Nonalcoholic fatty liver disease, nocturnal hypoxia, and endothelial function in patients with sleep apnea

Nephrological, Pulmonary, and Dermatological Complications in the Context of MAFLD/NAFLD: A Narrative Review

Background: The most common cause of chronic liver disease is now known to be non-alcoholic fatty liver disease (NAFLD), recently redefined as metabolic-associated fatty liver disease (MAFLD). This review aims to synthesize current evidence on the pathophysiology and clinical implications of nephrological, pulmonary, and dermatological manifestations among NAFLD/MAFLD patients. In order to find safe and efficient treatments, NAFLD/MAFLD has emerged as a primary concern for hepatologists worldwide. Methods: We conducted a comprehensive review of the literature from major databases, focusing on studies that evaluated the extrahepatic manifestations of NAFLD/MAFLD. Emphasis was placed on identifying pathophysiological mechanisms and assessing their clinical impact on renal, pulmonary, and dermatological systems. Results: Recent developments in the management of chronic viral hepatitis have lowered the mortality rate associated with chronic liver disease. However, the prevalence of NAFLD/MAFLD continues to rise, making chronic liver disease a significant health concern for the future. An increasing percentage of patients on liver transplant waiting lists now have cirrhosis and hepatocellular carcinoma due to non-alcoholic liver disease. Furthermore, the incidence and prevalence of chronic kidney disease have surged, linking NAFLD/MAFLD to higher morbidity, mortality, and healthcare costs. Conclusions: NAFLD/MAFLD is underdiagnosed and underappreciated, yet its incidence is rapidly increasing, raising concerns about a potential global epidemic. Given its multisystemic impact-extending to renal, pulmonary, and dermatological complications-it is crucial to develop interdisciplinary strategies for early detection and effective management of the disease.

Assessing the Pathophysiology, Morbidity, and Mortality of Obstructive Sleep Apnea

The basic definitions of obstructive sleep apnea (OSA), its epidemiology, its clinical features and complications, and the morbidity and mortality of OSA are discussed. Included in this treatise is a discussion of the various symptomatic and polysomnographic phenotypes of COPD that may enable better treatment and impact mortality in persons with OSA. The goal of this article is to serve as a reference for life and disability insurance company medical directors and underwriters when underwriting an applicant with probable or diagnosed sleep apnea. It is well-referenced (133 ref.) allowing for more in-depth investigation of any aspect of sleep apnea being queried.

Association of Obstructive Sleep Apnea with Nonalcoholic Fatty Liver Disease: Evidence, Mechanism, and Treatment

Obstructive sleep apnea (OSA), a common sleep-disordered breathing condition, is characterized by intermittent hypoxia (IH) and sleep fragmentation and has been implicated in the pathogenesis and severity of nonalcoholic fatty liver disease (NAFLD). Abnormal molecular changes mediated by IH, such as high expression of hypoxia-inducible factors, are reportedly involved in abnormal pathophysiological states, including insulin resistance, abnormal lipid metabolism, cell death, and inflammation, which mediate the development of NAFLD. However, the relationship between IH and NAFLD remains to be fully elucidated. In this review, we discuss the clinical correlation between OSA and NAFLD, focusing on the molecular mechanisms of IH in NAFLD progression. We meticulously summarize clinical studies evaluating the therapeutic efficacy of continuous positive airway pressure treatment for NAFLD in OSA. Additionally, we compile potential molecular biomarkers for the co-occurrence of OSA and NAFLD. Finally, we discuss the current research progress and challenges in the field of OSA and NAFLD and propose future directions and prospects.

Association between sleep apnea and ultrasound-defined liver fibrosis: Results from NHANES 2017 to 2020

Liver fibrosis is a critical factor in the advancement of nonalcoholic fatty liver disease towards cirrhosis. There is limited research exploring the association between obstructive sleep apnea (OSA) and liver fibrosis among community populations. The present study aimed to assess the association between sleep apnea (SA) and liver fibrosis based on the National Health and Nutrition Examination Survey (NHANES). Data were acquired from NHANES survey cycle 2017 to 2020. We assessed liver fibrosis by the median values of liver stiffness measurement (LSM). The diagnosis of SA was based on participants' response to sleep questionnaire. Univariate and multivariate logistic regression were used to validate the association of SA and liver fibrosis. A total of 7615 participants were included in this study. The LSM level of SA group was significantly higher than non-SA group. The proportion of liver fibrosis in SA group was markedly higher than that in non-SA group (14.0% vs 7.3%, P < .001). Univariate logistic analysis showed that SA was positively associated with liver fibrosis (OR = 2.068, 95%CI = 1.715-2.494, P < .001). Further multivariate logistic analysis revealed that SA was independently associated with increased risk of liver fibrosis after adjusting for confounding factors (OR = 1.277, 95%CI = 1.003-1.625, P = .048). The current study demonstrated an independent association between self-reported SA and increased risk of ultrasound-defined liver fibrosis in community-based sample.

Long-term intermittent hypoxia in mice induces inflammatory pathways implicated in sleep apnea and steatohepatitis in humans

Obstructive sleep apnea (OSA) induces intermittent hypoxia (IH), an independent risk factor for non-alcoholic fatty liver disease (NAFLD). While the molecular links between IH and NAFLD progression are unclear, immune cell-driven inflammation plays a crucial role in NAFLD pathogenesis. Using lean mice exposed to long-term IH and a cohort of lean OSA patients (n = 71), we conducted comprehensive hepatic transcriptomics, lipidomics, and targeted serum proteomics. Significantly, we demonstrated that long-term IH alone can induce NASH molecular signatures found in human steatohepatitis transcriptomic data. Biomarkers (PPARs, NRFs, arachidonic acid, IL16, IL20, IFNB, TNF-α) associated with early hepatic and systemic inflammation were identified. This molecular link between IH, sleep apnea, and steatohepatitis merits further exploration in clinical trials, advocating for integrating sleep apnea diagnosis in liver disease phenotyping. Our unique signatures offer potential diagnostic and treatment response markers, highlighting therapeutic targets in the comorbidity of NAFLD and OSA.

Associations between Rest-Activity Rhythms and Liver Function Tests: The US National Health and Nutrition Examination Survey, 2011-2014

Liver functions are regulated by the circadian rhythm; however, whether a weakened circadian rhythm is associated with impaired liver function is unclear. This study aims to investigate the association of characteristics of rest-activity rhythms with abnormal levels of biomarkers of liver function. Data were obtained from the National Health and Nutrition Examination Survey 2011-2014. Seven rest-activity rhythm parameters were derived from 24 h actigraphy data using the extended cosine model and non-parametric methods. Multiple logistic regression and multiple linear regression models were used to assess the associations between rest-activity rhythm parameters and alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transaminase (GGT), albumin and bilirubin. Weakened overall rhythmicity characterized by a lower F statistic was associated with higher odds of abnormally elevated ALP (ORQ1vs.Q5: 2.16; 95% CI 1.19, 3.90) and GGT (ORQ1vs.Q5: 2.04; 95% CI 1.30, 3.20) and abnormally lowered albumin (ORQ1vs.Q5: 5.15; 95% CI 2.14, 12.38). Similar results were found for a lower amplitude, amplitude:mesor ratio, interdaily stability and intradaily variability. Results were robust to the adjustment of confounders and cannot be fully explained by individual rest-activity behaviors, including sleep and physical activity. Weakened rest-activity rhythms were associated with worse liver function as measured by multiple biomarkers, supporting a potential role of circadian rhythms in liver health.

