The effect of ketone bodies on alanine and glutamine metabolism in isolated skeletal muscle from the fasted chick.
The effects of ketone bodies on the metabolism of alanine and glutamine were studied in isolated extensor digitorum communis (EDC) muscles from 24 h-fasted chicks. (1) Acetoacetate and DL-beta-hydroxybutyrate (4 mM) markedly inhibit branched-chain amino acid (BCAA) transamination and alanine formation. (2) Ketone bodies (1 and 4 mM) increase the intracellular concentration and release of glutamate and glutamine, suggesting that inhibition of BCAA transamination does not limit intracellular availability of glutamate for alanine synthesis. (3) Ketone bodies (1 and 4 mM) do not affect glucose uptake by muscles, but decrease the rate of glycolysis as well as the intracellular concentration and release of pyruvate in muscles. (4) Addition of 12 mM-glucose increases the formation of alanine in muscles incubated in the absence of ketone bodies, but has no effect in muscles incubated in the presence of 4 mM ketone bodies. (5) Addition of 5 mM-pyruvate to the media prevents the inhibiting effect of ketone bodies on BCAA transamination and alanine synthesis. These results suggest that ketone bodies decrease alanine synthesis by limiting the intracellular availability of pyruvate, owing to inhibition of glycolysis, and inhibit BCAA transamination by decreasing the intracellular concentration of amino-group acceptors such as pyruvate in EDC muscles from fasted chicks.
Wu
G Y
GY
Department of Animal Science, University of Alberta, Edmonton, Canada.
Thompson
J R
JR
D000409:Alanine / Q000378:metabolism*; D000597:Amino Acids, Branched-Chain; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002645:Chickens; D005215:Fasting; D005947:Glucose / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D005973:Glutamine / Q000378:metabolism*; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007657:Ketone Bodies / Q000378:metabolism* / Q000494:pharmacology; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D011773:Pyruvates / Q000494:pharmacology; D019289:Pyruvic Acid
D000597:Amino Acids, Branched-Chain; D005971:Glutamates; D007657:Ketone Bodies; D011773:Pyruvates; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005947:Glucose; D000409:Alanine