48.　Modifications of neuroendocrine responses in humans induced by simulated microgravity using head-down bed rest (HDBR)

一般演題

Dominika Kanikowska¹, Maki Sato¹, Satoshi Iwase¹, Yuuki Shimizu¹, Yoko Inukai¹, Naoki Nishimura¹,
Hiroki Sakurai^1,2, Junichi Sugenoya¹

¹Department of Physiology, Aichi Medical University School of Medicine, Nagakute
²Department of Algesiology, Aichi Medical University, Nagakute

　Introduction: Head-down bed rest of -6° (HDBR) was used as a model for studying the physiological changes during microgravity in spaceflight.　Exposure of animals and humans to the space flight condition results in numerous immunological and hormonal changes similar to those observed during HDBR, but the mechanisms are not clear.　The aim of the present study was to investigate whether exposure to such an environment led to alterations in the synthesis of some hormones.

　Methods: Eight male volunteers were subjected to HDBR of -6° for 20 days.　Plasma cortisol, insulin, glucose, leptin, ghrelin and TSH, fT3 and fT4 were determined before (PRE), at days 5^th, 15 and after HDBR (POST), to assess the effects of HDBR.

　Results: In subjects, cortisol concentration (PRE: 17.9±1.1 μg/dl; day 5^th: 20.8±1.5 μg/dl) and insulin concentration (PRE: 7.7±0.9 μIU/ml; day 15: 10.13±1.6 μIU/ml) increased significantly, and the concentration of leptin (PRE: 4.3±1.2 ng/ml; POST: 3.52±0.9 ng/ml) and glucose (PRE: 93±1.6 mg/dl; POST: 87±2.0 mg/dl) decreased during HDBR.　The concentration of TSH, fT3, fT4 and ghrelin didn't change significantly during HDBR.
　Discussion: The results indicate that several neuroendocrine parameters are modulated by prolonged HDBR of -6°, and that psychological stress, body composition changes and/or physical inactivity might play a role in inducing these changes.