Obstructive sleep apnea and hypoxemia are associated with advanced liver histology in pediatric nonalcoholic fatty liver disease

An international multidisciplinary consensus on pediatric metabolic dysfunction-associated fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent in children and adolescents, particularly those with obesity. NAFLD is considered a hepatic manifestation of the metabolic syndrome due to its close associations with abdominal obesity, insulin resistance, and atherogenic dyslipidemia. Experts have proposed an alternative terminology, metabolic dysfunction-associated fatty liver disease (MAFLD), to better reflect its pathophysiology. This study aimed to develop consensus statements and recommendations for pediatric MAFLD through collaboration among international experts.

METHODS

A group of 65 experts from 35 countries and six continents, including pediatricians, hepatologists, and endocrinologists, participated in a consensus development process. The process encompassed various aspects of pediatric MAFLD, including epidemiology, mechanisms, screening, and management.

FINDINGS

In round 1, we received 65 surveys from 35 countries and analyzed these results, which informed us that 73.3% of respondents agreed with 20 draft statements while 23.8% agreed somewhat. The mean percentage of agreement or somewhat agreement increased to 80.85% and 15.75%, respectively, in round 2. The final statements covered a wide range of topics related to epidemiology, pathophysiology, and strategies for screening and managing pediatric MAFLD.

CONCLUSIONS

The consensus statements and recommendations developed by an international expert panel serve to optimize clinical outcomes and improve the quality of life for children and adolescents with MAFLD. These findings emphasize the need for standardized approaches in diagnosing and treating pediatric MAFLD.

FUNDING

This work was funded by the National Natural Science Foundation of China (82070588, 82370577), the National Key R&D Program of China (2023YFA1800801), National High Level Hospital Clinical Research Funding (2022-PUMCH-C-014), the Wuxi Taihu Talent Plan (DJTD202106), and the Medical Key Discipline Program of Wuxi Health Commission (ZDXK2021007).

Review of paediatric obesity and non-alcoholic fatty liver disease-A focus on emerging non-pharmacologic treatment strategies

Obesity in paediatrics has become one of the most serious public health concerns worldwide. Paediatric obesity leads to increased adult obesity and is associated with several comorbidities, both physical and psychological. Within gastroenterology, non-alcoholic fatty liver disease (NAFLD) is now the most common cause of paediatric liver disease and the most common cause of liver transplantation in young adults. Treatment for NAFLD largely focuses on treatment of obesity with weight loss strategies. Unfortunately, the traditional method of weight loss using multicomponent lifestyle modification (dietary changes, increased exercise and behavioural modification) has often led to disappointing results. In adult patients with obesity, treatment strategies have evolved to include bariatric surgery and, more recently, bariatric endoscopy. In paediatrics, the obesity and NAFLD epidemics will likely require this variety of treatment to address children in a personalized manner. Here, we present a review of paediatric obesity, paediatric NAFLD and the various treatment strategies to date. We focus on non-pharmacologic and emerging therapies, including bariatric surgery and bariatric endoscopy-based treatments. With such a large population of children and adolescents with obesity, further development of these treatments, including paediatric-focused clinical trials, is essential for these emerging modalities.

Macronutrient and Micronutrient Intake in Adolescents With Non-alcoholic Fatty Liver Disease: The Association With Disease Severity

OBJECTIVES

While dietary changes are recommended to treat pediatric non-alcoholic fatty liver disease (NAFLD), the role of specific nutrients in disease progression is unclear. The objective of this study is to (1) assess the macronutrient and micronutrient intake in adolescents with liver biopsy proven NAFLD [with and without non-alcoholic steatohepatitis (NASH)] and lean controls; (2) determine nutritional predictors of disease severity amongst these groups.

METHODS

Adolescents with biopsy-proven NAFLD and lean controls completed the Harvard Food Frequency Questionnaire.

RESULTS

Twenty-eight NAFLD and 15 lean controls were studied. NAFLD with (n = 20) and without NASH (n = 8) had similar total calorie, protein, fat, and carbohydrate intake. Subjects with NASH had higher total sugar (122.3 ± 48.3 vs 83.1 ± 38.8 g), glucose (24.3 ± 9.3 vs 15.2 ± 7.5 g), sucrose (42.3 ± 16.9 vs 28.8 ± 11.7 g), and fructose (29.4 ± 12.5 vs 18.1 ± 8.0 g) intake than those with NAFLD but without NASH ( P < 0.05). Both NAFLD groups had similar micronutrient intake. Alanine aminotransferase (ALT) correlated with total caloric intake ( ρ = 0.4; P = 0.04). Total carbohydrate calories correlated with a higher NAS summary score ( ρ = 0.38; P = 0.04) and lobular inflammation ( ρ = 0.50; P = 0.007). Percent calories from added sugar and glucose correlated with worsening NAS summary score ( ρ = 0.44, P = 0.02; ρ = 0.48, P = 0.009) and lobular inflammation ( ρ = 0.51, P = 0.006; ρ = 0.53, P = 0.004). Percent calories from fructose correlated with lobular inflammation ( ρ = 0.56; P = 0.002). Total daily calories, protein, fat, carbohydrate, and micronutrient intake were similar between NAFLD and lean controls.

CONCLUSIONS

NASH patients consume similar total calories, protein, and fat as those without NASH, but have significantly higher sugar intake. NAFLD and lean children, however, have similar macro/micronutrient intake. Histologic disease severity correlates with total carbohydrate and added sugar intake, supporting a role for simple sugar intake in NAFLD progression.

