Nicotinamide-N-methyltransferase regulates lipid metabolism via SAM and 1-methylnicotinamide in the AML12 hepatocyte cell line
Nicotinamide-N-methyltransferase regulates lipid metabolism via SAM and 1-methylnicotinamide in the AML12 hepatocyte cell line
复制标题
烟酰胺-N-甲基转移酶通过 SAM 和 1-甲基烟酰胺调节 AML12 肝细胞系中的脂质代谢
DOI：
10.1093/jb/mvad028
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Shinpei Kawaoka
中科院分区：
文献类型：
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作者：
Mayuko Yoda;Rin Mizuno;Yoshihiro Izumi;Masatomo Takahashi ;Takeshi Bamba;Shinpei Kawaoka
烟酰胺- n -甲基转移酶（NNMT）是一种消耗-腺苷基蛋氨酸（SAM）和烟酰胺（NAM）产生-腺苷基同型半胱氨酸（SAH）和1-甲基烟酰胺（MNAM）的酶。NNMT对这四种代谢物的数量调节有多大作用取决于NNMT是这些代谢物的主要消费者还是生产者，这在不同的细胞环境中是不同的。然而，NNMT是否在AML12肝细胞系中对这些代谢物进行了关键调控还未被探索。为了解决这个问题，我们敲低了nnmtrnai在AML12细胞中的作用，并研究了nnmtrnai对代谢和基因表达的影响。我们发现nnmtrnai积累了SAM和SAH，而在NAM不变的情况下减少了MNAM。这些结果表明，NNMT是SAM的重要消耗者，对该细胞系中MNAM的产生至关重要。此外，转录组分析显示，SAM和MNAM稳态的改变伴随着各种有害的分子表型，如脂肪生成基因（如asSrebf1）的下调。与此一致的是，油重染色实验表明nnmtrnai后总中性脂减少。用SAM生物发生抑制剂环亮氨酸处理nnmtrnai AML12细胞，可抑制SAM积累并挽救中性脂质的减少。MNAM也显示出提高中性脂质的活性。这些结果表明，NNMT通过维持适当的SAM和MNAM稳态来促进脂质代谢。本研究提供了一个额外的例子，说明NNMT在调节SAM和MNAM代谢中起关键作用。
Nicotinamide-N-methyltransferase (NNMT) is an enzyme that consumesS-adenosyl-methionine (SAM) and nicotinamide (NAM) to produceS-adenosyl-homocysteine (SAH) and 1-methylnicotinamide (MNAM). How much NNMT contributes to the quantity regulation of these four metabolites depends on whether NNMT is a major consumer or producer of these metabolites, which varies among various cellular contexts. Yet, whether NNMT critically regulates these metabolites in the AML12 hepatocyte cell line has been unexplored. To address this, we knockdownNnmtin AML12 cells and investigate the effects ofNnmtRNAi on metabolism and gene expression. We find thatNnmtRNAi accumulates SAM and SAH, whereas it reduces MNAM with NAM being unaltered. These results indicate that NNMT is a significant consumer of SAM and critical for MNAM production in this cell line. Moreover, transcriptome analyses reveal that altered SAM and MNAM homeostasis is accompanied by various detrimental molecular phenotypes, as exemplified by the down-regulations of lipogenic genes, such asSrebf1. Consistent with this, oil-redO-staining experiments demonstrate the decrease of total neutral lipids uponNnmtRNAi. TreatingNnmtRNAi AML12 cells with cycloleucine, an inhibitor of SAM biogenesis suppresses SAM accumulation and rescues the decrease of neutral lipids. MNAM also shows activity to elevate neutral lipids. These results suggest that NNMT contributes to lipid metabolism by maintaining proper SAM and MNAM homeostasis. This study provides an additional example where NNMT plays a critical role in regulating SAM and MNAM metabolism.