Mitochondrial DNA alteration in obstructive sleep apnea

Rationale: Obstructive Sleep Apnea (OSAS) is a common disease associated with increase of cardiovascular risk and characterized by repeated episodes of Intermitted Hypoxia (IH) which induce oxidative stress and systemic inflammation. Mitochondria are organelles with their own DNA (MtDNA) present into the cells and they are involved in the respiratory chain. Oxidative stress can induce damage to nuclear and mitochondrial DNA. Objectives: The aim of this study was to investigate if the increase of oxidative stress in OSAS patients can induce also MtDNA alteration. Methods: Content of MtDNA and nuclear DNA (nDNA) was measured into blood cells of OSAS patients by Real Time PCR. The ratio between MtDNA/nDNA was then calculated. Presence of oxidative stress was evaluated by levels of Reactive Oxygen Metabolites (ROMs), measured by diacron reactive oxygen metabolite test (d-ROM test). Differences between OSAS patients and control group were then calculated by T-test and correlation between MtDNA/nDNA and ROMs level was evaluated by Pearson analysis. Measurements and Main Results: 81 patients (age 56,32±11,96; BMI 38,25±10,37; AHI 48,93±27,17) were compared with 40 control subjects (age 44,05±12,7; BMI 27,38±5,56, AHI 3,2±1,3). MtDNA/nDNA was higher in patients with OSAS than in control group (155,28±54,84 vs 133,33±48,76; p=0,03), also the levels of ROMs were higher in OSAS subjects (344,72±71,66 vs 226±36,77; p=0,02) and they were positive correlated with MtDNA/nDNA (R=0,53, p<0,01). Conclusions: In OSAS patients there is a Mitochondrial DNA damage induced by increase of oxidative stress. Intermitted hypoxia seems to be the main mechanism which lead to this process.