利拉鲁肽对高脂饮食大鼠血清钠尿肽水平的影响及机制

Effect and mechanism of liraglutide on serum BNP level in rats after high-fat diet feeding

目的研究利拉鲁肽对高脂饮食大鼠血清钠尿肽水平的影响及机制。方法选择雄性清洁级SD大鼠24只,适应性喂养1周后随机分为对照组、高脂组、利拉鲁肽组,每组8只。测定各组血糖、血脂及钠尿肽水平,自噬关键分子酵母Atg6同系物(Beclin-1)和微管相关蛋白1轻链3(LC3)Ⅱ行免疫组织化学染色,RT-qPCR检测自噬相关基因mRNA表达,Western blot检测腺苷酸活化蛋白激酶(AMPK)、磷酸化AMPK(p-AMPK)、哺乳动物雷帕霉素靶蛋白(mTOR)、磷酸化mTOR(p-mTOR)、Beclin-1和LC3蛋白表达。结果与高脂组比较,利拉鲁肽组钠尿肽水平明显降低[(49.54±3.02)pg/ml vs(58.49±7.67)pg/ml,P<0.05]。免疫组织化学染色显示,高脂组和利拉鲁肽组心肌组织Beclin-1和LC3Ⅱ吸光度值较对照组明显降低,差异有统计学意义(P<0.05)。利拉鲁肽组心肌组织Beclin-1和LC3Ⅱ吸光度值较高脂组明显升高,差异有统计学意义(P<0.05)。RT-qPCR和Western blot检测结果显示,与对照组比较,高脂组心肌组织Beclin-1、LC3ⅡmRNA和蛋白表达明显降低,差异有统计学意义(P<0.05)。利拉鲁肽组心肌组织Beclin-1、LC3ⅡmRNA和蛋白表达较高脂组明显升高,差异有统计学意义(P<0.05)。与对照组比较,高脂组p-AMPK蛋白表达明显降低,p-mTOR蛋白表达明显升高,差异有统计学意义(P<0.05)。与高脂组比较,利拉鲁肽组p-AMPK蛋白表达明显升高(0.94±0.10 vs 0.53±0.16,P<0.05),p-mTOR蛋白表达明显降低(2.45±0.94 vs 3.04±0.81,P<0.05)。结论利拉鲁肽可降低高脂饮食大鼠钠尿肽水平,并且利拉鲁肽可能通过AMPK/mTOR信号通路促进自噬。

Objective To investigate the effect of liraglutide on serum brain natriuretic peptide(BNP)level in rats fed with high-fat diet,and to elucidate the underlying mechanisms.Methods A total of 24 male clean-grade SD rats were selected and randomly divided into control,high-fat and liraglutide groups,with 8 rats in each group.Blood glucose,lipid and BNP levels were measured in each group.Immunohistochemical staining was performed for the autophagy key molecule yeast Atg6 homolog(Beclin-1)and microtubule-associated protein 1 light chain 3(LC3)Ⅱ,and RT-qPCR was carried out to detect the mRNA expression of autophagy-related genes.Western blotting was adopted to detect the protein expression of adenylate-activated protein kinase(AMPK),p-AMPK,mTOR,p-mTOR,Beclin-1 and LC3.Results The serum BNP level was significantly lower in the liraglutide group than the high-fat group(49.54±3.02 pg/ml vs 58.49±7.67 pg/ml,P<0.05).The results of immunohistochemical staining revealed that the expressin levels of Beclin-1 and LC3Ⅱin myocardial tissue were significantly decreased in the high-fat group and liraglutide group than the control group(P<0.05),and the levels were obviously higher in the liraglutide group than the high-fat group(P<0.05).RT-qPCR and Western blotting showed that the expression of Beclin-1 and LC3Ⅱat mRNA and protein levels were significantly lower in the high-fat group than the control group(P<0.05),but liraglutide intervention resulted increased expression levels when compared with the high-fat group(P<0.05).Compared with the control group,the protein level of p-AMPK was significantly lower while that of p-mTOR obviously higher in the high-fat group(P<0.05).But liraglutide treatment reversed the above phenomena,with increased p-AMPK expression and decreased p-mTOR protein when compared with the high-fat group(0.94±0.10 vs 0.53±0.16,2.45±0.94 vs 3.04±0.81,P<0.05).Conclusion Liraglutide reduces the serum BNP level in rats fed with high-fat diet,and liraglutide may promote autophagy through AMPK/mTOR signaling pathway.