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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE  
Year : 2021  |  Volume : 32  |  Issue : 5  |  Page : 1340-1347
Urinary pigment epithelium-derived factor as a marker of diabetic nephropathy in Egyptian patients with type 2 diabetes mellitus


1 Department of Internal Medicine, Nephrology Unit, School of Medicine, Cairo University, Cairo, Egypt
2 Department of Internal Medicine, Endocrinology Unit, School of Medicine, Cairo University, Cairo, Egypt
3 Department of Chemical Pathology, School of Medicine, Cairo University, Cairo, Egypt

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Date of Web Publication4-May-2022
 

   Abstract 


Diabetic nephropathy (DN) is the most common cause of end-stage renal disease. Urinary pigment epithelium-derived factor (PEDF) has also been shown to suppress the expression of fibrogenic, pro-inflammatory, and angiogenic factors, thus contributing to pathological changes in early DN. We aimed to study the role of urinary PEDF as a biomarker for the detection of chronic kidney disease progression in patients with type 2 diabetes mellitus (T2DM). Sixty patients with T2DM were recruited in addition to 20 nondiabetic healthy volunteers. Urinary PEDF using enzyme-linked immunoassay technique was performed to all subjects, and correlations between it and different clinical parameters were examined. Our study showed a statistically significant correlation between urinary PEDF level and duration of DM (P <0.001), glycosylated hemoglobin (P <0.001), serum creatinine (P <0.001), urinary albumin-to-creatinine ratio (P <0.001), and stage of diabetic retinopathy by fundus examination (P <0.001). Urinary PEDF is a good indicator of progression of DN and microvascular damage (as a complication of diabetes) in general. It was also increased in case of poor diabetic control.

How to cite this article:
Fayed A, Rabiee A, El-Saadany O, Shaban M, Hesham D, Elghobary H, Hammad H, Fatthy M. Urinary pigment epithelium-derived factor as a marker of diabetic nephropathy in Egyptian patients with type 2 diabetes mellitus. Saudi J Kidney Dis Transpl 2021;32:1340-7

How to cite this URL:
Fayed A, Rabiee A, El-Saadany O, Shaban M, Hesham D, Elghobary H, Hammad H, Fatthy M. Urinary pigment epithelium-derived factor as a marker of diabetic nephropathy in Egyptian patients with type 2 diabetes mellitus. Saudi J Kidney Dis Transpl [serial online] 2021 [cited 2022 May 25];32:1340-7. Available from: https://www.sjkdt.org/text.asp?2021/32/5/1340/344753



   Introduction Top


Diabetic nephropathy (DN) is the most common cause of end-stage renal disease (ESRD). It accounts for 54% of all renal failure patients requiring chronic dialysis.[1] Early detection can ensure timely intervention and improvement of treatment outcome. Thus far, microalbuminuria (MA) has been recognized as an early indicator of DN; however, the presence of albuminuria might not be always indicative of DN in individuals with type 2 diabetes mellitus (T2DM), as revealed by biopsy studies.[2] In fact, MA is a marker for endothelial dysfunction. MA may develop because of hypertension or/and insulin resistance,[3] along with hyperglycemia, and the presence of MA in T2DM patients may also be indicative of cardiovascular disease.

Therefore, there is a need to identify new sensitive and specific markers for screening and assessing incipient DN and monitoring responses to therapy. Identification of novel biomarkers implicated in DN may enable early detection of patients at risk of clinical disease progression, especially before a significant reduction in glomerular filtration rate (GFR) or the development of microalbuminuria.[4]

Pigment epithelium-derived factor, a member of the serine protease inhibitor (serpin) gene family, is a 50 KDa glycoprotein first identified in the conditioned medium of human retinal pigment epithelial cells as a neurotrophic factor and a potent angiogenic inhibitor.[5] Cell-based and animal studies have suggested pigment epithelium-derived factor (PEDF) to be a local protective factor against diabetic microvascular damage.[6] Decreased PEDF protein and mRNA expression have been found in kidneys of diabetic mice.[7] PEDF has also been shown to suppress the expression of fibrogenic,[8] pro-inflammatory, and angiogenic factors,[9] thus contributing to pathological changes in early DN.[10]

In the current study, we aimed to examine the role of urinary PEDF as a biomarker for the detection of chronic kidney disease (CKD) progression in patients with T2DM.


   Patient and Methods Top


Kasr Al-Ainy Hospital is a major hospital and a tertiary referral center serving patients from Cairo and also patients referred from all other governorates of Egypt. Sixty patients with T2DM were recruited from the outpatient endocrinology clinic, nephrology clinic, and internal medicine departments during August 2016 to December 2018; This study also included 20 nondiabetic healthy people who were age and sex matched as controls.