Nonalcoholic Steatohepatitis in Children

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in children. Although environmental factors are major contributors to early onset, children have both shared and unique genetic risk alleles as compared with adults with NAFLD. Treatment relies on reducing environmental risk factors, but many children have persistent diseases. No medications are approved specifically for the treatment of NAFLD, but some anti-obesity or diabetes treatments may be beneficial. Pediatric NAFLD increases the risk of diabetes and other cardiovascular risk factors. Long-term prospective studies are needed to determine the long-term risk of hepatic and non-hepatic morbidity and mortality in adulthood.

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.

Metabolic Associated Fatty Liver Disease in Children-From Atomistic to Holistic

Non-alcoholic fatty liver disease has become the most common chronic liver disease in children due to the alarmingly increasing incidence of pediatric obesity. It is well-documented that MAFLD prevalence is directly related to an incremental increase in BMI. The multiple hits theory was designed for providing insights regarding the pathogenesis of steatohepatitis and fibrosis in MAFLD. Recent evidence suggested that the microbiome is a crucial contributor in the pathogenesis of MAFLD. Aside from obesity, the most common risk factors for pediatric MAFLD include male gender, low-birth weight, family history of obesity, MAFLD, insulin resistance, type 2 diabetes mellitus, obstructive sleep apnea, and polycystic ovarium syndrome. Usually, pediatric patients with MAFLD have nonspecific symptoms consisting of fatigue, malaise, or diffuse abdominal pain. A wide spectrum of biomarkers was proposed for the diagnosis of MAFLD and NASH, as well as for quantifying the degree of fibrosis, but liver biopsy remains the key diagnostic and staging tool. Nevertheless, elastography-based methods present promising results in this age group as potential non-invasive replacers for liver biopsy. Despite the lack of current guidelines regarding MAFLD treatment in children, lifestyle intervention was proven to be crucial in the management of these patients.

Recent advances in the epidemiology of nonalcoholic fatty liver disease in children

Children with obesity are at risk for numerous health problems, including nonalcoholic fatty liver disease (NAFLD). This review focuses on progress made in the epidemiology of NAFLD in children for the years 2015-2020. The estimated prevalence of NAFLD in children with obesity is 26%. The incidence of NAFLD in children has risen rapidly over the past decade. An understanding of the reasons for this rise is incomplete, but over the past 5 years, many studies have provided additional insight into the complexity of risk factors, diagnostic approaches, and associated comorbidities. Risk factors for NAFLD are wide-ranging, including perinatal factors involving both the mother and newborn, as well as environmental toxin exposure. Progress made in the noninvasive assessment will be critical to improving issues related to variability in approach to screening and diagnosis of NAFLD in children. The list of serious comorbidities observed in children with NAFLD continues to grow. Notably, for many of these conditions, such as diabetes and depression, the rates observed have exceeded the rates reported in children with obesity without NAFLD. Recent advancements reviewed show an increased awareness of this problem, while also calling attention to the need for additional research to guide successful efforts at prevention and treatment.

The association of obstructive sleep apnea with dyslipidemia in Korean children and adolescents: a single-center, cross-sectional study

STUDY OBJECTIVES

To evaluate whether obstructive sleep apnea (OSA) and its severity are related to dyslipidemia and alanine transaminase elevation as a marker of nonalcoholic fatty liver disease in children.

METHODS

The data collected from polysomnography, laboratory measurements (lipid profile and liver enzyme), and body mass index in children aged 0-18 years who visited the pediatric department between 2012 and 2018 were retrospectively analyzed.

RESULTS

There were a total of 273 participants in the study (ages 0-6 years, 7-12 years, and 13-18 years: 61.9%, 26.4%, and 11.7%, respectively). In the ages 7-12 and 13-18 years groups, obesity was strongly associated with OSA severity (Cramer's V = 0.498, P < .001). High-density lipoprotein cholesterol levels were significantly lower in the OSA group than in the non-OSA group, irrespective of the presence of obesity. In addition, high-density lipoprotein cholesterol levels were significantly different between the OSA severity groups after adjusting for body mass index (P = .000). In participants who were obese, moderate and severe OSA were associated with alanine transaminase elevation (P = .023 and P = .045, respectively).

CONCLUSIONS

This study suggests that OSA may be an independent risk factor for dyslipidemia and that OSA and obesity have a synergistic effect on alanine transaminase elevation. Early diagnosis and treatment of OSA from childhood, especially in obese children, will reduce metabolic complications.

CITATION

Kang EK, Jang MJ, Kim KD, Ahn YM. The association of obstructive sleep apnea with dyslipidemia in Korean children and adolescents: a single-center, cross-sectional study. J Clin Sleep Med. 2021;17(8):1599-1605.

