TY - JOUR
T1 - Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids.
AU - Mourtzakis, Marina
AU - Saltin, B.
AU - Graham, T.
AU - Pilegaard, H.
PY - 2006
Y1 - 2006
N2 - During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44 ± 1% peak oxygen consumption (mean ± SE) until exhaustion (exhaustion at 3 h 23 min ± 11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout (P < 0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake (P < 0.05) was also associated with decreasing PDH activity (P < 0.05) and increased PDH kinase 4 mRNA (P < 0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised 68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise.
AB - During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44 ± 1% peak oxygen consumption (mean ± SE) until exhaustion (exhaustion at 3 h 23 min ± 11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout (P < 0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake (P < 0.05) was also associated with decreasing PDH activity (P < 0.05) and increased PDH kinase 4 mRNA (P < 0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised 68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise.
U2 - 10.1152/japplphysiol.00571.2005
DO - 10.1152/japplphysiol.00571.2005
M3 - Journal article
SN - 8750-7587
VL - 100
SP - 1822
EP - 1830
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 6
ER -