Glucose metabolism through the hexosamine biosynthetic pathway drives hepatic de novo lipogenesis via promoting N-linked protein glycosylation.

IF 3.9 3区 医学 Q1 GASTROENTEROLOGY & HEPATOLOGY
Yanhui Li, Qing Song, Rui Guo, Yanyu Qian, Yuwei Jiang, Zhenyuan Song
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引用次数: 0

Abstract

De novo lipogenesis (DNL) converts excess glucose into lipids, whereas the hexosamine biosynthetic pathway (HBP), a glycolytic branch, generates UDP-N-acetylglucosamine for protein glycosylation, including O-GlcNAcylation and N-linked glycosylation. Both pathways are active in hepatocytes and integral to glucose metabolism; however, their functional interplay remains unclear. Here, we investigated the role of HBP in hepatic DNL activation using both in vitro and in vivo models. AML12 hepatocytes were cultured in low- and high-glucose media with or without HBP blockade, both pharmacologically and genetically. For in vivo studies, male C57BL/6J mice were subjected to a fasting-refeeding regimen with or without intraperitoneal administration of azaserine, a competitive inhibitor of glutamine-fructose-6-phosphate transaminase 1 (GFPT1), the rate-limiting enzyme of the HBP. Our results demonstrated that, in AML12 cells, glucose exposure activated both DNL and HBP, leading to triacylglycerol (TAG) accumulation, whereas HBP inhibition ameliorated DNL and TAG accumulation. In mice, refeeding after a 24-h fasting induced hepatic DNL, which was abolished by HBP inhibition, indicating its mechanistic involvement in glucose-driven lipogenesis. Mechanistically, we identified ATF4 as a key regulator of GFPT1 upregulation under high-glucose conditions. As expected, both glucose-treated hepatocytes and livers from fasting-refed mice exhibited increased protein glycosylation. Notably, blocking N-linked glycosylation, but not O-GlcNAcylation, abolished glucose-induced DNL activation, indicating that HBP is essential for glucose-induced DNL pathway activation via promoting N-linked glycosylation, independent of O-GlcNAcylation. In conclusion, our findings establish that an intact HBP is required for glucose-induced hepatic DNL activation, primarily through promoting protein N-linked glycosylation.NEW & NOTEWORTHY High-glucose exposure activates both hepatic HBP and DNL pathways. The glucose metabolism into HBP is essential for the activation of the DNL pathway. ATF4 activation plays a mechanistic role in high glucose-induced HBP activation. HBP drives high glucose-induced hepatic DNL activation via promoting N-linked protein glycosylation.

葡萄糖代谢通过己糖胺生物合成途径通过促进n -连接蛋白糖基化驱动肝脏从头脂肪生成。
De novo lipogenesis (DNL)将多余的葡萄糖转化为脂质,而糖酵解分支己糖胺生物合成途径(HBP)生成udp - n -乙酰氨基葡萄糖(UDP-GlcNAc)用于蛋白质糖基化,包括o - glcn酰化和n -链糖基化。这两种途径在肝细胞中都很活跃,是葡萄糖代谢的组成部分;然而,它们在功能上的相互作用尚不清楚。在这里,我们通过体外和体内模型研究了HBP在肝脏DNL激活中的作用。AML12肝细胞在有或没有HBP阻断的低糖和高糖培养基中培养,从药理学和遗传学上都是如此。在体内研究中,雄性C57BL/6J小鼠接受空腹-再喂养方案,有或没有腹腔注射azaserine, azaserine是谷氨酰胺-果糖-6-磷酸转氨酶1 (GFPT1)的竞争性抑制剂,是HBP的限速酶。我们的研究结果表明,在AML12细胞中,葡萄糖暴露激活了DNL和HBP,导致三酰甘油(TAG)的积累,而抑制HBP可改善DNL和TAG的积累。在小鼠中,禁食24小时后再进食诱导肝脏DNL,而HBP抑制会消除DNL,表明其参与葡萄糖驱动的脂肪生成的机制。在机制上,我们发现ATF4是高糖条件下GFPT1上调的关键调节因子。正如预期的那样,葡萄糖处理的肝细胞和禁食小鼠的肝脏都表现出增加的蛋白质糖基化。值得注意的是,阻断n -链糖基化而不是o - glcn酰化,可以消除葡萄糖诱导的DNL激活,这表明HBP通过促进n -链糖基化而独立于o - glcn酰化,对葡萄糖诱导的DNL通路激活至关重要。总之,我们的研究结果表明,葡萄糖诱导的肝脏DNL激活需要一个完整的HBP,主要是通过促进蛋白n链糖基化。
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来源期刊
CiteScore
9.40
自引率
2.20%
发文量
104
审稿时长
1 months
期刊介绍: The American Journal of Physiology-Gastrointestinal and Liver Physiology publishes original articles pertaining to all aspects of research involving normal or abnormal function of the gastrointestinal tract, hepatobiliary system, and pancreas. Authors are encouraged to submit manuscripts dealing with growth and development, digestion, secretion, absorption, metabolism, and motility relative to these organs, as well as research reports dealing with immune and inflammatory processes and with neural, endocrine, and circulatory control mechanisms that affect these organs.
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