Effects of synbiotic supplementation on microbiota-derived protein-bound uremic toxins, systemic inflammation, and biochemical parameters in patients on hemodialysis: A double-blind, placebo-controlled, randomized clinical trial

Efficacy of probiotics/synbiotics supplementation in patients with chronic kidney disease: a systematic review and meta-analysis of randomized controlled trials

Background

Chronic kidney disease (CKD) is a serious and steadily growing health problem worldwide. Probiotic and synbiotic supplementation are expected to improve kidney function in CKD patients by altering imbalanced intestinal flora, regulating microbiota metabolites, modulating the brain-gut axis, and reducing inflammation.

Objectives

Our aim is to report the latest and largest pooled analyses and evidence updates to explore whether probiotic and synbiotic have beneficial effects on renal function and general conditions in patients with CKD.

Methods

We conducted a systematic literature search using PubMed, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials from inception until 1 December 2023. Eligible literatures were screened according to inclusion and exclusion criteria, data were extracted, and a systematic review and meta-analysis was performed. Measurements included renal function-related markers, inflammatory markers, uremic toxins, lipid metabolism-related markers and electrolytes levels.

Results

Twenty-one studies were included. The results showed that probiotic/synbiotic significantly reduced blood urea nitrogen (BUN) (standardized mean difference (SMD), -0.23, 95% confidence interval (CI) -0.41, -0.04; p = 0.02, I2 = 10%) and lowered c-reactive protein level (CRP) (SMD: -0.34; 95% CI: -0.62, -0.07; p = 0.01, I2 = 37%) in CKD patients, compared with the control group.

Conclusion

In summary, probiotic/synbiotic supplementation seems to be effective in improving renal function indices and inflammation indices in CKD patients. Subgroup analyses suggested that longer-term supplementation is more favorable for CKD patients, but there is a high degree of heterogeneity in the results of partial subgroup analyses. The efficacy of probiotic/synbiotic in treating CKD needs to be supported by more evidence from large-scale clinical studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024526836, Unique identifier: CRD42024526836.

A comprehensive review of synbiotics: an emerging paradigm in health promotion and disease management

Synbiotics are complex preparations of prebiotics that can be selectively utilized by live microorganisms to improve host health. Synbiotics are divided into complementary synbiotics, which consist of probiotics and prebiotics with independent functions, and synergistic synbiotics, which consist of prebiotics that are selectively used by gut microorganisms. Complementary synbiotics used in human clinical trials include Lactobacillus spp. and Bifidobacterium spp. as probiotics, and fructooligosaccharides, galactooligosaccharides, and inulin as prebiotics. Over the past five years, synbiotics have been most commonly used in patients with metabolic disorders, including obesity, and immune and gastrointestinal disorders. Several studies have observed alterations in the microbial community; however, these changes did not lead to significant improvements in disease outcomes or biochemical and hematological markers. The same synbiotics have been applied to individuals with different gut environments. As a result, even with the same synbiotics, there are non-responders who do not respond to the applied synbiotics due to the different intestinal environment for each individual. Therefore, to obtain meaningful results, applying different synbiotics depending on the individual is necessary. Synergistic synbiotics are one solution to circumvent this problem, as they combine elements that can effectively improve health, even in non-responders. This review aims to explain the concept of synbiotics, highlight recent human clinical trials, and explore the current state of research on synergistic synbiotics.

A Historical Perspective on Uremia and Uremic Toxins

Uremia, also known as uremic syndrome, refers to the clinical symptoms in the final stage of renal failure. The definition of the term has changed over time due to an improved comprehension of the kidney's function and the advancement of dialysis technology. Here, we aim to present an overview of the various concepts that have developed regarding uremia throughout the years. We provide a comprehensive review of the historical progression starting from the early days of Kolff and his predecessors, continuing with the initial research conducted by Niwa et al., and culminating in the remote sensing hypothesis of Nigam. Additionally, we explore the subsequent investigation into the function of these toxins as signaling molecules in various somatic cells.

