长非编码RNA Linc-RAM在Ageing导致的骨骼肌肌少症发生发展中的功能与分子机制

Demographic shifts in the population have meant that the number of older adults in society has expanded hugely. Sarcopenia, characterized as age-related quality and functional decline of skeletal muscle, is an important risk factor of disability and frailty among elderly population. Sarcopenia disease places a substantial burden on the ageing population, contributing ~10% of the disease burden in those over 60 years of age. In the field of geriatrics research, people are currently beginning to pay more attention to sarcopenia since the high morbidity with more than 30% among elderly population. It has been suggested that multiple causal factors contribute the pathogenesis and development of sarcopenia during ageing. Of them, muscle stem cells are functional declined with ageing and play important roles in sarcopenia. Our laboratory has been focused on the regulatory roles of myofiber-mediated metabolic niche on muscle stem cell functions in sarcopenia during ageing. We have recently identified a long noncoding RNA (Linc-RAM), specifically expressed in skeletal muscle, regulates myogenic differentiation and muscle metabolism. The aged Linc-RAM knockout mice exhibit sarcopenic phenotype, suggesting that Linc-RAM is a novel gene functionally involving skeletal muscle ageing. Therefore, the Linc-RAM knockout mice provide an animal model for investigating the molecular mechanism of the sarcopenia pathogenesis. The specific focus of the project is to investigate the regulatory roles of Linc-RAM-mediated muscle metabolism on sarcopenia. The findings from the proposed work will not only provide experimental evidence that long noncoding RNA functions in regulating sarcopenia, but also provide a rationale for developing intervention strategy against sarcopenia in the clinical settings.

全球步入老龄化社会。衰老引起的骨骼肌减少——肌少症（Sarcopenia）发病率高，60岁以上高达30%，严重降低老龄人群的生活质量，加重家庭和社会的养老负担。因此，尽管国内外关于肌少症的研究刚刚起步，却已成为目前老年医学研究热点之一。项目申请人团队主要研究方向是骨骼肌代谢微环境对骨骼肌干细胞功能的调控及其在肌少症发生发展中的作用机制，并鉴定了一个骨骼肌特异表达调控骨骼肌代谢的长非编码Linc-RAM，基因敲除老年小鼠表现为肌少症表型，提示Linc-RAM可能是新的骨骼肌组织衰老相关基因。本项目将通过系统鉴定Linc-RAM介导的骨骼肌代谢调控的分泌因子（包括细胞因子和代谢小分子），深入研究这些分泌因子对骨骼肌干细胞功能的调控及其在肌少症发生发展中的作用机制，最终为阐明长非编码RNA调节肌少症以及骨骼肌代谢调控的分泌因子的潜在临床应用提供有价值的科学数据。

项目负责人团队前期工作中，发现骨骼肌特异表达的长非编码RNA Linc-RAM调控骨骼肌代谢，Linc-RAM基因敲除小鼠具有肌少症病理表型。本项目的主要研究内容是：系统鉴定Linc-RAM介导的骨骼肌代谢调控的分泌因子、研究这些分泌因子对骨骼肌干细胞功能的调控作用；鉴定Linc-RAM结合蛋白，阐明其结合蛋白的功能及其分子机制。.本项目按计划完成预期目标，主要成果包括：利用系统的代谢表型分析，发现Linc-RAM通过调节骨骼肌代谢影响系统能量稳态；采用代谢组学和RNA-seq系统鉴定了Linc-RAM介导的骨骼肌分泌的代谢小分子，功能研究发现代谢小分子乙酰乙酸通过激活Mek-Erk-MEF2调节miR-133b/SRF轴调控骨骼肌干细胞增殖；鉴定了Linc-RAM结合蛋白，发现细胞质中Linc-RAM结合糖原磷酸化酶PYGM促进骨骼肌干细胞分化；细胞核中Linc-RAM结合蛋白MyoD，调控骨骼肌细胞分化的3D基因组结构。同时，还发现了另一个小分子非编码RNA miR-378调控骨骼肌代谢及其骨骼肌干细胞微环境，影响骨骼肌干细胞Pax7Hi亚群。本项目成果，将为非编码RNA调节骨骼肌代谢影响老年肌少症和潜在的临床应用提供有价值的科学数据。