Leucine Co-ingestion and Myofibrillar Protein Synthesis in Older Adults

Summary

The loss of muscle mass with aging is associated with a dysregulation of muscle protein synthesis (MPS) that is generally characterized by a suppressed MPS response to protein ingestion. This 'anabolic resistance' to protein feeding can be overcome with the ingestion of larger protein servings (\~0.4g/kg/meal, equivalent to \~ 30 - 40g/meal); however, older adults would likely find it challenging to consume such quantities of protein on a per meal basis.

The amino acid leucine has a unique role as a key 'activator' of MPS. Some research shows that increasing the leucine content of a suboptimal dose of a protein supplement can enhance the MPS response in older adults. However it is currently unknown whether the co-ingestion of leucine with normal, mixed meals can increase MPS. Furthermore, it has been suggested that leucine supplementation may only benefit older adults consuming suboptimal daily protein intakes. Therefore, the purpose of the current study is to examine the impact of leucine co-ingestion with mixed macronutrient meals on the myofibrillar protein synthetic response in older men consuming daily protein intakes at or below the current recommendations. A further objective is to determine whether the myofibrillar protein synthetic response to a session of resistance exercise is enhanced by leucine supplementation with meals. The investigators hypothesize that, in both the exercised and non-exercised condition, leucine co-ingestion at meals will enhance integrative myofibrillar protein synthesis in older adults consuming lower daily protein intakes, but will not augment MPS in those consuming higher daily protein. The investigators further hypothesize that the influence of leucine supplementation on MPS will be greater in the exercise condition than the non-exercise condition.

Conditions

• Aging
• Sarcopenia

Interventions

DIETARY_SUPPLEMENT

Leucine

5 g leucine with sucrose and maltodextrin

DIETARY_SUPPLEMENT

Placebo

5 g glycine with sucrose and maltodextrin

Sponsors & Collaborators

• Canadian Institutes of Health Research (CIHR)

  collaborator OTHER_GOV

• McMaster University

  lead OTHER

Principal Investigators

• Stuart M Phillips, PhD · McMaster University

Study Design

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

SINGLE

Model

PARALLEL

Eligibility

Min Age

65 Years

Max Age

85 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2015-05-31

Primary Completion

2015-10-31

Completion

2015-10-31

Countries

• Canada

Study Locations