Saudi Journal of Kidney Diseases and Transplantation

BRIEF COMMUNICATION
Year
: 2021  |  Volume : 32  |  Issue : 1  |  Page : 157--162

Study of Uromodulin Gene Polymorphism in Egyptian Patients with End-Stage Renal Disease


Mostafa Abdelsalam1, Mohamad Motawea2, Fadyazmy Kyrillos2, Ahmed Abdel-Razik3, Maysaa El Sayed Zaki4, Ahmed Abdel-Wahab1,  
1 Department of Internal Medicine, Mansoura Nephrology and Dialysis Unit, Faculty of Medicine, Mansoura University, Mansoura, Egypt
2 Department of Internal Medicine, Endocrinology Unit, Faculty of Medicine, Mansoura University, Mansoura, Egypt
3 Department of Tropical Medicine, Faculty of Medicine, Mansoura University, Mansoura, Egypt
4 Department of Clinical Pathology, Faculty of Medicine, Mansoura University, Mansoura, Egypt

Correspondence Address:
Mostafa Abdelsalam
Department of Internal Medicine, Mansoura Nephrology and Dialysis Unit, Faculty of Medicine, Mansoura University, Mansoura
Egypt

Abstract

Uromodulin (UMOD) gene polymorphism has been linked with end-stage renal disease. In this research, we studied the prevalence of UMOD rs42993393 T>C in Egyptian hemodialysis (HD) patients and the blood level of UMOD in those patients. The study was a case–control study and included 100 patients on regular HD and 100 healthy control subjects. The blood samples from the studied groups were subjected to the determination of UMOD blood level and molecular study of UMOD rs42993393 T>C genotype by polymerase chain reaction with restriction fragment length polymorphism. The serum UMOD level was significantly low in patients (38.6 7.6 ng/mL) compared to control subjects (221.3 ± 54.2, P = 0.0001). On the other hand, the UMOD rs42993393T>C was significantly increased in TC in patients (28%, odds ratio 1.3–1.0–2.0) compared to controls (22%, P = 0.03), and there was a significant increase in CC in patients (10%) compared to control subjects (3%; P = 0.0001). The T allele was significantly increased in controls compared to patients with a significant increase in C allele in patients compared to controls (P = 0.01). The present study highlights the prevalence of UMOD gene polymorphism at rs42993393T>C. There was a significant prevalence of C allele and C genotypes in HD patients. This finding may indicate that this allele may be a predisposing genotype for renal failure in susceptible patients. On the other hand, the significant reduction of serum UMOD in patients with end-stage renal disease may be attributed to the reduced functioning renal mass.



How to cite this article:
Abdelsalam M, Motawea M, Kyrillos F, Abdel-Razik A, Zaki ME, Abdel-Wahab A. Study of Uromodulin Gene Polymorphism in Egyptian Patients with End-Stage Renal Disease.Saudi J Kidney Dis Transpl 2021;32:157-162


How to cite this URL:
Abdelsalam M, Motawea M, Kyrillos F, Abdel-Razik A, Zaki ME, Abdel-Wahab A. Study of Uromodulin Gene Polymorphism in Egyptian Patients with End-Stage Renal Disease. Saudi J Kidney Dis Transpl [serial online] 2021 [cited 2022 Jan 26 ];32:157-162
Available from: https://www.sjkdt.org/text.asp?2021/32/1/157/318517


Full Text



 Introduction



End-stage renal disease (ESRD) is a major health problem worldwide, with an annual incidence rate of up to 8%, and the number of the patients who receive renal replacement therapy is estimated to be more than 1.4 million. This disease represents a burden on health resources in developing countries.[1] In Egypt, there is evidence that ESRD is increasing. The leading causes of ESRD in Egyptian patients include diabetes mellitus (DM), hypertension, chronic glomerulonephritis (GN), chronic pyelonephritis, schistosomal obstructive uropathy, and schistosomal nephropathy.[2]

Recent advances in genome-wide association studies of kidney disease resulted in the discovery of several genes associated with the development of ESRD. Among these genes is uromodulin (UMOD) gene.[3]

