of small vessels in diabetes cardiomyopathy remains unclear. Myocardial contrast echocardiography allows the quantification of myocardial blood flow at rest and during dipyridamole infusion. The aim of the study was to determine the myocardial blood flow reserve in normal rats compared with streptozotocin-induced diabetic rats using contrast echocardiography.

METHODS

We prospectively studied 40 Wistar rats. Diabetes was induced by intravenous streptozotocin in 20 rats. All rats underwent baseline and stress (dipyridamole: 20 mg/kg) high power intermittent imaging in short axis view under anaesthesia baseline and after six months. Myocardial blood flow was determined and compared at rest and after dipyridamole in both populations. The myocardial blood flow reserve was calculated and compared in the 2 groups. Parameters of left ventricular function were determined from the M-mode tracings and histological examination was performed in all rats at the end of the study.

RESULTS

At six months, myocardial blood flow reserve was significantly lower in diabetic rats compared to controls (3.09 +/- 0.98 vs. 1.28 +/- 0.67 ml min-1 g-1; p < 0.05). There were also a significant decrease in left ventricular function and a decreased capillary surface area and diameter at histology in the diabetic group.

CONCLUSION

In this animal study, diabetes induced a functional alteration of the coronary microcirculation, as demonstrated by contrast echocardiography, a decrease in capillary density and of the cardiac systolic function. These findings may offer new insights into the underlying mechanisms of diabetes cardiomyopathy.

Altered calcium homeostasis does not explain the contractile deficit of diabetic cardiomyopathy

OBJECTIVE

This study examines the extent to which the contractile deficit of diabetic cardiomyopathy is due to altered Ca(2+) homeostasis.

RESEARCH DESIGN AND METHODS

Measurements of isometric force and intracellular calcium ([Ca(2+)](i), using fura-2/AM) were made in left ventricular (LV) trabeculae from rats with streptozotocin-induced diabetes and age-matched siblings.

RESULTS

At 1.5 mmol/l [Ca(2+)](o), 37 degrees C, and 5-Hz stimulation frequency, peak stress was depressed in diabetic rats (10 +/- 1 vs. 17 +/- 2 mN/mm(2) in controls; P < 0.05) with a slower time to peak stress (77 +/- 3 vs. 67 +/- 2 ms; P < 0.01) and time to 90% relaxation (76 +/- 7 vs. 56 +/- 3 ms; P < 0.05). No difference was found between groups for either resting or peak Ca(2+), but the Ca(2+) transient was slower in time to peak (39 +/- 2 vs. 34 +/- 1 ms) and decay (time constant, 61 +/- 3 vs. 49 +/- 3 ms). Diabetic rats had a longer LV action potential (APD(50), 98 +/- 5 vs. 62 +/- 5 ms; P < 0.0001). Western blotting showed that diabetic rats had a reduced expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2a, with no difference in expression of the Na(+)/Ca(2+) exchanger. Immunohistochemistry of LV free wall showed that type I collagen was increased in diabetic rats (diabetic 7.1 +/- 0.1%, control 12.7 +/- 0.1%; P < 0.01), and F-actin content reduced (diabetic 56.9 +/- 0.6%; control 61.7 +/- 0.4%; P < 0.0001) with a disrupted structure.

CONCLUSIONS

We find no evidence to support the idea that altered Ca(2+) homeostasis underlies the contractile deficit of diabetic cardiomyopathy. The slower action potential and reduced SERCA2a expression can explain the slower Ca(2+) transient kinetics in diabetic rats but not the contractile deficit. Instead, we suggest that the observed LV remodeling may play a crucial role.

