Association of the vitamin D receptor gene start codon Fok I polymorphism with calcium oxalate stone disease

Predictive value of single-nucleotide polymorphism signature for nephrolithiasis recurrence: a 5-year prospective study

Background

Genetic variations are linked to kidney stone formation. However, the association of single nucleotide polymorphism (SNPs) and stone recurrence has not been well studied. This study aims to identify genetic variants associated with kidney stone recurrences and to construct a predictive nomogram model using SNPs and clinical features to predict the recurrence risk of kidney stones.

Methods

We genotyped 49 SNPs in 1001 patients who received surgical stone removal between Jan 1 and Dec 31 of 2012. All patients were confirmed stone-free by CT scan and then received follow-up at least 5 years. SNP associations with stone recurrence were analyzed by Cox proportion hazard model. A predictive nomogram model using SNPs and clinical features to predict the recurrence risk of kidney stones was developed by use of LASSO Cox regression.

Results

The recurrence rate at 3, 5, 7 years were 46.8%, 71.2%, and 78.4%, respectively. 5 SNPs were identified that had association with kidney stone recurrence risk. We used computer-generated random numbers to assign 500 of these patients to the training cohort and 501 patients to the validation cohort. A nomogram that combined the 14-SNPs-based classifier with the clinical risk factors was constructed. The areas under the curve (AUCs) at 3, 5 and 7 years of this nomogram was 0.645, 0.723, and 0.75 in training cohort, and was 0.631, 0.708, and 0.727 in validation cohort, respectively. Results show that the nomogram presented a higher predictive accuracy than those of the SNP classifier or clinical factors alone.

Conclusion

SNPs are significantly associated with kidney stone recurrence and should add prognostic value to the traditional clinical risk factors used to assess the kidney stone recurrence. A nomogram using clinical and genetic variables to predict kidney stone recurrence has revealed its potential in the future as an assessment tool during the follow-up of kidney stone patients.

CAG repeats and one polymorphism in androgen receptor gene are associated with renal calcium stone disease

PURPOSE

Evidence suggests that androgens can be involved in the pathogenesis of renal stones. This study aimed at investigating coding region polymorphisms and CAG repeats in androgen receptor (AR) and their association with active renal calcium stone disease.

MATERIALS AND METHODS

Male patients with calcium kidney stones (N = 106) with at least two episodes of stone recurrence or size increase during the past 5 years (ASF) were enrolled from December 2008 to April 2009. Control individuals were recruited after matching for age and gender from healthy individuals without current stone or history of stone disease. Genetic sequencing and single strand conformational polymorphism (SSCP) were used to determine AR polymorphisms in the patients and controls.

RESULTS

Two polymorphisms were identified in the AR gene: Silent G to A polymorphism in the first exon of the AR gene and C to G polymorphism in intron 4. CAG repeats ranged from 12 to 37. The C/G polymorphism in intron 4 and CAG repeats were associated with the status of active renal calcium stone disease (all p < 0.05). The CC variant of C/G polymorphism was not observed in patients with stone disease. CAG repeats less than 20 and more than 28 were mostly observed in ASF patients (p < 0.05).

CONCLUSIONS

CAG repeats and intron 4 C/G polymorphism in the AR gene have an association with renal calcium stone disease.

Vitamin D receptor gene polymorphisms and susceptibility to urolithiasis: a meta-regression and meta-analysis

BACKGROUND

The currently available data with respect to the association between vitamin D receptor (VDR) gene polymorphism and risk to urolithiasis are inconclusive and inconsistent. Hence, an exhaustive meta-analysis can solve the discrepancies and provide a hint for upcoming investigations. Herein, a meta-analysis was carried out to attain a conclusive estimate of the association between VDR gene single nucleotide polymorphisms (SNPs) and urolithiasis risk.

