3. Effects of MICT and HIIT on Glycolytic Metabolism in Skeletal Muscle of db/db Mice
(1) MICT and HIIT Increase Glycogen Content in Skeletal Muscle of db/db Mice
PAS staining images revealed that muscle fibers in the NC group were densely and uniformly stained with deep granules. In comparison, the DC group showed sparse and unevenly distributed dark purple glycogen granules within muscle fibers, indicating severe impairment in glycogen synthesis. After 10 weeks of exercise intervention, the HIIT group exhibited densely and uniformly stained muscle fibers, similar to the normal group morphology. The MICT group showed intermediate staining intensity, confirming its partial restorative effect. The glycogen content in muscle tissue was observed under a light microscope at 200x magnification, and the positive area for muscle glycogen was analyzed using ImageJ software. Compared to the NC group, the glycogen content in the DC group significantly decreased (P < 0.001). Compared to the DC group, both the MICT and HIIT groups showed a significant increase in glycogen content (P < 0.001). Compared to the MICT group, the HIIT group had a significantly higher glycogen content (P < 0.001).
(2) MICT and HIIT Improve Glycolytic Metabolic Indicators in Skeletal Muscle of db/db Mice
Compared to the NC group, the expression of GLUT4 protein in the DC group significantly decreased (P < 0.01). Compared to the DC group, both the MICT and HIIT groups showed a significant increase in GLUT4 protein expression (P < 0.001). Compared to the MICT group, the HIIT group had a significantly higher expression of GLUT4 protein (P < 0.001). Compared to the NC group, the activity of L-LDH enzyme in the DC group significantly increased (P < 0.001), while the activity of G6PDH significantly decreased (P < 0.001). Compared to the DC group, the MICT group showed a significant decrease in L-LDH enzyme activity (P < 0.05) and a significant increase in G6PDH enzyme activity (P < 0.001). The HIIT group also showed a significant decrease in L-LDH enzyme activity (P < 0.01) and a significant increase in G6PDH enzyme activity (P < 0.001). Compared to the MICT group, the HIIT group had a significantly lower L-LDH enzyme activity (P < 0.001) and a significantly higher G6PDH enzyme activity (P < 0.05).
