Obstructive Sleep Apnea Is Associated with Nonalcoholic Steatohepatitis and Advanced Liver Histology

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.

Potential Therapeutic Targets in Obesity, Sleep Apnea, Diabetes, and Fatty Liver Disease

Obesity and metabolic syndrome affect the majority of the US population. Patients with obesity are at increased risk of developing type 2 diabetes (T2DM), obstructive sleep apnea (OSA), and metabolic dysfunction-associated steatotic liver disease (MASLD), each of which carry the risk of further complications if left untreated and lead to adverse outcomes. The rising prevalence of obesity and its comorbidities has led to increased mortality, decreased quality of life, and rising healthcare expenditures. This phenomenon has resulted in the intensive investigation of exciting therapies for obesity over the past decade, including more treatments that are still in the pipeline. In our present report, we aim to solidify the relationships among obesity, T2DM, OSA, and MASLD through a comprehensive review of current research. We also provide an overview of the surgical and pharmacologic treatment classes that target these relationships, namely bariatric surgery, the glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon receptor agonists.

Non-alcoholic fatty liver disease and sleep disorders

Studies have shown that non-alcoholic fatty liver disease (NAFLD) may be associated with sleep disorders. In order to explore the explicit relationship between the two, we systematically reviewed the effects of sleep disorders, especially obstructive sleep apnea (OSA), on the incidence of NAFLD, and analyzed the possible mechanisms after adjusting for confounding factors. NAFLD is independently associated with sleep disorders. Different sleep disorders may be the cause of the onset and aggravation of NAFLD. An excessive or insufficient sleep duration, poor sleep quality, insomnia, sleep-wake disorders, and OSA may increase the incidence of NAFLD. Despite that some research suggests a unidirectional causal link between the two, specifically, the onset of NAFLD is identified as a result of changes in sleep characteristics, and the reverse relationship does not hold true. Nevertheless, there is still a lack of specific research elucidating the reasons behind the higher risk of developing sleep disorders in individuals with NAFLD. Further research is needed to establish a clear relationship between NAFLD and sleep disorders. This will lay the groundwork for earlier identification of potential patients, which is crucial for earlier monitoring, diagnosis, effective prevention, and treatment of NAFLD.

Sleep Apnea, Obesity, and Diabetes - an Intertwined Trio

PURPOSE OF REVIEW

To synthesize the existing literature regarding the complex interplay between sleep disturbance, obesity, and diabetes. The review emphasizes the three pillars of health being diet, exercise, and sleep, with the notion that if one is ignored, then the other two could suffer.

RECENT FINDINGS

Sleep deprivation is associated with incident obesity, perhaps mediated by dysregulation in leptin and ghrelin - hormones important in regulation of appetite. Sleep apnea is very common particularly among obese people with type 2 diabetes mellitus. Treatment of sleep apnea has clear symptomatic benefits although its impact on long-term cardiometabolic health is less clear. Sleep disturbance may be an important modifiable risk for patients at risk of cardiometabolic disease. An assessment of sleep health may be an important component of the comprehensive care of patients with obesity and diabetes mellitus.

OBSTRUCTIVE SLEEP APNEA SYNDROME RISK IN PATIENTS WITH NON-ALCOHOLIC FATTY LIVER DISEASE IS ASSOCIATED WITH OBESITY AND PRESENCE OF NASH

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and refers to a wide spectrum of histological abnormalities ranging from simple steatosis (HE) to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma.

OBJECTIVE

To assess the risk of obstructive sleep apnea syndrome (OSAS) and relating it to demographic, biochemical and histological data in patients with non-alcoholic fatty liver disease.

METHODS

Cross-sectional cohort study in individuals with biopsy-proven NAFLD. Anthropometric and biochemical parameters, presence of metabolic syndrome and insulin resistance were evaluated. The Berlin Questionnaire (BQ) was applied to assess the risk of apnea and a food record was requested. Based on the BQ, participants were classified as high or low risk for OSAS. In the correlation of sleep apnea with the severity of NAFLD, presence of nonalcoholic steatohepatitis (NASH) and the degree of liver fibrosis were evaluated. Statistical analysis used the chi-square test, Student's t and bivariate logistic regression; values were expressed as mean ± standard deviation. This research project was approved by the Ethics Committee.

