Fig. 5

Enrichment and rate of appearance of ¹³C₆-phenylalanine. a Plasma ¹³C₆-phenylalanine (¹³C₆-Phe) enrichment (tracer-to-tracee ratio (TTR)) during the entire infusion period. Mean ± SE, n = 13. b Rate of appearance (μmol/kg LBM/hr) of ¹³C₆ Phe (Ra) during the basal period (BASAL, 3 hrs), after protein intake and exercise (PROT + EX, 3 hrs) and over the two periods combined (TOTAL, 6 hrs). Over the total period, Ra tended to be higher in rheumatoid arthritis patients (RA) vs. healthy controls (CON) (p = 0.110). Individual data are shown with line at mean ± SE, n = 13