Protein feeding prior to sleep as a dietary strategy to improve post-exercise recovery and muscle mass in young and elderly men

The regulation of muscle mass and function are critical during muscle growth
and repair in both athletes as during advanced ageing, when the loss of muscle
mass is a common phenomenom (sarcopenia). Sarcopenia has a large impact on the
healthcare system causing an increased morbiditeit, hospitalization and/or
institutionalization. The loss of muscle mass is caused by a combination of
factors as a suboptimal food intake and a sedentary lifestyle. Aslo, an optimal
nutritional status seems to be important during recovery in athletes. A
disregulation of muscle protein turnover results in a disbalance between muscle
protein synthesis and muscle protein breakdown. The intake of dietary protein
is shown to have a positive impact on the synthesis of skeletal muscle
proteins. Amino acids stimulates muscle protein synthesis and slows down muscle
protein breakdown, resulting in a positive muscle protein net balance in both
young and elderly. However, the timing of intake and the total amount influence
muscle protein netto balance. An extra amount of dietary protein prior to sleep
can increase the daily protein intake and could result in a positive protein
balance. Moreover, it is unknown whether the intake of an amount of proteins
prior to sleep stimulates muscle protein synthesis during the night. In the
present study we investigte the impact of a single amount of protein with or
without additional leucine on muscle protein synthesis during overnight sleep
in healthy young and old men. Furthermore, we will assess digestion and
absorption kinetics during sleep. The use of intrinsically labeled casein in
combination with intravenous stable isotope infusion will allow us to assess de
novo muscle protein synthesis.

The primary objective of this study is to investigate the effect of a meal-like
amount of dietary protein prior to sleep on postprandial muscle protein
synthesis in healthy young and elderly men, following exercise, during the
night. Furthermore, as a secondary objective, we will assess digestion and
absorption kinetics during sleep.

Double-blind randomized intervention study

The young subjects will consume a testdrink of 400 ml with 0 gram, 30 gram
intrinsically labelled casein of 30 gram intrinsically labelled casein + 2.0 g
leucin, randomized after exercise or rest, prior to sleep.
The elderly will consume a testdrink of 400 ml with 0 gram, 20 gram
intrinsically labelled casein, 40 gram intrinsically labelled casein, or 20
gram intrinsic labelled casein + 1.2 gram leucin, randomized after exercise or
rest, prior to sleep.

The burden and risks associated with participation are small. Insertion of the
catheters is comparable to a blood draw and could result in a small hematoma.
Muscle biopsies will be taken under local anesthesia by an experienced
physician, but may cause some minor discomfort for maximally up to 24 h after
completion. The discomfort is comparable to muscle soreness or the pain one has
after bumping into a table. In total 5 (during screening 8 ml) and 15 blood
samples (during test, 10 mL) will be taken. The total amount of blood draws
(180 ml) is less than half the amount of a blood donation and will be
completely restored in approximately 1 month. Participants come to the
university twice: 1 screening (4 hours) and 1 experimental trial (evening and
night, 14 hours). For the screening, participants have to be fasted, so they
are not allowed to eat and drink (except for water) from 22h00 the evening
before. Also, 2 days prior to the experimental trial participants should not
perform any type of intense physical exercise, and 24 hours prior do not
consume alcohol. During the screening a medical questionnaire will be filled
in, a DEXA scan and OGTT will be performed. Furthermore, the participants will
be asked to consume distributed meals during the day of the trial and to fill
out their food intake and an activity diary for 2 days prior to the
experimental trial. During the experimental trial the subjects will stay
overnight and prior/during their sleep we will collect muscle and blood
samples. All participants will consume a test beverage consisting of milk
protein with or without additional leucine prior to sleep. The intrinsically
labeled milk protein has been approved for human consumption and has been used
in previous METC approved studies. With the use of both intrinsically labeled
protein, intravenous stable isotope infusion of amino acids and blood and
muscle samples de novo muscle protein synthesis from the ingested testdrink can
be assessed during the night. There is no direct benefit for the participants,
only their contribution to scientific knowledge and nutritional strategies that
prevent muscle loss during recovery in athlethes and with advanced ageing in
the elderly, which will be obtained from this study and used in the future.