The human UMOD gene is located on chromosome 16 and encodes for UMOD, which is a glycoprotein exclusively produced in the thick ascending loop of Henle and distal convoluted tubules in the kidney and secreted in the urine.[4]

The main function of UMOD in the kidneys is debatable. It is suggested that it plays a role in the innate immunity through binding to immunoglobulin G and complement and tumor necrosis factor alpha. In vitro studies have demonstrated that animal injections with UMOD resulted in cellular immune response and tubulointerstitial nephritis.[5] This was attributed to the recruitment of immune cells. Another study proposed a protective role for UMOD in animal studies of ischemic reperfusion injury.[6] There is evidence that mutations in the gene coding UMOD lead to improper configuration of this glycoprotein, which results in its polymerization in the tubular cells with accelerated tubular cell death and loss of the nephrons with progressive kidney diseases, leading to renal failure.[7],[8] UMOD mutations are associated with a defect in the urinary concentration, salt wasting, hyperuricemia, gout, hypertension, and ESRD.[9]

The genetic studies of single-nucleotide poly-morphisms (SNPs) of UMOD gene revealed that polymorphisms in the regions rs12917707 and rs42993393 were associated with chronic kidney disease.[10],[11],[12]

There is evidence that specific SNPs in UMOD gene lead to overexpression of UMOD which is associated with ESRD.[13]

There are several studies about the association of UMOD gene polymorphism with ESRDs of various etiologies.[3],[14] However, to the best of our knowledge, there are no such studies on Egyptian patients.

The objectives of the present study were to determine the prevalence of UMOD rs42993393 T>C in Egyptian patients with ESRD and to determine the blood level of UMOD in those patients in comparison to normal population.

 Material and Method



The study was a case–control study that included 100 patients with ESRD on regular chronic hemodialysis (HD) and 100 healthy control subjects. The patients were recruited from Mansoura Nephrology and Dialysis Unit from March 2018 till March 2019. The study was approved by Mansoura Ethical Committee, and the approval was obtained from each participant.

Each subject was evaluated for clinical history and complete medical examination. Ten milliliters of blood sample was withdrawn under complete sterile conditions. The blood sample was divided into three aliquots; one was used for the determination of blood levels of sodium, potassium, creatinine, urea, blood urea nitrogen, calcium, and uric acid by autoanalyzer Dialab480, and the remaining sera were kept frozen at -20°C for the determination of blood UMOD level by enzyme-linked immunosorbent assay (ELISA-Euroimmun AG, Lübeck, Germany). The second aliquot was overlaid on EDTA for complete blood counts with Sysmex. The third aliquot was used for genomic DNA separation from whole blood for molecular study.

Polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP) was used for the determination of UMOD rs42993393 T>C genotype.

DNA extraction from blood

DNA from the blood samples was extracted by the use of QIAamp DNA Blood Mini Kit extraction kit (Qiagen-Hilden-Germany), according to the manufacturers’ protocol.

PCR-RFLP

The primers used for the amplification were forward primer 5/-GTGCAAATTTATTTCG CCTCCA-/3 and reverse primer 5/-GGACTACCTTCTGGTTCTGACTTTCA-/3’. The used amplification mixture was supplied from Qiagen. The following amplification cycles were used: 30 cycles with the following cycle parameters: 95°C for 1 min, annealing at 59°C for 30 sec, followed by extension at 72°C for 30 sec, and final elongation at 72°C for 10 min.

SNP was analyzed with RFLP using Msp1 restriction enzyme (New England BioLab Inc., USA). Msp1 specifically cut at the CˇCGG to produce two products of size 87 base pair (bp) and 27 bp, which were resolved in 2% agarose gel along with 100 bp DNA ladder and visualized by ethidium bromide staining. The data obtained from RFLP were further confirmed by nucleotide sequencing (Applied Biosciences, Germany).[3]

 Statistical Analysis



Statistical analysis was carried out by the use of IBM Statistics version 22.0 (IBM Corp., Armonk, NY, USA). Numerical data are presented as mean ± standard deviation for normally distributed values. Differences between the groups were analyzed by ANOVA. All results were considered significant if P <0.05.

