Physical exercise and normobaric hypoxia: independent modulators of peripheral cholecystokinin metabolism in man.
The purpose of the present investigation was to determine the independent effects of hypoxia and physical exercise on peripheral cholecystokinin (CCK) metabolism in humans. Thirty-two physically active men were randomly assigned in a double-blind manner to either a normoxic (N; n = 14) or hypoxic (H; n = 18) group. During the acute study, subjects in the H group only participated in two tests, separated by 48 h, which involved a cycling test to exhaustion in normobaric normoxia and normobaric hypoxia (inspired O(2) fraction = 0.21 and 0.16, respectively). In the intermittent study, N and H groups cycle-trained for 4 wk at the same relative exercise intensity in both normoxia and hypoxia. Acute normoxic exercise consistently raised plasma CCK during both studies by 290-723%, which correlated with increases in the plasma ratio of free tryptophan to branched chain amino acids (r = 0.58-0.71, P < 0.05). In contrast, acute hypoxic exercise decreased CCK by 7.0 +/- 5.5 pmol/l, which correlated with the decrease in arterial oxygen saturation (r = 0.56, P < 0.05). In the intermittent study, plasma CCK response at rest and after normoxic exercise was not altered after physical training, despite a slight decrease in adiposity. We conclude that peripheral CCK metabolism 1) is more sensitive to acute changes than chronic changes in energy expenditure and 2) is potentially associated with acute changes in tissue PO(2) and metabolic precursors of cerebral serotoninergic activity.
Bailey
D M
DM
Hypoxia Research Unit, Health and Exercise Sciences Research Laboratory, School of Applied Sciences, University of Glamorgan, South Wales, CF37 1DL, United Kingdom. dbailey1@glam.ac.uk
Davies
B
B
Castell
L M
LM
Newsholme
E A
EA
Calam
J
J
D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000097:blood; D000886:Anthropometry; D001274:Atmospheric Pressure; D001786:Blood Glucose / Q000032:analysis; D002766:Cholecystokinin / Q000097:blood*; D004032:Diet; D004311:Double-Blind Method; D002149:Energy Intake; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000097:blood; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010806:Physical Education and Training; D012016:Reference Values; D014364:Tryptophan / Q000097:blood
D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D019344:Lactic Acid; D014364:Tryptophan; D002766:Cholecystokinin; D005990:Glycerol