Calcium-sensing receptor gene polymorphisms in patients with calcium urolithiasis: a systematic review

CASR, CLDN 14, ALPL & SLC34A1 genes are associated with the risk of nephrolithiasis in Egyptian children

BACKGROUNDS

The pathophysiology of nephrolithiasis is complex, influenced by both environmental and genetic factors. Calcium is the most prevalent metabolite present in the stone matrix. Stimulating the basolateral calcium sensing receptor (CASR) in the renal tubules leads to an increase in claudin-14 expression, reducing paracellular calcium permeability and increasing urinary Ca2+ excretion. Alkaline phosphatase (ALPL) hydrolyzes the pyrophosphate to free phosphate, proposing its potential role in nephrolithiasis development. Solute carrier family 34 member 1 (SLC34A1) encodes Na+-Pi cotransporter 2a, playing a key role in renal absorption of phosphate. We aimed to detect the risk of CASR, CLDN14, ALPL, and SLC34A1 gene polymorphisms on the development of nephrolithiasis in the Egyptian children.

METHODS

We enrolled 143 children diagnosed with nephrolithiasis and 112 healthy controls. Real-time polymerase chain reaction analysis of CASR (rs1801725 G/T & rs73186030 C/T), CLDN14 (rs219780 C/T & rs199565725 AC/del), ALPL (rs149344982 A/G, rs1976403 A/C & rs1256328 C/T), and SLC34A1 (rs11746443 G/A) single-nucleotide polymorphisms (SNPs) were performed.

RESULTS

We observed that children carrying the T allele of CASR rs1801725, CLDN14 rs219780, and ALPL rs1256328 SNPs were at a greater risk of nephrolithiasis compared to the control group (p = 0.003, p < 0.001, and p = 0.001, respectively). The children with the del allele of CLDN14 rs199565725 and the ALPL rs1976403 C allele had a significantly higher risk of developing nephrolithiasis compared to the control group (p = 0.007 & p = 0.001, respectively). The individuals who have the A allele of ALPL rs149344982 and SLC34A1 rs11746443 had a significantly higher risk of nephrolithiasis compared to the control group (p < 0.001). We found that CLDN14 rs219780 CT, ALPL rs149344982 AG, ALPL rs1256328 TT, and SLC34A1 rs11746443 GA genotypes were the final predictors of nephrolithiasis in children (p < 0.05). Individuals with ATAT and GTAT haplotypes had approximately a 29- and 19-fold increased risk of nephrolithiasis.

DISCUSSION

Nephrolithiasis is a complex disease caused by genetic and environmental factors. It would be beneficial if, among patients with recurrent kidney stones, the nephrologists could identify patients at high risk who would benefit from personalized therapy, a controlled lifestyle, and regular check-ups using the necessary investigation. There are several gene polymorphisms that were identified as the risk factor for developing nephrolithiasis. We found that CASR rs1801725 G/T, CLDN14 rs199565725 AC/del & rs219780 C/T, ALPL rs149344982 A/G, rs1976403 A/C & rs1256328 C/T, SLC34A1 rs11746443 G/A were associated with an increased risk of nephrolithiasis in Egyptian children. The study limitations include a lack of detailed information on nephrolithiasis risk factors such as diet and body mass index.

CONCLUSION

CLDN14 rs219780 CT, ALPL rs149344982 AG, ALPL rs1256328 TT, and SLC34A1 rs11746443 GA genotypes were the final predictors of nephrolithiasis in children.

Haplotype of CaSR gene is associated with risk of renal stone disease in West Indian population

Calcium is the most abundant metabolite involved in the stone matrix. The CaSR gene controls calcium homeostasis, and genetic variation in the CaSR gene could lead to the development of renal stone disease. Therefore, the current study has been designed to assess the association of genetic variants of CaSR gene polymorphisms with renal stone disease. A single-centric prospective study has been carried out on a total of 300 participants (150 cases and 150 controls). Serum levels of calcium, creatinine, parathyroid hormone, and 24 h urine metabolites were measured. Two polymorphisms, rs1801725 and rs1042636, of the CaSR gene, have been genotyped for each participant. T test, binary logistic regression, and Chi-square analysis were used for statistical analysis. Renal stone patients had significantly higher levels of serum parathyroid hormone, creatinine, and 24-h urine metabolites in comparison to the controls. CaSR gene variants, rs1801725 (GG) and rs1042636 (AA), both have shown significant association with renal stone disease. In addition, individuals having specific genotypes along with metabolic abnormalities such as hypercalcemia and hyperparathyroidism are found to be at a higher significant risk of developing the renal stone disease. In the present study, the haplotype of the CaSR gene has shown an association with renal stone disease. Individuals with hyperparathyroidism and hypercalcemia and risk genotype have a higher susceptibility to developing renal stone disease.

