Mitochondrial DNA alteration in obstructive sleep apnea

Background: Obstructive Sleep Apnea (OSAS) is a disease associated with the increase of cardiovascular risk and it is characterized by repeated episodes of Intermittent Hypoxia (IH) which inducing oxidative stress and systemic inflammation. Mitochondria are cell organelles involved in the respiratory that have their own DNA (MtDNA). The aim of this study was to investigate if the increase of oxidative stress in OSAS patients can induce also MtDNA alterations. Methods: 46 OSAS patients (age 59.27 +/- 11.38; BMI 30.84 +/- 3.64; AHI 36.63 +/- 24.18) were compared with 36 control subjects (age 54.42 +/- 6.63; BMI 29.06 +/- 4.7; AHI 3.8 +/- 1.10). In blood cells Content of MtDNA and nuclear DNA (nDNA) was measured in 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). Results: MtDNA/nDNA was higher in patients with OSAS than in the control group (150.94 +/- 49.14 vs 128.96 +/- 45.8; p = 0.04), the levels of ROMs were also higher in OSAS subjects (329.71 +/- 70.17 vs 226 +/- 36.76; p = 0.04) and they were positively correlated with MtDNA/nDNA (R = 0.5, p < 0.01). Conclusions: In OSAS patients there is a Mitochondrial DNA damage induced by the increase of oxidative stress. Intermittent hypoxia seems to be the main mechanism which leads to this process.