Determining Relationships among Genome-Wide Dna Methylation Profiles, Genome-Wide Gene Expression Profiles, and Clinical Phenotypes in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea (OSA) is a disorder in which loss of pharyngeal dilator muscle tone at sleep onset causes recurrent pharyngeal collapse and temporary cessation of breathing. OSA has now been proven to cause systemic hypertension, myocardial infarction, congestive heart failure, and stroke. Patients with OSA may have a propensity for night-time cardiac death and post-stroke death. The mainstay of medical treatment of OSA syndrome is administration of continuous positive airway pressure (CPAP) during sleep, which has been shown to decrease the risk of fatal and non-fatal cardiovascular events. Little is know about the mechanisms by which habitual snoring occurs and simple snoring develops into symptomatic OSA. Pathophysiological mechanisms and biological pathways linking oxidative stress and sleep fragmentation to various adverse consequences of OSA remains to be further clarified. DNA methylation patterns are susceptible to change in response to environmental stimuli, and play a major role in the regulation of gene expression. Chronic intermittent hypoxia induces global increases in DNA methylation and decreases in CpG methylation. To date, gene-specific CpG methylation in OSA patients has not yet been evaluated by the genome-wide methylation array. The aim of this study in first year is to investigate whole genome DNA methylation profiles in OSA patients and their correlation with the development of OSA. Two previous gene expression microarray studies have identified changes in several genes related to oxidative stress, cell cycles, and inflammation. To date, the effects of CPAP treatment, the mechanisms of the adverse consequences of OSA, and the characteristic genes able to distinguish simple snoring from OSA have not yet been evaluated by the microarray method. The aim of this study in second year is to investigate whole genome gene expression profiles in different groups of OSA patients with a negative correlation to DNA methylation status, and to identify the altered expressed genes associated with OSA.. In the third year of this study, the results of the altered methylated and expressed genes will be validated in a larger cohort. Furthermore, the decreased expression of the hypermethylated genes may be reversible using demethylating agents, such as 5-aza-2’-deoxycytidine (DAC), or histone deacetyl inhibitors, such as trichostatin A (TSA), in a cell culture model. In the first year, we will conduct this prospective case-control study to examine DNA methylation profiles of blood leukocytes in five groups (12 subjects for each group): (1) untreated OSA with adverse consequences, (2) untreated OSA without adverse consequences, (3) OSA patients with regular use of nasal CPAP, (4) simple snorers, and (5) healthy subjects, using the HumanMethylation27 BeadChip. In the second year, we will examine gene expression profiles in these 5 groups (24 subjects for each group) using HumRef-8 Expression BeadChip. In the third year, additional 24 samples from each group (total 120 samples) will be included in the validation experiments for the identified altered methylation and gene expression genes, using pyrosequencing and RT-PCR methods. Finally, we’ll apply primary peripheral blood mononuclear cells obtained from OSA patients to investigate the effects of the de-methylation agents (DAC and TSA) on the re-activation of the hypermethylated and down-regulated genes, hoping to identify novel biomarkers and targets for drug therapy in OSA.

Project ID:PC10009-0103
External Project ID:NSC100-2314-B182A-095