NUTRITION – LEUCINE – HMB


2 RESEARCH ARTICLES


EQUIVALENT HYPERTROPHY AND STRENGTH GAINS IN HMB or LEUCINE SUPPLEMENTED MEN – 2018


Jakubowski JS1Wong EPT1Nunes EA2Noguchi KS1Vandeweerd JK1Murphy KT1Morton RW1McGlory C1Phillips SM

ABSTRACT
– Ingestion of proteins with high leucine content during resistance training (RT) can augment hypertrophy
– Some data suggest that a leucine metabolite, β-hydroxy, β-methylbutyrate (HMB), is substantially more anabolically efficacious than leucine
PURPOSE
– Test whether HMB vs. Leucine, added to Whey Protein, results in muscle hypertrophy and strength gains in young men performing resistance training
METHODS
26 resistance-trained men (23 ± 2 y) performed 12 wk of RT with 3 phases
– Phase 1: 8 wk of periodized RT (3 training sessions/wk)
– Phase 2: 2 wk overreaching period (5 sessions/wk)
– Phase 3: 2 wk taper (3 sessions/wk)
– Participants were randomly assigned to twice daily ingestion of:
(a) whey protein (25 g) plus HMB (1.5 g) (Whey+HMB; n=13)
(b) whey protein (25 g) plus leucine (1.5 g) (Whey+Leu; n=13)
– Skeletal muscle biopsies were performed before and after RT
– Measures of fat and bone-free mass (FBFM), vastus lateralis (VL) muscle thickness and muscle cross-sectional area (CSA – both by ultrasound), muscle fiber CSA, and 1-repetition maximum (1-RM) strength tests were determined
RESULTS
– Increases in FBFM, VL muscle thickness, muscle CSA and fiber type CSA and 1-RM strength with no differences between groups at any phase
– No differences between groups or time-by-group interactions in hormone concentrations at any phase of the RT program
CONCLUSION
– HMB added to whey did not result in greater increases in any measure of muscle mass, strength, or hormonal concentration compared to leucine added to whey
– Our results show that HMB is no more effective in stimulating RT-induced hypertrophy and strength gains than leucine


EFFECTS OF LEUCINE AND ITS METABOLITE HMB ON MPS – 2013


D J Wilkinson, Hossain, Hill, B E Phillips, H Crossland, J Williams, P Loughna, Churchward-Venne, Breen, S M Phillips, Etheridge, Rathmacher, Smith, Szewczyk, P J Atherton
INTRODUCTION
– Leucine (Leu) possesses the most marked anabolic characteristics in acting as a trigger element for initiation of protein synthesis
– As a BCAA, Leu can be catabolized within muscle, posing the possibility metabolites of Leu could be involved in mediating (bringing about) the anabolic effect(s) of Leu
OBJECTIVE/METHOD:
(1) Measure muscle protein anabolism in response to Leu and its metabolite HMB
(2) Study effect of HMB or Leu alone on MPS and for HMB we also measured muscle proteolysis
RESULTS
(1) 3.42g free-acid FA-HMB (providing 2.42 g of pure HMB) exhibited rapid bioavailability and similarly to 3.42g Leu, stimulated MPS; HMB +70% vs. Leu +110%
(2) While HMB and Leu both increased anabolic signalling this was more pronounced with Leu
(3) HMB consumption reduced muscle protein breakdown (MPB; −57%) in an insulin-independent manner
CONCLUSIONS:
– HMB induces acute muscle anabolism (increased MPS and reduced MPB) albeit perhaps via distinct, and/or additional mechanism(s) to Leu
KEY POINTS
(1) Leucine acts as both a ‘trigger’ for the initiation of protein synthesis, and as a substrate for newly synthesized protein
(2) Leucine can be metabolized within skeletal muscle, leaving open the possibility that it’s metabolites might possess anabolic properties
(3) HMB, has shown +ve effects on lean body mass and strength following exercise, and in disease-related muscle wasting, yet its impact on muscle protein turnover is undefined
(4) HMB stimulates muscle protein synthesis to a similar extent to Leucine
(5) HMB was also found to decrease muscle protein breakdown
(6) That HMB enhances muscle protein anabolism may partly (or wholly) underlie its pre-defined anabolic/anti-catabolic supplemental efficacy

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