Association between vitamin D receptor FokI. Polymorphism and serum parathyroid hormone level in patients with chronic renal failure

Profile of vitamin D receptor gene polymorphism TaqI in patients with periodontitis

The present study aimed to assess the incidence of the vitamin D receptor (VDR) gene polymorphism TaqI in patients with periodontitis, and the potential association of this polymorphism with the severity of the disease. This was a case-controlled study, which included 162 adults divided into two groups as follows: Case group (81 patients diagnosed with periodontitis) and control group (81 patients without periodontitis). Venous blood was obtained from each sample from which DNA was extracted. The gene polymorphism was determined using restricted fragment length polymorphism-PCR and DNA sequencing to identify endonuclease restrictions in exon 9 (TaqI). The data were analyzed using an independent samples t-test. VDR gene polymorphisms were detected in periodontitis cases with TT (86.4%), Tt (12.4%) and tt (1.2%) genotypes. DNA sequencing confirmed a change in the sequence of the VDR gene nucleotides in patients with periodontitis. The data indicated that the severity of periodontal tissue damage may be influenced by changes in the nucleotide sequence.

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.

Association between vitamin D receptor (FokI) genetic variant rs2228570 and iron profile in hemodialysis patients

Iron deficiency is a common etiology of anemia that causes suboptimal response to erythropoietin therapy in hemodialysis (HD) patients. This study investigated the association between vitamin D receptor (VDR) genetic variant (FokI) rs2228570 with iron indices (serum iron, transferrin, transferrin saturation, and ferritin). Sixty adequately hemodialyzed patients subdivided into two groups; 31 patients with transferrin saturation (TSAT) < 20% and 29 with TSAT > 20% who received I.V sodium ferric gluconate, calcium, and vitamin D. Sixty normal healthy were selected as the control group.. VDR genetic variant (SNP rs2228570) was genotyped in all subjects using PCR/RFLP. HD patients showed a higher frequency of rs2228570 FF genotype (38.3%) than controls (31.7%). The frequency of ff genotype and f allele in patients (8.4 and 35% respectively) were significantly lower than controls (25 and 46.7% respectively). Allele model (f vs. F): OR 0.721, 95% CI 0.521-0.998, P = 0.049. While (ff vs. FF): OR 0.452, 95% CI 0.223-0.917, P = 0.028. The distribution of Ff + ff genotypes in HD cases with TSAT > 20% was higher than in HD cases with TSAT < 20%, Dominant model (Ff +ff vs FF): OR 2.753, 95% CI 1.902-3.409, P = 0.048. f allele showed lower frequency in low TSAT group than high TSAT group (27.4 vs. 43.1%) with significant P value (P = 0.042) with allele model (f vs. F): OR 2.012, 95% CI 1.923-4.226, P = 0.042. Fok-1 ff, Ff + ff genotypes were significantly associated with TSAT > 20% with a protective effect against low TSAT in HD patients.

Effects of genetic variants on serum parathyroid hormone in hyperparathyroidism and end-stage renal disease patients: A systematic review and meta-analysis

BACKGROUND

Parathyroid hormone (PTH) is one of the principal regulators of calcium homeostasis, crucial for normal functioning of the kidneys, bones, heart, and nervous system. Different pathologic conditions can affect serum PTH level resulting in hyperparathyroidism or hypoparathyroidism. Our study assessed the association of previously reported polymorphisms with the level of PTH (expressed in pg/mL) among individuals with different pathologic conditions affecting PTH level.

METHODS

We searched Web of Science, MEDLINE, and Scopus to identify relevant articles published up to July 2017. The search yielded 6967 publications of which 44 fulfilled the inclusion criteria. We conducted meta-analyses for calcium-sensing receptor gene (CaSR) rs1801725 polymorphism in patients with primary hyperparathyroidism and vitamin D receptor gene (VDR) rs1544410 polymorphism in patients with end-stage renal disease (ESRD).

RESULTS

None of the polymorphisms were significantly associated with PTH levels in the overall population. In subgroup analysis by ethnicity for VDR rs1544410 gene polymorphism, we found significant differences under dominant model (SMD: -0.18 [-0.32, -0.05], P < .01) and AA versus GG comparison (SMD: -0.29 [-0.52, -0.06], P < .01) in Asian patients with ESRD, while nominally significant results (P < .05) were observed for AG versus GG and AA versus GG comparisons in European individuals with ESRD.

