Vitamin D receptor: A highly versatile nuclear receptor

The Fok1 vitamin D receptor gene polymorphism and 25(OH) D serum levels and prostate cancer among Jordanian men

BACKGROUND

Prostate cancer (PCa) is one of the most commonly diagnosed neoplasms and the second leading cause of cancer death in men in the Western world. Vitamin D (1,25dihydroxy vitamin D) is linked to many biological processes that influence oncogenesis but data on relations between its genetic variants and cancer risk have been inconsistent. The aim of this study was to determine associations between a vitamin D genetic polymorphism and 25-hydroxyvitamin D [25(OH)D] levels and prostate cancer.

MATERIALS AND METHODS

Genomic DNA was extracted from 124 Jordanian prostate cancer patients and 100 healthy volunteers. Ethical approval was granted from the ethical committee at Hashemite University and written consent was given by all patients. PCR was used to amplify the vitamin D receptor Fok1 polymorphism fragment. 25(OH)D serum levels were measured by competitive immunoassay.

RESULTS

All genotypes were in Hardy-Weinberg equilibrium. Genotype frequency for Fok1 genotypes FF, Ff and ff was 30.7%, 61.3% and 8.06%, for prostate cancer patients, while frequencies for the control group was 28.0%, 66.0% and 6.0%, respectively, with no significant differences. Vitamin D serum level was significantly lower in prostate cancer patients (mean 7.7 ng/ml) compared to the control group (21.8 ng/ml). No significant association was noted between 25(OH)D and VDR Fok1 gene polymorphism among Jordanians overall, but significant associations were evident among prostate cancer patients (FF, Ff and ff : 25(OH)D levels of 6.2, 8.2 and 9.9) and controls (19.0, 22.5 and 26.3, respectively). An inverse association was noted between 25(OH)D serum level less than 10 ng/ml and prostate cancer risk (OR 35.5 and 95% CI 14.3- 88.0).

CONCLUSIONS

There is strong inverse association between 25(OH)D serum level less than 10 ng/ml level and prostate cancer risk.

Serum levels of vitamin D, vitamin D-binding protein and vitamin D receptor in migraine patients from central Anatolia region

OBJECTIVES

Inflammation is proposed to be involved in the pathogenesis of both vitamin D deficiency and migraine. However, the data examining the relation of vitamin D with migraine are limited. We aimed to investigate the serum levels of vitamin D, vitamin D-binding protein (VDBP) and vitamin D receptor (VDR) in combination, in migraine patients from central Anatolia region.

METHODS

Fifty-two newly diagnosed migraine patients and age- and sex-matched 49 control subjects were enrolled in this cross-sectional prospective study. Migraine diagnosis was settled according to the International Classification of Headache Disorders-II diagnostic criteria. Serum samples were analysed for the measurement of vitamin D, VDBP and VDR levels by using commercial enzyme-linked immuno sorbent assay kits.

RESULTS

Serum vitamin D and VDR levels were found to be significantly lower in migraine patients than in controls (p = 0.012 and p = 0.038, respectively); whereas serum VDBP levels were similar between the groups (p > 0.05). There was no correlation between serum vitamin D, VDBP and VDR levels and headache characteristics including aura, attack severity, frequency and duration, and disease duration (p > 0.05). In terms of headache characteristics, no significant difference between migraineurs with vitamin D values < 25 and ≥ 25 ng/ml was observed (p > 0.05).

CONCLUSIONS

The present findings may suggest that decreased serum vitamin D levels were associated with migraine.

Vitamin D Metabolites; Protective versus Toxic Properties: Molecular and Cellular Perspectives

Vitamin D plays an essential role in bone metabolism. The discovery that the vitamin D receptor (VDR), a member of the nuclear receptor superfamily, is expressed in most tissues led researchers to investigate other biological actions of vitamin D. These effects were found to include anti-inflammatory effects and anti-atherogenesis, decreased renin activity and biosynthesis, induction of cell differentiation, inhibition of cell growth, and immunomodulation. In spite of the plethora of evidence on the protective effects of vitamin D, the reports on its intoxication still are considerably few. Therefore, in this review we aim to summarize the molecular and cellular bases of the protect-ive and toxic vitamin D actions that are mediated mostly by VDR. This review will also shed light on vitamin D metabolites other than the active metabolite calcitriol and particularly 25-hydroxy vitamin D (25(OH)D), putting emphasis on its magnifying role in vitamin D intoxication. One of the important themes we discuss is defining serum levels of beneficial or toxic effects of other exogenous vitamin D administration and its impact on 25(OH)D serum levels in animals and human subjects.