The roles of calcium-sensing receptor (CaSR) in heavy metals-induced nephrotoxicity

The kidney is a vital organ responsible for regulating water, electrolyte and acid-base balance as well as eliminating toxic substances from the blood in the body. Exposure of humans to heavy metals in their natural and occupational environments, foods, water, and drugs has serious implications on the kidney's health. The accumulation of heavy metals in the kidney has been linked to acute or chronic renal injury, kidney stones or even renal cancer, at the expense of expensive treatment options. Therefore, unearthing novel biomarkers and potential therapeutic agents or targets against kidney injury for efficient treatment are imperative. The calcium-sensing receptor (CaSR), a G-protein-coupled receptor (GPCR) is typically expressed in the parathyroid glands and renal tubules. It modulates parathyroid hormone secretion according to the serum calcium (Ca²⁺) concentration. In the kidney, it modulates electrolyte and water excretion by regulating the function of diverse tubular segments. Notably, CaSR lowers passive and active Ca²⁺ reabsorption in distal tubules, which facilitates phosphate reabsorption in proximal tubules and stimulates proton and water excretion in collecting ducts. Moreover, at the cellular level, modulation of the CaSR regulates cytosolic Ca²⁺ levels, reactive oxygen species (ROS) generation and the mitogen-activated protein kinase (MAPK) signaling cascades as well as autophagy and the suppression of apoptosis, an effect predominantly triggered by heavy metals. In this regard, we present a review on the CaSR at the cellular level and its potential as a therapeutic target for the development of new and efficient drugs against heavy metals-induced nephrotoxicity.

The genetic framework for development of nephrolithiasis

Over 1%–15% of the population worldwide is affected by nephrolithiasis, which remains the most common and costly disease that urologists manage today. Identification of at-risk individuals remains a theoretical and technological challenge. The search for monogenic causes of stone disease has been largely unfruitful and a technological challenge; however, several candidate genes have been implicated in the development of nephrolithiasis. In this review, we will review current data on the genetic inheritance of stone disease, as well as investigate the evolving role of genetic analysis and counseling in the management of nephrolithiasis.

The low levels of circulating hepatocyte growth factor in nephrolithiasis cases: independent from gene polymorphism

Environmental and genetic factors are important in development of nephrolithiasis. In a recent study, it has been demonstrated that hepatocyte growth factor (HGF) has an anti-apoptotic effect and thus can reduce the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells. The aim of this study was to evaluate the HGF serum levels and its two gene polymorphisms and possible association of the two in patients with nephrolithiasis. One hundred and five patients with nephrolithiasis and 70 healthy volunteers with similar demographic features were included in this study. Serum HGF levels were measured, and HGF intron 13 C>A (in 102 stone patients and 68 healthy subjects) and intron 14 T>C (in 99 stone patients and 56 healthy subjects) polymorphisms were determined using real-time polymerase chain reaction with TaqMan allelic discrimination method. There were no statistically significant differences in HGF intron 13 C>A and intron 14 T>C polymorphisms between the control and patient groups (X (2) = 1.72 df = 2; p = 0.42, and X (2) = 0.68 df = 2; p = 0.71, respectively). Mean serum HGF concentration was significantly lower in the stone disease patients than in the control subjects (1.05 ± 0.63 pg/mL and 1.35 ± 0.58 ng/mL respectively, p = 0.0001). When allele distribution frequency between stone patients and healthy subjects was compared, there were no significant differences in intron 13 and intron 14 allele distributions between two groups (p = 0.43 and p = 0.44, respectively). It may be concluded from the findings that decrease in HGF levels may play a role in renal stone formation, independent from gene polymorphisms.