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烟酰胺腺嘌呤二核苷酸(NAD)是真核细胞中的一种重要的代谢氧化还原辅酶,它在各种生物过程中起关键作用,包括新陈代谢、衰老、细胞死亡、DNA 修复和表达[1-2]。NAD主要有3种生物合成途径,在哺乳动物中,补救途径是NAD的主要来源并且该途径只有两个步骤(图1)。NAD 在该途径中的合成速率主要由烟酰胺磷酸核糖基转移酶(Nampt)决定,该步骤首先将烟酰胺(NAM)和5-磷酸核糖基-1-焦磷酸(PRPP)转化为烟酰胺单核苷酸(NMN)。然后,在第二步中将NMN与ATP偶联并转化为NAD[3]。直接使用NMN可以弥补NAD的不足,因此NMN可以参与多种疾病的调节,如2型糖尿病、肥胖症、心力衰竭、神经再生和炎症等[4-8]。
溃疡性结肠炎是炎症性肠病的一种。近年来,其病因和发病机制的研究受到广泛关注[9-11]。目前治疗溃疡性结肠炎的手段主要是对症治疗,如抗感染药、糖皮质激素和免疫抑制剂等,但这些药物长期使用会带来很多不良反应[12-13]。NAD与多种炎症性疾病有关,如败血症和类风湿性关节炎[14-15]。此外,有报道显示,炎症性肠病患者结肠组织和血清中Nampt浓度升高,并将Nampt作为小儿炎症性肠病严重程度的标志物[16-17]。因此,作为NAD合成的中间重要产物NMN,也有可能对炎症性肠病产生一定作用。与此同时,目前有很多含有NMN的保健品问世,但是由于NMN参与调节的功能非常复杂,并且有研究表明NMN可以促进肿瘤的增殖等作用[18],因此,补充NMN并不一定对人体都有益。并且,NMN作为保健品需要长期服用,但对于一些患有如炎症性肠病的慢性病患者,评价其对于患者的安全性极其重要。
本研究主要考察NMN对DSS诱导的溃疡性结肠炎小鼠模型的作用。以评价NMN作为保健品是否适用于患有溃疡性结肠炎的患者。
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雄性C57小鼠(8周龄,上海西普尔-必凯实验动物有限公司),放于实验室适应2周后进行造模。按照之前的方法进行模型制备[19],将DSS(美国MP公司,分子量为36 000~50 000)溶于水中,至终浓度为3%,让小鼠自由饮用。
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将NMN[音芙医药科技(上海)有限公司]溶于生理盐水中,制备不同浓度的NMN溶液,将雄性C57小鼠分为6组,分别为生理盐水对照组,3、10、30、100、300 mg/kg NMN的不同剂量组。按照容积0.1 ml/10 g,通过灌胃(ig)和腹腔注射(ip)两种方式,从第1天开始给药,每天1次,直至实验观察结束。
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按照之前的评分标准进行评分[19],对体重下降程度、大便性状、血便情况分别进行评分,而后进行加和,计算总分数。具体评分标准见表1。
表 1 疾病评分
评分 体重下降(%) 大便性状 血便情况 0 无 正常 无 1 1~5 — — 2 5~10 半稀便 潜血 3 10~15 — — 4 ≥15 稀便 肉眼血便 注:“—”表示无此项评分。 -
小鼠处死后,取整个结肠部位,测量长度进行比较。而后将结肠下段部位组织用4%多聚甲醛固定24 h,然后包埋在石蜡中。准备厚度为4 μm的切片,按照之前的实验方法,进行HE染色[19]。
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本实验指标均为定量数据,数据以(
$\bar x \pm s$ )表示。两两比较采用t-test法进行,采用GraphPad Prism 7统计软件进行统计分析。
Effect of NMN on DSS induced ulcerative colitis in mice
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摘要:
目的 探究烟酰胺单核苷酸(NMN)对葡聚糖硫酸钠盐(DSS)诱导的溃疡性结肠炎小鼠模型的作用。 方法 采用DSS诱导溃疡性结肠炎小鼠模型评价NMN的作用。应用DSS对C57小鼠进行造模,给予NMN后观察模型小鼠的生存时间、体重、疾病评分(DAI)、结肠组织长度以及结肠组织切片病理学变化。 结果 NMN对模型小鼠的生存时间、体重、DAI、肠道形态学变化等无显著性改变。 结论 NMN对DSS诱导的溃疡性结肠炎小鼠无显著作用。 Abstract:Objective To investigate the effects of Nicotinamide mononucleotide (NMN) on ulcerative colitis induced by dextran sulfate sodium (DSS) in mice. Methods DSS-induced ulcerative colitis mice were used to evaluate the effects of NMN. After NMN administration, the survival time, weight, disease activity index (DAI), colon tissue length and pathological changes of colon tissue slices were observed. Results NMN did not cause significant changes in the survival time, weight, DAI, and intestinal morphology of ulcerative colitis mice. Conclusion NMN has no significant effect on DSS-induced ulcerative colitis mice. -
Key words:
- nicotinamide mononucleotide /
- ulcerative colitis
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表 1 疾病评分
评分 体重下降(%) 大便性状 血便情况 0 无 正常 无 1 1~5 — — 2 5~10 半稀便 潜血 3 10~15 — — 4 ≥15 稀便 肉眼血便 注:“—”表示无此项评分。 -
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