High intensity aerobic exercise training improves chronic intermittent hypoxia-induced insulin resistance without basal autophagy modulation

Identification and validation of a novel autophagy-related biomarker in obstructive sleep apnea syndrome

STUDY OBJECTIVES

Obstructive sleep apnea syndrome is closely associated with tumor growth. Chronic intermittent hypoxia promotes autophagy and is related to malignant tumor development. However, the role of autophagy in obstructive sleep apnea syndrome progression remains unclear.

METHODS

obstructive sleep apnea syndrome datasets (GSE135917 and GSE38792) from Gene Expression Omnibus were analyzed to identify differentially expressed genes and autophagy-related differentially expressed genes. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set enrichment analysis were conducted, and a protein-protein interaction network identified hub genes. Colorectal cancer datasets from The Cancer Genome Atlas were used for differential expression and survival analyses, along with gene set enrichment analysis and immune infiltration analysis. Chronic intermittent hypoxia-induced autophagy and oxidative stress were investigated in Sprague-Dawley rats using reactive oxygen species assays. Hub genes were validated in rats and obstructive sleep apnea syndrome patient samples.

RESULTS

Gene set enrichment analysis revealed significant differences in autophagy-related gene expression among obstructive sleep apnea syndrome patients. Hub genes ATG5, CASP1, MAPK8, EIF4G1, and TANK-binding kinase 1 were identified, with ATG5 and TANK-binding kinase 1 validated. Autophagy-related differentially expressed genes were predominantly upregulated in colorectal cancer tissues. TANK-binding kinase 1 expression in colorectal cancer patients was associated with enhanced sensitivity to immunotherapy and CD8 + T cell, macrophage, and regulatory T cell infiltration, potentially influencing the immune microenvironment. The animal experiments showed that chronic intermittent hypoxia increased reactive oxygen species levels, suggesting that chronic intermittent hypoxia plays a role in autophagy. TANK-binding kinase 1 expression was significantly higher in obstructive sleep apnea syndrome patients than in controls, and continuous positive airway pressure did not alter TANK-binding kinase 1 levels.

CONCLUSIONS

This study is the first to describe the potential contribution of TANK-binding kinase 1 to the development of obstructive sleep apnea syndrome and its potential as a novel biomarker and potential therapeutic target for obstructive sleep apnea syndrome.

The Potential Interplay Between HIF-1α, Angiogenic, and Autophagic Signaling During Intermittent Hypoxic Exposure and Exercise

Berkemeier, Quint N., Michael R. Deyhle, James J. McCormick, Kurt A. Escobar, and Christine M. Mermier. The potential interplay between HIF-1α, angiogenic, and autophagic signaling during intermittent hypoxic exposure and exercise High Alt Med Biol. 25:326-336, 2024.-Environmental hypoxia as a result of decreased barometric pressure upon ascent to high altitudes (>2,500 m) presents increased physiological demands compared with low altitudes, or normoxic environments. Competitive athletes, mountaineers, wildland firefighters, military personnel, miners, and outdoor enthusiasts commonly participate in, or are exposed to, forms of exercise or physical labor at moderate to high altitudes. However, the majority of research on intermittent hypoxic exposure is centered around hematological markers, and the skeletal muscle cellular responses to exercise in hypoxic environments remain largely unknown. Two processes that may be integral for the maintenance of cellular health in skeletal muscle include angiogenesis, or the formation of new blood vessels from preexisting vasculature and autophagy, a process that removes and recycles damaged and dysfunctional cellular material in the lysosome. The purpose of this review is to is to examine the current body of literature and highlight the potential interplay between low-oxygen-sensing pathways, angiogenesis, and autophagy during acute and prolonged intermittent hypoxic exposure in conjunction with exercise. The views expressed in this paper are those of the authors and do not reflect the official policy of the Department of Army, DOD, DOE, ORAU/ORISE or U.S. Government.

Autophagy Alterations in White and Brown Adipose Tissues of Mice Exercised under Different Training Protocols

BACKGROUND

Autophagy is a conserved catabolic process that promotes cellular homeostasis and health. Although exercise is a well-established inducer of this pathway, little is known about the effects of different types of training protocols on the autophagy levels of tissues that are tightly linked to age-related metabolic syndromes (like brown adipose tissue) but are not easily accessible in humans.

