Carla J. Dolenga

Is there a relationship between tryptophan dietary intake and plasma levels of indoxyl sulfate in chronic kidney disease patients on hemodialysis

INTRODUCTION Gut microbiota is involved in generation of uremic toxins in chronic kidney disease (CKD) patients on hemodialysis (HD), like indoxyl sulfate (IS) that is originated from tryptophan amino acid fermentation. OBJECTIVE To evaluate the tryptophan intake by chronic renal failure patients on HD and its possible relationship with IS plasma levels. METHODS Participated of the study 46 patients with CKD on HD regular program (56.5% men; 52.7 ± 10.3 years; 63 (32.2-118.2) months on HD; BMI 25.6 ± 4.9 kg/m2). The tryptophan intake was evaluated by a 24-hours dietary recall (R-24h) performed on 3 different days. Routine biochemical tests and anthropometric measurements were evaluated. IS plasma levels were determined by High Performance Liquid Chromatography (HPLC) with fluorescent detection and the interleukin-6 (IL-6) plasma levels by immunoenzymatic method (ELISA, Enzyme Linked Immunosorbent Assay). RESULTS The average of tryptophan intake was according to recommendation, but IS plasma levels (35.0 ± 11.9 mg/L) were elevated, however according to the EUTox values for uremic individuals. There was no correlation between the tryptophan intake and IS plasma levels. However, there was positive correlation between protein intake and tryptophan and variables used to evaluate lean body mass, and moreover, IS levels were positively associated with IL-6 (r = 0.6: p = 0.01). CONCLUSION The present study suggests that tryptophan dietary intake may not be a determinant factor to IS levels. However, it suggests that gut microbiota may play an important role in systemic inflammation in patients with CKD.

The Impact of Uremic Toxicity Induced Inflammatory Response on the Cardiovascular Burden in Chronic Kidney Disease

Uremic toxin (UT) retention in chronic kidney disease (CKD) affects biological systems. We aimed to identify the associations between UT, inflammatory biomarkers and biomarkers of the uremic cardiovascular response (BUCVR) and their impact on cardiovascular status as well as their roles as predictors of outcome in CKD patients. CKD patients stages 3, 4 and 5 (n = 67) were recruited and UT (indoxyl sulfate/IS, p-cresil sulfate/pCS and indole-3-acetic acid/IAA); inflammatory biomarkers [Interleukin-6 (IL-6), high sensitivity C reactive protein (hsCRP), monocyte chemoattractant protein-1 (MCP-1), soluble vascular adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1) and soluble Fas (sFas)] and BUCVRs [soluble CD36 (sCD36), soluble receptor for advanced glycation end products (sRAGE), fractalkine] was measured. Patients were followed for 5.2 years and all causes of death was used as the primary outcome. Artery segments collected at the moment of transplantation were used for the immunohistochemistry analysis in a separate cohort. Estimated glomerular filtration rate (eGFR), circulating UT, plasma biomarkers of systemic and vascular inflammation and BUCVR were strongly interrelated. Patients with plaque presented higher signs of UT-induced inflammation and arteries from CKD patients presented higher fractalkine receptor (CX3CR1) tissue expression. Circulating IS (p = 0.03), pCS (p = 0.007), IL-6 (p = 0.026), sFas (p = 0.001), sCD36 (p = 0.01) and fractalkine (p = 0.02) were independent predictors of total mortality risk in CKD patients. Our results reinforce the important role of uremic toxicity in the pathogenesis of cardiovascular disease (CVD) in CKD patients through an inflammatory pathway.

Uremia Impacts VE-Cadherin and ZO-1 Expression in Human Endothelial Cell-to-Cell Junctions

Endothelial dysfunction in uremia can result in cell-to-cell junction loss and increased permeability, contributing to cardiovascular diseases (CVD) development. This study evaluated the impact of the uremic milieu on endothelial morphology and cell junction’s proteins. We evaluated (i) serum levels of inflammatory biomarkers in a cohort of chronic kidney disease (CKD) patients and the expression of VE-cadherin and Zonula Occludens-1 (ZO-1) junction proteins on endothelial cells (ECs) of arteries removed from CKD patients during renal transplant; (ii) ECs morphology in vitro under different uremic conditions, and (iii) the impact of uremic toxins p-cresyl sulfate (PCS), indoxyl sulfate (IS), and inorganic phosphate (Pi) as well as of total uremic serum on VE-cadherin and ZO-1 gene and protein expression in cultured ECs. We found that the uremic arteries had lost their intact and continuous endothelial morphology, with a reduction in VE-cadherin and ZO-1 expression. In cultured ECs, both VE-cadherin and ZO-1 protein expression decreased, mainly after exposure to Pi and uremic serum groups. VE-cadherin mRNA expression was reduced while ZO-1 was increased after exposure to PCS, IS, Pi, and uremic serum. Our findings show that uremia alters cell-to-cell junctions leading to an increased endothelial damage. This gives a new perspective regarding the pathophysiological role of uremia in intercellular junctions and opens new avenues to improve cardiovascular outcomes in CKD patients.

Effect of prebiotic (fructooligosaccharide) on uremic toxins of chronic kidney disease patients: a randomized controlled trial

Background Microbial-derived uremic toxins, p-cresyl sulfate (PCS), indoxyl sulfate (IS) and indole 3-acetic acid (IAA), have been associated with the burden of chronic kidney disease (CKD). Prebiotics have emerged as an alternative to modulate the gut environment and to attenuate toxin production. This trial aims to investigate the effect of a prebiotic fructooligosaccharide (FOS) on uremic toxins of non-dialysis-dependent CKD (NDD-CKD) patients. Methods A double-blind, placebo-controlled, randomized trial was conducted for 3 months. In all, 50 nondiabetic NDD-CKD patients [estimated glomerular filtration rate (eGFR) <45 mL/min/1.73 m2], aged 18-80 years, were allocated to prebiotic (FOS, 12 g/day) or placebo (maltodextrin, 12 g/day) groups. Primary outcomes were changes in serum (total and free) and urinary (total) PCS. Secondary outcomes included changes in IS, IAA, serum markers of intestinal permeability (zonulin), gut-trophic factors (epidermal growth factor and glucagon-like peptide-2), eGFR, inflammation (high sensitive c-reactive protein and interleukin-6), homeostatic model assessment-insulin resistance, lipid profile and gastrointestinal symptoms. Results From 50 participants (54% men, 57.3 ± 14.6 years and eGFR 21.4 ± 7.6 mL/min/1.73 m2), 46 completed the follow-up. No changes in dietary intake or gastrointestinal symptoms were observed. There was a trend in the difference of serum total ΔPCS (treatment effect adjusted for baseline levels: -12.4 mg/L; 95% confidence interval (-5.6 to 0.9 mg/L; P = 0.07) and serum-free Δ%PCS [intervention -8.6 (-41.5 to 13.9%) versus placebo 3.5 (-28.8 to 85.5%); P = 0.07] between the groups. The trend in the difference of serum total ΔPCS was independent of eGFR and dietary protein:fiber ratio intake. No difference was found in urinary PCS. Aside from the decreased high-density lipoprotein cholesterol in the intervention, no differences were observed in the change of IS, IAA or other secondary outcome between the groups. Conclusions Our result suggests the potential of FOS in reducing serum total and free PCS in nondiabetic NDD-CKD patients.