To simultaneously assess the relative antiproteolytic effect of insulin on both skeletal muscle and in the whole body, phenylalanine rates of appearance (R(a); reflecting proteolysis) were measured across the leg (reflecting skeletal muscle) and in the whole body, utilizing a constant tracer infusion of [2H5]phenylalanine in the basal state and during euglycemic hyperinsulinemia (2,600 μU/ml) in seven normal adults. Phenylalanine R(a) in the leg was significantly decreased during hyperinsulinemia (6.11 ± 0.83 vs. 3.59 ± 0.70 μmol/min, P < 0.001). In contrast, leg phenylalanine rate of utilization (R(d)) was not significantly changed (4.88 ± 0.77 vs. 3.86 ± 0.92 μmol/min). Phenylalanine R(a) in the whole body was significantly decreased during hyperinsulinemia (49.4 ± 2.2 vs. 41.9 ± 2.3 μmol/min, P < 0.001). However, phenylalanine release was suppressed to a significantly greater degree in the leg than in the whole body during hyperinsulinemia (43 ± 7 vs. 15 ± 2%, P < 0.01). These results suggest that insulin suppresses proteolysis in the whole body and in skeletal muscle, even in the face of hypoaminoacidemia. In addition, the substantially greater degree of suppression of proteolysis by insulin in skeletal muscle compared with the whole body suggests that, at least under these conditions, insulin may have a greater antiproteolytic effect on skeletal muscle compared with other tissues.
|Original language||English (US)|
|Journal||American Journal of Physiology - Endocrinology and Metabolism|
|Issue number||6 24-6|
|State||Published - 1991|
- Protein turnover
- Stable isotope tracers
ASJC Scopus subject areas