METHODS

Here, we take advantage of animal models to assess the effects of short- and long-term resistance and endurance training in both white and brown adipose tissue, reporting distinct alterations on autophagy proteins microtubule-associated proteins 1A/1B light chain 3B (MAP1LC3B, or LC3B) and sequestosome-1 (SQSTM1/p62). Additionally, we also analyzed the repercussions of these interventions in fat tissues of mice lacking autophagy-related protein 4 homolog B (ATG4B), further assessing the impact of exercise in these dynamic, regulatory organs when autophagy is limited.

RESULTS

In wild-type mice, both short-term endurance and resistance training protocols increased the levels of autophagy markers in white adipose tissue before this similarity diverges during long training, while autophagy regulation appears to be far more complex in brown adipose tissue. Meanwhile, in ATG4B-deficient mice, only resistance training could slightly increase the presence of lipidated LC3B, while p62 levels increased in white adipose tissue after short-term training but decreased in brown adipose tissue after long-term training.

CONCLUSIONS

Altogether, our study suggests an intricated regulation of exercise-induced autophagy in adipose tissues that is dependent on the training protocol and the autophagy competence of the organism.

Tanshinone IIA inhibited intermittent hypoxia induced neuronal injury through promoting autophagy via AMPK-mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic intermittent hypoxia (CIH) is the primary pathophysiological process of obstructive sleep apnea (OSA) and is closely linked to neurocognitive dysfunction. Tanshinone IIA (Tan IIA) is extracted from Salvia miltiorrhiza Bunge and used in Traditional Chinese Medicine (TCM) to improve cognitive impairment. Studies have shown that Tan IIA has anti-inflammatory, anti-oxidant, and anti-apoptotic properties and provides protection in intermittent hypoxia (IH) conditions. However, the specific mechanism is still unclear.

AIM OF THE STUDY

To assess the protective effect and mechanism of Tan IIA treatment on neuronal injury in HT22 cells exposed to IH.

MATERIALS AND METHODS

The study established an HT22 cell model exposed to IH (0.1% O₂ 3 min/21% O₂ 7 min for six cycles/h). Cell viability was determined using the Cell Counting Kit-8, and cell injury was determined using the LDH release assay. Mitochondrial damage and cell apoptosis were observed using the Mitochondrial Membrane Potential and Apoptosis Detection Kit. Oxidative stress was assessed using DCFH-DA staining and flow cytometry. The level of autophagy was assessed using the Cell Autophagy Staining Test Kit and transmission electron microscopy (TEM). Western blot was used to detect the expressions of the AMPK-mTOR pathway, LC3, P62, Beclin-1, Nrf2, HO-1, SOD2, NOX2, Bcl-2/Bax, and caspase-3.

RESULTS

The study showed that Tan IIA significantly improved HT22 cell viability under IH conditions. Tan IIA treatment improved mitochondrial membrane potential, decreased cell apoptosis, inhibited oxidative stress, and increased autophagy levels in HT22 cells under IH conditions. Furthermore, Tan IIA increased AMPK phosphorylation and LC3II/I, Beclin-1, Nrf2, HO-1, SOD2, and Bcl-2/Bax expressions, while decreasing mTOR phosphorylation and NOX2 and cleaved caspase-3/caspase-3 expressions.

CONCLUSION

The study suggested that Tan IIA significantly ameliorated neuronal injury in HT22 cells exposed to IH. The neuroprotective mechanism of Tan IIA may mainly be related to inhibiting oxidative stress and neuronal apoptosis by activating the AMPK/mTOR autophagy pathway under IH conditions.

