Creatine phosphokinase elevation in obstructive sleep apnea syndrome: an unknown association?

Serum Cardiac and Skeletal Muscle Marker Changes in Repetitive Breath-hold Diving

Background

Breath-hold diving (BH-diving) is associated to extreme environmental conditions, prolonged physical activity, and complex adaptation mechanisms to supply enough O₂ to vital organs. Consequently, one of the biggest effects could be an increased exercise-induced muscle fatigue, in both skeletal and cardiac muscles that can induce an increase of muscles injury markers including creatine kinase (CK), aspartate transferase (AST), and alanine transferase (ALT) when concerning the skeletal muscle, cardiac creatine kinase isoenzyme (CK-MBm) and cardiac troponin I (cTnI) when concerning the cardiac muscle, and lactate dehydrogenase (LDH) as index of muscle stress. The aim of this study is to investigate serum cardiac and skeletal muscle markers before and after a BH-diving training session.

Results

We found statistically significant increases of CK (T0: 136.1% p < 0.0001; T1: 138.5%, p < 0.0001), CK-MBm (T0: 145.1%, p < 0.0001; T1: 153.2%, p < 0.0001) LDH (T0: 110.4%, p < 0.0003; T1: 110.1%, p < 0.0013) in both T0 and T1 blood samples, as compared to basal value. AST showed a statistically significant increase only at T0 (106.8%, p < 0.0007) while ALT did not exhibit statistically significant changes. We did not find any changes in cTnI levels between pre-dive and post-dive samples.

Conclusions

Our data seem to indicate that during a BH-diving training session, skeletal and cardiac muscles react to physical effort releasing stress-related substances. Although the peculiar nature of BH-diving makes it difficult to understand if our results are related only to exercise induced muscle adaptation or whether acute hypoxia or a response to environmental changes (pressure) play a role to explain the observed changes, further studies are needed to better understand if these biomarker changes are linked to physical exercise or to acute hypoxia, or if both conditions play a role.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00349-z.

Obstructive Sleep Apnea, Hypoxia, and Nonalcoholic Fatty Liver Disease

Recent studies have demonstrated that obstructive sleep apnea (OSA) is associated with the development and evolution of nonalcoholic fatty liver disease (NAFLD), independent of obesity or other shared risk factors. Like OSA, NAFLD is a prevalent disorder associated with major adverse health outcomes: Patients with NAFLD may develop cirrhosis, liver failure, and hepatocellular carcinoma. One major finding that has emerged from these studies is that the OSA-NAFLD association is related to the degree of nocturnal hypoxemia in OSA. Animal models have therefore largely focused on intermittent hypoxia, a key manifestation of OSA, to shed light on the mechanisms by which OSA may give rise to the complex metabolic disturbances that are seen in NAFLD. Intermittent hypoxia leads to tissue hypoxia and can result in oxidative stress, mitochondrial dysfunction, inflammation, and overactivation of the sympathetic nervous system, among many other maladaptive effects. In such models, intermittent hypoxia has been shown to cause insulin resistance, dysfunction of key steps in hepatic lipid metabolism, atherosclerosis, and hepatic steatosis and fibrosis, each of which is pertinent to the development and/or progression of NAFLD. However, many intriguing questions remain unanswered: Principally, how aggressively should the clinician screen for NAFLD in patients with OSA, and vice versa? In this review, we attempt to apply the best evidence from animal and human studies to highlight the relationship between these two disorders and to advocate for further trials aimed at defining these relationships more precisely.

Diagnostic capability of biological markers in assessment of obstructive sleep apnea: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review is to evaluate the diagnostic value of biological markers (exhaled breath condensate, blood, salivary and urinary) in the diagnosis of OSA in comparison to the gold standard of nocturnal PSG.

METHODS

Studies that differentiated OSA from controls based on PSG results, without age restriction, were eligible for inclusion. The sample of selected studies could include studies in obese patients and with known cardiac disease. A detailed individual search strategy for each of the following bibliographic databases was developed: Cochrane, EMBASE, MEDLINE, PubMed, and LILACS. The references cited in these articles were also crosschecked and a partial grey literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies.

RESULTS

After a two-step selection process, nine articles were identified and subjected to qualitative and quantitative analyses. Among them, only one study conducted in children and one in adults found biomarkers that exhibit sufficiently satisfactory diagnostic accuracy that enables application as a diagnostic method for OSA.

CONCLUSION

Kallikrein-1, uromodulin, urocotin-3, and orosomucoid-1 when combined have enough accuracy to be an OSA diagnostic test in children. IL-6 and IL-10 plasma levels have potential to be good biomarkers in identifying or excluding the presence of OSA in adults.

