Sleep apnea and fatty liver disease: The growing link and management issues

Non-alcoholic fatty liver disease as metabolic consequence of obstructive sleep apnea

Obstructive sleep apnea (OSA) as a worldwide prevalent condition carries risk for cardiovascular and metabolic diseases, ultimately increasing overall mortality rates. Non-alcoholic fatty liver disease (NAFLD) can be considered as the primary metabolic disease, but also as a coexisting OSA comorbidity. Although prevalence of NAFLD covers quarter of world population, it increases with OSA presence. It can be speculated that chronic intermittent hypoxia (CIH) and sympathetic nervous system overactivity are involved in NAFLD pathogenesis and progression from simple steatosis through steatohepatitis to fibrosis. CIH provides the environment for liver oxidative stress, inflammation and increases the expression of genes involved in cholesterol and fatty acids synthesis. Catecholamines increase b-oxidation in liver and release free fatty acids from adipose tissue in plasma which inhibit insulin effects. Obesity and insulin resistance as key players in NAFLD development and advancement, deepen vicious circle of oxidative stress, inflammation and dyslipidemia. If not treated, OSA in NAFLD patients has been associated with inflammation, hepatocytes' necrosis, and fibrosis. Continuous positive airway pressure (CPAP) represents gold standard for OSA therapy, allowing the unimpeded air passage through upper parts of respiratory system. However, it has been demonstrated that CPAP therapy have beneficial effects on cardiometabolic outcomes and slow liver degeneration.

Non-alcoholic fatty liver disease is an independent risk factor for inflammation in obstructive sleep apnea syndrome in obese Asian Indians

INTRODUCTION

Obstructive sleep apnea (OSA) has been estimated to affect 4-11% of the population and causes systemic inflammation which leads to metabolic syndrome (MS). Non-alcoholic fatty liver disease (NAFLD) is also associated with MS whether NAFLD is an additional risk factor for the systemic inflammation that occurs in OSA is unclear.

OBJECTIVE

In this study, we aimed to analyze the association of OSA and NAFLD with MS and systemic inflammation in Asian Indians.

METHODS

Total 240 (132 males and 108 females) overweight/obese subjects [body mass index (BMI > 23 kg/m2)] were recruited; of these, 124 subjects had OSA with NAFLD, 47 had OSA without NAFLD, 44 did not have OSA but had NAFLD and 25 had neither OSA nor without NAFLD. Severity of NAFLD was based on abdomen ultrasound and of OSA on overnight polysomnography. Clinical examinations, anthropometry, body composition, metabolic parameters, and inflammatory biomarkers were recorded.

RESULTS

Serum levels of leptin, macrophage migration inhibitory factor (MIF), interleukin-6 (IL-6), high sensitive C-reactive protein (Hs-CRP), and tumor necrosis factor alpha (TNF-α) were significantly higher, and adiponectin levels were significantly lower in OSA with NAFLD subjects. Prevalence of MS was significantly increased in OSA and NAFLD subjects (p = 0.001). There was a strong association and correlation between leptin, IL-6, Hs-CRP, MIF, and TNF-α in OSA and NAFLD subjects. Multivariate logistic regression showed that OSA was positively associated with the NAFLD [odds ratio (OR), (95% confidence interval (CL) 3.12 (2.58-7.72), (P = 0.002)].

CONCLUSION

NAFLD is an additional risk factor in OSA subject which contributes to systemic inflammation in Asian Indians.