Effects of Probiotic-Enriched Minas Cheese (Lactobacillus acidophilus La-05) on Cardiovascular Parameters in 5/6 Nephrectomized Rats

Dairy foods have become an interest in chronic kidney disease (CKD) due to their nutritional profile, which makes them a good substrate for probiotics incorporation. This study evaluated the effect of probiotic-enriched Minas cheese with Lactobacillus acidophilus La-05 in an experimental rat model for CKD on cardiac, inflammatory, and oxidative stress parameters. Male Wistar rats were divided into 4 groups (n = 7/group): 5/6 nephrectomy + conventional Minas cheese (NxC); 5/6 nephrectomy + probiotic Minas cheese (NxPC); Sham + conventional Minas cheese (ShamC); Sham + probiotic Minas cheese (ShamPC). Offering 20 g/day of Minas cheese with Lact. acidophilus La-05 (108-109 log CFU/g) for 6 weeks. The cardiomyocyte diameter was determined. Superoxide dismutase (SOD) activity in plasma, heart, kidney, and colon tissue was performed. At the end of supplementation, no significant changes in lipid profile and renal parameters were found. The NxPC group showed a decrease in cardiomyocyte diameter compared to the NxC group (16.99 ± 0.85 vs. 19.05 ± 0.56 μm, p = 0.0162); also they showed reduced plasmatic SOD activity (502.8 ± 49.12 vs. 599.4 ± 94.69 U/mL, p < 0.0001). In summary, probiotic-enriched Minas cheese (Lact. acidophilus La-05) consumption suggests a promisor cardioprotective effect and was able to downregulate SOD activity in a rat model of CKD.

Synbiotics, prebiotics and probiotics for people with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a major public health problem affecting 13% of the global population. Prior research has indicated that CKD is associated with gut dysbiosis. Gut dysbiosis may lead to the development and/or progression of CKD, which in turn may in turn lead to gut dysbiosis as a result of uraemic toxins, intestinal wall oedema, metabolic acidosis, prolonged intestinal transit times, polypharmacy (frequent antibiotic exposures) and dietary restrictions used to treat CKD. Interventions such as synbiotics, prebiotics, and probiotics may improve the balance of the gut flora by altering intestinal pH, improving gut microbiota balance and enhancing gut barrier function (i.e. reducing gut permeability).

