Influence of vitamin D receptor polymorphisms on biochemical markers of mineral bone disorders in South African patients with chronic kidney disease

The vitamin D receptor TaqI TT genotype is associated with type 1 diabetes in the Black South African population

Polymorphisms in the vitamin D receptor (VDR) gene (BsmI (rs1544410), FokI (rs2228570), ApaI (rs7975232), TaqI (rs731236)) and low vitamin D concentrations have previously been associated with type 1 diabetes (T1D). Vitamin D is thought to mediate the switch from a pro-inflammatory Th1 response to an anti-inflammatory Th2 response which is protective against the development of T1D. These associations are inconsistent across studies and population groups. These associations have not been investigated in the South African black population. Thus, this observational, case-control study aims to address this knowledge gap. South African black participants with T1D (cases; n = 182) and healthy controls (n = 151) were genotyped for the four VDR polymorphisms using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Vitamin D levels were measured using high performance liquid chromatography (HPLC). Vitamin D levels were not significantly different between cases and controls (62.8 ± 20.7 vs. 59.5 ± 17.0 nmol/l, respectively; P = 0.122). Higher vitamin D levels were associated with the TaqI TT (P = 0.045) and FokI TT/TC (P = 0.014) genotypes in multivariate analyses. Furthermore, the TaqI TT genotype was associated with T1D status in multivariate analysis (P = 0.040). The FokI CC genotype increases the transcription of CYP24A1, resulting in vitamin D catabolism and thus decreased vitamin D concentration through the action of 24-hydroxlase. The TaqI TT genotype results in increased vitamin D potentially through calcium metabolism feedback pathways. In addition, the TaqI TT genotype is associated with T1D through a vitamin D-independent mechanism and may be in linkage disequilibrium with a true causative variant.

Vitamin D status and VDR gene polymorphisms in patients with growth hormone deficiency: A case control Tunisian study

Introduction

Growth Hormone Deficiency (GHD) is a rare disease marked by a complete or partial reduction in the production of growth hormone. Vitamin D deficiency is frequent and may be associated with several pathologies. However, the association between GHD and vitamin D deficiency has not been extensively studied. This study aimed to analyse VDR gene polymorphisms related to vitamin D status to ensure better care for patients with GHD.

Material and methods

A case-control study was conducted at the Children's Hospital of Tunis in collaboration with the Farhat Hached's Hospital of Sousse, including patients with GHD and healthy subjects. Genetic analysis of the VDR gene polymorphisms was performed using PCR-RFLP technique. Haplotypes were examined with Haploview software, while statistical analyses were carried out using SPSS and R programming language.

Results

Our study revealed significant differences in vitamin D (p = 0, 049) and calcium concentrations between patients and healthy subjects, which were lower in the GHD group (p = 0,018). A comparison of allelic and genotypic frequencies of the five polymorphisms indicated an association between the FokI polymorphism and GHD. Furthermore, significant difference was observed between the ApaI genotypes and PTH (p = 0,019) and ALP (p = 0,035). FokI genotypes were associated with phosphorus (p = 0,021). Additionally, One haplotype, CTAGT, exhibited a significant difference between the patients and healthy subjects (p = 0,002).

Conclusion

Our study findings indicate that hypovitaminosis D is common among patients with GHD, even when undergoing treatment with rhGH. This underscores the critical importance of vitamin D supplementation during treatment.

Vitamin D receptor (BsmI) gene polymorphism and allele frequency among chronic kidney disease patients in south Indian population

The vitamin D receptor (VDR) axis plays an important role in multiple physiological renal functions. BsmI gene is one among the VDR gene plays a vital role in maintaining this VDR axis and any polymorphism in VDR gene will cause dysfunction of renal tissues. The main objective of the study is to study the link between BsmI VDR gene polymorphism and Chronic Kidney Disease (CKD). This was a case-control study, which includes 100 cases and 100 controls. BsmI gene analysis was done by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP). Among 100 CKD study participants, BB (wild-type) genotype of BsmI gene was present in 7 patients (7%), Bb (heterozygous) genotype was present in 23 patients (23%) and bb (mutant) genotype was present in 70 patients (70%). And among 100 controls, 92 subjects were found to have BB genotype and 8 subjects were found to have Bb genotype and none of subjects were found to have bb genotypes. CKD patients with Bb and bb genotypes were found to have significantly elevated serum urea, creatinine and decreased Glomerular Filtration Rate (GFR) when compared to the BB genotype of BsmI gene. 'b' allele of BsmI gene, Bb and bb genotypes of BsmI gene plays a greater role in Guanine/Adenine single nucleotide polymorphism of BsmI gene in CKD.

Vitamin D receptor gene polymorphisms in chronic kidney disease Egyptian children: effect on biochemical markers of bone mineral disorders

INTRODUCTION

The aim of this study was to assess the association between four vitamin D receptor (VDR) single nucleotide polymorphisms BsmI (rs1544410), ApaI (rs7975232), FokI (rs2228570) and TaqI (rs731236) and the susceptibility to chronic kidney disease (CKD) in Egyptian children and to evaluate their association with mineral status in these patients.

MATERIAL AND METHODS

The current study included 305 patients with CKD and 100 apparently healthy children. We measured the serum vitamin D (VD), para-thyroid hormone (PTH) level and fibroblast growth factor 23 (FGF-23) levels by ELISA method. The genotyping of the four VDR gene variants was carried out by PCR-RFLP technique.

