HIF1A and obstructive sleep apnea syndrome: There are two main putative mechanisms by which OSA increases LFA, one of which is the activation of triglyceride biosynthesis in liver through a pathway from hypoxia-inducible factor-1α (HIF-1α) [13, 14, 39], and the other is the increase in serum free fatty acid values observed in OSA patients [40, 41].