OBJECTIVES

This review aimed to evaluate the benefits and harms of synbiotics, prebiotics, and probiotics for people with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 9 October 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) measuring and reporting the effects of synbiotics, prebiotics, or probiotics in any combination and any formulation given to people with CKD (CKD stages 1 to 5, including dialysis and kidney transplant). Two authors independently assessed the retrieved titles and abstracts and, where necessary, the full text to determine which satisfied the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Data extraction was independently carried out by two authors using a standard data extraction form. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous outcomes. The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. Data entry was carried out by one author and cross-checked by another. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Forty-five studies (2266 randomised participants) were included in this review. Study participants were adults (two studies in children) with CKD ranging from stages 1 to 5, with patients receiving and not receiving dialysis, of whom half also had diabetes and hypertension. No studies investigated the same synbiotic, prebiotic or probiotic of similar strains, doses, or frequencies. Most studies were judged to be low risk for selection bias, performance bias and reporting bias, unclear risk for detection bias and for control of confounding factors, and high risk for attrition and other biases. Compared to prebiotics, it is uncertain whether synbiotics improve estimated glomerular filtration rate (eGFR) at four weeks (1 study, 34 participants: MD -3.80 mL/min/1.73 m², 95% CI -17.98 to 10.38), indoxyl sulfate at four weeks (1 study, 42 participants: MD 128.30 ng/mL, 95% CI -242.77 to 499.37), change in gastrointestinal (GI) upset (borborymgi) at four weeks (1 study, 34 participants: RR 15.26, 95% CI 0.99 to 236.23), or change in GI upset (Gastrointestinal Symptom Rating Scale) at 12 months (1 study, 56 participants: MD 0.00, 95% CI -0.27 to 0.27), because the certainty of the evidence was very low. Compared to certain strains of prebiotics, it is uncertain whether a different strain of prebiotics improves eGFR at 12 weeks (1 study, 50 participants: MD 0.00 mL/min, 95% CI -1.73 to 1.73), indoxyl sulfate at six weeks (2 studies, 64 participants: MD -0.20 μg/mL, 95% CI -1.01 to 0.61; I² = 0%) or change in any GI upset, intolerance or microbiota composition, because the certainty of the evidence was very low. Compared to certain strains of probiotics, it is uncertain whether a different strain of probiotic improves eGFR at eight weeks (1 study, 30 participants: MD -0.64 mL/min, 95% CI -9.51 to 8.23; very low certainty evidence). Compared to placebo or no treatment, it is uncertain whether synbiotics improve eGFR at six or 12 weeks (2 studies, 98 participants: MD 1.42 mL/min, 95% CI 0.65 to 2.2) or change in any GI upset or intolerance at 12 weeks because the certainty of the evidence was very low. Compared to placebo or no treatment, it is uncertain whether prebiotics improves indoxyl sulfate at eight weeks (2 studies, 75 participants: SMD -0.14 mg/L, 95% CI -0.60 to 0.31; very low certainty evidence) or microbiota composition because the certainty of the evidence is very low. Compared to placebo or no treatment, it is uncertain whether probiotics improve eGFR at eight, 12 or 15 weeks (3 studies, 128 participants: MD 2.73 mL/min, 95% CI -2.28 to 7.75; I² = 78%), proteinuria at 12 or 24 weeks (1 study, 60 participants: MD -15.60 mg/dL, 95% CI -34.30 to 3.10), indoxyl sulfate at 12 or 24 weeks (2 studies, 83 participants: MD -4.42 mg/dL, 95% CI -9.83 to 1.35; I² = 0%), or any change in GI upset or intolerance because the certainty of the evidence was very low. Probiotics may have little or no effect on albuminuria at 12 or 24 weeks compared to placebo or no treatment (4 studies, 193 participants: MD 0.02 g/dL, 95% CI -0.08 to 0.13; I² = 0%; low certainty evidence). For all comparisons, adverse events were poorly reported and were minimal (flatulence, nausea, diarrhoea, abdominal pain) and non-serious, and withdrawals were not related to the study treatment.

AUTHORS' CONCLUSIONS

We found very few studies that adequately test biotic supplementation as alternative treatments for improving kidney function, GI symptoms, dialysis outcomes, allograft function, patient-reported outcomes, CVD, cancer, reducing uraemic toxins, and adverse effects. We are not certain whether synbiotics, prebiotics, or probiotics are more or less effective compared to one another, antibiotics, or standard care for improving patient outcomes in people with CKD. Adverse events were uncommon and mild.

Food-Derived Uremic Toxins in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have a higher cardiovascular risk compared to the average population, and this is partially due to the plasma accumulation of solutes known as uremic toxins. The binding of some solutes to plasma proteins complicates their removal via conventional therapies, e.g., hemodialysis. Protein-bound uremic toxins originate either from endogenous production, diet, microbial metabolism, or the environment. Although the impact of diet on uremic toxicity in CKD is difficult to quantify, nutrient intake plays an important role. Indeed, most uremic toxins are gut-derived compounds. They include Maillard reaction products, hippurates, indoles, phenols, and polyamines, among others. In this review, we summarize the findings concerning foods and dietary components as sources of uremic toxins or their precursors. We then discuss their endogenous metabolism via human enzyme reactions or gut microbial fermentation. Lastly, we present potential dietary strategies found to be efficacious or promising in lowering uremic toxins plasma levels. Aligned with current nutritional guidelines for CKD, a low-protein diet with increased fiber consumption and limited processed foods seems to be an effective treatment against uremic toxins accumulation.

