The effects of protein ingestion and exercise on plasma and dialysate amino acid concentrations during hemodialysis

Chronic hemodialysis patients suffer from poor physical functioning due to
progressive loss of skeletal muscle mass and function. Preliminary data from
our lab shows that 8 - 15 grams of amino acids are lost into the dialysate
during a hemodialysis session, causing a significant decline in plasma amino
acid concentrations. Few studies in chronic hemodialysis patients suggest that
oral protein ingestion during hemodialysis is able to prevent this decline and
associated muscle protein breakdown. However, the amount of protein required to
achieve this effect (±60 g) is not feasible for clinical practice. Nonetheless,
a feasible amount of protein combined with an additional anabolic stimulus,
such as exercise, might be able to prevent the hemodialysis-induced decline in
plasma amino acid concentrations. In healthy adults, exercise before protein
ingestion enhances the net protein balance of skeletal muscle and improves
postprandial glycemia. However, the effect of intradialytic exercise on plasma
and dialysate amino acid concentrations throughout hemodialysis is unclear. In
addition, it is not known if this effect differs between fed and fasted
patients. Knowledge about the acute metabolic response after protein ingestion
and exercise during hemodialysis is important for the development of
intradialytic anabolic strategies in chronic hemodialysis patients.

To assess the effects of intradialytic exercise and protein ingestion on amino
acid loss into the dialysate and plasma total amino acid concentrations.

Randomized cross-over (four groups) study design.

During four HD sessions, patients will (A) ingest a placebo drink, (B) ingest a
placebo drink and perform aerobic exercise, (C) ingest a protein supplement,
and (D) ingest a protein supplement and perform aerobic exercise. Following
initiation of the hemodialysis session, arterial plasma samples will be
obtained with 30-min intervals during a 4 h period for analysis of plasma amino
acid, glucose, and insulin concentrations. In addition, spent dialysate will be
collected and glucose monitoring will be applied continuously throughout the
hemodialysis session.

The risks involved in participating in this experiment are minimal. Blood and
spent dialysate samples will be collected from the arterial blood line and
dialysate line, respectively, without extra burden or risk for the patients.
Oral food intake during hemodialysis is routine for most patients and is well
tolerated. The protein supplements are produced according to HACCP standards
and are safe for human use. Intradialytic exercise is common practice in many
hemodialysis departments, and (serious) adverse events are rarely reported.