Exercise-induced FKBP8-mediated Mitophagy Via AMPK Activation In Soleus Muscle Of Rats

Abstract

Scientific Abstract PURPOSE: To investigate the effects of downhill running on mitochondrial structure/function and expression levels of mitophagy-related proteins in rat skeletal muscle, and whether AMP-activated protein kinase (AMPK) plays a regulatory role in this context. METHODS: Male Sprague-Dawley rats were divided into a control (C, n = 8) or an exercise (E, n = 56) group. Rats in the E group were exercised on a treadmill down a 16° incline at 16 m/min for 90 min, and were further divided into 0 h (E0), 12 h (E12), 24 h (E24), 48 h (E48) and 72 h (E72) post-exercise sub-groups. Rats in the E0 and E12 sub-groups received acute AMPK agonist AICAR treatment (500 mg/kg via I.P.) or saline (n = 8 each) 30 min before exercise. At each time point the soleus muscle was collected under full anesthesia. Mitochondrial ultrastructural changes in skeletal muscle were observed by using a transmission electron microscope. Protein expression levels of skeletal muscle p-AMPKα1/2(T172), total AMPKα, heat shock protein 60 (HSP60), cyclophilin D (CypD), mitochondrial FK506 binding protein 8 (FKBP8/FKBP38), microtubule-associated protein 1 light chain 3 (LC3) and cytosolic cytochrome C (Cyt C) were determined by using Western blot. LC3 co-localizations with mitochondria and FKBP8 were measured by the immunofluorescence technique. One-way and two-way ANOVAs were used for data analysis. RESULTS: After downhill running, skeletal muscle mitochondrial structure appeared to be abnormal and contained a large number of mitophagosomes; the expression levels of AMPK phosphorylation (E12 = 1.81 ± 0.54), FKBP8 (E12 = 3.11 ± 0.26), LC3 (E12 = 1.80 ± 0.12), CypD (E0 = 1.41 ± 0.26) and Cyt C (E0 = 2.31 ± 0.68) and the co-localization of FKBP8 and LC3 were significantly higher, whereas the expression levels of mitochondrial quantitative protein HSP60 (E12 = 0.62 ± 0.09) were significantly lower than those in the C group (p < 0.05 to p < 0.01). AICAR treatment enhanced AMPK phosphorylation in exercised muscle and the expression levels of mitochondrial FKBP8 and LC3 involved in mitophagy. CONCLUSION: A session of downhill running activated the AMPK phosphorylation and LC3 co-localizations with mitochondria and FKBP8, and induced mitophagy and mitochondrial damage within rat skeletal muscle. (Supported by Natural Science Foundation of China grant 31900842).