RESULTS

Regarding the parameters evaluated, significant differences were observed between the groups in terms of body mass index (BMI), waist and neck circumference. In the histological evaluation, patients classified as high risk were more likely to have fibrosis and NASH. In bivariate regression, the BMI, presence of fibrosis and steatohepatitis in the biopsy were independently associated with an elevated risk of the syndrome.

CONCLUSION

A high prevalence of risk for OSAS was observed in the studied group, with a higher risk being independently associated with BMI and presence of steatohepatitis, suggesting that it is a factor associated with the severity of the disease.

A clinical overview of non-alcoholic fatty liver disease: A guide to diagnosis, the clinical features, and complications-What the non-specialist needs to know

Non-alcoholic fatty liver disease (NAFLD) has a rapidly rising prevalence worldwide and is the most common cause of liver disease in developed countries. In this article, we discuss the spectrum of disease of NAFLD with a focus on the earlier spectrum of the disease that is commonly encountered by non-specialists, as well as the hepatic and extra-hepatic associations of the disease. We discuss in detail the two common presentations of NAFLD, incidentally detected hepatic steatosis and asymptomatic raised liver enzymes, and provide an algorithm for management and continued to follow up for these patients. Considerations for the management of cardiovascular comorbidities in these patients are also discussed. Finally, we cover the topic of screening for NAFLD in high-risk populations.

Association of obstructive sleep apnea with non-alcoholic fatty liver disease in patients with obesity: an observational study

PURPOSE

Obstructive Sleep Apnea (OSA) is associated with the presence and severity of Non-Alcoholic Fatty Liver Disease (NAFLD). We aimed to investigate the relationship between the severity of OSA and NAFLD and to recognize a polysomnographic parameter correlated with progression of fibrosis, determined by a non-invasive score of liver fibrosis, FIBrosis-4 index (FIB-4), in patients affected by severe obesity and OSA.

METHODS

We enrolled 334 patients (Body Mass Index, BMI 44.78 ± 8.99 kg/m²), divided into classes according to severity of OSA evaluated with Apnea Hypopnea Index (AHI): OSAS 0 or absent (17%), mild OSA (26%), moderate OSA (20%), severe OSAS (37%). We studied anthropometric, polysomnographic, biochemical data and FIB-4. A multiple regression model was computed to identify a polysomnographic independent predictor of FIB-4 among those parameters previously simple correlated with FIB-4.

RESULTS

The severity of OSA was associated with a decrease in High-Density Lipoprotein-cholesterol (HDL) and an increase in BMI, triglycerides, Homeostasis model assessment insulin-resistance index (HOMA), transaminases and FIB-4. FIB-4 correlated with sex, age, BMI, AHI, mean percentage oxyhaemoglobin (meanSaO2%), number of desaturations, platelets, transaminases, HDL, triglycerides and HOMA. The only variables independently related to FIB-4 were sex, BMI, triglycerides and meanSpO2 (r = 0.47, AdjRsqr = 0.197).

CONCLUSION

MeanSpO2% represented an independent determinant for the worsening of FIB-4 in patients with severe obesity and OSA. Hence, it could hypothesize a clinical role of meanSaO2% in recognizing patients with obesity and OSA and higher risk of developing advanced fibrosis and, thus, to undergo further investigation.

LEVEL III

Evidence obtained from well-designed cohort analytic studies.

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.

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.

NAFLD and autoimmune hepatitis: Do not judge a book by its cover

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease (almost 25% of the general population). Autoimmune hepatitis (AIH) is a relatively rare liver disease of unknown aetiology characterized by female predominance and large heterogeneity regarding epidemiology, clinical manifestations, genetics, serology and liver pathology. The potential NAFLD/AIH coincidence or an AIH diagnosis alone instead of NAFLD represent a challenge for clinicians, both in making a correct and timely diagnosis but also in the management of these diseases. The diagnosis of both diseases can be challenging as: (a) reliable laboratory tests to confidently diagnose or exclude NAFLD or AIH are missing; (b) physicians and pathologists are much more familiar with a very common disease like NAFLD so, they do not consider an alternative or additional diagnosis; (c) most NAFLD studies do not investigate the patients for all autoantibodies involved in AIH diagnosis, apply the diagnostic scoring systems for AIH or address the possibility of AIH features on liver histology and (d) the recent European and American practice guidelines for NAFLD do not mention clearly the importance of IgG determination and liver autoimmune serology according to the AIH guidelines. Patients with NAFLD/AIH coincidence have significantly more frequently hypertension, diabetes, obesity, older age, lower transaminases, bilirubin and simplified score for AIH diagnosis but no female predominance compared to AIH patients only. The true outcome of NAFLD/AIH patients is practically unknown while their management is quite problematic because official clinical practice guidelines for this condition are missing.

