Rosiglitazone protects against ischemia/reperfusion-induced leukocyte adhesion in the zucker diabetic fatty rat

Beneficial Effects of Aerobic Exercise Training Combined with Rosiglitazone on Glucose Metabolism in Otsuka Long Evans Tokushima Fatty Rats

BACKGROUND

Regular aerobic exercise is essential for the prevention and management of type 2 diabetes mellitus and may be particularly beneficial for those treated with thiazolidinediones, since it may prevent associated weight gain. This study aimed to evaluate the effect of combined exercise and rosiglitazone treatment on body composition and glucose metabolism in obese diabetes-prone animals.

METHODS

We analyzed metabolic parameters, body composition, and islet profiles in Otsuka Long Evans Tokushima Fatty rats after 28 weeks of aerobic exercise, rosiglitazone treatment, and combined exercise and rosiglitazone treatment.

RESULTS

Combined exercise with rosiglitazone showed significantly less increase in weight and epididymal fat compared to rosiglitazone treatment. Aerobic exercise alone and combined rosiglitazone and exercise treatment led to similar retention of lean body mass. All experimental groups showed a decrease in fasting glucose. However, the combined exercise and rosiglitazone therapy group showed prominent improvement in glucose tolerance compared to the other groups. Rescue of islet destruction was observed in all experimental groups, but was most prominent in the combined therapy group.

CONCLUSION

Regular aerobic exercise combined with rosiglitazone treatment can compensate for the adverse effect of rosiglitazone treatment and has benefit for islet preservation.

MicroRNA-155 aggravates ischemia-reperfusion injury by modulation of inflammatory cell recruitment and the respiratory oxidative burst

The inflammatory sequelae of ischemia-reperfusion injury (IRI) are a major causal factor of tissue injury in various clinical settings. MicroRNAs (miRs) are short, non-coding RNAs, which regulate protein expression. Here, we investigated the role of miR-155 in IR-related tissue injury. Quantifying microRNA-expression levels in a human muscle tissue after IRI, we found miR-155 expression to be significantly increased and to correlate with the increased expression of TNF-α, IL-1β, CD105, and Caspase3 as well as with leukocyte infiltration. The direct miR-155 target gene SOCS-1 was downregulated. In a mouse model of myocardial infarction, temporary LAD ligation and reperfusion injury resulted in a smaller area of necrosis in miR-155-/- animals compared to wildtype animals. To investigate the underlying mechanisms, we evaluated the effect of miR-155 on inflammatory cell recruitment by intravital microscopy and on the generation of reactive oxygen species (ROS) of macrophages. Our intravital imaging results demonstrated a decreased recruitment of inflammatory cells in miR-155-/- animals during IRI. The generation of ROS in leukocytic cells of miR-155-/- animals was also reduced. RNA silencing of the direct miR-155 target gene SOCS-1 abrogated this effect. In conclusion, miR-155 aggravates the inflammatory response, leukocyte infiltration and tissue damage in IRI via modulation of SOCS-1-dependent generation of ROS. MiR-155 is thus a potential target for the treatment or prevention of IRI.

Exaggerated neutrophil-mediated reperfusion injury after ischemic stroke in a rodent model of type 2 diabetes

OBJECTIVE

We tested the hypothesis that both chronic and acute inflammatory processes contribute to worse reperfusion injury and stroke outcome in an experimental model of T2DM.

MATERIALS AND METHODS

Twelve- to thirteen-week-old male Zucker Diabetic Fatty (ZDF) rats vs. Zucker Lean Controls (ZLC) rats were tested at baseline and after middle cerebral artery occlusion (ischemia) and reperfusion (I-R). Neutrophil adhesion to the cerebral microcirculation, neutrophil expression of CD11b, infarction size, edema, neurologic function, sICAM, and cerebral expression of neutrophil-endothelial inflammatory genes were measured.

RESULTS

At baseline, CD11b and sICAM were significantly increased in ZDF vs. ZLC animals (p < 0.05). After I-R, significantly more neutrophil adhesion and cell aggregates were observed in ZDF vs. ZLC (p < 0.05); infarction size, edema, and neurologic function were significantly worse in ZDF vs. ZLC (p < 0.05). CD11b and sICAM-1 remained significantly increased in ZDFs (p < 0.05), and cerebral expression of IL-1β, GRO/KC, E-selectin, and sICAM were significantly induced in ZDF, but not ZLC groups (p < 0.05) after 2.5 hours of reperfusion.

