Association of VDR gene polymorphisms with heart disease in chronic kidney disease patients

Physiological Evidence and Therapeutic Outcomes of Vitamin D on Cardiovascular Diseases

Vitamin D hormone is an important regulator of various physiological functions, and its deficiency is characterized by an imbalance in parathyroid hormone and calcium homeostasis. The role of vitamin D in cardiovascular physiology is well demonstrated in animal and humanbased studies. In this context, hyperlipidemia, increased atherogenic plaques, cardiac inflammation, hypertension, myocarditis, myocardial infarction, and heart failure are some of the commonest known conditions connected with vitamin D deficiency. Supplementation of vitamin D is recommended to achieve normal serum vitamin D concentrations, nonetheless, in clinical trials often seen discrepancies concerning the supplementation effects and effectiveness. This review summarizes the data on the role of vitamin D in cardiovascular health along with some recent clinical findings regarding the effects of vitamin D supplementation.

Fok I and Bsm I gene polymorphism of vitamin D receptor and essential hypertension: a mechanistic link

The vitamin D receptor (VDR) gene serves as a good candidate gene for susceptibility to essential hypertension. The gene regulates the renin angiotensin system by influencing blood pressure regulation. Around 3% of the human genome is regulated by the vitamin D endocrine system. Several studies have reported mixed results with respect to relationship of VDR gene and hypertension. Observational evidence supports the concept that vitamin D plays a role in the pathogenesis of cardiovascular disease and arterial hypertension which is further supported by meta-analysis and case control studies reporting how VDR polymorphism leads to the onset and development of hypertension. In this review, we summarize the existing literature on the link between VDR and hypertension, including mechanistic studies, observational data, and clinical trials showing relationship of vitamin D level and hypertension with a focus on recent findings related to genetic studies that showed the relationship of VDR gene polymorphism with vitamin D level in hypertensive and normotensive groups. As a result, determining the association of VDR polymorphisms with essential hypertension is expected to aid in the risk assessment for the condition.

Vitamin D and Glomerulonephritis

Vitamin D presents a plethora of different functions that go beyond its role in skeletal homeostasis. It is an efficient endocrine regulator of the Renin–Angiotensin–Aldosterone System (RAAS) and erythropoiesis, exerts immunomodulatory effects, reduces the cardiovascular events and all-cause mortality. In Chronic Kidney Disease (CKD) patients, Vitamin D function is impaired; the renal hydrolyzation of its inactive form by the action of 1α-hydroxylase declines at the same pace of reduced nephron mass. Moreover, Vitamin D major carrier, the D-binding protein (DBP), is less represented due to Nephrotic Syndrome (NS), proteinuria, and the alteration of the cubilin–megalin–amnionless receptor complex in the renal proximal tubule. In Glomerulonephritis (GN), Vitamin D supplementation demonstrated to significantly reduce proteinuria and to slow kidney disease progression. It also has potent antiproliferative and immunomodulating functions, contributing to the inhibitions of kidney inflammation. Vitamin D preserves the structural integrity of the slit diaphragm guaranteeing protective effects on podocytes. Activated Vitamin D has been demonstrated to potentiate the antiproteinuric effect of RAAS inhibitors in IgA nephropathy and Lupus Nephritis, enforcing its role in the treatment of glomerulonephritis: calcitriol treatment, through Vitamin D receptor (VDR) action, can regulate the heparanase promoter activity and modulate the urokinase receptor (uPAR), guaranteeing podocyte preservation. It also controls the podocyte distribution by modulating mRNA synthesis and protein expression of nephrin and podocin. Maxalcalcitol is another promising alternative: it has about 1/600 affinity to vitamin D binding protein (DBP), compared to Calcitriol, overcoming the risk of hypercalcemia, hyperphosphatemia and calcifications, and it circulates principally in unbound form with easier availability for target tissues. Doxercalciferol, as well as paricalcitol, showed a lower incidence of hypercalcemia and hypercalciuria than Calcitriol. Paricalcitol demonstrated a significant role in suppressing RAAS genes expression: it significantly decreases angiotensinogen, renin, renin receptors, and vascular endothelial growth factor (VEGF) mRNA levels, thus reducing proteinuria and renal damage. The purpose of this article is to establish the Vitamin D role on immunomodulation, inflammatory and autoimmune processes in GN.

