Obstructive sleep apnoea and cardiovascular consequences: Pathophysiological mechanisms

Obstructive sleep apnoea syndrome is a growing health concern, affecting nearly one billion people worldwide; it is an independent cardiovascular risk factor, associated with incident obesity, insulin resistance, hypertension, arrhythmias, stroke, coronary artery disease and heart failure. Obstructive sleep apnoea-related cardiovascular and metabolic co-morbidities are a major concern for prognosis and the complexity of obstructive sleep apnoea integrated care. Continuous positive airway pressure, the first-line therapy for the treatment of obstructive sleep apnoea, is highly effective at improving symptoms and quality of life, but has limited effect on co-morbidities. Deciphering the molecular pathways involved in obstructive sleep apnoea metabolic and cardiovascular consequences is a priority to make new pharmacological targets available, in combination with or as an alternative to continuous positive airway pressure. Intermittent hypoxia, a landmark feature of obstructive sleep apnoea, is the key intermediary mechanism underlying metabolic and cardiovascular complications. Experimental settings allowing intermittent hypoxia exposure in cells, rodents and healthy humans have been established to dissect the molecular mechanisms of obstructive sleep apnoea-related co-morbidities. The main objective of this review is to recapitulate the molecular pathways, cells and tissue interactions contributing to the cardiometabolic consequences of intermittent hypoxia. Sympathetic activation, low-grade inflammation, oxidative stress and endoplasmic reticulum stress are triggered by intermittent hypoxia and play a role in cardiometabolic dysfunction. The key role of hypoxia-inducible factor-1 transcription factor will be detailed, as well as the underestimated and less described importance of mitochondrial functional changes in the intermittent hypoxia setting.