Low muscle glycogen and elevated plasma free fatty acid modify but do not prevent exercise-induced PDH activation in human skeletal muscle.
OBJECTIVE
To test the hypothesis that free fatty acid (FFA) and muscle glycogen modify exercise-induced regulation of PDH (pyruvate dehydrogenase) in human skeletal muscle through regulation of PDK4 expression.


METHODS
On two occasions, healthy male subjects lowered (by exercise) muscle glycogen in one leg (LOW) relative to the contra-lateral leg (CON) the day before the experimental day. On the experimental days, plasma FFA was ensured normal or remained elevated by consuming breakfast rich (low FFA) or poor (high FFA) in carbohydrate, 2 h before performing 20 min of two-legged knee extensor exercise. Vastus lateralis biopsies were obtained before and after exercise.


RESULTS
PDK4 protein content was approximately 2.2- and approximately 1.5-fold higher in LOW than CON leg in high FFA and low FFA, respectively, and the PDK4 protein content in the CON leg was approximately twofold higher in high FFA than in low FFA. In all conditions, exercise increased PDHa (PDH in the active form) activity, resulting in similar levels in LOW leg in both trials and CON leg in high FFA, but higher level in CON leg in low FFA. PDHa activity was closely associated with the PDH-E1alpha phosphorylation level.


CONCLUSIONS
Muscle glycogen and plasma FFA attenuate exercise-induced PDH regulation in human skeletal muscle in a nonadditive manner. This might be through regulation of PDK4 expression. The activation of PDH by exercise independent of changes in muscle glycogen or plasma FFA suggests that exercise overrules FFA-mediated inhibition of PDH (i.e., carbohydrate oxidation), and this may thus be one mechanism behind the health-promoting effects of exercise.
Kiilerich
Kristian
K
Copenhagen Muscle Research Centre, University of Copenhagen, Copenhagen, Denmark. kkiilerich@bio.ku.dk
Gudmundsson
Mikkel
M
Birk
Jesper B
JB
Lundby
Carsten
C
Taudorf
Sarah
S
Plomgaard
Peter
P
Saltin
Bengt
B
Pedersen
Per A
PA
Wojtaszewski
Jorgen F P
JF
Pilegaard
Henriette
H
D000328:Adult; D001827:Body Height; D001835:Body Weight; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood* / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D010101:Oxygen Consumption; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D012016:Reference Values; D016474:Weight-Bearing; D055815:Young Adult
D005230:Fatty Acids, Nonesterified; D007328:Insulin; C000631432:PDK4 protein, human; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D006003:Glycogen; D017346:Protein Serine-Threonine Kinases