Study On The Relationship Between Pathogenesis Of Tuberculosis And Vitamin D Plasma Level And Vitamin D Receptor Gene Polymorphisms

Objective: We aimed to analyze the correlation of vitamin D deficiency and the tuberculosis by detecting and comparing the plasma vitamin D levels in TB patients and healthy controls. Then we explored the link between single nucleotide polymorphisms(SNPs) of the vitamin D receptor(VDR) and active TB development in Chinese population. In this study, we investigated the association of vitamin D deficiency and VDR gene polymorphisms with susceptibility and severity to tuberculosis in comparison with health controls. Thus we can provide information and basis for further large-scale studies of the relationship between the vitamin D deficiency and VDR gene polymorphisms with active tuberculosis, and provide references for further determination of high-risk population and prevention of TB control in the future.Methods: We developed an UPLC-MS/MS method to determine the concentrations of 25(OH) D2 and 25(OH) D3 of plasma in the TB patients and healthy subjects, and then got the total concentrations of 25(OH) D, which could reflect the vitamin D levels in body. Setting 12ng/ml and 20ng/ml of 25(OH) D concentrations as the cut-off points, we divided the concentrations of vitamin D into three levels, including deficiency, inadequate and adequate. Then we grouped the subjects according to the levels of vitamin D and contrasted the mean levels and different level proportions of vitamin D. The VDR gene genotypes were measured using the polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) method. We assessed the VDR genotypes at Fok I, Bsm I, Apa I and Taq I SNP sites and grouped the subjects according to the results and then compared and contrasted the distribution differences. All data, including the clinical characteristics and laboratory test data, were collected and ordered into a uniform data format, such as general condition, drug resistant situation, culture status, radiographic severity, radiographic cavity, concomitant diseases and so on. We divided the patients into different groups accoding to the clinical characteristics and contrast the vitamin D status and VDR genotypes.Results: The method was linear from 2 to 80ng/ml for both 25(OH) D2(r=0.9980) and 25(OH) D3(r=0.9999) with intra- and inter-assay precision less than 10%. The lower quantitative limit and lower detection limit were 2ng/ml and 0.5ng/ml, respectively. This method was appropriate for the determination of 25-hydroxyvitamin D in human plasma. A total of 239 participants were enrolled into two groups(180 TB patients and 59 healthy controls) in this study, the TB patients were divided into drug sensitive TB group(n= 128) and drug resistant TB group(n= 59) according to the drug susceptibility testing results. In all the subjects, mean plasma 25(OH)D concentrations in drug sensitive TB group(C = 10.42 ng/ml) and drug resistant TB group(C = 11.11 ng/ml) were lower than that in the healthy controls(C = 21.97 ng/ml). In TB patients, participants with unilateral lesions had higher vitamin D levels compared to those with bilateral lesions(P = 0.030). In drug resistant patients, participants not combined with extrapulmonary tuberculosishad higher vitamin D levelscompared to those combined with extrapulmonary tuberculosis(P = 0.001). The frequency of ff genotype was relatively higher in drug sensitive TB group(P < 0.001) and drug resistant TB group(P < 0.001). The frequency of f allele was also relatively higher in drug sensitive TB group(P<0.001) and drug resistant TB group(P<0.001). In TB patients, participants with Ff genotype(OR 0.16,95%CI 0.06-0.45), ff genotype(OR 0.35,95%CI 0.13-0.93) or Bb genotype(OR 0.13,95%CI 0.02-0.99) had lower proportions of extrapulmonary tuberculosis. In male patients, participants with ff genotype had lower proportions of retreatment(P = 0.025) and cavity formation(P = 0.001). In drug sensitive TB patients, participants with aa genotype had lower proportion of cavity formation(P = 0.008). No significant association of VDR gene polymorphism at Taq I site with clinical characteristics of TB patients was found. In TB patients, participants with bb genotype had higher vitamin D levels(P < 0.05) compared to those with Bb genotype.Conclusion: There are relationships between the vitamin D deficiency and VDR gene polymorphisms with tuberculosis. People with lower plasma level of vitamin D may have a greater risk to develop tuberculosis. TB patients with lower plasma level of vitamin D may have a greater risk of bilateral lesions and extrapulmonary tuberculosis. The VDR gene polymorphism at Fok I site may predispose to tuberculosis development, and ff genotype may be a risk factor of tuberculosis.