Biomarkers associated with obstructive sleep apnea: A scoping review

The overall validity of biomarkers in the diagnosis of obstructive sleep apnea (OSA) remains unclear. We conducted a scoping review to provide assessments of biomarkers characteristics in the context of obstructive sleep apnea (OSA) and to identify gaps in the literature. A scoping review of studies in humans without age restriction that evaluated the potential diagnostic value of biological markers (blood, exhaled breath condensate, salivary, and urinary) in the OSA diagnosis was undertaken. Retained articles were those focused on the identification of biomarkers in subjects with OSA, the latter being confirmed with a full overnight or home-based polysomnography (PSG). Search strategies for six different databases were developed. The methodology of selected studies was classified using an adaptation of the evidence quality criteria from the American Academy of Pediatrics. Additionally the biomarkers were classified according to their potential clinical application. We identified 572 relevant studies, of which 117 met the inclusion criteria. Eighty-two studies were conducted in adults, 34 studies involved children, and one study had a sample composed of both adults and children. Most of the studies evaluated blood biomarkers. Potential diagnostic biomarkers were found in nine pediatric studies and in 58 adults studies. Only nine studies reported sensitivity and specificity, which varied substantially from 43% to 100%, and from 45% to 100%, respectively. Studies in adults have focused on the investigation of IL-6, TNF-α and hsCRP. There was no specific biomarker that was tested by a majority of authors in pediatric studies, and combinatorial urine biomarker approaches have shown preliminary promising results. In adults IL-6 and IL-10 seem to have a favorable potential to become a good biomarker to identify OSA.

Metabolic dysfunction in obstructive sleep apnea: A critical examination of underlying mechanisms

It has recently become clear that obstructive sleep apnea (OSA) is an independent risk factor for the development of metabolic syndrome, a disorder of defective energy storage and use. Several mechanisms have been proposed to explain this finding, drawing upon the characteristics that define OSA. In particular, intermittent hypoxia, sleep fragmentation, elevated sympathetic tone, and oxidative stress - all consequences of OSA - have been implicated in the progression of poor metabolic outcomes in OSA. In this review we examine the evidence to support each of these disease manifestations of OSA as a unique risk for metabolic dysfunction. Tissue hypoxia and sleep fragmentation are each directly connected to insulin resistance and hypertension, and each of these also may increase sympathetic tone, resulting in defective glucose homeostasis, excessive lipolysis, and elevated blood pressure. Oxidative stress further worsens insulin resistance and in turn, metabolic dysfunction also increases oxidative stress. However, despite many studies linking each of these individual components of OSA to the development of metabolic syndrome, there are very few reports that actually provide a coherent narrative about the mechanism underlying metabolic dysfunction in OSA.

Characterization of primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea

OBJECTIVES

We identified the primary symptoms leading to Chinese patients presenting at hospital with suspected obstructive sleep apnea (OSA) and studied the prevalence and characteristics of OSA in confirmed cases.

METHODS

We collected data on 350 consecutive patients (302 males and 43±11 years old) with suspected OSA who underwent overnight polysomnography (PSG).

RESULTS

Among all patients, rankings of primary symptoms that led to the patients presenting at hospital for PSG were observed apnea (33%), snoring alone (29%), choking/gasping (13%), daytime sleepiness (5%) and other (20%). For severe OSA, prevalence rate was 61%, apnea hypopnea index (AHI) was 64±18, age was 44±10 years old, body mass index (BMI) was 28±3.5 kg/m(2), and hypertension rate was 28%.

CONCLUSIONS

Self-awareness of symptoms led a majority of the patients to present at hospital in China. Compared to currently available case series studies, our results suggest that OSA patients in East Asian countries are characterized by higher prevalence and more severe apnea, younger age, poorer sleep quality, but less obesity and less comorbidity with hypertension, relative to countries in North America, South America and Europe.

Influence of constant positive airway pressure therapy on lipid storage, muscle metabolism and insulin action in obese patients with severe obstructive sleep apnoea syndrome

AIM

To observe the effect of constant positive airway pressure (CPAP) therapy on regional lipid deposition, muscle metabolism and glucose homeostasis in obese patients with obstructive sleep apnoea syndrome (OSAS).

METHODS

A total of 29 obese patients underwent assessment before and after a minimum of 12-week CPAP therapy. Abdominal adipose tissue was assessed using magnetic resonance imaging. Intramyocellular lipid (IMCL) and skeletal muscle creatine were assessed using (1)H-magnetic resonance spectroscopy. Fasting venous and arterial blood were collected. Glucose control was assessed using the homeostatic model. A subgroup of six patients were also evaluated for skeletal muscle pH, phosphocreatine (PCr) and mitochondrial function using (31)P-magnetic resonance spectroscopy. The sample was divided according to CPAP therapy, with regular users defined as a minimum nightly use of >or=4 h; 19 subjects were regular and 10 were irregular CPAP users.

RESULTS

Visceral adipose tissue volume and circulating leptin were reduced with regular CPAP use but not with irregular CPAP use. Regular CPAP use also produced an increase in skeletal muscle creatine and resting PCr and a decrease in muscle pH. Neither the regular nor irregular CPAP users showed any change in IMCL content, insulin sensitivity scores or mitochondrial function.

CONCLUSIONS

These data show that regular CPAP therapy reduces visceral adipose tissue and leptin and improves skeletal muscle metabolites. In obese patients with severe OSAS, regular CPAP use does not improve glucose control, suggesting that the influence of obesity on glucose control dominates over any potential effect of OSAS.