Modulation of metabolic and cardiac dysfunctions by insulin sensitizers and angiotensin receptor blocker in rat model of type 2 diabetes mellitus

Department of Medical Physiology, Faculty of Medicine, Mansoura University, Egypt.
Canadian Journal of Physiology and Pharmacology (Impact Factor: 1.77). 03/2011; 89(3):216-26. DOI: 10.1139/Y11-012
Source: PubMed


The objective of this study was to investigate the modulation of metabolic dysfunctions, adiponectin levels, and cardiac dysfunctions of type 2 diabetes mellitus (T2DM) by a combination of the insulin sensitizer rosiglitazone and angiotensin receptor blocker telmisartan in an experimental rat model. Fifty male adult Sprague-Dawley rats were divided equally into 5 groups. Group I: fed normal chow; served as normal control group. Groups II-V: fed a high-fat diet (HFD) for 2 weeks, followed by injection of streptozotocin (STZ; 35 mg/kg) to create a model of T2DM. Group II: treated with vehicle. Group III: treated with rosiglitazone (4 mg/kg). Group IV: treated with telmisartan (5 mg/kg). Group V: treated with both agents. Untreated HFD-STZ rats showed elevated fasting blood glucose, insulin, homeostasis model assessment (HOMA) index, triglycerides (TGs), low-density lipoprotein cholesterol (LDL), and total serum cholesterol (TC), with a decrease in high-density lipoprotein cholesterol (HDL) and adiponectin levels (p < 0.001). Rosiglitazone exerted more improvement in all parameters than telmisartan did, and a combination of both did not augment the improvement further, except for TGs and adiponectin. For the isolated atrial study, a combination of rosiglitazone and telmisartan corrected the responses of the atria of HFD-STZ rats to the negative inotropic effect induced by adenosine better than either one did alone, whereas this combination, surprisingly, significantly attenuated the positive inotropic response to β-adrenoreceptor and α-adrenoreceptor agonists. In conclusion, rosiglitazone significantly improved the metabolic and cardiac dysfunctions in T2DM. Moreover, a combination of rosiglitazone and telmisartan offered more improvement in serum TGs and adiponectin, and restored the atrial inotropic response to adenosine. Surprisingly, this combination significantly attenuates the positive inotropic response to α1-adrenoreceptor and β-adrenoreceptor agonists.

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    ABSTRACT: Zinc is a trace metal and acts as an active component of various enzymes. Zinc deficiency has been suggested to be associated with the development of diabetes. The present study investigated the role of zinc supplementation on prevention of diabetic conditions. A double-disease model mimicking hyperlipidemia and type 2 diabetes was created by applying high-fat diet and streptozotocin (STZ) to Wistar rats. We demonstrated that zinc supplementation improved symptoms of diabetes such as polydipsia and increased serum level of high-density lipoprotein cholesterol, indicating that zinc supplementation has a potential beneficial effect on diabetic conditions. The level of maldondialdehyde (MDA), an oxidative stress marker, was reduced in liver by zinc supplementation in high fat-fed rats with or without STZ injection. Meanwhile, we observed an increase in the expression of metallothioneins (MTs) in liver of rats treated with zinc. This suggests that the induction of MTs in liver, which has been shown to be important in scavenging free radicals, could be one of the underlying mechanisms of zinc supplementation on reducing MDA levels in liver. Finally, we found that zinc levels in liver were increased while there was no change in serum zinc levels, indicating that local zinc level might be a critical factor for the induction of MTs. Also, the level of MTs could potentially be an index of zinc bioavailability. Taken together, these results suggest that both zinc and MT could play an important role in balancing nutrition and metabolism to prevent diabetic development.
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