Physical Exercise and Liver Autophagy: Potential Roles of IL-6 and Irisin

Autophagic dysregulation contributes to liver diseases. Although some investigations have examined the effects of endurance and resistance exercise on autophagy activation, potential myokines responsible for skeletal muscle-liver crosstalk are still unknown. Based on experimental studies and bioinformatics, we hypothesized that interleukin 6 (IL-6) and irisin might be key players in the contraction-induced release of molecules that regulate liver autophagic responses.

d-Allulose Improves Endurance and Recovery from Exhaustion in Male C57BL/6J Mice

d-Allulose, a rare sugar, improves glucose metabolism and has been proposed as a candidate calorie restriction mimetic. This study aimed to investigate the effects of d-allulose on aerobic performance and recovery from exhaustion and compared them with the effects of exercise training. Male C57BL/6J mice were subjected to exercise and allowed to run freely on a wheel. Aerobic performance was evaluated using a treadmill. Glucose metabolism was analyzed by an intraperitoneal glucose tolerance test (ipGTT). Skeletal muscle intracellular signaling was analyzed by Western blotting. Four weeks of daily oral administration of 3% d-allulose increased running distance and shortened recovery time as assessed by an endurance test. d-Allulose administration also increased the maximal aerobic speed (MAS), which was observed following treatment for >3 or 7 days. The improved performance was associated with lower blood lactate levels and increased liver glycogen levels. Although d-allulose did not change the overall glucose levels as determined by ipGTT, it decreased plasma insulin levels, indicating enhanced insulin sensitivity. Finally, d-allulose enhanced the phosphorylation of AMP-activated protein kinase and acetyl-CoA carboxylase and the expression of peroxisome proliferator-activated receptor γ coactivator 1α. Our results indicate that d-allulose administration enhances endurance ability, reduces fatigue, and improves insulin sensitivity similarly to exercise training. d-Allulose administration may be a potential treatment option to alleviate obesity and enhance aerobic exercise performance.

Role of the p38MAPK signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia

This study explored the role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia (CIH). Male Sprague-Dawley rats were randomly divided to normoxic control (CON), CIH (optimal modeling time was determined prior by measuring the expression of several proteins after 2-, 4-, and 6-wk intermittent hypoxia), solvent (CIH+Veh), or p38MAPK inhibitor (CIH+SB203580) groups. DMSO and SB203580 were injected intraperitoneally 30 min before hypoxia in CIH+Veh and CIH+SB203580 group rats, respectively. Rat learning and memory were evaluated via the Morris water maze test. Ultrastructural changes in the hippocampal CA1 region autophagic vesicles and neurons were observed under transmission electron and light microscopy. Hippocampal microtubule-associated proteins were detected by western blot. Morris water maze test showed that CIH+SB203580 group rats spent significantly more time on the platform quadrant and crossed the platform more times than CIH+Veh group rats (P < 0.01). Hematoxylin-eosin (HE) staining showed greater rat cell damage in the CIH+SB group than in the CIH and CIH+Veh groups. Western blot analysis showed that CIH+SB group rats had significantly lower p-p38MAPK/p38MAPK, LC3I, and p62 expression and higher beclin-1 expression than CIH+Veh group rats (P < 0.01). Electron microscopy showed that CIH+SB203580 group rats had several small hippocampal neuron autophagic vesicles. On immunofluorescence analyses, it showed a higher LC3II expression in CIH+SB203580 group rats than in CIH+Veh group rats (P < 0.01). These results indicate that inhibition of the CIH p38MAPK signaling pathway can activate autophagy and protect hippocampal neurons in rats.NEW & NOTEWORTHY The pathophysiological processes related to autophagy obstructive sleep apnea-hypopnea syndrome (OSAHS) are unclear. This study clarified that the inhibition of the p38MAPK signaling pathway could further activate autophagy in hippocampal nerve cells, thus reducing nerve cell injury.

Impact of Different Physical Exercises on the Expression of Autophagy Markers in Mice

