Evidence that a decrease in liver glycogen content stimulates FFA mobilization during exercise.
This study evaluated a liver glycogen content decrease before exercise on the metabolic responses during exercise. Rats injected with glucagon (20 microg x kg(-1)) were compared to rats with a 50% food restriction (1/2-fast) and normally fed rats. All were studied at rest and during exercise (26 m/min, 0% grade). Resting liver glycogen concentrations were twice as high (P<.01) in normally fed rats, with no significant differences between 1/2-fast and glucagon-injected rats. During exercise, liver glycogen content was significantly reduced in normally fed rats. After exercise, plasma insulin levels were decreased (P<.01) in all groups, and beta-hydroxybutyrate concentrations were similar in normally fed and glucagon-injected rats and significantly (P<.01) lower in 1/2-fast rats. Exercise caused a significant increase in FFA concentrations in all groups (P<.01). No significant differences in FFA concentrations were found between 1/2-fast and glucagon-injected groups (P>0.05).
Couturier
K
K
UFR-STAPS, Faculté des Sciences du Sport et de l'Education Physique, Université Claude Bernard, Lyon, France.
Bélanger
P
P
Latour
M G
MG
Lavoie
J M
JM
D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005215:Fasting / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005934:Glucagon / Q000008:administration & dosage / Q000378:metabolism; D007328:Insulin / Q000097:blood; D008099:Liver / Q000378:metabolism*; D008112:Liver Glycogen / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008112:Liver Glycogen; D005934:Glucagon