SUSCEPTIBILITY OF LDL TO OXIDATIVE STRESS IN OBSTRUCTIVE SLEEP-APNEA

Cardiovascular diseases are more common in patients with obstructive s leep apnea (OSA) than in the general population. We hypothesized that, severe hypoxemia during sleep in these patients may cause an imbalanc e between reactive oxygen species and the antioxidant reserve that is important for the detoxification of these molecules. We tested the hyp othesis that low-density lipoproteins (LDL) in hypoxic OSA patients ma y be more susceptible to oxidative stress than LDL of nonhypoxic OSA p atients and normal controls. Fifteen OSA patients were included in thi s study, six with severe hypoxia (hypoxic group) who spent more than 1 0 minutes during sleep with SaO(2) <85% (mean 96 minutes), and nine OS A patients (nonhypoxic group) who spent less than 10 minutes during sl eep with SaO(2) <85% (mean 1.1 minutes). Six healthy nonsmoking males of the same age group were included as a control group. The susceptibi lity of each individual's LDL to oxidative stress was examined after f ree-radical challenge in vitro by assessing changes in levels of conju gated dienes. The LDL in OSA patients with severe hypoxia was not more susceptible to oxidative stress compared to the LDL of nonhypoxic OSA patients and normal controls. After 6 hours of exposure to an oxidati ve agent, the changes in the mean conjugated diene were not different among the three groups (p = 0.75). The time required to reach 50% of m aximal absorbance was also not different, p = 0.199. Glutathione perox idase and catalase activities in red blood cells in the hypoxic and no nhypoxic patient groups were not significantly different. One night of CPAP therapy in each patient group did not significantly change the l evel of the antioxidant enzymes. Our results did not show any differen ce in the susceptibility to oxidative stress between hypoxic and nonhy poxic OSA patients and normal controls.