Elevated serum β₂-GPI-Lp(a) complexes levels in children with nephrotic syndrome

Abstract

Background: The complexes of β₂-glycoprotein I (β₂-GPI) with lipoprotein(a) [β₂-GPI-Lp(a)] exist in human circulation and are increased in serum from patients with some autoimmune diseases. This study aims to investigate the concentration of β₂-GPI-Lp(a) in serum of children with idiopathic nephrotic syndrome (NS) and its relationship with serum lipids, oxidized lipoprotein and renal function parameters to explore the potential of the complexes as an additional marker for evaluating pediatric NS.

Methods: Serum concentrations of β₂-GPI-Lp(a) complexes and oxidized Lp(a) [ox-Lp(a)] were measured by "Sandwich" ELISAs in 80 NS children and 82 age/sex-matched healthy controls. The levels of serum lipids and kidney parameters were also determined. Multivariate logistic regression analysis was performed to identify correlate of β₂-GPI-Lp(a) and NS.

Results: The serum concentrations of β₂-GPI-Lp(a) complexes in children with NS were significantly higher than those in controls (median 0.95 U/ml vs 0.28 U/ml, P<0.0001). Ox-Lp(a) levels were also markedly elevated (median 14.55 mg/l vs 2.60 mg/l, P<0.0001] in NS children. The concentrations of β₂-GPI-Lp(a) were positively correlated with ox-Lp(a) (r=0.246, P=0.028), but not with Lp(a) level, and the concentrations of ox-Lp(a) were positively related with Lp(a) (r=0.301, P=0.007) in NS children. Multivariate logistic regression analysis identified a positive association between NS and β₂-GPI-Lp(a) (OR=13.694, 95% CI 6.400-29.299, P<0.0001), after adjusting for kidney function parameters, serum lipids and ox-Lp(a).

Conclusions: Elevated β₂-GPI-Lp(a) level was an independent and significant risk factor for pediatric NS and, enhanced Lp(a) oxidation partly contributes to the formation of β₂-GPI-Lp(a) complexes.