LEUCINE – KEY AMINO ACID FOR MUSCLE MASS
1
LEUCINE ADDED TO MILK
Devries MC1, McGlory C1, Bolster DR2, Kamil A2, Rahn M2, Harkness L2, Baker SK3, Phillips SM1.
BACKGROUND
– Older adults show a blunted muscle protein synthesis (MPS) response to meals relative to younger adults
– Evidence suggests that this anabolic resistance can be overcome by consuming greater quantities of Leucine
OBJECTIVE
– Determine whether adding Leucine to 10 g of milk proteins would, when compared with a larger dose (25 g) of whey protein isolate (WPI), result in similar increases in acute (hourly) and integrated (daily) myofibrillar protein synthesis (myoPS)
METHODS
– Healthy older (age: 69 ± 1 y) women (n = 11/group)
– 2x daily consumption of either:
(1) WPI [25 g WPI (3 g l-leucine)]
(2) or Leucine (LEU; 10 g milk protein with 3 g total l-leucine) for 6 days
– Participants performed unilateral resistance exercise to allow assessment of the impact of the supplement alone and with resistance exercise
RESULTS
– Acute myoPS increased in both legs in response to LEU and WPI compared with fasting
– The increase was greater with LEU than with WPI in the exercised leg but not in the rested leg
– The acute myoPS response was greater in the exercised leg than in the rested leg for both WPI (63%) and LEU (58%)
– Integrated myoPS increased with WPI and LEU in the exercised leg during supplementation, and with WPI but not LEU in the rested leg compared with the basal state
CONCLUSIONS
– A lower-protein (10 compared with 25 g/dose), Leucine-matched beverage induced similar increases in acute and integrated myoPS
– Longer-term interventions are needed to substantiate these findings
OBJECTIVE
– We measured the acute (hourly) and integrated (daily) myofibrillar protein synthesis (myoPS) response to consumption of a high-quality mixed protein beverage compared with an isonitrogenous protein beverage with added leucine
DESIGN
– Healthy older women (aged 65–75 y, n = 11/group) consumed a fixed, weight-maintaining diet with protein at 1.0 g · kg–1 · d–1
– They were randomly assigned to twice-daily consumption of either:
a) 15 g milk protein beverage containing 4.2 g Leucine (LEU)
b) or 15 g mixed protein (milk and soy) beverage containing 1.3 g Leucine (CON)
– Unilateral leg resistance exercise allowed a determination of acute ([13C6]-phenylalanine infusion, hourly rate) and integrated (deuterated water ingestion, daily rate) exercised and rested myoPS responses.
RESULTS
– Acute myoPS increased in response to feeding in the rested (CON: 13% ± 4%; LEU: 53% ± 5%) and exercised (CON: 30% ± 4%; LEU: 87% ± 7%) leg in both groups, but the increase was greater in LEU
– Integrated myoPS increased during the supplementation period in both legs (rested: 9% ±1%; exercised: 17% ± 2%) in LEU, but in the exercised leg only (7% ± 2%) in CON
CONCLUSIONS
– A 15-g protein-containing beverage with ∼4 g Leucine induced greater increases in acute and integrated myoPS than did an isonitrogenous, isoenergetic mixed-protein beverage
– Declines in muscle mass in older women may be attenuated with habitual twice-daily consumption of a protein beverage providing 15 g protein and higher (4.2 g/serving) amounts of Leucine
Philip J Atherton, Kenneth Smith et al
PURPOSE/METHODS
– RE: 6 × 8 knee-extension repetitions at 75% of 1-RM
– Groups (n = 9) of young 24 ± 6 y and older men 70 ± 5 y
(i) RE followed by Slim-Fast Optima (SFO 10 g PRO; 24 g CHO) with 4.2 g of leucine (LEU)
(ii) RE + SFO with 4.2 g of alanine (ALA; isonitrogenous control).
RESULTS
(1) In young men, area under the curve and peak FSR were greater in the SFO + LEU than in the SFO + ALA group, after RE
(2) In older men, AUC post-exercise anabolic responses were greater in the SFO + LEU than SFO + ALA group, after RE
(3) Irrespective of age, increases in p70S6K1 phosphorylation were evident in response to both SFO + LEU and SFO + ALA, although greater with leucine supplementation than alanine, specifically in the older men
CONCLUSION
– Addition of Leucine to a sub-maximal PRO bolus improves anabolic responses to RE in young and older men
Churchward-Venne, Breen, Di Donato, Hector, Mitchell, Moore, Stellingwerff, Breuille, Offord, Baker, Phillips
OBJECTIVE
· We assessed effect of supplementation on Myofibrillar PRO Synthesis (MPS) at rest and after exercise.
(1) a lower-PRO mixed macronutrient beverage with varying doses of Leucine or
(2) a mixture of BCAAs
DESIGN
· 40 men (21±1 y) completed unilateral knee-extensor resistance exercise before ingestion of:
(1) 25g whey PRO (W25) (3.0 g Leucine)
(2) 6.25g whey protein (W6) (0.75g Leucine)
(3) 6.25g whey protein supplemented with Leucine to 3.0 g total Leucine (W6+Low-Leu)
(4) 6.25g whey protein supplemented with Leucine to 5.0 g total Leucine (W6+High-Leu)
(5) 6.25g whey protein supplemented with Leucine, Isoleucine, and Valine to 5.0 g total Leucine
RESULTS
(1) Area under blood Leucine curve was greatest for W6+High-Leu group compared with W6 and W6+Low-Leu groups
(2) In the postprandial period: over 0–1.5 h, rates of MPS were increased above baseline in all treatments
(3) Post-meal period: over 1.5–4.5 hr, MPS remained increased above baseline after all treatments but was greatest after W25 (approx. 267%) and W6+High-Leu (approx. 220%)
CONCLUSIONS
– A low-PRO (6.25g) mixed beverage can be as effective as a high-PRO dose (25g) at stimulating increased MPS rates when supplemented with a high (5g total) amount of Leucine
– Churchward-Venne, Burd, Mitchell, West, Philp, Marcotte, Baker, Baar, Phillips
METHODS:
– 24 males, 22 ± 0.6 yrs, completed an acute bout of unilateral resistance exercise prior to consuming either:
(a) 25 g of whey protein (WHEY)
(b) 6.25 g whey protein with total leucine equivalent to WHEY (LEU)
(c) 6.25 g whey protein with total essential amino acids (EAAs) equivalent to WHEY for all EAAs except leucine (EAA-LEU).
CONCLUSIONS:
(1) A low dose of whey supplemented with leucine or all other EAAs was as effective as a complete PRO (WHEY) in stimulating postprandial MPS
(2) However only WHEY was able to sustain increased rates of MPS post-exercise and may therefore be most suited to increase exercise-induced muscle protein accretion