Chronic Kidney Disease, Gut Dysbiosis, and Constipation: A Burdensome Triplet

Gut Dysbiosis and Probiotic Therapy in Chronic Kidney Disease: A Comprehensive Review

Chronic kidney disease (CKD) is a multifactorial disease affecting more than 13.4% of the world's population and is a growing public health problem. It is silent in its early stages and leads to irreversible kidney damage as the disease progresses. A key factor in this progression is the bidirectional relationship between CKD and gut dysbiosis, which creates an imbalance that promotes the accumulation of uremic toxins (UTs), contributing to renal fibrosis, endothelial dysfunction, and decreased glomerular filtration rate. In addition, CKD itself exacerbates gut dysbiosis by altering the composition of the gut microbiota (GM) and promoting the growth of pathogenic microorganisms. Therefore, it is crucial to explore new therapeutic strategies, and the use of probiotics and synbiotics has shown promise in modulating the GM. Numerous preclinical studies have shown that the use of probiotics in CKD has a beneficial effect on the kidney by reducing UTs, apoptosis, inflammation, and oxidative stress. Probiotic treatment has also been associated with restoration of intestinal integrity, modulation of microbial composition and diversity, and increased production of short-chain fatty acids (SCFAs). These positive results have also been observed in patients at different stages of CKD, where the use of probiotics and/or synbiotics was able to improve creatinine levels and uremic parameters and alleviate abdominal discomfort, in addition to modulating GM and reducing serum endotoxin levels. Although recent studies have explored the benefits of probiotics in the treatment of CKD, further research is needed to determine their long-term efficacy and clinical relevance. This review focuses on the factors driving gut dysbiosis in CKD, its role in disease progression, and the potential of probiotics as a therapeutic strategy.

The association of RBP4 with chronic kidney diseases in southern Chinese population

Background

Retinol binding protein 4 (RBP4), as a novel adipokine, has been proven to be highly related to insulin resistance, obesity, diabetes, hypertension, hyperuricemia and other metabolic diseases, which are all risk factors for chronic kidney disease (CKD). However, there is a lack of sufficient studies to explore the relationship between RBP4 and CKD, and no reports have described the predictive value of RBP4 for CKD. This study was designed to clarify the relationship between RBP4 and CKD and its potential predictive value.

Methods

Our team has conducted a large-scale cross-sectional survey that contained 2117 individuals on the southern coast of China. Correlation test, logistic regression analysis were used to evaluate the association between RBP4 and CKD. Receiver operating characteristic (ROC) were used to evaluate the optimal cut-off and predictive value of RBP4 for predicting CKD.

Results

By using the quartile grouping method, the population was divided into four groups according to the RBP4 level. As the RBP4 level increased, the prevalence of CKD also gradually increased among different groups. RBP4 was also correlated with various metabolic risk factors, such as blood glucose, blood lipids, blood pressure, waist circumference, uric acid, and with kidney function indicators such as creatinine, urine protein. Logistic regression analysis found that after adjusting for confounders, RBP4 remained significantly associated with CKD, independent of metabolic risk factors. ROC analysis showed that RBP4 as a single index, AUC (0.666) was superior to Scr, FBG, Log HOMA-IR, WC, TG, VLDL-C, UA, HDL-C, LDL-C, and that combining RBP4 indicator and other common risk factors of CKD can improve the accuracy for predicting CKD.

Conclusion

This study found that the RBP4 was strongly correlated with CKD, RBP4 may become a valuable marker and have strong power for predicting CKD.

Effect of fecal microbiota transplantation on patients with sporadic amyotrophic lateral sclerosis: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder marked by the progressive loss of motor neurons. Recent insights into ALS pathogenesis underscore the pivotal role of the gut microbiome, prompting an investigation into the potential therapeutic impact of fecal microbiota transplantation (FMT) on sporadic ALS patients.

