Human Forearm Muscle Metabolism during Exercise III Uptake, release and oxidation of β-hydroxybutyrate and observations on the β-hydroxybutyrate/acetoacetate ratio

Abstract

The metabolism of ketone bodies by human forearm muscle during exercise was studied in healthy young volunteers. Net muscular uptakes of β-hydroxybutyrate and acetoacetate were observed at rest. The arterial-deep venous concentration differences of both these metabolites correlated positively to their arterial concentrations at rest. No correlation between β-hydroxybutyrate uptake and arterial concentration was observed during exercise. Results using DL-β-hydroxybutyrate-4-¹⁴C as tracer during exercise indicated that the L(+) isomer was taken up to a lesser extent than the D(-) isomer. During arterial infusion of D(-)-β-hydroxybutyrate-3-¹⁴C, the deep venous β-hydroxybutyrate specific activity was lower than that of arterial blood, indicating that an intramuscular production of β-hydroxybutyrate occurred during exercise. Net production of acetoacetate and/or β-hydroxybutyrate by the forearm muscle was observed in five of seven experiments.

Key Words:

• Acetoacetate
• exercise
• forearm
• β-hydroxybutyrate
• lactate
• metabolism
• muscle
• pyruvate