Distinct effects of exercise and SGLT2i therapy on mitochondrial quality control related proteins in gastrocnemius of a rat model

Mitochondrial dysfunction impairs the ability of highly metabolic tissues, such as skeletal muscle, to oxidize glucose and fatty acids. This contributes to insulin resistance and results in type 2 diabetes (T2D). Mitochondrial quality control, including fission, fusion, and mitophagy, is essential for maintaining function of mitochondria. We previously reported that exercise training (EX) and sodium-glucose cotransporter-2 inhibitor therapy (SGLT2i) independently improved glucose regulation in a rodent model of T2D. However, the effects of SGLT2i, EX, and their combination on mitochondrial quality control-related proteins in gastrocnemius remain unclear. Objective: To evaluate the effect of SGLT2i, EX, and their combination on mitochondrial quality control-related proteins in the gastrocnemius. Hypothesis: SGLT2i, EX, and their combination significantly affect expression of mitochondrial quality control proteins in the gastrocnemius when compared to glucose-intolerant animals. Methods: Hyperglycemia was induced in male Sprague Dawley rats using a combination of a low-dose streptozotocin (30 mg/kg) and a high-fat diet (45% kcal from fat). The rats were assigned to one of four groups: vehicle sedentary (VEH SED; n=10), vehicle exercise (VEH EX; n=7), SGLT2i sedentary (SGLT2i SED; n=10), and SGLT2i exercise (SGLT2i EX; n=7) and underwent treatments for 12 weeks. Rats in the SGLT2i groups received canagliflozin (3 mg/kg/day) via oral gavage in 0.5% methylcellulose. Exercise groups performed treadmill running 5 days per week for 60 minutes per session on a 10% incline, at approximately 50% of maximal running speed as determined by a VO2max test. Results: While SGLT2i did not affect fission-related proteins in the gastrocnemius, pro-fusion protein expression of MFN2 was three times higher and OPA1 was~97% higher; however, these did not reach significance (p=0.056, and p=0.14, respectively). EX did not affect the expression of any of the fission or fusion related proteins assessed. Although not significant, SGLT2i had ~16% lower expression of autophagy-related LC3B-I (p=0.058). EX had lower expression of autophagy-related BNIP3 (~85%) and mitophagy-related Pink1 (~20%) and Parkin (~12%), however these did not reach statistical significance (p=0.09, p=0.16, p=0.17, respectively). Combining therapies did not significantly affect the expression of fission proteins, fusion proteins, or autophagy/mitophagy proteins compared to the individual therapies alone (p>0.05). Conclusion: SGLT2i promoted the expression of mitochondrial fusion proteins. Additionally, each therapy individually showed a trend toward reduced autophagy/mitophagy protein expression compared to the glucose intolerance group. Restoration of whole-body metabolism with SGLT2i or exercise may have contributed to overall mitochondrial health, resulting in the observed differences in mitochondrial quality control proteins. These findings are preliminary, aimed at identifying whether chronic SGLT2i administration or exercise affects mitochondrial quality control-related proteins in a model of T2D, and further studies are needed to clarify its role in SGLT2i- and/or exercise-related health benefits. This work was supported by Pfizer Inc This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.