小檗碱对糖尿病db/db小鼠骨骼肌蛋白质代谢的影响及机制研究
Effects of berberine on skeletal muscle protein metabolism in db/db mice and study of its mechanism
目的 探讨小檗碱对糖尿病/胰岛素抵抗模型db/db小鼠骨骼肌蛋白质代谢及肌萎缩蛋白Fbox-1(Atrogin-1)表达的影响.方法 db/db小鼠为研究对象,以野生型为对照组.予小檗碱(5 mg·kg-1·d-1)腹腔注射3周,观察体重和食量;3周末处死,分离胫骨前肌和腓肠肌.胫骨前肌冰冻切片行层黏连蛋白免疫组化染色,荧光显微镜下观察并拍照,测量肌纤维横截面积并计算肌纤维面积分布图;同位素[14C]-苯丙氨酸掺入法检测肌肉蛋白合成,[3H]-酪氨酸释放率分析检测肌肉分解代谢;Northern印迹检测腓肠肌Atrogin-1和肌环指蛋白1(MurF-1)转录水平,Western印迹检测蛋白翻译水平.结果 小檗碱能明显降低db/db小鼠血糖水平[(18.55---3.79对26.32±4.02)mmol/L,P<0.01],降低脂肪重量[(2.75±0.30对3.77±0.52)g,P<0.05],使胫骨前肌的肌重/胫骨长度比值及肌纤维横截面积下降,肌纤维面积分布图明显左移;小檗碱使野生型j、鼠和db/db小鼠的蛋白质合成率下降18% ~ 22%;蛋白质分解率升高24%~ 26%,使肌肉特异性的Atrogin-1、MurF-1转录和翻译水平增高,同时使真核转录因子3调节亚基(eIF3-f)蛋白水平降低.结论 小檗碱具有降糖降脂作用,但可引起骨骼肌蛋白质合成下降,促进蛋白质分解代谢,加剧糖尿病的骨骼肌消耗,其机制与上调Atrogin-1和MurF-1表达,同时下调elF3-f有关.
更多Objective To study the effect of berberine on diabetes or insulin resistance accompanied with reduction of skeletal moscle and wasting in db/db mice.Methods db/db mouse-a model of diabetes/insulin-resistance was studied,with the wild type mouse as control.After being treated with berberine ( 5 mg · kg-1 · d-1 ) for 3 weeks,the muscle size of tibia anterior (TA) of the animals was measured after staining with laminine/Hyosin Heavy chain-Slow using immunochemistry,then observed under fluorescent microscope and calculated with software.The rate of [ 14 C ] -Phenalanine incorporation into the uuscle was measured to analyze the protein synthesis,and the [ 3 H ] -Tyrosine released into the medium was determined in order to analyze protein degradation.The mRNA expressions of muscle atrophy Fbox-1 ( Atrogin-1 ) and muscle ring finger-1 ( MuRF-1 ) were measured by Northern blot.Results With berberine treatment,blood glucose and fat levels were lowered [ ( 18.55 ± 3.79 vs 26.32 ± 4.02 ) mmol/L,P<0.01 ; ( 2.75 ± 0.30 vs 3.77 ± 0.52 ) g,P<0.05 ],but tibia anterior muscle weight/length ratio and cross-section area were decreased,rates of protein synthesis in isolated muscles of db/db mice were decreased by 18% -22%,and the rates of degradation were significantly raised by 24% -26% after berberine treatment.There also was increased the transcription and translation of Atrogin-1 and MuRF-1,accompanied with decreased eukaryotic initiation factor 3 subunit (eIF3-f) protein level simultaneously. Conclusion Berberine improves hyperglycemia and insulin resistance by down-regulating blood sugar and body fat,but it causes reduced protein synthesis and minimally enhanced protein degradation.The mechanism might be related to berberine-induced up-regulating Atrogin-1 、MurF-1 and down-regulating eIF3-f.
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