Transcriptomic analyses reveal rhythmic and CLOCK-driven pathways in human skeletal muscle

The circadian regulation of transcriptional processes has a broad impact on cell metabolism. Here, we compared the diurnal transcriptome of human skeletal muscle conducted on serial muscle biopsies in vivo with profiles of human skeletal myotubes synchronized in vitro. Extensive rhythmic transcription was observed in human skeletal muscle in comparison to in vitro cell culture. However, nearly half of the in vivo rhythmicity was lost at the mRNA accumulation level. siRNA-mediated clock disruption in primary myotubes significantly affected the expression of ~8% of all genes, with impact on glucose homeostasis and lipid metabolism. Genes involved in GLUT4 expression, translocation and recycling were negatively affected, whereas lipid metabolic genes were altered to promote activation of lipid utilization. Moreover, basal and insulin stimulated glucose uptake were significantly reduced upon CLOCK depletion. Altogether, our findings suggest an essential role for cell-autonomous circadian clocks in coordinating muscle glucose homeostasis and lipid metabolism in humans. 10 candidates with 6 biopsies each for a total of 57 samples being sequenced. Together with GSE109825, part of the same study described above.

转录过程的昼夜节律调控对细胞代谢具有广泛影响。本研究将基于体内连续肌肉活检获取的人骨骼肌日节律转录组，与体外同步化人骨骼肌肌管的转录谱进行了对比分析。相较于体外细胞培养模型，人体骨骼肌中可检测到大量节律性转录事件，但在mRNA积累水平上，近半数的体内节律性转录特征出现丢失。通过小干扰RNA（siRNA）介导的CLOCK基因敲低，原代肌管中约8%的全部基因的表达受到显著影响，且该影响波及葡萄糖稳态与脂质代谢通路。参与葡萄糖转运蛋白4（GLUT4）表达、转位与循环的基因受到负向调控，而脂质代谢相关基因的表达改变则可促进脂质利用的激活。此外，在CLOCK基因敲低后，基础状态及胰岛素刺激下的葡萄糖摄取水平均显著降低。综上，本研究结果表明，细胞自主性昼夜节律时钟在协调人体肌肉葡萄糖稳态与脂质代谢过程中发挥着不可或缺的关键作用。本研究共纳入10名候选受试者，每人接受6次肌肉活检，总计获取57个样本用于测序。该数据集与GSE109825同属于上述提及的同一研究项目。