The WHO classification is used to diagnose diabetes.At least five years from the diagnosis of type 2 diabetes was required to be included in our study. Exclusion criteria included type 1 diabetes, ESRD patients on regular hemodialysis, cirrhotic patients, Child B and C, patients on either angiotensin-con-verting enzyme (ACE) inhibitors or angio-tensin II receptor blocker, pregnant females, the presence of infections, and symptoms or signs of other systemic diseases.

After discussing the procedure with each patient separately, written consent was obtained. All our patients were subjected to full history through clinical examination. The weight of each participant was measured using a digital scale while the participant was lightly clothed with bare feet. Each participant’s height was measured while they were barefoot., and the body mass index (BMI) was calculated as body weight in kg divided by height square in meters (kg/m2). The waist circumference was measured midway between rib margin and the iliac crest in a standing position by the same examiner. The blood pressure (BP) was measured using mercury sphygmomanometer; two measurements were made, and the average was calculated.. Hypertension was diagnosed for any patient taking antihypertensive agents or his BP >140/90 mm Hg on two separate measurements on two different occasions. Fundus examination was performed to all participants using direct ophthalmoscopy, and results were classified according to international clinical diabetic retinopathy and diabetic macula edema disease severity scales.[11] Abdominal ultrasonography was done using Siemens Acuson X300 device, with a convex 2D probe with frequency of 2.5–4.5 MHz after proper preparation of the patients, to assess the size and echogenicity of both kidneys, and the presence of liver cirrhosis.

Laboratory investigations included routine laboratory investigations including complete blood count, fasting plasma glucose, glycosylated hemoglobin (HbA1c), and serum levels of total proteins and albumin, renal function [creatinine and blood urea nitrogen and estimated GFR (eGFR)] according to the Modification of Diet in Renal Disease equation, random urine sample for testing for albumin/creatinine ratio (A/C ratio) repeated twice three months apart if the first sample was positive for microalbuminuria (MA), patients had been instructed to refrain from heavy exercise 24 h before the test, virology including hepatitis B virus surface antigen, hepatitis C virus antibody and human immunodeficiency virus antibody using (enzyme-linked immunoassay) ELISA technique and urinary PEDF by ELISA based on the biotin double antibody sandwich technology (add PEDF to the wells, which are precoated with PEDF monoclonal antibody, and then incubate, after that, add anti-PEDF antibodies labeled with biotin to unite with streptavidin-HRP, which forms immune complex. Remove unbound enzymes after incubation and washing. Add substrate A and B. Then, the solution will turn blue and change into yellow with the effect of acid. The shades of solution and the concentration of human PEDF are positively correlated).


   Statistical Analysis Top


Precoded data were entered on the computer using Microsoft Office Excel Software program (2010) for Windows. Data were then transferred to the IBM SPSS Statistics software program version 25.0 (IBM Corp., Armonk, NY, USA) to be statistically analyzed. Continuous variables are expressed as mean ± standard deviation. Frequency and percentage were done for qualitative variables. Comparisons between quantitative variables were done using the nonparametric Kruskal–Wallis and Mann–Whitney tests.[12] For comparing categorical data, Chi-square (χ2) test was performed. Exact test was used instead when the expected frequency is <5.[13] Correlations between quantitative variables were done using Spearman correlation coefficient.[14] P <0.05 was considered statistically significant; graphs were used to illustrate some information.


   Results Top


The present study included 80 subjects, 60 of which were diabetic patients (32 males and 28 females) and 20 were healthy control subjects (11 males and 9 females). Patients in our study were of average age (59.53 ± 10.52 years in the diabetic group and 47.30 ± 17.02 years in the control group). Diabetic group members had higher BMI (28.61 ± 4.89) compared to that of the control group (23.74 ± 4.34). Most of the diabetic group members were hypertensive [38 patients (63.3%)]. The average duration of diabetes in the diabetic group was 9.58 ± 5.54 years. Most of the diabetic patients were anemic. They had elevated serum creatinine (2.22 ± 1.77 mg/dL) and albuminuria (about 1 g in average). Diabetes in the diabetic group was not very well controlled (average HbAiC = 7.65% ± 1.24%). The laboratory results of the studied groups are discussed in [Table 1]. [Figure 1] shows the correlation between duration of DM and urinary A/C ratio. [Figure 2] shows that the urinary PEDF level is significantly higher in the diabetic group than the control group.
Table 1: Laboratory results of studied groups.

