The relative role of protein synthesis and degradation in determining postprandial net protein deposition in human muscle is not known. To this aim, we studied forearm leucine and phenylalanine turnover by combining the arteriovenous catheterization with tracer infusions, before and following a 4 h administration of a mixed meal in normal volunteers. Forearm amino acid kinetics were assessed in both whole blood and plasma. Fasting forearm protein degradation exceeded synthesis (P < 0.01) using either tracer, indicating net muscle protein loss. The net negative forearm protein balance was quantitatively similar in whole blood and in plasma. After the meal, forearm proteolysis was suppressed (P < 0.05- < 0.03), while forearm protein synthesis was stimulated (P < 0.05- < 0.01). However, stimulation of protein synthesis was greater (P < 0.05- < 0.01) in whole blood (leucine data: +50.4 +/- 7.8 nmol/min x 100 ml of forearm; phenylalanine data: +30.4 +/- 11.6) than in plasma (leucine data: +17.8 +/- 5.6 nmol/min x 100 ml of forearm; phenylalanine data: +5.7 +/- 2.1). Consequently, the increment of net amino acid balance was approximately two to fourfold greater (P < 0.04- < 0.03) in whole blood than in plasma. In conclusion, meal ingestion stimulates forearm protein deposition through both enhanced protein synthesis and inhibited proteolysis. Plasma data underestimate net postprandial forearm protein synthesis, suggesting a key role of red blood cells and/or of blood mass in mediating mealenhanced protein accretion.

Mechanisms of postprandial protein accretion in human skeletal muscle. Insight from leucine and phenylalanine forearm kinetics.

ZANETTI, MICHELA;BARAZZONI, ROCCO;
1996-01-01

Abstract

The relative role of protein synthesis and degradation in determining postprandial net protein deposition in human muscle is not known. To this aim, we studied forearm leucine and phenylalanine turnover by combining the arteriovenous catheterization with tracer infusions, before and following a 4 h administration of a mixed meal in normal volunteers. Forearm amino acid kinetics were assessed in both whole blood and plasma. Fasting forearm protein degradation exceeded synthesis (P < 0.01) using either tracer, indicating net muscle protein loss. The net negative forearm protein balance was quantitatively similar in whole blood and in plasma. After the meal, forearm proteolysis was suppressed (P < 0.05- < 0.03), while forearm protein synthesis was stimulated (P < 0.05- < 0.01). However, stimulation of protein synthesis was greater (P < 0.05- < 0.01) in whole blood (leucine data: +50.4 +/- 7.8 nmol/min x 100 ml of forearm; phenylalanine data: +30.4 +/- 11.6) than in plasma (leucine data: +17.8 +/- 5.6 nmol/min x 100 ml of forearm; phenylalanine data: +5.7 +/- 2.1). Consequently, the increment of net amino acid balance was approximately two to fourfold greater (P < 0.04- < 0.03) in whole blood than in plasma. In conclusion, meal ingestion stimulates forearm protein deposition through both enhanced protein synthesis and inhibited proteolysis. Plasma data underestimate net postprandial forearm protein synthesis, suggesting a key role of red blood cells and/or of blood mass in mediating mealenhanced protein accretion.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2627042
 Avviso

Registrazione in corso di verifica.
La registrazione di questo prodotto non è ancora stata validata in ArTS.

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 52
  • ???jsp.display-item.citation.isi??? 52
social impact