Search tips
Search criteria

Results 1-4 (4)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  Muscle p70S6K phosphorylation in response to soy and dairy rich meals in middle aged men with metabolic syndrome: a randomised crossover trial 
Nutrition & Metabolism  2014;11(1):46.
The mammalian target of rapamycin (mTOR) pathway is the primary regulator of muscle protein synthesis. Metabolic syndrome (MetS) is characterized by central obesity and insulin resistance; little is known about how MetS affects the sensitivity of the mTOR pathway to feeding.
The responsiveness of mTOR pathway targets such as p706Sk to a high protein meal containing either dairy or soy foods was investigated in healthy insulin sensitive middle-aged men and those presenting with metabolic syndrome (MetS). Twenty male subjects (10 healthy controls, 10 MetS) participated in a single-blinded randomized cross-over study. In a random sequence, subjects ingested energy-matched breakfasts composed predominately of either dairy-protein or soy-protein foods. Skeletal muscle biopsies were collected in the fasted state and at 2 and 4 h post-meal ingestion for the analysis of mTOR- and insulin-signalling kinase activation.
Phosphorylated Akt and Insulin receptor substrate 1 (IRS1) increased during the postabsorptive period with no difference between groups. mTOR (Ser448) and ribosomal protein S6 phosphorylation increased 2 h following dairy meal consumption only. p70S6K (Thr389) phosphorylation was increased after feeding only in the control subjects and not in the MetS group.
These data demonstrate that the consumption of a dairy-protein rich but not a soy-protein rich breakfast activates the phosphorylation of mTOR and ribosomal protein S6, required for protein synthesis in human skeletal muscle. Unlike healthy controls, subjects with MetS did not increase muscle p70S6K(Thr389) phosphorylation in response to a mixed meal.
Trial registration
This trial was registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) as ACTRN12610000562077.
PMCID: PMC4190399  PMID: 25302072
2.  The actions of exogenous leucine on mTOR signalling and amino acid transporters in human myotubes 
BMC Physiology  2011;11:10.
The branched-chain amino acid (BCAA) leucine has been identified to be a key regulator of skeletal muscle anabolism. Activation of anabolic signalling occurs via the mammalian target of rapamycin (mTOR) through an undefined mechanism. System A and L solute carriers transport essential amino acids across plasma membranes; however it remains unknown whether an exogenous supply of leucine regulates their gene expression. The aim of the present study was to investigate the effects of acute and chronic leucine stimulation of anabolic signalling and specific amino acid transporters, using cultured primary human skeletal muscle cells.
Human myotubes were treated with leucine, insulin or co-treated with leucine and insulin for 30 min, 3 h or 24 h. Activation of mTOR signalling kinases were examined, together with putative nutrient sensor human vacuolar protein sorting 34 (hVps34) and gene expression of selected amino acid transporters. Phosphorylation of mTOR and p70S6K was transiently increased following leucine exposure, independently to insulin. hVps34 protein expression was also significantly increased. However, genes encoding amino acid transporters were differentially regulated by insulin and not leucine.
mTOR signalling is transiently activated by leucine within human myotubes independently of insulin stimulation. While this occurred in the absence of changes in gene expression of amino acid transporters, protein expression of hVps34 increased.
PMCID: PMC3141572  PMID: 21702994
4.  Whey Protein Ingestion Activates mTOR-dependent Signalling after Resistance Exercise in Young Men: A Double-Blinded Randomized Controlled Trial  
Nutrients  2009;1(2):263-275.
The effect of resistance exercise with the ingestion of supplementary protein on the activation of the mTOR cascade, in human skeletal muscle has not been fully elucidated. In this study, the impact of a single bout of resistance exercise, immediately followed by a single dose of whey protein isolate (WPI) or placebo supplement, on the activation of mTOR signalling was analyzed. Young untrained men completed a maximal single-legged knee extension exercise bout and were randomized to ingest either WPI supplement (n = 7) or the placebo (n = 7). Muscle biopsies were taken from the vastus lateralis before, and 2, 4 and 24 h post-exercise. WPI or placebo ingestion consumed immediately post-exercise had no impact on the phosphorylation of Akt (Ser473). However, WPI significantly enhanced phosphorylation of mTOR (Ser2448), 4E-BP1 (Thr37/46) and p70S6K (Thr389) at 2 h post-exercise. This study demonstrates that a single dose of WPI, when consumed in modest quantities, taken immediately after resistance exercise elicits an acute and transient activation of translation initiation within the exercised skeletal muscle.
PMCID: PMC3257597  PMID: 22253983
leucine; BCAA; p70S6K; 4E-BP1; resistance exercise

Results 1-4 (4)