METHODS

Conducted as a double-blind, placebo-controlled, parallel-group, randomized clinical trial, the study enrolled 27 participants from October 2022 to April 2023. The participants were followed up for 6 months from February 2023 to October 2023, during in-person visits at baseline, week 15, week 23, and week 35. The participants, evenly randomized, received either healthy donor FMT (FMT, n = 14) or a mixture of 0.9% saline and food coloring (E150c) as sham transplantation (placebo, n = 13). The primary outcome measured the change in the ALS Functional Rating Scale-Revised (ALSFRS-R) total score from baseline to week 35. Secondary outcomes included changes in gastrointestinal and respiratory functions, muscle strength, autonomic function, cognition, quality of life, intestinal microbiome composition, and plasm neurofilament light chain protein (NFL). Efficacy and safety outcomes were assessed in the intention-to-treat population.

RESULTS

A total of 27 randomized patients (47% women; mean age, 67.2 years), 24 participants completed the entire study. Notably, ALSFRS-R score changes exhibited no significant differences between FMT (6.1 [SD, 3.11]) and placebo (6.41[SD, 2.73]) groups from baseline to week 35. Secondary efficacy outcomes, encompassing respiratory function, muscle strength, autonomic function, cognition, quality of life, and plasm NFL, showed no significant differences. Nevertheless, the FMT group exhibited improvements in constipation, depression, and anxiety symptoms. FMT induced a shift in gut microbiome community composition, marked by increased abundance of Bifidobacterium, which persisted until week 15 (95% CI, 0.04 to 0.28; p = 0.01). Gastrointestinal adverse events were the primary manifestations of FMT-related side effects.

CONCLUSIONS

In this clinical trial involving 27 sporadic ALS patients, FMT did not significantly slow the decline in ALSFRS-R score. Larger multicenter trials are needed to confirm the efficacy of FMT in sporadic ALS patients and to explore the underlying biological mechanisms.

TRIAL REGISTRATION

Chinese Clinical Trial Registry Identifier: ChiCTR 2200064504.

The gut microbiome, chronic kidney disease, and sarcopenia

Sarcopenia is a prevalent condition in patients with chronic kidney disease (CKD), intricately linked to adverse prognoses, heightened cardiovascular risks, and increased mortality rates. Extensive studies have found a close and complex association between gut microbiota, kidney and muscle. On one front, patients with CKD manifest disturbances in gut microbiota and alterations in serum metabolites. These abnormal microbiota composition and metabolites in turn participate in the development of CKD. On another front, altered gut microbiota and its metabolites may lead to significant changes in metabolic homeostasis and inflammation, ultimately contributing to the onset of sarcopenia. The disturbance of gut microbial homeostasis, coupled with the accumulation of toxic metabolites, exerts deleterious effects on skeletal muscles in CKD patients with sarcopenia. This review meticulously describes the alterations observed in gut microbiota and its serum metabolites in CKD and sarcopenia patients, providing a comprehensive overview of pertinent studies. By delving into the intricate interplay of gut microbiota and serum metabolites in CKD-associated sarcopenia, we aim to unveil novel treatment strategies for ameliorating their symptoms and prognosis.

The associations between nutrition and circulating gut microbiota-derived uremic toxins in patients undergoing kidney replacement therapy: An observational, cross-sectional study

BACKGROUND

Gut microbiota generates a series of bioactive metabolites that can be converted into uremic toxins such as trimethylamine-N-oxide (TMAO), p-cresyl sulfate (pCS), and indoxyl sulfate (IS). The aim of the study was to examine the association between diet and the concentrations of the mentioned gut microbiota-derived uremic toxins.

METHODS

An observational cross-sectional study was conducted involving 210 participants: 84 hemodialysis (HD) patients, 44 peritoneal dialysis (PD) patients, 52 kidney transplant recipients (KTR), and 30 healthy controls. Dietary intake was assessed using a 3-day food diary and a food frequency questionnaire with 6 answers (FFQ-6). The alternate Mediterranean diet (aMED) score was calculated based on data obtained from the 3-day food diary and FFQ-6. Blood samples were analyzed for TMAO, pCS, and IS concentrations using liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

Significant differences in TMAO, pCS, and IS concentrations were observed among the study groups. HD and PD patients exhibited higher levels of these metabolites compared to KTR and healthy controls. The median aMED score was 4 (3-5) points in the HD group, 4.5 (4-6) points in the PD group, 5 (4-6) points in the KTRs, and 6 (5-7) points in the control group. Higher adherence to the Mediterranean diet (aMED score) was associated with lower pCS levels in dialysis patients. Vegetable intake several times a day was found to mitigate the effects of phenylalanine and tyrosine intake on pCS concentration among dialysis patients.