RESULTS

The TaqI AG & the BsmI TT genotypes were associated with a significantly higher risk of CKD. The expression of 25-OH D serum level was decreased in patients with TaqI GG & AG genotypes groups and in patients with BsmI TT genotype group The expression of PTH serum level was increased in patients with BsmI CT genotype group. The expression of FGF-23 serum level was increased in patients with Taq1 AG genotype group. We found 3 specific haplotypes; AGCA, AGCC and GGCA for healthy controls.

CONCLUSIONS

Our study showed an association between VDR TaqI, BsmI polymorphisms and the susceptibility to CKD. The existence of VDR vari-ants affected the protein expression of VD, FGF-23 and PTH. The AGCA, AGCC and GGCA haplotypes were considered as protec-tive factors against the development of renal nephropathy in our population.

Structural and functional insights on vitamin D receptor and CYP24A1 deleterious single nucleotide polymorphisms: A computational and pharmacogenomics perpetual approach

The development of chronic kidney disease (CKD) drugs remains a challenge due to the variations in the genes. The vitamin D receptor (VDR) and Cytochrome 24A1 (CYP24A1) genetic variants might affect the drug potency, efficacy and pathway. Here we have to analyse and determine the deleterious single-nucleotide polymorphisms (nsSNPs) of VDR and CYP24A1 genes and their different population's drug responses in different populations to understand the key role in CKD. Among that the large scale of nsSNP, we used certain computational tools that predicted six missense variants are observed to be significantly damaging effect and SNP variability with large differences in various populations. Molecular docking studies were carried out by clinical and our screened compounds to VDR and CYP24A1. Docking results revealed all the compounds have a good binding affinity (Score). The screened compounds (TCM_2868 and UNPD_141613) show good binding affinity when compared to known compounds. The QM/MM study revealed that the compounds have electron transfer ability and act as a donor/acceptor to mutated proteins. The structural and conformational changes of protein complexes were analysed by molecular dynamics study. Hence, this study helps to identify suitable drugs through drug discovery in CKD treatment. The abovementioned compounds have more binding affinity, efficacy, and potency of both wild and mutant of VDR and CYP24A1.

Current treatment options for secondary hyperparathyroidism in patients with stage 3 to 4 chronic kidney disease and vitamin D deficiency

Introduction: Secondary hyperparathyroidism (SHPT) represents a complication of chronic kidney disease (CKD). Vitamin D system is altered since early CKD, and vitamin D deficiency is an established trigger of SHPT. Although untreated SHPT may degenerate into tertiary hyperparathyroidism with detrimental consequences in advanced CKD, best treatments for counteracting SHPT from stage 3 CKD are still debated. Enthusiasm on prescription of vitamin D receptor activators (VDRA) in non-dialysis renal patients, has been mitigated by the risk of low bone turnover and positive calcium-phosphate balance. Nutritional vitamin D is now suggested as first-line therapy to treat SHPT with low 25(OH)D insufficiency. However, no high-grade evidence supports the best choice between ergocalciferol, cholecalciferol, and calcifediol (in its immediate or extended-release formulation).Areas covered: The review discusses available data on safety and efficacy of nutritional vitamin D, VDRA and nutritional therapy in replenishing 25(OH)D deficiency and counteracting SHPT in non-dialysis CKD patients.Expert opinion: Best treatment for low 25(OH)D and SHPT remains unknown, due to incomplete understanding of the best homeostatic, as mutable, adaptation of mineral metabolism to CKD progression. Nutritional vitamin D and nutritional therapy appear safest interventions, whenever contextualized with single-patient characteristics. VDRA should be restricted to uncontrolled SHPT by first-line therapy.

Vitamin D receptor polymorphisms and bone health after kidney transplantation

Background/aim

Bone disease is one of the most prominent complications after kidney transplantation. Bone diseases include osteoporosis, persistent secondary hyperparathyroidism, and avascular necrosis (AVN). We investigated the relationship between the polymorphisms of the vitamin D receptor (VDR) gene and bone diseases occurring after kidney transplantation.

Materials and methods

The study consists of 234 kidney allograft recipients with a minimum follow-up of five years after kidney transplantation. Patients with glomerular filtration rates less than 30 mL/min/1.73m2, a history of parathyroidectomy, bisphosphonate use pre- or post-transplantation, and cinacalcet use posttransplantation excluded. We evaluated associations between the polymorphisms of the VDR gene (BsmI, TaqI, ApaI, FokI, and Cdx2), the first-year bone mineral density (BMD) scores, persistent secondary hyperparathyroidism, and AVN.

Results

Patients with low BMD scores were significantly younger (P = 0.03) and had higher intact parathormone (iPTH) levels (P = 0.03). Cdx2 TT genotype significantly increases the risk of low BMD scores (OR: 3.34, P = 0.04). Higher phosphate levels were protective against abnormal BMD scores (OR: 0.53; P = 0.03). Patients with persistent hyperparathyroidism had significantly longer dialysis vintage and higher pretransplantation iPTH levels (P = 0.02 and P < 0.001, respectively). Cdx2, CT/TT, and ApaI CA/AA genotypes significantly increase the risk of persistent hyperparathyroidism (OR: 6.81, P < 0.001, OR: 23.32, P < 0.001, OR:4.01, P = 0.02, and OR: 6.30, P = 0.01; respectively). BsmI CT/TT genotypes were found to increase AVN risk with an HR of 3.48 (P = 0.03). Higher hemoglobin levels were also found to decrease AVN risk with an HR of 0.76 (P = 0.05).

Conclusion

Certain VDR gene polymorphisms are associated with a higher risk for bone diseases after kidney transplantation.