Mitochondrial DNA alteration in obstructive sleep apnea

Activation of Sirtuin3 by honokiol ameliorates alveolar epithelial cell senescence in experimental silicosis via the cGAS-STING pathway

BACKGROUND

Silicosis, characterized by interstitial lung inflammation and fibrosis, poses a significant health threat. ATII cells play a crucial role in alveolar epithelial repair and structural integrity maintenance. Inhibiting ATII cell senescence has shown promise in silicosis treatment. However, the mechanism behind silica-induced senescence remains elusive.

METHODS

The study employed male C57BL/6 N mice and A549 human alveolar epithelial cells to investigate silicosis and its potential treatment. Silicosis was induced in mice via intratracheal instillation of crystalline silica particles, with honokiol administered intraperitoneally for 14 days. Silica-induced senescence in A549 cells was confirmed, and SIRT3 knockout and overexpression cell lines were generated. Various analyses were conducted, including immunoblotting, qRT-PCR, histology, and transmission electron microscopy. Statistical significance was determined using one-way ANOVA with Tukey's post-hoc test.

RESULTS

This study elucidates how silica induces ATII cell senescence, emphasizing mtDNA damage. Notably, honokiol (HKL) emerges as a promising anti-senescence and anti-fibrosis agent, acting through sirt3. honokiol effectively attenuated senescence in ATII cells, dependent on sirt3 expression, while mitigating mtDNA damage. Sirt3, a class III histone deacetylase, regulates senescence and mitochondrial stress. HKL activates sirt3, protecting against pulmonary fibrosis and mitochondrial damage. Additionally, HKL downregulated cGAS expression in senescent ATII cells induced by silica, suggesting sirt3's role as an upstream regulator of the cGAS/STING signaling pathway. Moreover, honokiol treatment inhibited the activation of the NF-κB signaling pathway, associated with reduced oxidative stress and mtDNA damage. Notably, HKL enhanced the activity of SOD2, crucial for mitochondrial function, through sirt3-mediated deacetylation. Additionally, HKL promoted the deacetylation activity of sirt3, further safeguarding mtDNA integrity.

CONCLUSIONS

This study uncovers a natural compound, HKL, with significant anti-fibrotic properties through activating sirt3, shedding light on silicosis pathogenesis and treatment avenues.

Berberine ameliorates chronic intermittent hypoxia-induced cardiac remodelling by preserving mitochondrial function, role of SIRT6 signalling

Chronic intermittent hypoxia (CIH) is associated with an increased risk of cardiovascular diseases. Previously, we have shown that berberine (BBR) is a potential cardioprotective agent. However, its effect and mechanism on CIH-induced cardiomyopathy remain uncovered. This study was designed to determine the effects of BBR against CIH-induced cardiac damage and to explore the molecular mechanisms. Mice were exposed to 5 weeks of CIH with or without the treatment of BBR and adeno-associated virus 9 (AAV9) carrying SIRT6 or SIRT6-specific short hairpin RNA. The effect of BBR was evaluated by echocardiography, histological analysis and western blot analysis. CIH caused the inactivation of myocardial SIRT6 and AMPK-FOXO3a signalling. BBR dose-dependently ameliorated cardiac injury in CIH-induced mice, as evidenced by increased cardiac function and decreased fibrosis. Notably, SIRT6 overexpression mimicked these beneficial effects, whereas infection with recombinant AAV9 carrying SIRT6-specific short hairpin RNA abrogated them. Mechanistically, BBR reduced oxidative stress damage and preserved mitochondrial function via activating SIRT6-AMPK-FOXO3a signalling, enhancing mitochondrial biogenesis as well as PINK1-Parkin-mediated mitophagy. Taken together, these data demonstrate that SIRT6 activation protects against the pathogenesis of CIH-induced cardiac dysfunction. BBR attenuates CIH-induced myocardial injury by improving mitochondrial biogenesis and PINK1-Parkin-dependent mitophagy via the SIRT6-AMPK-FOXO3a signalling pathway.

Impact of obstructive sleep apnea on neuromuscular transmission- a descriptive study

Objective: Obstructive sleep apnea (OSA) is a sleep disorder accompanied by intermittent hypoxia. Neuromuscular transmission (NT) is known to be disturbed under chronic hypoxia. In this descriptive study, it has been aimed to test NT under intermittent hypoxia in OSA. Methods: Thirty-nine newly diagnosed OSA patients without any comorbidities or conditions that alter NT were included in the study. Jitter analysis was performed using a concentric needle electrode. Results: The mean jitter value of 39 OSA patients was 25.9 ± 3.7 μs. When compared to the mean reference jitter values, patients in the present study had significantly higher jitter (p < 0.001). Seven (17.9%) patients met the electrophysiological criteria for NT failure. Conclusion: The authors propose that intermittent hypoxia can be the trigger for NT failure in OSA. The interaction between increased oxidative stress and disturbed mitochondrial functions may also contribute.

Sleep fragmentation induces heart failure in a hypertrophic cardiomyopathy mouse model by altering redox metabolism

Sleep fragmentation (SF) disrupts normal biological rhythms and has major impacts on cardiovascular health; however, it has never been shown to be a risk factor involved in the transition from cardiac hypertrophy to heart failure (HF). We now demonstrate devastating effects of SF on hypertrophic cardiomyopathy (HCM). We generated a transgenic mouse model harboring a patient-specific myosin binding protein C3 (MYBPC3) variant displaying HCM, and measured the progression of pathophysiology in the presence and absence of SF. SF induces mitochondrial damage, sarcomere disarray, and apoptosis in HCM mice; these changes result in a transition of hypertrophy to an HF phenotype by chiefly targeting redox metabolic pathways. Our findings for the first time show that SF is a risk factor for HF transition and have important implications in clinical settings where HCM patients with sleep disorders have worse prognosis, and strategic intervention with regularized sleep patterns might help such patients.