CONCLUSION

Scientific evidence of genetic association of serum PTH level among individuals with different pathologic conditions remains deficient and published results provide weak evidence. Further well-conducted studies on larger sample sets designed according to evidence-based principles are warranted to assure clinically applicable findings.

Genome-wide meta-analysis identifies novel loci associated with parathyroid hormone level

Background

Parathyroid hormone (PTH) is one of the principal regulators of calcium homeostasis. Although serum PTH level is mostly accounted by genetic factors, genetic background underlying PTH level is insufficiently known. Therefore, the aim of this study was to identify novel genetic variants associated with PTH levels.

Methods

We performed GWAS meta-analysis within two genetically isolated Croatian populations followed by replication analysis in a Croatian mainland population and we also combined results across all three analyzed populations. The analyses included 2596 individuals. A total of 7,411,206 variants, imputed using the 1000 Genomes reference panel, were analysed for the association. In addition, a sex-specific GWAS meta-analyses were performed.

Results

Polymorphisms with the lowest P-values were located on chromosome 4 approximately 84 kb of the 5′ of RASGEF1B gene. The most significant SNP was rs11099476 (P = 1.15 × 10⁻⁸). Sex-specific analysis identified genome-wide significant association of the variant rs77178854, located within DPP10 gene in females only (P = 2.21 × 10^− 9). There were no genome-wide significant findings in the meta-analysis of males.

Conclusions

We identified two biologically plausible novel loci associated with PTH levels, providing us with further insights into the genetics of this complex trait.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0018-5) contains supplementary material, which is available to authorized users.

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

BACKGROUND

It remains unclear whether genetic factors may explain the reported variation in the levels of biochemical markers of chronic kidney disease mineral and bone disorders (CKD- MBD) across ethnic groups. Therefore, the aim of this study was to examine the influence of vitamin D receptor (VDR) polymorphisms on secondary hyperparathyroidism and its association with vitamin D levels in black and white South African study participants.

METHODS

This was a cross sectional study involving 272 CKD stage 3- 5D patients and 90 healthy controls. The four major VDR polymorphisms (Bsm 1, Fok 1, Taq 1, and Apa1) were genotyped using the polymerase chain reaction- restriction fragment length polymorphism (PCR -RFLP) method. In addition, biochemical markers of CKD-MBD were measured to determine their associations with the four VDR polymorphisms.

RESULTS

With the exception of Taq I polymorphism, the distribution of the VDR polymorphisms differed significantly between blacks and whites. In hemodialysis patients, the Bb genotype was significantly associated with moderate secondary hyperparathyroidism (OR, 3.88; 95 CI 1.13-13.25, p = 0.03) and severe hyperparathyroidism (OR, 2.54; 95 CI 1.08-5.96, p = 0.03). This was consistent with the observed higher levels of median parathyroid hormone, fibroblast growth factor 23 and mean phosphate in patients with Bb genotype. This candidate risk genotype (Bb) was over represented in blacks compared to whites (71.0% versus 55.6%, p < 0.0001). In an unadjusted regression model, FokFf genotype was found to be significantly associated with the risk of developing severe vitamin D deficiency < 15 ng/ml (OR, 1.89; 95 CI 1.17-3.07, p = 0.01).

CONCLUSION

The VDR Bb genotype is an independent predictor of developing secondary hyperparathyroidism in patients with end stage kidney disease. In addition, study participants with FokFf genotype are at increased of developing severe 25 -hydroxyvitamin D [25(OH)D] deficiency.

Vitamin D receptor polymorphism in chronic kidney disease patients with complicated cardiovascular disease

Several studies indicate a relationship between vitamin D and cardiovascular disease. Pleiotropic actions of vitamin D and its analogs are mediated by vitamin D receptor (VDR). VDRs have been identified in almost all tissues, including vascular smooth muscle cells, cardiomyocytes, and endothelial cells. The FokI and BsmI polymorphisms of the VDR gene are regarded as strong markers of disturbed vitamin D signaling pathway. Studies investigating the relationship between VDR genotypes and left ventricular hypertrophy revealed a highly significant association with the BsmI Bb heterozygous genotype. There are conflicting data on the action of vitamin D in left ventricular hypertrophy. Experimental as well as observational studies and small clinical trials have suggested that vitamin D administration may favorably influence left ventricular hypertrophy, whereas large randomized clinical trials have shown negative results. However, a beneficial effect on the left atrial volume index and the duration of hospitalization were observed in patients treated with vitamin D analogs. Larger clinical trials with robust clinical end points are needed to confirm that vitamin D is effective in preventing cardiovascular disease in chronic kidney disease patients and in general population.