NAFLD: comorbidity and associated diseases

Non-alcoholic fatty liver disease (NAFLD) went beyond the competence of a gastroenterologist and acquired the character of a multidisciplinary problem. NAFLD requires the attention of many professionals. A characteristic feature of NAFLD is the variety of concomitant diseases and pathological conditions with common pathophysiological mechanisms. This review summarizes and presents the data available in the modern literature on the association of NAFLD with cardiovascular diseases, type 2 diabetes mellitus, hypothyroidism, polycystic ovary syndrome, chronic kidney disease, colorectal cancer, obstructive sleep apnea, osteoporosis, psoriasis.

[Epidemiology of non-alcoholic steatohepatitis. Extent/burden of the problem and its impact on public health]

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of liver disease, the most common cause of chronic liver function augmentation and it will be the most common indication for liver transplantation in 2020. The prevalence of NAFLD has increased over time in line with the increase of obesity and type 2 diabetes. There is a discrepancy between the studies concerning the prevalence of NAFLD because of the different diagnostic methods used (ultrasound or magnetic resonance, fibroscan, controlled attenuation parameter (CAP), histology). Because of its high prevalence the impact of NAFLD in public health is real. Therapeutic advances must be made to better understand the natural history of NAFLD and improve the management of this emerging liver disease.

A Wake-up Call for Human Immunodeficiency Virus (HIV) Providers: Obstructive Sleep Apnea in People Living With HIV

Obstructive sleep apnea (OSA) is defined by repetitive collapse of the upper airway during sleep leading to transient hypoxemia and arousals from sleep. Surges in sympathetic activity, repeated oxygen desaturation, and sleep fragmentation can lead to cardiovascular (eg, myocardial infarction) and neurocognitive (eg, excessive daytime sleepiness) consequences. Emerging data suggest that OSA is common in people living with human immunodeficiency virus (PLWH) and that traditional risk factors for OSA, such as obesity, are not highly predictive of OSA in PLWH. Untreated OSA is associated with increased fatigue and levels of inflammation. Despite these data, most PLWH with OSA remain undiagnosed and untreated. Improved awareness of OSA among healthcare providers and greater use of OSA diagnostic approaches have the potential to substantially improve quality of life and outcomes in PLWH.

Hypoxia Suppresses High Fat Diet-Induced Steatosis And Development Of Hepatic Adenomas

Purpose

Nonalcoholic fatty liver disease (NAFLD) is considered the most common form of silent liver disease in the United States and obesity is associated with increased risk of NAFLD. Obstructive sleep apnea (OSA) which is common in obese individuals is associated with a greater incidence of NAFLD, which in turn, increases the risk for hepatocellular carcinoma (HCC). It is unclear how obesity, OSA and NAFLD interrelate nor how they collectively contribute to an increased risk for developing HCC.

Patients and methods

Male BALB/c mice were exposed to diethylnitrosamine and phenobarbital followed by 48 weeks of either standard chow diet (chow), chow with hypoxia, high-fat diet, or a combination of hypoxia and high-fat diet. We noninvasively monitored tumor development using micro-CT imaging. We tracked the total weight gained throughout the study. We evaluated liver histology, fat accumulation, carbonic anhydrase 9 (CA9) and hypoxia-inducible factor 1-alpha (HIF-1α) expression, as well as, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT).

Results

A high-fat diet without hypoxia led to the development of obesity that induced hepatic steatosis and promoted tumorigenesis. Animals on a high-fat diet and that were also exposed to hypoxia had lower total weight gain, lower steatosis, lower serum AST and ALT levels, and fewer number of hepatic adenomas than a high-fat diet without hypoxia.

Conclusion

These findings suggest that hypoxia abrogates obesity, hepatic steatosis, and hepatic tumorigenesis related to a high-fat diet.

Association between non-alcoholic fatty liver disease and decreased lung function in adults: A systematic review and meta-analysis

AIM

] and forced vital capacity [FVC]).

METHODS

We searched publication databases using predefined keywords to identify studies (published up to October 4, 2018), in which NAFLD was diagnosed by imaging or biochemistry (no studies with biopsy-proven NAFLD were available). Data from selected studies were extracted, and meta-analysis was performed using random-effects modelling.

