Effect of Supplementing a Mixed Macronutrient Beverage With Graded Doses of Leucine on Myofibrillar Protein Synthesis

Summary

Muscle mass is normally maintained through the regulated balance between the processes of protein synthesis (i.e. making new muscle proteins) and protein breakdown (breaking down old muscle proteins). Proteins are composed of amino acids and we know that amino acids increase muscle protein synthesis. However, not all amino acids are the same. Essential amino acids are ones that must be consumed through food, while non-essential amino acids can be made by our body. Interestingly, the essential amino acids are all that are required to increase the rate of muscle protein synthesis. In addition, the essential amino acid leucine appears to be particularly important in regulating protein synthesis. However, how leucine is able to increase protein synthesis is not entirely understood. Previously, it has been shown that 20-25 g of high-quality protein, such as that found in milk (whey), appears to be the amount of protein that maximizes the rate of muscle protein synthesis after performing a bout of resistance exercise. Thus, we aim to measure the synthesis of new muscle proteins after ingesting different amounts of protein and amino acids. We will measure muscle protein synthesis after consumption of the beverage a participant is randomized to in a leg that has done no exercise ( ie. a rested leg) and in the other leg that has done resistance exercise. Amino acids are 'strung-together' to make protein. The 'essential' amino acids must be consumed through food because our body cannot make them, thus they are consumed when you eat protein rich foods like milk or chicken. Leucine, isoleucine, and valine are simply 3 of the 8 essential amino acids that make up dietary protein. Unlike essential amino acids, 'non-essential' amino acids may be synthesized by the body, however they are also present in protein rich foods like chicken or milk. We aim to determine if it is the leucine content found in 25 g of whey protein that is primarily responsible for maximizing muscle protein synthesis at rest and following resistance exercise. We also wish to determine how muscle genes and metabolism respond to this protocol.

Conditions

• Muscle Protein Synthesis

Interventions

DIETARY_SUPPLEMENT

Positive Control

Subject consumes 25g of whey protein following unilateral exercise

DIETARY_SUPPLEMENT

Negative Control

Subject consumes 6.25g of whey protein following unilateral exercise

DIETARY_SUPPLEMENT

Low Protein Low Leucine Spike

Subject consumes 6.25g of whey protein plus 3g of leucine following unilateral exercise

DIETARY_SUPPLEMENT

Low Protein High Leucine Spike

Subject consumes 6.25g of whey protein plus 5g of leucine following unilateral exercise

DIETARY_SUPPLEMENT

Low Protein + High Leucine + BCAA Spike

Subject consumes 6.25g of whey protein plus 5g of leucine plus valine and isoleucine (BCAA) following unilateral exercise

Sponsors & Collaborators

• McMaster University

  lead OTHER

Principal Investigators

• Stuart M Phillips, PhD · McMaster University

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2011-01-31

Primary Completion

2011-05-31

Completion

2011-05-31

Countries

• Canada

Study Locations