Chronic intermittent hypoxia promotes early intrahepatic endothelial impairment in rats with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a progressive disease that ranges from simple steatosis to cirrhosis. Obstructive sleep apnea syndrome (OSAS) and chronic intermittent hypoxia (CIH) are implicated in the pathogenesis of NAFLD. However, the overlapping consequences of CIH on liver sinusoidal endothelial function over time in NAFLD are largely unknown. We explored endothelial dysfunction in a rat model of NAFLD with a high-fat diet exposed to CIH [12 h/day, every 30 s to fractional concentration of oxygen ([Formula: see text] 8%-10%]. The livers were isolated and perfused, and the endothelial function was determined by testing the vasodilation of the liver circulation to increased concentrations of acetylcholine and von Willebrand factor (vWF) and intercellular adhesion molecule 1 (ICAM-1) expression. Phosphorylated endothelial nitric oxide synthase (p-eNOS), cGMP, and oxidative stress were assessed to determine nitric oxide bioavailability. Inflammation and fibrosis were evaluated by transaminases, myeloperoxidase activity, hydroxyproline, and histological evaluation. Hypoxia-inducible factors (HIFs) were studied as a marker of hypoxia and after a second insult with acetaminophen. CIH exposure provoked typical systemic features of OSAS and provoked a decreased response in vasodilation to acetylcholine. This was associated with increased oxidative stress and reduced p-eNOS and cGMP. The microcirculation impairment due to CIH preceded significant hepatic inflammation and fibrotic changes, despite the presence of HIF expression. In conclusion, CIH exacerbates endothelial dysfunction in NAFLD rats associated with increased oxidative stress and reduced nitric oxide bioavailability. This occurs before inflammation and fibrosis establish. Our results suggest that with CIH endothelial dysfunction should be considered an early target.NEW & NOTEWORTHY We believe the findings are of relevance because we demonstrate that chronic intermittent hypoxia further augments impaired hepatic endothelial dysfunction in nonalcoholic fatty liver disease rats. Because obstructive sleep apnea syndrome is associated with systemic endothelial dysfunction in cardiovascular disorders, and chronic intermittent hypoxia is an independent and reversible risk factor for hypertension and coronary artery disease, we hypothesized that this entity may be of potential relevance in the pathophysiology of nonalcoholic fatty liver disease.

Management of Patients With Non-alcoholic Steatohepatitis Undergoing Liver Transplantation: Considerations for the Anesthesiologist

Non-alcoholic fatty liver disease (NAFLD) currently affects more than 25% of the world population and is rising. NAFLD can progress to non-alcoholic steatohepatitis that is associated with hepatic inflammation and fibrosis and can result in cirrhosis with subsequent liver failure. Non-alcoholic steatohepatitis (NASH) has now emerged as one of the leading etiologies for a liver transplant among adults in the United States. Given the rising incidence of liver transplants in patients with NASH-related cirrhosis, it is essential for anesthesiologists to be familiar with this condition as well as with NASH-related comorbidities and perioperative complications. Not only is NASH linked to metabolic syndrome, but it also is independently associated with cardiovascular disease, renal and thyroid dysfunction, obstructive sleep apnea (OSA), and a hypercoagulable state. The association with these conditions can affect the perioperative outcome of these patients, particularly because of increased mortality from major adverse cardiovascular events and sepsis. In order to decrease the perioperative morbidity and mortality of patients with NASH undergoing a liver transplant, a multidisciplinary approach to their perioperative management is essential, along with careful preoperative evaluation and aggressive intraoperative and postoperative monitoring. The focus of this review article is to provide a comprehensive overview of challenges associated with liver transplants in patients with NASH and to provide suggestions for appropriate patient selection and perioperative management.

Obstructive Sleep Apnea and Nonalcoholic Fatty Liver Disease in the General Population: A Cross-Sectional Study Using Nationally Representative Data

(1) Background: To evaluate the association between obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease (NAFLD) in the general population using a nationally representative sample from South Korea; (2) Methods: This study included 4275 adults aged ≥40 years who completed the snoring, tiredness, observed apnea, high blood pressure, body mass index (BMI), age, neck circumference, and gender (STOP-Bang) questionnaire. The risk of OSA was stratified into low, intermediate, and high grades according to the STOP-Bang score. The prevalence of NAFLD according to the STOP-Bang score was calculated, and the increasing trend was measured. A complex sample multivariable regression analysis with adjustments for possible confounding variables was used to calculate the odds ratio of NAFLD and advanced fibrosis. Subgroup analysis was conducted with stratification based on sex and obesity status; (3) Results: We identified 1021 adults with NAFLD and 3254 adults without NAFLD. The prevalence of NAFLD increased significantly with higher STOP-Bang scores in both men and women. Participants of both sexes with high STOP-Bang scores were more likely to have NAFLD. Compared to non-obese individuals, the risk of NAFLD according to the STOP-Bang score was more intense in obese individuals. With respect to hepatic steatosis, there was no significant association between advanced fibrosis and STOP-Bang score; (4) Conclusions: OSA, the risk of which was measured using the STOP-Bang model, was closely associated with NAFLD in both Korean men and women. Clinicians should consider screening for NAFLD in individuals with a high STOP-Bang score.

Coagulation and Endothelial Dysfunction Associated with NAFLD: Current Status and Therapeutic Implications

Non-alcoholic fatty liver disease (NAFLD) is closely related to insulin resistance, type 2 diabetes mellitus and obesity. It is considered a multisystem disease and there is a strong association with cardiovascular disease and arterial hypertension, which interfere with changes in the coagulation system. Coagulation disorders are common in patients with hepatic impairment and are dependent on the degree of liver damage. Through a review of the literature, we consider and discuss possible disorders in the coagulation cascade and fibrinolysis, endothelial dysfunction and platelet abnormalities in patients with NAFLD.

Sleep apnea phenotyping and relationship to disease in a large clinical biobank

Objective

Sleep apnea is associated with a broad range of pathophysiology. While electronic health record (EHR) information has the potential for revealing relationships between sleep apnea and associated risk factors and outcomes, practical challenges hinder its use. Our objectives were to develop a sleep apnea phenotyping algorithm that improves the precision of EHR case/control information using natural language processing (NLP); identify novel associations between sleep apnea and comorbidities in a large clinical biobank; and investigate the relationship between polysomnography statistics and comorbid disease using NLP phenotyping.

Materials and Methods

We performed clinical chart reviews on 300 participants putatively diagnosed with sleep apnea and applied International Classification of Sleep Disorders criteria to classify true cases and noncases. We evaluated 2 NLP and diagnosis code-only methods for their abilities to maximize phenotyping precision. The lead algorithm was used to identify incident and cross-sectional associations between sleep apnea and common comorbidities using 4876 NLP-defined sleep apnea cases and 3× matched controls.

Results

The optimal NLP phenotyping strategy had improved model precision (≥0.943) compared to the use of one diagnosis code (≤0.733). Of the tested diseases, 170 disorders had significant incidence odds ratios (ORs) between cases and controls, 8 of which were confirmed using polysomnography (n = 4544), and 281 disorders had significant prevalence OR between sleep apnea cases versus controls, 41 of which were confirmed using polysomnography data.

Discussion and Conclusion

An NLP-informed algorithm can improve the accuracy of case-control sleep apnea ascertainment and thus improve the performance of phenome-wide, genetic, and other EHR analyses of a highly prevalent disorder.

