Inflammation in sleep apnea: an update

Bone metabolism parameters and inactive matrix Gla protein in patients with obstructive sleep apnea†

STUDY OBJECTIVES

The aim of this study was to investigate differences in dual-energy X-ray absorptiometry (DXA) parameters, trabecular bone score (TBS), bone turnover markers and inactive matrix Gla protein (dp-ucMGP) between patients with obstructive sleep apnea (OSA) and healthy controls.

METHODS

This study enrolled 53 male patients diagnosed with OSA, and 50 age- and body mass index (BMI)-matched control subjects. All participants underwent DXA imaging, TBS assessment and blood sampling for biochemical analysis of bone metabolism markers.

RESULTS

Mean apnea-hypopnea index (AHI) score of OSA patients was 43.8 ± 18.8 events/h. OSA patients had significantly higher plasma dp-ucMGP levels in comparison to controls (512.7 ± 71.9 vs. 465.8 ± 50.9 pmol/L, p < 0.001). OSA and control group did not significantly differ regarding standard DXA results, while TBS values were significantly lower in the OSA group (1.24 ± 0.17 vs. 1.36 ± 0.15, p < 0.001). AHI score was a significant independent correlate of plasma dp-ucMGP levels (β ± SE, 1.461 ± 0.45, p = 0.002). In addition, TBS retained a significant relationship with dp-ucMGP values (β ± SE, -93.77 ± 38.1, p = 0.001).

CONCLUSIONS

dp-ucMGP levels are significantly higher in patients with OSA and correlate with disease severity. In addition, TBS values in OSA patients are lower in comparison with the control group and decrease with disease severity.

The relationship between obstructive sleep apnea syndrome and obesity: A new perspective on the pathogenesis in terms of organ crosstalk

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a common disorder that has a major impact on public health. The connection between OSAS and obesity is very complex and likely represents an interaction between biological and lifestyle factors. Oxidative stress, inflammation and metabolic dysregulation are both actors involved in the pathogenesis of OSAS and obesity. Also, the current evidence suggests that gut microbiota plays a significant role in the emergence and progression of some metabolic disorders. When the relationship between OSAS and obesity is evaluated extensively, it is understood that they show mutual causality with each other, and that metabolic challenges such as impaired microbiota affect this bidirectional organ interaction, and by ensuing organ injury.

OBJECTIVES

The aim of this study is to investigate the association between OSAS and obesity, and the effect of "organ crosstalk" on the pathogenesis of the relationship and to contribute to the diagnosis and treatment options in the light of current data.

DATA SOURCE

We performed an electronic database search including PubMed, EMBASE and Web of Science. We used the following search terms: OSAS, obesity, inflammation, metabolic dysregulation and gut microbiota.

CONCLUSION

Obesity and OSAS adversely affect many organs and systems. Besides the factors affecting the diagnosis of the OSAS-obesity relationship, mutual organ interactions among the respiratory system, adipose tissue and intestines should not be ignored for prevention and treatment of OSAS and obesity. Comprehensive clinical trials addressing the efficacy and efficiency of current or potential treatments on therapeutic applications in the OSAS-obesity relationship are needed.

Treatment of obstructive sleep apnea with CPAP improves chronic inflammation measured by neutrophil-to-lymphocyte ratio

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with chronic inflammation likely triggered by nocturnal, intermittent hypoxemia and increased adrenergic tone. The neutrophil-to-lymphocyte ratio (NLR) was recently described as a measure of subclinical systemic inflammation. Studies on the effect of continuous positive airway pressure (CPAP) therapy in OSA on subclinical inflammation measured by NLR are lacking. We hypothesize that NLR levels would improve as chronic inflammation diminishes in patients with OSA treated with CPAP.

METHODS

We retrospectively reviewed patients in whom OSA was diagnosed and who were treated with CPAP therapy. Complete blood count (CBC) were obtained pretreatment and posttreatment for calculation of NLR, which was calculated by dividing the number of neutrophils by the number of lymphocytes. Patients with conditions known to affect NLR such as chronic infections, inflammatory diseases, active cardiovascular disease, and malignancies were excluded from the study. CPAP adherence downloads were obtained for all patients.

RESULTS

Out of 184 patients in whom OSA was diagnosed and who were treated with CPAP, 109 met our study criteria, including baseline polysomnogram, baseline and posttreatment CBC, and available adherence download. We compared the NLR before and after treatment with CPAP. There was a significant difference in NLR before and after treatment with CPAP (P < .0001). There was also a significant difference in apnea-hypopnea index before and after treatment (P < .0001). We also assessed the relationship between CPAP adherence (percentage of days used for > 4 hours) and the change in NLR. NLR decreased significantly in both the adherent (CPAP use ≥ 70% of days; P = .014) and nonadherent groups (CPAP use < 70% of days; P = .0003). Finally, we noticed a significant direct correlation between CPAP adherence beyond 70% and the change in NLR (ΔNLR) (P = .046) in patients who had ≥ 70% adherence with CPAP, which was not observed in patients with < 70% adherence.

CONCLUSIONS

The NLR may be a useful marker for monitoring improvement, as CPAP had a desirable effect on the chronic inflammation induced by OSA when measured by NLR in this study. Our results specifically suggest that the NLR values decrease significantly in patients using CPAP regardless of adherence, but with a more direct relationship in those who use it beyond 70% of days, at least 4 hours a day.

Circulating P-Selectin Glycoprotein Ligand 1 and P-Selectin Levels in Obstructive Sleep Apnea Patients

Purpose

Obstructive sleep apnea (OSA) is characterized by chronic intermittent hypoxia which induces inflammation in blood vessels leading to the development of cardiovascular comorbidities. Several studies implicated the role of P-selectin in vascular inflammation of OSA. P-selectin glycoprotein ligand 1 (PSGL-1) is the main activator for P-selectin and is involved in immune cell trafficking. However, PSGL-1 has not been analyzed in OSA. The aim of the study was to investigate plasma PSGL-1 and P-selectin levels to have a deeper understanding on their interaction in obstructive sleep apnea.

Methods

Fifty-one untreated patients with OSA and 42 non-OSA controls were recruited. Plasma PSGL-1 levels were determined in evening and morning samples, P-selectin levels were analyzed in morning samples using commercially available ELISA kits. Polysomnography was performed in all participants. OSA was defined by an apnea–hypopnea index ≥ 5/h.

Results

PSGL-1 levels did not differ between controls and OSA patients either in the evening or in the morning. Although, there was no difference between controls (16.9/6.8–40.8 ng/ml) and patients with OSA (19.6/8.4–56.8, p = 0.24), patients with severe OSA had increased plasma P-selectin levels (25.6/8.4–56.8 ng/ml) compared to mild OSA patients (14.1/8.5–35.3 ng/ml, p = 0.006) and controls (p = 0.03).

