A single bout of exhaustive treadmill exercise increased AMPK activation associated with enhanced autophagy in mice skeletal muscle

Restoring Autophagy by Exercise Ameliorates Insulin Resistance Partly via Calcineurin-Driven TFEB Nuclear Translocation

Exercise activates autophagy and lysosome system in skeletal muscle, which are known to play an important role in metabolic adaptation. However, the mechanism of exercise-activated autophagy and lysosome system in obese insulin resistance remains covert. In this study, we investigated the role of exercise-induced activation of autophagy and lysosome system in improving glucose metabolism of skeletal muscle. Male C57BL/6 mice were randomly divided into five groups: the chow diet (CD) group, the high-fat diet (HFD) group, the high-fat diet plus exercise (HFD-E) group and the HFD-E treated with calcineurin inhibitor FK506 (HFD-E-F) or saline (HFD-E-S) groups. The mice in exercise groups (HFD-E, HFD-E-F and HFD-E-S) were subjected to aerobic treadmill exercise (speed at 12 m/min for 1 h per session, 0° slope, 5 days per week for 12 weeks). Mice of HFD-E-F group were intraperitoneally administered FK506 (1 mg/kg), once each day for 2 weeks before the end of exercise. Expressions pTFEB, T-TFEB and autophagy-lysosome markers, including Beclin1, LC3, ULK1, SQSTM1, LAMP1, CTSD and CTSL proteins in gastrocnemius muscle were analysed. We demonstrated that HFD induced insulin resistance and decreased autophagy-lysosomal proteins and the exercise significantly increased transcription factor EB (TFEB) translocation from the cytoplasm to the nucleus, restored the impaired autophagy-lysosomal-related protein expressions, and improved glucose metabolism. The increase in TFEB nuclear translocation was partly blocked by the calcineurin inhibitor FK506. Our results suggest that exercise promotes autophagy and lysosome restoration by regulating calcineurin-mediated TFEB nuclear translocation, ultimately alleviating HFD-induced insulin resistance in mice skeletal muscle.

Autophagy and Exercise: Current Insights and Future Research Directions

Autophagy is a cellular process by which proteins and organelles are degraded inside the lysosome. Exercise is known to influence the regulation of autophagy in skeletal muscle. However, as gold standard techniques to assess autophagy flux in vivo are restricted to animal research, important gaps remain in our understanding of how exercise influences autophagy activity in humans. Using available datasets, we show how the gene expression profile of autophagy receptors and ATG8 family members differ between human and mouse skeletal muscle, providing a potential explanation for their differing exercise-induced autophagy responses. Furthermore, we provide a comprehensive view of autophagy regulation following exercise in humans by summarizing human transcriptomic and phosphoproteomic datasets that provide novel targets of potential relevance. These newly identified phosphorylation sites may provide an explanation as to why both endurance and resistance exercise lead to an exercise-induced reduction in LC3B-II, while possibly divergently regulating autophagy receptors, and, potentially, autophagy flux. We also provide recommendations to use ex vivo autophagy flux assays to better understand the influence of exercise, and other stimuli, on autophagy regulation in humans. This review provides a critical overview of the field and directs researchers towards novel research areas that will improve our understanding of autophagy regulation following exercise in humans.

Restoration of autophagy activity by dipsacoside B alleviates exhaustive exercise-induced kidney injury via the AMPK/mTOR pathway

Exhaustive exercise (EE) induces kidney injury, but its concrete mechanism has not been fully elucidated. Hepatoprotective effects of dipsacoside B (DB) have been found previously, involving in autophagy induction. However, whether DB exerts renal protective effect and its potential mechanism are still unknown. The present study aimed to investigate the benefit of DB in EE-induced kidney injury and decipher its underlying mechanism. Here, we found that DB ameliorated EE-induced renal dysfunction and renal histopathological injury in rats. DB possessed anti-inflammatory, anti-oxidative, and anti-apoptotic functions in kidneys of exercise-induced exhausted rats. Besides, DB improved autophagy function in kidneys of EE rats. Mechanically, activation of the adenylate-activating protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway was implicated in the kidney injury-relieving effects and autophagy restoration induced by DB. Collectively, these findings provide reference for the clinical application of DB in preventing and managing EE-induced kidney injury.

Autophagy machinery plays an essential role in traumatic brain injury-induced apoptosis and its related behavioral abnormalities in mice: focus on Boswellia Sacra gum resin

Traumatic brain injury (TBI) is described as a structural damage or physiological disturbance of brain function that occurs after trauma and causes disability or death in people of all ages. New treatment targets for TBI are being explored because current medicines are frequently ineffectual and poorly tolerated. There is increasing evidence that following TBI, there are widespread changes in autophagy-related proteins in both experimental and clinical settings. The current study investigated if Boswellia Sacra Gum Resin (BSR) treatment (500 mg/kg) could modulate post-TBI neuronal autophagy and protein expression, as well as whether BSR could markedly improve functional recovery in a mouse model of TBI. Taken together our results shows for the first time that BSR limits histological alteration, lipid peroxidation, antioxidant, cytokines release and autophagic flux alteration induced by TBI.

Polyamines and Physical Activity in Musculoskeletal Diseases: A Potential Therapeutic Challenge

Autophagy dysregulation is commonplace in the pathogenesis of several invalidating diseases, such as musculoskeletal diseases. Polyamines, as spermidine and spermine, are small aliphatic cations essential for cell growth and differentiation, with multiple antioxidant, anti-inflammatory, and anti-apoptotic effects. Remarkably, they are emerging as natural autophagy regulators with strong anti-aging effects. Polyamine levels were significantly altered in the skeletal muscles of aged animals. Therefore, supplementation of spermine and spermidine may be important to prevent or treat muscle atrophy. Recent in vitro and in vivo experimental studies indicate that spermidine reverses dysfunctional autophagy and stimulates mitophagy in muscles and heart, preventing senescence. Physical exercise, as polyamines, regulates skeletal muscle mass inducing proper autophagy and mitophagy. This narrative review focuses on the latest evidence regarding the efficacy of polyamines and exercise as autophagy inducers, alone or coupled, in alleviating sarcopenia and aging-dependent musculoskeletal diseases. A comprehensive description of overall autophagic steps in muscle, polyamine metabolic pathways, and effects of the role of autophagy inducers played by both polyamines and exercise has been presented. Although literature shows few data in regard to this controversial topic, interesting effects on muscle atrophy in murine models have emerged when the two "autophagy-inducers" were combined. We hope these findings, with caution, can encourage researchers to continue investigating in this direction. In particular, if these novel insights could be confirmed in further in vivo and clinical studies, and the two synergic treatments could be optimized in terms of dose and duration, then polyamine supplementation and physical exercise might have a clinical potential in sarcopenia, and more importantly, implications for a healthy lifestyle in the elderly population.