Mitochondrial Dysfunction and Metabolic Reprogramming in Obesity and Asthma

Mitochondrial dysfunction and metabolic reprogramming have been extensively studied in many disorders ranging from cardiovascular to neurodegenerative disease. Obesity has previously been associated with mitochondrial fragmentation, dysregulated glycolysis, and oxidative phosphorylation, as well as increased reactive oxygen species production. Current treatments focus on reducing cellular stress to restore homeostasis through the use of antioxidants or alterations of mitochondrial dynamics. This review focuses on the role of mitochondrial dysfunction in obesity particularly for those suffering from asthma and examines mitochondrial transfer from mesenchymal stem cells to restore function as a potential therapy. Mitochondrial targeted therapy to restore healthy metabolism may provide a unique approach to alleviate dysregulation in individuals with this unique endotype.

Intermittent hypoxia induces hepatic senescence through promoting oxidative stress in a mouse model

PURPOSE

Metabolic-associated fatty liver disease (MAFLD) is an aging-related disease. Obstructive sleep apnea (OSA) may cause MAFLD. This study aimed to explore whether or not intermittent hypoxia (IH), the hallmark of OSA, induces liver aging through oxidative stress.

METHODS

C57BL/6J male mice were administered normal air (control), IH, or antioxidant tempol + IH daily for 6 weeks before the collection of serum and liver tissue samples. A histological examination was conducted to assess liver aging. ELISA was performed to measure liver function indicator levels in the serum and oxidative stress indicator activities in the liver. Western blot analysis was carried out to determine the protein expression of the markers related to oxidative stress, inflammation, and senescence.

RESULTS

Compared with control, IH resulted in significant increases in serum ALT, AST, and TG levels in mice (all P < 0.001), along with lobular inflammation and accumulation of collagen and fat in the liver. The protein levels of inflammatory factors and senescent markers were significantly increased in the IH mouse liver compared with those in the control mouse liver. Meanwhile, IH significantly reduced SOD and CAT activities while enhancing p22phox and Nrf2 protein expression in mouse liver compared with control. Importantly, antioxidant therapy with tempol effectively abrogated the effects of IH on oxidative stress response and aging-related liver injury.

CONCLUSIONS

Our findings suggest that IH induces liver inflammation and aging through oxidative stress. OSA may exacerbate target organ aging and participate in target organ damage. Strategies targeting oxidative stress may prevent and treat OSA-related MAFLD.

Role of Oxidative Stress in the Occurrence and Development of Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) causes recurrent apnea and intermittent hypoxia at night, leading to several complications such as cognitive dysfunction. However, the molecular mechanisms underlying cognitive dysfunction in OSAS are unclear, and oxidative stress mediated by intermittent hypoxia is an important mechanism. In addition, the improvement of cognitive dysfunction in patients with OSAS varies by different treatment regimens; among them, continuous positive airway pressure therapy (CPAP) is mostly recognized for improving cognitive dysfunction. In this review, we discuss the potential mechanisms of oxidative stress in OSAS, the common factors of affecting oxidative stress and the Links between oxidative stress and inflammation in OSAS, focusing on the potential links between oxidative stress and cognitive dysfunction in OSAS and the potential therapies for neurocognitive dysfunction in patients with OSAS mediated by oxidative stress. Therefore, further analysis on the relationship between oxidative stress and cognitive dysfunction in patients with OSAS will help to clarify the etiology and discover new treatment options, which will be of great significance for early clinical intervention.

Oxidative Stress in Obstructive Sleep Apnea Syndrome: Putative Pathways to Hearing System Impairment

INTRODUCTION

OSAS is a disease that affects 2% of men and 4% of women of middle age. It is a major health public problem because untreated OSAS could lead to cardiovascular, metabolic, and cerebrovascular complications. The more accepted theory relates to oxidative stress due to intermittent hypoxia, which leads, after an intense inflammatory response through multiple pathways, to endothelial damage. The objective of this study is to demonstrate a correlation between OSAS and hearing loss, the effect of the CPAP on hearing function, and if oxidative stress is also involved in the damaging of the hearing system.

METHODS

A review of the literature has been executed. Eight articles have been found, where seven were about the correlation between OSAS and the hearing system, and only one was about the CPAP effects. It is noted that two of the eight articles explored the theory of oxidative stress due to intermittent hypoxia.

RESULTS

All studies showed a significant correlation between OSAS and hearing function (p < 0.05).

CONCLUSIONS

Untreated OSAS affects the hearing system at multiple levels. Oxidative stress due to intermittent hypoxia is the main pathogenetic mechanism of damage. CPAP has no effects (positive or negative) on hearing function. More studies are needed, with the evaluation of extended high frequencies, the execution of vocal audiometry in noisy environments, and the evaluation of potential biomarkers due to oxidative stress.

Mitochondrial replication, transcription, and function in obstructive sleep apnea

We assessed mitochondrial replication, transcription, and function in the upper airways of obstructive sleep apnea (OSA) patients and the effects of uvulopalatopharyngoplasty. Twenty subjects with mild and 40 with moderate to severe OSA requiring uvulopalatopharyngoplasty were included. Mitochondrial transcription factor A (TFAM) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in uvula specimens were assessed by immunohistochemical staining, and their mRNA and protein expression was examined using reverse-transcription polymerase chain reaction and western blotting, respectively. The mitochondrial to nuclear DNA (Mt/N) ratio in the blood, exhaled breath condensate (EBC), and uvula was measured using quantitative reverse-transcription polymerase chain reaction. TFAM and PGC-1α protein concentrations in the plasma and EBC were determined using enzyme-linked immunosorbent assay. All tested parameters were higher in the OSA group than in the control. Three months later, 21 uvulopalatopharyngoplasty-responsive patients with OSA showed decreased TFAM and PGC-1α concentrations and EBC Mt/N ratio while these remained high in 19 uvulopalatopharyngoplasty-unresponsive patients. The OSA group showed severe inflammation, increased mitochondrial replication and transcription-related signaling, and mitochondrial dysfunction in the uvula. Successful OSA treatment using uvulopalatopharyngoplasty restored the TFAM and PGC-1α levels and EBC Mt/N ratio.

