Genetic variation in claudin-2, hypercalciuria, and kidney stones

Exploring the Critical Role of Tight Junction Proteins in Kidney Disease Pathogenesis

BACKGROUND

Kidney disease poses a significant global health challenge, marked by a rapid decline in renal function due to a variety of causative factors. A crucial element in the pathophysiology of kidney disease is the dysregulation of epithelial cells, which are vital components of renal tissue architecture. The integrity and functionality of these cells are largely dependent on tight junctions (TJ) proteins, complex molecular structures that link adjacent epithelial cells. These TJ not only confer cellular polarity and maintain essential barrier functions but also regulate epithelial permeability.

SUMMARY

TJ proteins are pivotal in their traditional role at cell junctions and in their non-junctional capacities. Recent research has shifted the perception of these proteins from mere structural elements to dynamic mediators of kidney disease, playing significant roles in various renal pathologies. This review explores the multifaceted roles of TJ proteins, focusing on their functions both within and external to the renal epithelial junctions. It highlights how these proteins contribute to mechanisms underlying kidney disease, emphasizing their impact on disease progression and outcomes.

KEY MESSAGES

TJ proteins have emerged as significant players in the field of nephrology, not only for their structural role but also for their regulatory functions in disease pathology. Their dual roles in maintaining epithelial integrity and mediating pathological processes make them promising therapeutic targets for kidney disease. Understanding the intricate contributions of TJ proteins in kidney pathology offers potential for novel therapeutic strategies, aiming to modulate these proteins to halt or reverse the progression of kidney disease.

Association of single nucleotide genetic polymorphisms of vitamin D receptor and calcium-sensitive receptor with calcium-containing kidney stones in Chinese Dai populations: a prospective multi-center study

PURPOSE

To evaluate the association between vitamin D receptor (VDRs) and calcium-sensitive receptor (CaSR) gene polymorphisms and calcium-containing kidney stones (CCKS) in Dai populations.

METHODS

A total of 160 CCKS patients and 87 healthy controls were included in this study. CCKS was confirmed using urological computed tomography (CT), plain abdominal radiograph, or surgical lithotomy. Stone samples obtained during surgery were analyzed using infrared spectroscopy. Venous blood and 24-h urine samples were collected and analyzed using Sanger sequencing and high-performance liquid chromatography, respectively. Genetic variants in the VDR gene (rs7975232, rs2228570, rs731236, and rs1544410) and CaSR gene (rs7652589, rs1801725, and rs1042636) were identified through sequence analysis.

RESULTS

Analysis of genotype and allele frequencies revealed that the rs7975232 polymorphism in the VDR gene and the rs7652589 allele in the CaSR gene were significantly associated with CCKS. Furthermore, patients carrying the AC and AA genotypes of rs7975232 showed a higher incidence of hypocitraturia compared to those with other genotypes (p < 0.05). The AA and GG genotypes of rs1042636 and the AA genotype of rs7652589 were significantly associated with hypercalciuria (p < 0.05).

CONCLUSION

CCKS in this study population may be closely related to hypocitraturia caused by the VDR locus rs7975232 polymorphism and hypercalciuria caused by the CaSR locus rs1042636 and rs7652589 polymorphism.

Unravelling the Complex Relationship between Diet and Nephrolithiasis: The Role of Nutrigenomics and Nutrigenetics

Nephrolithiasis is an increasingly prevalent condition, especially in high income countries, and is associated with high morbidity. Extraordinary progress in genetics made the identification of genetic forms of nephrolithiasis possible. These genetic diseases are usually rare and do not account for the most common forms of nephrolithiasis that are the result of several factors such as environment, dietary habits, and predisposing genes. This knowledge has shaped what we classify as nephrolithiasis, a condition that is now recognized as systemic. How and to what extent all these factors interact with one another and end in kidney stone formation, growth, and recurrence is not completely understood. Two new research fields have recently been trying to give some answers: nutrigenomics and nutrigenetics. These fields have the aim of understanding the intricate diet/genome interface that influences gene expression regulation mainly through epigenetic mechanisms and results in specific medical conditions such as cancer, metabolic syndrome, and cardiovascular diseases. Epigenetics seems to play a crucial role and could represent the link between environmental factors, that we are constantly exposed to, and risk factors for nephrolithiasis. In this systematic review, we summarize all the available evidence of proven or hypothesized epigenetic mechanisms related to nephrolithiasis.

The correlation between promoter hypermethylation of VDR, CLDN, and CasR genes and recurrent stone formation

Objectives

Recurrent Kidney stone formation is a main medical problem imposing a significant burden on both healthcare and the economy worldwide. Environmental and genetic factors have been linked to a bigger risk of kidney stone formation. We aim to assess the role of methylation on recurrent stone formation in three target genes.

Methods

We aimed to check the association between promoter hypermethylation vitamin D receptor (VDR), calcium-sensing receptor (CaSR), and claudin 14 (CLDN14) genes in recurrent kidney stones. We enrolled 30 consecutive recurrent kidney stone formers (age 18–60 years) (cases) and 30 age and gender-matched controls.3. To identify promoter methylation, two target regions from each candidate gene were bisulfited after blood collection and DNA extraction. Methylation quantification was done through methylation-specific high resolution melting (MS-HRM).

Results

The mean age of the patients and controls (mean ± SD) was 49.58 ± 14.23 years and BMI 36.12 ± 2.72. The methylation status in all six target regions was meaningfully different between the stone-former group and controls when methylation was considered in three clusters of unmethylated, methylated, and hypermethylated. A higher effect in VDR and CLDN was observed compare to CasR (p-value < 0.001, and < 0.005 versus p-value < 0.256).

Conclusions

Methylation as an important epigenetic mechanism should be considered more in recurrent stone formations. Promoter hypermethylation of VRD and CLDN genes may have an essential role in recurrent kidney stones formations.