CONCLUSIONS

The diet of patients undergoing kidney replacement therapy (KRT) significantly affects the concentrations of gut microbiota-derived uremic toxins. These findings highlight the importance of dietary management in mitigating the adverse effects of these toxins in patients with chronic kidney disease (CKD).

Gut Dysbiosis and Its Role in the Anemia of Chronic Kidney Disease

The gut dysbiosis present in chronic kidney disease (CKD) has been associated with anemia. Factors such as the accumulation of gut-derived uremic toxins, increased gut barrier permeability-induced inflammation, and a reduced intestinal production of short-chain fatty acids (SCFAs), all associated with changes in the intestinal microbiota composition in CKD, may lead to the development or worsening of anemia in renal patients. Understanding and addressing these mechanisms related to gut dysbiosis in CKD patients can help to delay the development of anemia and improve its control in this population. One approach is to avoid or reduce the use of drugs linked to gut dysbiosis in CKD, such as phosphate binders, oral iron supplementation, antibiotics, and others, unless they are indispensable. Another approach involves introducing dietary changes that promote a healthier microbiota and/or using prebiotics, probiotics, or symbiotics to improve gut dysbiosis in this setting. These measures can increase the presence of SCFA-producing saccharolytic bacteria and reduce proteolytic bacteria, thereby lowering the production of gut-derived uremic toxins and inflammation. By ameliorating CKD-related gut dysbiosis, these strategies can also improve the control of renal anemia and enhance the response to erythropoiesis-stimulating agents (ESAs) in ESA-resistant patients. In this review, we have explored the relationship between gut dysbiosis in CKD and renal anemia and propose feasible solutions, both those already known and potential future treatments.

Aberrant bowel movement frequencies coincide with increased microbe-derived blood metabolites associated with reduced organ function

Bowel movement frequency (BMF) directly impacts the gut microbiota and is linked to diseases like chronic kidney disease or dementia. In particular, prior work has shown that constipation is associated with an ecosystem-wide switch from fiber fermentation and short-chain fatty acid production to more detrimental protein fermentation and toxin production. Here, we analyze multi-omic data from generally healthy adults to see how BMF affects their molecular phenotypes, in a pre-disease context. Results show differential abundances of gut microbial genera, blood metabolites, and variation in lifestyle factors across BMF categories. These differences relate to inflammation, heart health, liver function, and kidney function. Causal mediation analysis indicates that the association between lower BMF and reduced kidney function is partially mediated by the microbially derived toxin 3-indoxyl sulfate (3-IS). This result, in a generally healthy context, suggests that the accumulation of microbiota-derived toxins associated with abnormal BMF precede organ damage and may be drivers of chronic, aging-related diseases.

Effects of Dietary Fiber Intake and the Prevalence of Constipation Among Patients With End-Stage Renal Disease (ESRD) in Jeddah, Saudi Arabia: A Cross-Sectional Observational Study

RATIONALE/BACKGROUND

Hemodialysis (HD) patients with end-stage renal disease (ESRD) are particularly prone to constipation, which has become a growing public health issue. Nutritional therapy, such as fiber intake, significantly influences the management of constipation. In Saudi Arabia, there is limited data on fiber consumption and its correlation with constipation management in HD patients.

AIMS

The study aimed to investigate the correlation between dietary fiber intake and its effect on the prevalence of constipation in HD patients.

MATERIALS AND METHODS

This cross-sectional observational study of 77 ESRD patients on HD aged 18+ was conducted in a single dialysis center over six months. A questionnaire was employed to diagnose constipation (as defined by the Rome IV criteria of constipation), and seven-day food records were used to evaluate dietary fiber intake.

RESULTS

A study found a high prevalence of constipation (53%) among participants, with a lower daily fiber intake than recommended. However, a significant relationship was found between fiber intake and constipation (p < 0.05) with lower fiber intake in constipated patients compared to non-constipated (p = 0.001).

