Impairment of small intestinal protein assimilation in patients with end-stage renal disease: extending the malnutrition-inflammation-atherosclerosis concept.

BACKGROUND: Protein malnutrition is a common finding in renal disease. Recently, we showed that impaired protein assimilation (digestion and absorption) may contribute to protein malnutrition in nondiabetic patients with chronic renal failure.

OBJECTIVE: The aim of the present study was to evaluate whether these findings can be extended to the dialysis population. Moreover, relations with indexes of the malnutrition-inflammation-atherosclerosis (MIA) syndrome were investigated.

DESIGN: Protein assimilation was evaluated in 24 healthy control subjects and in 40 patients with end-stage renal disease (ESRD; 14 treated with peritoneal dialysis and 26 with hemodialysis) by means of a [13C]protein breath test, quantification of the generation rate of p-cresol, or both methods. Both approaches provide reliable information on the efficiency of protein assimilation. Breath test results were expressed as the maximum percentage recovery per hour of the administered dose of 13C (%max) and as the cumulative percentage recovery at the end of the test (%cum end). Several indexes of nutritional status, inflammation, and atherosclerosis were assessed.

RESULTS: Compared with the control subjects, ESRD patients had significantly lower breath-test derived indexes of protein assimilation [%max=3.75 +/- 0.30 compared with 4.90 +/- 0.25, P=0.006; %cum end=12.41 (5.74-23.22) compared with 16.87 (9.42-22.99), P=0.020] and a higher 24-h p-cresol generation rate corrected for dietary protein intake [3.89 (0.48-11.60) compared with 2.81 (0.21-11.20) mg p-cresol/g urea nitrogen; P=0.028]. The presence of impaired protein assimilation was associated with indexes of the MIA syndrome.

CONCLUSION: Our study provides evidence that protein assimilation is impaired in ESRD patients. Moreover, this disorder is associated with the severity of the MIA syndrome.