TLR2 and obstructive sleep apnea syndrome: Multivariate linear regression analysis showed that OSA was the independent factor of DNA methylation levels over CpG sites #1, #2, #3, #18, #25 and #28 of the TLR2 promoter region, CpG sites #1 and #3 of the TLR6 gene body, and protein expressions of TLR6 (Tables 2 and S3).