The serine/threonine kinase AMP-activated protein kinase (AMPK) is a drug target for the treatment of obesity and type 2 diabetes (T2D). Metformin, a widely prescribed anti-hyperglycemic agent, and β-guanidinopropionic acid (β-GPA), a dietary supplement and creatine analog, have been shown to increase activity of AMPK. Macroautophagy is an intracellular degradation pathway for aggregated proteins and dysfunctional organelles, which can be mediated by AMPK. The present study sought to elucidate how metformin and β-GPA affect cell morphology, AMPK activity, autophagy and mitochondrial morphology and function in developing C2C12 myotubes. β-GPA reduced myotube diameter and increased length throughout differentiation, while metformin increased myotube diameter only at the 48 h time point. β-GPA treatment enhanced AMPK signaling and expression of autophagy-related proteins. β-GPA treatment also increased the density of autophagosomes, autolysosomes, and lysosomes. Metformin also increased activation of AMPK after 48 h, but in contrast to β-GPA, led to a dramatic reduction in the density of autophagosomes and lysosomes. Both metformin and β-GPA reduced the mitochondrial oxygen consumption rate, and differentially altered mitochondrial morphology. Obesity and T2D have been shown to increase mitochondrial dysfunction and reduce autophagic flux in skeletal muscle cells. Therefore, β-GPA may help to alleviate the effects of metabolic disease by increasing autophagic flux in skeletal muscle cells. In contrast, the reduction of autophagy by metformin may lead to dysregulation of mitochondrial maintenance, as well as muscle development.

丝氨酸/苏氨酸激酶 AMP 活化蛋白激酶 (AMPK) 是治疗肥胖症和 2 型糖尿病 (T2D) 的药物靶点。二甲双胍是一种广泛使用的抗高血糖药，β-胍基丙酸 (β-GPA) 是一种膳食补充剂和肌酸类似物，已被证明可以增加 AMPK 的活性。巨自噬是聚集蛋白和功能失调的细胞器的细胞内降解途径，可由 AMPK 介导。本研究试图阐明二甲双胍和 β-GPA 如何影响 C2C12 肌管发育过程中的细胞形态、AMPK 活性、自噬和线粒体形态和功能。β-GPA 在整个分化过程中降低了肌管直径并增加了长度，而二甲双胍仅在 48 小时时间点增加了肌管直径。β-GPA 处理增强了 AMPK 信号和自噬相关蛋白的表达。β-GPA 处理还增加了自噬体、自体溶酶体和溶酶体的密度。48 小时后，二甲双胍还增加了 AMPK 的活化，但与 β-GPA 相比，导致自噬体和溶酶体的密度显着降低。二甲双胍和 β-GPA 都降低了线粒体耗氧率，并不同程度地改变了线粒体形态。肥胖和 T2D 已被证明会增加线粒体功能障碍并减少骨骼肌细胞中的自噬通量。因此，β-GPA 可能通过增加骨骼肌细胞中的自噬通量来帮助减轻代谢疾病的影响。相反，二甲双胍降低自噬可能导致线粒体维持和肌肉发育失调。