Relationship of Vitamin D Binding Protein Polymorphisms and Lung Function in Korean Chronic Obstructive Pulmonary Disease

Purpose

Multiple genetic factors are associated with chronic obstructive pulmonary disease (COPD). The association of gene encoding vitamin D binding protein (VDBP, GC) with COPD has been controversial. We sought to investigate the types of GC variants in the Korean population and determine the association of GC variants with COPD and lung function in the Korean population.

Materials and Methods

The study cohort consisted of 203 COPD patients and 157 control subjects. GC variants were genotyped by the restriction fragment-length polymorphism method. Repeated measures of lung function data were analyzed using a linear mixed model including sex, age, height, and pack-years of smoking to investigate the association of GC genetic factors and lung function.

Results

GC1F variant was most frequently observed in COPD (46.1%) and controls (42.0%). GC1S variant (29.0% vs. 21.4%; p=0.020) and genotype 1S-1S (8.3% vs. 3.4%; p=0.047) were more commonly detected in control than COPD. According to linear mixed model analysis including controls and COPD, subjects with genotype 1S-1S had 0.427 L higher forced expiratory volume in 1 second (FEV₁) than those with other genotypes (p=0.029). However, interaction between the genotype and smoking pack-year was found to be particularly significant among subjects with genotype 1S-1S; FEV₁ decreased by 0.014 L per smoking pack-year (p=0.001).

Conclusion

This study suggested that GC polymorphism might be associated with lung function and risk of COPD in Korean population. GC1S variant and genotype 1S-1S were more frequently observed in control than in COPD. Moreover, GC1S variant was more common in non-decliners than in rapid decliners among COPD.     

外周维生素D结合蛋白、25-羟维生素D和原发性肝细胞癌风险的关系

目的 25-羟维生素D[25(OH) D)]已被证明与原发性肝细胞癌(HCC)的发生有关,但对于维生素D结合蛋白(VDBP)在原发性肝细胞癌发生中的作用却知之甚少.作者检测了25(OH)D的主要载体维生素D结合蛋白(VDBP),研究其在25(OH)D与原发性肝细胞癌风险中的作用.方法 收集146例HCC患者和249名对照组的血样,检测血浆VDBP和25(OH)D的浓度.采用logistic回归计算比值比(OR)和95％可信区间(CI),评估外周血VDBP、25(OH)D与原发性肝细胞癌的发生风险之间的关系.结果 血浆VDBP浓度与HCC风险之间呈负相关;血浆25(OH)D与HCC风险呈正相关.只有在25(OH)D浓度高于中位数的人群中,VDBP升高显著,降低了HCC风险.在VDBP浓度低于中位数的人群中,高浓度的25(OH)D显著提高了HCC风险.结论 高浓度的VDBP可结合更多的25(OH)D,减少游离25(OH)D的生物利用度,同时检测VDBP和25(OH)D水平对于确定维生素D与HCC风险的相关性非常重要.     

Hypovitaminosis D in a Young Lebanese Population: Effect of GC Gene Polymorphisms on Vitamin D and Vitamin D Binding Protein Levels

Bioactive vitamin D is a steroid hormone transported in blood via the vitamin D binding protein (DBP). Our study aimed to investigate the vitamin D status in a young Lebanese population and study the association of hypovitaminosis with levels of DBP. Polymorphisms in the GC gene that encodes DBP were also screened. Blood samples were collected from 179 university students. Vitamin D status and DBP levels were assayed by enzyme‐linked immunosorbent assay (ELISA). DNA was extracted from 128 participants, and genotyping of the two GC gene SNPs, rs7041, and rs4588, was carried out by restriction fragment length polymorphism. Forty‐seven percent of participants had hypovitaminosis D (<20 ng/ml). A significant positive correlation was observed between vitamin D status and DBP. Genotyping data showed that participants carrying the rs7041 GG and rs4588 AA genotypes had higher concentrations of DBP than those carrying other genotypes. Four allelic versions of the GC gene were observed, one of which, GC*3, was encountered for the first time in this study, and was found to be associated with both normal vitamin D and high DBP levels. Modifying genes such as GC could therefore affect DBP levels, and contribute, along with environmental factors, to the hypovitaminosis D observed in sunny countries.     

Vitamin D binding protein and vitamin D in human allergen‐induced endobronchial inflammation