RESULTS

and FVC at baseline were also independently associated with a ∼ 15% increased risk of incident NAFLD (n = 1 study in Korean individuals). Subgroup analyses did not materially modify these findings.

CONCLUSIONS

and FVC in Asian and United States adults, and such small, but significant, reductions of lung volumes at baseline may be also associated with increased NAFLD incidence in Asian individuals. Further research is needed to better elucidate the link between NAFLD and impaired lung volumes.

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.

Magnitude of Nonalcoholic Fatty Liver Disease: Western Perspective

The incidence of nonalcoholic fatty liver disease (NAFLD) is continuing to rise worldwide, and it is estimated that this disquieting trend will continue for another 10-15 years before prevalence begins to decrease. NAFLD is the hepatic manifestation of metabolic syndrome. As obesity, diabetes, and other lifestyle-related diseases continue to rise, the spectrum of NAFLD, e.g., nonalcoholic steatohepatitis, liver fibrosis, liver cirrhosis, liver-related morbidity, and mortality, will increase in parallel. Its widespread prevalence and associated economic burden have drawn significant attention, and a multitude of pharmaceutical companies are participating in active research trying to find a "cure". Unfortunately, as of now, no targeted treatment exists to treat this condition, and therefore, emphasis has been on its prevention. The current review focuses on the epidemiology, clinical characteristics, risk factors, and clinical outcomes of NAFLD in Western countries. It is important to understand the magnitude of NAFLD and its risk factors in Western countries where the prevalence of NAFLD has now reached epidemic proportions to identify the best strategy to prevent and possibly control this epidemic.

The association between glycometabolism and nonalcoholic fatty liver disease in patients with obstructive sleep apnea

Purpose

Growing evidence has revealed that nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes. This study aimed to assess the association between glycometabolism and NAFLD in patients with obstructive sleep apnea (OSA).

Methods

Patients with suspected OSA were enrolled consecutively and then underwent polysomnography, liver ultrasound, and biochemical measurements. Logistic regressions were used to identify factors associated with NAFLD.

Results

In total, 415 patients were included. The prevalence of NAFLD in the non-OSA, mild OSA, moderate OSA, and severe OSA groups was 37.21%, 69.09%, 68.34%, and 78.08%, respectively. Stepwise logistic regression suggested that percentage of total sleep time spent with oxygen saturation of < 90% (TS90), lowest oxygen saturation (LaSO₂), and homeostatic model assessment of insulin resistance (HOMA-IR) were independently associated with NAFLD in all subjects, after adjusting for confounders (odds ratio [OR] = 1.037, p = 0.014; OR = 1.056, p = 0.004; OR = 0.732, p = 0.009; respectively). TS90, LaSO₂, and HOMA-IR were also independent predictors for NAFLD in patients with mild and moderate OSA, whereas TS90, LaSO₂, and ODI were independent predictors for NAFLD in patients with severe OSA.

Conclusions

There is a relationship between OSA and NAFLD, and the combination of disordered glycometabolism and intermittent hypoxia may act as a “two hit” mechanism to promote the development of NAFLD. Furthermore, intermittent hypoxia alone was an independent predictor for NAFLD in severe OSA patients.

Sleep apnea, metabolic disease, and the cutting edge of therapy

Obstructive sleep apnea (OSA) is common, and many cross-sectional and longitudinal studies have established OSA as an independent risk factor for the development of a variety of adverse metabolic disease states, including hypertension, insulin resistance, type 2 diabetes, nonalcoholic fatty liver disease, dyslipidemia, and atherosclerosis. Nasal continuous positive airway pressure (CPAP) has long been the mainstay of therapy for OSA, but definitive studies demonstrating the efficacy of CPAP in improving metabolic outcomes, or in reducing incident disease burden, are lacking; moreover, CPAP has variable rates of adherence. Therefore, the future of OSA management, particularly with respect to limiting OSA-related metabolic dysfunction, likely lies in a coming wave of alternative approaches to endophenotyping OSA patients, personalized care, and defining and targeting mechanisms of OSA-induced adverse health outcomes.