Sleep apnea is a common disease in which breathing partially or completely pauses during sleep, leading to less oxygen in the blood, repeated awakenings, and increased risk of developing multiple diseases. Current studies of sleep apnea often have relatively few participants due to the challenge of performing overnight sleep recordings. Electronic health record (EHR) billing code diagnoses of sleep apnea could be repurposed to increase the size of research studies, but the accuracy of the diagnoses is reduced. We developed a reusable algorithm that improves the accuracy of EHR sleep apnea diagnoses using natural language processing to extract information from clinical notes. As a proof of concept, we used the algorithm to identify hundreds of diseases that are increased among participants with sleep apnea compared to similar patients without sleep apnea. Many of these disease relationships with sleep apnea have not been previously recognized. This improved algorithm will help to accelerate future large-scale investigations of the causes and consequences of sleep apnea.

Research status and progress of metabolic associated fatty liver disease

Metabolic associated fatty liver disease (MAFLD) is a more appropriate general predicate to describe non-alcoholic fatty liver disease. The new definition lists metabolic dysfunction as an important cause of liver disease, demonstrates the high heterogeneity of this condition, and speeds up the transformation path to new treatment. The incidence of extrahepatic complications and related diseases of MAFLD far exceed that of the liver disease itself, which seriously threatens human health. In view of the current insufficient understanding of its severity, and the imperfect understanding of the disease scope, pathogenesis, and diagnosis of extrahepatic complications, especially the lack of effective drug treatment, this paper introduces and reviews the research status and progress of extrahepatic complications of MAFLD.

Novel screening model of obstructive sleep apnea for snorers with suspected NAFLD undergoing liver sonography

BACKGROUND/AIMS

Given the increased incidence of obstructive sleep apnea (OSA) among patients with nonalcoholic fatty liver disease (NAFLD), noninvasive screening methods are urgently needed to screen for OSA risk in these patients when conducting an office-based assessment of hepatic steatosis. Therefore, we investigated the controlled attenuation parameter (CAP) and hepatic steatosis index (HSI) in patients with and without OSA and developed screening models to detect OSA.

METHODS

We retrospectively reviewed the medical records of all adult snorers with suspected NAFLD undergoing liver sonography between June 2017 and June 2020. Records encompassed CAP and HSI data as well as data collected during in-hospital full-night polysomnography. The multivariate logistic regression models were constructed to explore the predictors of OSA risk. Furthermore, model validation was performed based on the medical records corresponding to the July 2020-June 2021 period.

RESULTS

A total of 59 patients were included: 81.4% (48/59) were men, and the mean body mass index (BMI) was 26.4 kg/m². Among the patients, 62.7% (37/59) and 74.6% (44/59) (detected by the HSI and CAP, respectively) had NAFLD, and 78% (46/59) were diagnosed with OSA on the basis of polysomnography. Three screening models based on multivariate analysis were established. The model combining male sex, a BMI of > 24.8, and an HSI of > 38.3 screened for OSA risk the most accurately, with an area under the receiver operating characteristic curve of 0.81 (sensitivity: 78%; specificity: 85%; and positive and negative predictive values: 95% and 52%, respectively) in the modeling cohort. An accuracy of 70.0% was achieved in the validation group.

CONCLUSIONS

The combination screening models proposed herein provide a convenient, noninvasive, and rapid screening tool for OSA risk and can be employed while patients receive routine hepatic check-ups. These models can assist physicians in identifying at-risk OSA patients and thus facilitate earlier detection and timely treatment initiation.

Nonalcoholic fatty liver disease is associated with the development of obstructive sleep apnea

Increasing evidence suggests that obstructive sleep apnea (OSA) is a metabolic syndrome-related disease; however, the association between nonalcoholic fatty liver disease (NAFLD) and OSA is not firmly established. In this study, we investigated the relationship between NAFLD and OSA in a general population drawn from a nationwide population-based cohort. Data from the Korean National Health Insurance System between January 2009 and December 2009 were analyzed using Cox proportional hazards model. NAFLD was defined as a fatty liver index (FLI) ≥ 60 in patients without excessive alcohol consumption (who were excluded from the study). Newly diagnosed OSA during follow-up was identified using claims data. Among the 8,116,524 participants, 22.6% had an FLI score of 30–60 and 11.5% had an FLI ≥ 60. During median follow-up of 6.3 years, 45,143 cases of incident OSA occurred. In multivariable analysis, the risk of OSA was significantly higher in the higher FLI groups (adjusted hazard ratio [aHR] 1.15, 95% confidence interval [CI] 1.12–1.18 for FLI 30–60 and aHR 1.21, 95% CI 1.17–1.26 for FLI ≥ 60). These findings were consistent regardless of body mass index and presence of abdominal obesity. In conclusion, a high FLI score may help identify individuals with a high risk of OSA. Understanding the association between NAFLD and OSA may have clinical implications for risk-stratification of individuals with NAFLD.

Association between obstructive sleep apnea and non-alcoholic fatty liver disease in pediatric patients: a meta-analysis

BACKGROUND

Some studies have reported a relationship between obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) in pediatric population. However, this issue remains controversial.

OBJECTIVES

The purpose of the present study was to investigate the association between OSA and NAFLD in pediatric population.

METHODS

We systematically searched PubMed, Web of Science, Embase for eligible studies. The data involving markers of NAFLD including alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic inflammation, hepatic fibrosis of both OSA group and control group were extracted. Pooled standardised mean difference (SMD) and weighted mean difference (WMD) were appropriately calculated through a fixed or random-effect model.

RESULTS

Nine cross-sectional studies with 1133 children and adolescents were included. OSA was significantly associated with ALT, AST, and NAFLD fibrosis stage, but not NAFLD inflammation grade. Subgroup analysis indicated that both mild OSA and severe OSA were significantly associated with elevated ALT and AST. Furthermore, in the studies with all main confounding factors (age, gender, and BMI) matched, OSA group had higher ALT and AST levels than control group.

CONCLUSIONS

This meta-analysis suggested that OSA was associated with NAFLD evidenced by elevated liver enzymes and progressive hepatic fibrosis in pediatric population. Screening and monitoring of NAFLD in pediatric patients with obesity-related OSA are necessary.

Hypoxia and Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide and comprises varied grades of intrahepatic lipid accumulation, inflammation, ballooning, and fibrosis; the most severe cases result in cirrhosis and liver failure. There is extensive clinical and experimental evidence indicating that chronic intermittent hypoxia, featuring a respiratory disorder of growing prevalence worldwide termed obstructive sleep apnea, could contribute to the progression of NAFLD from simple steatosis, also termed non-alcoholic fatty liver or hepatosteatosis, to non-alcoholic steatohepatitis; however, the molecular mechanisms by which hypoxia might contribute to hepatosteatosis setup and progression still remain to be fully elucidated. In this review, we have prepared an overview about the link between hypoxia and lipid accumulation within the liver, focusing on the impact of hypoxia on the molecular mechanisms underlying hepatosteatosis onset.

Non-alcoholic Fatty Liver Disease: Growing Burden, Adverse Outcomes and Associations

Nonalcoholic fatty liver disease (NAFLD) is a systemic disorder with a complex multifactorial pathogenesis and heterogenous clinical manifestations. NAFLD, once believed to be an innocuous condition, has now become the most common cause of chronic liver disease in many countries worldwide. NAFLD is already highly prevalent in the general population, and owing to a rising incidence of obesity and diabetes mellitus, the incidence of NAFLD and its impact on global healthcare are expected to increase in the future. A subset of patients with NAFLD develops progressive liver disease leading to cirrhosis, hepatocellular carcinoma, and liver failure. NAFLD has emerged as one of the leading causes of cirrhosis and hepatocellular carcinoma in recent years. Moreover, HCC can occur in NAFLD even in absence of cirrhosis. Compared with the general population, NAFLD increases the risk of liver-related, cardiovascular and all-cause mortality. NAFLD is bidirectionally associated with metabolic syndrome. NAFLD increases the risk and contributes to aggravation of the pathophysiology of atherosclerosis, cardiovascular diseases, diabetes mellitus, and chronic kidney disease. In addition, NAFLD is linked to colorectal polyps, polycystic ovarian syndrome, osteoporosis, obstructive sleep apnea, stroke, and various extrahepatic malignancies. Extended resection of steatotic liver is associated with increased risk of liver failure and mortality. There is an increasing trend of NAFLD-related cirrhosis requiring liver transplantation, and the recurrence of NAFLD in such patients is almost universal. This review discusses the growing burden of NAFLD, its outcomes, and adverse associations with various diseases.

