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Gravitational Physiology, Aging and Medicine

Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Physiol. | doi: 10.3389/fphys.2018.01956

Galanin and adrenomedullin plasma responses during artificial gravity on a human short-arm centrifuge

 Julia Stroetges1, Charles Laing2, Bernd Johannes1, Edwin Mulder1,  Bianca Brix3,  Andreas Roessler3, Johannes Reichmuth3, Joern Rittweger1, 4* and  Nandu Goswami5*
  • 1Institut für Luft- und Raumfahrtmedizin, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Germany
  • 2Centre for Human and Aerospace Physiological Sciences (CHAPS), King's College London, United Kingdom
  • 3Institute of Physiology, Medical University of Graz, Austria
  • 4Universität zu Köln, Germany
  • 5Medical University of Graz, Austria

Galanin and adrenomedullin plasma responses to head-up tilt and lower body negative pressure had been studied previously. However, to what extent by short-arm human centrifugation (SAHC) affects these responses is not known. In this study, we assessed how the application of variable gradients of accelerations (Δgz) via shifting of the rotation axis during centrifugation affects selected hormonal responses. Specifically, we tested the hypothesis, that cardiovascular modulating hormones such as galanin and adrenomedullin will be higher in non-finishers when compared to finishers during SAHC exposure.
Twenty healthy subjects (10 women and 10 men) were exposed to two g-levels (1gz and 2.4gz at the feet (gz_Feet)) in two positions (axis of rotation placed above the head and axis of rotation placed at the heart’s level). Subjects were categorized as finishers or non-finishers based on whether presyncopal signs developed before protocol completion.
Elevated baseline levels of galanin appeared to predict orthostatic tolerance (p=0.054) and seemed to support good orthostatic tolerance during 1 gz_Feet SAHC (p=0.034). In finishers, 2.4 gz_Feet SAHC was associated with increased galanin levels after centrifugation (p=0.007). For adrenomedullin, the hypothesized increases were observed after centrifugation at 1 gz_Feet (p=0.031), but not at 2.4 gz_Feet, suggesting that other central mechanisms than local distribution of adrenomedullin predominate when coping with orthostatic challenge (p >0.14).
In conclusion, galanin levels increase during elevated levels of central hypovolemia and appear to be important for coping with such challenges. For adrenomedullin, we found that its release depends on degree of central hypovolemia induced fluid shifts and subject’s ability to cope with such challenges. Furthermore, the gradient of acceleration Δgz is shown to be an innovative approach to quantify the grade of central hypovolemia and to assess cardiovascular and neurohormonal responses in those that can tolerate (finishers) or not tolerate (non-finishers) artificial gravity (AG). As AG is being considered as a preventing tool for spaceflight induced deconditioning in future missions, understanding the effects of AG on cardiovascular and hormonal responses in subjects that develop presyncope is important.

Keywords: Syncope, Orthostatic Intolerance, gravity, Artificial gravity, Hormones, Adrenomedullin, Galanin

Received: 16 Jul 2018; Accepted: 22 Dec 2018.

Edited by:

Ovidiu C. Baltatu, Anhembi Morumbi University - Laureate International Universities, Brazil

Reviewed by:

Joyce M. Evans, University of Kentucky, United States
Satoshi Iwase, Aichi Medical University, Japan  

Copyright: © 2018 Stroetges, Laing, Johannes, Mulder, Brix, Roessler, Reichmuth, Rittweger and Goswami. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Prof. Joern Rittweger, Institut für Luft- und Raumfahrtmedizin, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Cologne, Germany, joerna.rittweger@dlr.de
Prof. Nandu Goswami, Medical University of Graz, Graz, 8036, Styria, Austria, nandu.goswami@medunigraz.at