Association between obstructive sleep apnea and non-alcoholic fatty liver disease: a systematic review and meta-analysis

The relationship between obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) has been an issue of great concern. The primary purpose of this study was to determine the influence of OSA on the levels of liver enzymes including alanine transaminase (ALT) and aspartate transaminase (AST). The secondary purpose was to estimate the effect of OSA on the histological lesions of NAFLD, such as steatosis, lobular inflammation, ballooning degeneration, fibrosis, as well as NAFLD activity score (NAS). A systematic literature review using PubMed, Cochrane Library, Embase, and Ovid technologies from January 2007 to April 2017 was performed, and 9 studies (2272 participants) that met the selection criteria were evaluated. The present study demonstrated that OSA was related to ALT levels, but no significant correlation was found with AST levels. The subgroup analysis showed that the severity of OSA was associated with ALT levels, not with AST levels. The meta-regression analysis showed that age, sex, homeostasis model assessment, diabetes mellitus, body mass index, and waist circumference did not have a significant effect on the levels of ALT and AST. OSA was also found to be significantly correlated with steatosis, lobular inflammation, ballooning degeneration, and fibrosis, but was not correlated with NAS. OSA was independently related to the development and progression of NAFLD in terms of liver enzyme level and histological alterations. Future studies should investigate the possible relevant mechanisms, thereby guiding the exploration of potential therapeutic implications to prevent the progression of disease.

The association of nonalcoholic steatohepatitis and obstructive sleep apnea

BACKGROUND AND AIM

The association between obstructive sleep apnea (OSA) and abnormal liver enzymes has been reported in multiple studies. The existing literature regarding the relationship between OSA and nonalcoholic steatohepatitis (NASH) is conflicting. Thus we aimed to determine the relationship between OSA and NASH from a large database.

PATIENTS AND METHODS

A cross-sectional study was performed using the 2012 Nationwide Inpatient Sample. We identified adult patients (18-90 years) who had a diagnosis of OSA using the International Classification of Diseases 9th version codes. The control group was comprised of adult individuals with no discharge records of OSA. NASH diagnosis was also identified using the International Classification of Diseases 9th version codes. The association between OSA and NASH was calculated using univariable and multivariable logistic regression.

RESULTS

A total of 30 712 524 hospitalizations were included. The OSA group included 1 490 150 patients versus 29 222 374 in the control non-OSA group. The OSA group average age was 61.8±0.07 years (44.2% females) compared with 57.0±0.11 years (60.1% females) in the non-OSA group. NASH prevalence was significantly higher in the OSA group compared with the non-OSA group [2% (95% confidence interval (CI): 1.9, 2.1) vs. 0.65% (95% CI: 0.63, 0.66), P<0.001]. After adjusting for obesity, diabetes, hypertension, dyslipidemia, the metabolic syndrome and Charlson comorbidity index, OSA patients were three times more likely to have NASH [adjusted odds ratio: 3.1 (95% CI: 3.0-3.3), P<0.001].

CONCLUSION

Patients with OSA are three times more likely to have NASH compared with patients without OSA after controlling for other confounders. These data indicate that OSA should be considered as an independent risk factor for developing NASH.

Intermittent hypoxia is a proinflammatory stimulus resulting in IL-6 expression and M1 macrophage polarization

The biological factors that promote inflammation or nonalcoholic steatohepatitis (NASH) in the setting of nonalcoholic fatty liver disease remain incompletely understood. Clinical studies have demonstrated an association between obstructive sleep apnea (OSA) and both inflammation and fibrosis in NASH, but the mechanism has not been identified. In this study, we use in vitro modeling to examine the impact of intermittent hypoxia on the liver. Hepatocyte, stellate cell, and macrophage cell lines were exposed to intermittent or sustained hypoxia. Candidate genes associated with inflammation, fibrosis, and lipogenesis were analyzed. Circulating cytokines were assessed in human serum of patients with nonalcoholic fatty liver disease. Intermittent hypoxia results in significant induction of interleukin (IL)-6 expression in both hepatocytes and macrophages. The increase in IL-6 expression was independent of hypoxia inducible factor 1 induction but appeared to be in part related to antioxidant response element and nuclear factor kappa B activation. Mature microRNA 365 (miR-365) has been demonstrated to regulate IL-6 expression, and we found that miR-365 expression was decreased in the setting of intermittent hypoxia. Furthermore, macrophage cell lines showed polarization to an M1 but not M2 phenotype. Finally, we found a trend toward higher circulating levels of IL-6 in patients with OSA and NASH. Conclusion: Intermittent hypoxia acts as a potent proinflammatory stimulus, resulting in IL-6 induction and M1 macrophage polarization. Increased IL-6 expression may be due to both induction of antioxidant response element and nuclear factor kappa B as well as inhibition of miR-365 expression. Higher levels of IL-6 were observed in human samples of patients with OSA and NASH. These findings provide biological insight into mechanisms by which obstructive sleep apnea potentiates inflammation and fibrosis in patients with fatty liver disease. (Hepatology Communications 2017;1:326-337).