Natural products from plants and microorganisms: Novel therapeutics for chronic kidney disease via gut microbiota regulation

Dysbiosis of gut microbiota plays a fundamental role in the pathogenesis and development of chronic kidney disease (CKD) and its complications. Natural products from plants and microorganisms can achieve recognizable improvement in renal function and serve as an alternative treatment for chronic kidney disease patients with a long history, yet less is known on its beneficial effects on kidney injury by targeting the intestinal microbiota. In this review, we summarize studies on the effects of natural products from plants and microorganisms, including herbal medicines and their bioactive extracts, polysaccharides from plants and microorganisms, and phytochemicals, on the prevention and treatment of chronic kidney disease through targeting gut microflora. We describe the strategies of these anti-CKD effects in animal experiments including remodulation of gut microbiota structure, reduction of uremic toxins, enhancement of short-chain fatty acid (SCFA) production, regulation of intestinal inflammatory signaling, and improvement in intestinal integrity. Meanwhile, the clinical trials of different natural products in chronic kidney disease clinical practice were also analyzed and discussed. These provide information to enable a better understanding of the renoprotective effects of these effective natural products from plants and microorganisms in the treatment of chronic kidney disease. Finally, we propose the steps to prove the causal role of the intestinal microflora in the treatment of chronic kidney disease by natural products from plants and microorganisms. We also assess the future perspective that natural active products from plants and microorganisms can beneficially delay the onset and progression of kidney disease by targeting the gut flora and highlight the remaining challenges in this area. With the continuous deepening of studies in recent years, it has been proved that gut microbiota is a potential target of natural active products derived from plants and microorganisms for chronic kidney disease treatment. Fully understanding the functions and mechanisms of gut microbiota in these natural active products from plants and microorganisms is conducive to their application as an alternative therapeutic in the treatment of chronic kidney disease.

Probiotics, Prebiotics, and Synbiotics for Patients on Dialysis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

The current systematic review and meta-analysis investigated the effects of probiotic, prebiotic, and synbiotic administration on inflammation, metabolic parameters, nutritional status, and uremic toxin in dialysis patients.

METHODS

Up to June 2021, publications were searched in Cochrane Library, PubMed, EMBASE, and Web of Science databases. The protocol was submitted to the International Prospective Register of Systematic Reviews and was approved.

RESULTS

This meta-analysis included 18 randomized controlled trials which were eligible. This meta-analysis discovered that probiotic, prebiotic, and synbiotic supplements could reduce C-reactive protein (standardized mean difference (SMD), -0.38; 95% confidence interval (CI), -0.68 to -0.08; P = .01), interleukin 6 (SMD, -0.48; 95% CI, -0.76 to -0.20; P = .00), and indoxyl sulfate (SMD, -0.24; 95% CI, -0.48 to -0.01; P = .045) and increase high-density lipoprotein cholesterol (SMD, 0.25; 95% CI, 0.03 to 0.46; P = .025) compared with the control group but had no significant influence on tumor necrosis factor α, albumin, hemoglobin, triglyceride, total cholesterol, low-density lipoprotein cholesterol, calcium, phosphorus, uric acid, or p-cresyl sulfate in dialysis patients.

CONCLUSIONS

Probiotic, prebiotic, and synbiotic administration could reduce C-reactive protein, interleukin 6, and indoxyl sulfate and increase high-density lipoprotein cholesterol in dialysis patients. To better examine the impact, large-scale, long-term, controlled diets and well-designed randomized controlled trials are needed.

p-Cresyl sulfate predicts clinical outcomes in sustained peritoneal dialysis: a 5-year follow-up cohort study and meta-analysis

Background

The impact of p-cresyl sulfate (PCS) and indoxyl sulfate (IS) on the prognosis of patients with uremia remains controversial. We performed a prospective study on peritoneal dialysis (PD) to investigate the relationship between PCS or IS levels with clinical outcomes.

Methods

This prospective cohort study investigated the association of serum PCS and IS with clinical outcomes in patients undertaking PD. We performed a correlations analysis to explore the influencing factors of PCS an IS. Meta-analysis was conducted to objectively evaluate the prognostic effects of PCS and IS on different stages of CKD patients.

Results

A total of 127 patients were enrolled consecutively and followed with an average period of 51.3 months. Multivariate Cox regression showed that serum total PCS not only contributed to the occurrence of PD failure event (HR: 1.05, 95% CI = 1.02 to 1.07, p < 0.001), but also increased the risk of cardiovascular event (HR: 1.08, 95% CI = 1.04 to 1.13, p < 0.001) and PD-associated peritonitis (HR: 1.04, 95% CI = 1.02 to 1.08, p = 0.001). Dividing the total PCS level by 18.99 mg/L, which was calculated from the best cutoff value of the ROC curve, patients with total PCS higher than 18.99 mg/L had worse prognosis. Meta-analysis confirmed its value in cardiovascular event in PD.

