Protein/Fiber Index Modulates Uremic Toxin Concentrations in Hemodialysis Patients

Abstract

Background: Indoxyl sulfate (IS) and p-cresyl sulfate (PCS), two uremic toxins (UTs), are associated with increased mortality in patients with chronic kidney disease (CKD). These toxins are produced by the microbiota from the diet and excreted by the kidney. The purpose of this study was to analyze the effect of diet on IS and PCS concentration in hemodialysis (HD) patients. Methods: We performed a prospective monocentric study using a seven-day diet record and determination of serum IS and PCS levels in HD patients. We tested the association between toxin concentrations and nutritional data. Results: A total of 58/75 patients (77%) completed the diet record. Mean caloric intake was 22 ± 9.2 kcal/kg/day. The protein/fiber index was 4.9 ± 1.8. No correlation between IS or PCS concentration and protein/fiber index was highlighted. In the 18 anuric patients (31%) in whom residual renal function could not affect toxin concentrations, IS and PCS concentrations were negatively correlated with fiber intake and positively correlated with the protein/fiber index. In a multivariate analysis, IS serum concentration was positively associated with the protein/fiber index (p = 0.03). Conclusions: A low protein/fiber index is associated with low concentrations of uremic toxins in anuric HD patients. Diets with an increased fiber intake must be tested to determine whether they reduce PCS and IS serum concentrations.

A Metagenomic Approach Does Not Elucidate Uremic Toxin Levels in Hemodialysis Patients.

“…The findings of the present study, support a direct association between the dietary protein-to-fiber ratio and serum IS, consistent with prior reports. 6,42 Not unexpectedly, TMAO was also associated with protein-to-fiber ratio in this patient sample of non-vegetarians. Conversely, dietary protein-to-fiber ratio and serum level of CS trended but were not significantly associated, in contrast with previous reports in CKD patients, 7 those receiving hemodialysis, 6 and controlled feeding of healthy adults.…”

“…6,42 Not unexpectedly, TMAO was also associated with protein-to-fiber ratio in this patient sample of non-vegetarians. Conversely, dietary protein-to-fiber ratio and serum level of CS trended but were not significantly associated, in contrast with previous reports in CKD patients, 7 those receiving hemodialysis, 6 and controlled feeding of healthy adults. 43 This lack of significant effect of CS, in addition to the limitation of sample size, may be due to the generally low to moderate fiber intakes of the hemodialysis patients, i.e., an adequate level of dietary fiber substrate and perhaps decreased transit time is needed to shift from proteolytic to saccharolytic fermentation.…”

“…Evidence suggests that the dietary protein-to-fiber ratio is correlated with blood levels of uremic toxins. 6,7 Higher protein intake provides precursor aromatic amino acids for the microbial synthesis of such toxins as p-cresyl sulfate, indoxyl sulfate, and phenylacetylglutamine, increasing levels, and conversely, higher fiber intake, provides microbial-available carbohydrates that suppress proteolytic activity through various mechanisms. 8,9 However, from a clinical patient perspective, mitigation of uremic toxin production through diet modification offers considerable challenges.…”

Biotics (Pre-, Pro-, Post-) and Uremic Toxicity: Implications, Mechanisms, and Possible Therapies

“…The blood concentrations of these uremic toxins were strongly influenced by the patient’s diet, showing a significant correlation with the protein/fiber index. That is to say, to investigate the potential reduction of these uremic toxins, diets with higher fiber intake should be tested as a beneficial approach to lowering their levels and minimizing the risk of undernutrition [ 87 ].…”