Conclusions

P-selectin expression relates to disease severity suggesting a pathophysiological role in endothelial cell activation. PSGL-1 levels are unaltered in OSA, suggesting an alternative activation pathway for P-selectin in OSA.

Oropharyngeal Microbiome in Obstructive Sleep Apnea: Decreased Diversity and Abundance

STUDY OBJECTIVES

To explore and analyze diversity and abundance of oropharyngeal microbiota in patients with obstructive sleep apnea (OSA).

METHODS

This was a cross-sectional study. Middle-aged men, suspected to have OSA, referred to full-night polysomnography, and willing to provide oropharyngeal swab samples, were consecutively enrolled. OSA severity was assessed by apnea-hypopnea index (AHI) as non-OSA (AHI < 5 events/h) and OSA (AHI ≥ 15 events/h). Bacterial DNA of oropharyngeal samples was extracted and quality test performed. Oropharyngeal microbiota was analyzed using 16S ribosomal DNA (rDNA) sequencing, and bioinformatic analysis carried out after sequencing.

RESULTS

Samples from 51 men (25 in the non-OSA group and 26 in the OSA group) were sent for examination. Of these, 40 samples were found to have sufficient concentration of DNA and were analyzed for bioinformatics. In alpha diversity analysis, the OSA group exhibited significantly lower sobs (198.33 ± 21.71 versus 216.57 ± 26.21, P = .022), chao (221.30 ± 26.62 versus 243.86 ± 26.20, P = .014), ace (222.17 ± 27.15 versus 242.42 ± 25.81, P = .028) and shannon index (3.14 ± 0.23 versus 3.31 ± 0.26, P = .035), suggesting a reduction in microbial species diversity. We further divided participants into non-OSA, moderate OSA, and severe OSA groups and observed a significant decrease in the bacterial biodiversity of OSA groups compared with the non-OSA group, with the most significant decrease occurring in the moderate OSA group. Principal coordinate analysis showed two extremely different oropharyngeal microbial communities in non-OSA and OSA groups. More interestingly, proportion of Neisseria was slightly higher in the severe OSA group (20.64%), followed by the moderate OSA and non-OSA groups (12.57% and 9.69%, respectively). Glaciecola was not detected in the OSA groups compared to the non-OSA group (0 versus 0.772 ± 0.4754, P < .001).

CONCLUSIONS

Middle-aged men with OSA showed less oropharyngeal species diversity and altered abundance, on which further confirmation is warranted.

Does nesfatin-1 influence the hypothalamic–pituitary–gonadal axis in adult males with obstructive sleep apnoea?

There is growing evidence that obstructive sleep apnoea (OSA) influences the hypothalamic–pituitary–gonadal axis (HPG axis) in men. The aim of the study was to assess the association of nesfatin-1 with HPG axis disturbances in OSA. This is a prospective study with consecutive enrolment. It comprises 72 newly diagnosed OSA patients ((AHI: apnoea-hypopnea index) 18 subjects: 5 ≤ AHI < 15; 24: 15 ≤ AHI < 30; 30: AHI ≥ 30) and a control group composed of 19 patients (AHI < 5). All patients underwent polysomnography and fasting blood collection for nesfatin-1, testosterone, luteinising hormone (LH), high-sensitivity C-reactive protein (hsCRP), aspartate transaminase (AST), alanine aminotransferase (ALT), creatinine and glucose. Groups had similar levels of LH, nesfatin-1 and testosterone (p = 0.87; p = 0.24; p = 0.08). Nesfatin-1 was not correlated to LH (p = 0.71), testosterone (p = 0.38), AHI (p = 0.34) or the oxygen desaturation index (ODI) (p = 0.69) either in the whole group, or in sub-groups. The study did not reveal any association between the HPG axis and nesfatin-1 in OSA adult males. It is possible that nesfatin-1 is not a mediator of HPG axis disturbances in adult patients with OSA.

Fatigue, Sleep, and Autoimmune and Related Disorders

Profound and debilitating fatigue is the most common complaint reported among individuals with autoimmune disease, such as systemic lupus erythematosus, multiple sclerosis, type 1 diabetes, celiac disease, chronic fatigue syndrome, and rheumatoid arthritis. Fatigue is multi-faceted and broadly defined, which makes understanding the cause of its manifestations especially difficult in conditions with diverse pathology including autoimmune diseases. In general, fatigue is defined by debilitating periods of exhaustion that interfere with normal activities. The severity and duration of fatigue episodes vary, but fatigue can cause difficulty for even simple tasks like climbing stairs or crossing the room. The exact mechanisms of fatigue are not well-understood, perhaps due to its broad definition. Nevertheless, physiological processes known to play a role in fatigue include oxygen/nutrient supply, metabolism, mood, motivation, and sleepiness-all which are affected by inflammation. Additionally, an important contributing element to fatigue is the central nervous system-a region impacted either directly or indirectly in numerous autoimmune and related disorders. This review describes how inflammation and the central nervous system contribute to fatigue and suggests potential mechanisms involved in fatigue that are likely exhibited in autoimmune and related diseases.

Magnitude and Determinants of Patients at Risk of Developing Obstructive Sleep Apnea in a Non-Communicable Disease Clinic

Background and Objective: Obstructive sleep apnea (OSA) is a common chronic disorder worldwide, which can adversely affect the cardiovascular system among non-communicable disease (NCD) patients. It is underdiagnosed—or rather not diagnosed—in primary care settings due to the costly diagnostic techniques involved. This study aimed to assess the number of study participants at risk of developing OSA and to assess and quantify the risk factors associated with this disorder. Materials and Methods: A cross-sectional study was performed in an NCD clinic of a rural health training center, Karikalampakkam, Puducherry of South India from August 2018 to October 2018. A Modified Berlin Questionnaire (MBQ) was used to screen the study participants at risk for OSA. Four-hundred-and-seventy-three people aged 18 years and above were included in the study, using systematic random sampling. Respondents’ socio-demographic and morbidity characteristics, as well as clinical and anthropometric parameters including body weight, height, blood pressure, neck, hip and waist circumference were collected. Data was captured using Epicollect5 and analyzed using SPSS version 20.0. Results: One-fourth (25.8%) of the respondents were at high risk of developing OSA. In terms of gender, 27.9% of the men and 23.8% of the women were at high risk for OSA. In univariate analyses, the risk of developing OSA was significantly associated with a history of diabetes mellitus, hypertension, dyslipidemia and gastro-esophageal reflux disease, weight, body mass index, neck, waist and hip circumference, waist–hip ratio, and systolic and diastolic blood pressure. Multivariate logistic regression analysis showed that a history of dyslipidemia (aOR, 95% CI = 2.34, 1.22–4.48), body mass index (aOR, 95% CI = 1.15, 1.06–1.22) and waist circumference (aOR, 95% CI = 1.10, 1.07–1.14) emerged as significant predictors of risk for OSA. Conclusions: A considerable proportion of NCD patients with easily detectable attributes are at risk of developing OSA, but still remain undiagnosed at a primary health care setting. The results obtained using MBQ in this study were comparable to studies performed using polysomnography. Dyslipidemia, body mass index and waist circumference were independent risk factors for predicting a risk of developing OSA. Prospective studies are needed to confirm whether a reduction in these risk factors could reduce the risk for OSA.

