Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Lo Ka Chung Research Centre for Natural Anti-Cancer Drug Development and State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Int J Mol Sci. 2023 May 28;24(11):9402. doi: 10.3390/ijms24119402.
Growing evidence proves that amino acid restriction can reverse obesity by reducing adipose tissue mass. Amino acids are not only the building blocks of proteins but also serve as signaling molecules in multiple biological pathways. The study of adipocytes' response to amino acid level changes is crucial. It has been reported that a low concentration of lysine suppresses lipid accumulation and transcription of several adipogenic genes in 3T3-L1 preadipocytes. However, the detailed lysine-deprivation-induced cellular transcriptomic changes and the altered pathways have yet to be fully studied. Here, using 3T3-L1 cells, we performed RNA sequencing on undifferentiated and differentiated cells, and differentiated cells under a lysine-free environment, and the data were subjected to KEGG enrichment. We found that the differentiation process of 3T3-L1 cells to adipocytes required the large-scale upregulation of metabolic pathways, mainly on the mitochondrial TCA cycle, oxidative phosphorylation, and downregulation of the lysosomal pathway. Single amino acid lysine depletion suppressed differentiation dose dependently. It disrupted the metabolism of cellular amino acids, which could be partially reflected in the changes in amino acid levels in the culture medium. It inhibited the mitochondria respiratory chain and upregulated the lysosomal pathway, which are essential for adipocyte differentiation. We also noticed that cellular interleukin 6 (IL6) expression and medium IL6 level were dramatically increased, which was one of the targets for suppressing adipogenesis induced by lysine depletion. Moreover, we showed that the depletion of some essential amino acids such as methionine and cystine could induce similar phenomena. This suggests that individual amino acid deprivation may share some common pathways. This descriptive study dissects the pathways for adipogenesis and how the cellular transcriptome was altered under lysine depletion.
越来越多的证据表明，通过减少脂肪组织质量，氨基酸限制可以逆转肥胖。氨基酸不仅是蛋白质的组成部分，而且在多种生物途径中充当信号分子。研究脂肪细胞对氨基酸水平变化的反应至关重要。据报道，低浓度的赖氨酸可抑制 3T3-L1 前脂肪细胞中脂质积累和几种脂肪生成基因的转录。然而，赖氨酸剥夺诱导的细胞转录组变化的详细情况和改变的途径尚未得到充分研究。在这里，我们使用 3T3-L1 细胞，对未分化和分化细胞以及赖氨酸缺乏环境下的分化细胞进行了 RNA 测序，并对数据进行了 KEGG 富集分析。我们发现，3T3-L1 细胞向脂肪细胞的分化过程需要代谢途径的大规模上调，主要是在线粒体 TCA 循环、氧化磷酸化和溶酶体途径下调。赖氨酸的单一氨基酸耗尽会依赖剂量抑制分化。它破坏了细胞氨基酸的代谢，这在培养基中氨基酸水平的变化中可以部分反映出来。它抑制了线粒体呼吸链并上调了溶酶体途径，这对脂肪细胞分化是必不可少的。我们还注意到细胞白细胞介素 6 (IL6) 的表达和培养基中 IL6 水平显著增加，这是赖氨酸缺乏诱导脂肪生成抑制的靶点之一。此外，我们还表明，像蛋氨酸和胱氨酸这样的一些必需氨基酸的耗尽也会引起类似的现象。这表明单个氨基酸的缺乏可能共享一些共同的途径。这项描述性研究剖析了脂肪生成的途径，以及在赖氨酸缺乏下细胞转录组是如何改变的。
