Intradialytic protein ingestion and exercise do not compromise uremic toxin removal throughout hemodialysis

OBJECTIVE: Dietary protein and physical activity interventions are increasingly implemented during hemodialysis to support muscle maintenance in patients with end-stage renal disease. Though muscle maintenance is important, adequate removal of uremic toxins throughout hemodialysis is the primary concern for patients. It remains to be established whether intradialytic protein ingestion and/or exercise modulate uremic toxin removal during hemodialysis.

METHODS: We recruited 10 patients with end-stage renal disease (age: 65±16 y, BMI: 24.2±4.8 kg/m2) on chronic hemodialysis treatment to participate in this randomized crossover trial. During hemodialysis, patients were assigned to ingest 40 g protein or a non-protein placebo both at rest (PRO and PLA, respectively) and following 30 min of exercise (PRO+EX and PLA+EX, respectively). Blood and spent dialysate samples were collected throughout hemodialysis to assess reduction ratios and removal of urea, creatinine, phosphate, cystatin C, and indoxyl sulfate.

RESULTS: The reduction ratios of urea and indoxyl sulfate were higher during PLA (76±6 and 46±9%, respectively) and PLA+EX interventions (77±5 and 45±10%, respectively) when compared to PRO (72±4 and 40±8%, respectively) and PRO+EX interventions (73±4 and 43±7%, respectively; protein effect: P=0.001 and P=0.023, respectively; exercise effect: P=0.25 and P=0.52, respectively). Nonetheless, protein ingestion resulted in greater urea removal (P=0.046) during hemodialysis. Reduction ratios and removal of creatinine, phosphate, and cystatin C during hemodialysis did not differ following intradialytic protein ingestion or exercise (protein effect: P>0.05; exercise effect: P>0.05). Urea, creatinine, and phosphate removal were greater throughout the period with intradialytic exercise during PLA+EX and PRO+EX interventions when compared to the same period during PLA and PRO interventions (exercise effect: P=0.034, P=0.039, and P=0.022, respectively).

CONCLUSION: The removal of uremic toxins is not compromised by protein feeding and/or exercise implementation during hemodialysis in patients with end-stage renal disease.