CONCLUSION

Both sides of the neutrophil-endothelial interface appear to be primed prior to I-R, and remain significantly more activated during I-R in an experimental model of T2DM. Consequently, reperfusion injury appears to play a significant role in poor stroke outcome in T2DM.

Acute rosiglitazone treatment is cardioprotective against ischemia-reperfusion injury by modulating AMPK, Akt, and JNK signaling in nondiabetic mice

Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor (PPAR)-γ agonist, has been demonstrated to possess cardioprotective properties during ischemia-reperfusion. However, this notion remains controversial as recent evidence has suggested an increased risk in cardiac events associated with long-term use of RGZ in patients with type 2 diabetes. In this study, we tested the hypothesis that acute RGZ treatment is beneficial during I/R by modulating cardioprotective signaling pathways in a nondiabetic mouse model. RGZ (1 μg/g) was injected intravenously via the tail vein 5 min before reperfusion. Myocardial infarction was significantly reduced in mice treated with RGZ compared with vehicle controls (8.7% ± 1.1% vs. 20.2% ± 2.5%, P < 0.05). Moreover, isolated hearts were subjected to 20 min of global, no-flow ischemia in an ex vivo heart perfusion system. Postischemic recovery was significantly improved with RGZ treatment administered at the onset of reperfusion compared with vehicle ( P < 0.001). Immunoblot analysis data revealed that the levels of both phospho-AMP-activated protein kinase (Thr172) and phospho-Akt (Ser473) were significantly upregulated when RGZ was administered 5 min before reperfusion compared with vehicle. On the other hand, inflammatory signaling [phospho-JNK (Thr183/Tyr185)] was significantly downregulated as a result of RGZ treatment compared with vehicle ( P < 0.05). Intriguingly, pretreatment with the selective PPAR-γ inhibitor GW-9662 (1 μg/g iv) 10 min before reperfusion significantly attenuated these beneficial effects of RGZ on the ischemic heart. Taken together, acute treatment with RGZ can reduce ischemic injury in a nondiabetic mouse heart via modulation of AMP-activated protein kinase, Akt, and JNK signaling pathways, which is dependent on PPAR-γ activation.

Management of cardiac fibrosis in diabetic rats; the role of peroxisome proliferator activated receptor gamma (PPAR-gamma) and calcium channel blockers (CCBs)

BACKGROUND

Diabetes mellitus (DM) and hypertension (HTN) are accused of being responsible for the development of the cardiac fibrosis due to severe cardiomyopathy.

METHODS

Blood glucose (BG) test was carried out, lipid concentrations, tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), matrix metalloproteinase (MMP-2), collagen-I and collagen-III were measured in male Albino rats weighing 179-219 g. The rats were divided into five groups, kept on either control diet or high fat diet (HFD), and simultaneously treated with rosiglitazone (PPAR-gamma) only for one group with 3 mg/kg/day via oral route for 30 days, and with rosiglitazone and felodipine combination for another group with 3 mg/kg/day and 5 mg/kg/day, respectively via oral route for 30 days.

RESULTS

Diabetic hypertensive (DH) rats which fed on a HFD, injected with streptozotocin (STZ) (i.p.) and obstruction for its right kidney was occurred develop hyperglycemia, hypertension, cardiac fibrosis, hypertriglyceridemia, hypercholesterolemia, increased TNF-α, increased TGF-β, decreased MMP-2, increased collagen-I and increased collagen-III, when compared to rats fed on control diet. Treating the DH rats with rosiglitazone only causes a significant decrease for BG levels by 52.79%, triglycerides (TGs) by 24.05%, total cholesterol (T-Chol) by 30.23%, low density lipoprotein cholesterol (LDL-C) by 40.53%, TNF-α by 20.81%, TGF-β by 46.54%, collagen-I by 48.11% and collagen-III by 53.85% but causes a significant increase for MMP-2 by 272.73%. Moreover, Treating the DH rats with rosiglitazone and felodipine combination causes a significant decrease for BG levels by 61.08%, blood pressure (BP) by 16.78%, TGs by 23.80%, T-Chol by 33.27%, LDL-C by 45.18%, TNF-α by 22.82%, TGF-β by 49.31%, collagen-I by 64.15% and collagen-III by 53.85% but causes a significant increase for MMP-2 by 290.91%. Rosiglitazone alone failed to decrease the BP in DH rats in the current dosage and duration.