Mitochondria Need Their Sleep: Redox, Bioenergetics, and Temperature Regulation of Circadian Rhythms and the Role of Cysteine-Mediated Redox Signaling, Uncoupling Proteins, and Substrate Cycles

Although circadian biorhythms of mitochondria and cells are highly conserved and crucial for the well-being of complex animals, there is a paucity of studies on the reciprocal interactions between oxidative stress, redox modifications, metabolism, thermoregulation, and other major oscillatory physiological processes. To address this limitation, we hypothesize that circadian/ultradian interaction of the redoxome, bioenergetics, and temperature signaling strongly determine the differential activities of the sleep–wake cycling of mammalians and birds. Posttranslational modifications of proteins by reversible cysteine oxoforms, S-glutathionylation and S-nitrosylation are shown to play a major role in regulating mitochondrial reactive oxygen species production, protein activity, respiration, and metabolomics. Nuclear DNA repair and cellular protein synthesis are maximized during the wake phase, whereas the redoxome is restored and mitochondrial remodeling is maximized during sleep. Hence, our analysis reveals that wakefulness is more protective and restorative to the nucleus (nucleorestorative), whereas sleep is more protective and restorative to mitochondria (mitorestorative). The “redox–bioenergetics–temperature and differential mitochondrial–nuclear regulatory hypothesis” adds to the understanding of mitochondrial respiratory uncoupling, substrate cycling control and hibernation. Similarly, this hypothesis explains how the oscillatory redox–bioenergetics–temperature–regulated sleep–wake states, when perturbed by mitochondrial interactome disturbances, influence the pathogenesis of aging, cancer, spaceflight health effects, sudden infant death syndrome, and diseases of the metabolism and nervous system.

Changes in glial cells and neurotrophic factors due to rotenone-induced oxidative stress in Nrf2 knockout mice

Glaucoma is one of the most common causes of blindness worldwide. It is thought to be a multifactorial disease with underlying mechanisms that include mitochondrial dysfunction and oxidative stress. Here, we used NF-E2 related factor 2 (Nrf2) knockout (KO) mice, which are vulnerable to oxidative stress, to examine a neuroprotective effect against oxidative stress due to rotenone, a mitochondrial complex I inhibitor. Wild-type (WT) and Nrf2 KO mice received an oral solution of rotenone for 30 days. We then extracted the retinas and performed immunohistochemistry and quantitative RT-PCR. We also prepared a primary Müller cell culture of samples from each mouse, added 30 μM rotenone, and then measured cell viability, cytotoxicity and CellRox absorbance. We also examined gene expression. We found a significant increase in the number of 8-OHdG-positive retinal ganglion cells (RGCs) after rotenone administration in both the WT and Nrf2 KO mice. There was no difference in the number of RNA-binding protein with multiple splicing (RBPMS)-positive RGCs in the WT and Nrf2 KO mice, but Nrf2 KO mice that were given rotenone had significantly less retinal gene expression of RBPMS than Nrf2 KO mice given a control. Moreover, there was significantly higher mRNA gene expression of vimentin and glial fibrillary acidic protein (GFAP) in Nrf2 KO mice that received rotenone than WT mice that received rotenone. A statistical analysis of the in vitro experiment showed that cell viability was lower, cytotoxicity was higher, and oxidative stress was higher in the Müller cells of the Nrf2 KO mice than the WT mice. Finally, brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF) were significantly higher in the Müller cells of the Nrf2 KO mice than the WT mice. These findings suggest that in Nrf2 KO mice under oxidative stress caused by rotenone, temporary neurotrophic factors are secreted from the Müller cells, conferring neuroprotection in these cells.

Obstructive Sleep Apnea: A Look towards Micro-RNAs as Biomarkers of the Future

Sleep-disordered breathing (SDB) includes a broad spectrum of diseases, of which obstructive sleep apnea syndrome (OSA) is the most clinically significant manifestation. OSA is a respiratory disorder characterized by episodes of complete or partial obstruction of the upper airways that disturb ventilation and sleep architecture. In recent years, interest in the clinical implications of OSA seems to have increased, probably due to the numerous studies that have shown the existence of an important correlation between OSA and cardiovascular, dysmetabolic, and neoplastic changes. The guidelines currently available highlight the importance of diagnosis and effective treatment for OSA, underlining the need for new biomarkers that are useful in clinical practice, feasible, and reproducible to guide medical decision making. In this review, we intend to provide an overview of the potential role of microRNAs as new indicators for OSA management. MicroRNAs (miRNAs) are small non-coding RNA molecules that play an important role in RNA silencing and regulation of gene expression at the post-transcriptional level. These can bind specifically to their target genes by forming silencing complexes, thus inducing degradation or altered gene expression. A wide range of miRNAs have been extensively studied in a variety of diseases including cancer, and recently, miRNAs have been shown to have enormous potential to function as diagnostic and clinical biomarkers of disease. This review includes recent studies that establish the inevitable role of miRNAs in the pathogenesis of OSA.

Flow-mediated skin fluorescence: A novel method for the estimation of sleep apnea risk in healthy persons and cardiac patients

BACKGROUND

A pilot study revealed a relationship between the results of flow mediated skin fluorescence (FMSF) and of ECG-Holter-based estimated apnea/hypopnea index (eAHI) in asymptomatic individuals. The aim of this study was to test whether the results of FMSF show a relationship with the eAHI in patients with coronary artery disease or aortic stenosis.

