Nutritional Strategies to Augment the Postprandial Muscle Protein Synthetic Response to the Ingestion of a Low Dose of Protein in Middle-aged Women

Study Overview
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Brief Summary
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Using stable isotope methodology, investigators will determine the postabsorptive and postprandial muscle protein synthetic response in 60 female adults (Age 50-79, BMI: <30 kg/m2) immediately after an acute bout of resistance exercise. Participants will be divided in to 5 groups of twelve women (n=12). Each group will receive a different protein beverage or placebo to consume following the resistance exercise training. Group 1 will consume a beverage consisting of whey protein; group 2 will consume whey protein supplemented with additional leucine; group 3 will consume whey protein supplemented with additional leucine and hydrolyzed whey peptides; group 4 will consume whey protein supplemented with additional leucine and citrulline; group 5 will just consume water. During the testing, blood and muscle samples will be collected.

Conditions
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Aging

Intervention / Treatment
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* Behavioral: Resistance Exercise
* Dietary Supplement: 14 g Whey protein
* Dietary Supplement: 6.6 g Whey protein + 1.25 g leucine
* Dietary Supplement: 4 g Whey protein + 1.25 g leucine + 2.6 g Whey peptides
* Dietary Supplement: 6.6 g Whey protein + 1.25 g leucine + 0.8 g Citrulline
* Other: Water control


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI <30 kg/m2 Healthy, sedentary Either 20-30 years old or 50-79 years old Exclusion Criteria: Tobacco use Allergies to milk consumption Unusually high protein consumption Vegan diet Allergies to antibiotics or xylocaine Phenylketonuria (PKU) Diagnosed GI tract diseases Arthritic conditions A history of neuromuscular problems Heart disease Metabolic disorders -Liver, kidney, or urinary disease Musculoskeletal problems Autoimmune disease Neurological disease Previous participation in amino acid tracer studies Predisposition to hypertrophic scarring or keloid formation Individuals on any medications known to affect protein metabolism (i.e. corticosteroids, non-steroidal anti-inflammatories, or prescription strength acne medications). Individuals using thyroid medications or other medications affecting endocrine function Pregnancy Contraindications for exercise BMI ≥30 supplements that influence protein metabolism (e.g omega 3 fish oils)

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 79 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Whey protein<br>After resistance exercise, participants aged 50-79 years will consume 14g Whey protein dissolved in 200 mL of water | Behavioral: Resistance Exercise<br>* Participants will perform unilateral leg extension exercise immediately prior to ingestion of the experimental beverage<br>Dietary Supplement: 14 g Whey protein<br> <br> |
| Experimental: Whey + Leucine<br>After resistance exercise, participants aged 50-79 years will consume 6.6 g Whey protein + 1.25 g Leucine dissolved in 200 mL of water | Behavioral: Resistance Exercise<br>* Participants will perform unilateral leg extension exercise immediately prior to ingestion of the experimental beverage<br>Dietary Supplement: 6.6 g Whey protein + 1.25 g leucine<br> <br> |
| Experimental: Whey + Leucine + Whey peptides<br>After resistance exercise, participants aged 50-79 years will consume 4 g Whey protein + 1.25 g Leucine + 2.6 g Whey peptides dissolved in 200 mL of water | Behavioral: Resistance Exercise<br>* Participants will perform unilateral leg extension exercise immediately prior to ingestion of the experimental beverage<br>Dietary Supplement: 4 g Whey protein + 1.25 g leucine + 2.6 g Whey peptides<br> <br> |
| Experimental: Whey + Leucine + Citrulline<br>After resistance exercise, participants aged 50-79 years will consume 6.6 g Whey protein + 1.25 g Leucine + 0.8 g Citrulline dissolved in 200 mL of water | Behavioral: Resistance Exercise<br>* Participants will perform unilateral leg extension exercise immediately prior to ingestion of the experimental beverage<br>Dietary Supplement: 6.6 g Whey protein + 1.25 g leucine + 0.8 g Citrulline<br> <br> |
| Sham Comparator: Water<br>After resistance exercise, participants aged either 20-30 or 50-79 years old will consume 200 mL water | Behavioral: Resistance Exercise<br>* Participants will perform unilateral leg extension exercise immediately prior to ingestion of the experimental beverage<br>Other: Water control<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The myofibrillar protein synthetic response to protein ingestion | Myofibrillar protein synthesis rates will be assessed during the postabsorptive period for 3 hr and during the 4 hr after the ingestion of the experimental beverages. This will allow us to assess the change from the postabsorptive to the postprandial period | Postabsorptive for 3 hours, Postprandial for 4 hours hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| mTORC1 phosphorylation | Activation of anabolic signaling pathways will be assessed in the fasted state and at 2 and 4 hr after the ingestion of the experimental beverages. | Baseline and at 2 and 4 hours after protein ingestion |