PULSE, A protein feeding strategy to promote muscle protein anabolism in the elderly

Sarcopenia is the age associated loss of skeletal muscle mass and function.
This process affects physical performance and thereby the daily functions of
the elderly. Food intake and in particular protein intake has been shown to be
a powerful stimulus to promote net muscle protein anabolism. Hereby it has been
suggested that feeding protein in pulses improves nitrogen balance more than
feeding protein spread over the day does. Such shift in total body protein
retention needs further confirmation from muscle metabolism studies in view of
the aging related loss of muscle mass.
Therefore the present study has been designed to investigate whether a
specific pattern of protein feeding might increase the appearance of labeled
phenylalanine in skeletal muscle tissue in the elderly. It is hypothesized
that ingestion of the same amount of dietary protein over the day in a
pulse-like manner, as opposed to spread over the day, will result in a higher
incorporation of labeled phenylalanine in skeletal muscle tissue.

The purpose of the study is to investigate whether a protein pulse feeding
pattern increases the appearance of labeled phenylalanine in skeletal muscle
tissue over a 24 h period in the elderly.

The proposed intervention study is a randomized single-blind trial, with 2 arms
in parallel (Pulse group, Spread group). In this study, the effect of a protein
feeding strategy will be assessed by measuring the incorporation of
intrinsically labeled phenylalanine (L-[1-13C]phenylalanine) in the Vastus
lateralis muscle of the elderly. The full study comprises a baseline
assessment of 1,5 h and feeding period of 4 days.

A parallel intervention study with two protein diet groups (Pulse group and
Spread group). Every group receives the same daily amount of protein(70g)
including intrinsic labeled amino acids. However, the amounts provided at
specific time points during the day will be different. In the Pulse group the
subjects receive a large bolus of protein (50g) during breakfast and 2 smaller
boluses of 10g each during lunch and dinner time. In the Spread group, the
subjects will receive the same amount of protein throughout the day provided in
6 different portions (11.6g per portion).

The risks involved in participating in this experiment are minimal. The test
beverages are made from normal nutritional ingredients and for this reason do
not bring any health risks. These beverages contain protein which includes
labeled amino acids. The latter amino acids are not radioactive. They are
widely used in many metabolic studies and are considered completely safe.
For blood collection the only risk is that of a small local hematoma. This is
the same for the muscle biopsies which will be collected by an experienced
physician. Following the biopsy the minor incision heals rapidly and
completely.