Diabetic sarcopenia (DS) is a common and debilitating complication of diabetes mellitus (DM), marked by progressive skeletal muscle atrophy and functional impairment. This condition significantly elevates the risk of falls, disability, and mortality in diabetic patients (Yuan and Larsson, 2023). Epidemiological studies estimate that up to 24.5 % of individuals with diabetes suffer from sarcopenia, driven by multifactorial mechanisms including insulin resistance, chronic inflammation, and mitochondrial dysfunction (Duarte et al., 2024). Among these, disrupted skeletal muscle metabolism and imbalanced mitophagy have emerged as critical contributors to DS pathogenesis. However, the upstream molecular regulators that connect these processes via canonical signaling pathways remain poorly understood (Sebastián et al., 2024).

Mitophagy, the selective degradation of damaged mitochondria, plays a vital role in maintaining muscle integrity. While adequate mitophagy protects against muscle aging and dysfunction, excessive or dysregulated mitophagy can lead to mitochondrial loss and muscle wasting. Recent studies have shown that TP53INP2-mediated mitophagy can improve muscle quality and lifespan in aged mice (Sebastián et al., 2024), whereas heightened autophagic flux is linked to mitochondrial fragmentation and sarcopenia progression (Zdanowicz and Grosicka-Maciąg, 2024). These findings underscore the importance of mitophagy balance and the need to identify upstream regulators that influence this process.

The PI3K/AKT/mTOR signaling axis is not only central to metabolic regulation and muscle homeostasis but also plays a key role in cellular responses to oxidative and toxic stress. Impairments in PI3K/AKT/mTOR signaling have been associated with insulin resistance and increased mitophagic activity in diabetic muscle, contributing to structural and metabolic deterioration (Qin et al., 2021, Zhang et al., 2013, Giha et al., 2022). Toxicological studies also demonstrate that environmental stressors like arsenic and polystyrene microplastics can inhibit this pathway, inducing pathological autophagy and apoptosis. For example, arsenic exposure in common carp suppressed PI3K/AKT/mTOR signaling and elevated LC3-II expression in gut tissue—effects reversed by zinc supplementation (Guo et al., 2021). Similarly, in broilers, polystyrene microplastics inhibited this pathway via PTEN activation, resulting in autophagy and lung damage (Lu et al., 2023). These models highlight the pathway’s vulnerability to diverse stressors and its pivotal role in tissue degeneration.

Despite growing interest in PI3K/AKT/mTOR signaling, its upstream regulation in diabetic skeletal muscle remains largely unexplored. One potential modulator is ATP1B4, a muscle-specific β-subunit isoform of the Na⁺/K⁺-ATPase family. Originally considered a structural protein, ATP1B4 has been implicated in mitochondrial calcium handling, transcriptional regulation, and ion transport under stress (Bai et al., 2025, Pestov et al., 2011). It is also known to influence MyoD expression and skeletal muscle development, indicating a specialized role in muscle physiology (Ahmad et al., 2023). Yet, its function in adult muscle under diabetic conditions is not well defined.

Bioinformatic analysis revealed that ATP1B4 is significantly upregulated in diabetic skeletal muscle, suggesting a potential role in DS pathogenesis. Previous study proposed that ATP1B4 may influence muscle metabolism via the PI3K/AKT/mTOR pathway, although this hypothesis has not been experimentally validated (Lv et al., 2020). Additionally, ATP1B4 may interact with signaling regulators such as PPP1R3A, which is involved in glycogen metabolism and calcium signaling (Hu et al., 2023), further supporting its possible role in metabolic remodeling under diabetic conditions.

However, several critical knowledge gaps remain: the temporal expression pattern of ATP1B4 in diabetic muscle has not been defined; its impact on mitophagy and mitochondrial dynamics is unknown; and, most importantly, its regulatory relationship with the PI3K/AKT/mTOR pathway has not been confirmed in vivo.

Therefore, this study aimed to investigate whether ATP1B4 regulates skeletal muscle metabolism and mitophagy in DS via modulation of the PI3K/AKT/mTOR signaling pathway. ATP1B4 was selected based on bioinformatic screening as the only skeletal muscle–related differentially expressed gene (DEG) in diabetic tissue, with predicted links to metabolic and signaling pathways relevant to DS. We hypothesized that ATP1B4 acts as an upstream regulator of the PI3K/AKT/mTOR axis, contributing to autophagy dysregulation and muscle degeneration in DS.