MicroRNA expression profile is altered in the upper airway skeletal muscle tissue of patients with obstructive sleep apnea-hypopnea syndrome

Objective

To investigate the involvement of microRNAs (miRNAs) in the pathogenesis of obstructive sleep apnea-hypopnea syndrome (OSAHS).

Methods

In this study, we investigated miRNA profiles in the upper airway (UA) skeletal muscles of four patients with OSAHS and four matched controls using the miRCURY miRNA array. In another cohort of 12 OSAHS cases and 7 controls, the mRNA expression levels of interleukin (IL)-6 and Lin-28 homolog A (Lin28A), targets of the downregulated let-7 family members, were measured by real-time quantitative-PCR. The potential targets of the miRNAs were predicted by miRNA target prediction databases miRanda, Microcosm, and Targetscan.

Results

The array identified 370 differentially expressed miRNAs, of which 181 were upregulated and 189 were downregulated in OSAHS patients (based on a fold-change >2.0 and p < 0.05). Upregulation of IL-6 and Lin28A was validated by quantitative reverse transcription PCR. The 612 targets predicted by all three algorithms were subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The results revealed perturbations in signaling pathways and cellular functions.

Conclusion

This study demonstrated profoundly altered miRNA expression profiles in upper airway muscular tissues of patients with OSAHS, which might contribute to the formation and development of OSAHS.

Decreased Levels of Anti-Aging Klotho in Obstructive Sleep Apnea

The klotho protein is secreted primarily by the kidneys. It is responsible for phosphate homeostasis and has an anti-aging, anti-inflammatory, and anti-oxidative stress role. Obstructive sleep apnea (OSA) is associated with an enhanced systemic inflammation and oxidative stress, but mechanisms that regulate these processes are poorly understood. The aim of the study was to investigate the plasma levels of klotho in OSA. Twenty-one previously untreated patients with OSA (56 ± 13 years, 12 males) and 41 non-OSA control volunteers (48 ± 16 years, 8 males) participated in the study. Medical history has been taken; participants filled out the Epworth Sleepiness Scale. C-reactive protein and renal function, glucose and lipid profile measurements were performed in sera; klotho was determined in citrate-treated plasma samples. Levels of plasma klotho were decreased in OSA (519.1 ± 164.9 pg/mL) versus controls (700.8 ± 431.4 pg/mL, p = 0.02). Reduced klotho concentrations were associated with markers of overnight hypoxemia determined with O₂ desaturation index (r = -0.31, p = 0.01), percentage of sleep time spent with saturation <90% (r = -0.41, p < 0.01), and minimal saturation during sleep (r = 0.33, p = 0.01). Interestingly, there was no relationship with apnea-hypopnea index, total sleep time, or arousal index (all p > 0.05). Significant association was also found between low plasma klotho levels and the presence of hypertension (p < 0.05). Our results suggest that chronic intermittent hypoxia reduces the levels of klotho in OSA, which may contribute to the development of hypertension. Decreased klotho levels may play a role in enhanced systemic inflammation in OSA and may be a future target for drug development.

Intermittent hypoxia impairs uterine artery function in pregnant mice

KEY POINTS

Obstructive sleep apnoea (OSA) is a chronic condition characterized by intermittent hypoxia that induces oxidative stress and inflammation leading to cardiovascular disease. Women can develop OSA during late pregnancy, which is associated with adverse maternal and fetal outcomes. However, the effects of OSA throughout pregnancy on fetoplacental outcomes are unknown. Using a mouse model of intermittent hypoxia, we evaluated main uterine artery function, spiral artery remodelling, circulating angiogenic and anti-angiogenic factors, and placental hypoxia and oxidative stress at gestational day 14.5 in pregnant mice. Gestational intermittent hypoxia increased placental weight but decreased fetal weight, impaired uterine artery function, increased circulating angiogenic and anti-angiogenic factors, and induced placental hypoxia and oxidative stress, but had no impact on spiral artery remodelling. Our results suggest that pregnant women experiencing OSA during pregnancy could be at risk of maternal and fetal complications.

ABSTRACT

Obstructive sleep apnoea (OSA) is characterized by chronic intermittent hypoxia (IH) and is associated with increased inflammation, oxidative stress and endothelial dysfunction. OSA is a common sleep disorder and remains under-diagnosed; it can increase the risk of adverse maternal and fetal outcomes in pregnant women. We investigated the effects of gestational IH (GIH) on uterine artery function, spiral artery remodelling and placental circulating angiogenic and anti-angiogenic factors in pregnant female mice. WT C57BL/6 mice (8 weeks) were exposed to either GIH ( F I O 2 12%) or intermittent air ( F I O 2 21%) for 14.5 days of gestation. Exposure to GIH reduced fetal weight but increased placental weight. GIH dams had higher plasma levels of oxidative stress (8-isoprostane) and inflammatory markers (tumour necrosis factor-α). GIH significantly reduced uterine artery function as indicated by reduced endothelium-dependent vasodilatation and enhanced vasoconstriction. Plasma levels of placental angiogenic and anti-angiogenic markers (soluble fms-like tyrosine kinase-1, soluble endoglin, angiogenic placental growth factor-2 and vascular endothelial growth factor) were higher in pregnant mice exposed to GIH. There was no evidence of impaired spiral artery remodelling based on immunostaining with α-smooth muscle actin and cytokeratin-7, and also by measurements of lumen area. Immunostaining for markers of hypoxia (pimonidazole) and oxidative stress (4-hydroxynonenal) were higher in mice exposed to GIH. Our data show that GIH adversely affects uterine vascular function and may be a mechanism by which gestational OSA leads to adverse maternal and fetal outcomes.

IL-33 Mediated Inflammation in Chronic Respiratory Diseases-Understanding the Role of the Member of IL-1 Superfamily

Interleukin 33 (IL-33) is an alarmin cytokine from the IL-1 family. IL-33 is localized in the nucleus and acts there as a gene regulator. Following injury, stress or cell death, it is released from the nucleus, and exerts its pro-inflammatory biological functions via the transmembrane form of the ST2 receptor, which is present mainly as attached to immune cells. In recent years, IL-33 became a focus of many studies due to its possible role in inflammatory disorders. Among respiratory disorders, the contribution of IL-33 to the development of asthma, in particular, has been most identified. Increased level of IL-33 in lung epithelial cells and blood serum has been observed in asthma patients. The IL-33/ST2 interaction activated the Th2 mediated immune response and further production of many pro-inflammatory cytokines. Single nucleotide polymorphisms in the IL-33 gene cause a predisposition to the development of asthma. Similarly, in chronic pulmonary obstructive disease (COPD), both increased expression of IL-33 and the ST2 receptor has been observed. Interestingly, cigarette smoke, a key inducer of COPD, not only activates IL-33 production by epithelial and endothelial cells, but also induces the expression of IL-33 in peripheral blood mononuclear cells. Knowledge regarding its contribution in other respiratory disorders, such as obstructive sleep apnea, remains greatly limited. Recently it was shown that IL-33 is one of the inflammatory mediators by which levels in blood serum are increased in OSA patients, compared to healthy control patients. This mini review summarizes current knowledge on IL-33 involvement in chosen chronic respiratory disorders and proposes this interleukin as a possible link in the pathogenesis of these diseases.