Clinical toxicology of citalopram after acute intoxication with the sole drug or in combination with other drugs: overview of 26 cases

There is discussion concerning the cardiac safety of citalopram in an overdose. The aim of this study was to investigate the toxic effects and toxicokinetic parameters of citalopram in an overdose as a single drug and in combination with other drugs. Cases observed between 1997 and 2006 were evaluated. Patient demographics, ingested doses, serum concentrations of citalopram, coingested drugs, and clinical parameters were acquired. Outcomes were observed symptoms of the gastrointestinal tract, respiratory tract, central nervous system, and cardiovascular system. Poisoning Severity Score was used to evaluate severity of every intoxicated patient. Individual toxicokinetic parameter values were calculated. Twenty-nine cases of citalopram overdose were observed; three cases had incomplete data so that 26 cases were evaluable. The ingested amount ranged from 200 to 4960 mg. Blood concentrations ranged from 0.21 to 7.5 mg/L with 20 minutes to 8 hours between suggested time of ingestion and blood sampling. Most frequently reported symptoms were drowsiness (seven cases), tachycardia (15 cases), QTc prolongation (eight cases), decrease of consciousness (eight cases), and seizures (four cases). Median length of hospital stay was 3 days (range, 1-8 days). Of the 26 evaluated cases, two fatalities occurred, one because of a cardiac arrest and one as a result of a respiratory arrest. According to Poisoning Severity Score, severity of intoxication was minor in three patients (11%), moderate in nine patients (35%), and severe in 14 patients (54%). Severity was mainly caused by neurologic and respiratory effects. Elimination half-life was prolonged but did not correlate with the amount of ingestion. Citalopram intoxications seem to proceed more severely than is known for other selective serotonin reuptake inhibitor intoxications, causing drowsiness, coma, and seizures in overdose. Cardiac toxicity is generally mild. Therefore, we recommend seizure precautions and intensive care unit admission with cardiac monitoring for citalopram-intoxicated patients. Because elimination half-life is prolonged, normal pharmacokinetics do not apply.

Diacylglycerol kinase zeta inhibits myocardial atrophy and restores cardiac dysfunction in streptozotocin-induced diabetes mellitus

Background

Activation of the diacylglycerol (DAG)-protein kinase C (PKC) pathway has been implicated in the pathogenesis of a number of diabetic complications. Diacylglycerol kinase (DGK) converts DAG to phosphatidic acid and acts as an endogenous regulator of PKC activity. Akt/PKB is associated with a downstream insulin signaling, and PKCβ attenuates insulin-stimulated Akt phosphorylation.

Methods and Results

We examined transgenic mice with cardiac-specific overexpression of DGKζ (DGKζ-TG) compared to wild type (WT) mice in streptozotocin-induced (STZ, 150 mg/kg) diabetic and nondiabetic conditions. After 8 weeks, decreases in heart weight and heart weight/body weight ratio in diabetic WT mice were inhibited in DGKζ-TG mice. Echocardiography at 8 weeks after STZ-injection demonstrated that decreases in left ventricular end-diastolic diameter and fractional shortening observed in WT mice were attenuated in DGKζ-TG mice. Thinning of the interventricular septum and the posterior wall in diabetic WT hearts were blocked in DGKζ-TG mice. Reduction of transverse diameter of cardiomyocytes isolated from the left ventricle in diabetic WT mice was attenuated in DGKζ-TG mice. Cardiac fibrosis was much less in diabetic DGKζ-TG than in diabetic WT mice. Western blots showed translocation of PKCβ and δ isoforms to membrane fraction and decreased Akt/PKB phosphorylation in diabetic WT mouse hearts. However in diabetic DGKζ-TG mice, neither translocation of PKC nor changes Akt/PKB phosphorylation was observed.

Conclusion

DGKζ modulates intracellular signaling and improves the course of diabetic cardiomyopathy. These data may suggest that DGKζ is a new therapeutic target to prevent or reverse diabetic cardiomyopathy.