Untargeted Metabolomic Profiling of Liver in a Chronic Intermittent Hypoxia Mouse Model

Obstructive sleep apnea (OSA) has been demonstrated to be associated with liver injury. Nevertheless, the mechanisms linking the two disorders remain largely unexplored to date. Based on UHPLC/Q-TOF MS platform, the present study aimed to study the hepatic metabolomic profiling in a chronic intermittent hypoxia (CIH) mouse model to identify altered metabolites and related metabolic pathways. C57BL/6 Mice (n = 12 each group) were exposed to intermittent hypoxia or control conditions (room air) for 12 weeks. At the end of the exposure, liver enzymes and histological changes were assessed. Untargeted metabolomics approach by UHPLC/Q-TOF MS and orthogonal partial least squares-discriminant analysis (OPLS-DA) were applied to screen altered metabolites in mice liver. Bioinformatics analyses were applied to identify the related metabolic pathways. CIH treatment caused a remarkable liver injury in mice. A total of 27 differential metabolites in negative ion mode and 44 in positive ion mode were identified between the two groups. These metabolites were correlated to multiple biological and metabolic processes, including various amino acid metabolism, membrane transport, lipid metabolism, carbohydrate metabolism, nucleotide metabolism, ferroptosis, etc. three differential metabolites including glutathione, glutathione disulfide, arachidonic acid (peroxide free) were identified in the ferroptosis pathway. CIH was associated with a significant metabolic profiling change in mice liver. The metabolites in amino acid metabolism, membrane transport, lipid metabolism, carbohydrate metabolism, nucleotide metabolism, and ferroptosis played an important role in CIH-induced liver injury. These findings contribute to a better understanding of the mechanisms linking OSA and liver injury and help identify potential therapeutic targets.

Alternative Etiologies of Liver Disease in Children With Suspected NAFLD

OBJECTIVES

To determine the prevalence of alternative causes of liver disease in a cohort of youth with overweight and obesity undergoing evaluation for suspected nonalcoholic fatty liver disease (NAFLD).

METHODS

Multicenter, retrospective cohort study of patients aged ≤18 years with overweight and obesity and evidence of elevated serum aminotransferases and/or hepatic steatosis on imaging, referred for suspected NAFLD to Cincinnati Children's Hospital Medical Center (2009-2017) or Yale New Haven Children's Hospital (2012-2017). Testing was performed to exclude the following: autoimmune hepatitis (AIH), Wilson disease, viral hepatitis (B and C), thyroid dysfunction, celiac disease, α-1 antitrypsin deficiency, and hemochromatosis.

RESULTS

A total of 900 children with overweight and obesity (63% boys, 26% Hispanic ethnicity) were referred, with a median age of 13 years (range: 2-18). Most had severe obesity (n = 666; 76%) with a median BMI z score of 2.45 (interquartile range [IQR]: 2.2-2.7). Median alanine aminotransferase level at presentation was 64 U/L (IQR: 42-95). A clinically indicated liver biopsy was performed in 358 children (40%) at a median of 6 months (IQR: 1-14) post initial visit; of those, 46% had confirmed nonalcoholic steatohepatitis. Positive autoantibodies were observed in 13% of the cohort, but none met criteria for AIH. Only 19 (2%) were found to have other causes of liver disease, with no cases of viral hepatitis or Wilson disease detected.

CONCLUSIONS

In a large, multicenter cohort, the vast majority of children with overweight and obesity with presumed or confirmed NAFLD tested negative for other causes of liver disease. In contrast to a previous pediatric report, no patient was diagnosed with AIH.

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.

Advances in the Epidemiology, Diagnosis, and Management of Pediatric Fatty Liver Disease

PURPOSE

Nonalcoholic fatty liver (NAFL) is a major contributor to pediatric liver disease. This review evaluated the current literature on prevalence, screening, diagnosis, and management of NAFL in children and explored recent advances in the field of pediatric NAFL.

METHODS

A PubMed search was performed for manuscripts describing disease burden, diagnosis, and management strategies in pediatric NAFL published within the past 15 years. Systematic reviews, clinical practice guidelines, randomized controlled trials, and cohort and case-control studies were reviewed for the purpose of this article.

FINDINGS

The prevalence of NAFL in children is increasing. It is a leading cause of liver-related morbidity and mortality in children. Screening and diagnosis of NAFL in children are a challenge. Lifestyle changes and exercise are the cornerstones of the management of NAFL.

IMPLICATIONS

Further research is needed to develop better screening and diagnostic tools for pediatric NAFL, including noninvasive diagnostics. NAFL therapeutics is another area of much-needed, ongoing research.

Can Baseline Characteristics be Used to Predict Liver Disease Outcomes in Pediatric Nonalcoholic Fatty Liver Disease?

OBJECTIVE

Longitudinal studies on childhood predictors of nonalcoholic fatty liver disease (NAFLD) progression are lacking. The objective of this study was to determine whether baseline clinical or laboratory measures predict liver disease outcomes in a pediatric NAFLD cohort.

METHODS

A retrospective study of patients with presumed NAFLD was conducted using baseline and follow-up clinical and laboratory measures. Disease outcomes were defined using the mean serum alanine aminotransferase (ALT) levels from 24 to 36 months after the first visit. Logistic regression assessed the relationship between ALT progression/regression and predictor variables. Multivariable regression determined the best model for predicting the ALT outcome. Markov process modeling explored the likelihood for a patient to transition between ALT states.

RESULTS

Of a total of 816 patients identified, 144 had sufficient data. Regression was seen in 26%, whereas 30% progressed. No baseline clinical or laboratory measurements had a significant effect on disease outcomes. Markov modeling demonstrated that subjects were more likely to either remain in their baseline ALT group or worsen rather than improve.

CONCLUSIONS

Routinely obtained baseline clinical or laboratory measures cannot help risk-stratify youth with presumed NAFLD in terms of long-term outcomes. Close clinical, radiographic, and histologic evaluation of patients is warranted to determine those at risk of progression.

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.