METHODS

Twenty-one patients (12 coronary disease, 9 aortic stenosis) and 37 healthy volunteers were included. FMSF was assessed before, during and after the pressure occlusion of the brachial artery, using a prototype device allowing the quantification of skin fluorescence. The values of FMSF expressed as baseline (BASE), maximum (MAX), and minimum (MIN) were analyzed. The percentages of ischemic response (IR) and hyperemic response (HR) were calculated. The eAHI was assessed from night ECG-Holter recordings. Differences between the groups and the relationships between the parameters were analyzed statistically.

RESULTS

Mean ± standard deviation of BASE, MAX, MIN and IR were not significantly different in both groups (p > 0.05). HR was significantly lower in cardiac patients (14.7 ± 7.5 vs. 11.8 ± 5.1; p = 0.048), whose eAHI was significantly higher (11.0 ± 7.4 vs. 36.3 ± 16.5; p < 0.01). Negative correlation for MAX and eAHI was found in volunteers and patients: r = -0.38, p = 0.02 and r = -0.47, p = 0.03, respectively. In volunteers, HR had a negative correlation with eAHI: r = -0.34, p = 0.04.

CONCLUSIONS

This pioneer study confirms that FMSF can be used to detect the negative correlation between MAX fluorescence and eAHI not only among healthy volunteers, but also among cardiac patients with coronary artery disease or aortic stenosis.

Obstructive sleep apnea and the incidence and mortality of gastrointestinal cancers: a systematic review and meta-analysis of 5,120,837 participants

Background

Emerging evidence has shown higher overall cancer incidence in patients with obstructive sleep apnea. Gastrointestinal cancers, including esophageal, stomach, liver, pancreas, and colorectal cancers account for 26% of incident cancers. However, the link between gastrointestinal cancers and obstructive sleep apnea is still unclear. We performed a systematic review and meta-analysis (registered PROSPERO CRD42021220836) to investigate the association between obstructive sleep apnea and incidence of gastrointestinal cancer.

Methods

We searched four electronic databases (PubMed, Embase, Cochrane Library, Scopus) and included studies published from inception till 15th November 2020 reporting the association of obstructive sleep apnea with gastrointestinal cancer incidence. Extracted data was meta-analyzed in a random-effects model.

Results

A total of seven studies were included, forming a combined cohort of 5,120,837 patients. Studies which adjusted for demographics and comorbidities were included in meta-analysis. Among four studies with 7-11 years of median follow-up, patients with obstructive sleep apnea experienced increased incidence of colorectal cancer (HR 1.70, 95% CI: 1.48-1.96, I²=22%). Pancreatic cancer incidence was nominally increased in three studies (HR 1.36, 95% CI: 0.88-2.09, I²=96), though this was not statistically significant. There was no association between obstructive sleep apnea and liver cancer incidence among three studies (HR 0.99, 95% CI: 0.81-1.22, I²=84). However, the lack of a statistically significant relationship between obstructive sleep apnea and pancreatic cancer in our meta-analysis does not necessarily imply the true absence of an association.

Conclusions

An increased risk of colorectal cancer was seen in patients with obstructive sleep apnea among studies with long-term follow-up. Further research is required to explore the utility of incorporating obstructive sleep apnea screening into colorectal cancer screening guidelines to identify high-risk individuals and to confirm a possible association of obstructive sleep apnea with pancreatic cancer.

PROSPERO Registration

CRD42021220836.

Banxia-Houpu decoction diminishes iron toxicity damage in heart induced by chronic intermittent hypoxia

CONTEXT

Obstructive sleep apnoea (OSA) causes chronic intermittent hypoxia (CIH), which results in mitochondrial dysfunction and generates reactive oxygen species (ROS) in the heart. Excessive free iron could accelerate oxidative damage, which may be involved in this process. Banxia-Houpu decoction (BHD) was reported to improve the apnoea hypopnoea index in OSA patients, but the specific mechanism was still unclear.

OBJECTIVE

To investigate whether BHD could reduce CIH-induced heart damage by regulating iron metabolism and mitochondrial function.

MATERIALS AND METHODS

C57BL/6N mice were randomly divided into control, CIH and BHD groups. Mice were exposed to CIH (21 - 5% O2, 20 times/h, 8 h/d) and administered BHD (3.51, 7.01 and 14.02 g/kg, intragastrically) for 21 d. Cardiac and mitochondrial function, iron levels, apoptosis and mitophagy were determined.

RESULTS

BHD (7.01 g/kg) significantly improved cardiac dysfunction, pathological change and mitochondrial structure induced by CIH. BHD increased the Bcl-2/Bax ratio (1.4-fold) and inhibited caspase 3 cleavage in CIH mice (0.45-fold). BHD activated mitophagy by upregulating Parkin (1.94-fold) and PINK1 (1.26-fold), inhibiting the PI3K-AKT-mTOR pathway. BHD suppressed ROS generation by decreasing NOX2 (0.59-fold) and 4-HNE (0.83-fold). BHD reduced the total iron in myocardial cells (0.72-fold) and mitochondrial iron by downregulating Mfrn2 (0.81-fold) and MtFt (0.78-fold) proteins, and upregulating ABCB8 protein (1.33-fold). Rosmarinic acid, the main component of Perilla Leaf in BHD, was able to react with Fe2+ and Fe3+ in vitro.

DISCUSSION AND CONCLUSIONS

These findings encourage the use of BHD to resist cardiovascular injury and provide the theoretical basis for clinical treatment in OSA patients.

WITHDRAWN: Mitochondria need their sleep: Sleep-wake cycling and the role of redox, bioenergetics, and temperature regulation, involving cysteine-mediated redox signaling, uncoupling proteins, and substrate cycles

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Association of obstructive sleep apnea and nocturnal hypoxemia with all-cancer incidence and mortality: a systematic review and meta-analysis

STUDY OBJECTIVES

Biological models suggest that obstructive sleep apnea (OSA) is potentially carcinogenic. We aimed to clarify the inconsistent epidemiological literature by considering various traditional and novel OSA severity indices.

