Consequences of subchronic and chronic exposure to intermittent hypoxia and sleep deprivation on cardiovascular risk factors in rats

Since studies suggest that both hypoxia and sleep fragmentation are related to cardiovascular alterations induced by obstructive sleep apnea, the present study was designed to evaluate the effects of hypoxia, sleep deprivation, and their combination on biochemical blood parameters in rats. In subchrome experiments (4 days), rats were exposed to intermittent hypoxia (IH) during the light period (2 min room air-2 min 10% O-2 for 12 h/day) and/or paradoxical sleep deprivation (PSD, 24 h/day). Consequences of chronic intermittent hypoxia (CIH) exposure were examined after 21 consecutive days of hypoxia protocol from 10:00 to 16:00 followed by a sleep restriction (SR) period of 18 h (16:00-10:00). Rats were randomly assigned to seven treatment groups: (1) control (2) IH (3) PSD (4) IH-PSD (5) SR (6) CIH and (7) CIH-SR. PSD reduced triglycerides and very low-density lipoprotein (VLDL) cholesterol concentrations and increased total cholesterol and high-density lipoprotein (HDL) cholesterol. IH did not alter any of these parameters. The combination of IH-PSD did not modify the values of total cholesterol and HDL compared to control group. In the chronic experiment, the animals exposed to CIH displayed a reduction of Vitamin B-6 and an increase of triglycerides and VLDL. Our findings show a duration-dependent effect of hypoxia on triglycerides. Rats in the SR and CIH-SR groups showed a diminished concentration of triglycerides and VLDL. SR rats showed a reduction in the concentration of homocysteine but the animals in the CIH-SR treatment condition did not display any alterations in this parameter. In this latter group, an augmentation of cysteine concentration was observed. These results suggest that sleep deprivation and hypoxia modify biochemical blood parameters in distinct ways. (C) 2006 Elsevier B.V. All rights reserved.