תזונה ותוספים Latency and duration of stimulation of human muscle protein synthesis during continuo

[Mike Bikov]

doi: 10.1111/j.1469-7793.2001.0575f.x
April 15, 2001 The Journal of Physiology, 532, 575-579.

Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids
Julien Bohé, J F Aili Low, Robert R Wolfe and Michael J Rennie
+ Author Affiliations

Metabolism Unit, Department of Surgery, University of Texas Medical Branch, Shriners Burns Hospital Galveston, TX 77550, USA
Division of Molecular Physiology, School of Life Sciences, University of Dundee Dundee DD1 4HN, UK
Corresponding author M. J. Rennie: Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 4HN, UK. Email: [email protected]
Abstract

The aim of this study was to describe the time course of the response of human muscle protein synthesis (MPS) to a square wave increase in availability of amino acids (AAs) in plasma. We investigated the responses of quadriceps MPS to a ≈1.7-fold increase in plasma AA concentrations using an intravenous infusion of 162 mg (kg body weight)−1 h−1 of mixed AAs. MPS was estimated from D3-leucine labelling in protein after a primed, constant intravenous infusion of D3-ketoisocaproate, increased appropriately during AA infusion.

Muscle was separated into myofibrillar, sarcoplasmic and mitochondrial fractions. MPS, both of mixed muscle and of fractions, was estimated during a basal period (2.5 h) and at 0.5-4 h intervals for 6 h of AA infusion.

Rates of mixed MPS were not significantly different from basal (0.076 ± 0.008 % h−1) in the first 0.5 h of AA infusion but then rose rapidly to a peak after 2 h of ≈2.8 times the basal value. Thereafter, rates declined rapidly to the basal value. All muscle fractions showed a similar pattern.

The results suggest that MPS responds rapidly to increased availability of AAs but is then inhibited, despite continued AA availability. These results suggest that the fed state accretion of muscle protein may be limited by a metabolic mechanism whenever the requirement for substrate for protein synthesis is exceeded.​

😍