Reprint of: Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

VDR expression on circulating endothelial progenitor cells in dialysis patients is modulated by 25(OH)D serum levels and calcitriol therapy

BACKGROUND/AIMS

Vitamin D deficiency is associated with endothelial dysfunction in uremic patients, possibly by the impairment in the number and function of endothelial progenitor cells (EPCs). In 89 hemodialysis patients, we investigated the factors associated with the number of circulating EPCs (CD34+/CD133+/KDR+ and CD34+/CD133-/KDR+ cells), the presence of VDR and the determinants of VDR expression on EPCs, in particular in calcitriol therapy.

METHODS

EPC counts, percentages of VDR-positive EPCs and VDR expression were assessed by flow cytometry. Cells isolated from a subgroup of patients were cultured to analyze colony-forming units, specific markers expression and a capillary-like structure formation.

RESULTS/CONCLUSIONS

Our study demonstrates the presence of VDR on EPCs. In our dialysis patients, the parameters studied on both CD34+/CD133+/KDR+ and CD34+/CD133-/KDR+ cells, in particular VDR expression, seem to be influenced by uremia-related factors, including anemia, inflammation, diabetes, 25(OH)D serum levels and calcitriol therapy.

No association between vitamin D receptor polymorphisms and coronary artery disease in a Chinese population

The clinical features suggest that genetic factors may have a strong influence on susceptibility to coronary artery disease (CAD). The aim of this study was to investigate the association between FokI (rs2228570) and BsmI (rs1544410) of the vitamin D receptor (VDR) gene polymorphisms and patients with CAD in a Chinese population. One hundred and fifty-two CAD patients and 212 healthy controls were genotyped for the FokI and BsmI polymorphisms in VDR gene using polymerase chain reaction-restriction fragment length polymorphism. No significant differences were observed in the genotype and allele frequencies of the FokI and BsmI polymorphisms between the cases and controls (For FokI: odds ratio = 1.11, 95% confidence interval 0.83-1.50; for BsmI: odds ratio = 0.74, 95% confidence interval 0.44-1.23). There was no significant difference in the genotype distribution or the allele frequencies of VDR FokI and BsmI between two groups in a Chinese population.

Association of genetic polymorphisms in vitamin D receptor gene and susceptibility to sporadic prostate cancer

Genetic and environmental factors are involved in prostate cancer (PCa) etiology. Single nucleotide polymorphisms (SNPs) may contribute to the PCa pathogenesis. The goal of this study is to determine the role of vitamin D receptor (VDR) gene polymorphisms and haplotypes in the development and progression of sporadic PCa. One hundred and thirty-three PCa patients and 157 age-matched healthy controls were genotyped for the Apa I (rs7975232), Bsm I (rs1544410) and Taq I (rs731236) polymorphisms in VDR gene by using polymerase chain reaction-restriction fragment length polymorphism. An association was observed between the Apa I polymorphism and PCa predisposition (P = 0.03). When compared with AA genotype, there was a highly notable difference in the frequencies of the Aa (P = 0.02), aa (P = 0.026) and Apa I ''a'' allele carriers (Aa + aa) (P = 0.009) genotypes. Furthermore, we found a statistical difference in the allele frequencies of the Apa I polymorphism between the sporadic PCa patients and control subjects (P = 0.013). The genotype distribution for the Bsm I and Taq I polymorphisms were similar between cases and controls (P > 0.05). No clinically significant relationship was found between the three-locus haplotypes and development of sporadic PCa. The genotype frequencies for the three polymorphisms of the VDR gene within subgroups of PCa (defined by tumor stage, Gleason score, PSA levels) were also analyzed, but no statistically noteworthy difference was observed (P > 0.05). As far as we know, this is the first study which investigates the relationship between VDR genotypes and sporadic PCa in the Turkish population. Our findings suggest that the VDR ApaI (rs7975232) polymorphism may play a role in the development of sporadic PCa.