Conclusion

The serum total PCS concentration was a detrimental factor for higher PD failure event, cardiovascular event, and PD-associated peritonitis. It could be used as an innovative marker in predicting poor clinical outcome in PD.

Effectiveness of Microecological Preparations for Improving Renal Function and Metabolic Profiles in Patients With Chronic Kidney Disease

Background

Determining whether microecological preparations, including probiotics, prebiotics, and synbiotics, are beneficial for patients with chronic kidney disease (CKD) has been debated. Moreover, determining which preparation has the best effect remains unclear. In this study, we performed a network meta-analysis of randomized clinical trials (RCTs) to address these questions.

Methods

MEDLINE, EMBASE, PubMed, Web of Science, and the Cochrane Central Register of Controlled Trials were searched. Eligible RCTs with patients with CKD who received intervention measures involving probiotics, prebiotics, and/or synbiotics were included. The outcome indicators included changes in renal function, lipid profiles, inflammatory factors, and oxidative stress factors.

Results

Twenty-eight RCTs with 1,373 patients were ultimately included. Probiotics showed greater effect in lowering serum creatinine [mean difference (MD) -0.21, 95% confidence interval (CI) -0.34, -0.09] and triglycerides (MD -9.98, 95% CI -19.47, -0.49) than the placebo, with the largest surface area under the cumulative ranking curve, while prebiotics and synbiotics showed no advantages. Probiotics were also able to reduce malondialdehyde (MDA) (MD -0.54, 95% CI -0.96, -0.13) and increase glutathione (MD 72.86, 95% CI 25.44, 120.29). Prebiotics showed greater efficacy in decreasing high-sensitivity C-reactive protein (MD -2.06, 95% CI -3.79, -0.32) and tumor necrosis factor-α (MD -2.65, 95% CI -3.91, -1.39). Synbiotics showed a partially synergistic function in reducing MDA (MD -0.66, 95% CI -1.23, -0.09) and high-sensitivity C-reactive protein (MD -2.01, 95% CI -3.87, -0.16) and increasing total antioxidant capacity (MD 145.20, 95% CI 9.32, 281.08).

Conclusion

The results indicated that microbial supplements improved renal function and lipid profiles and favorably affected measures of oxidative stress and inflammation in patients with CKD. After thorough consideration, probiotics provide the most comprehensive and beneficial effects for patients with CKD and might be used as the best choice for microecological preparations.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022295497, PROSPERO 2022, identifier: CRD42022295497.

Effects of Microbiota-Driven Therapy on Circulating Indoxyl Sulfate and P-Cresyl Sulfate in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Indoxyl sulfate (IS) and p-cresyl sulfate (PCS), protein-bound uremic toxins, exacerbate the deterioration of renal function and increase the risk of cardiovascular events in chronic kidney disease (CKD) patients. The effects of microbiota-driven therapy (probiotics, prebiotics, or synbiotics) on decreasing circulating IS and PCS concentrations are controversial; thus, we performed the present systematic review and meta-analysis to assess the effects of microbiota-driven therapy on circulating IS and PCS concentrations in CKD patients. PubMed, EMBASE, and Cochrane Library databases were systematically searched from inception to 22 July, 2021, and randomized controlled trials (RCTs) investigating the effects of microbiota-driven therapy on circulating IS and PCS concentrations in CKD patients were included. In all, 14 RCTs with 513 participants were eligible for the meta-analysis. The effects of microbiota-driven therapy on the circulating IS and PCS concentrations were evaluated with weighted mean differences (WMDs) measured by a fixed-effects model or a random-effects model. Compared with placebo, microbiota-driven therapy had no statistically significant effect on the circulating IS concentration (WMD: -1.64 mg/L; 95% CI: -3.46, 0.18 mg/L; P = 0.077) but it decreased the circulating PCS concentration (WMD: -2.42 mg/L; 95% CI: -3.81, -1.04 mg/L; P = 0.001). In the subgroup analyses, prebiotic (n = 6) and synbiotic (n = 3) supplementation significantly decreased the circulating PCS concentration, whereas probiotic (n = 3) supplementation did not. Meta-regression showed that the effects of microbiota-driven therapy were not associated with the supplementation time or the year of publication. Moreover, there was no significant evidence of publication bias. This review found that microbiota-driven therapy decreased the circulating PCS concentration in CKD patients. Additional large, well-designed RCTs with improved methodology and reporting are necessary to assess the effects of microbiota-driven therapy on circulating IS and PCS concentrations in the long term. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42021269146.