Perspectives on youth-onset nonalcoholic fatty liver disease

BACKGROUND

The prevalence and incidence of youth-onset nonalcoholic fatty liver disease (NAFLD) far exceeds other paediatric chronic liver diseases and represents a considerable public health issue globally.

METHODS

Here, we performed a narrative review of current knowledge regarding the epidemiology of paediatric NAFLD, selected concepts in pathogenesis, comorbidities, diagnosis, and management, and issues related to the transition to adulthood.

RESULTS

Paediatric NAFLD has become increasingly more prevalent, especially in certain subgroups, such as children with obesity and certain races/ethnicities. The pathophysiology of paediatric NAFLD is complex and multifactorial, driven by an interaction of environmental and genetic factors. Once developed, NAFLD in childhood is associated with type 2 diabetes, hypertension, increased cardiovascular disease risk, and end-stage liver disease. This predicts an increased burden of morbidity and mortality in adolescents and young adults. Early screening and diagnosis are therefore crucial, and the development of noninvasive biomarkers remains an active area of investigation. Currently, treatment strategies are focused on lifestyle changes, but there is also research interest in pharmacological and surgical options. In the transition from paediatric to adult care, there are several potential challenges/barriers to treatment and research is needed to understand how best to support patients during this time.

CONCLUSIONS

Our understanding of the epidemiology and pathophysiology of paediatric NAFLD has increased considerably over recent decades, but several critical knowledge gaps remain and must be addressed in order to better mitigate the short-term and long-term risks of youth-onset NAFLD.

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.

Recent advances in understanding and managing pediatric nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of disease that can range from isolated macrovesicular hepatocellular steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis to cirrhosis. The prevalence of NAFLD has increased over several decades, mirroring the global obesity pandemic. NAFLD currently represents the most common etiology of chronic liver disease in children and adolescents worldwide. Disease presentation in childhood strongly suggests that these children may have unique susceptibilities and more severe long-term consequences. Emerging data demonstrate that the pathogenesis of early-onset NAFLD is secondary to a complex interplay involving genetic, metabolic, environmental, and microbiological factors. Such influences may begin in utero. Dietary and lifestyle modifications remain the primary effective therapeutic interventions, although long-term efficacy is limited by poor adoption or adherence. Advances in the development and validation of non-invasive biomarkers and imaging modalities will facilitate diagnosis for affected children and adolescents and facilitate long-term natural history studies and the development of therapeutic interventions.

Nonalcoholic Fatty Liver Disease in Children: Unique Considerations and Challenges

Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence in concert with the global epidemic of obesity and is being diagnosed at increasingly younger ages. The unique histologic features and early presentation of disease in pediatrics suggest that children and adults may differ with regard to etiopathogenesis, with children displaying a greater vulnerability to genetic and environmental factors. Of significant relevance to pediatrics, in utero and perinatal stressors may alter the lifelong health trajectory of a child, increasing the risk of NAFLD and other cardiometabolic diseases. The development and progression of disease in childhood is likely to carry increased risk of long-term morbidity. Novel biomarkers and therapeutic agents are needed to avoid the otherwise inevitable health and societal consequences of this rapidly expanding pediatric population.

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.

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.

Evaluation of Quantitative Imaging Biomarkers for Early-phase Clinical Trials of Steatohepatitis in Adolescents

OBJECTIVES

Early-phase pediatric nonalcoholic fatty liver disease (NAFLD) clinical trials are designed with noninvasive parameters to assess potential efficacy. Increasingly, these parameters include magnetic resonance imaging (MRI)-derived proton density fat fraction (PDFF) and MR elastography (MRE)-derived shear stiffness as biomarkers of hepatic steatosis and fibrosis, respectively. Understanding fluctuations in these measures is essential for calculating trial sample sizes, interpreting results, and planning clinical drug trials in children with NAFLD. Lack of such data in children constitutes a critical knowledge gap. Therefore, the primary aim of this study was to assess whole-liver MRI-PDFF change in adolescents with nonalcoholic steatohepatitis (NASH) over 12 weeks.

METHODS

Adolescents 12 to 19 years with biopsy-proven NASH undergoing standard-of-care treatment were enrolled. Baseline and week-12 assessments of anthropometrics, transaminases, MRI-PDFF, and MRE stiffness were obtained.

RESULTS

Fifteen adolescents were included (mean age 15.7 [SD 2.9] years). Hepatic MRI-PDFF was stable over 12 weeks (mean absolute change -0.8%, P = 0.24). Correlation between baseline and week-12 values of MRI-PDFF was high (ICC = 0.97, 95% CI 0.90-0.99). MRE stiffness was stable (mean percentage change 2.7%, P = 0.44); correlation between baseline and week-12 values was moderate (ICC = 0.47; 95% CI 0-0.79). Changes in weight, BMI, and aminotransferases were not statistically significant.

CONCLUSION

In adolescents with NASH, fluctuations in hepatic MRI-PDFF and MRE stiffness over 12 weeks of standard-of-care were small. These data on the natural fluctuations in quantitative imaging biomarkers can serve as a reference for interventional trials in pediatric NASH and inform the interpretation and planning of clinical trials.

