Intermittent hypoxia, energy expenditure, and visceral adipocyte recovery

Background and objective: Body weight of patients with obstructive sleep apnea after initiation of nasal continuous positive airway pressure appears to increase. We hypothesized that intermittent hypoxia (IH) will decrease energy expenditure (EE), and that normoxic recovery will lead to body weight gains. Methods: C57BL/6 J male mice were exposed to either 12 h/day of mild IH (alternating F_IO₂-10-11% and 21%; 640 s cycle), or severe IH (F_IO₂-6-7%-21%; 180 s cycle) or sham IH daily for 4 or 8 weeks. After exposures, EE was evaluated while mice were kept under normoxia for 5 weeks and organ histology was evaluated. Results: EE was not decreased by IH. However, visceral white adipocyte size after normoxic recovery was significantly increased in severe IH in an intensity-dependent manner. Conclusion: Our hypothesis that IH would decrease EE was not corroborated. However, IH and normoxic recovery seem to promote severity-dependent enlargement of visceral adipocytes, likely reflecting altered energy preservation mechanisms induced by IH.