NAD Blocks High Glucose Induced Mesangial Hypertrophy via Activation of the Sirtuins-AMPK-mTOR Pathway
NAD Blocks High Glucose Induced Mesangial Hypertrophy via Activation of the Sirtuins-AMPK-mTOR Pathway
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DOI：
10.1159/000330077
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发表时间：
2011-01-01
影响因子：
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通讯作者：
Cai, Guangyan
中科院分区：
文献类型：
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作者：
Zhuo, Li;Fu, Bo;Cai, Guangyan
背景/目的：自从NAD依赖的脱乙酰酶sirtuins被发现以来，人们已经认识到，维持细胞内NAD的水平对于管理细胞的应激反应至关重要。在这里，我们发现高糖(HG)诱导的系膜肥大与细胞内NAD水平的降低有关。本研究旨在探讨NAD对HG诱导的肾小球系膜肥大的影响。方法：用含或不含NAD的HG液培养大鼠肾小球系膜细胞。然后测定NAD(+)/NADH比值和sirtuins的酶活性。此外，对AMPK-mTOR信号的表达进行了Western印迹分析。结果：HG可诱导系膜细胞NAD(+)/NADH比值降低，SIRT1和SIRT3活性降低，系膜肥大，但NAD能维持细胞内NAD(+)/NADH比值和SIRT1和SIRT3活性，并能阻断HG诱导的系膜肥大。NAD激活sirtuins阻断了促肥厚性Akt信号的激活，增强了抗肥厚性AMPK信号的活性，从而阻止了随后mTOR介导的蛋白质合成。通过AMPK基因敲除，我们发现它上调了mTOR的磷酸化。在这种情况下，NAD抑制HG诱导的系膜肥厚，而NAD在AMPK siRNA存在下失去抑制作用。结论：这些结果揭示了NAD作为系膜肥大信号抑制因子的新作用，并提示防止NAD耗竭可能是治疗系膜肥厚的关键。版权所有(C)2011 S.Karger AG，巴塞尔
Background/aims-Since the discovery of NAD-dependent deacetylases, Sirtuins, it has been recognized that maintaining intracellular levels of NAD is crucial for the management of stress-response of cells. Here we show that high glucose(HG)-induced mesangial hypertrophy is associated with loss of intracellular levels of NAD. This study was designed to investigate the effect of NAD on HG-induced mesangial hypertrophy. Methods-The rat glomerular mesangial cells (MCs) were incubated in HG medium with or without NAD. Afterwards, NAD(+)/NADH ratio and enzyme activity of Sirtuins was determined. In addition, the expression analyses of AMPK-mTOR signaling were evaluated by Western blot analysis. Results-We showed that HG induced the NAD(+)/NADH ratio and the levels of SIRT1 and SIRT3 activity decreased as well as mesangial hypertrophy, but NAD was capable of maintaining intracellular NAD(+)/NADH ratio and levels of SIRT1 and SIRT3 activity as well as of blocking the HG-induced mesangial hypertrophy in vitro. Activating Sirtuins by NAD blocked the activation of pro-hypertrophic Akt signaling, and augmented the activity of the antihypertrophic AMPK signaling in MCs, which prevented the subsequent induction of mTOR-mediated protein synthesis. By AMPK knockdown, we showed it upregulated phosphorylation of mTOR. In such, the NAD inhibited HG-induced mesangial hypertrophy whereas NAD lost its inhibitory effect in the presence of AMPK siRNA. Conclusion-These results reveal a novel role of NAD as an inhibitor of mesangial hypertrophic signaling, and suggest that prevention of NAD depletion may be critical in the treatment of mesangial hypertrophy. Copyright (C) 2011 S. Karger AG, Basel