METHODS

The major databases, including ISI Web of science, Scopus, and PubMed/MEDLINE were searched systematically from until June 2020 to retrieve all relevant studies. Association between VDR gene polymorphisms, including FokI (rs2228570), TaqI (rs731236), BsmI (rs1544410), and ApaI (rs7975232), and urolithiasis risk was evaluated using pooled odds ratio (OR) and their corresponding 95% confidence interval (CI). Additionally, to seek for the potential source of heterogeneity, meta-regression analyses were exerted.

RESULTS

Literature search led to finally finding of 33 studies evaluating the VDR gene SNPs and urolithiasis risk. It was observed that none of the four SNPs were significantly associated with urolithiasis predisposition. However, subgroup analysis confirmed higher risk of urolithiasis in East-Asian and Caucasian population with ApaI and TaqI gene polymorphism. The analyses of sensitivity acknowledged the results stability.

CONCLUSION

Although this meta-analysis did not support the association of FokI, TaqI, BsmI, and ApaI in the overall polled analysis, it suggests that ApaI and TaqI SNPs is associated with increased risk of urolithiasis in East-Asian and Caucasians populations.

Relationship Between the ApaI (rs7975232), BsmI (rs1544410), FokI (rs2228570), and TaqI (rs731236) Variants in the Vitamin D Receptor Gene and Urolithiasis Susceptibility: An Updated Meta-Analysis and Trial Sequential Analysis

The relationship between urolithiasis and vitamin D receptor (VDR) gene variants is still under debate according to the available published literature. To assess correlations between VDR gene variants ApaI (rs7975232), BsmI (rs1544410), FokI (rs2228570), and TaqI (rs731236) and urolithiasis susceptibility, we performed the present study through meta-analysis. The PubMed, Cochrane Library, China National Knowledge Infrastructure, EMBASE, Web of Science, and Wanfang databases were searched to retrieve qualified case-control studies. Finally, 31 reports were selected for the present meta-analysis. The results demonstrated that the VDR gene TaqI TT genotype was related to decreased risk of urolithiasis in the overall population (TT vs. Tt+tt: P = 0.011, OR = 0.824, 95% CI = 0.709–0.957). In ethnicity subgroup analysis, we found that the TaqI variant was obviously correlated to urolithiasis risk among Asians and Caucasians (P < 0.05). Additionally, significant urolithiasis risk was identified in adults. However, the FokI, BsmI, and ApaI variants did not have an increased risk of developing urolithiasis. Trial sequential analysis results were on a sufficiently large number of participants and did not require more research to confirm associations. Our research suggested that the VDR gene variant TaqI was correlated with urolithiasis susceptibility and that the t-allele might be the risk gene and T-allele the protective gene in VDR TaqI variant.

Association of vitamin D receptor gene polymorphisms and risk of urolithiasis: results of a genetic epidemiology study and comprehensive meta-analysis

Polymorphisms of vitamin D receptor (VDR) gene have been associated with risk of urolithiasis, but, with inconsistent results and lack data from Pakistani population. Therefore, after including our indigenous study data, a comprehensive meta-analysis was performed to provide an evidence-based estimate of any association between VDR polymorphisms and urolithiasis risk. A total of 483 Pakistani subjects, comprising 235 urolithiasis patients and 248 healthy controls, were genotyped for 6 VDR polymorphisms. Additionally, a systematic literature search with subsequent meta-analysis was conducted and pooled odds ratios (ORs) were used to determine the strength of any existent associations. Trial sequential analysis (TSA) was also performed. Results revealed no significant association of any VDR polymorphism and urolithiasis risk in indigenous Pakistani patients. However, meta-analysis of 29 relevant studies indicated that VDR FokI polymorphism significantly increased the risk of urolithiasis in allelic (f vs. F: OR = 1.13; 95% CI = 1.05-1.22; p ≤ 0.01) and recessive (ff vs. FF + Ff: OR = 1.20; 95% CI = 1.05-1.38; p = 0.01) models with no significant heterogeneity. No associations were evident for VDR ApaI, BsmI and TaqI polymorphic variants and urolithiasis risk after correction for multiple testing. Subgroup analysis by ethnicity suggested significant association for FokI variant among Asians. The TSA results demonstrated that the evidence reflecting association of FokI polymorphism and urolithiasis risk was sufficient and conclusive. In conclusion, this meta-analysis suggests that VDR FokI polymorphism is significantly associated with urolithiasis risk, especially in Asians, whereas ApaI, BsmI and TaqI polymorphisms are not associated.

