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Mechanisms of activation of muscle branched‐chain alpha‐keto acid dehydrogenase during exercise in man.
Author(s) -
van Hall G,
MacLean D A,
Saltin B,
Wagenmakers A J
Publication year - 1996
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1996.sp021542
Subject(s) - ingestion , medicine , glycogen , endocrinology , chemistry , physical exercise , alpha (finance) , exercise physiology , surgery , construct validity , patient satisfaction
1. Exercise leads to activation (dephosphorylation) of the branched‐chain alpha‐keto acid dehydrogenase (BCKADH). Here we investigate the effect of low pre‐exercise muscle glycogen content and of branched‐chain amino acid (BCAA) ingestion on the activity of BCKADH at rest and after 90 min of one‐leg knee‐extensor exercise at 65% maximal one‐leg power output in five subjects. 2. Pre‐exercise BCAA ingestion (308 mg BCAAs (kg body wt)‐1) caused an increased muscle BCAA uptake, a higher intramuscular BCAA concentration and activation of BCKADH both at rest (9 +/‐ 1 versus 25 +/‐ 5% for the control and BCAA test, respectively) and after exercise (27 +/‐ 4 versus 54 +/‐ 7%). 3. At rest the percentage active BCKADH was not different, 6 +/‐ 2% versus 5 +/‐ 1%, in the normal and low glycogen content leg (392 +/‐ 21 and 147 +/‐ 34 mumol glycosyl units (g dry muscle)‐1, respectively). The post‐exercise BCKADH activity was higher in the low (46 +/‐ 2%) than in the normal glycogen content leg (26 +/‐ 2%). 4. It is concluded that: (1) the mechanism of activation by BCAA ingestion probably involves an increase of the muscle BCAA concentration; (2) BCKADH activation caused by exercise and BCAA ingestion are additive; (3) low pre‐exercise muscle glycogen content augments the exercise‐induced BCKADH activation without an increase in muscle BCAA concentration; and (4) the mechanism of BCKADH activation via BCAA ingestion and low muscle glycogen content are different.