Introduction: Chronic obstructive pulmonary disease (COPD) is one of the world's major public health problems. It is characterized by a major inflammatory response, where vitamin D, due to its role in regulating the immune system, and genetic variants involved in its metabolism may play an essential role. The aim of this study is to evaluate the association between 13 polymorphisms related to vitamin D metabolism and the COPD risk.

Material and methods: A retrospective longitudinal study was designed in which 152 cases of COPD diagnosed at the University Hospital Virgen de las Nieves and 456 controls without the pathology, matched by age and sex, were included. The determination of the 13 polymorphisms was carried out using TaqMan™ probes.

Results: Statistical analysis showed that the AA genotype and the A allele of the CYP27B1 rs4646536 polymorphism may be associated with an increased risk of developing COPD according to genotypic models (OR = 2.6; 95% CI = 1.38-5.22; p = 0.004), dominant (OR = 1.69; 95% CI = 1.15-2.5; p = 0.008), recessive (OR = 2.24; 95% CI = 1.22-4.41; p = 0.013) and additive (OR = 1.56; 95% CI = 1.18-2.08; p =0.020) models. Likewise, the AA genotype and the A allele of the CYP2R1 rs10741657 polymorphism were also associated with the risk of developing COPD according to the genotypic (OR = 1.9; 95% CI = 1.06-3.36; p = 0.028) and additive (OR = 1.37; 95% CI = 1.04-1.81; p = 0.027) models. Likewise, an association was found between GATG (p = 0.002; OR = 2.05; 95%CI = 1.32-3.20) and AGGT (p < 0.0001; OR = 2.1e46; 95%CI = 2.1e46-2.1e46) haplotypes and an increased risk of COPD.

Conclusions: We can therefore conclude that those variants could be used in the early detection of the disease in the future.

This study was approved by the Ethical Committee of the Andalusian Health System and conducted in accordance with the Declaration of Helsinki (code: 0201-N-23). All subjects participating in the study signed a written informed consent for the collection of saliva or blood samples and their donation to the biobank. The samples were encoded and treated confidentially throughout the study.

This study included 152 patients with COPD and 456 controls of Caucasian origin from southern Spain. The cases were diagnosed and recruited at the Virgen de las Nieves University Hospital, Granada (Spain), between 2017 and 2023. All sociodemographic and clinical variables were collected through Diraya clinical software. 
The Biobank of the Virgen de las Nieves University Hospital, which is part of the Biobank of the Andalusian Public Health System, provided DNA samples isolated from saliva or blood. Saliva samples were collected in 50 mL BD Falcon conical tubes (BD, Plymouth, United Kingdom). Blood samples were collected in 3 mL BD Vacutainer® tubes with EDTA K3 as an anticoagulant. DNA extraction was performed using the QlAamp DNA Mini extraction kit (Qiagen GmbH, Hilden, Germany), following the specifications provided by the manufacturer for DNA purification from saliva or blood. Purified DNA samples were stored at −80°C in the Biobank of the Virgen de las Nieves University Hospital. DNA concentration and purity were measured with the NanoDrop 2000™ UV-visible spectrophotometer using the ratio of the absorbance at 260/280 and 260/230.

The 13 polymorphisms (rs1544410 (BsmI), rs11568820 (Cdx-2), rs2228570 (FokI), rs7975232 (ApaI), rs731236 (TaqI), rs4646536, rs3782130, rs10877012, rs703842, rs6068816, rs4809957, rs7041, rs10741657) were determined by real-time polymerase chain reaction for allele discrimination using TaqMan® probes (ABI Applied Biosystems, Quant Studio 3 Real-Time PCR System, 96 wells), following the manufacturer’s instructions. The polymorphisms VDR-Bsml (rs1544410), CYP27B1 rs703842, and CYP27B1 rs3782130 were analyzed using an assay customized by ThermoFisher Scientific (Waltham, Massachusetts, United States) encoded as AN324M4, AN9HX2K, and ANPRYR9, respectively. Sanger sequencing was performed in 10% of the samples and used to confirm of the results. Real-time PCR and Sanger sequencing were performed in the Pharmacogenetics Unit of the Virgen de las Nieves University Hospital and the Department of Biochemistry and Molecular Biology II of the University of Granada. The criteria for SNPs quality control were: 1) missing genotype rate per SNP < 0.05; 2) minor allele frequency > 0.01; 3) p-value > 0.05 in Hardy Weinberg equilibrium test; 4) missing genotype rate between cases and controls < 0.05.