Role of Leucine in the Regulation of Human Myofibrillar Protein Synthesis at Rest and Following Resistance Exercise
Condition: Regulation of Muscle Protein Synthesis
Study type: Interventional

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, appears to be the amount of
      protein that maximizes the rate of muscle protein synthesis after performing a bout of
      resistance exercise. Thus, the aim is to measure the synthesis of new muscle proteins after
      ingesting the following:

        1. 25g whey protein

        2. 6.25g whey protein supplemented with leucine

        3. 6.25g whey protein supplemented with essential amino acids but no leucine

      The investigators will measure muscle protein synthesis after consumption of the above
      beverages in a leg that has done no exercise ( ie. a rested leg) and in the other leg that
      has done resistance exercise. The hypothesis is that 6.25g whey supplemented with leucine
      will stimulate muscle protein synthesis as effectively as 25g whey, but that 6.25g whey
      supplemented will all the essential amino acids except whey will be less effective at
      increasing muscle protein synthesis. Whey protein is a dairy-based protein found in cow's
      milk, thus when you drink a glass of milk you are consuming some whey protein. However, the
      investigators will be using an isolated form of whey protein, meaning it has been removed
      from milk. As mentioned previously, 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.
    


Intervention name(s): whey protein; whey protein supplemented with leucine; whey protein supplemented with essential amino acids
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): 25 g whey protein; 6.25 g whey protein supplemented with free form leucine; 6.25 g whey protein supplemented with essential amino acids devoid of leucine
Other intervention name(s): whey protein powder; whey protein powder supplemented with free-form leucine; whey protein supplemented with EAA devoid of leucine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: skeletal muscle; FSR; resistance exercise; leucine; protein