Effect of Protein High in Leucine on Muscle Protein Balance in Elderly Patients: Acute Study With Protein-tracer-techniques

Background: Improved muscle function/strength will enhance the quality of life of the more frail elderly population. Dietary proteins and amino acids act as anabolic substrates in muscles in elderly people. In particular the amino acid leucine is suggested to have an impact on muscle protein synthesis. In collaboration with the Danish dairy company Arla Foods we will use their conventional Whey protein and leucine enriched Whey protein in an acute study on elderly patients.

Our aim is to examine the acute effects of supplementation with whey protein high in leucine compared to whey protein with normal leucine content on muscle protein synthesis and protein balance in elderly patients.

Methods: We include 10 elderly patients, age 60-85 years in a randomized crossover study. The subjects will be recruited from the Osteoporosis Section at the Department of Endocrinology at Aarhus University Hospital. The subjects are their own controls in 2 x 1 day interventions A: whey protein high in leucine and B: whey protein with normal leucine content. Interventions are conducted with a 4 week washout period between them. On the intervention day postprandial protein synthesis rate will be measured over 2 X 3h using a tracer infusing protocol with 15Nphenylalanine along with blood samples and muscle biopsies. For analyzing steps of signaling in muscle protein synthesis initiated by leucine mammalian target of rapamycin (mTor) and sites downstream from mTor is quantified using western blotting. Whole body protein kinetics are calculated using the formula Q=i*Ei/Ep-i