To compare the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on glucose metabolism in the skeletal muscle of T2DM mice, this study investigates the potential regulatory mechanisms of the MSTN-AMPK/PGC-1α signaling pathway on mitochondrial quality control and its relationship with glucose metabolism.
Data from the GEO database for 2-type diabetes mellitus (T2DM) patients' skeletal muscle were analyzed to identify potential molecular targets for improving skeletal muscle glucose metabolism through exercise intervention. Differential expression analysis was performed on datasets GSE205891 and GSE230002 to screen for differentially expressed genes (DEGs) and find their intersection. GO and KEGG enrichment analyses were conducted on the intersecting genes, and a protein-protein interaction (PPI) network was constructed to identify the top 10 key genes. The interactions between the proteins encoded by these genes were analyzed to find those at critical nodes, which could serve as potential molecular targets for improving skeletal muscle glucose metabolism through exercise intervention.
Thirty-six 8-week-old male db/db mice (diabetic model) and 12 age-matched db/m mice (normal control) were adaptively fed for one week. db/db mice with random blood glucose levels ≥ 16.6 mmol/L were randomly divided into three groups: DC group (no intervention), MICT group, and HIIT group (12 mice each). The db/m mice served as the NC group. After a one-week adaptation period, the maximum running speed (Vmax) was measured for the MICT and HIET groups. A 10-week exercise intervention (5 days per week) was then implemented: the HIIT group underwent 2 minutes of high-intensity training at 90% Vmax (with 2-minute rest intervals, repeated 10 times), while the MICT group performed continuous exercise at 70% Vmax (matching the total distance of the HIIT group). Both groups included 5 minutes of warm-up and cool-down activities. Vmax was re-measured every two weeks to dynamically adjust the exercise intensity. Body weight and random blood glucose levels were monitored weekly, and skeletal muscle tissue samples were collected at the end of the intervention.
Histological examination using HE and PAS staining was performed to observe the morphological structure and glycogen deposition in the skeletal muscle. Transmission electron microscopy was used to examine mitochondrial ultrastructure. Enzyme activity assays were conducted to measure L-LDH and G6PDH activity. Western blotting was used to detect the protein expression levels of GLUT4, MSTN, AMPK, P-AMPK, PGC-1α, NRF2, TFAM, OPA1, MFN2, DRP1, PINK1, and PARKIN. Real-time quantitative PCR was used to measure mitochondrial DNA copy number.
- Gene screening results for the improvement of skeletal muscle metabolism in T2DM patients through exercise: From datasets GSE205891 and GSE230002, 81 and 100 DEGs were identified, respectively, with 26 genes overlapping. GO enrichment analysis showed that the intersecting genes were significantly associated with biological processes such as skeletal muscle tissue development, cytokine response, and insulin response. KEGG pathway analysis revealed significant enrichment of the AMPK signaling pathway. The PPI network of intersecting genes identified MSTN among the top 10 hub genes. Given its significant metabolic regulatory role, MSTN was selected as a potential molecular target for exercise intervention in T2DM.
Both MICT and HIIT increased glycogen content in the skeletal muscle of db/db mice: PAS staining images showed dense, uniformly deep purple granules in the muscle fibers of the NC group. In contrast, the DC group had sparse and unevenly distributed deep purple glycogen granules within the muscle fibers. The HIIT group exhibited dense, uniformly deep-stained granules, similar to the normal group. The MICT group showed intermediate staining intensity. Statistical analysis revealed that the glycogen content in the DC group was significantly lower than in the NC group (P < 0.001). Compared to the DC group, both the MICT and HIIT groups showed significantly increased glycogen content (P < 0.001). Additionally, the HIIT group had significantly higher glycogen content compared to the MICT group (P < 0.001).