Non-alcoholic fatty liver disease among patients with sleep disorders: a Nationwide study of Taiwan

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases. Studies have shown that sleep apnea is associated with NAFLD. However, studies on the association between sleep disorders in general and NAFLD are limited. We conducted a nationwide population-based longitudinal study to evaluate this potential association.

METHODS

We identified patients diagnosed with sleep disorders in the years 2000 through 2005 in Taiwan using the National Health Insurance Research Database and selected an equal number of patients without sleep disorders from the same database as the comparison cohort. The patients were followed from the index date to the diagnosis of NAFLD or the end of 2013. We used Cox proportional hazards models to estimate the risk of NAFLD associated with sleep disorders.

RESULTS

A total of 33,045 patients with sleep disorders were identified. The incidence of NAFLD was 14.0 per 10,000 person-year in patients with sleep disorders and 6.2 per 10,000 person-year in the comparison cohort. The adjusted hazard ratio (AHR) of NAFLD associated with sleep disorders was 1.78 (95% confidence interval [95%CI]: 1.46-2.16), and other independent risk factors included male sex (AHR = 1.31, 95%CI: 1.12-1.54), age 40-59 years (AHR = 1.49, 95%CI: 1.21-1.82), and dyslipidemia (AHR = 2.51, 95%CI: 2.08-3.04). In the subgroup analyses, both patients with (AHR = 2.24, 95%CI: 1.05-4.77) and without (AHR = 1.77, 95%CI: 1.46-2.15) sleep apnea had an increased risk of NAFLD.

CONCLUSIONS

Sleep disorders are associated with NAFLD, even in patients without sleep apnea. Further studies are warranted to explore the mechanisms of the association.

Obstructive sleep apnea and liver injury in severely obese patients with nonalcoholic fatty liver disease

OBJECTIVES

Obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease (NAFLD) are common in subjects with severe obesity. It has been suggested that insulin resistance and systemic inflammation may play a role in the development of nonalcoholic steatohepatitis (NASH), but the mechanisms remain controversial. The aim of this study was to explore the influence of OSA on liver injury and its potential mechanisms in severely obese patients with NAFLD.

METHODS

Severely obese patients requiring bariatric surgery were consecutively recruited between November 2017 and June 2018. Demographic, biochemical, liver ultrasound, and ambulatory polygraph data were collected.

RESULTS

One hundred fifty-three subjects with liver ultrasound-verified NAFLD were classified into three groups according to the apnea-hypopnea index (AHI). The level of serum alanine aminotransferase (ALT) and gamma-glutamyl transpeptidase (GGT) tended to increase with more severe OSA (P = 0.024 and P = 0.004, respectively). In the unadjusted analysis, both ALT and GGT were positively correlated with AHI, oxygen desaturation index, percentage of total sleep time spent with oxyhemoglobin saturation below 90%, male sex, homeostasis model assessment of insulin resistance (HOMA-IR), and total cholesterol, while liver enzymes were negatively related to lowest oxygen saturation. In multiple regression analysis, AHI (odds ratio (OR) = 1.052, P = 0.044) and HOMA-IR (OR = 1.135, P = 0.001) were independent risk factors for an elevated ALT level. High-sensitivity C-reactive protein (hs-CRP) was positively associated with BMI and GGT (r = 0.349 and r = 0.164 (P < 0.05), respectively), and no correlation was found between hs-CRP and AHI or other parameters of hypoxia. hs-CRP and GGT remained significantly correlated after adjusting for confounding parameters (OR = 2.509, P = 0.013).

CONCLUSIONS

OSA may play a role in liver injury among severely obese individuals with NAFLD. Insulin resistance and systemic inflammation were possible contributing factors in this process.

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.

Low Liver Density Is Linked to Cardiovascular Comorbidity in COPD: An ECLIPSE Cohort Analysis

Purpose

Fatty liver disease is associated with cardiometabolic disorders and represents a potential key comorbidity in Chronic Obstructive Pulmonary Disease (COPD). Some intermediary mechanisms of fatty liver disease (including its histological component steatosis) include tissue hypoxia, low-grade inflammation and oxidative stress that are key features of COPD. Despite these shared physiological pathways, the effect of COPD on the prevalence of hepatic steatosis, and the association between hepatic steatosis and comorbidities in this population remain unclear. Liver density measured by computed tomography (CT)-scan is a non-invasive surrogate of fat infiltration, with lower liver densities reflecting more fat infiltration and a liver density of 40 Hounsfield Units (HU) corresponding to a severe 30% fat infiltration.

Patients and Methods

We took advantage of the international cohort ECLIPSE in which non-enhanced chest CT-scans were obtained in 1554 patients with COPD and 387 healthy controls to analyse the liver density at T12-L1.

Results

The distribution of liver density was similar and the prevalence of severe steatosis (density<40 HU) was not different (4.7% vs 5.2%, p=0.7) between COPD and controls. In patients with COPD, the lowest liver density quartile was associated, after age and sex adjustment, with coronary artery disease (OR_a=1.59, 95% CI 1.12 to 2.24) and stroke (OR_a=2.20, 95% CI 1.07 to 4.50), in comparison with the highest liver density quartile.

Conclusion

The present data indicate that a low liver density emerged as a predictor of cardiovascular comorbidities in the COPD population. However, the distribution of liver density and the prevalence of severe steatosis were similar in patients with COPD and control subjects.

Severity Indices for Obstructive Sleep Apnea Syndrome Reflecting Glycemic Control or Insulin Resistance

Objective We aimed to identify obstructive sleep apnea syndrome (OSAS) severity indices reflecting the anthropometric and metabolic characteristics of patients with OSAS. Methods A total of 76 patients with OSAS underwent nasal continuous positive airway pressure (nCPAP). We also investigated the effects of nCPAP on OSAS-associated muscle sympathetic nerve activity (MSNA), risk for cardiovascular diseases, and insulin secretion and sensitivity. Results Among the OSAS severity indices, HbA1c was significantly correlated with the apnea-hypopnea index, whereas HOMA-beta, HOMA-IR, and hepatic insulin resistance were significantly correlated with % SpO₂<90%, independent of age, gender, and body mass index (BMI). Burst incidence of MSNA was independently associated with only a 3% oxygen desaturation index. nCPAP therapy significantly lowered the OSAS severity indices and reduced the burst rate, burst incidence, and heart rate. Conclusion The OSAS severity indices reflecting apnea/hypopnea are associated with glycemic control, whereas those reflecting hypoxia, particularly % SpO₂<90%, are associated with hepatic insulin resistance independent of obesity. Both types of OSAS severity indices, especially the 3% oxygen desaturation index (reflecting intermittent hypoxia), are independently associated with MSNA, which is dramatically lowered with the use of nCPAP therapy. These findings may aid in interpreting each OSAS severity index and understanding the pathophysiology of OSAS in clinical settings.