Beneficial effects of a lifestyle intervention program on C-reactive protein: impact of cardiorespiratory fitness in obese adolescents with sleep disturbances

The objectives of this study were to assess the relationship between inflammation and obstructive sleep apnea (OSA) and determine whether the lifestyle program's effects on inflammatory markers are associated with changes in anthropometric parameters, cardiorespiratory fitness, sleep duration, and OSA severity in severely obese adolescents. Participants were aged 14.6 (SD 1.2) yr, with a body mass index (BMI) of 40.2 (SD 6.5) kg/m². Sleep, anthropometric parameters, glucose metabolism, inflammatory profile, and cardiorespiratory fitness [V̇o_2peak relative to body weight (V̇o_2peakBW) and fat-free mass (V̇o_2peakFFM)] were assessed at admission and at the end of a 9-mo lifestyle intervention program (LIP). Associations between C-reactive protein (CRP) concentrations and BMI, sex, oxygen desaturation index (ODI), sleep fragmentation, total sleep time (TST), and V̇o_2peak were assessed via ANCOVA. Twenty-three subjects completed the study. OSA subjects ( n = 13) exhibited higher CRP concentrations and a trend for higher BMI than non-OSA subjects ( P = 0.09) at admission. After intervention, OSA was normalized in six subjects, and CRP significantly decreased in the OSA group and in the whole population. In both groups, leptin levels significantly decreased, whereas adiponectin concentrations increased. At admission, BMI adjusted for sex, arousal index, ODI, TST, and V̇o_2peakBW was associated with CRP levels (adjusted r² = 0.32, P < 0.05). The decrease in CRP concentrations postintervention was associated with enhanced V̇o_2peakFFM adjusted for sex, weight loss, and changed sleep parameters (adjusted r² = 0.75, P < 0.05). Despite higher amounts of CRP in OSA subjects, obesity severity outweighs the proinflammatory effects of OSA, short sleep duration, and low cardiorespiratory fitness. However, enhanced cardiorespiratory fitness is associated with the decrease of inflammation after controlling for the same parameters.

Oral Health and Oral Health-Related Quality of Life in Children With Obstructive Sleep Apnea

STUDY OBJECTIVES

This aim of this study was to evaluate oral health and oral health-related quality of life (OHRQoL) in children with obstructive sleep apnea (OSA).

METHODS

This cross-sectional study involved 31 children who had baseline polysomnography studies and in whom a diagnosis of OSA was made by a sleep physician. They were evaluated against 36 control patients who, based on parent responses to the Pediatric Sleep Questionnaire, were at very low risk for having sleep problems. The mean age of the cohort was 12.3 ± 2.7 years. The oral health status was examined clinically and recorded using caries and periodontal indices. OHRQoL was measured using the Child Oral Health Impact Profile (COHIP) questionnaires.

RESULTS

Children with OSA had significantly worsened oral health compared to control patients as evidenced by more caries (15.2 and 3.2, respectively; P < .001) and more periodontitis. Periodontitis severity was measured by the presence of bleeding on probing, (87% versus 30%, P < .001) and higher number of sites with abnormally deep periodontal probing depths (2.7 versus 0.3, P < .001). The COHIP scores were significantly higher among children with OSA compared to control patients, (29.7 versus 11.8, P < .001) consistent with poorer OHRQoL.

CONCLUSIONS

This study suggests that in children OSA may have a significant association with poorer oral health when compared to control patients without sleep problems, and that their oral health status may have a negative effect on their quality of life. Increased awareness regarding the oral health effects of sleep-disordered breathing in the medical and dental community is needed.

Age-dependent hypoxia-induced PD-L1 upregulation in patients with obstructive sleep apnoea

BACKGROUND AND OBJECTIVE

In obstructive sleep apnoea (OSA), intermittent hypoxia (IH) compromises immune surveillance through the upregulation of the programmed cell death-1 (PD-1) receptor and its ligand (PD-L1). Because the risk of OSA-related cancer depends on age, we assessed PD-L1/PD-1 expression in middle-aged and older patients with OSA as well as in a murine model.

METHODS

PD-L1 expression was studied in 41 patients with severe OSA and 40 healthy volunteers (HV), divided into two groups (≤55 and >55 years of age). We used flow cytometry, quantitative PCR (qPCR) and ELISA to determine PD-L1 expression on monocytes and plasma PD-L1 protein levels. Moreover, we analysed PD-L1 expression on an in vivo IH model with old and young mice.

RESULTS

In subjects up to 55 years of age, severe OSA increased PD-L1 surface protein and mRNA level expression on monocytes and soluble-PD-L1 protein concentration in plasma compared to HV. PD-L1 and hypoxia-induced factor (HIF)-1α expression correlated with age in HV, whereas in patients with OSA there was a negative relationship. In the mice exposed to IH, PD-L1 expression on F4/80+ splenocytes was also only increased in young animals. HIF-1α expression was significantly higher in patients with OSA than in HV in subjects up to 55 years of age, while PD-L1 expression in monocytes was related to HIF-1α expression in young patients with OSA.

CONCLUSION

PD-L1 upregulation in patients with OSA as a consequence of HIF-1α activation occurs mainly in young patients. In older patients with OSA, upregulation was not detected, possibly due to impaired oxygen sensitivity.

Connexins and Atrial Fibrillation in Obstructive Sleep Apnea

PURPOSE OF THE REVIEW

To summarize the potential interactions between obstructive sleep apnea (OSA), atrial fibrillation (AF), and connexins.

