Normalization of Oxygen Levels Induces a Metabolic Reprogramming in Livers Exposed to Intermittent Hypoxia Mimicking Obstructive Sleep Apnea.

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), is strongly associated with metabolic syndrome and metabolic dysfunction-associated steatotic liver disease (MASLD). IH exacerbates MASLD progression through oxidative stress, inflammation, and lipid accumulation. This study aims to investigate the impact of oxygen normalization on metabolic dysfunction in OSA patients using continuous positive airway pressure (CPAP) therapy, and in mice exposed to IH followed by a reoxygenation period. In the clinical study, 76 participants (44 OSA patients and 32 controls) were analyzed. OSA patients had higher insulin resistance, triglycerides, very low density lipoprotein (VLDL) content, and liver enzyme levels, along with a higher prevalence of liver steatosis. After 18 months of CPAP therapy, OSA patients showed significant improvements in insulin resistance, lipid profiles (total cholesterol and VLDL), liver function markers (AST and albumin), and steatosis risk scores (Fatty Liver Index and OWLiver test). In the experimental study, IH induced hepatic lipid accumulation, oxidative stress, and inflammation, and reoxygenation reversed these deleterious effects in mice. At the molecular level, IH downregulated fatty acid oxidation (FAO)-related genes, thus impairing the FAO process. Reoxygenation maintained elevated levels of lipogenic genes but restored FAO gene expression and activity, suggesting enhanced lipid clearance despite ongoing lipogenesis. Indeed, serum β hydroxybutyrate, a key marker of hepatic FAO in patients, was impaired in OSA patients but normalized after CPAP therapy, supporting improved FAO function. CPAP therapy improves lipid profiles, liver function, and MASLD progression in OSA patients. Experimental findings highlight the therapeutic potential of oxygen normalization in reversing IH-induced liver damage by FAO pathway restoration, indicating a metabolic reprogramming in the liver.