高胆固醇血症大鼠血管脂联素抵抗的机制探讨

Mechanisms of vascular adiponectin resistance in hypercholesterolemic rats

目的:观察高胆固醇血症大鼠血管对脂联素(adiponectin,APN)的反应是否发生改变,并探讨其相关机制。方法:将50只雄性SD大鼠随机分为10组,每组5只,分别以正常及高胆固醇饲料喂养0周、4周、8周、12周及16周。喂养结束后,麻醉采血检测血浆中胆固醇和APN的水平。分离大鼠主动脉,检测血管组织中腺苷酸活化的蛋白激酶(AMPK)的磷酸化(p-AMPK)和APN受体(adipoR1)表达的水平。将其血管组织与重组人APN(rAPN)共孵育,再次观察rAPN对血管组织中p-AMPK的影响。将大鼠血浆与rAPN共孵育4 h,观察孵育后的rAPN对人脐静脉血内皮细胞(HUVEC)p-AMPK的影响。结果:与喂养时间相同的正常饲料喂养组相比,以高脂饲料喂养8周、12周及16周后,血浆胆固醇的含量显著升高(8周:P<0.05;12周及16周:P<0.01)。与喂养时间相同的正常饲料喂养组比较,高脂饲料喂养8周时,血浆APN的水平显著升高(P<0.05),随后呈降低趋势,喂养16周时低于正常值。与喂养时间相同的正常饲料喂养组比较,rAPN激活的AMPK的水平在高脂饲料喂养12周后显著降低,且AdipoR1表达的水平在以高脂饲料喂养16周组中显著降低(P<0.05)。以高胆固醇血症大鼠血浆孵育的rAPN与以正常大鼠血浆孵育的rAPN相比,前者刺激HUVECs中AMPK磷酸化的水平显著降低(P<0.01)。结论:高胆固醇血症大鼠存在血管APN抵抗,早期与高脂血浆中存在某种物质抑制APN的活性有关,晚期还与APN的含量及AdipoR1水平的降低有关。

investigate to receive a AIM： To observe vascular responsiveness to adiponectin in hypercholesterolemic rats and to the mechanisms involved. METHODS： Fifty male Sprague Dawley （SD） rats were randomized regular rat chow diet or a high-fat diet for 0 - 16 weeks, and circulating cholesterol and adiponectin levels were determined. The aortas of rats were isolated and the expression of AMPK phosphoralytion （p-AMPK） and adiponectin receptor （AdipoR1） was detected. Aortas were incubated with recombinant full-length adiponectin （rAPN） and rAPN-induced AMPK phosphorylation was observed, rAPN was incubated with rat plasma for 4 h and then the effect of treated rAPN on AMPK phosphorylation in human umbilical vein endothelial cells was observed. RESULTS： Compared with that in rats fed with regular diet, cholesterol concentration increased after 8 weeks of the high-fat diet. Adiponectin levels in animals fed a high-fat diet significantly increased at 8 weeks and rapidly declined thereafter. The expression of rAPN-induced p-AMPK and AdipoR1 was reduced in rats fed a high-fat diet. Pre-incubation of rAPN with high-fat plasma rather than normal plasma significantly decreased the AMPK activation effect. CONCLUSION： The present study demonstrates that hypercholesterolemia causes vascular adiponectin resistance. Adiponectin modification/inactivation by unidentified factors in hypercholesterolemic plasma is likely responsible for early phase adiponectin resistance. A combination of adiponectin modification/inactivation reduced circulating adiponectin and decreased AdipoR1 expression and is responsible for late phase adiponectin resistance.