目的:细胞外基质(ECM)稳态在脂肪组织的代谢可塑性和内分泌功能中起着至关重要的作用。高水平的细胞内内毒素,VI型胶原α3链(Col6a3)的切割肽,在肥胖和糖尿病的脂肪细胞中经常观察到。然而,内毒素是如何在细胞内流通和影响脂肪细胞代谢稳态的,目前尚不清楚.因此,我们的目的是研究脂肪细胞内内毒素的运输及其代谢效应,这取决于瘦或肥胖状况。
方法:我们使用多西环素诱导的脂肪细胞特异性内毒素过表达小鼠进行功能获得研究,使用基于CRISPR-Cas9系统的Col6a3缺陷小鼠进行功能丧失研究。采用各种分子和生化技术来检查内毒素对代谢参数的影响。
结果:在肥胖期间的脂肪细胞中,大多数内体内毒素逃避溶酶体降解,并释放到细胞质中,以介导SEC13之间的直接相互作用,SEC13是外壳蛋白复合物II(COPII)囊泡的主要成分,和自噬相关7(ATG7),导致自噬体形成增加。自噬体的积累破坏了自噬通量的平衡,导致脂肪细胞死亡,炎症,和胰岛素抵抗。通过用siRNA离体抑制ATG7或用单克隆抗体在体内中和内毒素来改善这些不利的代谢作用。
结论:在脂肪细胞中高水平的细胞内内毒素介导的自噬通量损伤有助于代谢功能障碍,如细胞凋亡,炎症,肥胖患者的胰岛素抵抗.
Extracellular matrix (ECM) homeostasis plays a crucial role in metabolic plasticity and endocrine function of adipose tissue. High levels of intracellular endotrophin, a cleavage peptide of type VI collagen alpha 3 chain (Col6a3), have been frequently observed in adipocyte in obesity and diabetes. However, how endotrophin intracellularly traffics and influences metabolic homeostasis in adipocyte remains unknown. Therefore, we aimed to investigate the trafficking of endotrophin and its metabolic effects in adipocytes depending on lean or obese condition.
We used doxycycline-inducible adipocyte-specific endotrophin overexpressed mice for a gain-of-function study and CRISPR-Cas9 system-based Col6a3-deficient mice for a loss-of-function study. Various molecular and biochemical techniques were employed to examine the effects of endotrophin on metabolic parameters.
In adipocytes during obesity, the majority of endosomal endotrophin escapes lysosomal degradation and is released into the cytosol to mediate direct interactions between SEC13, a major component of coat protein complex II (COPII) vesicles, and autophagy-related 7 (ATG7), leading to the increased formation of autophagosomes. Autophagosome accumulation disrupts the balance of autophagic flux, resulting in adipocyte death, inflammation, and insulin resistance. These adverse metabolic effects were ameliorated by either suppressing ATG7 with siRNA ex vivo or neutralizing endotrophin with monoclonal antibodies in vivo.
High levels of intracellular endotrophin-mediated autophagic flux impairment in adipocyte contribute to metabolic dysfunction such as apoptosis, inflammation, and insulin resistance in obesity.