CONCLUSION

Our results indicate that the co-existence of diabetes and hypertension could induce cardiomyopathy which could further result in cardiac fibrosis, and that combination treatment with rosiglitazone and felodipine has a great protective role against the metabolic abnormalities, meanwhile, the treatment with rosiglitazone alone has a protective role with a minimal effect against these abnormalities and has no effect on decreasing BP in these cases which may lead to coronary artery diseases (CADs) in future.

Pharmacogenomic, physiological, and biochemical investigations on safety and efficacy biomarkers associated with the peroxisome proliferator-activated receptor-gamma activator rosiglitazone in rodents: a translational medicine investigation

Peroxisome proliferator-activated receptor (PPAR)-gamma modulators, a class of antidiabetic drugs, have been associated with cardiovascular risks in type 2 diabetes in humans. The objective of this study was to explore possible cardiovascular risk biomarkers associated with PPAR-gamma in rodents that could provide an alert for risk to humans. Normal, myocardial infarction-induced heart failure (HF) or Zucker diabetic fatty (ZDF) rats were used. Rats (n = 5-6) were treated with either vehicle or rosiglitazone (RGZ; 3 or 45 mg/kg/day p.o.) for 4 weeks. Biomarkers for potential cardiovascular risks were assessed, including 1) ultrasound for cardiac structure and function; 2) neuroendocrine and hormonal plasma biomarkers of cardiovascular risk; 3) pharmacogenomic profiling of cardiac and renal tissue by targeted tissue low-density gene array representing ion channels and transporters, and components of the renin-angiotensin-aldosterone system; and 4) immunohistochemistry for cardiac fibrosis, hypertrophy, and inflammation (macrophages and tumor necrosis factor-alpha). HF was confirmed by increase in cardiac brain natriuretic peptide expression (p < 0.01) and echocardiography. Adequate exposure of RGZ was confirmed by pharmacokinetics (plasma drug levels) and the pharmacodynamic biomarker adiponectin. In normal or HF rats, RGZ had no negative effects on any of the biomarkers investigated. Similarly, RGZ had no significant effects on gene expression except for the increase in interleukin-6 mRNA expression in the heart and decrease in epithelial sodium channel beta in the kidney. In contrast, echocardiography showed improved cardiac structure and function after RGZ in ZDF rats. Taken together, this study suggests a limited predictive power of these preclinical models in respect to observed clinical adverse effects associated with RGZ.

Rosiglitazone reverses endothelial dysfunction but not remodeling of femoral artery in Zucker diabetic fatty rats

OBJECTIVES

Endothelial dysfunction precedes atherogenesis and clinical complications in type 2 diabetes. The vascular dysfunction in Zucker diabetic fatty (ZDF) rats was evaluated at different ages along with the effect of treatment with rosiglitazone (Rosi) on endothelial function and mechanical remodeling.

METHODS

The Rosi treatment was given to ZDF rats for 3 weeks. The endothelium-dependent vasodilation and alpha-adrenoceptor-dependent vasoconstriction of femoral arteries were studied using an ex-vivo isovolumic myograph. The biomechanical passive property of the arteries was studied in Ca2+-free condition. The expressions of endothelial nitric oxide synthase (eNOS), alpha-adrenoceptor, matrix metalloproteinase 9 (MMP9), and elastase were evaluated.

RESULTS

Endothelium-dependent vasorelaxation of the femoral artery was blunted at low doses in ZDF rats at 11 weeks of age and attenuated at all doses in ZDF rats at 19 weeks of age. The expression of eNOS was consistent with the endothelium-dependent vasorelaxation. The alpha-adrenoceptor was activated and the mechanical elastic modulus was increased in ZDF rats at 19 weeks of age. The expressions of alpha-adrenoceptor, MMP9, and elastase were up regulated in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks restored endothelium-dependent vasorelaxation and the expression of eNOS and the adrenoceptor activation at the doses below 10-6 mole/L in ZDF rats at 19 weeks of age. Rosi treatment for 3 weeks did not, however, improve the mechanical properties of blood vessel, the expressions of alpha-adrenoceptor, MMP9, and elastase in ZDF rats.

CONCLUSION

The endothelial dysfunction and mechanical remodeling are observed as early as 19 weeks of age in ZDF rat. Rosi treatment for 3 weeks improves endothelial function but not mechanical properties.