Associations among four polymorphisms (BsmI, FokI, TaqI and ApaI) of vitamin D receptor gene and end-stage renal disease: a meta-analysis

BACKGROUND AND AIMS

To evaluate the association between vitamin D receptor (VDR) BsmI, FokI, TaqI and ApaI gene polymorphisms and the risk of end-stage renal disease (ESRD).

METHODS

All eligible studies were included in our meta-analysis of a search of the PubMed, Cochrane and China National Knowledge Infrastructure (CNKI) databases according to predefined criteria. The fixed-effects or random-effects models were used to calculate the pooled odds ratio (OR) and corresponding 95% confidence interval (CI).

RESULTS

Thirteen studies including 1510 patients and 1812 controls were recruited for the analysis of the association between the VDR BsmI, FokI, TaqI and ApaI gene polymorphisms and the risk of ESRD.VDR BsmI B allele, BB genotype and bb genotype, FokI F allele, FF genotype and ff genotype, TaqI T allele, TT genotype and tt genotype, ApaI A allele, AA genotype and aa genotype were not associated with ESRD susceptibility for overall populations, Asians and Caucasians.

CONCLUSIONS

Results from the current study suggest that VDR BsmI, FokI, TaqI and ApaI gene polymorphisms are not associated with the risk of ESRD in the overall populations, Asians and Caucasians. However, more studies should be performed in the future.

Vitamin D receptor gene polymorphism and left ventricular hypertrophy in chronic kidney disease

FokI and BsmI polymorphisms of vitamin D receptor (VDR) gene are regarded as reliable markers of disturbed vitamin D signaling pathway. Left ventricular hypertrophy (LVH) is a strong cardiovascular risk marker in end stage renal disease (ESRD) patients. Since BsmI polymorphism has been associated with LVH in ESRD patients, we addressed this study in patients with chronic kidney disease (CKD) not yet on dialysis. One hundred and forty five patients with CKD stage 3 were genotyped for FokI and BsmI VDR polymorphisms, in order to assess the relationships between these VDR polymorphisms, some markers of mineral bone disorders, and LVH measured by echocardiography. Patients bearing either the Ff heterozygous or FF homozygous genotype had significantly higher PTH values than those bearing the ff genotype. The relationships between VDR genotypes and LVH revealed a highly significant association of the BsmI Bb heterozygous genotype with LVH. In patients with CKD stage 3 BsmI B allele was independently related to LVH. Since LVH is a frequent finding in dialysis population due to several mechanisms, the presence of the same relationship in patients with CKD strengthens the hypothesis that alterations of vitamin D signaling are implicated in LVH development in patients with renal diseases.

Fok-I polymorphism of vitamin D receptor gene and the presence of renal dysfunction in patients with β-thalassemia major

Recent evidence supports the presence of renal dysfunction even among young patients with β-thalassemia major. However, the possible genetic contribution has never been investigated. The aim of this study was to correlate the presence of Fok-I polymorphism of the vitamin D receptor gene with abnormal levels of early markers of renal impairment in children and young adults with thalassemia. Thirty-four patients (19 male and 15 female) with β-thalassemia major on conventional treatment, with a mean decimal age of 14.62 ± 5.47 years (range: 5-22 years), were included in the study. Markers of renal function were determined in serum and in urine and patients were genotyped for Fok-I gene polymorphism. Genotype frequencies were similar to those previously reported for other populations: 47.06% of the patients were homozygous for the F allele, 41.18% were heterozygous, and 11.76% were homozygous for the f allele. A considerable number of patients demonstrated impaired renal function with increased serum cystatin C levels (29.41%), glomerular dysfunction with proteinuria (68%), as well as significant tubulopathy with hypercalciuria (73.08%), and increased levels of urinary β(2)-microglobulin (29.41%). When patients were stratified according to Fok-I polymorphism, a significantly higher prevalence of abnormally increased serum levels of cystatin C was observed in patients being homozygous for the f allele (75%) compared with those being heterozygous (Ff) or homozygous for the F allele (14.29% and 31.25%, respectively, P = .02). Further studies are needed to confirm these preliminary results and elucidate the possible mechanisms involved.