Upregulation of myocardial 11S-activated proteasome in experimental hyperglycemia

This study examined the hypothesis that the ubiquitin proteasome system (UPS) degrades proteins damaged by exposure to hyperglycemia. Experimental hyperglycemia was induced in male rats by treatment with streptozotocin. After 30 days, echocardiography confirmed the presence of cardiomyopathy as ejection fraction, fractional shortening, and diastolic function (E/A ratio) were decreased, and chamber diameter was increased in hyperglycemic animals. Proteasome non-ATP-dependent chymotryptic activity was increased over 2-fold in hyperglycemic hearts, but the ATP-dependent activity was decreased and levels of ubiquitinated proteins were increased. Protein levels of the PA28alpha of the 11S-activator ring were increased by 128% and the PA28beta subunit increased by 58% in the hyperglycemic hearts. The alpha3 subunit of the 20S-proteasome was increased by 82% while the catalytic beta5 subunit was increased by 68% in hyperglycemic hearts. Protein oxidation as indicated by protein carbonyls was significantly higher in hyperglycemic hearts. These studies support the conclusion that the UPS becomes dysfunctional during long term hyperglycemia. However, 11S-activated proteasome was increased suggesting a response to oxidative protein damage and a potential role for this form of the proteasome in a cardiac pathophysiology.

Effect of streptozotocin-induced diabetes on left ventricular function in adult rats: an in vivo Pinhole Gated SPECT study

BACKGROUND

Recent studies have suggested that diabetes mellitus (DM) may cause left ventricular (LV) dysfunction directly resulting in increased susceptibility to heart failure. Using pinhole collimators and advances in data processing, gated SPECT was recently adapted to image the rat heart. The present study was aimed to assess this new imaging technique for quantifying LV function and remodeling from the Streptozotocin (STZ) rat model compared to controls.

METHODS

Twenty one rats were randomly assigned to control or diabetic group. Six months after the induction of diabetes by STZ, Pinhole 99 m Tc-sestamibi gated SPECT was performed for determining rat LV volumes and function. Post-mortem histopathologic analysis was performed to evaluate the determinant of LV remodeling in this model.

RESULTS

After six months, the normalized to body weight LV End-systolic volume was significantly different in diabetic rats compared to controls (0.46 +/- 0.02 vs 0.33 +/- 0.03 microL/g; p = 0.01). The normalized LV End-diastolic volume was also different in both groups (1.51 +/- 0.03 vs 0.88 +/- 0.05 microL/g; p = 0.001) and the normalized stroke volume was significantly higher in STZ-rats (1.05 +/- 0.02 vs 0.54 +/- 0.06 microL/g; p = 0.001). The muscular fibers were thinner at histology in the diabetic rats (0.44 +/- 0.07 vs 0.32 +/- 0.06 AU; p = 0.01).

CONCLUSION

Pinhole 99 m Tc-sestamibi gated SPECT can successfully be applied for the evaluation of cardiac function and remodeling in STZ-induced diabetic rats. In this model, LV volumes were significantly changed compared to a control population, leading to a LV dysfunction. These findings were consistent with the histopathological abnormalities. Finally, these data further suggest the presence of diabetes cardiomyopathy.

[Patient education in chronic polyarthritis. 3. Intermediate results of a prospective, controlled study of the effectiveness and side effects of patient seminars for polyarthritis patients]

Efficacy and possible negative side effects of a patient education program for rheumatoid arthritis were evaluated in a controlled, prospective study over 3 months. 34 outpatients were educated over a total of 8 h in three groups within a patient-centred design. Before the program the knowledge of the disease depended only on the formal grade of education but not on disease-related variables such as disease duration or disability. Probably due to its individualizing method, the program improved the knowledge of all patients to the same extent, regardless of their intellectual and social prerequisites. The increased cognitive knowledge did not result in negative side effects like increased pain or depression. The pain score remained unchanged. Depression decreased after the education. The group sessions made us suppose that the participants may have represented a selected group of active, psychologically stable patients, who cope well with rheumatoid arthritis. In contrast, we felt that non-participation was the response of the inactive, fatalistic patients with rheumatoid arthritis, who live in social isolation and especially need our care. Therefore, future efforts must particularly focus on the problem of motivation and on an increase in the rate of participation.