DNA was isolated from peripheral blood using the QIAmp DNA mini kit (Qiagen GmbH), following the manufacturer's instructions. DNA (10 ng) was mixed with TaqMan Universal PCR Master mix II and TaqMan SNP probes (Applied Biosystems; Thermo Fisher Scientific, Inc.) and genotypes of SNPs rs2749812 were analysed with the 7500 Fast Real-Time Polymerase Chain Reaction (PCR) system with allelic discrimination according to the protocol used in a previous publication (7 (link)).