NMN长期补充对老年小鼠心功能的影响及机制研究

Effects of Long-term Supplementation of NMN on Heart Function in Old Mice and Its Mechanism

目的探讨烟酰胺单核苷酸(nicotinamide mononucleotide,NMN)对老年小鼠心功能的影响及机制。方法采用随机分组对照研究方法,选择3月龄C57BL/6J雄性小鼠。设置年轻组:不做任何处理,适应性喂养至4月龄;老年组:继续饲养至12~16月龄;实验组:于代谢笼中继续饲养至12~16月龄,监测饮水量,饮水中添加NMN[300mg/(kg·d)]。监测小鼠体质量变化,行口服葡萄糖耐量实验(oral glucose tolerance test,OGTT)。检测心脏烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleotide,NAD+)含量。超声检测小鼠心功能。检测氧化应激相关指标,脂质过氧化终产物丙二醛(malondialdehyde,MDA)含量、超氧化物歧化酶(superoxide dismutase,SOD)活性及蛋白过氧化水平。检测心肌腺嘌呤核苷三磷酸(adenosine triphosphate,ATP)含量及线粒体DNA(mtDNA)数目。结果与年轻组比较,老年组小鼠体质量明显增长;葡萄糖耐量受损,心肌NAD+含量下降。反映心脏舒张功能的舒张早期和舒张晚期血流速度比值(early ventricular diastole/late ventricular diastole,E/A)以及反映收缩功能的左心室射血分数(left ventricular ejection fraction reflecting,LVEF)和左心室短轴缩短率(left ventricular fraction shortening,LVFS)均下降。同时发现心肌组织MDA含量明显增加、SOD活性降低,羰基化的蛋白增多。心肌ATP含量和mtDNA拷贝数均明显减少。与老年组比较,实验组小鼠体质量增长不显著,糖耐量受损减轻。心脏NAD+含量增高,E/A值,LVEF及FS均增高,氧化应激改善。心肌ATP含量和mtDNA拷贝数上升。结论长期使用NMN恢复心脏NAD+水平并减轻线粒体损伤,最终改善老年小鼠心功能。

Objective To investigate the effects of nicotinamide mononucleotide(NMN)on cardiac function in aged mice and its potential mechanism.Methods Using randomized controlled study method,3-month-old C57BL/6J male mice were selected.Young group:adaptive feeding to 4months of age without any treatment;old group:continue feeding for 12 to 16months of age;experimental group:mice were kept in the metabolic cage for 12 to 16months of age,and the volume of drinking water was monitored.NMN[300mg/(kg·d)]was administered through add libitum drinking water.The body weight of mice was continuously monitored,and oral glucose tolerance test(OGTT)was performed.The content of nicotinamide adenine dinucleotide(NAD+)in the heart was detected.The cardiac function of mice was detected by ultrasound.Oxidative stress related markers:content of malondialdehyde(MDA),the activity of superoxide dismutase(SOD)and the level of protein peroxidation were detected.The myocardial ATP content and mtDNA copy number were detected.Results Compared with the young group,the body weight of the old group increased significantly;the glucose tolerance was impaired,and the myocardial NAD+content decreased.The early ventricular diastole/late ventricular diastole(E/A)ratio reflecting diastolic function,the left ventricular ejection fraction reflecting(LVEF)and left ventricular fraction shortening(LVFS)reflecting systolic function were decreased.Meanwhile,the content of MDA was increased significantly,the activity of SOD was decreased,and carbonylation of protein was increased.The ATP content and mtDNA copy number were significantly reduced.Compared with the old group,the weight gain of experimental group was not significant,and the glucose tolerance was improved.The content of cardiac NAD+,E/A value,LVEF and LVFS were increased,and the oxidative stress was attenuated.Myocardial ATP content and mtDNA copy number were increased.Conclusion Long-term application of NMN can restore the level of NAD+in heart,reduced mitochondrial damage and ultimately improving the heart function of old mice.