Hypoxia exacerbates nonalcoholic fatty liver disease via the HIF-2α/PPARα pathway

This study aimed to investigate whether hypoxia can affect nonalcoholic fatty liver disease (NAFLD) progression and the associated mechanisms, specifically regarding the hypoxia-inducible factor (HIF)-2α/peroxisome proliferator-activated receptor (PPAR)α pathway in vitro and in vivo. Recent studies have reported that, compared with HIF-1α, HIF-2α has different effects on lipid metabolism. We propose hypoxia may exacerbate NAFLD by the HIF-2α upregulation-induced suppression of PPARα in the liver. To verify this hypothesis, a steatotic human hepatocyte (L02) cell line treated with free fatty acids and a mouse model of NAFLD fed a high-fat diet were used. Steatotic hepatocytes were treated with hypoxia, HIF-2α siRNA, PPARα agonists, and inhibitors, respectively. Meanwhile, the NAFLD mice were exposed to intermittent hypoxia or intermittent hypoxia with PPARα agonists. The relative gene expression levels of HIF-1α, HIF-2α, mitochondrial function, fatty acid β-oxidation and lipogenesis were examined. Evidence of lipid accumulation was observed, which demonstrated that, compared with normal hepatocytes, steatotic hepatocytes exhibited higher sensitivity to hypoxia. This phenomenon was closely associated with HIF-2α. Moreover, lipid accumulation in hepatocytes was ameliorated by HIF-2α silencing or a PPARα agonist, despite the hypoxia treatment. HIF-2α overexpression under hypoxic conditions suppressed PPARα, leading to PGC-1α, NRF-1, ESRRα downregulation, and mitochondrial impairment. Additionally, β-oxidation genes such as CPT1α, CPT2α, ACOX1, and ACOX2 were downregulated and lipogenesis genes including LXRα, FAS, and SCD1 were upregulated by hypoxia. Therefore, we concluded that HIF-2α overexpression induced by hypoxia aggravated NAFLD progression by suppressing fatty acid β-oxidation and inducing lipogenesis in the liver via PPARα.

Extra-hepatic manifestations and complications of nonalcoholic fatty liver disease

This review article aims to synthesize the evidence regarding nonalcoholic fatty liver disease (NAFLD) as a systemic disorder. We critically discuss the metabolic syndrome and its components; the cardiovascular and the endocrine system; chronic respiratory disorders; the musculoskeletal system; the skin; and extra-hepatic tumors. We conclude that, while some of these extra-hepatic conditions clearly predispose to the development of secondary forms of NAFLD (typically hypothyroidism-induced NAFLD), others result from pre-existent NAFLD (e.g., certain extra-hepatic tumors) and others (such as Type 2 Diabetes) have, with NAFLD, mutual and bidirectional associations. Analyzed data imply that NAFLD is not merely a hepatic disease. It is also and possibly more importantly, a systemic disorder requiring a special awareness, a multidisciplinary approach and a multidimensional vision.

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.

Associations of variants In the hexokinase 1 and interleukin 18 receptor regions with oxyhemoglobin saturation during sleep

Sleep disordered breathing (SDB)-related overnight hypoxemia is associated with cardiometabolic disease and other comorbidities. Understanding the genetic bases for variations in nocturnal hypoxemia may help understand mechanisms influencing oxygenation and SDB-related mortality. We conducted genome-wide association tests across 10 cohorts and 4 populations to identify genetic variants associated with three correlated measures of overnight oxyhemoglobin saturation: average and minimum oxyhemoglobin saturation during sleep and the percent of sleep with oxyhemoglobin saturation under 90%. The discovery sample consisted of 8,326 individuals. Variants with p < 1 × 10(-6) were analyzed in a replication group of 14,410 individuals. We identified 3 significantly associated regions, including 2 regions in multi-ethnic analyses (2q12, 10q22). SNPs in the 2q12 region associated with minimum SpO2 (rs78136548 p = 2.70 × 10(-10)). SNPs at 10q22 were associated with all three traits including average SpO2 (rs72805692 p = 4.58 × 10(-8)). SNPs in both regions were associated in over 20,000 individuals and are supported by prior associations or functional evidence. Four additional significant regions were detected in secondary sex-stratified and combined discovery and replication analyses, including a region overlapping Reelin, a known marker of respiratory complex neurons.These are the first genome-wide significant findings reported for oxyhemoglobin saturation during sleep, a phenotype of high clinical interest. Our replicated associations with HK1 and IL18R1 suggest that variants in inflammatory pathways, such as the biologically-plausible NLRP3 inflammasome, may contribute to nocturnal hypoxemia.

Impact of Non-alcoholic Fatty Liver Disease on long-term cardiovascular events and death in Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) and Non-Alcoholic Fatty Liver Disease (NAFLD) both independently increase cardiovascular risk. We hypothesized that NAFLD might increase the incidence of cardiovascular disease and death in COPD patients. The relationship between NAFLD, incident cardiovascular events, and death was assessed in a prospective cohort of COPD patients with 5-year follow-up. Noninvasive algorithms combining biological parameters (FibroMax®) were used to evaluate steatosis, non-alcoholic steatohepatitis (NASH) and liver fibrosis. Univariate and multivariate Cox regression models were used to assess the hazard for composite outcome at the endpoint (death or cardiovascular event) for each liver pathology. In 111 COPD patients, 75% exhibited liver damage with a prevalence of steatosis, NASH and fibrosis of 41%, 37% and 61%, respectively. During 5-year follow-up, 31 experienced at least one cardiovascular event and 7 died. In univariate analysis, patients with liver fibrosis had more cardiovascular events and higher mortality (Hazard ratio [95% CI]: 2.75 [1.26; 6.03]) than those with no fibrosis; this remained significant in multivariate analysis (Hazard ratio [95% CI]: 2.94 [1.18; 7.33]). We also found that steatosis and NASH were not associated with increased cardiovascular events or mortality. To conclude, early assessment of liver damage might participate to improve cardiovascular outcomes in COPD patients.

Increased liver stiffness in patients with severe sleep apnoea and metabolic comorbidities

The goal of this study was to assess the relationship between the severity of obstructive sleep apnoea (OSA) and liver stiffness measurement (LSM), one of the most accurate noninvasive screening tools for liver fibrosis in nonalcoholic fatty liver disease.The study included 147 patients with at least one criterion for the metabolic syndrome, assessed by polysomnography for suspected OSA. LSM was performed using transient elastography (FibroScan). Significant liver disease and advanced liver fibrosis were defined as LSM ≥7.3 and ≥9.6 kPa, respectively.23 patients were excluded because of unreliable LSM. Among 124 patients, 34 (27.4%) had mild OSA, 38 (30.6%) had moderate OSA and 52 (42.0%) had severe OSA. LSM values were 7.3- <9.6 kPa in 18 (14.5%) patients and ≥9.6 kPa in 15 (12.1%) patients. A dose-response relationship was observed between OSA severity and LSM values (p=0.004). After adjustment for age, sex, metabolic syndrome and insulin resistance, severe OSA was associated with an increased risk of LSM ≥7.3 kPa (OR 7.17, 95% CI 2.51-20.50) and LSM ≥9.6 kPa (OR 4.73, 95% CI 1.25-17.88).In patients with metabolic comorbidities, severe OSA is independently associated with increased liver stiffness, which may predispose to a higher risk of significant liver disease and poorer prognosis.

