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.
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。