MEGALIN - A FACULTATIVE MARKER OF OBESITY-RELATED GLOMERULOPATHY IN CHILDREN

Obesity-related glomerulopathy (ORG) is an increasingly detected syndrome present in children with obesity. Megalin, a constitutive proximal tubule cell protein, when present in urine, can be considered as a biomarker indicating renal injury in these children. The aim of the study was to analyze 24-hour urine 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 90 age-matched healthy children. Daily urine megalin excretion, NGAL and AGT concentrations in serum and 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 in normo- 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 in hyper- and hypo-filtering children with obesity. Normofiltering children with obesity (corresponding to individuals with asymptomatic ORG), presented significantly increased uAGT concentration. Elevated sNGAL and uNGAL concentrations are useful for characterization of both hyper- and hypo-filtration states 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.