左卡尼汀对自然衰老模型大鼠的心脏保护作用及其分子机制研究

Protective Effect of Levocarnitine on the Heart of Natural Aging Rats and Its Molecular Mechanism

背景左卡尼汀是重要的线粒体能量代谢调节物,其对衰老心脏是否具有保护作用尚不明确。目的以自然饲养的24月龄大鼠来构建自然衰老动物模型,研究左卡尼汀对自然衰老模型大鼠的心脏保护作用,并深入分析其分子机制。方法2017年1月—2019年6月,选取3月龄SPF级雄性大鼠30只。将在标准饲养环境下自然饲养至4月龄的大鼠作为青年对照组(n=10)。将在标准饲养环境下自然饲养至24月龄的大鼠随机分为左卡尼汀组(n=10)和老年对照组(n=10)。左卡尼汀组大鼠给予左卡尼汀300 mg·kg^-1·d^-1,老年对照组大鼠给予等量0.9%氯化钠溶液,均连续灌胃4周。记录并比较各组大鼠心脏收缩、舒张功能指标〔包括左心室舒张末期内径(LVEDD)、左心室收缩末期内径(LVESD)、左心室舒张末期容积(LVEDV)、左心室收缩末期容积(LVESV)、左心室射血分数(LVEF)、左心室短轴缩短率(LVFS)〕,血清丙二醛(MDA)水平、超氧化物歧化酶(SOD)活性,线粒体超微结构,心肌组织三磷酸腺苷(ATP)、磷酸化-AMP依赖的蛋白激酶(p-AMPK)、肉毒碱脂酰转移酶1(CPT-1)水平。结果老年对照组LVEDD、LVESD、LVEDV、LVESV大于青年对照组(P<0.05);左卡尼汀组LVESD、LVESV小于青年对照组,LVEF、LVFS高于青年对照组(P<0.05);左卡尼汀组LVEDD、LVESD、LVEDV、LVESV小于老年对照组,LVFS高于老年对照组(P<0.05)。老年对照组血清MDA水平高于青年对照组,SOD活性小于青年对照组(P<0.05);左卡尼汀组血清MDA水平高于青年对照组(P<0.05);左卡尼汀组血清MDA水平低于老年对照组,SOD活性大于老年对照组(P<0.05)。与青年对照组大鼠相比,老年对照组大鼠线粒体形态各异,部分线粒体肿胀明显,基质出现多个局灶性空泡;与老年对照组相比,左卡尼汀组大鼠心肌细胞线粒体体积明显缩小,偶见空泡变性,线粒体嵴排列整齐致密。老年对照组心肌组织ATP水平低于青年对照组(P<0.05);左卡尼汀组心肌组织ATP水平高于老年对照组(P<0.05)。老年对照组心肌组织p-AMPK、CPT-1水平低于青年对照组(P<0.05);左卡尼汀组心肌组织p-AMPK、CPT-1水平高于老年对照组(P<0.05)。结论左卡尼汀可改善自然衰老模型大鼠心脏功能,提高其抗氧化能力,保护衰老心肌线粒体结构和增加衰老心肌ATP生成,其机制可能与上调AMPK/CPT-1信号通路有关。

Background Levocarnitine palys an important role in mitochondrial energy metabolism,but whether it possesses protective effects on aging heart is unclear.Objective A natural aging animal model was constructed with 24 month-old rats fed naturally to study the protective effect of levocarnitine on the natural aging model rats,and its molecular mechanism was further analyzed.Methods A total of 30 three-month-old male SPF rats were selected from January 2017 to June 2019.Rats naturally raised to 4 months old in standard feeding environment were used as young control group(n=10).Rats naturally raised to 24 months old in standard feeding environment were randomly divided into the levocarnitine group(n=10)and the elderly control group(n=10).Rats in the levocarnitine group were given levocarnitine 300 mg·kg^-1·d^-1,and the rats in the elderly control group were given the same volume of 0.9%sodium chloride solution,and they were all fed for 4 weeks.The indexes of cardiac systolic and diastolic function(including LVEDD,LVESD,LVEDV,LVESV,LVEF,LVFS),serum MDA level,SOD activity,mitochondrial ultrastructure,levels of myocardial tissue ATP,p-AMPK,CPT-1 of rats were recorded and compared in each group.Results LVEDD,LVESD,LVEDV and LVESV in the elderly control group were larger than those in the young control group(P<0.05);LVESD and LVESV in the levocarnitine group were smaller than those in the young control group,and LVEF and LVFS were higher than those in the young control group(P<0.05);LVEDD,LVESD,LVEDV and LVESV in the levocarnitine group were smaller than those in the elderly control group,and LVFS was higher than that in the elderly control group(P<0.05).The serum MDA level of the elderly control group was higher than that of the young control group,and the SOD activity was lower than that of the young control group(P<0.05);the serum MDA level in the levocarnitine group was higher than that of the young control group(P<0.05);the serum MDA level in the levocarnitine group was lower than that in the elderly control group,and the SOD activity was greater than that in the elderly control group(P<0.05).Compared with the young control group,the elderly control group had different mitochondrial morphology,some mitochondria swelled obviously,and multiple focal vacuoles appeared in the matrix.Compared with the elderly control group,the mitochondrial volume of myocardial cells in the levocarnitine group was significantly reduced,and occasional vacuolar degeneration was observed,and the mitochondrial crests were neatly and densely arranged.The myocardial tissue ATP level of the elderly control group was lower than that of the young control group(P<0.05);the myocardial tissue ATP level of the levocarnitine group was higher than that of the elderly control group(P<0.05).The myocardial tissue p-AMPK and CPT-1 levels in the elderly control group were lower than those in the young control group(P<0.05);the myocardial tissue p-AMPK and CPT-1 levels in the levocarnitine group were higher than those in the elderly control group(P<0.05).Conclusion Levocarnitine can improve the cardiac function,enhance the antioxidant capacity,protect the mitochondrial structure and increase the ATP production of the aging myocardium in the natural aging model rats.The mechanism may be related to the upregulation of AMPK/CPT-1 signal pathway.