A Systematic Review of NAFLD-Associated Extrahepatic Disorders in Youths

Background: There is growing evidence that non-alcoholic fatty liver disease (NAFLD) is a disease affecting not only the liver but also extrahepatic organs. Aim: To investigate whether in youths NAFLD is associated with extrahepatic complications such as subclinical atherosclerosis, cardiac abnormalities, hypertension, type 2 diabetes, decreased bone mineral density, renal dysfunction, obstructive sleep apnea, and polycystic ovary syndrome. Methods: We systematically reviewed PubMed; Scopus; Embase; and the Cochrane Library databases up to 28 February 2019 and assessed the quality of studies using the Newcastle-Ottawa Scale. Results: Thirty-five articles were selected for this systematic review: fifteen (4627 participants) evaluated the association of NAFLD with subclinical atherosclerosis; four (969 participants) with cardiac abnormalities; two (550 participants) with hypertension; four (1328 participants) with diabetes; six (523 participants) with low bone mineral density; two (865 participants) with renal dysfunction; one with obstructive sleep apnea; and one with polycystic ovary syndrome. Most studies found that youths with NAFLD have increased features of subclinical atherosclerosis; as well as of cardiac alterations. Limited data were available to endorse a solid estimate of the prevalence of diabetes; low mineral density and renal dysfunction in the pediatric NAFLD population. Conclusion: NAFLD-related intermediate CVD outcomes can occur and be detected early in young populations.

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.

Nocturnal Hypoxia Activation of the Hedgehog Signaling Pathway Affects Pediatric Nonalcoholic Fatty Liver Disease Severity

Chronic intermittent hypoxia and hedgehog (Hh) pathway dysregulation are associated with nonalcoholic fatty liver disease (NAFLD) progression. In this study, we determined the relationship between obstructive sleep apnea (OSA)/nocturnal hypoxia and Hh signaling in pediatric NAFLD. Adolescents with histologic NAFLD (n = 31) underwent polysomnogram testing, laboratory testing, and Sonic Hh (SHh), Indian hedgehog (IHh), glioblastoma‐associated oncogene 2 (Gli2), keratin 7 (K7), α‐smooth muscle actin (α‐SMA), and hypoxia‐inducible factor 1α (HIF‐1α) immunohistochemistry. Aspartate aminotransferase (AST) correlated with SHh, r = 0.64; Gli2, r = 0.4; α‐SMA, r = 0.55; and K7, r = 0.45 (P < 0.01), as did alanine aminotransferase (ALT) (SHh, r = 0.51; Gli2, r = 0.43; α‐SMA, r = 0.51; P < 0.02). SHh correlated with NAFLD activity score (r = 0.39), whereas IHh correlated with inflammation (r = −0.478) and histologic grade (r = −0.43); P < 0.03. Subjects with OSA/hypoxia had higher SHh (4.0 ± 2.9 versus 2.0 ± 1.5), Gli2 (74.2 ± 28.0 versus 55.8 ± 11.8), and α‐SMA (6.2 ± 3.3 versus 4.3 ± 1.2); compared to those without (P < 0.03). OSA severity correlated with SHh (r = 0.31; P = 0.09) and Gli2 (r = 0.37; P = 0.04) as did hypoxia severity, which was associated with increasing SHh (r = −0.53), Gli2 (r = −0.52), α‐SMA (r = −0.61), and K7 (r = −0.42); P < 0.02. Prolonged O₂ desaturations <90% also correlated with SHh (r = 0.55) and Gli2 (r = 0.61); P < 0.05. Conclusion: The Hh pathway is activated in pediatric patients with NAFLD with nocturnal hypoxia and relates to disease severity. Tissue hypoxia may allow for functional activation of HIF‐1α, with induction of genes important in epithelial‐mesenchymal transition, including SHh, and NAFLD progression.

Nonalcoholic Liver Disease in Children and Adolescents

Pediatric nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease in children. The spectrum of NAFLD ranges from steatosis to nonalcoholic steatohepatitis (NASH) to fibrosis. Obesity rates in children continue to rise and, as a result, NAFLD in children is becoming more prevalent. The pathophysiology, natural history, and progression of disease are still being elucidated but NAFLD/NASH in children may represent a more severe phenotype that will benefit from early identification and management.

Associations of sleep duration and quality with serum and hepatic lipids: The Netherlands Epidemiology of Obesity Study

Short and long sleep duration and poor sleep quality may affect serum and hepatic lipid content, but available evidence is inconsistent. Therefore, we aimed to investigate the associations of sleep duration and quality with serum and hepatic lipid content in a large population‐based cohort of middle‐aged individuals. The present cross‐sectional study was embedded in the Netherlands Epidemiology of Obesity (NEO) study and consisted of 4260 participants (mean age, 55 years; proportion men, 46%) not using lipid‐lowering agents. Self‐reported sleep duration and quality were assessed using the Pittsburgh Sleep Quality Index questionnaire (PSQI). Outcomes of this study were fasting lipid profile (total cholesterol, low‐density lipoprotein [LDL]‐cholesterol, high‐density lipoprotein [HDL]‐cholesterol and triglycerides), postprandial triglyceride (response) levels, and hepatic triglyceride content (HTGC) as measured with magnetic resonance spectroscopy. We performed multivariable linear regression analyses, adjusted for confounders and additionally for measures that link to adiposity (e.g. body mass index [BMI] and sleep apnea). We observed that relative to the group with median sleep duration (≈7.0 hr of sleep), the group with shortest sleep (≈5.0 hr of sleep) had 1.5‐fold higher HTGC (95% confidence interval [CI]: 1.0‐2.2). The group with PSQI score ≥ 10 had a 1.1‐fold (95% CI: 1.0‐1.2) higher serum triglyceride level compared with the group with PSQI ≤ 5. However, these associations disappeared after adjustment for BMI and sleep apnea. Therefore, we concluded that previously observed associations of shorter sleep duration and poorer sleep quality with an adverse lipid profile, may be explained by BMI and sleep apnea, rather than by a direct effect of sleep on the lipid profile.

