Effect of fructooligosaccharide on endothelial function in CKD patients: a randomized controlled trial.

BACKGROUND: Microbiota-derived uremic toxins have been associated with inflammation that could corroborate with endothelial dysfunction (ED) and increase cardiovascular risk in patients with chronic kidney disease (CKD). This trial aimed to evaluate the effect of the prebiotic fructooligosaccharide (FOS) on endothelial function and arterial stiffness in nondialysis CKD patients. METHODS: In a double-blind controlled trial, 46 nondiabetic CKD patients were randomized to receive 12 g/day of FOS or placebo (maltodextrin) for 3 months. Total p-cresyl sulfate (PCS) and indoxyl sulfate by high-performance liquid chromatography, urinary trimethylamine N-oxide by mass spectrometry, C-reactive protein, interleukin-6 (IL-6), serum nitric oxide and stroma-derived factor-1 alfa were measured at baseline and at the end of follow-up; endothelial function was assessed through flow-mediated dilatation (FMD) and arterial stiffness by pulse wave velocity (PWV). RESULTS: The mean (± standard deviation) age of the study participants was 57.6 ± 14.4 years, with an estimated glomerular filtration rate of 21.3 ± 7.3 mL/min/1.73 m2. During the follow-up, regarding the inflammatory markers and uremic toxins, there was a significant decrease in IL-6 levels (3.4 ± 2.1 pg/mL versus 2.6 ± 1.4 pg/mL; P = 0.04) and a trend toward PCS reduction (55.4 ± 38.1 mg/L versus 43.1 ± 32.4 mg/L, P = 0.07) only in the prebiotic group. Comparing both groups, there was no difference in FMD and PWV. In an exploratory analysis, including a less severe ED group of patients (FMD ≥2.2% at baseline), FMD remained stable in the prebiotic group, while it decreased in the placebo group (group effect P = 0.135; time effect P = 0.012; interaction P = 0.002). CONCLUSIONS: The prebiotic FOS lowered circulating levels of IL-6 in CKD patients and preserved endothelial function only in those with less damaged endothelium. No effect of FOS in arterial stiffness was observed.

Higher Frequency of Fruit Intake Is Associated With a Lower Risk of Constipation in Hemodialysis Patients: A Multicenter Study.

OBJECTIVES: Constipation is a multifactorial gastrointestinal disorder commonly found in hemodialysis (HD) patients. In this multicenter cross-sectional study, we aimed to evaluate the prevalence and factors associated with constipation, including the frequency of dietary fiber intake. METHODS: HD patients from 4 dialysis clinics were invited. Participants answered a questionnaire which included Roma IV criteria to assess constipation status, use of medications, and lifestyle habits. A food frequency questionnaire with 7 response options on the main dietary fiber sources (fruits, vegetables, legumes, whole grains, and seeds) was also applied. Answers were transformed into a score to estimate the weekly intake frequency, and every score point corresponded to one time per week. Demographical and laboratory data were obtained from medical records. Univariate analysis was used to compare participants according to constipation status, and variables with P < .20 were included in the regression analysis model. RESULTS: Three hundred five HD patients were included (male: 51%; age: 52.2 ± 14.7 years old; HD vintage: 46 (19-82) months). Ninety-three participants had constipation (30.5%). Median (interquartile) food frequency questionnaire scores were as follows: fruits: 6 (2-14); vegetables: 6 (3-10); legumes: 3 (1-7); whole grain: 0 (0-1); and seeds: 0 (0-0). In univariate analysis, participants with constipation were significantly older, had lower literacy, higher prevalence of diabetes, and lower total beverage intake. The logistic regression analysis model also included body mass index, wheelchair need, sedentarism, fruits score, and seeds score (all with P < .20 in the univariate analysis). The independent predictors of constipation were diabetes (odds ratio = 1.96, 95% confidence interval 1.07-3.6, P = .03) and fruits intake score (odds ratio = 0.95, 95% confidence interval 0.91-0.99, P = .04). CONCLUSIONS: Almost one-third of the participants had constipation. The independent determinants of constipation were diabetes and lower frequency of fruit intake. Nutritional counseling to increase fiber intake can potentially decrease the prevalence of constipation in this population.

Does dietary potassium intake associate with hyperkalemia in patients with chronic kidney disease?