FokI Polymorphism of the Vitamin D Receptor Gene Is Associated with Susceptibility to Gastric Cancer: A Case-Control Study

Vitamin D is a potential protective agent against cancer, and its activity is mediated mainly by vitamin D receptor (VDR). The FokI polymorphism (rs10735810) represents a T-to-C transition (ATG to ACG) in exon 2 of the VDR gene, and this ATG represents the translation-initiation codon, encoded by the f allele. The FokI polymorphism results in the generation of a protein shortened by three amino acids, translated from the downstream ATG codon (the F allele). We investigated the relationship between the FokI polymorphism and gastric cancer in a Chinese Han population. A total of 187 patients and 212 healthy controls were enrolled. The FokI polymorphism was detected by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. The f allele frequency was higher in patients than that in controls (51.6% and 43.6%, P < 0.05). Multivariate logistics regression analysis revealed patients with the f allele (Ff + ff) showed a higher risk of gastric cancer [odds ratio (95% confidence interval) 2.73 (1.13~4.32)]. Patients with the f allele (Ff + ff) also presented a poorly differentiated type of gastric cancer (P < 0.05) and higher levels of C-reactive protein on admission than the FF group (5.5 ± 2.4 mg/L vs. 3.4 ± 1.3 mg/L, P < 0.05). Here, we show an association between the VDR FokI polymorphism and the susceptibility to gastric cancer, which may be helpful for early detection of high-risk individuals with the f allele for gastric cancer. Conversely, the F allele may be a protective factor against gastric cancer.

A whole genome SNP genotyping by DNA microarray and candidate gene association study for kidney stone disease

BACKGROUND

Kidney stone disease (KSD) is a complex disorder with unknown etiology in majority of the patients. Genetic and environmental factors may cause the disease. In the present study, we used DNA microarray to genotype single nucleotide polymorphisms (SNP) and performed candidate gene association analysis to determine genetic variations associated with the disease.

METHODS

A whole genome SNP genotyping by DNA microarray was initially conducted in 101 patients and 105 control subjects. A set of 104 candidate genes reported to be involved in KSD, gathered from public databases and candidate gene association study databases, were evaluated for their variations associated with KSD.

RESULTS

Altogether 82 SNPs distributed within 22 candidate gene regions showed significant differences in SNP allele frequencies between the patient and control groups (P < 0.05). Of these, 4 genes including BGLAP, AHSG, CD44, and HAO1, encoding osteocalcin, fetuin-A, CD44-molecule and glycolate oxidase 1, respectively, were further assessed for their associations with the disease because they carried high proportion of SNPs with statistical differences of allele frequencies between the patient and control groups within the gene. The total of 26 SNPs showed significant differences of allele frequencies between the patient and control groups and haplotypes associated with disease risk were identified. The SNP rs759330 located 144 bp downstream of BGLAP where it is a predicted microRNA binding site at 3'UTR of PAQR6 - a gene encoding progestin and adipoQ receptor family member VI, was genotyped in 216 patients and 216 control subjects and found to have significant differences in its genotype and allele frequencies (P = 0.0007, OR 2.02 and P = 0.0001, OR 2.02, respectively).

CONCLUSIONS

Our results suggest that these candidate genes are associated with KSD and PAQR6 comes into our view as the most potent candidate since associated SNP rs759330 is located in the miRNA binding site and may affect mRNA expression level.