CONCLUSION

The study highlights a significant link between fiber intake and constipation in HD patients, suggesting adequate daily intake of fiber was effective in preventing constipation and that nutritional counseling should include adequate daily fiber intake in medical therapy management.

The Mediterranean Diet as a Potential Solution to the Gut Microbiome Dysbiosis in Psoriasis Patients

Background

Adherence to a Mediterranean Diet (MeD) has been associated with lower disease severity in patients with psoriasis. However, the mechanism behind how this diet may lead to disease modification remain understudied. Recent studies have revealed dysbiosis of the gut microbiome in patients with psoriasis suggestive of inflammation and altered immune regulation. Diet affects the gut microbiome and this review aims to evaluate whether correcting this dysbiosis may be one theoretical mechanism by which the MeD may be associated with lower psoriasis severity.

Methods

A literature search of the PubMed database was conducted for the terms 1) 'psoriasis' and 'microbiome' or 'microbiota,' and 2) 'Mediterranean diet' and 'microbiome' or 'microbiota' with manual screening for relevant articles. In total, we identified 9 relevant primary research studies investigating the gut microbiome in patients with psoriasis and 16 relevant primary research studies investigating changes in the microbiota for those consuming a MeD.

Results

Though varying in exact levels of certain bacteria, studies analyzing the microbiome in psoriasis revealed dysbiosis. Those analyzing the effect of the Mediterranean diet on the microbiome revealed beneficial changes, including alleviating some of the same alterations seen in the microbiome of those with psoriasis.

Conclusion

Microbiota change is a possible mechanism why the MeD has previously been associated with lower psoriasis severity.

Kangxianling formula attenuates renal fibrosis by regulating gut microbiota

BACKGROUND

Renal fibrosis (RF) produced adverse effect on kidney function. Recently, intestinal dysbiosis is a key regulator that promotes the formation of renal fibrosis. This study will focus on exploring the protective mechanism of Kangxianling Formula (KXL) on renal fibrosis from the perspective of intestinal flora.

METHODS

Unilateral Ureteral Obstruction (UUO) was used to construct rats' model with RF, and receive KXL formula intervention for 1 week. The renal function indicators were measured. Hematoxylin-eosin (HE), Masson and Sirus red staining were employed to detect the pathological changes of renal tissue in each group. The expression of α-SMA, Col-III, TGF-β, FN, ZO-1, and Occuludin was detected by immunofluorescence and immunohistochemistry. Rat feces samples were collected and analyzed for species' diversity using high-throughput sequencing 16S rRNA.

RESULTS

Rats in UUO groups displayed poor renal function as well as severe RF. The pro-fibrotic protein expression in renal tissues including α-SMA, Col-III, TGF-β and FN was increased in UUO rats, while ZO-1 and Occuludin -1 expression was downregulated in colon tissues. The above changes were attenuated by KXL treatment. 16S rRNA sequencing results revealed that compared with the sham group, the increased abundance of pathogenic bacteria including Acinetobacter, Enterobacter and Proteobacteria and the decreased abundance of beneficial bacteria including Actinobacteriota, Bifidobacteriales, Prevotellaceae, and Lactobacillus were found in UUO group. After the administration of KXL, the growth of potential pathogenic bacteria was reduced and the abundance of beneficial bacteria was enhanced.

CONCLUSION

KXL displays a therapeutical potential in protecting renal function and inhibiting RF, and its mechanism of action may be associated with regulating intestinal microbiota.

Generally-healthy individuals with aberrant bowel movement frequencies show enrichment for microbially-derived blood metabolites associated with reduced kidney function

