β-Adrenergic blockade heightens the exercise-induced increase in leucine oxidation

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The purpose of this study was to assess the interaction between β- blockade and exercise on amino acid kinetics. This was a three-way crossover experiment using β1-blockade, β1,β2-blockade, and a placebo control. Three 6-h L-[1-13C]leucine and L-[α-15N]lysine infusions were performed. The first 3 h established an isotopic steady state, and 1 h of exercise (~50% of maximal O2 consumption) and 2 h of recovery followed. Plasma glucose decreased with exercise during all trials (P < 0.0001). During β1- and β1,β2-blockade, plasma free fatty acids were reduced during rest and exercise (P < 0.001). Leucine and lysine rates of appearance were unaffected by β-blockade during rest but were decreased with placebo exercise. Leucine oxidation increased with β-blockade (P < 0.01) and exercise (P < 0.001). There was a statistical interaction between both treatments (P < 0.004). In conclusion, leucine oxidation increased with exercise, further increased with β1-blockade, and was additionally heightened with β1,β2-blockade. This cumulative response indicates that leucine oxidation was regulated through β1- and β2-receptors.

Publication Title

American Journal of Physiology - Endocrinology and Metabolism




5 31-5