Role of Vitamin-D Receptor (VDR) single nucleotide polymorphisms in gestational hypertension development: A case-control study

Background

Recent literature data have highlighted the important role of hypovitaminosis D in pregnancy complications and prenatal/perinatal health. Vitamin D action takes place through vitamin D receptor (VDR) activation. Two single nucleotide polymorphisms of VDR gene, FokI and BsmI, have been reported to affect VDR molecular signaling and be associated with several disorders, including hypertension.

Methods

We carried out a case-control study aimed to assess vitamin D serum levels together with the distribution of VDR FokI and BsmI in a population of 116 pregnant women with gestational hypertension (GH) and 69 normotensive pregnant women (CTR).

Results

Hypovitaminosis D was largely prevalent both in GH (81%) and CTR (69%) pregnant women. Vitamin D insufficiency (10–30 ng/ml) had a similar frequency in both cohorts (GH 60% vs CTR 58%), while vitamin D deficiency (<10 ng/ml) was more frequent in GH cohort than in CTR one (21% vs 11%). Regression analysis showed that GH was significantly (p = 0.031) linked to vitamin D status. Vitamin D deficiency was associated with a threefold-increased risk of developing GH, while a normal vitamin D status was protective against this pregnancy disorder. The VDR FF/bB haplotype was the most frequent in GH cohort, and resulted to increase by two folds the risk for GH. Notably, hypovitaminosis D was found in 92% of FF/bB GH pregnant women, 27% of which had deficient vitamin D levels compared with 11% of their normotensive counterparts.

Conclusions

Despite being preliminary, these findings suggest that genotyping of pregnant women for VDR polymorphisms may be useful for a tailored vitamin D supplementation strategy.

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.

BSMI single nucleotide polymorphism in vitamin D receptor gene is associated with decreased circulatory levels of serum 25-hydroxyvitamin D among micro and macrovascular complications of type 2 diabetes mellitus

Vitamin D Receptor (VDR) gene single nucleotide polymorphism (SNP) in the intron 8 is a well characterized SNP which has previously been linked to various diseases including Type 2 Diabetes Mellitus (T2DM). However, the association of this SNP with micro and macrovascular complications of T2DM remains poorly studied. Hence, the present study was designed to investigate the association of VDR gene SNP with complications of T2DM (disease phenotype) and correlated it with the serum levels of (25[OH]D) (intermediate phenotype) along with other clinical risk factors of T2DM. Genotyping was carried out in a total of 866 subjects, in which Group-I had Control subjects (n = 252), Group-II with T2DM without complications (n = 200); Group-III and Group-IV had subjects with micro (n = 216) and macrovascular (n = 198) complications respectively by PCR -RFLP. The 'G' allele of the VDR gene SNP is associated with a significant risk for T2DM, Diabetic Neuropathy (DN) and Coronary Artery Disease (CAD). In addition, subjects with mutant GG genotype had lower levels of (25[OH]D) in both T2DM and micro-macrovascular complications than AA genotype. Thus, VDR (rs1544410) SNP was found to be associated with decreased serum (25[OH]D) levels in both micro-macrovascular complications of T2DM among South Indian Population.

Estimating the mutational load for cardiovascular diseases in Pakistani population

The deleterious genetic variants contributing to certain diseases may differ in terms of number and allele frequency from population to population depending on their evolutionary background. Here, we prioritize the deleterious variants from Pakistani population in manually curated gene list already reported to be associated with common, Mendelian, and congenital cardiovascular diseases (CVDs) using the genome/exome sequencing data of Pakistani individuals publically available in 1000 Genomes Project (PJL), and Exome Aggregation Consortium (ExAC) South Asia. By applying a set of tools such as Combined Annotation Dependent Depletion (CADD), ANNOVAR, and Variant Effect Predictor (VEP), we highlighted 561 potentially detrimental variants from PJL data, and 7374 variants from ExAC South Asian data. Likewise, filtration from ClinVar for CVDs revealed 03 pathogenic and 02 likely pathogenic variants from PJL and 112 pathogenic and 42 likely pathogenic variants from ExAC South Asians. The comparison of derived allele frequencies (DAF) revealed many of these prioritized variants having two fold and higher DAF in Pakistani individuals than in other populations. The highest number of deleterious variants contributing to common CVDs in descending order includes hypertension, atherosclerosis, heart failure, aneurysm, and coronary heart disease, and for Mendelian and congenital CVDs cardiomyopathies, cardiac arrhythmias, and atrioventricular septal defects.