A randomised controlled trial on melatonin and rosiglitazone for prevention of adhesion formation in a rat uterine horn model

PURPOSE

To investigate the effectiveness of melatonin and rosiglitazone in reducing postoperative adhesion formation in a rat uterine horn model.

METHODS

Thirty non-pregnant female Wistar albino rats, weighing 180-220 g, were used as a model for postoperative adhesion formation. The rats were randomised into three groups after seven standard lesions were inflicted in a 2-cm segment of each uterine horn and lower abdominal sidewall using bipolar cauterisation. The rats were treated with 10 mg/kg, intraperitoneal melatonin, and 1 mg/kg per day peroral rosiglitazone. No medication was given to the control group. As much as 20 uterine horns of 10 rats were evaluated in each group. Extent, severity, and degree of the adhesions to the uterine horns and, inflammation and fibrosis scores (histopathologically) were evaluated after 2 weeks of the treatment.

RESULTS

There was no mortality in the groups and all of the rats recovered without incident after operation. Rosiglitazone group had lower adhesion scores [median (min-max ranges)] regarding extent, severity, and degree of the adhesions [0 (0-3), 0 (0-3) and 0 (0-3), respectively], which were significantly different (P < 0.001, P < 0.05 and P < 0.01, respectively) from those of the controls [1 (0-3), 2 (0-2) and 2 (0-3), respectively]; however, there were no statistically significant differences between rosiglitazone versus melatonin groups [1 (0-4), 2 (0-3) and 1 (0-3), respectively] and melatonin versus control groups. Moreover, no significant differences were determined between groups regarding histopathologic findings.

CONCLUSION

Rosiglitazone, but not melatonin, is effective in prevention of adhesion formation in a rat uterine horn model.

Heme-oxygenase induction inhibits arteriolar thrombosis in vivo: effect of the non-substrate inducer cobalt protoporphyrin

Heme oxygenase-1 (HO) metabolizes heme to form the vasodilator carbon monoxide and antioxidant biliverdin. Upregulation of HO-1 by hemin, which is also a substrate attenuates thrombosis in rodent models, however, whether protection is due to HO-1 upregulation or to increased substrate availability is unknown. This study tested the hypothesis that treatment of mice with cobalt protoporphyrin (CoPP), a non-substrate HO-1 inducer, would protect the endothelium from laser injury. C57Bl/J6 mice were treated with vehicle, CoPP (20 mg/kg), CoPP plus the HO-1 inhibitor tin protoporphyrin (SnPP; 20 mg/kg) or SnPP alone for 18 h. Intravital microscopy was used to quantitate thrombus formation in cremaster arterioles in response to laser ablation of the endothelium. CoPP treatment inhibited thrombosis by 43% compared to vehicle (P<0.05). SnPP co-treatment negated the inhibitory effect of CoPP while SnPP alone potentiated thrombosis compared to vehicle. In CoPP-treated animals, cremaster HO-1 mRNA expression was increased 59+/-17-fold over vehicle (P<0.001). Co-treatment with CoPP+SnPP attenuated this effect by 36%, however the increase in HO-1 protein induced by CoPP was unaffected by SnPP. Induction of HO-1 by the non-substrate inducer CoPP protects against laser induced endothelial injury without the need for increased substrate. Small molecule, substrate-independent upregulation of HO-1 expression represents a feasible approach to ameliorate endothelial dysfunction in cardiovascular disease.

Pancreatic islet overproduction of H2S and suppressed insulin release in Zucker diabetic rats

Hydrogen sulfide (H(2)S) has been traditionally known for its toxic effects on living organisms. The role of H(2)S in the homeostatic regulation of pancreatic insulin metabolism has been unclear. The present study is aimed at elucidating the effect of endogenously produced H(2)S on pancreatic insulin release and its role in diabetes development. Diabetes development in Zucker diabetic fatty (ZDF) rats was evaluated in comparison with Zucker fatty (ZF) and Zucker lean (ZL) rats. Pancreatic H(2)S production and insulin release were also assayed. It was found that H(2)S was generated in rat pancreas islets, catalyzed predominantly by cystathionine gamma-lyase (CSE). Pancreatic CSE expression and H(2)S production were greater in ZDF rats than in ZF or ZL rats. ZDF rats exhibited reduced serum insulin level, hyperglycemia, and insulin resistance. Inhibition of pancreatic H(2)S production in ZDF rats by intraperitoneal injection of DL-propargylglycine (PPG) for 4 weeks increased serum insulin level, lowered hyperglycemia, and reduced hemoglobin A1c level (P<0.05). Although in ZF rats it also reduced pancreatic H(2)S production and serum H(2)S level, PPG treatment did not alter serum insulin and glucose level. Finally, H(2)S significantly increased K(ATP) channel activity in freshly isolated rat pancreatic beta-cells. It appears that insulin release is impaired in ZDF because of abnormally high pancreatic production of H(2)S. New therapeutic approach for diabetes management can be devised based on our observation by inhibiting endogenous H(2)S production from pancreas.