Effects of vitamin D receptor polymorphisms on urolithiasis risk: a meta-analysis

Background

Several studies analyzed the associations of Vitamin D receptor (VDR) polymorphisms with urolithiasis risk in different ethnic groups. However, the results were inconclusive. To evaluate a more precise estimation of the relationship, a meta-analysis was performed.

Methods

Pubmed, EMBASE, Wanfang Database, China National Knowledge Infrastructure (CNKI) and Weipu Database were searched. Data were extracted independently by two investigators. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations.

Results

Twenty-three case–control studies were included in this meta-analysis. Significant associations between ApaI, BsmI, FokI, and TaqI polymorphisms and urolithiasis risk were observed. However, sensitivity analyses for BsmI and FokI polymorphisms indicated that the results were not reliable and credible. In addition, there was a significant association of the ApaI-TaqI haplotype with urolithiasis risk.

Conclusions

This meta-analysis suggested that ApaI and TaqI polymorphisms in VDR gene were associated with urolithiasis risk.

The relation between bone and stone formation

Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.

Association of calcium urolithiasis with urokinase P141L and 3'-UTR C>T polymorphisms in a Japanese population

This was a case-control study to analyze the associations between calcium urolithiasis and the urokinase polymorphisms, P141L (rs2227564) and 3'-UTR C>T (rs4065), in a Japanese population. Cases consisted of 232 patients with urinary calcium stones (174 men and 58 women) who presented to a general hospital between April 2009 and June 2011. Among these cases, 115 (49.6 %) patients had calcium oxalate stones alone, and 113 (48.7 %) patients had calcium oxalate stones mixed with calcium phosphate stones. Controls consisted of 454 subjects who had a routine health check-up in the same prefecture. The two polymorphisms were genotyped via polymerase chain reaction with confronting two-pair primers. In the control group, the genotype frequencies of P141L were 0.573 for PP, 0.375 for PL, and 0.052 for LL, and those of 3'-UTR C>T were 0.835 for CC, 0.165 for CT, and TT was not identified. Neither of the polymorphisms was significantly associated with urolithiasis. The age- and sex-adjusted odds ratios of urolithiasis were 0.96 [95 % confidence interval (CI), 0.66-1.41] for PL and 1.22 (0.58-2.57) for LL as compared with PP genotype of P141L, and 1.01 (0.62-1.64) for CT as compared with CC genotype of 3'-UTR C>T. When compared with the PP genotype of P141L, the frequency of PL was significantly lower in female cases with a family history of urolithiasis than in females without such family history (p = 0.028). P141L and 3'-UTR polymorphisms of the urokinase gene are not associated with urolithiasis in a Japanese population.

E-cadherin gene 3'-UTR C/T polymorphism in Turkish patients with nephrolithiasis

Nephrolithiasis is a complex disease and many gene polymorphisms have been associated with stone formation. In this study we aimed to investigate another possible relationship between E-cadherin gene (CHD1) 3'-UTR C/T polymorphism and calcium oxalate nephrolithiasis in the Turkish population. Study population was composed of 143 patients with nephrolithiasis and 158 control subjects. CHD1 3'-UTR C/T polymorphism was analysed using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique. Genotype distribution of the investigated polymorphism was not deviated from Hardy-Weinberg equilibrium (HWE) in patients and control subjects (P > 0.05). C allele frequency was 85.7 and 85.1% in patients and controls, respectively (P = 0.836). Genotype distributions of the CHD1 3'-UTR C/T polymorphism among patients were also not significantly different from those among control subjects (P = 0.636). Our results showed that there is no association between the CHD1 gene 3'-UTR C/T polymorphism and nephrolithiasis in our population.