METHODS

We systematically searched PubMed, Embase, Scopus, and the Cochrane Library for observational or randomized studies of associations of OSA, measured by diagnostic codes or any index, each with all-cancer incidence or mortality in adults, compared with participants with no/mild OSA. Two reviewers independently selected studies, extracted data, and evaluated study bias using the Newcastle-Ottawa scale and quality of evidence using GRADE (Grading of Recommendations Assessment, Development, and Evaluation). We performed inverse variance-weighted, random-effects meta-analyses and sensitivity analyses.

RESULTS

We included 20 observational studies (5,340,965 participants), all with moderate/low bias, from 1,698 records. Based on T90 (sleep duration with oxygen saturation < 90%), patients with OSA who had moderate (T90 > 1.2%, hazard ratio [HR] = 1.28, 95% confidence interval [CI] = 1.07-1.54) and severe nocturnal hypoxemia (T90 > 12%, HR = 1.43, 95% CI = 1.16-1.76) experienced 30%-40% higher pooled all-cancer risk than normoxemic patients, after multiple adjustment for covariates including obesity. Furthermore, severe nocturnal hypoxemia nearly tripled all-cancer mortality (HR = 2.66, 95% CI = 1.21-5.85). Patients with apnea-hypopnea index-defined severe OSA, but not moderate OSA, had higher all-cancer risk (HR = 1.18, 95% CI = 1.03-1.35) but similar all-cancer mortality as patients without OSA. An OSA diagnosis was not associated with all-cancer risk. Evidence quality ranged from low to moderate. Insufficient evidence was available on the oxygen desaturation index, lowest/median saturation, and arousal index.

CONCLUSIONS

In patients with OSA, nocturnal hypoxemia is independently associated with all-cancer risk and mortality. Future studies should explore if risk differs by cancer type, and whether cancer screening and OSA treatment are beneficial.

SYSTEMATIC REVIEW REGISTRATION

Registry: PROSPERO; URL: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=220836; Identifier: CRD42021220836.

CITATION

Tan BKJ, Teo YH, Tan NKW, et al. Association of obstructive sleep apnea and nocturnal hypoxemia with all-cancer incidence and mortality: a systematic review and meta-analysis. J Clin Sleep Med. 2022;18(5):1427-1440.

Mitochondria determine response to anti-programmed cell death protein-1 (anti-PD-1) immunotherapy: An evidence-based hypothesis

Immunotherapy based on programmed cell death protein-1 (PD-1) is a promising approach in oncology. However, a significant fraction of patients remain unresponsive. Therefore, it is imperative to clarify the relevant predictive factors. A decrease in cellular adenosine triphosphate (c-ATP) level can predispose to cellular dysfunction. ATP is a prerequisite for proper T cell migration and activation. Therefore, a decrease in the c-ATP level impairs T cell function and promotes cancer progression. This article gives an overview of the potential predictive factors of PD-1 blockade. Besides, it highlights the pivotal role of mitochondria in response to anti-PD-1 therapies.

Continuous positive airway pressure affects mitochondrial function and exhaled PGC1-α levels in obstructive sleep apnea

Purpose: Subjects with obstructive sleep apnea (OSA) exhibit systemic and upper airway oxidative stress and inflammation, which cause mitochondrial dysfunction. The intend of this study is to estimate mitochondrial function (mitochondrial DNA/nuclear DNA [Mt/N] ratio) and protein levels of peroxisome proliferator-coactivated receptor gamma co-activator 1-alpha (PGC1-α) in the exhaled breath condensate (EBC) and plasma before and after continuous positive airway pressure (CPAP) treatment. Materials and methods: Twenty healthy individuals (control) and 40 subjects with severe or moderate OSA were recruited to undergo CPAP treatment and evaluation in a sleep study. The Mt/N ratio in the EBC and blood were assayed by quantitative real-time polymerase chain reaction. Enzyme-linked immunosorbent assay was used to measure the protein concentration of PGC1-α in the EBC and plasma. All experiments were performed after 3 months of CPAP treatment in subjects with OSA. Results: We observed no noteworthy differences between the control and treatment groups. Moreover, there were no differences in the Mt/N ratio in the blood and plasma levels of PGC1-α in subjects with OSA before and after treatment. However, the Mt/N ratio and protein levels of PGC1-α in the EBC of OSA subjects were higher than those in the control group and returned to normal levels after CPAP treatment. Conclusions: We successfully treated subjects with OSA by CPAP, which restored the Mt/N ratio and levels of PGC1-α in the EBC.

Association of Obstructive Sleep Apnea with the Aging Process

Rationale: Evidence suggests that the physiopathologic consequences of obstructive sleep apnea (OSA) resemble those induced by aging. Some studies report that the deleterious effects associated with OSA might be age dependent. Objectives: To evaluate the association of OSA with the aging process and to determine whether this association is maintained across different age groups. Methods: This was an observational, prospective study including 599 patients with suspected OSA. Five hallmarks of aging were evaluated: alteration of cellular communication (serum CRP [C-reactive protein] concentration), deregulation of nutrient sensing (insulin resistance), telomere attrition (leukocyte telomeric length), mitochondrial dysfunction (leukocyte mitochondrial DNA copy number), and genomic instability (urinary 8-hydroxy-2-deoxyguanosine concentration). For age-stratified analyses, subjects were divided into four groups according to the apnea-hypopnea index (AHI) and the median age (50 yr): young patients without OSA (age < 50 yr old, AHI < 15 events/h), young patients with OSA (age < 50 yr old, AHI ⩾ 15 events/h), older patients without OSA (age ⩾ 50 yr old, AHI < 15 events/h), and older patients with OSA (age ⩾ 50 yr old, AHI ⩾ 15 events/h). Results: A dose-response relationship was found between the AHI, arousal index, and time during the night spent with an oxygen saturation less than 90% and the following hallmarks: alteration of cellular communication, deregulation of nutrient sensing, mitochondrial dysfunction, and genomic instability. Considering age-stratified analyses, OSA was associated with an increase in several hallmarks of aging in young patients, but no significant association of OSA was identified in older patients. Conclusions: In subjects under 50 years of age, OSA is associated with an increase in specific hallmarks of aging, independent of several known confounding factors.

