Urinary protein expression patterns in children with sleep-disordered breathing: preliminary findings

Obstructive sleep apnea (OSA) is the most common form of sleep-disordered breathing, with almost 15 million Americans affected and many more at risk. Current diagnostic approach to OSA requires polysomnography, which is laborious, onerous, and time-consuming. There is ample evidence that inflammatory responses to the perturbations associated with OSA trigger a variety of genes and signaling cascades that ultimately lead to end-organ injury and changes in kidney function and protein expression. The aim of this study was therefore to analyze proteins in human urine and assess whether differential expression of particular proteins is associated with the presence of OSA.

Eleven OSA and 11 control children between the ages of three and 14 (males=17; females=5) underwent overnight sleep studies followed by a first-morning urine sample. Proteomic analysis of urine samples yielded a unique map of proteins, of which, five spots were selected for further analysis due to their significant intensity differences between OSA and control groups.

Mass spectrometry followed by peptide mass fingerprinting conclusively identified four of the five spots as gelsolin, perlecan (a heparan sulfate proteoglycan), albumin, and immunoglobulin (P<0.05 and protein scores>67).

Overall, increased expression of gelsolin and perlecan in the urinary proteome of children with OSA suggests that the episodic hypoxia associated with OSA may lead to changes in protein permeability or alternatively to increased catabolism of these proteins and their excretion in urine.