Polymorphisms in the vitamin D receptor and the androgen receptor gene associated with the risk of urolithiasis

Transcriptional activity of the vitamin D receptor (VDR) gene is regulated by androgen receptor (AR) gene and both are associated with renal stone formation. We examined gene polymorphisms of VDR (PCR-RFLP) and AR (GeneScan analysis) in 125 stone formers and 150 controls from north India. Genotype Ff of Fok-I and Tt of Taq-I demonstrated significantly higher risk (P<0.001, OR=3.559 and P=0.019, 1.830 respectively). Variant f allele exhibited 1.7-folds higher risk. Ff of Fok-I and Aa of Apa-I gene polymorphism showed higher risk in males only. Mean CAG repeat was significantly higher in hypercalciuric patients as compared to normocalciuric (mean=21.62 ± 3.384 vs. 20.11 ± 3.182; P=0.034). Combined effects 1.8-folds higher risk in patients with Tt genotype of Taq-I and short CAG repeat. Thus, association of FokI and TaqI VDR gene polymorphisms suggest VDR as an important genetic marker for urolithiasis. Further, patients with combination of Tt of Taq-I and short CAG repeat were at higher risk for stone formation.

Genetic basis of renal cellular dysfunction and the formation of kidney stones

Nephrolithiasis is a result of formation and retention of crystals within the kidneys. The driving force behind crystal formation is urinary supersaturation with respect to the stone-forming salts, which means that crystals form when the concentrations of participating ions are higher than the thermodynamic solubility for that salt. Levels of supersaturation are kept low and under control by proper functioning of a variety of cells including those that line the renal tubules. It is our hypothesis that crystal deposition, i.e., formation and retention in the kidneys, is a result of impaired cellular function, which may be intrinsic and inherent or triggered by external stimuli and challenges. Cellular impairment or dysfunction affects the supersaturation, by influencing the excretion of participating ions such as calcium, oxalate and citrate and causing hypercalciuria, hyperoxaluria or hypocitraturia. The production and excretion of macromolecular promoters and inhibitors of crystallization is also dependent upon proper functioning of the renal epithelial cells. Insufficient or ineffective crystallization modulators such as osteopontin, Tamm-Horsfall protein, bikunin, etc. are most likely produced by the impaired cells.

Predisposition of genetic polymorphism with the risk of urolithiasis

Urolithiasis is a relevant clinical problem with a subsequent burden for health system. The aim of this review is to provide recent progress made using genetic polymorphisms to define pathophysiology, to identify persons at risk for kidney stone disease and to predict treatment response. Population case-control studies are useful both as an alternative and an adjunct as compared to family studies. These involve either whole genome scanning or candidate gene approaches. While whole genome scanning is likely to be widely used in future, at present, candidate gene studies are more feasible. When performing candidate gene case-control studies factors such as study design, methods for recruitment of case and controls, selection of candidate genes, functional significance of polymorphisms chosen for study and statistical analysis require close attention to ensure that only genuine associations are detected. Some of the significant genes that play role in stone formation include calcitonin receptor gene (CTR), vitamin D receptor (VDR), Urokinase, Interleukin, (IL-1β, IL-Ra), E-Cadherin, Androgen & oestrogen receptor gene, vascular endothelial growth factor (VEGF) and Arginine p21. In our case-control study we studied CTR, VDR, Urokinase, IL-1β(-511 and +3954), IL-Ra from north India and predict that VDR, IL-β (-511) and IL-1Ra gene may be used as a possible genetic marker for earlier detection in patients who are at risk for calcium oxalate stone disease. Further, linkage disequilibrium and haplotype structure of a certain candidate gene is important for association analysis. When a certain polymorphic allele has been found to be associated with disease, it is further explained on basis of LD and haplotype structure by one or more other alleles. Once it is determined which haplotype carries the risk allele, by means of molecular biological functional analyses, the variants on that haplotype allele truly causing the effect can be determined.

