Background:  Reactive oxygen species and cytokines are reported to play a role in the proteinuria of nephrotic syndrome. The aim of this study was to investigate indirect evidence of oxidant activity together with leptin, lipoproteins and pro‐inflammatory cytokines in children with steroid‐sensitive nephrotic syndrome.

Methods:  A total of 40 children with steroid‐sensitive nephrotic syndrome (20 with newly onset or relapse comprised group I and 20 in remission while receiving steroids comprised group II) and 20 sex and age matched healthy control children were included. The following indirect parameters of oxidant activity were determined: serum malondialdehyde, erythrocyte superoxide dismutase, catalase and whole‐blood‐reduced glutathione. Serum leptin, lipids and lipoproteins were also determined.

Results:  Similar glutathione, increased malondialdehyde levels and decreased superoxide dismutase and catalase activity were observed in group I patients compared with controls. There was no significant difference in these variables between group I and group II (P > 0.05). Tumour necrosis factor‐alpha and interleukin‐6 concentrations were similar in patients and controls. Concentrations of interleukin‐1beta and interleukin‐8 were higher in the active phase of nephrotics compared with controls (P < 0.05). Significant positive correlations were found between malondialdehyde and interleukin‐1beta, interleukin‐6, leptin and lipoprotein (a) (P < 0.05). There were significant negative correlations between anti‐oxidants and leptin, lipoprotein (a) and several cytokines (P < 0.05).

Conclusions:  Changes in the concentrations of malondialdehyde, superoxide dismutase, catalase and glutathione are compatible with increased amounts of oxidation in steroid‐sensitive nephrotic syndrome. Leptin and pro‐inflammatory cytokines may be related to excessive protein permeability in nephrotic syndrome.