Megalin - a facultative marker of obesity-related glomerulopathy in children

Abstract

Obesity-related glomerulopathy (ORG) is an increasingly detected syndrome present in children withobesity. Megalin, a constitutive proximal tubule cell protein, when present in urine, can be consideredas a biomarker indicating renal injury in these children. The aim of the study was to analyze 24-hoururine megalin excretion in children with obesity and compare its clinical usefulness to both urine (u)and serum (s) concentrations of neutrophil gelatinase-associated lipocalin (NGAL) and angiotensinogen(AGT). The study group consisted of 112 patients with obesity; the control group was composed of 90age-matched healthy children. Daily urine megalin excretion, NGAL and AGT concentrations in serumand urine were estimated using ELISA assays. Obesity was defined by Body Mass Index (BMI) z score ≥2. GFR was calculated using Filler formula. An increased daily urine megalin excretion was detected innormo- and hypo-filtrating children with obesity (2.1±2.1 mg/kg b.w./24h and 12.4±3.6 mg/kg b.w./24h,respectively). In hyperfiltering children with obesity this excretion was found within control values(1.5±2.1 mg/kg b.w./24 h). sNGAL, uNGAL and uAGT concentrations were significantly increased inhyper- and hypo-filtering children with obesity. Normofiltering children with obesity (corresponding toindividuals with asymptomatic ORG), presented significantly increased uAGT concentration. ElevatedsNGAL and uNGAL concentrations are useful for characterization of both hyper- and hypo-filtrationstates in ORG. An increased daily urine megalin excretion in normofiltrating children with obesity,accompanied by elevated uAGT concentration, may indicate asymptomatic ORG in these children.