RECENT FINDINGS

OSA is highly prevalent in patients with cardiovascular disease, and is associated with increased risk for end-organ substantial morbidities linked to autonomic nervous system imbalance, increased oxidative stress and inflammation, ultimately leading to reduced life expectancy. Epidemiological studies indicate that OSA is associated with increased incidence and progression of coronary heart disease, heart failure, stroke, as well as arrhythmias, particularly AF. Conversely, AF is very common among subjects referred for suspected OSA, and the prevalence of AF increases with OSA severity. The interrelationships between AF and OSA along with the well-known epidemiological links between these two conditions and obesity may reflect shared pathophysiological pathways, which may depend on the intercellular diffusion of signaling molecules into either the extracellular space or require cell-to-cell contact. Connexin signaling is accomplished via direct exchanges of cytosolic molecules between adjacent cells at gap membrane junctions for cell-to-cell coupling. The role of connexins in AF is now quite well established, but the impact of OSA on cardiac connexins has only recently begun to be investigated. Understanding the biology and regulatory mechanisms of connexins in OSA at the transcriptional, translational, and post-translational levels will undoubtedly require major efforts to decipher the breadth and complexity of connexin functions in OSA-induced AF.

SUMMARY

The risk of end-organ morbidities has initiated the search for circulating mechanistic biomarker signatures and the implementation of biomarker-based algorithms for precision-based diagnosis and risk assessment. Here we summarize recent findings in OSA as they relate to AF risk, and also review potential mechanisms linking OSA, AF and connexins.

Cardiac rhythm disorders in obstructive sleep apnea

Obstructive sleep apnea (OSA) is common among patients with cardiac rhythm disorders. OSA may contribute to arrhythmias due to acute mechanisms, such as generation of negative intrathoracic pressure during futile efforts to breath, intermittent hypoxia, and surges in sympathetic activity. In addition, OSA may lead to heart remodeling and increases arrhythmia susceptibility. Atrial distension and remodeling, that has been shown to be associated with OSA, is a well-known anatomical substrate for atrial fibrillation (AF). AF is the arrhythmia most commonly described in patients with OSA. Several observational studies have shown that the treatment of OSA with continuous positive airway pressure (CPAP) reduces recurrence of AF after electrical cardioversion and catheter ablation. There is also evidence that nocturnal hypoxemia, a hallmark of OSA, predicts sudden cardiac death (SCD) independently of well-established cardiovascular risk factors. Among patients with an implantable cardiac defibrillator, those with OSA have a higher risk of receiving treatment for life-threatening arrhythmias. Nocturnal hypoxemia may also increase vagal tone, which increases susceptibility to bradycardic and conduction rhythm disorders that have also been described in patients with OSA. In conclusion, there are several biological pathways linking OSA and increased cardiac arrhythmogenesis propensity. However, the independent association is derived from observational studies and the direction of the association still needs clarification due to the lack of large clinical trials. This review focuses on the current scientific evidence linking OSA to cardiac rhythm disorders and point out future directions.

Effect of mandibular advancement therapy on inflammatory and metabolic biomarkers in patients with severe obstructive sleep apnoea: a randomised controlled trial

Systemic inflammation and metabolic disorders are among the mechanisms linking obstructive sleep apnoea (OSA) and cardiovascular disease (CVD). In 109 patients with severe OSA and no overt CVD, biomarkers of inflammation (C reactive protein, interleukin-6, tumour necrosis factor-α and its receptors, adiponectin, leptin and P-selectin), glucose and lipid metabolism, and N-terminal pro-brain natriuretic peptide, were measured before and after 2 months of treatment with a mandibular advancement device (MAD) (n=55) or a sham device (n=54). MAD reduced the Apnoea-Hypopnoea Index (p<0.001) but had no effect on circulating biomarkers compared with the sham device, despite high treatment adherence (6.6 hour/night). TRIAL REGISTRATION NUMBER: NCT01426607.

Obstructive Sleep Apnea: From Intermittent Hypoxia to Cardiovascular Complications via Blood Platelets

Obstructive sleep apnea is a chronic condition characterized by recurrent episodes of apneas or hypopneas during sleep leading to intermittent hypoxemia and arousals. The prevalence of the sleep disordered breathing is estimated that almost 50% of men and 24% of women suffer from moderate to severe form of the disorder. Snoring, collapse of upper airways and intermittent hypoxia are main causes of smoldering systemic inflammation in patients suffering from obstructive sleep apnea. The systematic inflammation is considered one of the key mechanisms leading to significant cardiovascular complications. Blood platelets, formerly not even recognized as cells, are currently gaining attention as crucial players in the immune continuum. Platelet surface is endowed with receptors characteristic for cells classically belonging to the immune system, which enables them to recognize pathogens, immune complexes, and interact in a homo- and heterotypic aggregates. Platelets participate in the process of transcellular production of bioactive lipids by delivering both specific enzymes and substrate molecules. Despite their lack of nucleus, platelets synthetize proteins in a stimuli-dependent manner. Atherosclerosis and consequent cardiovascular complications result from disruption in homeostasis of both of the platelet roles: blood coagulation and inflammatory processes modulation. Platelet parameters, routinely evaluated as a part of complete blood count test, were proposed as markers of cardiovascular comorbidity in patients with obstructive sleep apnea. Platelets were found to be excessively activated in this group of patients, especially in obese subjects. Persistent activation results in enhanced spontaneous aggregability and change in cytokine production. Platelet-lymphocyte ratio was suggested as an independent marker for cardiovascular disease in obstructive sleep apnea syndrome and continuous positive air pressure therapy was found to have an impact on platelet parameters and phenotype. In this literature review we summarize the current knowledge on the subject of platelets involvement in obstructive sleep apnea syndrome and consider the possible pathways in which they contribute to cardiovascular comorbidity.

Adropin and Inflammation Biomarker Levels in Male Patients With Obstructive Sleep Apnea: A Link With Glucose Metabolism and Sleep Parameters

STUDY OBJECTIVES

The main objectives of the study were to determine plasma adropin, systemic inflammation biomarker levels, and glucose metabolism parameters in patients with moderate and severe obstructive sleep apnea (OSA) compared to healthy controls.

METHODS

In this study, we included 50 male patients with OSA (25 moderate and 25 severe) and 25 age- and sex-matched control subjects. All subjects underwent fasting sampling of peripheral blood for laboratory analyses.

RESULTS

Adropin plasma levels were significantly lower in the severe OSA group in comparison with the moderate and control groups (4.50 ± 1.45 versus 6.55 ± 1.68 versus 8.15 ± 1.79 ng/mL, P < .001). Plasma biomarkers of systemic inflammation were significantly increased in patients with moderate OSA (interleukin [IL]-6 and tumor necrosis factor alpha [TNF-α]) and severe OSA (IL-6, TNF-α, high-sensitivity C-reactive protein) when compared with controls (P < .001). Adropin levels showed a significant negative correlation with IL-6 (r = -.419, P < .001), TNF-α (r = -.540, P < .001), fasting glucose (r = -.331, P = .004), hemoglobin A1c (r = -.438, P < .001), homeostatic model assessment insulin resistance index (r = -.213, P = .046), and polysomnographic parameters including apnea-hypopnea index (r = -.615, P < .001) and oxygen desaturation index (r = -.573, P < .001). A multivariate regression analysis showed that plasma adropin remained as a significant negative predictor of severe OSA status, when adjusted for age and body mass index and computed along with other inflammatory biomarkers in the regression model (odds ratio 0.069, 95% confidence interval 0.009-0.517, P = .009).