Association of urokinase gene 3'-UTR T/C polymorphism with calcium oxalate urolithiasis in children

INTRODUCTION AND OBJECTIVES

Urokinase is synthesized by various cells such as kidney, pneumocytes, and phagocytes. It cleaves plasminogen to plasmin and hence stimulates fibrinolysis. Urokinase breaks down the matrix protein within the stone and thus prevents stone formation and growth. Urokinase concentrations are lower and urokinase gene 3'-UTR T/C polymorphism is higher in patients with recurrent stones. Our aim was to investigate the role of urokinase gene 3'-UTR T/C polymorphism in childhood recurrent stone disease.

MATERIAL AND METHODS

A control group of 40 healthy children having no history of stone formation (group 1) (mean age 10.5+/-4.2 years), 40 children (mean age 10.5+/-4.33 years) who had calcium oxalate stones for the first time (group 2), and 40 patients (mean age 11.2+/-3.8 years) with recurrent calcium oxalate stone disease (group 3) were included in the study. The groups were compared with respect to age, gender and urokinase gene 3'-UTR T/C polymorphism. Polymerase chain reaction-based restriction analysis was used to identify C/T polymorphism of the urokinase gene.

RESULTS

No significant difference was observed between the three groups with respect to age and gender, while urokinase gene 3'-UTR T/C gene polymorphism was observed in four patients (10%) from group 3. In groups 1 and 2 there was no patient with T/C polymorphism.

CONCLUSIONS

Urokinase 3'-UTR T/C gene polymorphism seems to appear more commonly in children with recurrent calcium oxalate stone disease than in healthy children and in those with stones for the first time. These results suggest that the urokinase gene might play a role in childhood recurrent calcium oxalate stone disease.

Association of vitamin D receptor (Fok-I) polymorphism with the clinical presentation of calcium urolithiasis

OBJECTIVE

To investigate the effect of the vitamin D receptor (VDR) FokI polymorphism on the clinical presentation of calcium urolithiasis, as a FokI polymorphism in the VDR gene was recently reported to be associated with calcium metabolism disorders.

PATIENTS, SUBJECTS AND METHODS

In all, 235 patients with calcium urolithiasis and 231 age- and sex-matched healthy controls were recruited from Kaohsiung Medical University Hospital between June 2003 and February 2005. Clinical information on the age at first onset, stone episodes, stone severity and presence of family history were collected from patients with stones. Any VDR FokI polymorphism was detected using polymerase chain reaction-based restriction analysis.

RESULTS

The frequency of VDR FokI genotypes between the patients and the healthy controls was not significantly different. However, among patients, those with the FF genotype had a significantly higher risk of having more stone episodes (adjusted odds ratio 2.15, 95% confidence interval 1.02-4.54, P = 0.044) and were younger at the first onset (3.23, 1.08-9.63, P = 0.036) than those with the ff genotype.

CONCLUSION

The VDR FokI polymorphism might be important in the clinical presentation of patients with calcium urolithiasis, especially for the frequency of stone episodes and age at first onset, although it is not associated with the formation of stones.

Vitamin D receptor gene polymorphisms in patients with urolithiasis

Urolithiasis is a multifactorial disease, the onset and severity of which is influenced by both genetic and environmental factors. This study represents an investigation of the role of vitamin D receptor (VDR) gene polymorphisms (ApaI, BsmI, and TaqI) and combined genotypes in urolithiasis in a Turkish population. We studied 110 patients with urinary stones and 150 control subjects. The polymorphic regions were amplified using polymerase chain reaction, followed by digestion with restriction enzymes BsmI, ApaI, and TaqI, and analyzed electrophoretically. Genotype and allele frequencies were calculated, and the association with urolithiasis, family history, and recurrence of stone was investigated. Our data provide no evidence for an association between urolithiasis and VDR ApaI, BsmI, and TaqI genotypes. We also analyzed the effects of VDR ApaI, BsmI, and TaqI genotypes in combination; the "GTT" VDR haplotype, constructed from three adjacent restriction fragment length polymorphisms was overrepresented among the urolithiasis patients. However, no significant differences between heterozygous carriers (OR 1.302; 95% CI 0.527-3.215) and homozygous carriers (OR 3.39; 95% CI 0.719-15.985) were observed in our study population. A significant association was found only between the ApaI polymorphism and family history (P=0.017; chi (2)=5.657). Our data indicate that the VDR ApaI, BsmI, and TaqI polymorphisms do not confer a significant risk for urolithiasis.