Nonalcoholic Fatty Liver Disease in Children: Not a Small Matter

The prevalence of nonalcoholic fatty liver disease (NAFLD) has increased substantially in the past two decades and NAFLD has now become the most common cause of chronic liver disease in children and adolescents. NAFLD is a broad clinicopathologic spectrum ranging from simple steatosis to varying degrees of necroinflammation called nonalcoholic steatohepatitis (NASH), leading to fibrosis and subsequently to cirrhosis. Despite the increasing prevalence and progressive nature of NAFLD even among children, therapy for NAFLD in both adults and children are limited. Weight loss remains the only consistently effective therapy for NAFLD. Pharmacologic options are even more limited in children than in adults with NAFLD. Vitamin E has been shown to be effective in improving histology in children with NASH. Few pharmacologic options such as metformin, probiotics, omega-3 fatty acids, and cysteamine bitartrate have been studied in children, with limited beneficial effects. However, these studies are limited by small sample size and heterogeneity of outcome assessment after treatment. Recent studies show promising results with bariatric surgery with regards to weight loss and improvement in liver histology in adolescents with NAFLD. In this review article, we discuss epidemiology, pathophysiology, and extrahepatic comorbidities of pediatric NAFLD and review existing therapeutic options for children with NAFLD. We also review novel therapeutic strategies studied in adults that could potentially be studied in children in the future.

Treating Obstructive Sleep Apnea and Chronic Intermittent Hypoxia Improves the Severity of Nonalcoholic Fatty Liver Disease in Children

OBJECTIVE

To determine the effects of treating obstructive sleep apnea/nocturnal hypoxia on pediatric nonalcoholic fatty liver disease (NAFLD) severity and oxidative stress.

STUDY DESIGN

Biopsy proven participants (n = 9) with NAFLD and obstructive sleep apnea/hypoxia were studied before and after treatment with continuous positive airway pressure (CPAP) for sleep disordered breathing, including laboratory testing and markers of oxidative stress, urine F(2)-isoprostanes.

RESULTS

Adolescents (age 11.5 ± 1.2 years; body mass index, 29.5 ± 3.8 kg/m²) with significant NAFLD (mean histologic necroinflammation grade, 2.3 ± 0.9; fibrosis stage, 1.4 ± 1.3; NAFLD Activity Score summary, 4.8 ± 1.6) had obstructive sleep apnea/hypoxia by polysomnography. At baseline, they had severe obstructive sleep apnea/hypoxia, elevated aminotransferases, the metabolic syndrome, and significant oxidative stress (high F(2)-isoprostanes). Obstructive sleep apnea/hypoxia was treated with home CPAP for a mean 89 ± 62 days. Although body mass index increased, obstructive sleep apnea/hypoxia severity improved on CPAP and was accompanied by reduced alanine aminotransferase, metabolic syndrome markers, and F(2)-isoprostanes.

CONCLUSIONS

This study provides strong evidence that treatment of obstructive sleep apnea/nocturnal hypoxia with CPAP in children with NAFLD may reverse parameters of liver injury and reduce oxidative stress. These data also suggest CPAP as a new therapy to prevent progression of NAFLD in those children with obesity found to have obstructive sleep apnea/nocturnal hypoxia.

Symptoms of Daytime Sleepiness and Sleep Apnea in Liver Cirrhosis Patients

Background/propose. Sleep disturbance and excessive daytime sleepiness (EDS) have been reported in patients with hepatic cirrhosis with no hepatic encephalopathy (HE). The objective of this study was to evaluate daytime sleepiness and risk of obstructive sleep apnea (OSA) among liver cirrhosis patients.

MATERIAL AND METHODS

A cross-sectional study was conducted at King Abdulaziz Medical City (KAMC)-Riyadh over a period of six months, using a structured questionnaire that investigated: 1) Sleep patterns and daytime sleepiness using the Epworth Sleeping Scale (ESS), and 2) The risk for sleep apnea using the Berlin Questionnaire (BQ). We enrolled patients with a confirmed diagnosis of liver cirrhosis who were being followed at the hepatology and pre-liver transplant clinics.

RESULTS

We enrolled 200 patients with liver cirrhosis, 57.5% of whom were male. The mean age was 60 (± SD 12.2). The reported prevalence of EDS, OSA, and both EDS and OSA were 29.5%, 42.9%, and 13.6%, respectively. The prevalence of EDS was higher in patients with Hepatitis-C and patients with DM, who experienced short sleep duration. We did not find any association between the severity of liver disease and EDS or OSA as measured by Child-Pugh scores (CPS).

CONCLUSIONS

The risk of OSA and EDS is high among liver cirrhosis patients. Those patients with cirrhosis secondary to Hepatitis C are at higher risk of EDS and OSA. Both EDS and OSA affect patients designated as CPS Class A more frequently than patients designated as CPS Class B.