Allergic asthma is a chronic disease of the airways associated with airway hyperresponsiveness, a variable degree of airflow obstruction, airway remodelling and a characteristic airway inflammation. Factors of the vitamin D axis, which include vitamin D metabolites and vitamin D binding protein (VDBP), have been linked to asthma, but only few data exist about their regulation in the lung during acute allergen‐induced airway inflammation. Therefore, we analysed the regulation of factors of the vitamin D axis during the early‐ and late‐phase reaction of allergic asthma. Fifteen patients with mild allergic asthma underwent segmental allergen challenge. VDBP was analysed in bronchoalveolar lavage fluid (BALF) and serum using the enzyme‐linked immunosorbent assay (ELISA) technique. 25‐hydroxyvitamin D₃ [25(OH)D₃] and 1,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] were analysed by a commercial laboratory using the liquid chromatography–mass spectrometry (LC/MS) technique. VDBP (median 2·3, range 0·2–7·1 μg/ml), 25(OH)D₃ (median 0·060, range < 0·002–3·210 ng/ml) and 1,25(OH)₂D₃ (median < 0·1, range < 0·1–2·8 pg/ml) were significantly elevated in BALF 24 h but not 10 min after allergen challenge. After correction for plasma leakage using the plasma marker protein albumin, VDBP and 25(OH)D₃ were still increased significantly while 1,25(OH)₂D₃ was not. VDBP and 25(OH)D₃ were correlated with each other and with the inflammatory response 24 h after allergen challenge. Serum concentrations of all three factors were not influenced by allergen challenge. In conclusion, we report a significant increase in VDBP and 25(OH)D₃ in human BALF 24 h after allergen challenge, suggesting a role for these factors in the asthmatic late‐phase reaction.     

Association analysis between polymorphism rs2373115 of gene GRB-associated binding protein 2 and Mongolian Alzheimer patients

GRB-associated binding protein 2 (GAB2) may function as a risk factor of Alzheimer disease (AD) by affecting hyperphosphorylation of tau, causing neurofibrillary tangles. There had been genomewide analysis discovering polymorphism rs2373115 correlated with AD and in this study we performed an association analysis on this polymorphism in 107:100 Mongolian Alzheimer patients and controls in order to discover whether this correlation can be replicated in Chinese minority group. The results showed negative results, indicating GAB2 rs2373115 polymorphism was not a remarkable factor in developing Alzheimer disease among Mongolian.     

Circulating complexes of the vitamin D binding protein with G-actin induce lung inflammation by targeting endothelial cells

This study investigated the actin scavenger function of the vitamin D binding protein (DBP) in vivo using DBP null (−/−) mice. Intravenous injection of G-actin into wild-type (DBP+/+) and DBP−/− mice showed that contrary to expectations, DBP+/+ mice developed more severe acute lung inflammation. Inflammation was restricted to the lung and pathological changes were clearly evident at 1.5 and 4 h post-injection but were largely resolved by 24 h. Histology of DBP+/+ lungs revealed noticeably more vascular leakage, hemorrhage and thickening of the alveolar wall. Flow cytometry analysis of whole lung homogenates showed significantly increased neutrophil infiltration into DBP+/+ mouse lungs at 1.5 and 4 h. Increased amounts of protein and leukocytes were also noted in bronchoalveolar lavage fluid from DBP+/+ mice 4 h after actin injection. In vitro, purified DBP-actin complexes did not activate complement or neutrophils but induced injury and death of cultured human lung microvascular endothelial cells (HLMVEC) and human umbilical vein endothelial cells (HUVEC). Cells treated with DBP-actin showed a significant reduction in viability at 4 h, this effect was reversible if cells were cultured in fresh media for another 24 h. However, a 24-h treatment with DBP-actin complexes showed a significant increase in cell death (95% for HLMVEC, 45% for HUVEC). The mechanism of endothelial cell death was via both caspase-3 dependent (HUVEC) and independent (HLMVEC) pathways. These results demonstrate that elevated levels and/or prolonged exposure to DBP-actin complexes may induce endothelial cell injury and death, particularly in the lung microvasculature.     

Cofactor regulation of C5a chemotactic activity in physiological fluids. Requirement for the vitamin D binding protein, thrombospondin-1 and its receptors

Factors in physiological fluids that regulate the chemotactic activity of complement activation peptides C5a and C5a des Arg are not well understood. The vitamin D binding protein (DBP) has been shown to significantly enhance chemotaxis to C5a/C5a des Arg. More recently, platelet-derived thrombospondin-1 (TSP-1) has been shown to facilitate the augmentation of C5a-induced chemotaxis by DBP. The objective of this study was to better characterize these chemotactic cofactors and investigate the role that cell surface TSP-1 receptors CD36 and CD47 may play in this process. The chemotactic activity in C-activated normal serum, citrated plasma, DBP-depleted serum or C5 depleted serum was determined for both normal human neutrophils and U937 cell line transfected with the C5a receptor (U937–C5aR). In addition, levels of C5a des Arg, DBP and TSP-1 in these fluids were measured by RIA or ELISA. Results show that there is a clear hierarchy with C5a being the essential primary signal (DBP or TSP-1 will not function in the absence of C5a), DBP the necessary cofactor and TSP-1 a dependent tertiary factor, since it cannot function to enhance chemotaxis to C5a without DBP. Measurement of the C5a-induced intracellular calcium flux confirmed the same hierarchy observed with chemotaxis. Moreover, analysis of bronchoalveolar lavage fluid (BALF) from patients with the adult respiratory distress syndrome (ARDS) demonstrated that C5a-dependent chemotactic activity is significantly decreased after anti-DBP treatment. Finally, results show that TSP-1 utilizes cell surface receptors CD36 and CD47 to augment chemotaxis, but DBP does not bind to TSP-1, CD36 or CD47. The results clearly demonstrate that C5a/C5a des Arg needs both DBP and TSP-1 for maximal chemotactic activity and suggest that the regulation of C5a chemotactic activity in physiological fluids is more complex than previously thought.