Probiotics, Prebiotics, and Synbiotics Improve Uremic, Inflammatory, and Gastrointestinal Symptoms in End-Stage Renal Disease With Dialysis: A Network Meta-Analysis of Randomized Controlled Trials

Background

Probiotics, prebiotics, and synbiotics are three different supplements to treat end stage renal disease (ESRD) patients by targeting gut bacteria. The comprehensive comparison of the effectiveness of different supplements are lacking.

Objectives

The purpose of this network meta-analysis (NMA) is to assess and rank the efficacy of probiotics, prebiotics, and synbiotics on inflammatory factors, uremic toxins, and gastrointestinal symptoms (GI symptoms) in ESRD patients undergoing dialysis.

Methods

Randomized clinical trials were searched from the PubMed, Embase, and Cochrane Register of Controlled Trials databases, from their inception until 4 September 2021. Random-effect model were used to obtain all estimated outcomes in network meta-analysis (NMA). Effect estimates were presented as mean differences (Mean ± SD) with 95% confidence interval (CI). The comprehensive effects of all treatments were ranked by the surface under the cumulative ranking (SUCRA) probabilities.

Results

Twenty-five studies involved 1,106 participants were included. Prebiotics were superior in decreasing Interleukin-6 (IL-6; SMD –0.74, 95% CI [–1.32, –0.16]) and tumor-necrosis factor-α (TNF-α; SMD –0.59, 95% CI [–1.09, –0.08]), synbiotics were more effective in declining C-reactive protein (CRP; SMD –0.69, 95% CI [–1.14, –0.24]) and endotoxin (SMD –0.83, 95% CI [–1.38, –0.27]). Regarding uremic toxins, prebiotics ranked highest in reducing indoxyl sulfate (IS; SMD –0.43, 95% CI [–0.81, –0.05]), blood urea nitrogen (BUN; SMD –0.42, 95% CI [–0.78, –0.06]), and malondialdehyde (MDA; SMD –1.88, 95% CI [–3.02, –0.75]). Probiotics were rated as best in alleviating GI symptoms (SMD: –0.52, 95% CI [–0.93, –0.1]).

Conclusion

Our research indicated prebiotics were more effective in declining IL-6, TNF-α, IS, MDA, and BUN, synbiotics lowering CRP and endotoxin significantly, and probiotics were beneficial for alleviating GI symptoms, which may contribute to better clinical decisions. This study was registered in PROSPERO (Number: CRD42021277056).

Systematic Review Registration

[http://www.crd.york.ac.uk/PROSPERO], identifier [CRD42021277056].

Nutrition, Immunology, and Kidney: Looking Beyond the Horizons

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is epidemic throughout the word. Despite various novel therapeutic opportunities, CKD is still associated with high morbidity and mortality. In CKD, patient's chronic inflammation is frequent and related with adverse outcomes. Both innate and adaptive immunity are dysfunctional in CKD. Therefore, it is plausible to interfere with dysfunctional immunity in these patients. In the current review, we present the updated experimental and clinical data summarizing the effects of nutritional interventions including natural products and dietary supplements on immune dysfunction in the context of CKD.