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Figure 1: Correlation between duration of diabetes mellitus and urinary albumin-to-creatinine ratio.
A/C ratio: Albumin-to-creatinine ratio, DM: Diabetes mellitus.


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Figure 2: Comparison between urinary pigment epithelium-derived factor level in both diabetic and control groups.
PEDF: Pigment epithelium-derived factor.


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[Table 2] shows the correlation between PEDF level and different parameters in the diabetic group. There was a positive correlation between urinary PEDF level and age (P = 0.192), duration of DM (P <0.001), HbA1C (P <0.001), serum creatinine (P <0.001), serum urea (P <0.001) in addition to urinary A/C ratio (P <0.001) [Figure 3]. There was a negative correlation between PEDF level and serum hemoglobin (P = 0.826), GFR (P <0.001), serum potassium (P = 0.839) in addition to serum albumin (P <0.001).
Table 2: Correlation between PEDF level and other parameters in the diabetic group.

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Figure 3: Correlation between pigment epithelium-derived factor (PEDF) level with urinary albumin-tocreatinine (A/C) ratio and serum creatinine. (a) Correlation between PEDF level and urinary A/C ratio, (b) Correlation between PEDF level and serum creatinine.

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Fundus examination results in the diabetic group were as follows mild nonproliferative diabetic retinopathy (MNDR) was present in 38 patients (63.3%), severe nonproliferative diabetic retinopathy (SNDR) was present in 12 patients (20%), proliferative diabetic retinopathy (PDR) was present in eight patients (13.3%), while no apparent diabetic retinopathy (NDR) was present in two patients (3.3%). [Figure 4] shows the correlation between A/C ratio and PEDF level with stage of diabetic retinopathy by fundus examination (using independent-samples Kruskal–Wallis test). The more progressive is the stage of diabetic retinopathy by fundus examination, the higher is the A/C ratio value. The more progressive is the stage of diabetic retinopathy by fundus examination, the higher is the PEDF level in urine.
Figure 4: Correlation between pigment epithelium-derived factor (PEDF) level and urinary albumin-tocreatinine (A/C) ratio with stage of diabetic retinopathy by fundus examination (using independentsamples Kruskal–Wallis test). (a) Correlation between A/C ratio and stage of diabetic retinopathy by fundus examination. (b) Correlation between PEDF level and stage of diabetic retinopathy by fundus examination.

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   Discussion Top


Our study showed that PEDF level in urine is significantly higher in the diabetic group than in the control group (P < 0.001). Chen et al in 2010 found the same results.[7] Furthermore, our study showed that urinary PEDF level was positively correlated to duration of DM (r = 0.795, P <0.001), serum creatinine (r = 0.521, P <0.001), and A/C ratio (r = 0.805, P <0.001) and was negatively correlated to GFR (r = −0.511, P <0.001). All these results suggest that urinary PEDF is probably an important determinant of the pathogenesis of DN.

Hui et al in 2014 showed the same results but in correlation with serum PEDF instead of urinary PEDF.[8] From this, we conclude that both serum and urinary PEDFs are equally effective as a marker for progression of DN.

Several studies have suggested that albuminuria can be attributed with confidence to DN, if DN is present. In 2007, KDOQI Clinical Practice Guidelines and Clinical Practice Recommendations for Diabetes and CKD stated that in most patients with diabetes, CKD should be attributable to diabetes if MA is present along with DR.[15] Our study showed that the more progressive is the stage of diabetic retinopathy by fundus examination, the higher is the PEDF level in urine (P <0.001). This further proves that PEDF level is well correlated to progression of DN, and that the presence of high PEDF level denotes the presence of microvascular damage (retinopathy, or nephropathy, etc.).

Furthermore, our study showed that urinary PEDF level is positively correlated to HbA1c level (r = 0.946, P <0.001). Hence, we can conclude that PEDF level is also affected by the degree of diabetic control. The reason for increased urinary PEDF level in T2DM is unclear. It is speculated that there are several reasons behind the increased urinary concentrations of PEDF; (1) hyperfiltration of circulating PEDF because of the increased permeability of the glomerular basement membrane. PEDF is a glycoprotein with a molecular weight of 50 kDa, which is close to albumin with a molecular weight of 65 kDa, and (2) increased production or secretion of PEDF by renal tissues in response to hyperglycemia. This hypothesis could be best confirmed by biopsy studies, but it is very difficult to perform such studies in human beings, but it was performed in mice in 2007.[16]


   Study Limitations Top


First, the study used a cross-sectional design and included a relatively small sample size. Second, there is a paucity of knowledge about the relationship between PEDF levels and kidney disease progression in type 1 diabetes patients, as well as whether PEDF levels are influenced by antiproteinuric medicines, such as ACE inhibitors, or urinary tract infection.