Fibromax-based nonalcoholic fatty liver disease in chronic obstructive pulmonary disease patients with obstructive sleep apnea: Methodological considerations

The relationship between nonalcoholic fatty liver disease (NAFLD) and obstructive sleep apnea (OSA) has been well demonstrated, but remains to be evidenced in chronic obstructive pulmonary disease (COPD). Recently, Viglino et al. (Eur Respir J, 2017) attempted to determine the prevalence of liver fibrosis, steatosis and nonalcoholic steatohepatitis (NASH) in COPD patients, some of whom had OSA, basing the NAFLD diagnostic on three circulating biomarker-based liver scores: the FibroTest, SteatoTest and NashTest, from the Fibromax® panel. Among the main findings, the absence of OSA treatment emerged as independently associated with liver fibrosis and steatosis, when compared to effective treatment. However, besides the low number of treated patients, no polysomnographic respiratory data was provided, making it difficult to differentiate the impact of OSA from that of COPD in NAFLD prevalence. Furthermore, NAFLD diagnosis relied exclusively on circulating biomarker-based liver scores, without histological, imagery or other liver exploratory methods. Therefore, in this article, some methodological points are reminded and discussed, including the choice of OSA measurements, and the significance of ActiTest and AshTest scores from Fibromax® in this pathophysiological context.

Association between continuous positive airway pressure and serum aminotransferases in patients with obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) has been suggested to be a potential contributing factor for nonalcoholic fatty liver disease (NAFLD). Studies on the association between continuous positive airway pressure (CPAP) and NAFLD in OSA patients are limited and controversial.

OBJECTIVES

The aim of this study was to assess the relationship between OSA and NAFLD and the effect of CPAP therapy on serum aminotransferase levels in OSA patients.

METHODS

A total of 160 consecutive patients who underwent standard polysomnography were enrolled. Blood samples were obtained in the morning after sleep for biological profile measurements. Non-invasive ultrasound techniques were used to assess liver steatosis and fibrosis. Within the OSA group, serum aminotransferases were detected before and after CPAP treatment.

RESULTS

Alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase, and liver steatosis score increased significantly with an increase in OSA severity. Stepwise multiple regression with liver steatosis score, ALT, AST as dependent variable, respectively, apnea-hypopnea index (β = 0.447, p = 0.020; β = 0.266, p = 0.001; β = 0.351, p = 0.020, respectively) significantly predicted the liver steatosis score, ALT, AST after adjustment for confounders. After 3 months of CPAP treatment, there was a significant decrease in both ALT (54.20 ± 24.34 vs. 46.52 ± 24.95, p = 0.000) and AST (31.82 ± 8.91 vs. 29.00 ± 8.34, p = 0.039).

CONCLUSIONS

OSA severity was independently associated with liver steatosis and elevation of serum aminotransferases. 3 months of CPAP therapy were associated with a statistically significant improvement on liver injury in OSA patients.

Hepatic Cyp1a2 Expression Reduction during Inflammation Elicited in a Rat Model of Intermittent Hypoxia

BACKGROUND

Intermittent hypoxia (IH) is a key element of obstructive sleep apnea (OSA) that can lead to disorders in the liver. In this study, IH was established in a rat model to examine its effects on the expression of hepatic cytochrome P450 (CYP) and CYP regulators, including nuclear receptors.

METHODS

Hematoxylin and eosin staining was conducted to analyze the general pathology of the liver of rats exposed to IH. The messenger RNA (mRNA) expression levels of inflammatory cytokines, CYPs, nuclear factor-κB (NF-κB), and nuclear factors in the liver were measured by quantitative reverse transcription polymerase chain reaction.

RESULTS

We found inflammatory infiltrates in the liver of rats exposed to IH. The mRNA expression level of interleukin-1beta was increased in the liver of the IH-exposed rats (0.005 ± 0.001 vs. 0.038 ± 0.008, P = 0.042), whereas the mRNA expression level of Cyp1a2 was downregulated (0.022 ± 0.002 vs. 0.0050 ± 0.0002, P = 0.029). The hepatic level of transcription factor NF-κB was also reduced in the IH group relative to that in the control group, but the difference was not statistically significant and was parallel to the expression of the pregnane X receptor and constitutive androstane receptor. However, the decreased expression of the glucocorticoid receptor upon IH treatment was statistically significant (0.056 ± 0.012 vs. 0.032 ± 0.005, P = 0.035).

CONCLUSIONS

These results indicate a decrease in expression of hepatic CYPs and their regulator GR in rats exposed to IH. Therefore, this should be noted for patients on medication, especially those on drugs metabolized via the hepatic system, and close attention should be paid to the liver function of patients with OSA-associated IH.

Nonalcoholic fatty liver disease in chronic obstructive pulmonary disease

Nonalcoholic fatty liver disease (NAFLD) is independently linked to cardiometabolic morbidity and mortality. Low-grade inflammation, oxidative stress and ectopic fat, common features of chronic obstructive pulmonary disease (COPD), might contribute to the development of NAFLD.

We aimed to investigate the prevalence of NAFLD and to evaluate the relationship between various types of liver damage and COPD severity, comorbidities and circulating inflammatory cytokines. Validated noninvasive tests (FibroMax: SteatoTest, NashTest and FibroTest) were used to assess steatosis, nonalcoholic steatohepatitis (NASH) and liver fibrosis. Patients underwent an objective assessment of COPD comorbidities, including sleep studies. Biological parameters included a complete lipid profile and inflammatory markers.

In COPD patients the prevalence of steatosis, NASH and fibrosis were 41.4%, 36.9% and 61.3%, respectively. In multivariate analysis, SteatoTest and FibroTest were significantly associated with sex, body mass index (BMI), untreated sleep apnoea and insulin resistance, and, in addition, COPD Global Initiative for Chronic Obstructive Lung Disease stage for SteatoTest. Patients with steatosis had higher tumour necrosis factor-α levels and those with NASH or a combination of liver damage types had raised leptin levels after adjustment for age, sex and BMI.

We concluded that NAFLD is highly prevalent in COPD and might contribute to cardiometabolic comorbidities.

Association Between Severity of Obstructive Sleep Apnea and Blood Markers of Liver Injury

Obstructive sleep apnea (OSA) may contribute to the development of nonalcoholic fatty liver disease. We performed a multisite cross-sectional study to evaluate the association between the severity of OSA and blood markers of liver steatosis (using the hepatic steatosis index), cytolysis (based on alanine aminotransferase activity), and significant liver fibrosis (based on the FibroMeter [Echosens] nonalcoholic fatty liver disease score) in 1285 patients with suspected OSA in France. After adjusting for confounders including central obesity, the risk of liver steatosis increased with the severity of OSA (P for trend < .0001) and sleep-related hypoxemia (P for trend < .0003 for mean oxygen saturation). Decreasing mean oxygen saturation during sleep also was associated independently with a higher risk of liver cytolysis (P for trend < .0048). Severe OSA conferred an approximate 2.5-fold increase in risk for significant liver fibrosis compared with patients without OSA, but the association between OSA severity and liver fibrosis was not maintained after adjusting for confounders.

