Endothelium-dependent effect of sesame seed feeding on vascular reactivity of streptozotocin-diabetic rats: underlying mechanisms

Cardiovascular disorders continue to constitute major causes of morbidity and mortality in diabetic patients. In this study, the effect of chronic administration of sesame [Sesamum indicum L] seed feeding was studied on aortic reactivity of streptozotocin [STZ]-diabetic rats. Male diabetic rats received sesame seed-mixed food at weight ratios of 3% and 6% for 7 weeks, one week after diabetes induction. Contractile responses to KCl and phenylephrine [PE] and relaxation response to acetylcholine [ACh] and sodium nitroprusside [SNP] were obtained from aortic rings. Maximum contractile response of endothelium-intact rings to PE was significantly lower in sesame-treated diabetic rats [at a ratio of 6%] relative to untreated diabetics and endothelium removal abolished this difference. Endothelium-dependent relaxation to ACh was also significantly higher in sesame-treated diabetic rats [at a ratio of 6%] as compared to diabetic rats and pretreatment of rings with nitric oxide synthase inhibitor, N[G]-nitro-l-arginine methyl ester [L-NAME] significantly attenuated the observed response. Two-month diabetes also resulted in an elevation of malondialdehyde [MDA] and decreased superoxide dismutase [SOD] activity and sesame treatment significantly reversed the increased MDA content and restored activity of SOD. We thus conclude that chronic treatment of diabetic rats with sesame seed could in a dose- manner prevent some abnormal changes in vascular reactivity through nitric oxide and via attenuation of oxidative stress in aortic tissue and endothelium integrity is necessary for this beneficial effect

[ effect of curcumin on serum level of aspartate and alanine amoinotransferase and cardiac level of oxidative stress markers in diabetic rats]

Diabetes mellitus in long term accompanies with enhanced oxidative stress and decreased activity of antioxidant defense system. Due to antidiabetic and antioxidant activity of effective constituent of turmeric, curcumin, the effect of this component on serum level of aspartate and alanine aminotransferase and cardiac level of some oxidative stress markers were determined. In this experimental study, rats were divided into 5 groups, i.e. control, curcumin-treated control [50 mg/kg], diabetic, and curcumin-treated diabetic groups [10 and 50 mg/kg]. Curcumin was administered 7 days after streptozotocin injection for 5 weeks. Serum level of aspartate and alanine aminotransferase and heart tissue level of malondialdehyde [MDA] and nitrite and activity of Superoxide dismutase [SOD] were measured. Diabetic rats showed a significant increase in serum level of aspartate and alanine aminotransferase [p<0.01-0.05], while high-dose curcumin significantly reduced serum level of these enzymes [p<0.05]. In addition, diabetes was followed by increased level of MDA and nitrite in heart tissue [p<0.05-0.01] and non-significant decrease of SOD activity, whlie high-dose curcumin treatment significantly reduced MDA and nitrite level [p<0.05] and did not significantly change activity of SOD. Chronic treatment with curcumin could improve serum level of alanine and aspartate aminotransferase and some oxidative stress markers in cardiac tissue of diabetic rats

effect of crataegus spp branchlet feeding on endothelium-dependent contractile and relaxatory response of thoracic aorta from diabetic rats

Diabetes mellitus is accompanied with higher incidence of cardiovascular disorders. There is some evidence on antidiabetic and cardiovascular improving potential of Crataegus spp [CS]. Thus, the endothelium-dependent effect of oral administration of CS branchlet for 6 weeks on contractile and relaxatory response of thoracic aorta from diabetic rats was investigated. Male Wistar rats were divided into control, CS-treated control, diabetic, CS-treated diabetic, and glibenclamide-treated diabetic groups. Treated groups received CS-mixed pelleted food at a weight ratio of 6.25%. Body weight and serum glucose level was measured before the study and at weeks 3 and 6. At the end of study, contractile reactivity of thoracic aortic rings to KC1 and phenylephrine and relaxatory response to acetylcholine and sodium nitroprusside was determined using isolated tissue setup. Serum glucose level significantly decreased in CS-treated diabetic group [p<0.01] versus untreated diabetics. In addition, endothelium-intact CS-treated diabetic group showed a significantly lower contraction to KC1 and phenylephrine [p<0.05] as compared to diabetic group and endothelium removal abolished this response. Meanwhile, relaxation response of endothelium-intact rings to acetylcholine was significantly higher in CS-treated diabetic group as compared to diabetics [p<0.05]. In addition, there were no significant changes amongst the groups regarding relaxatory response to sodium nitroprusside. Chronic oral administration of CS through affecting endothelial-related agents could decrease contractile response and enhance relaxatory response in aortic tissue of diabetic rat and this may be beneficial in prevention of long-term vascular complications of diabetes

Quinapril attenuates the effect of long-term L-NAME administration on the vascular reactivity of diabetic rats

Angiotensin-converting enzyme [ACE] inhibitors including quinapril could exert a protective effect on cardiovascular system through endothelial system in normoglycemic and diabetic rats. The present experimental work was designed to study the vascular reactivity of aortic ring segments isolated from streptozotocin [STZ]-diabetic rats treated for 4 weeks with nitro-L-arginine-methyl ester [L-NAME; 50 mg/100 ml] or L-NAME plus quinapril [10 mg/100 ml] in drinking water. The results showed that quinapril treatment significantly attenuated the augmented contractile response to phenylephrine and KC1 in diabetic rats. In addition, quinapril treatment partially restored the reduced contractile response in diabetic animals treated chronically with L-NAME. It can be concluded that quinapril could partly counteract the effect of long-term L-NAME administration on vascular reactivity in STZ-diabetic rats