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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 31  |  Issue : 2  |  Page : 664-670

Effect of zinc supplementation on serum zinc and leptin levels in children on regular hemodialysis


1 Department of Pediatrics, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Biochemistry, Faculty of Medicine, Menoufia University, Menoufia, Egypt
3 Department of Pediatrics, Shebin El Kowm Teaching Hospital, Menoufia, Egypt

Date of Submission23-Oct-2016
Date of Acceptance21-Dec-2016
Date of Web Publication27-Aug-2018

Correspondence Address:
Asmaa M El-Sayed Saad
Meet Khakan Shebin Elkowm, El Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.239739

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  Abstract 


Objective
The aim of this study was to determine the effect of zinc supplementation on serum levels of zinc and leptin in pediatric patients on hemodialysis (HD).
Background
Zinc is an essential trace element for human nutrition, and its deficiency which could result in anorexia, poor nutritional status, high rates of infections, and growth retardation. Many patients on maintenance HD exhibit zinc deficiency. Leptin may offer a tool for making clear the physiology of zinc deficiency–induced anorexia based on a relationship between zinc and leptin levels.
Patient and methods
The study was carried out on 42 children divided into two groups: group I included 22 children on HD who received 50-mg zinc gluconate twice daily for 90 days, and group II included healthy children as controls. Anthropometric measurements were taken, and serum zinc and leptin levels were determined the day before supplementation and at day 90 of the study.
Results
Serum level of zinc is decreased and serum leptin level is increased in children on regular HD. There is an increase in zinc level and a decrease in serum leptin level after zinc supplementation.
Conclusion
Zinc supplementation increased serum zinc level and decreased serum leptin level among males and females in the studied patients. Enhancement of serum zinc level improves appetite and stimulate food intake.

Keywords: hemodialysis, leptin, pediatrics, supplementation, zinc


How to cite this article:
El-Mashad GM, El-Gebally ESI, El-Hefnawy SM, El-Sayed Saad AM. Effect of zinc supplementation on serum zinc and leptin levels in children on regular hemodialysis. Menoufia Med J 2018;31:664-70

How to cite this URL:
El-Mashad GM, El-Gebally ESI, El-Hefnawy SM, El-Sayed Saad AM. Effect of zinc supplementation on serum zinc and leptin levels in children on regular hemodialysis. Menoufia Med J [serial online] 2018 [cited 2018 Nov 20];31:664-70. Available from: http://www.mmj.eg.net/text.asp?2018/31/2/664/239739




  Introduction Top


Zinc is an essential trace element for human nutrition and is important for several bodily functions such as vision, cognition, cell reproduction, growth, and immunity. It plays a vital role in metabolism, particularly as a cofactor of many enzymes that are required for natural metabolic processes [1].

Zinc-deficient status is associated with immune system disturbances, poor nutritional status, high rates of infections, and growth retardation [2].

In chronic renal failure, derangements in zinc homeostasis may be found owing to altered protein metabolism, malabsorption of microelements in the gastrointestinal tract, disturbed renal excretion, and expected faulty cellular and tissue distribution [3].

Hemodialysis (HD) is one of the three replacement therapies in renal failure (the other two being renal transplant and peritoneal dialysis) [4].

Many studies have shown that patients on maintenance HD exhibit zinc deficiency, which could result in anorexia [5].

Leptin hormone may offer a tool for making clear the physiology of zinc deficiency–induced anorexia according to relationship between zinc and leptin levels [6].

Leptin is an important immunoregulatory hormone as it enhances a number of immune responses, including macrophage effector functions [7].

Leptin is a key hormone in the regulation of body weight and nutrition [8].


  Aim Top


The aim of this study was to determine the effects of zinc supplementation on serum zinc and leptin levels in patients with end-stage renal disease (ESRD) on regular HD.


  Patients and Methods Top


After approval of the Local Institutional Ethical Committee of Menoufia University Hospital, and obtaining written consents from all patients to participate in our study, this study was carried out in the Pediatric Nephrology Unit, Menoufia University Hospitals, during the period from December 2015 to May 2016.