Obstructive Sleep Apnea-hypopnea Syndrome as a Novel Potential Risk for Aging

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common sleep disorder, negatively influencing individuals' quality of life and socioeconomic burden. In recent years, OSAHS has been reported in not only constituting an aging-associated disease, but also in accelerating and/or potentiating aging mechanisms. However, the negative impacts of OSAHS on aging are underestimated because of low level of public awareness about this disease and high rates of undiagnosed cases, which are more critical in developing countries or economically disadvantaged regions. Hence, reviewing previously reported observations may assist scholars to better indicate that OSAHS is likely a novel potential risk for aging. Further understanding of the pathophysiological mechanism of OSAHS and its role in procession of aging may markedly highlight the importance of this common sleep disorder.

Sleep Apnoea Adverse Effects on Cancer: True, False, or Too Many Confounders?

Obstructive sleep apnoea (OSA) is a prevalent disorder associated with increased cardiovascular, metabolic and neurocognitive morbidity. Recently, an increasing number of basic, clinical and epidemiological reports have suggested that OSA may also increase the risk of cancer, and adversely impact cancer progression and outcomes. This hypothesis is convincingly supported by biological evidence linking certain solid tumours and hypoxia, as well as by experimental studies involving cell and animal models testing the effects of intermittent hypoxia and sleep fragmentation that characterize OSA. However, the clinical and epidemiological studies do not conclusively confirm that OSA adversely affects cancer, even if they hold true for specific cancers such as melanoma. It is likely that the inconclusive studies reflect that they were not specifically designed to test the hypothesis or because of the heterogeneity of the relationship of OSA with different cancer types or even sub-types. This review critically focusses on the extant basic, clinical, and epidemiological evidence while formulating proposed directions on how the field may move forward.

Searching for Inflammatory and Oxidative Stress Markers Capable of Clustering Severe Asthma

OBJECTIVE

Asthma inflammation may feature an imbalance between oxidative stress and antioxidant defenses. Oxidative stress induces propagation of airways inflammation and corticosteroid insensitivity contributing to poor asthma control, and frequent severe acute exacerbations. This study assessed inflammation and oxidative stress in severe asthmatic subjects and evaluated the possible correlations between inflammatory and oxidative stress markers investigated and asthma severity.

MATERIAL AND METHOD

Fifty-three patients with severe asthma, 11 patients with mild-moderate asthma and 12 healthy subjects were enrolled and underwent fractional exhaled nitric oxide (FENO) analysis and blood and sputum count cell collection. The content of mitochondrial DNA (MtDNA) and nuclear DNA (nDNA) was measured in exhaled breath condensate (EBC) by Real Time PCR and the ratio between MtDNA/nDNA was calculated. We detected MtDNA/nDNA in the EBC of severe asthmatics.

RESULTS

We found higher exhaled MtDNA/nDNA in severe asthmatics respectively compared to mild-moderate ones and to healthy controls (10.4±2.2 vs 7.9±2.5, p<0.05 and 10.4±2.2 vs 6.51±0.21, p<0.05). The level of exhaled MtDNA/nDNA was significantly higher in Non-T2 endotype severe asthmatics than T2 (14.07±10. 8 vs 6.5±5.5, p<0.05).

CONCLUSION

Oxidative stress marker (MtDNA/nDNA) is increased significantly with asthma severity and may be useful for endotyping severe asthma.

Obstructive Sleep Apnea and the Liver

Nonalcoholic fatty liver disease (NAFLD), a disorder of altered metabolic pathways, is increasing worldwide. Recent studies established obstructive sleep apnea (OSA) and chronic intermittent hypoxia (CIH) as NAFLD risk factors. Studies have ascertained that CIH is independently related to NAFLD. Continuous positive airway pressure (CPAP) shows inconsistent results regarding its efficacy in improving NAFLD. Observational, longer duration CPAP therapy studies have shown positive outcomes, whereas shorter duration, randomized controlled trials have shown no benefit. A multifaceted approach to NAFLD management with sufficiently longer duration of CPAP therapy may be beneficial in patients with moderate to severe OSA.

Recombinant human glucagon-like peptide-1 protects against chronic intermittent hypoxia by improving myocardial energy metabolism and mitochondrial biogenesis

BACKGROUND AND AIMS

Obstructive sleep apnea syndrome is a chronic disease associated with intermittent hypoxia (IH) and is an important risk factor for cardiovascular disease. Glucagon-like peptide (GLP-1) is a naturally occurring incretin used as a promising therapeutic agent in the treatment of acute myocardial infarction, dilated cardiomyopathy, and advanced heart failure. However, whether GLP-1 can protect against IH-induced cardiac injury is still unclear. Accordingly, in this study, we evaluated the effects of recombinant human GLP-1 (rhGLP-1) on cardiac health in mice.

METHODS

Mice were subjected to repetitive 5% O₂ for 30 s and 21% O₂ for 30 s, for a total of 8 h/day for 4 weeks. Subsequently, mice received subcutaneous injection of saline or rhGLP-1 (100 μg/kg, three times per day). Cardiac function, myocardial apoptosis and fibrosis, energy metabolism, and mitochondrial biogenesis were examined for evaluation of cardiac injury.

RESULTS

A reduction in diastolic function (E/A ratio) in mice exposed to IH was significantly reversed by rhGLP-1. IH induced marked cardiomyocyte apoptosis and myocardial fibrosis. Additionally, IH resulted in a shift from fatty acid to glucose metabolism in the myocardium with downregulation of peroxisome proliferator-activated receptor (PPAR) α and PPARγ. Moreover, IH caused a reduction in mitochondrial DNA (mtDNA) replication and transcription, together with reduced mtDNA content and impaired mitochondrial ultrastructure. These changes were abolished by rhGLP-1 via activation of PGC-1α and Akt signaling.