The Association Between IGF-1 Levels and the Histologic Severity of Nonalcoholic Fatty Liver Disease

Objectives:

The mechanisms responsible for the development of nonalcoholic fatty liver disease (NAFLD) and progression to nonalcoholic steatohepatitis (NASH) are incompletely understood. Growing evidence suggests that growth hormone (GH) and insulin-like growth factor-1 (IGF-1) may have roles in the development and progression of NAFLD. We hypothesized that lower serum IGF-1 levels would be associated with increased liver fat accumulation, inflammation, and fibrosis in a group of meticulously phenotyped obese subjects with liver biopsies.

Methods:

A retrospective, cross-sectional study was performed at Massachusetts General Hospital, Boston, MA, USA and St. Mary's Hospital, Richmond, VA, USA. Liver biopsies were performed in 142 subjects during NAFLD work-up or bariatric surgery and were graded by a single, blinded pathologist. Main outcome measures included liver histology and serum IGF-1.

Results:

Mean age was 52±10 years and body mass index (BMI) was 43±9 kg/m². Mean serum IGF-1 was lower in subjects with lobular inflammation (112±47 vs. 136±57 ng/ml, P=0.01), hepatocyte ballooning (115±48 vs. 135±57 ng/ml, P=0.05), higher fibrosis stage (stage 2–4 vs. 0–1; 96±40 vs. 125±51 ng/ml, P=0.005), and NASH (109±45 vs. 136±57 ng/ml, P=0.002). All results remained significant after controlling for age, BMI, and a diagnosis of diabetes, and all but hepatocyte ballooning (trend, P=0.06) remained significant after excluding individuals with cirrhosis. Steatosis was not significantly associated with mean serum IGF-1 levels.

Conclusions:

Low serum IGF-1 levels are associated with increased histologic severity of NAFLD when rigorously controlled for age, BMI, the presence of diabetes, and after the exclusion of subjects with cirrhosis. Further investigation is warranted to determine the differential effects of GH and IGF-1 on the development and progression of NAFLD, which could further elucidate pathophysiology and identify therapeutic targets.

Association between metabolic syndrome and liver histology among NAFLD patients without diabetes

BACKGROUND

Metabolic syndrome (MetS) and obesity are associated with non-alcoholic fatty liver disease (NAFLD). The aim of this observational study was to examine the relationship of MetS and a diagnosis of non-alcoholic steatohepatitis (NASH) in patients without diabetes in the NASH Clinical Research Network (CRN).

METHODS

Clinical, demographic, histological, laboratory and anthropometric data were collected on 356 adult patients without diabetes with NAFLD. Obesity was defined as body mass index ≥30.0. MetS was determined using the National Cholesterol Education Program-Adult Treatment Panel III (NCEP ATPIII) 2001 criteria to include 3 or more of the following: increased waist circumference, elevated triglycerides, reduced high-density lipoprotein cholesterol, hypertension and elevated fasting blood glucose.

RESULTS

Most patients were obese (71%) and had MetS (67%). Obesity was more prevalent among patients with MetS (80% vs 52%; p≤0.001). Markers of insulin resistance such as homoeostasis model assessment of insulin resistance (6.5 vs 4.9, p≤0.001) were higher among those with MetS compared with those without MetS. Histologically, patients without MetS had higher hepatocellular (p=0.04) and reticuloendothelial system iron (p=0.04). Patients with MetS were more likely to have severe hepatic steatosis (p=0.04) and chronic portal inflammation (p=0.01). On multiple logistic regression analysis, patients with definite NASH were almost 2.5 times more likely to have MetS than those without definite NASH (OR=2.41, p=0.01).

CONCLUSIONS

MetS is common in patients without diabetes with NAFLD and is associated with greater insulin resistance, hepatic steatosis and portal inflammation. While patients without MetS have greater iron overload, patients with MetS may have an increased propensity to have NASH. Therefore, presence of MetS in patients without diabetes with NAFLD may serve as a potential criterion for liver biopsy.