Association Between Cytokines and Liver Histology in Children with Nonalcoholic Fatty Liver Disease

Background

Reliable non-invasive markers to characterize inflammation, hepatocellular ballooning, and fibrosis in nonalcoholic fatty liver disease (NAFLD) are lacking. We investigated the relationship between plasma cytokine levels and features of NAFLD histology to gain insight into cellular pathways driving NASH and to identify potential non-invasive discriminators of NAFLD severity and pattern.

Methods

Cytokines were measured from plasma obtained at enrollment in pediatric participants in NASH Clinical Research Network studies with liver biopsy-proven NAFLD. Cytokines were chosen a priori as possible discriminators of NASH and its components. Minimization of Akaike Information Criterion (AIC) was used to determine cytokines retained in multivariable models.

Results

Of 235 subjects, 31% had "Definite NASH" on liver histology, 43% had "Borderline NASH", and 25% had NAFLD but not NASH. Total plasminogen activator inhibitor 1 (PAI1) and activated PAI1 levels were higher in pediatric participants with Definite NASH and with lobular inflammation. Interleukin-8 (IL-8) was higher in those with stage 3-4 fibrosis and lobular inflammation. sIL-2rα was higher in children with stage 3-4 fibrosis and portal inflammation. In multivariable analysis, PAI1 variables were discriminators of Borderline/Definite NASH, definite NASH, lobular inflammation and ballooning. IL-8 increased with steatosis and fibrosis severity; sIL-2rα increased with fibrosis severity and portal inflammation. IL-7 decreased with portal inflammation and fibrosis severity.

Conclusions

Plasma cytokines associated with histology varied considerably among NASH features, suggesting promising avenues for investigation. Future, more targeted analysis is needed to identify the role of these markers in NAFLD and to evaluate their potential as non-invasive discriminators of disease severity.

Nonalcoholic Fatty Liver Disease in Children: Hepatic and Extrahepatic Complications

Nonalcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome and has become the most common form of chronic liver disease in children and adolescents. The histologic spectrum of NAFLD is broad ranging, from the relatively benign form of simple steatosis to the aggressive form of nonalcoholic steatohepatitis, eventually leading to fibrosis and cirrhosis. NAFLD has also been recognized as an independent risk factor for extrahepatic complications, such as cardiovascular disease, type 2 diabetes mellitus, sleep disorders, and osteoporosis. In this review, we discuss both the hepatic and extrahepatic complications of NAFLD in children.

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).

Metabolic Consequences of Obstructive Sleep Apnea in Adolescents with Obesity: A Systematic Literature Review and Meta-Analysis

BACKGROUND

Adolescents who are obese are at high risk of developing obstructive sleep apnea (OSA). Although there is clear evidence associating OSA with metabolic dysfunction in adults, the evidence is less clear cut with adolescents. The purpose of this review was determine the association of sleep apnea with dyslipidemia, insulin resistance, cardiovascular disease risk, nonalcoholic fatty liver disease, and difficulty with weight loss in adolescents.

METHODS

A systematic literature review using PubMed, Scopus, CINAHL, Google Scholar, and PsycINFO was performed and articles were screened and reviewed with an a priori protocol.

RESULTS

Sixteen articles were included in qualitative synthesis and 10 were included in meta-analysis. Results from the meta-analysis indicate that OSA in adolescents is associated with greater risk of dyslipidemia, insulin resistance, and hypertension.

CONCLUSIONS

Although obesity leads to increased metabolic risk, OSA appears to independently increase metabolic impairment. Adolescents with obesity should be frequently screened for OSA to determine need for treatment and reduce this metabolic burden.

Clinical implications of understanding the association between oxidative stress and pediatric NAFLD

Oxidative stress is central to the pathogenesis of non-alcoholic steatohepatitis. The reactive oxygen species (ROS) that characterise oxidative stress are generated in several cellular sites and their production is influence by multi-organ interactions. Areas covered: Mitochondrial dysfunction is the main source of ROS in fatty liver and is closely related to endoplasmic reticulum stress. Both are caused by lipotoxicity and together these three factors form a cycle of progressive organelle damage, resulting in sterile inflammation and apoptosis. Adipose tissue inflammation and intestinal dysbiosis provide substrates for ROS formation and trigger immune activation. Obstructive sleep apnea and abnormal divalent metal metabolism may also play a role. Expert commentary: The majority of available high-quality data originates from studies in adults and there are fewer therapeutic trials performed in pediatric cohorts, therefore conclusions are generalised to children. Establishing the role of organelle interactions, and its relationship with oxidative stress in steatohepatitis, is a rapidly evolving area of research.

NASPGHAN Clinical Practice Guideline for the Diagnosis and Treatment of Nonalcoholic Fatty Liver Disease in Children: Recommendations from the Expert Committee on NAFLD (ECON) and the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN)

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease that occurs in the setting of insulin resistance and increased adiposity. It has rapidly evolved into the most common liver disease seen in the pediatric population and is a management challenge for general pediatric practitioners, subspecialists, and for health systems. In this guideline, the expert committee on NAFLD reviewed and summarized the available literature, formulating recommendations to guide screening and clinical care of children with NAFLD.

Effect of continuous positive airway pressure on liver enzymes in obstructive sleep apnea: A meta-analysis

BACKGROUND

Previous studies have suggested that obstructive sleep apnea (OSA) was associated with nonalcoholic fatty liver disease (NAFLD). However, the impact of OSA treatment using continuous positive airway pressure (CPAP) on liver enzymes remained controversial. This meta-analysis was conducted to determine whether CPAP therapy could reduce liver enzyme levels.

