Insulin Resistance, but Not Obstructive Sleep Apnea Is Associated with Hepatic Steatosis in Chinese Patients with Severe Obesity

Introduction: Severe obesity is often present with non-alcoholic fatty liver disease (NAFLD) and obstructive sleep apnea (OSA). Emerging researches suggest OSA plays an important role in NAFLD development and progression while the relationship between OSA and NAFLD is still conflicting. The interaction of OSA and NAFLD should be further evaluated as obesity surges. The purpose of this study was to assess the prevalence of OSA and NAFLD in patients with obesity undergoing bariatric surgery and evaluate the association between OSA and severity of NAFLD. Methods: 141 patients with severe obesity undergoing preoperative polysomnography and intraoperative liver biopsy during bariatric surgery were investigated. Clinical, anthropometric variables, liver enzymes, fasting blood glucose, fasting serum insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) were measured. The severity of NAFLD was assessed by degree of steatosis, ballooning, intralobular inflammation, and NAFLD activity score. The diagnosis and severity assessment of OSA was based on an apnea/hypopnea index (AHI). Results: OSA was diagnosed in 127 (90.07%), NAFLD in 124 (87.94%), and non-alcoholic steatohepatitis in 72 (51.06%) patients. There was a statistical difference in BMI, waist circumstance, neck circumstance, high-density lipoprotein cholesterol, fasting insulin, and HOMA-IR among the three groups divided by the severity of AHI. In addition, the distribution of hepatic steatosis grades among the three groups was statistically different (p = 0.025). AHI was significantly associated with HOMA-IR and hepatic steatosis when assessing the association between OSA parameters and liver histology in NAFLD (p < 0.05). Patients with steatosis of grades 1-3 had significantly elevated aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transferase, triglycerides, fasting insulin, fasting glucose, HOMA-IR, and AHI compared with the patients with steatosis of grade 0. In a multivariable logistic analysis, the positive association between AHI and hepatic steatosis attenuated after adjusting for HOMA-IR. Conclusion: Prevalence of OSA and NAFLD was high in patients with obesity eligible for bariatric procedures. HOMA-IR, but not AHI, was an independent risk factor for hepatic steatosis in this population.