Journal Article

Polymorphisms of the Vitamin D Binding Protein (VDBP) and Free Vitamin D in Patients with Cystic Fibrosis

Garriga-García, María, Vicente-Santamaria, Saioa, Moreno-Álvarez, Ana, González-Jiménez, David, Reyes-Domínguez, Ana Isabel, Gutiérrez-Martínez, José Ramon, Fernández-Lorenzo, Ana Estefanía, Gómez-Alonso, Carlos, Álvarez-Beltrán, Marina, Quesada-Colloto, Paula, Gil-Peña, Helena, Avello-Llano, Noelia, Peña-Quintana, Luis, Martin-Fernández, Carmen, García-Gil-Albert, Carmen, García-Romero, Ruth, Díaz-Martin, Juan José, Mano-Hernández, Agustín De la

2024

Overview

Objectives/Background: Vitamin D-binding protein (VDBP) and free vitamin D are new markers that are being studied as a possible markers of vitamin D status. The main aim of our study was to analyze the VDBP genotype and quantify the levels of free vitamin D in a sample of cystic fibrosis (CF) patients. Methods: We conducted a multicenter, cross-sectional, and prospective study including patients with CF and exocrine pancreatic insufficiency who were clinically stable. We investigated vitamin D levels (total and free) and the different VDBP haplotypes. Free vitamin D levels were measured using an electro-chemiluminescence assay. Results: A sample of 48 patients was obtained (52% male; median age 13.8 years). The most common allele of VDBP was Gc1s (72%) > Gc2 (52%) > Gc1f (27%). The median calcidiol was 21.2 ng/mL (IR 15.3–26.9), and 81% had levels in the insufficiency range: 23 patients (48%) below 20 ng/mL, and 16 (33%) between 20 and 30 ng/mL. The median free vitamin D level was 4.2 pg/mL (IR 3.9–5.6). A positive correlation was observed between calcidiol and free vitamin D levels (r = 0.871; p < 0.0001). After adjustment for season, vitamin D supplementation, sex, and CF-related diabetes, patients with Gc1f polymorphism had a lower risk of vitamin D deficiency, OR 0.22 (95% CI 0.05–0.99), and p = 0.027. A negative linear trend was observed between the polymorphisms grouped into three categories (Gc1/Gc1, Gc1/Gc2, and Gc2/Gc2, in that order) and vitamin D and free vitamin D levels (p = 0.025 and p = 0.033, respectively). Conclusion: In CF, as in the general population, the most common VDBP haplotype in the Caucasian race is Gc1s. VDBP polymorphisms influence serum vitamin D and free vitamin D levels in CF patients. There is a good correlation between free vitamin D and calcidiol levels, suggesting that measuring the latter in CF does not seem to provide any additional benefit.

• Publisher: MDPI AG,MDPI
• Subject: Adolescent / Adult / Alfacalcidol / Alleles / Analysis / Automation / Biomarkers - blood / Body mass index / Calcifediol / Cardiovascular disease / Care and treatment / Child / Chronic illnesses / Cross-Sectional Studies / Cystic fibrosis / Cystic Fibrosis - blood / Cystic Fibrosis - genetics / Ethylenediaminetetraacetic acid / Exocrine Pancreatic Insufficiency - blood / Exocrine Pancreatic Insufficiency - genetics / Female / Gastroenterology / Genetic aspects / Genotype / Haplotypes / Hospitals / Humans / Male / Medical research / Medicine, Experimental / Patients / Pediatrics / Polymorphism, Genetic / Prospective Studies / Protein binding / Proteins / Statistical analysis / Vitamin D / Vitamin D - analogs & derivatives / Vitamin D - blood / Vitamin D Deficiency - blood / Vitamin D Deficiency - genetics / Vitamin D-Binding Protein - blood / Vitamin D-Binding Protein - genetics / Vitamin deficiency / Young Adult