Association of vitamin D receptor-gene (FokI) polymorphism with calcium oxalate nephrolithiasis

BACKGROUND AND PURPOSE

Formation of kidney stones is still not understood but is hypothesized to be associated with the vitamin D receptor gene (VDR). In order to assess the eventual role of VDR start-codon FokI polymorphism in stone formation, we evaluated the association between calcium stone disease and this polymorphism in a North Indian population.

PATIENTS AND METHODS

A control group comprised of 166 healthy individuals (age range 22-58 years) and a group of 138 patients with calcium oxalate stones (age range 21-72 years) were examined. The polymorphism was detected using polymerase chain reaction-based restriction analysis. An unexcisable length of 265 bp (CC) and two fragments of 169 bp and 96 bp (TT) were obtained by FokI restriction digestion.

RESULTS

There was a statistically significant difference between the control and patient groups (X2 test, P<0.001) for the genotype of the VDR FokI start-codon polymorphism. The odds ratio (with 95% CI) for the C allele in those at risk of stone disease was 1.654 (1.041, 2.628). The VDR frequency distribution was also statistically significant (P<0.001) in case of male sex. The frequency distribution for this genetic polymorphism was not statistically different in normocalciuric and hypercalciuric stone patients (P=0.355).

CONCLUSION

The VDR FokI polymorphism may be a good candidate for a marker for calcium oxalate-stone disease. These findings may contribute a small piece to the understanding of the pathogenesis of urinary calculi.

Association of vitamin-D and calcitonin receptor gene polymorphism in paediatric nephrolithiasis

We investigated the role of vitamin-D receptor gene (VDR) and calcitonin receptor (CTR) gene polymorphism in childhood nephrolithiasis in the north Indian population. A control group of 60 healthy paediatric individuals (age range 4-16 years) and 50 paediatric patients (age range 2-14 years) with kidney stones were examined. Polymorphism in both genes (VDR and CTR) was detected by using PCR-based restriction analysis. There was a statistically significant difference between the two groups for the genotypes of the VDR gene Fok-I polymorphism (P =0.007) and the CTR gene (P =0.048) polymorphism. The odds ratio (95% Confidence Interval) for the C allele in those at risk of stone disease was 1.83 (0.82-4.09) in VDR gene polymorphism and 1.99 (0.90-4.39) in the case of CTR gene polymorphism. Our results suggest that the effects of VDR (Fok-I) and CTR gene polymorphism contribute to the understanding of the pathogenesis of urinary calculi. It is also suggestive of a potential candidate gene in the search for genetic causes of paediatric calcium oxalate nephrolithiasis.

Genetics of hypercalciuria and calcium nephrolithiasis: from the rare monogenic to the common polygenic forms

Idiopathic calcium nephrolithiasis is a multifactorial disease with a pathogenesis that involves a complex interaction of environmental and individual factors. This review discusses what is known about monogenic renal calcium stone-related disorders, provides an update on genetic research in calcium nephrolithiasis and such intermediate phenotypes as idiopathic hypercalciuria, discusses the problems that these conditions pose to clinicians and geneticists interested in their pathogenesis, and proposes some method tools potentially useful in this research frame of reference.