The study was carried out on 42 children, who were divided into two groups:

Group I included 22 children with ESRD on regular hemodialysis three times per week. It included 10 males and 12 females, ranged from 2 to 18 years of age. Zinc was given to all patients in a dose 50 mg/day for 3 months in the form of zinc gluconate.

All investigations were carried out before starting the HD session at the beginning of the study and after 3 months.

Children with history of malignancy, end-stage liver disease, and gastrointestinal disorder and children candidate for transplantation were excluded from the study.

Group II included 20 healthy children with matched age and sex. They served as a control group.

All patients and controls were subjected to full history taking, focusing on nutritional history and regular drug taking. Anthropometric measures including weight (kg), height (cm), and BMI (kg/m 2) were calculated.

For patient group, predialysis 4-ml venous blood sample was collected under aseptic condition and evacuated in test tubes at room temperature until centrifugation. Serum samples of patient group were divided into two tubes, one for leptin and the other for zinc. The same was done after supplementation.

Serum samples of control group were collected under aseptic conditions and also divided into two tubes, one for zinc and one for leptin.

Determination of serum zinc [9]

The determination of serum zinc level was done by using the colorimetric method with 5-Brom PAPS.

Zinc forms a red chelate complex with 2-(5-brom-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)-phenol. This is measured by the colorimetric method, and the increase of absorbance is proportional to the concentration of total zinc in the sample.

Sample was mixed with the reagent and incubated for 10 min at 25°C. It was measured against reagent blank.



Determination of serum leptin [10]

This was done by using enzyme-linked immune sorbent assay kit (ELISA) based on the sandwich principle. The kit was supplied by Clinilab Company (BDA, Beijing, China).

Principle of the test

This was done using DRG leptin ELISA kit. Leptin kit is a solid-phase ELISA based on the sandwich principle.

The microtiter wells are coated with a monoclonal antibody directed toward a unique antigenic site on a leptin molecule.

Standards, control specimens, and unknowns are incubated in the coated well with a specific biotinylated monoclonal antileptin antibody. A sandwich complex is formed. After incubation, the unbound material is washed off and a steptavidin–peroxidase enzyme complex is added for detection of the bound leptin.

Having added substrate solution, the intensity of color developed is proportional to the concentration of leptin in the patient sample.

Calculation of the average absorbance values for each set of standards, control, and patient samples was done.

Statistical analysis

Data were collected, tabulated, and statistically analyzed using an IBM personal computer with statistical package of the social science (SPSS), version 20 for windows (SPSS Inc., Chicago, Illinois, USA) and MedCalc 13 for windows (MedCalc Software BVBA, Ostend, Belgium), where the following statistics were applied.

Descriptive statistics

In descriptive statistics, quantitative data were presented in the form of mean ± SD and qualitative data were presented in the form of numbers and percentages.

Analytical statistics

The used tests of significance included the following:

χ2, Student's t-test, Mann–Whitney test, paired t-test, Wilcoxon's signed rank test, and Pearson's correlation (r).

P value more than 0.05 was considered statistically nonsignificant.

P s value less than 0.05 was considered statistically significant.

P value less than 0.001 was considered statistically highly significant.


  Results Top


There was no significant difference between patient and control groups regarding age and sex [Table 1].
Table 1: Demographic data of the studied groups

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There was a significant decrease in weight and height centiles in patients than controls [Table 2].
Table 2: Weight and height centile among the studied groups

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The most common causes of renal failure in our patients were obstructive uropathy (36.8%), such as posterior urethral valve and vesicoureteric reflux; followed by chronic glomerulonephritis (18.4%); then congenital anomalies (13.7%) such as polycystic kidney disease – solitary kidney; and then chronic pyelonephritis, unknown causes, and renal osteodystrophy (9%), whereas the least common cause was lupus nephritis (4.5%) [Table 3].
Table 3: Causes of renal failure among the studied patients