   Conclusion Top


Our study demonstrates that the urinary PEDF is a good marker for progression of DN and microvascular damage – as a complication of diabetes – in general. It can be used instead of or in addition to A/C ratio for follow-up of DN progression.


   Ethical Committee Approval Top


The Local Ethical Committee of the Department of Internal Medicine, School of Medicine, Cairo University, approved this work.


   Informed consent Top


Informed consent was obtained from all individual participants included in the study.

Conflict of interest: None declared.



 
   References Top

1.
Locatelli F, Pozzoni P, Del Vecchio L. Renal replacement therapy in patients with diabetes and end-stage renal disease. J Am Soc Nephrol 2004;15 Suppl 1:S25-9.  Back to cited text no. 1
    
2.
Molitch ME, DeFronzo RA, Franz MJ, et al. Nephropathy in diabetes. Diabetes Care 2004;27 Suppl 1:S79-83.  Back to cited text no. 2
    
3.
Lin CY, Chen MF, Lin LY, Liau CS, Lee YT, Su TC. Insulin resistance is the major determinant for microalbuminuria in severe hypertriglyceridemia: Implication for high-risk stratification. Intern Med 2008;47:1091-7.  Back to cited text no. 3
    
4.
Gerstein HC, Islam S, Anand S, et al. Dysglycaemia and the risk of acute myocardial infarction in multiple ethnic groups: An analysis of 15,780 patients from the INTERHEART study. Diabetologia 2010;53:2509-17.  Back to cited text no. 4
    
5.
Dawson DW, Volpert OV, Gillis P, et al. Pigment epithelium-derived factor: A potent inhibitor of angiogenesis. Science 1999;285: 245-8.  Back to cited text no. 5
    
6.
Boehm BO, Lang G, Volpert O, et al. Low content of the natural ocular anti-angiogenic agent pigment epithelium-derived factor (PEDF) in aqueous humor predicts progression of diabetic retinopathy. Diabetologia 2003;46: 394-400.  Back to cited text no. 6
    
7.
Chen H, Zheng Z, Li R, et al. Urinary pigment epithelium-derived factor as a marker of diabetic nephropathy. Am J Nephrol 2010;32: 47-56.  Back to cited text no. 7
    
8.
Hui E, Yeung CY, Lee PC, et al. Elevated circulating pigment epithelium-derived factor predicts the progression of diabetic nephropathy in patients with type 2 diabetes. J Clin Endocrinol Metab 2014;99:E2169-77.  Back to cited text no. 8
    
9.
Awad AS, Gao T, Gvritishvili A, et al. Protective role of small pigment epithelium-derived factor (PEDF) peptide in diabetic renal injury. Am J Physiol Renal Physiol 2013;305: F891-900.  Back to cited text no. 9
    
10.
Wang JJ, Zhang SX, Mott R, et al. Anti-inflammatory effects of pigment epithelium-derived factor in diabetic nephropathy. Am J Physiol Renal Physiol 2008;294:F1166-73.  Back to cited text no. 10
    
11.
Wilkinson CP, Ferris FL 3rd, Klein RE, et al. Proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. Ophthalmology 2003;110:1677-82.  Back to cited text no. 11
    
12.
Chan YH. Biostatistics 102: Quantitative data – Parametric & non-parametric tests. Singapore Med J 2003;44:391-6.  Back to cited text no. 12
    
13.
Chan YH. Biostatistics 103: Qualitative data – Tests of independence. Singapore Med J 2003. 44:498-503.  Back to cited text no. 13
    
14.
Chan YH. Biostatistics 104: Correlational analysis. Singapore Med J 2003;44:614-9.  Back to cited text no. 14
    
15.
KDOQI. KDOQI clinical practice guidelines and clinical practice recommendations for diabetes and chronic kidney disease. Am Kidney Dis 2007;49:S12-154.  Back to cited text no. 15
    
16.
Sahin K, Onderci M, Tuzcu M, et al. Effect of chromium on carbohydrate and lipid metabolism in a rat model of type 2 diabetes mellitus: The fat-fed, streptozotocin-treated rat. Metabolism 2007;56:1233-40.  Back to cited text no. 16
    

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Correspondence Address:
Ahmed Fayed
Department of Internal Medicine, Nephrology Unit, School of Medicine, Cairo University, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1319-2442.344753

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    Abstract
   Introduction
   Patient and Methods
   Statistical Analysis
   Results
   Discussion
   Study Limitations
   Conclusion
    Ethical Committe...
   Informed consent
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