Comparison of the urinary protein patterns of athletes by 2D-gel electrophoresis and mass spectrometry-a pilot study.

Urinary proteins and exercise-induced proteinuria have been the subject of much research. Proteinuria has been studied in depth after different running and cycling intensities and durations and the different mechanisms of glomerular filtration and tubular dysfunction have been elucidated. The present study was carried out to compare urinary protein profiles of athletes in different sport categories (endurance sport, team sport, strength sport). Doping-control urine samples obtained from in-competition testing and specimens derived from a control group were analysed by means of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and significantly deviating protein spots were enzymatically hydrolysed and identified by nanoflow liquid chromatography-orbitrap mass spectrometry. Endurance sport samples demonstrated a significant increase of mainly medium-sized urinary proteins such as transferrin, zinc alpha-2-glycoprotein and prostaglandin H2 D-isomerase (30-80 kDa) in 2D-PAGE experiments. Proteinuria was evident in all samples after protein concentration measurements (protein/creatinine > 15 mg/mmol). Alterations were also observed in strength sport samples, which showed an increase of low molecular weight proteins or protein fragments (<30 kDa, e.g., transthyretin, CD 59 antigen or an N-terminal transferrin fragment). In contrast, the concentration measurements did not imply proteinuria but total protein excretion was in a normal range. The study provides a first overview on 2D maps of the urinary proteome after different types of exercise. Future studies may lead to the establishment of urinary protein maps that are typical for a certain type of sport or even an individual athlete. These maps may complement the blood passport of athletes in doping control.