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There was a highly statistical significant increase in serum zinc level in the studied patients after zinc supplementation [Table 4].
Table 4: Serum zinc level of the studied patients before and after zinc supplementation

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There was a significant decrease in leptin level in the studied patients after zinc supplementation [Table 5].
Table 5: Serum leptin level of the studied patients before and after zinc supplementation

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There was a statistically significant negative correlation between serum zinc level and serum leptin level and duration of dialysis of studied patients, whereas there was a statistically significant positive correlation between serum zinc level and body weight and BMI, but no statistically significant correlation between serum zinc level and age and height [Table 6].
Table 6: Correlation between serum zinc level and the studied variables after zinc supplementation

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There was a statistically significant negative correlation between serum leptin level and serum zinc, weight, and BMI, but there was no statistically significant correlation between serum leptin level and age, height, and duration of dialysis in the studied patients [Table 7].
Table 7: Correlation between serum leptin level and the studied variables after zinc supplementation

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There was a highly significant decrease in serum zinc level in patients than controls [Figure 1].
Figure 1: Mean zinc level among studied groups.

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There was a significant increase in serum leptin level in patients than controls [Figure 2].
Figure 2: Mean leptin level among studied groups.

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There was a negative correlation between serum zinc level and leptin level before zinc supplementation [Figure 3].
Figure 3: Correlation between serum zinc level and leptin level before zinc supplementation.

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There was a negative correlation between serum zinc level and leptin level after zinc supplementation [Figure 4].
Figure 4: Correlation between serum zinc level and leptin level after zinc supplementation.

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  Discussion Top


Zinc is a relatively abundant trace element that performs a wide variety of functions in the body [11].

Knowledge of the occurrence of zinc deficiency and its importance for human health has increased greatly in recent years [12].

Serum zinc deficiency has been reported in patients with chronic kidney disease (CKD) owing to hypoproteinemia, proteinuria, and tubular reabsorption impairment [13]. During dialysis, some trace elements can accumulate in the body owing to dialysis fluid impurities, whereas others may enter the dialysate from the blood leading to deficiency of some trace elements [14].

In our study, 45.5% of patients on HD had weight below third centile and 50% had height below third centile, which has significant increase compared with control group. Pundziene et al. [15] found that 30.9% children with glomerular filtration rate of less than 60 ml/min/1.73 m 2 and 43.7% with ESRD had heights below the third centile.

This is in agreement with Kretzler and Allred [16], who stated that growth retardation is one of the major complications of children with CKD, which is believed to be multifactorial, including disturbed growth hormone, insulin-like growth factor-I function, nutritional status, acid-base balance, and bone mineralization.

This study shows that the most common cause of renal failure in children was obstructive uropathy, followed by chronic glomerulonephritis, then chronic pyelonephritis, congenital anomalies, and renal osteodystrophy, whereas the least common causes were lupus nephritis and idiopathic causes.

Harambat et al. [17] showed that congenital anomalies of the kidney and urinary tract (48%) were the most common causes of renal failure in pediatric patients followed by hereditary nephropathies (10%) and glomerulonephritis (14%).

Gulati and Langman [18] reported that the chief causes of CKD in children include the following: obstructive uropathy, hypoplastic or dysplastic kidney, reflux nephropathy, glomerulonephritis, and polycystic kidney disease.

This disagrees with results that show the principal causes of ESRD were interstitial nephritis (14–32%), glomerulonephritis (11–24%), and diabetes (5–20%) [19].

In this study, before intervention, the mean serum zinc level in the patient group was 60.9 ± 13.4 mg/dl and in control group was 95.0 ± 9.84 mg/dl. So, there was a highly significant decrease in serum zinc level in patient group before supplementation compared with control group.

In Egypt, a study by Shouman et al. [20] included 33 pediatric patients with ESRD on regular HD, three times weekly, and 20 healthy control subjects, and it was conducted in Cairo University Children Hospital. It found that zinc concentration is significantly decreased in patients than controls with inverse correlation to duration of dialysis, and related that to the loss of trace elements during the dialysis procedure, which is in agreement with this study.

