Irisin restores metabolic homeostasis in diabetic skeletal muscle via the metabolism-inflammation axis and alternative splicing modulation

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia, insulin resistance, and impaired insulin secretion. The high global prevalence of T2DM contributes significantly to worldwide morbidity and mortality. Irisin, an exercise-induced myokine, has been shown to modulate energy metabolism by regulating insulin action. However, the precise regulatory network of irisin, particularly concerning its interaction with the metabolism-inflammation axis and alternative splicing (AS) modulation, requires comprehensive evaluation and description. This study aimed to investigate the therapeutic effects of irisin on glucose and lipid metabolism and to elucidate its molecular regulatory mechanisms in T2DM utilizing a multi-omics approach. To investigate the interactions between irisin and T2DM, a high-fat diet (HFD) was used along with multiple, low-dose injections of streptozotocin (STZ) to create T2DM model in C57BL/6J mice. After five weeks, the mice were treated with irisin every other day. Fasting blood glucose (FBG) and fasting insulin (FINS) were measured using ELISA, and the homeostatic model assessment of insulin resistance (HOMA-IR) was calculated to evaluate insulin sensitivity. Lipid metabolism was assessed by determining total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C). RNA sequencing (RNA-seq) of skeletal muscle was performed to identify differentially expressed genes (DEGs) and regulated alternative splicing events (RASEs), followed by functional enrichment analysis. Then RT-qPCR was used for validation of the key DEGs found. Irisin treatment significantly ameliorated insulin resistance and dyslipidemia in T2DM mice ( P < 0.05). RNA-seq analysis identified 1169 DEGs between the model and control groups (727 upregulated, 442 downregulated), and 414 DEGs post-irisin treatment (202 upregulated, 212 downregulated), alongside 511 significant RASEs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that these DEGs and alternative splicing events (ASEs) were predominantly associated with metabolic and inflammatory pathways. Key DEGs, including Bdh1, Pdpr, Dglucy, Lrtm1, Ccl6, Cd163, Fcgr3, and Adamts5, were successfully validated via RT-qPCR. Irisin mitigates skeletal muscle insulin resistance in T2DM mice, potentially through coordinated regulation of the metabolism-inflammation axis and remodeling mRNA splicing patterns, indicating its potential as a therapeutic strategy for T2DM.