To investigate the effect and mechanism of neuromuscular electrical stimulation (NMES) at different frequencies in the prevention and treatment of ICU-acquired weakness (ICU-AW).

Eighty-eight healthy male C57BL/6 mice were randomly divided into 11 groups with 8 mice in each group. The specific groups were as follows: blank control group (C1) , tracheotomy + aseptic water infusion control group (C2), ICU-AW model group (ICU-AW), NMES 20 Hz group (ICU-AW-20), NMES 40Hz group (ICU-AW-40) , NMES 60 Hz group (ICU-AW-60), NMES 80 Hz group (ICU-AW-80), ICU model group + AMPK agonist group (ICU-AW-A), ICU model group + AMPK agonist control group (ICU-AW-V), ICU model group + AMPK inhibitor group (ICU-AW-40-C), and ICU model group+ AMPK inhibitor control group (ICU-AW-40-C). The limbs holding power and survival status of the mice were detected after operation. After 7 days, mice lung tissue and gastrocnemius specimens were collected, and pathological changes were observed by HE staining, and Western blot and qRT-PCR were applied to detect Atrogin-1 MuRF-1 expression in mice gastrocnemius.

When compared with C1 and C2, lung injury and gastrocnemius muscle atrophy were apparently noted, and the limbs holding power significantly reduced in ICU-AW (P<0.05). The mRNA and protein expressions of Atrogin-1 and MuRF-1 were significantly decreased in ICU-AW when compared to C1 and C2 (P<0.01 and P<0.05, respectively). There was a significant reduction of p-AMPK level in ICU-AW when compared with that in C2 (P<0.01). The mice in ICU-AW-A treated with A-769662, an agonist of AMPK, the gastrocnemius muscle atrophy improved, and the grasping power was significantly elevated and the level of mRNA and protein expressions of Atrogin-1 and MuRF-1 were significantly reduced (P<0.01, vs. ICU-AW-C). After NMSE treatment, the grasping power in ICU-AW-20, ICU-AW-40, and ICU-AW-60 was improved when compared with that in ICU-AW (P<0.05), the gastrocnemius muscle atrophy was improved, and Atrogin-1 and MuRF-1 protein and gene expression were significantly decreased(P<0.05). The muscle weakness in ICU-AW-40 alleviated most dramatically than any other groups (P<0.05, vs. ICU-AW-20 or ICU-AW-60 ). The mice was treated compound C or Compared with the control group, the grasping ability and gastrocnemius muscle atrophy were improved in ICU-AW-A group, and the protein and gene expression levels of Atrogin-1 and MuRF-1 were significantly decreased in ICU-AW-A group (P<0.01). Compound C, an AMPK inhibitor, significantly reversed the protective effect of NMES 40 Hz on ICU-AW (P<0.05, ICU-AW-40-C vs. ICU-AW-40-V).

Early intervention with 40 Hz NMES can significantly improve ARDS related ICU-AW skeletal muscle atrophy in mice, and the protective mechanism may be through the regulation of AMPK.