Fig. 3. BCAA elevations are derived from a long–term pool of amino acids.

a, Plasma levels (mean ± SEM) of ¹³C–labeled leucine and valine normalized to food intake over time following a two–hour exposure to diets containing ¹³C–labeled leucine and valine. The time points correspond to the red arrowheads in the diagram. b, Diagram of experiment using labeled diets to investigate contributions to plasma BCAA levels from long–term pools. Two cohorts of mice were used for these experiments, one sacrificed in the fed state and a second sacrificed in the fasted state at the time points indicated by the red arrowheads. c, Fractional labeling of total amino acids in protein hydrolysate of gastrocnemius muscle from fasted KP^–/–C mice and control littermates (n = 8 KP^–/–C, n = 6 control). d, Fractional labeling of plasma amino acids in KP^–/–C and control mice in the fed state (n = 3 KP^–/–C, n = 4 control). e, The calculated contribution of the short– and long–term BCAA pools to the BCAAs present in plasma . f, Mean (±SEM) gastrocnemius weight (left panel, t-test, P=0.01), a predominantly fast–twitch muscle, and heart weight (right panel) normalized to body weight (n = 6 KP^–/–C, n = 10 control).