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Effects of leucine supplementation on animal e human studies related to skeletal muscle protein turnover |
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| Study |
Duration |
Dose |
Methods |
Results |
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| Human |
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| 4 |
180 min |
L-leucine: 1.09 and or 1.74 μmol/kg/min with insulin (plasma: 208 and 207 μmol/L) (infusion) |
Leucine + KIC rates of appearance; KIC oxidation; Leucine-carbon flux |
Leucine 1.09 μmol/kg/min stimulated leucine deposition into body protein in 37.7% but did not suppress endogenous proteolysis; Leucine 1.74 μmol/kg/min with insulin had a cumulative effect of 49.9% on net leucine deposition into body protein. |
| 5 |
7 h |
L-leucine: 154 ± 1 mmol/kg-1/h-1 (infusion) |
Whole-body valine and phenylalanine (tracers) flux |
Inhibition of protein degradation without causing an increase in protein synthesis. |
| 6 |
16 h |
BCAA: 1.66 μmol/kg/min (infusion) |
Whole-body (arterial and venous) leucine and phenylalanine (tracers) flux rates |
Suppressed rate of whole-body (-37%) and forearm (-43%) muscle proteolysis. |
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| Rat |
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| 8† |
105 min |
BCAA: 246 mg/kg-1/h-1 (infusion) |
- |
Neither muscle protein synthesis nor breakdown affected. |
| 9 |
NR |
L-leucine: 0.1, 0.2, 0.25 and/or 0.5 mM (muscle incubation) |
Rate of 14CO2 and KIC production |
Protein synthesis was stimulated in: 10% (0.1 mM), 19% (0.2 mM) and 42% (0.5 mM); Protein degradation was inhibited in: 0% (0.1 mM), 6% (0.2 mM), 15% (0.25 mM) and 26% (0.5 mM). |
| 1 |
2 h |
L-leucine: 0.5 mM (muscle incubation) |
Incorporation of tyrosine (tracer) into proteins |
Leucine increased the specific activity of the proteins by 25% and incorporated tissue proteins by 11.5%. |
| 27 |
2 h |
L-leucine: 0.5 mM (muscle incubation) |
Rate of tyrosine (tracer) incorporated and released |
Protein synthesis was stimulated in the soleus muscles by 69% and in EDL muscles by 38%. No effects on protein degradation were observed. |
| 12 |
NR |
L-leucine: 5 mM (muscle incubation) |
Release of acid-soluble 3H-tyrosine (tracer) |
Leucine caused a significantly reduction in proteolysis of -8 to 12%. |
| 11 |
NR |
L-leucine: 10 mM (muscle incubation) |
Rate of tyrosine (tracer) released |
Decreased whole-body proteolytic rate in 25%. |
| 14 |
10 d |
L-leucine: ~0,7 g/kg/day* (ingestion) |
Rate of tyrosine (tracer) released |
Suppressed postprandial proteolysis in old rats in 40% (measured by proteasome-dependent proteolysis). |
| 17 |
12–15 d |
BCAA: 1 g/kg/day* (ingestion) |
Incorporation of L- [2,6-3H]phenylalanine and release of tyrosine (tracers) |
Suppression on the loss of body weight (-1.5 vs. -4.5 g of control group); increase in rate of protein synthesis in gastrocnemius muscle (~50–60%) and in weight of the soleus muscle (~0.007 g); decrease of protein degradation in soleus muscle (-1500 g/2 h measured by fluorescence). |
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| Mice |
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| 16 |
20 d |
L-leucine: ~4.2 g/day* (ingestion) |
Rate of incorporation of [3H]-phenylalanine and release of tyrosine (tracers) |
Protein synthesis was higher around 23.4% and degradation reduced in by around 11% with leucine supplementation. |
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| Calves |
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| 18 |
5 d |
L-leucine: 239.6 μmol/L (infusion) |
Urea creatinine, urea nitrogen and urea 3-methyl-histidine levels |
Improvement on nitrogen balance without effect on protein degradation |
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† = Unpublished results; *Relativized according to the data provided; AA = amino acid; BCAA = branched-chain amino acids; KIC = [1-14C]alpha-ketoisocaproate acod; NR = Not related. | ||||
Zanchi et al. Nutrition & Metabolism 2008 5:20 doi:10.1186/1743-7075-5-20 |
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