TRIAL REGISTRATION NUMBER

NCT00063622; Pre-results.

Extrahepatic Complications of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is an important cause of liver disease that is often associated with the metabolic syndrome. There is a growing awareness that extrahepatic complications occur in individuals with NAFLD, especially an increased risk of cardiovascular disease. Development of diabetes mellitus, chronic kidney disease, colorectal cancer, and endocrinopathies has been linked to NAFLD. This article reviews the extrahepatic complications affecting individuals with NAFLD and the pathogenesis underlying their development.

Role of MicroRNAs in NAFLD/NASH

MicroRNAs (miRNAs) are highly conserved, small, 18-25 nucleotide, non-coding RNAs that regulate gene expression at the post-transcriptional level. Each miRNA can regulate hundreds of target genes, and vice versa each target gene can be regulated by numerous miRNAs, suggesting a very complex network and explaining how miRNAs play pivotal roles in fine-tuning essentially all biological processes in all cell types in the liver. Here, we summarize the current knowledge on the role of miRNAs in the pathogenesis and diagnosis of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) with an outlook to the broader aspects of metabolic syndrome. Furthermore, we discuss the role of miRNAs as potential biomarkers and therapeutic targets in NAFLD/NASH.

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.

The impact of obstructive sleep apnea on nonalcoholic fatty liver disease in patients with severe obesity

OBJECTIVE

Obstructive sleep apnea (OSA) is common among candidates for bariatric surgery. OSA and its associated intermittent hypoxia have been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis. A large cohort of bariatric surgery patients was studied in an effort to explore the relationship between OSA severity, hypoxia, metabolic syndrome, and the severity of NAFLD.

METHODS

Bariatric surgery candidates who underwent both polysomnography and liver biopsy were studied. The severity of OSA as determined by the apnea-hypopnea index (AHI) and parameters of hypoxia was studied in relation to extent of abnormalities of liver histology as measured by the presence of hepatic steatosis, inflammation, and fibrosis.

RESULTS

The study cohort included 362 patients with a mean age of 46.2 years and BMI of 49.9 kg/m(2) . On the basis of AHI, 26% of the cohort had no OSA, 32% mild OSA, 22% moderate OSA, and 20% severe OSA. For the study subjects without metabolic syndrome, positive correlations were found between OSA severity, as measured by AHI, and parameters of hypoxia, with the severity of NAFLD.

CONCLUSIONS

OSA severity and its accompanying hypoxia are associated with the severity of NAFLD.

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.

Obstructive Sleep Apnea Is Associated with Liver Damage and Atherosclerosis in Patients with Non-Alcoholic Fatty Liver Disease

Background/Aims

We assessed whether obstructive sleep apnea (OSA) and nocturnal hypoxemia are associated with severity of liver fibrosis and carotid atherosclerosis in patients with biopsy-proven NAFLD and low prevalence of morbid obesity. Secondary aim was to explore the association of OSA and hypoxemia with NASH and severity of liver pathological changes.

Methods

Consecutive patients (n = 126) with chronically elevated ALT and NAFLD underwent STOP-BANG questionnaire to estimate OSA risk and ultrasonographic carotid assessment. In patients accepting to perform cardiorespiratory polygraphy (PG, n = 50), OSA was defined as an apnea/hypopnea index ≥5. A carotid atherosclerotic plaque was defined as a focal thickening >1.3 mm.

Results

Prevalence of high OSA risk was similar in patients refusing or accepting PG (76% vs 68%, p = 0.17). Among those accepting PG, overall OSA prevalence was significantly higher in patients with F2-F4 fibrosis compared to those without (72% vs 44%; p = 0.04). Significant fibrosis was independently associated with mean nocturnal oxygen saturation (SaO₂)<95% (OR 3.21, 95%C.I. 1.02–7.34; p = 0.04). Prevalence of OSA tended to be higher in patients with, than in those without, carotid plaques (64% vs 40%; p = 0.08). Carotid plaques were independently associated with %time at SaO2<90% >1 (OR 6.30, 95%C.I. 1.02–12.3; p = 0.01).

Conclusions

In NAFLD patients with chronically elevated ALT at low prevalence of morbid obesity, OSA was highly prevalent and indexes of SaO₂ resulted independently associated with severity of liver fibrosis and carotid atherosclerosis. These data suggest to consider sleep disordered breathing as a potential additional therapeutic target in severe NAFLD patients.