Institute for Health and Sport, Victoria University, Melbourne, Australia.
Centre for Muscle Research, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Australia.
Exp Physiol. 2024 Nov;109(11):1909-1921. doi: 10.1113/EP091962. Epub 2024 Sep 2.
In muscle, digoxin inhibits Na,K-ATPase (NKA) whereas acute exercise can increase NKA gene expression, consistent with training-induced increased NKA content. We investigated whether oral digoxin increased NKA isoform mRNA expression (qPCR) in muscle at rest, during and post-exercise in 10 healthy adults, who received digoxin (DIG, 0.25 mg per day) or placebo (CON) for 14 days, in a randomised, double-blind and cross-over design. Muscle was biopsied at rest, after cycling 20 min (10 min each at 33%, then 67% ), then to fatigue at 90% and 3 h post-exercise. No differences were found between DIG and CON for NKA α or β isoform mRNA. Both α (354%, P = 0.001) and β mRNA (P = 0.008) were increased 3 h post-exercise, with α and β mRNA unchanged, whilst α mRNA declined at fatigue (-43%, P = 0.045). In resting muscle, total β mRNA (∑(β+β+β)) increased in DIG (60%, P = 0.025) and also when transcripts for each isoform were normalised to CON then either summed (P = 0.030) or pooled (n = 30, P = 0.034). In contrast, total α mRNA (∑(α+α+α), P = 0.348), normalised then summed (P = 0.332), or pooled transcripts (n = 30, P = 0.717) did not differ with DIG. At rest, NKA α and β protein abundances were unchanged by DIG. Post-exercise, α and β proteins were unchanged, but α declined at 3 h (19%, P = 0.020). In conclusion, digoxin did not modify gene expression of individual NKA isoforms at rest or with exercise, indicating NKA gene expression was maintained consistent with protein abundances. However, elevated resting muscle total β mRNA with digoxin suggests a possible underlying β gene-stimulatory effect. HIGHLIGHTS: What is the central question of this study? Na,K-ATPase (NKA) in muscle is important for Na/K homeostasis. We investigated whether the NKA-inhibitor digoxin stimulates increased NKA gene expression in muscle and exacerbates NKA gene responses to exercise in healthy adults. What is the main finding and its importance? Digoxin did not modify exercise effects on muscle NKA α and β gene transcripts, which comprised increased post-exercise α and β mRNA and reduced α mRNA during exercise. However, in resting muscle, digoxin increased NKA total β isoform mRNA expression. Despite inhibitory-digoxin or acute exercise stressors, NKA gene regulation in muscle is consistent with the maintenance of NKA protein contents.
在肌肉中，地高辛抑制钠钾-ATP 酶（NKA），而急性运动可以增加 NKA 基因表达，与训练诱导的 NKA 含量增加一致。我们研究了在 10 名健康成年人中，口服地高辛（DIG，每天 0.25 毫克）或安慰剂（CON）14 天后，地高辛是否会在休息时、运动中和运动后增加肌肉中的 NKA 同工型 mRNA 表达（qPCR），采用随机、双盲和交叉设计。在休息时、骑自行车 20 分钟（每次 33%，然后 67%，然后疲劳）后、运动后 90%和 3 小时后，肌肉活检。DIG 和 CON 之间，NKAα或β同工型 mRNA 没有差异。α（354%，P=0.001）和βmRNA（P=0.008）均在运动后 3 小时增加，而α和βmRNA不变，而αmRNA在疲劳时下降（-43%，P=0.045）。在休息时，DIG 增加了总βmRNA（∑（β+β+β））（60%，P=0.025），当每个同工型的转录物与 CON 正常化，然后分别求和（P=0.030）或合并（n=30，P=0.034）时，也增加了总βmRNA。相比之下，DIG 没有改变总αmRNA（∑（α+α+α），P=0.348）、求和（P=0.332）或合并转录物（n=30，P=0.717）。休息时，DIG 对地高辛 α和β蛋白丰度没有影响。运动后，α和β蛋白没有变化，但在 3 小时时下降（19%，P=0.020）。总之，地高辛在休息或运动时没有改变单个 NKA 同工型的基因表达，表明 NKA 基因表达与蛋白丰度一致。然而，地高辛在休息时增加了肌肉总β mRNA，这表明可能存在β基因刺激作用。
这个研究的中心问题是什么？
肌肉中的钠钾-ATP 酶（NKA）对钠钾稳态很重要。我们研究了 NKA 抑制剂地高辛是否会刺激健康成年人肌肉中增加的 NKA 基因表达，并加剧运动对 NKA 基因的影响。
主要发现及其重要性是什么？
地高辛没有改变运动对肌肉 NKAα和β基因转录物的影响，这包括运动后增加的α和β mRNA 和运动期间减少的α mRNA。然而，在休息时，地高辛增加了 NKA 总β同工型 mRNA 表达。尽管存在抑制性地高辛或急性运动应激源，肌肉中的 NKA 基因调节与 NKA 蛋白含量的维持一致。