Mean apnea-hypopnea duration (but not apnea-hypopnea index) is associated with worse hypertension in patients with obstructive sleep apnea

To determine which polysomnography parameters are associated with severity of hypertension.This retrospective study collected data on all patients admitted to our urban, academic center in Beijing with hypertension who had undergone polysomnograms (PSG) and were diagnosed with obstructive sleep apnea (OSA) (apnea-hyponea index [AHI] ≥5/hour). We then compared polysomnographic parameters (AHI, oxygen desaturation index [ODI], lowest oxygen saturation [LOS], and mean apnea-hypopnea duration [MAD]) by hypertension severity in this cohort.There were 596 subjects who met entry criteria. Age, sex distribution, body mass index (BMI), history of current smoking and alcohol were similar among groups. Subjects with longer MAD suffered from more severe hypertension (P = 0.011). There were no relationship between AHI, ODI, and LOS and hypertension in our cohort. There were no significant differences in age, sex, BMI, history of current smoking and alcohol use between hypertension groups. MAD had a small but significant independent association (odds ratio [OR] = 1.072, 95% confidence interval [CI] 1.019-1.128, P = 0.007) with moderate to severe hypertension, using logistic regression analysis that accounted for age, sex, BMI, history of current smoking and alcohol, AHI, and LOS.Chinese inpatients with longer MAD by PSG face higher odds of moderate to severe hypertension. The mechanism of these effects may be due to aggravated nocturnal hypoxaemia and hypercapnia, as well as disturbed sleep architecture. These results suggest that additional information available in the polysomnogram, such as MAD, should be considered when evaluating OSA patients.

Gut epithelial barrier markers in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is now being recognized as an additional contributing factor to the pathogenesis of obesity-related comorbidities. At the same time, there is now increasing evidence to suggest that intestinal wall permeability plays a role in the development of metabolic syndrome. In the present study, circulating zonulin and fatty acid binding protein (I-FABP) were measured in association with metabolic, hepatic, and inflammatory parameters.

RESULTS

Compared with controls, plasma I-FABP levels were significantly higher in patients with OSA (571 pg/mL [IQR 290-950] vs 396 pg/mL [IQR 234-559], p = 0.04). Zonulin levels were similar between groups. Significant relationships were observed between zonulin levels and waist circumference (p < 0.05), glucose (p < 0.05), and insulin (p < 0.05). In addition, in the OSA group, zonulin levels correlated negatively with the mean nocturnal oxygenation saturation (p < 0.05) and positively with total cholesterol (p < 0.05), alanine aminotransferase (ALT) (p < 0.005), aminotransferase (AST) (p < 0.01), gamma glutamyltransferase (GGT) (p < 0.005), and high-sensitivity C-reactive protein (hs-CRP) (p < 0.05). Multivariate analysis showed that associations between zonulin and ALT, AST, and hs-CRP were attenuated, but not eliminated, after adjustment for other variables.

CONCLUSIONS

The results of this study suggest that OSA is a risk factor for intestinal damage, regardless of metabolic profile, and that intestinal permeability might be a possible contributor to nonalcoholic fatty liver disease in patients with OSA.

Nonalcoholic fatty liver disease and obstructive sleep apnea

Obstructive sleep apnea (OSA) and more importantly its hallmark, chronic intermittent hypoxia (CIH), are established factors in the pathogenesis and exacerbation of nonalcoholic fatty liver disease (NAFLD). This has been clearly demonstrated in rodent models exposed to intermittent hypoxia, and strong evidence now also exists in both paediatric and adult human populations. OSA and CIH induce insulin-resistance and dyslipidemia which are involved in NAFLD physiopathogenesis. CIH increases the expression of the hypoxia inducible transcription factor HIF1α and that of downstream genes involved in lipogenesis, thereby increasing β-oxidation and consequently exacerbating liver oxidative stress. OSA also disrupts the gut liver axis, increasing intestinal permeability and with a possible role of gut microbiota in the link between OSA and NAFLD. OSA patients should be screened for NAFLD and vice versa those with NAFLD for OSA. To date there is no evidence that treating OSA with continuous positive airway pressure (CPAP) will improve NAFLD but it might at least stabilize and slow its progression. Nevertheless, these multimorbid patients should be efficiently treated for all their metabolic co-morbidities and be encouraged to follow weight stabilization or weight loss programs and physical activity life style interventions.

Obstructive sleep apnea is associated with fatty liver index, the index of nonalcoholic fatty liver disease

BACKGROUND AND OBJECTIVES

The relationship between obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease (NAFLD) is gaining increased attention. The aim of the present study was to examine the relationship of OSA with NAFLD defined by an elevated fatty liver index (FLI).

MATERIALS AND METHODS

A total of 319 consecutive patients who underwent standard polysomnography were enrolled. Fasting blood samples were obtained from all patients for biological profile measurements, and demographic data were collected. Values of FLI were determined and assessed as predictors of the presence of NAFLD, as measured by ultrasound. The discriminative ability of FLI was estimated on the basis of the area under the receiver operator characteristic curve.

RESULTS

An FLI of 60 achieved the highest diagnostic accuracy and yielded an area under the receiver operator characteristic curve of 0.822 (95% confidence interval: 0.729-0.916) in the detection of NAFLD. Patients with an FLI of 60 or higher had a significantly lower lowest O2 saturation (73 vs. 83%, P<0.001), a lower mean nocturnal oxygen saturation (93 vs. 95%, P<0.001), a higher apnea-hypopnea index (39.7 vs. 18.4, P<0.001), a higher oxygen desaturation index (39 vs. 10.6, P<0.001), and a higher percentage of sleep time spent with SpO2 less than 90% (4.63 vs. 0.92%, P<0.001) compared with those with FLI less than 60. In multivariate analysis, the presence of OSA was independently associated with elevated FLI after adjusting for confounding factors (odds ratio: 5.141, 95% confidence interval: 1.414-18.696, P=0.013).

CONCLUSION

Our results suggest a positive association between the severity of OSA and NAFLD defined by an elevated FLI, which may serve as a good biomarker for detecting NAFLD in OSA patients.

Nonalcoholic fatty liver disease as a multi-systemic disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. NAFLD includes a wide spectrum of liver conditions ranging from simple steatosis to nonalcoholic steatohepatitis and advanced hepatic fibrosis. NAFLD has been recognized as a hepatic manifestation of metabolic syndrome linked with insulin resistance. NAFLD should be considered not only a liver specific disease but also an early mediator of systemic diseases. Therefore, NAFLD is usually associated with cardiovascular disease, chronic kidney disease, type 2 diabetes, obesity, and dyslipidemia. NAFLD is highly prevalent in the general population and is associated with increased cardiovascular morbidity and mortality. The underlying mechanisms and pathogenesis of NAFLD with regard to other medical disorders are not yet fully understood. This review focuses on pathogenesis of NAFLD and its relation with other systemic diseases.

Extrahepatic Manifestations of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide with an increased prevalence of metabolic, macro- and microvascular complications. The primary causes of mortality in NAFLD are cardiovascular disease (CVD), malignancy and liver disease. NAFLD is a multisystem disease that affects a variety of extra-hepatic organ systems. The main focus of this review is to summarize the reported extra-hepatic associations, which include CVD, chronic kidney disease, obstructive sleep apnea, osteoporosis, psoriasis, colorectal cancer, iron overload and various endocrinopathies (e.g. type 2 diabetes mellitus, thyroid dysfunction, and polycystic ovarian syndrome). Due to the systemic manifestations of NAFLD patients require a multidisciplinary assessment and may benefit from more rigorous surveillance and early treatment interventions to decrease mortality related to malignancy or cardiometabolic diseases.

Liver Steatosis and Fibrosis in OSA patients After Long-term CPAP Treatment: A Preliminary Ultrasound Study

In cases of morbid obesity, obstructive sleep apnea (OSA) was associated with biopsy-proven liver damage. The role of non-invasive techniques to monitor liver changes during OSA treatment with continuous positive airway pressure (CPAP) is unknown. We used non-invasive ultrasound techniques to assess liver steatosis and fibrosis in severe OSA patients at diagnosis and during long-term CPAP treatment. Fifteen consecutive patients with severe OSA (apnea hypopnea index 52.5 ± 19.1/h) were studied by liver ultrasound and elastography (Fibroscan) at 6-mo (n = 3) or 1-y (n = 12) follow-up. Mean age was 49.3 ± 11.9 y, body mass index (BMI) was 35.4 ± 6.4 kg/m(2). Adherence to CPAP was ≥5 h/night. At baseline, most patients had severe liver steatosis independent of BMI; at follow-up, liver steatosis was not statistically different, but a relationship between severity of steatosis and BMI became apparent (Spearman's rho: 0.53, p = 0.03). Significant fibrosis as assessed by Fibroscan was absent at diagnosis or follow-up (failure or unreliable measurements in four markedly obese patients). Therefore, ultrasound liver assessment is feasible in most OSA patients, and CPAP treatment may positively affect liver steatosis.