Potential of 3,4-dihydroxy-phenyl lactic acid for ameliorating ischemia-reperfusion-induced microvascular disturbance in rat mesentery

This study intended to examine the effect of 3,4-dihydroxy-phenyl lactic acid (DLA), a major ingredient of Salvia miltiorrhiza, on ischemia-reperfusion (I/R)-induced rat mesenteric microcirculatory injury. DLA (5 mg.kg(-1).h(-1)), superoxide dismutase (SOD, 12,000 U.kg(-1).h(-1)), or catalase (CAT, 20 mg/kg) was continuously infused either starting from 10 min before the ischemia or 10 min after the initiation of reperfusion. The venule diameter, number of adherent leukocytes, FITC-albumin leakage, dihydrorhodamine 123 fluorescence, and mast cell degranulation were determined using an intravital microscope. The production of hydrogen peroxide (H(2)O(2)) and the expression of adhesion molecules CD11b/CD18 in neutrophils were evaluated by in vitro experiments. The results showed that pretreatment with DLA significantly reduced peroxide production in and leukocyte adhesion to venular wall, albumin leakage, and mast cell degranulation induced by I/R. The DLA posttreatment exerted an ameliorating effect on I/R-induced disorders as well, characterized by inhibiting further increase in peroxide production in venular wall and albumin leakage and diminishing the number of leukocytes that had adhered to the venular wall. In vitro experiments revealed that treatment with DLA significantly attenuated TNF-alpha plus fMLP-evoked production of H(2)O(2) and the H(2)O(2)-elicited expression of CD11b/CD18 on neutrophils. SOD and CAT manifested similarly but with the exception that either SOD or CAT were unable to retrieve the adherent leukocytes if administrated after initiation of reperfusion and to depress the H(2)O(2)-induced expression of CD11b/CD18 on neutrophils. It is concluded that DLA protects from and ameliorates the I/R-induced microcirculatory disturbance by interfering with both peroxide production and adhesion molecule expression.

Cardiac remodeling in obesity

The dramatic increase in the prevalence of obesity and its strong association with cardiovascular disease have resulted in unprecedented interest in understanding the effects of obesity on the cardiovascular system. A consistent, but puzzling clinical observation is that obesity confers an increased susceptibility to the development of cardiac disease, while at the same time affording protection against subsequent mortality (termed the obesity paradox). In this review we focus on evidence available from human and animal model studies and summarize the ways in which obesity can influence structure and function of the heart. We also review current hypotheses regarding mechanisms linking obesity and various aspects of cardiac remodeling. There is currently great interest in the role of adipokines, factors secreted from adipose tissue, and their role in the numerous cardiovascular complications of obesity. Here we focus on the role of leptin and the emerging promise of adiponectin as a cardioprotective agent. The challenge of understanding the association between obesity and heart failure is complicated by the multifaceted interplay between various hemodynamic, metabolic, and other physiological factors that ultimately impact the myocardium. Furthermore, the end result of obesity-associated changes in the myocardial structure and function may vary at distinct stages in the progression of remodeling, may depend on the individual pathophysiology of heart failure, and may even remain undetected for decades before clinical manifestation. Here we summarize our current knowledge of this complex yet intriguing topic.

Diabetic cardiomyopathy revisited

Diabetes mellitus increases the risk of heart failure independently of underlying coronary artery disease, and many believe that diabetes leads to cardiomyopathy. The underlying pathogenesis is partially understood. Several factors may contribute to the development of cardiac dysfunction in the absence of coronary artery disease in diabetes mellitus. This review discusses the latest findings in diabetic humans and in animal models and reviews emerging new mechanisms that may be involved in the development and progression of cardiac dysfunction in diabetes.