ATP1B4 as a candidate upstream regulator of muscle atrophy in diabetic sarcopenia via PI3K/AKT/mTOR-mediated autophagy

Objective

This study aimed to elucidate the regulatory role of the muscle-specific gene ATP1B4 in skeletal muscle metabolism and mitophagy in diabetic sarcopenia (DS) rats.

Methods

Differentially expressed genes were screened from the GEO dataset GSE7014, and ATP1B4 was identified as a candidate gene associated with DS. A DS rat model was established via high-fat diet feeding and streptozotocin injection. ATP1B4 expression was modulated through lentiviral overexpression or knockdown. Additionally, PI3K/AKT/mTOR pathway activators (SC79, leucine) and inhibitors (LY294002, MK-2206) were administered. Protein expression of ATP1B4, phosphorylated PI3K/AKT/mTOR components, and autophagy markers (LC3-II, DRP1, ATG9, MFN2) was assessed via Western blotting, immunohistochemistry, and immunofluorescence. Skeletal muscle function and structure were evaluated using behavioral tests (treadmill and inclined plane) and histopathological staining (H&E, Masson, PAS).

Results

Bioinformatic analysis of the GSE7014 dataset identified ATP1B4 as a skeletal muscle-related differentially expressed gene enriched in extracellular matrix and metabolic pathways. In DS rats, ATP1B4 expression was upregulated, coinciding with suppression of PI3K/AKT/mTOR signaling and activation of mitophagy markers (LC3-II, DRP1, ATG9). Overexpression of ATP1B4 exacerbated hyperglycemia, muscle atrophy, collagen accumulation, and glycogen deposition, while knockdown reversed these effects. Activation of the PI3K/AKT/mTOR pathway improved muscle function and histological architecture, normalized autophagy, and reduced pathological features. However, co-overexpression of ATP1B4 eliminated the protective effects of pathway activation. Conversely, dual intervention with ATP1B4 knockdown and PI3K activation restored skeletal muscle integrity and autophagy flux. Importantly, ATP1B4 expression remained unchanged following pathway modulation, supporting its unidirectional upstream regulatory role in DS.

Conclusion

ATP1B4 may aggravate diabetic sarcopenia by acting as an upstream suppressor of the PI3K/AKT/mTOR pathway.