Those with insulin resistance often display increased circulating branched-chain amino acids (BCAA), which has been largely attributable to reduced BCAA catabolic capacity. Metabolic stimuli such as exercise activates AMP-activated kinase (AMPK), which promotes the metabolism of BCAA and induction/activation of BCAA catabolic enzymes. Though much attention has been paid to BCAA catabolic machinery, few studies have assessed the effect of AMPK activation on the predominant BCAA transporter, L-type amino acid transporter 1 (LAT1). This study assessed the effect of AMPK activation on LAT1 expression via common chemical AMPK activators in a cell model of skeletal muscle. C2C12 myotubes were treated with either 1 mM AICAR, 1 mM Metformin, or filter-sterilized water (control) for 24 h with either low- (5 mM) or high-glucose (25 mM) media. LAT1 and pAMPK protein content were measured via western blot. BCAA media content was measured using liquid chromatography-mass spectrometry. AICAR treatment significantly increased pAMPK and reduced LAT1 expression. Collectively, pAMPK and LAT1 displayed a significant inverse relationship independent of glucose levels. During low-glucose experiments, AICAR-treated cells had higher BCAA media content compared to other groups, and an inverse relationship between LAT1 and BCAA media content was observed, however, these effects were not consistently observed during high-glucose conditions. Further investigation with AICAR with and without concurrent LAT1 inhibition (via JPH203) also revealed reduced BCAA utilization in AICAR-treated cells regardless of LAT1 inhibition (which also independently reduced BCAA utilization). pAMPK activation via AICAR (but not Metformin) may reduce LAT1 expression and BCAA uptake in a glucose-dependent manner.

患有胰岛素抵抗的人通常表现出循环支链氨基酸 (BCAA) 增加，这很大程度上归因于 BCAA 分解代谢能力降低。运动等代谢刺激会激活 AMP 激活激酶 (AMPK)，从而促进 BCAA 的代谢以及 BCAA 分解代谢酶的诱导/激活。尽管 BCAA 分解代谢机制受到广泛关注，但很少有研究评估 AMPK 激活对主要 BCAA 转运蛋白 L 型氨基酸转运蛋白 1 (LAT1) 的影响。本研究通过骨骼肌细胞模型中常见的化学 AMPK 激活剂评估了 AMPK 激活对 LAT1 表达的影响。 C2C12 肌管用 1 mM AICAR、1 mM 二甲双胍或过滤灭菌水（对照）以及低（5 mM）或高葡萄糖（25 mM）培养基处理 24 小时。通过蛋白质印迹测量 LAT1 和 pAMPK 蛋白含量。使用液相色谱-质谱法测量BCAA培养基含量。 AICAR 处理显着增加 pAMPK 并减少 LAT1 表达。总的来说，pAMPK 和 LAT1 显示出显着的负相关关系，与葡萄糖水平无关。在低葡萄糖实验中，与其他组相比，AICAR 处理的细胞具有更高的 BCAA 培养基含量，并且观察到 LAT1 和 BCAA 培养基含量之间呈负相关，然而，在高葡萄糖条件下并没有一致地观察到这些效应。对同时抑制 LAT1 和不抑制 LAT1 的 AICAR 进行的进一步研究（通过 JPH203）也显示，无论 LAT1 抑制如何，AICAR 处理的细胞中 BCAA 的利用率都会降低（这也独立地降低了 BCAA 的利用率）。通过 AICAR（但不是二甲双胍）激活 pAMPK 可能会以葡萄糖依赖性方式减少 LAT1 表达和 BCAA 摄取。