RECENT FINDINGS

Nutritional interventions including natural products and dietary supplements (e.g., curcumin, sulforaphane, resistant starch, anthocyanin, chrysin, short chain fatty acids, fish oil resistant starch) slow down the inflammation by at least 6 mechanisms: (i) decrease nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB); (ii) decrease NLR family pyrin domain containing 3 (NLRP3); (iii) decrease interleukin-1 (IL-1), decrease interleukin-6 (IL-6) secretion; (iv) decrease polymorphonuclear priming); (v) promote anti-inflammatory pathways (nuclear factor-erythroid factor 2-related factor 2 (NFR2); (vi) increase T regulatory (Tregs) cells). Natural products and dietary supplements may provide benefit in terms of kidney health. By modulation of nutritional intake, progression of CKD may be delayed.

Effects of prebiotic oligofructose-enriched inulin on gut-derived uremic toxins and disease progression in rats with adenine-induced chronic kidney disease

Recent studies suggest that dysbiosis in chronic kidney disease (CKD) increases gut-derived uremic toxins (GDUT) generation, leads to systemic inflammation, reactive oxygen species generation, and poor prognosis. This study aimed to investigate the effect of oligofructose-enriched inulin supplementation on GDUT levels, inflammatory and antioxidant parameters, renal damage, and intestinal barrier function in adenine-induced CKD rats. Male Sprague-Dawley rats were divided into control group (CTL, n = 12) fed with standard diet; and CKD group (n = 16) given adenine (200 mg/kg/day) by oral gavage for 3-weeks to induce CKD. At the 4th week, CKD rats were subdivided into prebiotic supplementation (5g/kg/day) for four consecutive weeks (CKD-Pre, n = 8). Also, the control group was subdivided into two subgroups; prebiotic supplemented (CTL-Pre, n = 6) and non-supplemented group (CTL, n = 6). Results showed that prebiotic oligofructose-enriched inulin supplementation did not significantly reduce serum indoxyl sulfate (IS) but did significantly reduce serum p-Cresyl sulfate (PCS) (p = 0.002) in CKD rats. Prebiotic supplementation also reduced serum urea (p = 0.008) and interleukin (IL)-6 levels (p = 0.001), ameliorated renal injury, and enhanced antioxidant enzyme activity of glutathione peroxidase (GPx) (p = 0.002) and superoxide dismutase (SOD) (p = 0.001) in renal tissues of CKD rats. No significant changes were observed in colonic epithelial tight junction proteins claudin-1 and occludin in the CKD-Pre group. In adenine-induced CKD rats, oligofructose-enriched inulin supplementation resulted in a reduction in serum urea and PCS levels, enhancement of the antioxidant activity in the renal tissues, and retardation of the disease progression.

Effects of Probiotics, Prebiotics, and Synbiotics on Uremic Toxins, Inflammation, and Oxidative Stress in Hemodialysis Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The dysbiosis of gut microbiota may cause many complications in patients with end-stage renal disease, which may be alleviated by probiotic, prebiotic, and synbiotic supplementation. The aim of this systematic review and meta-analysis was to assess the effects of these supplementations on circulatory uremic toxins, biomarkers of inflammation, and oxidative stress in hemodialysis patients. We searched the EMBASE, MEDLINE, Web of Science, and Cochrane Library databases until 8 August 2021. Randomized controlled trials evaluating adult patients receiving hemodialysis were included. The pooled results from 23 studies with 931 hemodialysis patients indicated that interventions significantly decreased the circulating levels of p-cresyl sulfate (standardized mean difference (SMD): 0.38; 95% CI: -0.61, -0.15; p = 0.001), endotoxins (SMD: -0.58; 95% CI: -0.99, -0.18; p = 0.005), malondialdehyde (SMD: -1.16; 95% CI: -1.81, -0.52; p = 0.0004), C-reactive proteins (CRP) (SMD: -0.61; 95% CI: -0.99, -0.23; p = 0.002), and interleukin 6 (SMD: -0.92; 95% CI: -1.51, -0.33; p = 0.002), and improved the total antioxidant capacity (SMD: 0.89; 95% CI: 0.49, 1.30; p < 0.0001) and glutathione (SMD: 0.40; 95% CI: 0.14, 0.66; p = 0.003) when compared to the placebo group. Our results suggest that treatment with probiotics, prebiotics, and synbiotics may help alleviate uremic toxin levels, oxidative stress, and the inflammatory status in hemodialysis patients.

