Swimming Differentially Affects T2DM-Induced Skeletal Muscle ER Stress and Mitochondrial Dysfunction Related to MAM

Purpose: Mitochondrial dysfunction and endoplasmic reticulum stress (ERS) are associated with metabolic diseases such as obesity and Type 2 diabetes mellitus (T2DM). Mitochondria and ER are connected via mitochondria-associated membranes (MAM) that are involved in glucose homeostasis and insulin resistance. We postulated that exercise might positively benefit T2DM-induced ER and mitochondrial dysfunction that might be associated with MAM.

Materials and methods: Mice were fed a high-fat diet and injected with streptozotocin (STZ) to create T2DM models. Glucose tolerance, mitochondrial quality, MAM quality, and ERS were investigated in diabetic mice after six weeks of swimming.

Results: Type 2 DM induced decreased MAM quantity, impaired mitochondrial quality, and deteriorated ERS in skeletal muscle that led to endoplasmic reticulum-associated degradation (ERAD). Swimming alleviated strong ERS caused by T2DM. Importantly, MAM quantity was positively associated with mitochondrial function and tended to negatively correlate with the ERS branch, ATF6. Moreover, both ATF6 branches of ERS and ERAD were positively associated with the pIRE1α branch of ERS.

Conclusion: Type 2 DM induced glucose intolerance, powerful ERS, and mitochondrial dysfunction associated with decreased amounts of MAM. Swimming improved glucose intolerance and selectively mitigated the ERS in skeletal muscle. Therefore, MAM quality and ATF6 might be novel and important targets for T2DM treatment. Endoplasmic reticulum stress might be an effective target of swimming to improve diabetes.