The results of the present study showed that serum zinc concentrations after zinc supplementation increase from 60.9 ± 13.4 to 95.0 ± 9.84 mg/dl, which is within a reference range.

This is consistent with previous studies that have stated subnormal serum zinc concentrations in the HD population, with improvements after zinc supplementation [21].

Similar results were found by Guo et al. [22] and Jern et al. [23] who reported improvement of serum zinc level after supplementation in HD patients.

In this study, before intervention, serum leptin level in the supplemented group was 13.4 ± 13.1 ng/dl and in the control group was 5.83 ± 2.19 ng/dl.

Gariboito et al. [24] also reported that there was an increased in serum leptin level in children with CKD under HD, but they failed to explain the mechanism which causes this disturbance.

The rate of leptin clearance from serum determines leptin level. Impairment of glomerular filtration in patients with renal insufficiency may lead to increase in leptin level, which may cause loss of appetite and protein energy malnutrition in patients with renal insufficiency [25].

Although not all patients with CKD have elevated serum leptin levels as reported in some studies, a significant elevation is noted when such levels are adequately corrected for body fat mass and age [26].

The result of our study showed that mean serum leptin level in patients was 6.04 ± 7.94 ng/ml after zinc supplementation, so there was a significant negative correlation between zinc and leptin levels.

These results agree with those of Luciana et al. [27] who showed that low plasma zinc levels are negatively associated with high leptin levels in HD patients.

Relationship between zinc level and plasma leptin in HD patients was also found by Aranha et al. [6] who reported that low plasma zinc levels are negatively associated with high leptin levels in HD patients.

Argani et al. [14] showed that the mean serum leptin was decreased significantly after zinc supplementation, but more studies are needed to clarify the mechanisms by which serum leptin level is influenced as a result of zinc supplementation in HD patients. Mariani et al. [28] presented a hypothesis on zinc supplementation that it may decrease interleukin (IL)-6 and subsequently leptin level. They also reported that zinc supplementation in patients with low or borderline normalizes circulating zinc modulated plasmatic IL-6.

Another study conducted by Trujillo et al. [29] demonstrated that IL-6 has multiple effects in human adipose tissue and most importantly IL-6 could increase leptin production. Therefore, decreasing IL-6 with zinc supplementation may reduce leptin level.

This is in agreement with Aness et al. [30] who found that the duration of HD had a negative correlation with serum zinc level.

This agrees with the results founds by Esfahani et al. [31] who showed that long-term HD leads to abnormalities of some trace elements in children, and derangements increase with duration of HD, and that there was a linear relation between the period of dialysis and serum level of zinc.

This study showed that there was no statistically significant correlation between leptin level and duration of dialysis.

Merabet et al. [32] found no correlation between leptin levels and the number of years patients had been on dialysis or with recent weight changes. Also, they concluded that leptin is increased in patients with ESRD, but it does not appear to cause decreased weight as leptin level did not correlate with residual renal function.

In our study, weight and BMI showed improvement after zinc supplementation The weight increased from 37.4 ± 14.2 to 38.1 ± 14.4 kg and BMI from 19.3 ± 3.94 to 19.5 ± 3.97 kg/m 2.

Zinc deficiency is associated with decreased food intake and has been observed in patients with CDK. Leptin is an anorexigenic peptide, and patients with CKD present generally high levels of this hormone [33].

This result agrees with the study done by Ohinata et al. [34] who reported that oral zinc supplementation improves appetite and stimulates food intake. Similar results were found by Sahin et al. [35] who stated that zinc supplement to the diets of HD patients may be of value to prevent malnutrition. Also, this result agrees with the results of Friedman [36] that showed as plasma leptin levels decrease, it stimulates appetite and suppresses energy expenditure until fat mass is restored.


  Conclusion Top


Serum zinc level is low and serum leptin level is high in patients with CKD whether under either conservative or dialysis treatment.

Zinc supplementation increases serum zinc and decrease serum leptin levels among males and females in the studied patients. Improvement of serum zinc level improves appetite and stimulate food intake.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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