Genetic variation in the vitamin D receptor and polycystic ovary syndrome risk

The possible association of vitamin D receptor gene FokI, BsmI, ApaI, and TaqI polymorphisms with polycystic ovary syndrome (PCOS) risk, and their influence on insulin resistance and serum levels of insulin in the women with PCOS was examined. The findings of the present study indicate that genetic variation in the vitamin D receptor may affect PCOS development as well as insulin resistance in women with PCOS.

Iron indices and vitamin D receptor polymorphisms in hemodialysis patients

Cardiovascular disease caused by accelerated atherosclerosis is the major determinant of morbidity and mortality in chronic kidney disease patients. Vitamin D and its analogs provide survival benefit for hemodialysis (HD) patients. Vitamin D exerts its effects through the vitamin D receptor (VDR) that is coded for by a gene showing several polymorphisms that, in turn, are associated with a variety of diseases and differential responses to vitamin D. In this study, we evaluated the association between 4 VDR polymorphisms (ie, those identified by the restriction enzymes BsmI, ApaI, TaqI, and FokI) and iron indices (serum iron, transferrin, transferrin saturation, and ferritin) in 88 hemodialysis patients routinely treated with vitamin D. The absence or presence of the BsmI, ApaI, TaqI, and FokI restriction sites were denominated B and b, A and a, T and t, F and f, respectively. Our results show that in HD patients with transferrin saturation <20%, the F allele was more frequent than in HD patients with transferrin saturation >20% (P = .03). This relationship may provide a link between VDR alleles and iron and nutritional markers, which are highly predictive variables of cardiovascular morbidity and mortality in hemodialysis patients.

Gene polymorphism association studies in dialysis: bone and mineral metabolism

Abnormalities in bone and mineral metabolism have a significant impact on morbidity and mortality among patients with end-stage renal disease (ESRD). In addition to confounding environmental factors, genetic susceptibility factors may also influence the occurrence and severity of these abnormalities and account for interindividual variability among patients. Indeed, polymorphisms involving genes of the calcium/parathyroid hormone/calcitriol axis have been associated with bone and mineral metabolism abnormalities. This review summarizes studies involving polymorphisms of candidate genes and their effects on the development of complications related to bone and mineral metabolism abnormalities among patients with ESRD.

Regression of skeletal manifestations of hyperparathyroidism with oral vitamin D

CONTEXT

Parathyroidectomy is the only effective therapy for osteitis fibrosa cystica in hyperparathyroidism.

OBJECTIVE

The objective of this study was to describe the changes of skeletal and nonskeletal manifestations in a patient with hyperparathyroidism and renal failure after oral vitamin D therapy.

DESIGN

This was a descriptive case report.

SETTING

The patient was followed up in a referral center.

PATIENT

A 55-yr-old male patient with moderate renal failure was referred for expansile lytic lesions affecting several ribs and the spinous process of T12. His creatinine was 1.8 mg/dl; calcium, 8.9 mg/dl; PTH, 666 pg/ml; and 1,25 dihydroxy-vitamin D, 27 pg/ml. Bone mineral density (BMD) Z-scores by dual-energy x-ray absorptiometry were -4.1 at the spine, -1.7 at the hip, and -4.3 at the forearm.

MAIN OUTCOME MEASURES

The main outcome measures were the skeletal manifestations of hyperparathyroidism.

RESULTS

At 10 months of therapy, calcium level was 10 mg/d, PTH level declined to 71 pg/ml, and BMD increased by 12% at the spine and 18% at the hip. Computerized tomography (CT) cuts revealed marked regression in the lytic lesions. At 2 yr, BMD increased by an additional 6% at the spine, and there were no further changes in the lytic lesions by CT. The vitamin D receptor genotype using the restriction enzymes Bsm1, Taq1, and Apa1 was Bb, tt, and AA.

CONCLUSIONS

We showed regression of severe skeletal abnormalities of hyperparathyroidism documented by serial CT images in response to oral vitamin D therapy. It is possible that the vitamin D receptor genotype of the patient modulated this response.