Although physical exercise-induced autophagy activation has been considered a therapeutic target to enhance tissue health and extend lifespan, the effects of different exercise models on autophagy in specific metabolic tissues are not completely understood. This descriptive investigation compared the acute effects of endurance (END), exhaustive (ET), strength (ST), and concurrent (CC) physical exercise protocols on markers of autophagy, genes, and proteins in the gastrocnemius muscle, heart, and liver of mice. The animals were euthanized immediately (0 h) and six hours (6 h) after the acute exercise for the measurement of glycogen levels, mRNA expression of Prkaa1, Ppargc1a, Mtor, Ulk1, Becn1, Atg5, Map1lc3b, Sqstm1, and protein levels of Beclin 1 and ATG5. The markers of autophagy were measured by quantifying the protein levels of LC3II and Sqstm1/p62 in response to three consecutive days of intraperitoneal injections of colchicine. In summary, for gastrocnemius muscle samples, the main alterations in mRNA expressions were observed after 6 h and for the ST group, and the markers of autophagy for the CC group were increased (i.e., LC3II and Sqstm1/p62). In the heart, the Beclin 1 and ATG5 levels were downregulated for the ET group. Regarding the markers of autophagy, the Sqstm1/p62 in the heart tissue was upregulated for the END and ST groups, highlighting the beneficial effects of these exercise models. The liver protein levels of ATG5 were downregulated for the ET group. After the colchicine treatment, the liver protein levels of Sqstm1/p62 were decreased for the END and ET groups compared to the CT, ST, and CC groups. These results could be related to diabetes and obesity development or liver dysfunction improvement, demanding further investigations.

The importance of autophagy regulation in obstructive sleep apnea

PURPOSE

Autophagy, the self-renewal process of cells, is dependent on lysosomes to degrade damaged organelles and proteins. The increased or damaged level of autophagy is proven to relate to a number of disorders, including metabolic disorders, malignant tumors, pulmonary diseases, and neurodegenerative disorders. This review aims to examine the effects of autophagy on the pathogenic mechanism of obstructive sleep apnea (OSA) in order to guide relevant disease treatment.

METHODS

We conducted a search of the literature using the electronic database, focusing on articles that explored the association between OSA and autophagy.

CONCLUSION

OSA can induced autophagy through hypoxia, oxidative stress, endoplasmic reticulum stress, endothelial dysfunction, miRNA, etc. We propose that the mechanism of the autophagy in patients with OSA should be eclucidated in further studies.

Exercise and Organ Cross Talk

Chronic heart failure, diabetes, depression, and other chronic diseases are associated with high mortality rate and low cure rate. Exercise induces muscle contraction and secretes multiple myokines, which affects the signaling pathways in skeletal muscle tissues and regulate remote organ functions. Exercise is known to be effective in treating a variety of chronic diseases. Here we summarize how exercise influences skeletal muscle, heart, brain, gut, and liver, and prevents heart failure, cognitive dysfunction, obesity, fatty liver, and other diseases. Exercise training may achieve additional benefits as compared to the present medication for these chronic diseases through cross talk among skeletal muscle and other organs.

Mechanism of neoagarotetraose protects against intense exercise-induced liver injury based on molecular ecological network analysis

Here we have explored the effect of neoagarotetraose (NAT) on liver injury caused by intense exercise. Our results showed that NAT treatment obviously decreased liver weight (p &lt; 0.01), improved the liver morphological structure, decreased ALT level (p &lt; 0.05) and endotoxin (LPS) (p &lt; 0.01). In addition, NAT could regulate bile acid profiles in feces and serum of mice, which indicated the potential of liver function, suggesting that NAT was effective to relieve intense exercise-induced liver injury. NAT could regulate the expression of colon genes. NAT tended to alter the microbial composition of mice under intense exercise. We uncovered the network interactions between liver traits and microbial communities in NAT treatment mice. Interestingly, our data indicated that intense exercise-induced liver injury may be related to Clostridiales. In summary, these results demonstrated that NAT relieved liver injury induced by intense exercise may be related to gut microbiota.

Rapamycin and ZSTK474 can have differential effects at different post‑infection time‑points regarding CVB3 replication and CVB3‑induced autophagy

