Abstract：
BACKGROUND: LDL receptor-related protein-1 (LRP1) is a cell-surface receptor that functions in diverse physiological pathways. We previously demonstrated that hepatocyte-specific LRP1 deficiency (hLRP1KO) promotes diet-induced insulin resistance and increases hepatic gluconeogenesis in mice. However, it remains unclear whether LRP1 regulates hepatic glycogenesis.
METHODS: Insulin signaling, glycogenic gene expression, and glycogen content were assessed in mice and HepG2 cells. The pcDNA 3.1 plasmid and adeno-associated virus serotype 8 vector (AAV8) were used to overexpress the truncated β-chain (β∆) of LRP1 both in vitro and in vivo.
RESULTS: On a normal chow diet, hLRP1KO mice exhibited impaired insulin signaling and decreased glycogen content. Moreover, LRP1 expression in HepG2 cells was significantly repressed by palmitate in a dose- and time-dependent manner. Both LRP1 knockdown and palmitate treatment led to reduced phosphorylation of Akt and GSK3β, increased levels of phosphorylated glycogen synthase (GYS), and diminished glycogen synthesis in insulin-stimulated HepG2 cells, which was restored by exogenous expression of the β∆-chain. By contrast, AAV8-mediated hepatic β∆-chain overexpression significantly improved the insulin signaling pathway, thus activating glycogenesis and enhancing glycogen storage in the livers of high-fat diet (HFD)-fed mice.
CONCLUSIONS: Our data revealed that LRP1, especially its β-chain, facilitates hepatic glycogenesis by improving the insulin signaling pathway, suggesting a new therapeutic strategy for hepatic insulin resistance-related diseases.
METHODS: Insulin signaling, glycogenic gene expression, and glycogen content were assessed in mice and HepG2 cells. The pcDNA 3.1 plasmid and adeno-associated virus serotype 8 vector (AAV8) were used to overexpress the truncated β-chain (β∆) of LRP1 both in vitro and in vivo.
RESULTS: On a normal chow diet, hLRP1KO mice exhibited impaired insulin signaling and decreased glycogen content. Moreover, LRP1 expression in HepG2 cells was significantly repressed by palmitate in a dose- and time-dependent manner. Both LRP1 knockdown and palmitate treatment led to reduced phosphorylation of Akt and GSK3β, increased levels of phosphorylated glycogen synthase (GYS), and diminished glycogen synthesis in insulin-stimulated HepG2 cells, which was restored by exogenous expression of the β∆-chain. By contrast, AAV8-mediated hepatic β∆-chain overexpression significantly improved the insulin signaling pathway, thus activating glycogenesis and enhancing glycogen storage in the livers of high-fat diet (HFD)-fed mice.
CONCLUSIONS: Our data revealed that LRP1, especially its β-chain, facilitates hepatic glycogenesis by improving the insulin signaling pathway, suggesting a new therapeutic strategy for hepatic insulin resistance-related diseases.
摘要：
背景：LDL受体相关蛋白1（LRP1）是一种细胞表面受体，在多种生理途径中起作用。我们先前证明肝细胞特异性LRP1缺乏症（hLRP1KO）可促进饮食诱导的胰岛素抵抗并增加小鼠的肝糖异生。然而,目前尚不清楚LRP1是否调节肝糖原.
方法：胰岛素信号，糖原基因表达，在小鼠和HepG2细胞中评估糖原含量。pcDNA3.1质粒和腺相关病毒血清型8载体（AAV8）用于在体外和体内过表达LRP1的截短的β链（βΔ）。
结果：在正常饮食中，hLRP1KO小鼠表现出胰岛素信号受损和糖原含量降低。此外，棕榈酸酯以剂量和时间依赖性方式显著抑制HepG2细胞中的LRP1表达。LRP1敲低和棕榈酸盐处理均导致Akt和GSK3β磷酸化降低，磷酸化糖原合酶（GYS）水平升高，胰岛素刺激的HepG2细胞糖原合成减少，通过外源表达βΔ链恢复。相比之下,AAV8介导的肝βκ链过表达显著改善了胰岛素信号通路，从而激活高脂饮食（HFD）喂养的小鼠肝脏中的糖原生成并增强糖原储存。
结论：我们的数据显示LRP1，尤其是其β链，通过改善胰岛素信号通路促进肝糖原，提示肝脏胰岛素抵抗相关疾病的新治疗策略。
方法：胰岛素信号，糖原基因表达，在小鼠和HepG2细胞中评估糖原含量。pcDNA3.1质粒和腺相关病毒血清型8载体（AAV8）用于在体外和体内过表达LRP1的截短的β链（βΔ）。
结果：在正常饮食中，hLRP1KO小鼠表现出胰岛素信号受损和糖原含量降低。此外，棕榈酸酯以剂量和时间依赖性方式显著抑制HepG2细胞中的LRP1表达。LRP1敲低和棕榈酸盐处理均导致Akt和GSK3β磷酸化降低，磷酸化糖原合酶（GYS）水平升高，胰岛素刺激的HepG2细胞糖原合成减少，通过外源表达βΔ链恢复。相比之下,AAV8介导的肝βκ链过表达显著改善了胰岛素信号通路，从而激活高脂饮食（HFD）喂养的小鼠肝脏中的糖原生成并增强糖原储存。
结论：我们的数据显示LRP1，尤其是其β链，通过改善胰岛素信号通路促进肝糖原，提示肝脏胰岛素抵抗相关疾病的新治疗策略。
