膳食补充剂NMN：掉落凡间的“长生不老仙丹”？！
“长寿药”、“长生不老药”，甚至“不死药”……这些听起来就很厉害的称号都是网上对膳食补充剂NMN的描述。本以为太上老君的仙丹只是天界的一个传说，但听这架势，仙丹是化为NMN，下凡来咱人间走一遭了？
「极养视界」科普实验室 原创出品
文章｜Yu Shen MS
校稿｜Xinyin PHD, RD 编审｜Haoran PHD
编辑｜Jiaqi Xu BS, RD 设计｜Fay
阅读信息 📖
难度：★★☆☆☆ 类型：盘点 字数：3598
文章纲要
看NMN现原形
NMN抗衰的幕后“主使”
NMN让人“长生不老”是否成立？
官方对NMN的态度
平价替代有没有？
极养君有话说
极养视点
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小科普 >>> Sirtuins与DNA修复、抵抗氧化应激以及长寿相关的信号通路都有关联，也被称为长寿蛋白。
施用NMN可以快速提升小鼠组织内NAD+水平[8]，通过一年持续性的NMN补充后，小鼠体内的NAD+水平得到了提升；与年龄相关的体重增加得到了抑制；胰岛素敏感性、血脂、眼部功能以及骨密度都得到了改善，且未产生毒副作用[8]。
给老年老鼠施加NMN后，肌肉中一些由衰老引起的指标得到了改善，如线粒体功能改善、ATP合成增强、炎症减轻等[9]。
在线虫中，补充NMN改善了神经与肌肉功能并延长了线虫约10%的寿命[10]。
如上述所言，NMN的安全性及健康效用在小鼠及线虫体内得到了积极的验证，但要注意这些试验都为动物实验，NMN是否在人体中拥有相同的效用还需要临床试验的证明。
▲ 表二｜市场常见NMN补充剂对比表
从烟酸（NA）出发合成NAD+的Preiss-Handler途径； 从色氨酸出发的合成NAD+的从头合成途径（de novo pathway）； 将消耗NAD+所产生的副产物打捞起来，重新合成NAD+的补救途径（salvage pathway）（图一[13]），烟酰胺（NAM）、烟酰胺核糖（NR）以及NMN都是通过补救途径转化为NAD+。
▲ 图一｜NAD+合成途径
在考虑NAD+的各个前体时我们也不能忘记，NAD+的合成不是有了前体就万事大吉，任何前体转变为NAD+都需要酶的帮助。烟酰胺磷酸核糖转移酶（NAMPT）是NAD+合成的关键限速酶，许多研究都证明了锻炼以及热量限制可提升这种酶的表达，从而增加NAD+的生物合成以及SIRT1的活性[19]。而肥胖以及高热量饮食会限制NAMPT酶活，减少NAD+在体内的水平[4]。
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参考文献
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