Objective

Physical exercise training is associated with increased glucose uptake in skeletal muscle and improved glycemic control. HDAC5, a class IIa histone deacetylase, has been shown to regulate transcription of the insulin-responsive glucose transporter GLUT4 in cultured muscle cells. In this study, we analyzed the contribution of HDAC5 to the transcriptional network in muscle and the beneficial effect of muscle contraction and regular exercise on glucose metabolism.

Methods

HDAC5 knockout mice (KO) and wild-type (WT) littermates were trained for 8 weeks on treadmills, metabolically phenotyped, and compared to sedentary controls. Hdac5-deficient skeletal muscle and cultured Hdac5-knockdown (KD) C2C12 myotubes were utilized for studies of gene expression and glucose metabolism. Chromatin immunoprecipitation (ChIP) studies were conducted to analyze Il6 promoter activity using H3K9ac and HDAC5 antibodies.

Results

Global transcriptome analysis of Hdac5 KO gastrocnemius muscle demonstrated activation of the IL-6 signaling pathway. Accordingly, knockdown of Hdac5 in C2C12 myotubes led to higher expression and secretion of IL-6 with enhanced insulin-stimulated activation of AKT that was reversed by Il6 knockdown. Moreover, Hdac5-deficient myotubes exhibited enhanced glucose uptake, glycogen synthesis, and elevated expression levels of the glucose transporter GLUT4. Transcription of Il6 was further enhanced by electrical pulse stimulation in Hdac5-deficient C2C12 myotubes. ChIP identified a ∼1 kb fragment of the Il6 promoter that interacts with HDAC5 and demonstrated increased activation-associated histone marker AcH3K9 in Hdac5-deficient muscle cells. Exercise intervention of HDAC5 KO mice resulted in improved systemic glucose tolerance as compared to WT controls.

Conclusions

We identified HDAC5 as a negative epigenetic regulator of IL-6 synthesis and release in skeletal muscle. HDAC5 may exert beneficial effects through two different mechanisms, transcriptional control of genes required for glucose disposal and utilization, and HDAC5-dependent IL-6 signaling cross-talk to improve glucose uptake in muscle in response to exercise.

中文翻译：

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组蛋白脱乙酰酶 5 调节骨骼肌中白细胞介素 6 的分泌和胰岛素作用。

客观的

体育锻炼与骨骼肌葡萄糖摄取增加和血糖控制改善有关。HDAC5 是一种 IIa 类组蛋白脱乙酰酶，已被证明可以调节培养的肌肉细胞中胰岛素响应性葡萄糖转运蛋白 GLUT4 的转录。在这项研究中，我们分析了 HDAC5 对肌肉转录网络的贡献以及肌肉收缩和定期运动对葡萄糖代谢的有益影响。

方法

HDAC5 敲除小鼠 (KO) 和野生型 (WT) 同窝小鼠在跑步机上训练 8 周，进行代谢表型分析，并与久坐的对照组进行比较。Hdac5缺陷的骨骼肌和培养的Hdac5敲低 (KD) C2C12 肌管用于基因表达和葡萄糖代谢的研究。使用 H3K9ac 和 HDAC5 抗体进行染色质免疫沉淀 (ChIP) 研究来分析Il6启动子活性。

结果

Hdac5 KO 腓肠肌的整体转录组分析表明 IL-6 信号通路被激活。因此， C2C12 肌管中Hdac5的敲低导致 IL-6 的表达和分泌增加，同时胰岛素刺激的 AKT 激活增强，而IL6敲低可逆转这一现象。此外，Hdac5缺陷的肌管表现出增强的葡萄糖摄取、糖原合成以及葡萄糖转运蛋白GLUT4的表达水平升高。在Hdac5缺陷的 C2C12 肌管中电脉冲刺激进一步增强了Il6的转录。ChIP 鉴定了与 HDAC5 相互作用的Il6启动子的~1 kb 片段，并证明在Hdac5缺陷的肌肉细胞中激活相关的组蛋白标记 AcH3K9 增加。与 WT 对照相比，HDAC5 KO 小鼠的运动干预导致全身葡萄糖耐量改善。

结论

我们确定 HDAC5 是骨骼肌中 IL-6 合成和释放的负表观遗传调节因子。HDAC5 可能通过两种不同的机制发挥有益作用：葡萄糖处理和利用所需基因的转录控制，以及 HDAC5 依赖性 IL-6 信号串扰以改善运动时肌肉中的葡萄糖摄取。