CONCLUSIONS

Plasma adropin concentrations significantly correlate with indices of disease severity in patients with OSA, suggesting that adropin potentially plays an important role in the complex pathophysiology of the disease.

Risk of gallstones in patients with obstructive sleep apnea: a nationwide observational cohort study

PURPOSE

To assess the association between obstructive sleep apnea (OSA) and gallstones.

METHODS

We identified 3827 patients aged ≥ 20 years with OSA between 2000 and 2010 from the Longitudinal Health Insurance Research Database 2000 (LHID2000) as the study cohort. The beneficiaries without OSA were randomly selected and propensity-matched with the study cohort in a 1:1 ratio according to age; sex; occupation; urbanization; comorbidities of hypothyroidism, hyperlipidemia, diabetes, liver cirrhosis, alcohol-related illness, hypertension, chronic obstructive pulmonary disease (COPD), obesity, inflammatory bowel disease, stroke, coronary artery disease (CAD), hepatitis B virus, and hepatitis C virus; and the index year. All patients were followed until the end of 2011 or withdrawal from the National Health Insurance program to determine the incidence of gallstones.

RESULTS

The prevalence of OSA was higher in men (67.3%) and in patients younger than 49 years (57.0%; mean age 47.8 ± 15.1 years). The cumulative incidence of gallstones was higher in the OSA cohort than in the non-OSA cohort (log-rank test, P < 0.001). Compared with patients without OSA, those with OSA had an increased risk of gallstones (adjusted hazard ratio = 1.53, 95% confidence interval = 1.16-2.03) after adjustment for age, sex, hyperlipidemia, diabetes, hypertension, COPD, stroke, and CAD.

CONCLUSION

The study shows a strong association between OSA and gallstones. Moreover, our findings suggest the requirement for survey and health education for gallstones in OSA and further studies to verify whether the treatment of OSA can reduce the risk of gallstones.

A review of the associations between obstructive sleep apnea and hypertensive disorders of pregnancy and possible mechanisms of disease

Obesity is prevalent among pregnant women in the United States; 15-20% of obese pregnant women have obstructive sleep apnea. The prevalence of obstructive sleep apnea increases along with body mass index, age and in the presence of other co-morbidities. Untreated obstructive sleep apnea in women is associated with a range of cardiovascular, pulmonary and metabolic co-morbidities; recent studies suggest that women with obstructive sleep apnea in pregnancy may be at significantly greater risk of entering pregnancy with chronic hypertension and/or of developing hypertensive disorders of pregnancy: gestational hypertension; preeclampsia; or eclampsia. This has serious public health implications; hypertensive disorders of pregnancy are a major cause of maternal and neonatal morbidity and mortality and are associated with a greater lifetime risk for cardiovascular disease. The mechanisms that associated obstructive sleep apnea with hypertensive disorders of pregnancy have not been defined, but several pathways are scientifically plausible. In this review, we will present a comprehensive literature review of the following: the associations between obstructive sleep apnea and hypertensive disorders of pregnancy; the proposed mechanisms that may connect obstructive sleep apnea and hypertensive disorders of pregnancy; and the effectiveness of treatment at mitigating these adverse outcomes.

Circulating Survivin Levels in Obstructive Sleep Apnoea

INTRODUCTION

Obstructive sleep apnoea (OSA) is characterised by a low-grade systemic and airway inflammation; however, the regulatory mechanisms of inflammation are poorly explored. Survivin (Birc5) is an anti-apoptotic protein which inhibits Type 1 inflammation; however, this molecule has not been investigated in OSA.

METHODS

Forty-five patients with OSA and 31 non-OSA control subjects were involved. Venous blood was collected for plasma survivin measurements before and after diagnostic overnight polysomnography. Plasma survivin levels were compared between the two groups and correlated to OSA severity and comorbidities.

RESULTS

Plasma survivin levels were lower in OSA in the evening (27.6 ± 89.9 vs. 108.3 ± 161.2 pg/ml, p < 0.01) and in the morning (17.4 ± 48.6 vs. 36.4 ± 69.2 pg/ml, p = 0.02) compared to the control group. This OSA-related decrease was also present when only the non-obese patients were analysed. Significant indirect relationships were observed between plasma survivin levels and measures of OSA severity such as the apnoea-hypopnoea index (r = - 0.45) or oxygen desaturation index (r = - 0.40, both p < 0.01); however, when adjusting to BMI, these became insignificant (p > 0.05). Low plasma survivin concentrations were associated with high BMI (r = - 0.35), high CRP (r = - 0.31), low HDL cholesterol (r = 0.24) and high triglyceride levels (r = - 0.24, all p < 0.05).

CONCLUSION

Plasma survivin levels are reduced in OSA, relate to disease severity, and are associated with high CRP levels. This suggests an impaired immunoregulation in this disorder which needs to be studied in further detail.

Roles of Microglial Phagocytosis and Inflammatory Mediators in the Pathophysiology of Sleep Disorders

Sleep serves crucial learning and memory functions in both nervous and immune systems. Microglia are brain immune cells that actively maintain health through their crucial physiological roles exerted across the lifespan, including phagocytosis of cellular debris and orchestration of neuroinflammation. The past decade has witnessed an explosive growth of microglial research. Considering the recent developments in the field of microglia and sleep, we examine their possible impact on various pathological conditions associated with a gain, disruption, or loss of sleep in this focused mini-review. While there are extensive studies of microglial implication in a variety of neuropsychiatric and neurodegenerative diseases, less is known regarding their roles in sleep disorders. It is timely to stimulate new research in this emergent and rapidly growing field of investigation.

Obstructive sleep apnea and objective short sleep duration are independently associated with the risk of serum vitamin D deficiency

BACKGROUND

Studies demonstrate an association between vitamin D (25(OH)D) deficiency and sleep disturbances, such as obstructive sleep apnea (OSA) and short sleep duration. However, to date, no studies have concurrently and objectively evaluated the effect of these factors on 25(OH)D.

OBJECTIVES

To evaluate whether OSA and objective short sleep duration are independently associated with reduced 25(OH)D in an adult population sample.

METHODS

A cross-sectional study included 657 individuals from the city of Sao Paulo, Brazil, as part of the ERA project. Participants fulfilled questionnaires and underwent clinical evaluation, polysomnography and blood sample collection for 25(OH)D quantification. OSA was classified into three categories (mild, moderate and severe). The risk of 25(OH)D deficiency was considered as levels<30 ng/mL. Short sleep duration was defined as total sleep time<6 hours.