BACKGROUND: Dietary potassium restriction is a strategy to control hyperkalemia in chronic kidney disease (CKD). However, hyperkalemia may result from a combination of clinical conditions. This study aimed to investigate whether dietary potassium or the intake of certain food groups associate with serum potassium in the face of other risk factors. METHODS: We performed a cross-sectional analysis including a nondialysis-dependent CKD (NDD-CKD) cohort and a hemodialysis (HD) cohort. Dietary potassium intake was assessed by 3-day food records. Underreporters with energy intake lower than resting energy expenditure were excluded. Hyperkalemia was defined as serum potassium >5.0 mEq/L. RESULTS: The NDD-CKD cohort included 95 patients {median age 67 [interquartile range (IQR) 55-73] years, 32% with diabetes mellitus (DM), median estimated glomerular filtration rate 23 [IQR 18-29] mL/min/1.73 m2} and the HD cohort included 117 patients [median age 39 (IQR 18-67) years, 50% with DM]. In NDD-CKD, patients with hyperkalemia (36.8%) exhibited lower serum bicarbonate and a tendency for higher serum creatinine, a higher proportion of DM and the use of renin-angiotensin-aldosterone system blockers, but lower use of sodium bicarbonate supplements. No association was found between serum and dietary potassium (r = 0.01; P = 0.98) or selected food groups. Conditions associated with hyperkalemia in multivariable analysis were DM {odds ratio [OR] 3.55 [95% confidence interval (CI) 1.07-11.72]} and metabolic acidosis [OR 4.35 (95% CI 1.37-13.78)]. In HD, patients with hyperkalemia (50.5%) exhibited higher serum creatinine and blood urea nitrogen and lower malnutrition inflammation score and a tendency for higher dialysis vintage and body mass index. No association was found between serum and potassium intake (r = -0.06, P = 0.46) or food groups. DM [OR 4.22 (95% CI 1.31-13.6)] and serum creatinine [OR 1.50 (95% CI 1.24-1.81)] were predictors of hyperkalemia in multivariable analyses. CONCLUSIONS: Dietary potassium was not associated with serum potassium or hyperkalemia in either NDD-CKD or HD patients. Before restricting dietary potassium, the patient's intake of potassium should be carefully evaluated and other potential clinical factors related to serum potassium balance should be considered in the management of hyperkalemia in CKD.

Prebiotic, Probiotic, and Synbiotic Supplementation in Chronic Kidney Disease: A Systematic Review and Meta-analysis.

OBJECTIVE: Gut dysbiosis has been implicated in the pathogenesis of chronic kidney disease (CKD). Restoring gut microbiota with prebiotic, probiotic, and synbiotic supplementation has emerged as a potential therapeutic intervention but has not been systematically evaluated in the CKD population. DESIGN AND METHODS: This is a systematic review. A structured search of MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and the International Clinical Trials Register Search Portal was conducted for articles published since inception until July 2017. Included studies were randomized controlled trials investigating the effects of prebiotic, probiotic, and/or synbiotic supplementation (>1 week) on uremic toxins, microbiota profile, and clinical and patient-centered outcomes in adults and children with CKD. RESULTS: Sixteen studies investigating 645 adults met the inclusion criteria; 5 investigated prebiotics, 6 probiotics, and 5 synbiotics. The quality of the studies (Grades of Recommendation, Assessment, Development and Evaluation) ranged from moderate to very low. Prebiotic, probiotic, and synbiotic supplementation may have led to little or no difference in serum urea (9 studies, 345 participants: mean difference [MD] -0.30 mmol/L, 95% confidence interval [CI] -2.20 to 1.61, P = .76, I2 = 53%), indoxyl sulfate (4 studies, 144 participants: MD -0.02 mg/dL, 95% CI -0.09 to 0.05, P = .61, I2 = 0%), and p-cresyl sulfate (4 studies, 144 participants: MD -0.13 mg/dL, 95% CI -0.41 to 0.15, P = .35, I2 = 0%). Prebiotic supplementation may have slightly reduced serum urea concentration (4 studies, 105 participants: MD -2.23 mmol/L, 95% CI -3.83 to -0.64, P = .006, I2 = 11). Of the 2 studies investigating microbiota changes, synbiotic interventions significantly increased Bifidobacterium. Supplement effects on clinical outcomes were uncertain. CONCLUSIONS: There is limited evidence to support the use of prebiotics, probiotics, and/or synbiotics in CKD management.