Naowaboot Jarinyaporn, Pannangpetch Patchareewan, Kukongviriyapan Veerapol, Kukongviriyapan Upa, Nakmareong Saowanee, Itharat Arunporn
Department of Pharmacology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
Nutr Res. 2009 Aug;29(8):602-8. doi: 10.1016/j.nutres.2009.06.002.
Free radical-induced vascular dysfunction plays a key role in the pathogenesis of vascular disease found in chronic diabetic patients. Morus alba (MA) leaf extract is promoted for good health especially in diabetic patients. Interestingly, antidiabetic and antioxidant activities of MA have been reported in experimental animals. Thus, the hypothesis of this study was that the long-term treatment with MA could improve vascular reactivity of chronic diabetic rats. To test this hypothesis, we examined the effect of long-term treatment with MA on the vascular responses to vasoactive agents in streptozotocin-induced chronic diabetic rats. The diabetic rats were either orally administered with distilled water, MA (0.25, 0.5 and 1 g/kg per day) or subcutaneously injected with insulin (4 U/kg per day) for 8 weeks. After each treatment, the fasting blood glucose, blood pressure, vascular responses to vasoactive agents and tissue malondialdehyde were examined. Morus alba at the doses of 0.5 and 1 g/kg, which significantly reduced blood glucose level, also significantly decreased the high blood pressure in diabetic rats. Vascular responses of the chronic diabetic rats to vasodilators, acetylcholine (3-30 nmol/kg) and sodium nitroprusside (1-10 nmol/kg) were significantly suppressed by 26% to 44% and 45% to 77% respectively, whereas those to vasoconstrictor, phenylephrine (0.01-0.1 micromol/kg) were significantly increased by 23% to 38% as compared to normal rats. Interestingly, the administration of 0.5 and 1 g/kg MA or 4 U/kg insulin significantly restored the vascular reactivities of diabetic rats. Moreover, 8 weeks of diabetes resulted in the elevation of malondialdehyde content in tissues (liver, kidney, heart, and aorta), and MA treatment significantly lessened this increase. These results provide the first evidence for the efficacy of MA in restoring the vascular reactivity of diabetic rats, the mechanism of which may associate with the alleviation of oxidative stress.
自由基诱导的血管功能障碍在慢性糖尿病患者血管疾病的发病机制中起关键作用。桑叶提取物对健康有益，尤其对糖尿病患者。有趣的是，实验动物中已报道了桑叶的抗糖尿病和抗氧化活性。因此，本研究的假设是长期给予桑叶可改善慢性糖尿病大鼠的血管反应性。为验证这一假设，我们研究了长期给予桑叶对链脲佐菌素诱导的慢性糖尿病大鼠血管对血管活性药物反应的影响。糖尿病大鼠分别口服蒸馏水、桑叶（0.25、0.5和1克/千克/天）或皮下注射胰岛素（4单位/千克/天），持续8周。每次治疗后，检测空腹血糖、血压、血管对血管活性药物的反应以及组织丙二醛含量。剂量为0.5和1克/千克的桑叶显著降低了血糖水平，同时也显著降低了糖尿病大鼠的高血压。慢性糖尿病大鼠对血管舒张剂乙酰胆碱（3 - 30纳摩尔/千克）和硝普钠（1 - 10纳摩尔/千克）的血管反应分别显著抑制了26%至44%和45%至77%，而对血管收缩剂去氧肾上腺素（0.01 - 0.1微摩尔/千克）的反应与正常大鼠相比显著增加了23%至38%。有趣的是，给予0.5和1克/千克的桑叶或4单位/千克的胰岛素可显著恢复糖尿病大鼠的血管反应性。此外，糖尿病8周导致组织（肝脏、肾脏、心脏和主动脉）中丙二醛含量升高，而桑叶治疗显著减轻了这种升高。这些结果首次证明了桑叶在恢复糖尿病大鼠血管反应性方面的功效，其机制可能与减轻氧化应激有关。