Can upper airway surgery for OSA protect against cardiovascular sequelae via effects on coagulation?

CONCLUSION

Upper airway surgery is associated with salutary effects on the blood coagulation characteristics of OSA patients, a benefit that may be protective against cardiac and cerebrovascular morbidity and mortality.

OBJECTIVE

Increased blood coagulation is an important factor linking OSA and cardiovascular complications. Surgery is an important method to treat OSA, but the effect of surgery on blood coagulation in OSA patients is unknown.

METHODS

the authors performed a prospective clinical trial of adult OSA patients who underwent surgery from 2012-2014. Pre-operative and post-operative blood coagulation parameters and polysomnography (PSG) results were compared.

RESULT

There were 61 subjects. The total rate of success in curing OSA was 11.5%. The rate of response after surgery was 40.8%. Overall, the Apnea-Hypopnea Index (AHI) improved after surgery (from 39.8 3 ± 24.49 to 25.9 7 ± 18.53, p < 0.01). After surgery, serum platelet counts (PLT) decreased (from 242.5 ± 52.6 to 230.9 ± 40.7, p=0.01), and Fibrinogen (FIB) levels declined (from 262.5 ± 52.5 to 247.3 ± 44.4, p = 0.02). Other blood coagulation parameters also improved: prothrombin time (PT) (from 10.6 2 ± 0.62 to 10.8 6 ± 0.70, p=0.01), activated partial thromboplastin time (APTT) (from 26.9 8 ± 4.94 to 27.7 8 ± 3.02, p = 0.06), and Thrombin time (TT) (from 19.5 3 ± 0.84 to 20.1 1 ± 1.31, p < 0.01).

Impact of effective versus sham continuous positive airway pressure on liver injury in obstructive sleep apnoea: Data from randomized trials

BACKGROUND AND OBJECTIVE

Obstructive sleep apnoea (OSA) could be an independent risk factor for non-alcoholic fatty liver disease (NAFLD) occurrence and progression. The impact of continuous positive airway pressure (CPAP) treatment on non-invasive markers of NAFLD has not been studied. The aim of this study was to evaluate the effect of 6-12 weeks of effective CPAP on the FibroMax test (comprising components including the SteatoTest, NashTest and FibroTest) through three randomized sham controlled studies.

METHODS

The FibroMax test was performed in 103 obstructive sleep apnoea patients (apnoea + hypopnoea index > 15/h) enrolled in a randomized study comparing sham versus effective CPAP.

RESULTS

At baseline, 40.4% of patients in the sham CPAP group and 45.5% in the CPAP group exhibited liver steatosis. Furthermore, 39.6% of patients in the sham CPAP group and 58.4% in the CPAP group displayed borderline or possible non-alcoholic steatohepatitis (NASH). Six to twelve weeks of effective CPAP did not demonstrate any impact on reducing steatosis, NASH or liver fibrosis even after adjustment for gender, BMI, baseline apnoea + hypopnoea index and severity of liver injury.

CONCLUSION

A number of non-invasive markers of liver damage are increased in untreated obstructive sleep apnoea patients, potentially contributing to cardiometabolic risk, but they do not improve after 6-12 weeks of effective CPAP treatment.

CLINICAL TRIAL REGISTRATION

NCT01196845 (ADISAS), NCT00464659 (MneSAS) and NCT00669695 (StatinflaSAS) at ClinicalTrials.gov.

Obstructive sleep apnea with excessive daytime sleepiness is associated with non-alcoholic fatty liver disease regardless of visceral fat

BACKGROUND/AIMS

Obstructive sleep apnea (OSA) is associated with an increased risk of obesity and non-alcoholic fatty liver disease (NAFLD), but it remains unclear whether the risk of NAFLD is independently related to OSA regardless of visceral obesity. Thus, the aim of the present study was to examine whether OSA alone or in combination with excessive daytime sleepiness (EDS) or short sleep duration was associated with NAFLD independent of visceral fat in Korean adults.

METHODS

A total of 621 participants were selected from the Korean Genome and Epidemiology Study (KoGES). The abdominal visceral fat area (VFA) and hepatic fat components of the participants were assessed using computed tomography scans and they were then categorized into four groups depending on the presence of OSA and EDS.

RESULTS

The proportions of NAFLD were 21.1%, 18.5%, 32.4%, and 46.7% in participants without OSA/EDS, with only EDS, with only OSA, and with both OSA and EDS, respectively. A combination of OSA and EDS increased the odds ratio (OR) for developing NAFLD (OR, 2.75; 95% confidence interval [CI], 1.21 to 6.28) compared to those without OSA/EDS, and this association remained significant (OR, 2.38; 95% CI, 1.01 to 5.59) even after adjusting for VFA. In short sleepers (< 5 hours) with OSA, the adjusted OR for NAFLD was 2.50 (95% CI, 1.08 to 5.75) compared to those sleeping longer than 5 hours without OSA.

CONCLUSIONS

In the present study, OSA was closely associated with NAFLD in Korean adults. This association was particularly strong in those with EDS or short sleep duration regardless of VFA.

Lysyl Oxidase as a Serum Biomarker of Liver Fibrosis in Patients with Severe Obesity and Obstructive Sleep Apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with the progression of nonalcoholic fatty liver disease (NAFLD). We hypothesized that the hypoxia of OSA increases hepatic production of lysyl oxidase (LOX), an enzyme that cross-links collagen, and that LOX may serve as a biomarker of hepatic fibrosis.

DESIGN

Thirty-five patients with severe obesity underwent liver biopsy, polysomnography, and serum LOX testing. A separate group with severe OSA had serum LOX measured before and after 3 mo of CPAP or no therapy, as did age-matched controls. LOX expression and secretion were measured in mouse hepatocytes following exposure to hypoxia.

SETTING

The Johns Hopkins Bayview Sleep Disorders Center, and the Hypertension Unit of the Heart Institute at the University of São Paulo Medical School.

MEASUREMENTS AND RESULTS

In the bariatric cohort, the apnea-hypopnea index was higher in patients with hepatic fibrosis than in those without fibrosis (42.7 ± 30.2 events/h, versus 16.2 ± 15.5 events/h; P = 0.002), as was serum LOX (84.64 ± 29.71 ng/mL, versus 45.46 ± 17.16 ng/mL; P < 0.001). In the sleep clinic sample, patients with severe OSA had higher baseline LOX than healthy controls (70.75 ng/mL versus 52.36 ng/mL, P = 0.046), and serum LOX decreased in patients with OSA on CPAP (mean decrease 20.49 ng/mL) but not in untreated patients (mean decrease 0.19 ng/mL). Hypoxic mouse hepatocytes demonstrated 5.9-fold increased LOX transcription (P = 0.046), and enhanced LOX protein secretion.

CONCLUSIONS

The hypoxic stress of obstructive sleep apnea may increase circulating lysyl oxidase (LOX) levels. LOX may serve as a biomarker of liver fibrosis in patients with severe obesity and nonalcoholic fatty liver disease.