METHODS

Two reviewers independently searched PubMed, Cochrane library, Embase and Web of Science before December 2015. Information on characteristics of subjects, study design and pre- and post-CPAP treatment of serum ALT and AST was extracted for analysis. A total of five studies with seven cohorts that included 192 patients were pooled into meta-analysis.

RESULTS

CPAP was associated with a statistically significant decrease on both ALT and AST levels in OSA patients (WMD = 8.036, 95% CI = 2.788-13.285, z = 3.00, P = .003 and WMD = 4.612, 95% CI = 0.817-8.407, z = 2.38, P = .017, respectively). Subgroup analyses indicated that CPAP therapy was more effective in OSA patients with treatment duration > 3 mo (WMD = 12.374, 95% CI = 2.727-22.020, z = 2.51, P = .012 for ALT and WMD = 7.576, 95% CI = 1.781-13.370, z =2.56, P = .010 for AST).

CONCLUSION

This meta-analysis suggested that CPAP was associated with a statistically significant decrease on liver enzymes in OSA patients. Further large-scale well-designed RCTs with long-term follow-up are required to clarify this issue.

Nocturnal hypoxia-induced oxidative stress promotes progression of pediatric non-alcoholic fatty liver disease

BACKGROUND & AIMS

Oxidative stress is proposed as a central mediator in NAFLD pathogenesis, but the specific trigger for reactive oxygen species generation has not been clearly delineated. In addition, emerging evidence shows that obesity related obstructive sleep apnea (OSA) and nocturnal hypoxia are associated with NAFLD progression in adults. The aim of this study was to determine if OSA/nocturnal hypoxia-induced oxidative stress promotes the progression of pediatric NAFLD.

METHODS

Subjects with biopsy proven NAFLD and lean controls were studied. Subjects underwent polysomnograms, liver histology scoring, laboratory testing, urine F(2)-isoprostanes (measure of lipid peroxidation) and 4-hydroxynonenal liver immunohistochemistry (in situ hepatic lipid peroxidation).

RESULTS

We studied 36 adolescents with NAFLD and 14 lean controls. The OSA/hypoxia group (69% of NAFLD subjects) had more severe fibrosis (64% stage 0-2; 36% stage 3) than those without OSA/hypoxia (100% stage 0-2), p=0.03. Higher F(2)-isoprostanes correlated with apnea/hypoxia index (r=0.39, p=0.03), % time SaO2 <90% (r=0.56, p=0.0008) and inversely with SaO2 nadir (r=-0.46, p=0.008). OSA/hypoxia was most severe in subjects with the greatest 4HNE staining (p=0.03). Increasing F(2)-isoprostanes(r=0.32, p=0.04) and 4HNE hepatic staining (r=0.47, p=0.007) were associated with worsening steatosis. Greater oxidative stress occurred in subjects with definite NASH as measured by F(2)-isoprostanes (p=0.06) and hepatic 4HNE (p=0.03) compared to those with borderline/not NASH.

CONCLUSIONS

These data support the role of nocturnal hypoxia as a trigger for localized hepatic oxidative stress, an important factor associated with the progression of NASH and hepatic fibrosis in obese pediatric patients.

LAY SUMMARY

Obstructive sleep apnea and low nighttime oxygen are associated with NAFLD progression in adults. In this study, we show that adolescents with NAFLD who have OSA and low oxygen have significant scar tissue in their livers. NAFLD subjects affected by OSA and low oxygen have a greater imbalance between the production of free radicals and their body's ability to counteract their harmful effects than subjects without OSA and low oxygen. This study shows that low oxygen levels may be an important trigger in the progression of pediatric NASH.

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.

Similarities and differences between pediatric and adult nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is highly common and potentially serious in children and adolescents. The term NAFLD refers to a spectrum of diseases ranging from accumulation of fat in the liver (simple steatosis or nonalcoholic fatty liver "NAFL") to the potentially progressive form of nonalcoholic steatohepatitis (NASH) characterized by hepatocyte ballooning, inflammation, and often associated with fibrosis. While large prospective longitudinal studies in pediatric NAFLD are still lacking, growing evidence suggests that children with NAFL are at increased risk for cardiometabolic complications, while those with NASH and advance fibrosis are also at risk for significant liver-related morbidity including cirrhosis and its complications. Pediatric NAFLD shares features of adult NAFLD but also shows many different characteristics in terms of prevalence, histology, diagnosis and management. Translational studies suggest that NAFLD is a highly heritable disease in which genetic variations and environment closely interact to determine the disease phenotype and the progression to the more advanced forms of the disease. Changes in lifestyle, targeting gradual weight reduction, and physical exercise continue to be the mainstay of treatment for NAFLD in children. Recent advances in development of noninvasive diagnostic modalities and the potential for identifying effective pharmacological interventions may result in significant progress in the management of NAFLD in the pediatric population.

The Progression and Natural History of Pediatric Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the United States. Childhood NAFLD is associated with hepatic and nonhepatic morbidity and mortality. Nonhepatic associations include cardiovascular, metabolic, pulmonary, and psychological disorders. Cardiovascular conditions observed in childhood include left ventricular dysfunction. Furthermore, childhood obesity is associated with greater odds of having hepatocellular carcinoma as an adult. Evidence suggests that NAFLD may begin in utero in children of diabetic mothers. Thus rigorous efforts for structured diagnosis and follow-up are a priority to better develop the understanding of outcomes in pediatric NAFLD.

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.