 Results



The study included 100 chronic HD patients and 100 healthy controls. The age of the patients was significantly older than control subjects (50.8 ± 7.9, 45.8 ± 8.1, respectively, P = 0.0001). The patients were mainly males (61%). The duration of dialysis ranges from one month up to 180 months. The etiology of ESRD was attributed mainly to DM (32%) and combined hypertension and DM (22%). The UMOD level had significantly reduced serum level in patients (38.6±7.6 ng/mL) compared to control subjects (221.3±54.2, P = 0.0001) [Table 1].{Table 1}

In the study of UMOD rs42993393 T>C, there were a statistically significant increase in TC in patients [28%, odds ratio (OR) 1.3–1.0–2.0] compared to controls (22%, P = 0.03) and a significant increase in CC in patients (10%) compared to control subjects (3%), P = 0.0001. The T allele was significantly increased in controls compared to patients with a significant increase in C allele in patients compared to controls (P = 0.01), [Table 2].{Table 2}

 Discussion



In the present study, there was a significant reduction of serum UMOD level in patients with ESRD compared to control subjects. This finding was similar to the previous reports by Lvet al, Leihereret al, and Steubl et al.[15],[16],[17] UMOD is mainly secreted from renal tubular epithelial cells and excreted to urine and minor fraction of it is released from basolateral side to tubulointerstitium and detected in the blood.[18],[19] The decline in the serum level of UMOD in patients with ESRD reflects the reduction of functional nephron mass and/or reserve of the tubules.[20],[21] Therefore, the decline in the serum UMOD indirectly reflected abnormalities in renal tubulo-interstitial function, which is associated with a reduction in erythropoietin production, acid–base homeostasis disequilibrium and mineral metabolism disorder, which therefore links the progress on kidney function, which reflects the usefulness of the use of UMOD as an independent marker of kidney function.[22]

The SNPs in the promoter region of UMOD have been linked either to decline in the occurrence of chronic kidney failure or to the development of chronic renal failure and is associated with greater secretion of UMOD.[13],[23]

There were a statistically significant decrease of TT in patients [62%, OR (confidence interval 95%), 1.8 (10–3.3), P = 0.03], compared to controls (75%, P = 0.03), a significant increase in TC in patients (28%, OR 1.3–1.0–2.0) compared to controls (22%, P = 0.03), and a significant increase in CC in patients (10%) compared to control subjects (3%), P = 0.0001. The T allele was significantly increased in controls compared to patients with significant increase in C allele in patients compared to controls (P = 0.01). These findings suggest that there is a link between C allele and genotype with C and risk of ESRD. These findings were similar to a previous study conducted on patients with diabetic nephropathy on Indian patients.[3] On the contrary, previous studies have shown a link between TT genotype and increase creatinine with age and reduced estimated glomerular filtration rate with increased secretion of UMOD that precedes the development of chronic renal failure.[12],[14] The association of mutations in UMOD gene with renal failure may be linked not only to increased UMOD production but also to misfolding of the UMOD molecule, with the abnormal UMOD becoming entrapped in the end of cytoplasmatic reticulum of the cells of the thick ascending limb of the loop of Henle.[24],[25] This may be the explanation for the insignificant difference in the serum level of UMOD with different genotypes in the patients.

We recognize a number of limitations to our study. First, this study was a single-center study with a small sample size, and multicenter larger studies are necessary to confirm our conclusions. Second, we studied only the polymorphism of rs42993393 and extended studies with multiple genetic polymorphisms are essential to find the link between UMOD gene polymorphism and ESRD in Egyptian patients.

In conclusion, the present study highlights the prevalence of UMOD gene polymorphism at rs42993393 T>C. There was a significant prevalence of C allele and C genotypes in patients with ESRD. This finding can be explained by the observation that this allele may be a predisposing genotype for renal failure in susceptible patients. The serum UMOD was significantly reduced in patients with ESRD, which may be attributed to the reduction of functioning renal mass. There was an insignificant association with UMOD level with any genotypes in the patients.

Conflict of interest: None declared.

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