17β-oestradiol aggravates hyperglycemia-induced dysfunction of macrovascular tone regulation in ovariectomized female rats

• Main Authors: Chung-Yen Chen, 陳忠諺
• Other Authors: Chia-Hung Yen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/14528532502821190430

碩士 === 國立屏東科技大學 === 生物科技系所 === 102 === Diabetes causes vascular dysfunction. In our previous study has demonstrated that there is gender difference at the hyperglycemia-induced vascular dysfunction, it was more serious in diabetic female rats than that in diabetic male rats. Many study showed that endothelial cells is targets for estrogen. And there are some evidences showed that in some cases, estradiol (E2) have adverse effect on the blood vessels, like in post-menopausal woman, estrogen supplements increases risk of stroke and deep vein thrombosis. Therefore, we hypothesized that 17β-oestradiol (E2) plays an important role in the hyperglycemia-induced vascular dysfunction in female rats. Therefore, we used female Wistar rats divided into six groups, that is control, diabetic female rats (DM), diabetic ovariectomized female rats (OVX+DM), plus 17β-oestradiol (E2, 1mg/kg/week)-treated diabetic ovariectomized female rats (OVX+DM+E2), ovariectomized female rats(OVX), and plus 17β-oestradiol (E2, 1mg/kg/week)-treated ovariectomized female rats (OVX+E2) to examine whether 17β-oestradiol supplements are aggravated hyperglyciemia-induced macrovascular dysfunction in diabetic female rats. Diabetic rat induction via nicotinamide (180mg/kg) plus streptozotocin (90mg/kg) method and 17β-oestradiol supplements via subcutaneous injection for 1mg/kg/week. When rats persistent symptoms of hyperglycemia for eight weeks, we sacrificed rat, collected serum to measure E2 concentration, and isolated the thoracic aorta to evaluate the vascular functions using phenylephrine(PE), a α1-receptor agonist, to measure the vasocontractile response, acetylcholine(NO-cyclic GMP pathway stimulator, 10-8-10-5M), clonidine (α2-adrenoceptor agonist stimulator,10-7-10-5M) or insulin(PI3K/Akt pathway stimulator, 1.6-9.6μM) to demonstrate the vasorelaxation response, and nitro-L-arginine methyl ester(L-NAME), a nitric oxide synthase inhibitor, to assess the basal nitric oxide(NO) release from endothelium. Also, we measured the basal reactive oxygen species (ROS) production and the NADPH-related oxidase activity indirectly in thoracic aorta, renal artery, adipose and intestinal tissues by lucigenin-based chemiluminescence method. In the result, (1) In estradiol concentrations of serum, the ovariectomized group (24.6±1.6pg/mL) was significantly lower than that in control group (33.1±1.7pg/mL). And, in the 17β-oestradiol-treated group(41.4±5.8pg/mL) was significantly higher than that in ovariectomized group；(2) The fasting blood glucose of OVX+DM+E2 group(408±6 mg/dL) was significantly higher than that in OVX+DM group(356±6 mg/dL)；(3) The body weight of OVX+DM group was significantly higher than that in OVX+DM+E2 group(260±2g).(4)The acetylcholine-mediated endothelium-relaxation was significant lower in OVX+DM+E2 group( from 8.5±1.4 % to 88.8±2.1 %) than that in OVX+DM group (from 22.8±5.5% to 95.1±4.1%).；(5) basal endothelium-derived nitric oxide release was significantly reduced in OVX+DM+E2 group(24.4±2.9%) than that in OVX+DM group(37.2±5.6%).；(6) additionally, in adipose tissues, the basal ROS production and NADPH-related oxidase activity was significantly increased in OVX+DM+E2 group than that in OVX+DM group. But, in aorta, renal artery and intestine tissues was similar between these two groups.；(7) The clonidine-mediated vasorelaxation was significant lower in OVX+DM+E2 group than that in OVX+DM group. At the same time a similar situation was also appeared in the insulin-induced vasorelaxation. Our results clarified that extra 17β-oestradiol supplement could exacerbates hyperglycemia-related endothelium dysfunction in ovariectomized female rats, which was mediated by nitric oxide release, and whether it was in the case of acetylcholine stimulation. These phenomena whether associated with increasing oxidative stress of adipose tissue in 17β-oestradiol supplement ovariectomized diabetic rats, need to be further explored. Therefore, we recommend that estradiol replacement therapy should be more carefully assessed to apply on ovariectomzed or postmenopausal diabetic women, it could be an additional risk factor for macrovascular dysfunctions in these subjects.