title: Time-course human urine proteomics in space-flight simulation experiments.
abstract: BACKGROUND
  Long-term space travel simulation experiments enabled to discover different aspects of human metabolism such as the complexity of NaCl salt balance. Detailed proteomics data were collected during the Mars105 isolation experiment enabling a deeper insight into the molecular processes involved.
  
  
  RESULTS
  We studied the abundance of about two thousand proteins extracted from urine samples of six volunteers collected weekly during a 105-day isolation experiment under controlled dietary conditions including progressive reduction of salt consumption. Machine learning using Self Organizing maps (SOM) in combination with different analysis tools was applied to describe the time trajectories of protein abundance in urine. The method enables a personalized and intuitive view on the physiological state of the volunteers. The abundance of more than one half of the proteins measured clearly changes in the course of the experiment. The trajectory splits roughly into three time ranges, an early (week 1-6), an intermediate (week 7-11) and a late one (week 12-15). Regulatory modes associated with distinct biological processes were identified using previous knowledge by applying enrichment and pathway flow analysis. Early protein activation modes can be related to immune response and inflammatory processes, activation at intermediate times to developmental and proliferative processes and late activations to stress and responses to chemicals.
  
  
  CONCLUSIONS
  The protein abundance profiles support previous results about alternative mechanisms of salt storage in an osmotically inactive form. We hypothesize that reduced NaCl consumption of about 6 g/day presumably will reduce or even prevent the activation of inflammatory processes observed in the early time range of isolation. SOM machine learning in combination with analysis methods of class discovery and functional annotation enable the straightforward analysis of complex proteomics data sets generated by means of mass spectrometry.
authors.forename: Hans
authors.initials: H
authors.lastname: Binder
authors.forename: Henry
authors.initials: H
authors.lastname: Wirth
authors.forename: Arsen
authors.initials: A
authors.lastname: Arakelyan
authors.forename: Kathrin
authors.initials: K
authors.lastname: Lembcke
authors.forename: Evgeny S
authors.initials: ES
authors.lastname: Tiys
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Ivanisenko
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Kolchanov
authors.forename: Alexey
authors.initials: A
authors.lastname: Kononikhin
authors.forename: Igor
authors.initials: I
authors.lastname: Popov
authors.forename: Evgeny N
authors.initials: EN
authors.lastname: Nikolaev
authors.forename: Lyudmila
authors.initials: L
authors.lastname: Pastushkova
authors.forename: Irina M
authors.initials: IM
authors.lastname: Larina
mesh_terms: D000328:Adult; D001185:Artificial Intelligence; D018480:Astronauts; D003198:Computer Simulation; D006801:Humans; D008297:Male; D020543:Proteome / Q000032:analysis*; D040901:Proteomics; D013026:Space Flight; D014556:Urine
chemical_list: D020543:Proteome