Energy, protein and substrate metabolism in simulated
microgravity.
Acheson, Kevin J., Jacques D[acute]ecombaz, Christelle Piguet-Welsch, Franck
Montigon, Bernard Decarli, Isabelle Bartholdi, Edward B. Fern.
Nestec Ltd., Nestl[acute]e Research Centre, Vers-chez-les-Blanc, 1000
LAUSANNE 26, Switzerland
APStracts 2:0030R, 1995.
Whole body protein turnover, and energy expenditure before and during
an oral glucose tolerance test (1g/kg Body weight), were studied on
separate occasions, in 6 healthy, young men before and during 3 days
of simulated microgravity using the 6 degrees Head Down Tilt (HDT) method.
After 42-47h of HDT basal insulin concentrations increased
significantly from 9.4+/-1.9 to 13.1+/-2.1 [mu]U/ml (p<0.002). No
significant differences in glycemia, insulinemia nor free fatty acid
concentrations were observed in response to the oral glucose load.
With HDT increases were observed in basal, postabsorptive, resting
metabolic rate (8%; p<0.05), lipid oxidation (33+/-2 to 51+/-5 mg/min;
p<0.02), and the thermic effect of glucose (7.7+/-1 to 10.7+/-0.6%; NS).
Protein turnover (arithmetic mean of ammonia and urea flux rates) was
unchanged by HDT but a significant increase was seen when calculated
from ammonia alone (p<0.02). The present data show that HDT results
in an increased energy requirement through elevations in both the
basal metabolic rate and the thermic response to food ingestion.
These changes may have been brought about by a cephalic shift of body
fluids similar to that experienced in microgravity.
Received 31 May 1994; accepted in final form 27 January 1995.
APS Manuscript Number R292-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.