RESULTS

The risk of 25(OH)D deficiency was observed in 59.5% of the sample, affecting more individuals of the female gender, obese, with African American ethnicity, and those that were smokers, sedentary and presented hypertension and diabetes. In the final logistic model adjusted for age, gender, ethnicity, obesity, smoking, hypertension, diabetes, sedentary lifestyle, seasonality and creatinine serum levels, both OSA and short sleep duration showed significant independent associations with the risk of 25(OH)D deficiency (moderate OSA: OR for 25(OH)D<30 = 2.21, 95% CI: 1.35-3.64, p<0.01; severe OSA: OR for 25(OH)D<30 = 1.78, 95% CI: 1.06-3.00, p = 0.03; short sleep duration: OR for 25(OH)D<30 = 1.61, 95% CI: 1.15-2.26, p = 0.01). After a subgroup analysis, similar results were observed only in participants ≥50 years.

CONCLUSION

OSA and short sleep duration are independently associated with the risk of 25(OH)D deficiency in an adult population. Age-related changes in vitamin D metabolism and the frequency of sleep disorders may be involved in these associations. Future studies exploring whether 25(OH)D levels may modulate OSA and sleep curtailment-related outcomes are needed.

Sleep Problems as Predictors in Attention-Deficit Hyperactivity Disorder: Causal Mechanisms, Consequences and Treatment

Attention-deficit hyperactivity disorder (ADHD) is notorious for its debilitating consequences and early age of onset. The need for early diagnosis and intervention has frequently been underscored. Previous studies have attempted to clarify the bidirectional relationship between ADHD and sleep problems, proposing a potential role for sleep problems as early predictors of ADHD. Sleep deprivation, sleep-disordered breathing, and circadian rhythm disturbances have been extensively studied, yielding evidence with regard to their induction of ADHD-like symptoms. Genetic-phenotypic differences across individuals regarding the aforementioned sleep problems have been elucidated along with the possible use of these characteristics for early prediction of ADHD. The long-term consequences of sleep problems in individuals with ADHD include obesity, poor academic performance, and disrupted parent-child interactions. Early intervention has been proposed as an approach to preventing these debilitating outcomes of ADHD, with novel treatment approaches ranging from melatonin and light therapy to myofunctional therapy and adjustments of the time point at which school starts.

Snoring and components of metabolic syndrome in Southeastern Chinese adults: A community-based study

INTRODUCTION

Snoring has been associated with a number of abnormal conditions, but little work has been done on its association with components of metabolic syndrome based on the epidemiology in Chinese adults.

OBJECTIVE

This study aimed to investigate the association between snoring and components of metabolic syndrome in southeastern Chinese adults.

METHODS

A two-stage, cross-sectional community-based study was performed in Fuzhou, Southeast China, from 2005 to 2009. Stage 1: 5500 subjects were administered a questionnaire. Data on self-reported snoring status, daytime somnolence, demographic data, disease histories, and potential confounders were collected and anthropometric measurements were performed. Stage 2: 1000 subjects who were already investigated underwent a blood test and measurement of blood pressure.

RESULTS

Data from 4286 subjects were available; 606 subjects were habitual snorers. The prevalence of overweight or obesity, hyperglycemia, hypertension, and dyslipidemia in occasional and habitual snorers was higher than that in the study population (16.66%, 7.89%, 10.52%, and 5.81%, respectively). A significantly increasing trend based on snoring frequency existed in the prevalence of metabolic disorders. The prevalence of components of metabolic syndrome continued to be significantly associated with snoring frequency after controlling confounding factors. Odds ratios of suffering from the aforementioned conditions for occasional and habitual snorers were 1.5-2.5 (P < 0.05) and 2.4-4.8 (P < 0.001) times higher, respectively, compared with nonsnorers.

CONCLUSIONS

The prevalence of snoring and components of metabolic syndrome is high in southeastern Chinese adults. Both habitual and occasional snoring are closely associated with metabolic disorders independent of confounding factors.

Restless legs syndrome and cardiovascular disease: a research roadmap

In this paper, we first critically appraise the epidemiologic literature examining the association of restless legs syndrome (RLS) with cardiovascular disease (CVD) and then consider whether lessons learned from the study of cardiovascular consequences of other sleep disorders might inform a research agenda to examine the potential mechanisms of cardiovascular morbidity of RLS. Cross-sectional and longitudinal studies are both mixed as to whether there is a meaningful association of RLS and CVD. On the other hand, numerous cross-sectional and longitudinal observational studies have shown a strong association of obstructive sleep apnea (OSA) with CVD risk. Each of the potential mediating mechanisms in OSA may also be assessed in RLS, including 1) neural mechanisms such as increased central sympathetic outflow, impaired baroreflex function, diminished heart rate and blood pressure variability, and increased chemoreflex sensitivity, 2) metabolic mechanisms such as glucose intolerance and reduced insulin sensitivity/diabetes as a result of sleep disturbance in RLS, 3) oxidative stress, 4) systemic or vascular inflammatory mechanisms, and 5) vascular mechanisms including impaired endothelial functioning, increased aortic stiffness, hypothalamic-pituitary axis activation or renin-angiotensin-aldosterone activation. Three known characteristics of RLS may contribute to these specific mechanisms of increased cardiovascular risk: 1) periodic limb movements of sleep, which are associated with large increases in heart rate and blood pressure, 2) sleep fragmentation and sleep deprivation, which are known to produce adverse consequences for neural, metabolic, oxidative, inflammatory, and vascular systems, and 3) iron deficiency, which is an emerging risk for cardiovascular disease. Future research priorities include additional epidemiologic studies which characterize multiple CVD risk factors, case-control studies which examine known markers of cardiovascular risk, and small clinical trials which assess the effects of RLS treatment on intermediate physiological markers such as sympathetic activity or baroreflex control, measures of vascular stiffness and reactivity, or measures of insulin sensitivity and glucose tolerance.

Immune and inflammatory responses to freediving calculated from leukocyte gene expression profiles

Freedivers hold their breath while diving, causing blood oxygen levels to decrease (hypoxia) while carbon dioxide increases (hypercapnia). Whereas blood gas changes are presumably involved in the progression of respiratory diseases, less is known about their effect on healthy individuals. Here we have used gene expression profiling to analyze elite athletes' immune and inflammatory responses to freediving. Blood was collected before and 1 and 3 h after a series of maximal dynamic and static freediving apneas in a pool, and peripheral blood gene expression was mapped on genome-wide microarrays. Fractions of phenotypically distinct immune cells were computed by deconvolution of the gene expression data using Cibersort software. Changes in gene activity and associated biological pathways were determined using R and GeneGo software. The results indicated a temporary increase of neutrophil granulocytes, and a decrease of cytotoxic lymphocytes; i.e., CD8+ T cells and resting NK cells. Biological pathway associations indicated possible protective reactions: genes involved in anti-inflammatory responses to proresolving lipid mediators were upregulated, whereas central factors involved in granule-mediated lymphocyte cytotoxicity were downregulated. While it remains unresolved whether freediving alters the immune system's defensive function, these results provide new insight into leukocyte responses and the protection of homeostasis in healthy athletes.