Effect of Probiotic, Prebiotic, and Synbiotic Supplementation on Cardiometabolic and Oxidative Stress Parameters in Patients With Chronic Kidney Disease: A Systematic Review and Meta-analysis

PURPOSE

Chronic kidney disease (CKD) is a major health problem worldwide. Evidence supporting the use of probiotic, prebiotic, and synbiotic supplementation in the management of CKD is mixed, although some studies suggest they may be useful. A systematic review and meta-analysis was performed to evaluate the effectiveness of probiotic, prebiotic, and synbiotic supplementation for improving cardiometabolic and oxidative stress parameters in patients with CKD.

METHODS

A comprehensive key word search was performed in EMBASE, Medline, Scopus, Cochrane Central, and Web of Science until April 2020. Randomized controlled trials investigating the effectiveness of probiotic, synbiotic, and prebiotic supplementation for the management of adults with CKD were included. Primary outcomes were measures of cardiometabolic parameters such as cholesterol and fasting blood glucose. Secondary outcomes were measures of oxidative stress (eg, malondialdehyde levels) and body mass index. Random effects meta-analyses were used to estimate mean treatment effects. Results are reported as standardized mean differences (SMDs) and 95% CIs.

FINDINGS

Fourteen articles were included. In patients with CKD, probiotic, prebiotic, and synbiotic supplementation significantly reduced total cholesterol (SMD, -0.25; 95% CI, -0.46 to -0.04; I² = 00.0%), fasting blood glucose (SMD, -0.41; 95% CI, -0.65 to -0.17; I² = 00.0%), homeostatic model assessment of insulin resistance (SMD, -0.63; 95% CI, -0.95 to -0.30; I² = 43.3%), insulin levels (SMD, -0.49; 95% CI, -0.90 to -0.08; I² = 65.2%), high-sensitivity C-reactive protein levels (SMD, -0.52; 95% CI, -0.81 to -0.22; I² = 52.7%), and malondialdehyde levels (SMD, -0.79; 95% CI, -1.22 to -0.37; I² = 69.8%) compared with control interventions. Supplementation significantly increased the quantitative insulin sensitivity check index (SMD, 0.78; 95% CI, 0.51 to 1.05; I² = 00.0%), total antioxidant capacity (SMD, 0.42; 95% CI, 0.18 to 0.66; I² = 00.0%), and glutathione levels (SMD, 0.52; 95% CI, 0.19 to 0.86; I² = 37.0%).

IMPLICATIONS

Probiotic, prebiotic, and synbiotic supplementation seems to be a promising intervention for improving cardiometabolic and oxidative stress parameters in patients with CKD.

Low serum parathyroid hormone is a risk factor for peritonitis episodes in incident peritoneal dialysis patients: a retrospective study

BACKGROUND

Serum parathyroid hormone (PTH) levels have been reported to be associated with infectious mortality in peritoneal dialysis (PD) patients. Peritonitis is the most common and fatal infectious complication, resulting in technique failure, hospital admission and mortality. Whether PTH is associated with peritonitis episodes remains unclear.

METHODS

We examined the association of PTH levels and peritonitis incidence in a 7-year cohort of 270 incident PD patients who were maintained on dialysis between January 2012 and December 2018 using Cox proportional hazard regression analyses. Patients were categorized into three groups by serum PTH levels as follows: low-PTH group, PTH < 150 pg/mL; middle-PTH group, PTH 150-300 pg/mL; high-PTH group, PTH > 300 pg/mL.

RESULTS

During a median follow-up of 29.5 (interquartile range 16-49) months, the incidence rate of peritonitis was 0.10 episodes per patient-year. Gram-positive organisms were the most common causative microorganisms (36.2%), and higher percentage of Gram-negative organisms was noted in patients with low PTH levels. Low PTH levels were associated with older age, higher eGFR, higher hemoglobin, calcium levels and lower phosphate, alkaline phosphatase levels. After multivariate adjustment, lower PTH levels were identified as an independent risk factor for peritonitis episodes [hazard ratio 1.643, 95% confidence interval 1.014-2.663, P = 0.044].

CONCLUSIONS

Low PTH levels are independently associated with peritonitis in incident PD patients.