Coxsackievirus B3 (CVB3) infection has been shown to stimulate autophagy. We have demonstrated that the inhibition of phosphoinositide 3‑kinase (PI3K)/protein kinase B/mammalian target of rapamycin complex (mTORC) signaling pathway could affect the autophagic reaction induced by CVB3 infection in our previous study. However, the processes associating autophagy and CVB3 replication remain to be determined. In the present study, CVB3‑induced autophagy and its impact on viral replication were investigated. Rapamycin (inhibitor of mTOR) and ZSTK474 (inhibitor of PI3K) were used to change the autophagic reaction caused by CVB3 in Hela cells at different post‑infection (p.i.) time points (6, 9, 12 and 24 h p.i.), meanwhile, we detected the CVB3 mRNA replication and CVB3 capsid protein VP1 expression following the change of autophagy. Here, it was showed that ZSTK474 and Rapamycin promoted CVB3‑induced autophagy, as well as decreasing CVB3 mRNA replication and CVB3 capsid protein VP1 expression at 6 and 9 h p.i. ZSTK474 also alleviated CVB3‑induced autophagy, and decreased CVB3 mRNA replication and VP1 expression at 12 and 24 h p.i. However, Rapamycin continued to promote CVB3‑induced autophagy and increase CVB3 mRNA replication at 12 and 24 h p.i, as well as increase VP1 expression at 12 h, but not at 24 h, p.i. In the present study, we found Rapamycin and ZSTK474 have differential effects at different p.i. time‑points regarding CVB3 replication and CVB3‑induced autophagy. This indicates that the association between CVB3‑induced autophagy and viral replication depends on the infection time. During the early course of infection, autophagy may help host cells clear the virus, thereby providing protection, whereas when the infection time increases, autophagy may be exploited for viral replication.

Autophagy and inflammation in chronic respiratory disease

Persistent inflammation within the respiratory tract underlies the pathogenesis of numerous chronic pulmonary diseases including chronic obstructive pulmonary disease, asthma and pulmonary fibrosis. Chronic inflammation in the lung may arise from a combination of genetic susceptibility and environmental influences, including exposure to microbes, particles from the atmosphere, irritants, pollutants, allergens, and toxic molecules. To this end, an immediate, strong, and highly regulated inflammatory defense mechanism is needed for the successful maintenance of homeostasis within the respiratory system. Macroautophagy/autophagy plays an essential role in the inflammatory response of the lung to infection and stress. At baseline, autophagy may be critical for inhibiting spontaneous pulmonary inflammation and fundamental for the response of pulmonary leukocytes to infection; however, when not regulated, persistent or inefficient autophagy may be detrimental to lung epithelial cells, promoting lung injury. This perspective will discuss the role of autophagy in driving and regulating inflammatory responses of the lung in chronic lung diseases with a focus on potential avenues for therapeutic targeting. Abbreviations AR allergic rhinitis AM alveolar macrophage ATG autophagy-related CF cystic fibrosis CFTR cystic fibrosis transmembrane conductance regulator COPD chronic obstructive pulmonary disease CS cigarette smoke CSE cigarette smoke extract DC dendritic cell IH intermittent hypoxia IPF idiopathic pulmonary fibrosis ILD interstitial lung disease MAP1LC3B microtubule associated protein 1 light chain 3 beta MTB Mycobacterium tuberculosis MTOR mechanistic target of rapamycin kinase NET neutrophil extracellular traps OSA obstructive sleep apnea PAH pulmonary arterial hypertension PH pulmonary hypertension ROS reactive oxygen species TGFB1 transforming growth factor beta 1 TNF tumor necrosis factor.

Intermittent hypoxia-induced insulin resistance is associated with alterations in white fat distribution

Sleep apnea syndrome is characterized by repetitive upper airway collapses during night leading to intermittent hypoxia (IH). The latter is responsible for metabolic disturbances that rely, at least in part, on abdominal white fat inflammation. Besides qualitative alterations, we hypothesized that IH could also modify body fat distribution, a key factor for metabolic complications. C57BL6 mice exposed to IH (21-5% FiO₂, 60 s cycle, 8 h/day) or air for 6 weeks were investigated for topographic fat alterations (whole-body MRI). Specific role of epididymal fat in IH-induced metabolic dysfunctions was assessed in lipectomized or sham-operated mice exposed to IH or air. Whereas total white fat volume was unchanged, IH induced epididymal adipose tissue (AT) loss with non-significant increase in subcutaneous and mesenteric fat. This was associated with impaired insulin sensitivity and secretion. Epididymal lipectomy led to increased subcutaneous fat in the perineal compartment and prevented IH-induced metabolic disturbances. IH led to reduced epididymal AT and impaired glucose regulation. This suggests that, rather than epididymal AT volume, qualitative fat alterations (i.e. inflammation) could represent the main determinant of metabolic dysfunction. This deterioration of glucose regulation was prevented in epididymal-lipectomized mice, possibly through prevention of IH-induced epididymal AT alterations and compensatory increase in subcutaneous AT.