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J Clin Res Pediatr Endocrinol. 2018 Aug 17. doi: 10.4274/jcrpe.0046. [Epub ahead of print]

Evaluation of Renal Function in Obese Children and Adolescents Based on Serum Cystatin C, Estimated Glomerular Filtration Rate Formulas, and Proteinuria: Which is Most Useful?

Author information

1
Ankara University Faculty of Medicine, Departmnt of Pediatrics, Ankara, Turkey
2
Ankara University Faculty of Medicine, Departmnt of Pediatric Endocrinology, Ankara, Turkey
3
Ankara University Faculty of Medicine, Departmnt of Pediatric Nephrology, Ankara, Turkey

Abstract

Background:

There is growing interest in the relationship between obesity and renal damage. The effect of obesity on renal function in children and adolescents has not been adequately investigated. In addition, there is no complete consensus on the reliability of renal function parameters and which of these accurately estimate true renal function. The primary goal of this study was to evaluate renal function in obese children and adolescents using glomerular filtration rate (GFR), cystatin C, and creatinine (Cr)-derived formulas. We also compared classical GFR measurement methods with methods based on bioimpedance analysis-derived body cell mass (BCM).

Subjects and Methods:

We enrolled 108 obese and 46 healthy subjects aged 6–18 years. Serum cystatin C, serum creatinine, 24-hour proteinuria, creatinine clearance (CrCl), and GFR were evaluated in both groups. Estimated GFR was measured with creatinine-based, cystatin C-based, combined (cystatin C and creatinine), and BCM-based formulas. Both actual and fat-free mass body surface areas were used when required. Metabolic parameters (blood glucose, insulin, and lipids) were analyzed in the obese subjects, and International Diabetes Federation criteria were used to identify metabolic syndrome (MetS).

Results:

We did not detect statistically significant differences between the obese and control groups for mean creatinine (p=0.658) and mean cystatin C (p=0.126). Mean cystatin C levels of MetS patients were significantly higher than in non-MetS obese participants. Creatinine-based GFR measurements, BCM-based measurements, and a combined creatinine and cystatin C measurement showed a statistically significant increase in the GFR of obese subjects compared to controls. This increase was negatively correlated with duration of obesity. Estimations also did not differ based on actual or fat-free mass body surface area. Only the Filler equation showed a statistically significant decrease in eGFR in MetS patients. There were no statistically significant differences between the obese and control groups for proteinuria (p=0.994) and fat-free mass proteinuria (p=0.476).

Conclusion:

We conclude that cystatin C could be used as an earlier biomarker than creatinine in the detection of impaired renal function in obese children, especially those with MetS. Creatinine-based formulas represent hyperfiltration as the first difference in renal function. Decreasing eGFR seen with cystatin C-based formulas in MetS patients but not creatinine-based formulas may represent the early stages of renal damage. Using fat-free mass or BCM for eGFR formulas in obese children seems to provide no additional information.

KEYWORDS:

Obesity; glomerular filtration rate; body cell mass; cystatin C

PMID:
30145854
DOI:
10.4274/jcrpe.0046
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