Association of vitamin D receptor genotypes with calcium excretion in nephrolithiatic subjects in northern India

Our objective was to investigate the association between the vitamin D receptor (VDR) allelic variants (Bsm I and Fok I) and nephrolithiasis in northern India. A total of 150 nephrolithiatic patients and 100 age and sex matched controls were enrolled for study. A 10 ml blood sample was obtained for biochemical analysis and DNA isolation. In addition, 24 h urine samples were obtained from each patient for the estimation of calcium and creatinine. PCR was performed for the Bsm I and Fok I VDR variants. The association between Bsm I and Fok I VDR polymorphism and nephrolithiasis was investigated after digestion with restriction enzymes (3 U). The product was analysed on 3% agarose gel for Bsm I and 15% polyacrylamide gel for Fok I allelic variants. We did not observe any significant differences in the prevalence of either the Bsm I or Fok I VDR genotypes between stone formers and controls. The B allele was found to be more prevalent in hypercalciuric patients compared to controls and nephrolithiatic subjects. The subjects with the bb genotype exhibited a higher calcium excretion than the BB genotype. Patients with the F allele were also found to excrete higher urinary calcium. VDR genotypes may be associated with increased calcium excretion in hypercalciuric nephrolithiatic subjects.

Association between vitamin D receptor gene polymorphisms and tubular citrate handling in calcium nephrolithiasis

OBJECTIVES

Hypocitraturia is a risk factor for calcium nephrolithiasis. 1,25(OH)2D3 influences renal citrate handling and enhances citraturia. The aim of this study was to evaluate the relationship between vitamin D receptor (VDR) allelic variant and urinary citrate excretion in recurrent stone formers (SF) patients.

DESIGN

Case-control study.

SUBJECTS

A total of 220 recurrent calcium oxalate SF patients and 114 healthy control (C) subjects were enrolled for this study. Subjects with urinary tract infections, hyperparathyroidism, cystinuria >70 micromol/24 h, gouty diathesis, renal tubular acidosis, renal failure, chronic diarrhoeal states, intake of thiazide diuretics, angiotensin-converting enzyme (ACE)-inhibitors, glucocorticoids or oestrogens were excluded. A standard constant diet was given for 7 days. The 24-h urinary citrate excretion and the active tubular reabsorption of filtered citrate (Rcit) were evaluated. Hypocitraturia was defined as a urinary citrate excretion lower than 1.7 mmol day-1. Stone formers patients and C were genotyped for BsmI and TaqI VDR alleles. Contingency table chi-square tests were used to compare genotype frequencies in hypocitraturic SF patients, normocitraturic SF and C.

RESULTS

The prevalence of hypocitraturia in SF patients was 32.7% (72 of 200). Hypocitraturia in these patients resulted from excessive Rcit of a normal load of citrate. We found a different distribution (P < 0.05) of BsmI and TaqI VDR genotypes in hypocitraturic SF patients compared with normocitraturic SF and C. In particular, the prevalence of bb and TT VDR genotypes in hypocitraturic SF was significantly higher than in normocitraturic SF and C.

CONCLUSIONS

These results point to a genetic association between BsmI and TaqI VDR polymorphisms and idiopathic hypocitraturia in calcium-oxalate recurrent SF patients.

Urokinase gene 3'-UTR T/C polymorphism is associated with urolithiasis

OBJECTIVES

To study single nucleotide polymorphisms to investigate the possibility that urokinase is involved in the formation of urolithiasis, which, although lacking in genetic evidence, has been previously proposed.

METHODS

A total of 153 patients with recurrent calcium stones and 105 controls were studied. Polymerase chain reaction-based restriction analysis was used to identify the C/T polymorphism of the urokinase gene, which is mapped on the 3'-untranslated region (3'-UTR) on chromosome 10.

RESULTS

A significant difference was found in the distribution of the urokinase gene 3'-UTR C/T polymorphism frequency between patients with stones and normal controls (P <0.05). The odds ratio for the risk of the "T" allele in patients with stones was 3.088 (95% confidence interval 1.06 to 8.99).

CONCLUSIONS

The results of our study demonstrate that the urokinase gene 3'-UTR "T" allele is associated with calcium stone disease. Individuals possessing the "T" allele have a higher incidence of calcium oxalate stone disease. The results of this study provide genetic evidence that the urokinase gene may play a role in stone formation.