Fundamental role of pan-inflammation and oxidative-nitrosative pathways in neuropathogenesis of Alzheimer's disease in focal cerebral ischemic rats

Alzheimer's disease (AD) is a chronic progressive neurodegenerative condition of the brain, and it is the most common cause of dementia. Several neurobiological etiologies of AD are described in the literature. These include vascular, infectious, toxic, nutritional, metabolic, and inflammatory. However, these heterogeneous etiologies have a common denominator - viz. Inflammation and oxidative stress. Lipopolysaccharide (LPS) elevates the synthesis of proinflammatory cytokines and chemokines; chronically, together they trigger various pathological responses in the periphery and the CNS including dysfunctional memory consolidation and memory decline. Aging - the main risk factor for AD is inherently associated with inflammation. There are several age-related comorbidities that are also associated with inflammation and oxidative stress. Such co-prevailing aggravating factors, therefore, persist against a background of underlying aging-related pathology. They may converge, and their synergistic propagation may modify the disease course. A critical balance exists between homeostasis/repair and inflammatory factors; chronic, unrelenting inflammatory milieu succeeds in promoting a neuroinflammatory and neurodegenerative outcome. Extensive evidence is available that CNS inflammation is associated with neurodegeneration. LPS, proinflammatory cytokines, several mediators secreted by microglia, and oxidative-nitrosative stress in concert play a pivotal role in triggering neuroinflammatory processes and neurodegeneration. The persistent uncontrolled activity of the above factors can potentiate cognitive decline in tandem enhancing vulnerability to AD. Despite significant progress during the past twenty years, the prevention and treatment of AD have been tantalizingly elusive. Current studies strongly suggest that amelioration/prevention of the deleterious effects of inflammation may prove beneficial in preventing AD onset and retarding cognitive dysfunction in aging and AD. A concerted multi-focal therapeutic effort around the inflammation-oxidative-nitrosative stress paradigm may be crucial in preventing and treating AD. This paper informs on such relevant polypharmacy approach.

Biological plausibility linking sleep apnoea and metabolic dysfunction

Obstructive sleep apnoea (OSA) is a very common disorder that affects 10-25% of the general population. In the past two decades, OSA has emerged as a cardiometabolic risk factor in both paediatric and adult populations. OSA-induced metabolic perturbations include dyslipidaemia, atherogenesis, liver dysfunction and abnormal glucose metabolism. The mainstay of treatment for OSA is adenotonsillectomy in children and continuous positive airway pressure therapy in adults. Although these therapies are effective at resolving the sleep-disordered breathing component of OSA, they do not always produce beneficial effects on metabolic function. Thus, a deeper understanding of the underlying mechanisms by which OSA influences metabolic dysfunction might yield improved therapeutic approaches and outcomes. In this Review, we summarize the evidence obtained from animal models and studies of patients with OSA of potential mechanistic pathways linking the hallmarks of OSA (intermittent hypoxia and sleep fragmentation) with metabolic dysfunction. Special emphasis is given to adipose tissue dysfunction induced by sleep apnoea, which bears a striking resemblance to adipose dysfunction resulting from obesity. In addition, important gaps in current knowledge and promising lines of future investigation are identified.

Fundamental role of pan-inflammation and oxidative-nitrosative pathways in neuropathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a chronic progressive neurodegenerative condition of the brain, and it is the most common cause of dementia. Several neurobiological etiologies of AD are described in the literature. These include vascular, infectious, toxic, nutritional, metabolic, and inflammatory. However, these heterogeneous etiologies have a common denominator - viz. Inflammation and oxidative stress. Lipopolysaccharide (LPS) elevates the synthesis of proinflammatory cytokines and chemokines; chronically, together they trigger various pathological responses in the periphery and the CNS including dysfunctional memory consolidation and memory decline. Aging - the main risk factor for AD is inherently associated with inflammation. There are several age-related comorbidities that are also associated with inflammation and oxidative stress. Such co-prevailing aggravating factors, therefore, persist against a background of underlying aging-related pathology. They may converge, and their synergistic propagation may modify the disease course. A critical balance exists between homeostasis/repair and inflammatory factors; chronic, unrelenting inflammatory milieu succeeds in promoting a neuroinflammatory and neurodegenerative outcome. Extensive evidence is available that CNS inflammation is associated with neurodegeneration. LPS, proinflammatory cytokines, several mediators secreted by microglia, and oxidative-nitrosative stress in concert play a pivotal role in triggering neuroinflammatory processes and neurodegeneration. The persistent uncontrolled activity of the above factors can potentiate cognitive decline in tandem enhancing vulnerability to AD. Despite significant progress during the past twenty years, the prevention and treatment of AD have been tantalizingly elusive. Current studies strongly suggest that amelioration/prevention of the deleterious effects of inflammation may prove beneficial in preventing AD onset and retarding cognitive dysfunction in aging and AD. A concerted multi-focal therapeutic effort around the inflammation-oxidative-nitrosative stress paradigm may be crucial in preventing and treating AD. This paper informs on such relevant polypharmacy approach.

The platelet-to-lymphocyte ratio reflects the severity of obstructive sleep apnea syndrome and concurrent hypertension

Background

Chronic intermittent hypoxia, platelet activation and inflammation all play roles in the pathogenesis of obstructive sleep apnea syndrome (OSAS), which may increase the risk of cardiovascular disease (CVD). The aim of this study was to evaluate the relationship of the platelet-to-lymphocyte ratio (PLR) as a new biomarker showing systemic inflammation and platelet distribution width (PDW) as an indicator of platelet activation to the severity of OSAS.

Methods

A total of 290 patients suspected with OSAS who underwent a full night of polysomnography were included. The patients were placed into 4 separate groups according to their apnea-hypopnea index (AHI) scores; the control group (AHI <5), mild OSAS group (AHI 5–15), moderate OSAS group (AHI 16–30), and severe OSAS group (AHI >30). CVD risk was defined by the presence of hypertension, diabetes mellitus, current smoking, and dyslipidemia.

Results

Higher AHI groups were significantly correlated with increasing age, body mass index, systolic blood pressure and male sex. PLR and PDW were also significantly associated with AHI (r = 0.417 for PLR and r = 0.227 for PDW, all p-values < 0.001) and the Epworth sleepiness scale (r = 0.160 for PLR and r = 0.189 for PDW, all p-values <0.05). Multivariate regression analysis revealed that AHI ≥9.2 (adjusted odds ratios [OR] 5.03, 95 % confidential interval (CI) = 1.67-15.2, p = 0.004) and PLR ≥159 (adjusted OR 2.81, 95 % CI = 1.34-5.91, p = 0.006) were independently associated with the presence of hypertension.

Conclusion

PLR and PDW are associated with OSAS severity. PLR may also be useful as a systemic biomarker for the concurrent hypertension in OSAS patients.