CONCLUSIONS

rhGLP-1 protects against IH-induced cardiac injury by improving myocardial energy metabolism and enhancing the early adaptive changes of mitochondrial biogenesis.

Moderating effects of sleep duration on diabetes risk among cancer survivors: analysis of the National Health Interview Survey in the USA

Background

Growing evidence suggests that cancer and diabetes may share common risk factors such as age, race/ethnicity, obesity, insulin resistance, sedentary lifestyle, smoking, and alcohol consumption. However, little is known about how habitual sleep duration (a known cardiometabolic risk factor) may affect the relationship between cancer and diabetes. The aim of this study was to investigate whether sleep duration moderated the relationship between history of cancer and diabetes.

Methods

Data were extracted from the National Health Interview Survey dataset from 2004 to 2013 containing demographics, chronic diseases, and sleep duration (N=236,406). Data were analyzed to assess the moderating effect of short and long sleep durations on cancer and diabetes mellitus.

Results

Our findings indicate that short sleep (odds ratio [OR] =1.07, 95% CI =1.03–1.11, P<0.001) and long sleep (OR =1.32, 95% CI =1.26–1.39, P<0.001) were associated with diabetes mellitus in fully adjusted models. However, only long sleep duration significantly moderated the relationship between cancer and diabetes (OR =0.88, 95% CI =0.78–0.98, P<0.05).

Conclusion

Our findings indicate that for cancer survivors, short sleep was associated with higher self-reported diabetes and long sleep duration may act as a buffer against diabetes mellitus, as the likelihood of self-reported diabetes was lower among cancer survivors who reported long sleep duration.

Impact

Findings from the current study have clinical and public health implications. Clinically, comprehensive sleep assessments and sleep interventions to improve sleep are needed for cancer survivors who have comorbid diabetes. Our findings can also spur public health reform to make sleep an important component of standard cancer survivorship care, as it reduces other chronic disease like diabetes.

Oxidative stress in chronic lymphocytic leukemia: still a matter of debate

There is a large body of evidence showing a strong correlation between carcinogenesis of several types of human tumors, including chronic lymphocytic leukemia (CLL), and oxidative stress (OS). The mechanisms by which OS may promote cancer pathogenesis have not been completely deciphered yet and, in CLL, as in other neoplasms, whether OS is a primary cause or simply a downstream effect of the disease is still an open question. It has been demonstrated that, in CLL, OS concomitantly results from increased reactive oxygen species (ROS) production, mainly ascribable to CLL cells mitochondrial activity, and impaired antioxidant defenses. Interestingly, OS evaluation in CLL patients, at diagnosis, seems to have a prognostic significance, thus getting new insights in the biological comprehension of the disease with potential therapeutic implications.

Association between mitochondrial DNA damage and ocular blood flow in patients with glaucoma

Background/Aims

We determined the relationship between tissue mean blur rate (MT) and mitochondrial dysfunction, represented by the mitochondrial/nuclear DNA (mtDNA/nDNA) ratio. We also investigated the usefulness of these biomarkers.

Methods

We assessed ocular blood flow in 123 eyes of 123 patients with open-angle glaucoma (OAG) and 37 control eyes of 37 healthy subjects by measuring MT in the optic nerve head with laser speckle flowgraphy. We measured mtDNA and nDNA with PCR, calculated the mtDNA/nDNA ratio and compared this ratio with MT using Spearman’s rank test. We used multiple regression analysis to further investigate the association between MT and glaucoma in the most severe group.

Results

The control and the patients with glaucoma had significant differences in the mtDNA/nDNA ratio, circumpapillary retinal nerve fibre layer thickness and MT. There was no significant relationship between the mtDNA/nDNA ratio and MT in patients with OAG overall or the female patients with OAG, but there was a significant relationship between the mtDNA/nDNA ratio and MT, temporal-MT and superior-MT in male patients with severe OAG (r=−0.46, p=0.03; r=−0.51, p=0.02; r=−0.61, p<0.01, respectively). Furthermore, we found that the mtDNA/nDNA ratio was an independent contributor to temporal-MT and superior-MT in these patients (p<0.01 and p=0.03, respectively).

Conclusion

We found that there was a significant relationship between the mtDNA/nDNA ratio and MT in male patients with severe OAG, suggesting that the mtDNA/nDNA ratio may be a new biomarker in glaucoma and may help research on the vulnerability of these patients to mitochondrial dysfunction.

The relationship between increased oxidative stress and visual field defect progression in glaucoma patients with sleep apnoea syndrome

PURPOSE

Sleep apnoea syndrome (SAS) is often associated with glaucoma, and intermittent hypoxia, present in SAS, can contribute to glaucoma pathogenesis. However, the relationships between SAS, high systemic oxidative stress and the speed of glaucoma progression are unclear. Thus, we investigated these relationships in glaucoma patients with and without SAS.

METHODS

Peripheral blood samples were collected from 166 eyes of 166 Japanese patients: 42 controls, 109 open-angle glaucoma (OAG) patients without SAS and 15 OAG patients with SAS. Prognostic factors for visual field defect progression were determined with logistic regression. Diacron reactive oxygen metabolites (dROM) and biological antioxidant potential (BAP) were measured with a free radical analyser. Clinical parameters were also recorded. Intergroup comparisons used the Mann-Whitney U test.

RESULTS

Multiple regression analysis showed that SAS was a statistically significant contributing factor to fast visual field defect progression, defined as mean deviation (MD) slope ≤-2.0 dB/Y (SAS: odds ratio (OR) = 14.48; p = 0.002). The non-SAS and SAS groups had similar age, sex, intraocular pressure (IOP), axial length and antiglaucoma drug use. The SAS group had a significantly higher dROM level (p = 0.001), BAP level (p = 0.038) and steeper MD slope (p = 0.001) than the non-SAS group.

CONCLUSION

Glaucoma patients with SAS have higher dROM, as well as steeper MD slope, than patients without SAS, suggesting that SAS may induce systemic oxidative stress and promote glaucomatous visual field defect progression.

Damage of Inner Ear Sensory Hair Cells via Mitochondrial Loss in a Murine Model of Sleep Apnea With Chronic Intermittent Hypoxia

Study Objectives

Investigating the exact pathophysiology of obstructive sleep apnea syndrome (OSAS)-induced hearing loss is critical. We sought to verify the hypothesis that a correlation exists between mitochondrial dysfunction in inner ear hair cells and the auditory dysfunction induced by chronic intermittent hypoxia (CIH) in a murine model of sleep apnea.

Methods

C57BL/6J adult male mice were randomized to 4 weeks of CIH (n = 12) or normoxia (Sham) (n = 12). Hearing threshold was determined by auditory brainstem response. The activity of mitochondria was compared between CIH and Sham mice. Histological assessment and transmission electron microscopy were performed for assessing morphologic changes in mitochondria. The number of mtDNA copies as well as the levels of PGC1-α, Tfam, and VDAC (voltage-dependent anion channel) were determined in the hair cells of CIH mice.

Results

We observed that hearing ability in CIH mice was impaired and hair-cell mitochondria in CIH mice were fewer compared to that in Sham and also displayed an aberrant morphology. The mRNA levels of PGC-1α and Tfam were higher in the CIH group than in the Sham group. Moreover, the expression of VDAC was increased in the tectorial membrane, the basilar membrane, and especially in the inner hair cells of CIH mice.

Conclusions

This study using CIH mice as a model for OSAS provides evidence of an association between OSAS and auditory function alteration, as well as of mitochondria being part of the pathophysiology of hearing impairment. Further investigation is required to determine whether mitochondria could serve as a valid target for preventive or therapeutic purposes.

Regulation of mitochondrial genome replication by hypoxia: The role of DNA oxidation in D-loop region

Mitochondria of mammalian cells contain multiple copies of mitochondrial (mt) DNA. Although mtDNA copy number can fluctuate dramatically depending on physiological and pathophysiologic conditions, the mechanisms regulating mitochondrial genome replication remain obscure. Hypoxia, like many other physiologic stimuli that promote growth, cell proliferation and mitochondrial biogenesis, uses reactive oxygen species as signaling molecules. Emerging evidence suggests that hypoxia-induced transcription of nuclear genes requires controlled DNA damage and repair in specific sequences in the promoter regions. Whether similar mechanisms are operative in mitochondria is unknown. Here we test the hypothesis that controlled oxidative DNA damage and repair in the D-loop region of the mitochondrial genome are required for mitochondrial DNA replication and transcription in hypoxia. We found that hypoxia had little impact on expression of mitochondrial proteins in pulmonary artery endothelial cells, but elevated mtDNA content. The increase in mtDNA copy number was accompanied by oxidative modifications in the D-loop region of the mitochondrial genome. To investigate the role of this sequence-specific oxidation of mitochondrial genome in mtDNA replication, we overexpressed mitochondria-targeted 8-oxoguanine glycosylase Ogg1 in rat pulmonary artery endothelial cells, enhancing the mtDNA repair capacity of transfected cells. Overexpression of Ogg1 resulted in suppression of hypoxia-induced mtDNA oxidation in the D-loop region and attenuation of hypoxia-induced mtDNA replication. Ogg1 overexpression also reduced binding of mitochondrial transcription factor A (TFAM) to both regulatory and coding regions of the mitochondrial genome without altering total abundance of TFAM in either control or hypoxic cells. These observations suggest that oxidative DNA modifications in the D-loop region during hypoxia are important for increased TFAM binding and ensuing replication of the mitochondrial genome.

Analysis of mitochondrial DNA alteration in new phenotype ACOS

BACKGROUND

Mitochondria contain their own DNA (MtDNA) that is very sensitive to oxidative stress and as a consequence could be damaged in quantity. Oxidative stress is largely recognized to play a key role in the pathogenesis of asthma and COPD and might have a role in the new intermediate phenotype ACOS (asthma-COPD overlap syndrome). The aim of this study was to investigate MtDNA alterations, as an expression of mitochondrial dysfunction, in ACOS and to verify whether they might help in the identification of this new phenotype and in its differentiation from asthma and COPD.

METHODS

Ten (10) ACOS according to Spanish guidelines, 13 ACOS according to GINA guidelines, 13 COPD, 14 asthmatic patients and ten normal subjects were enrolled. They further underwent a blood, induced sputum and exhaled nitric oxide collection. Content of MtDNA and nuclear DNA (nDNA) were measured in the blood cells of patients by Real Time PCR.

RESULTS

ACOS patients showed an increase of MtDNA/nDNA ratio. Dividing ACOS according to guidelines, those from the Spanish showed a higher value of MtDNA/nDNA compared to those from GINA/GOLD (92.69 ± 7.31 vs 80.68 ± 4.16). Spanish ACOS presented MtDNA/nDNA ratio closer to COPD than asthma. MtDNA was higher in asthmatic, COPD, GINA and Spanish ACOS patients compared to healthy subjects (73.30 ± 4.47-137.0 ± 19.45-80.68 ± 4.16-92.69 ± 7.31 vs 65.97 ± 20.56).

CONCLUSION

We found an increase of MtDNA/nDNA ratio in ACOS subjects that led us to conclude that there is presence of mitochondrial dysfunction in this disease, that makes it closer to COPD than to asthma. Although the MtDNA/nDNA ratio results are a useful marker for differential diagnosis from asthma, COPD and ACOS, further studies are needed to confirm the potentiality of MtDNA/nDNA ratio and to a better characterization of ACOS.