Bowel movement frequency (BMF) has been linked to changes in the composition of the human gut microbiome and to many chronic conditions, like metabolic disorders, neurodegenerative diseases, chronic kidney disease (CKD), and other intestinal pathologies like irritable bowel syndrome and inflammatory bowel disease. Lower BMF (constipation) can lead to compromised intestinal barrier integrity and a switch from saccharolytic to proteolytic fermentation within the microbiota, giving rise to microbially-derived toxins that may make their way into circulation and cause damage to organ systems. However, the connections between BMF, gut microbial metabolism, and the early-stage development and progression of chronic disease remain underexplored. Here, we examined the phenotypic impact of BMF variation in a cohort of generally-healthy, community dwelling adults with detailed clinical, lifestyle, and multi-omic data. We showed significant differences in microbially-derived blood plasma metabolites, gut bacterial genera, clinical chemistries, and lifestyle factors across BMF groups that have been linked to inflammation, cardiometabolic health, liver function, and CKD severity and progression. We found that the higher plasma levels of 3-indoxyl sulfate (3-IS), a microbially-derived metabolite associated with constipation, was in turn negatively associated with estimated glomerular filtration rate (eGFR), a measure of kidney function. Causal mediation analysis revealed that the effect of BMF on eGFR was significantly mediated by 3-IS. Finally, we identify self-reported diet, lifestyle, and psychological factors associated with BMF variation, which indicate several common-sense strategies for mitigating constipation and diarrhea. Overall, we suggest that aberrant BMF is an underappreciated risk factor in the development of chronic diseases, even in otherwise healthy populations.

Exploring Symptom Clusters in Chinese Patients with Diabetic Kidney Disease: A Network Analysis

Purpose

The research on symptom management in patients with diabetic kidney disease (DKD) has shifted from separate symptoms to symptom clusters and networks recently. This study aimed to evaluate the unpleasant symptoms of DKD patients, and to investigate how these symptom clusters could affect patients.

Methods

408 DKD patients were recruited in this cross-sectional study. The symptoms of DKD patients were measured using the modified Dialysis Symptom Index. Network analysis was employed to evaluate the symptom network and the characteristics of individual nodes, while factor analysis was utilized to identify symptom clusters.

Results

Blurred vision was the most prevalent symptom among DKD patients. The symptoms identified as the most distressing, severe, and frequent were light headache or dizziness, arteriovenous fistula/catheterization pain, and diarrhea, respectively. Five symptom clusters were obtained from factor analysis, and the most central symptom cluster in the entire symptom network was sexual dysfunction.

Conclusion

This study identified five symptom clusters in Chinese DKD patients, with sexual dysfunction emerging as the most central cluster. These findings carry significant clinical implications, underscoring the necessity of assessing symptom clusters and their associations to enhance symptom management in DKD patients. Further research is essential to elucidate the underlying mechanisms of symptoms and to clarify the associations among symptoms in DKD patients across different disease trajectories or treatment modalities.

Investigating the Efficacy of Kidney-Protective Lactobacillus Mixture-Containing Pet Treats in Feline Chronic Kidney Disease and Its Possible Mechanism

Microbiota-based strategies are a novel auxiliary therapeutic and preventative way of moderating chronic kidney disease (CKD). Lactobacillus mixture (Lm) was previously demonstrated to exert a renal-protective function in the CKD mice model. The efficacy of probiotics in pet foods is a relatively new area of study, and thus verifying the potential health benefits is necessary. This study evaluated the efficacy of Lm treats in feline CKD and elucidated the mechanisms underlying host-microbe interactions. CKD cats (2 and 3 stages) were administrated probiotic pet treats daily (10 g) for 8 weeks. The results demonstrated that during the eight weeks of Lm administration, creatinine was reduced or maintained in all cats with CKD. Similarly, gut-derived uremic toxin (GDUT), indoxyl sulfate (IS), were potential clinical significance in IS after Lm treatment (confidence intervals = 90%). The life quality of the cats also improved. Feline gut microbiome data, metabolic functional pathway, and renal function indicator analyses revealed the possible mechanisms involved in modulating CKD feline microbial composition. Further regulation of the microbial functions in amino acid metabolism after Lm administration contributed to downregulating deleterious GDUTs. The current study provides potential adjuvant therapeutic insights into probiotic pet foods or treats for pets with CKD.

Blueberry, cranberry, raspberry, and strawberry as modulators of the gut microbiota: target for treatment of gut dysbiosis in chronic kidney disease? From current evidence to future possibilities

Gut dysbiosis is common in patients with chronic kidney disease (CKD) and is associated with uremic toxin production, inflammation, oxidative stress, and cardiovascular disease development. Therefore, healthy dietary patterns are essential modulators of gut microbiota. In this context, studies suggest that consuming berry fruits, rich in polyphenols and nutrients, may positively affect the gut microbiota, promoting the selective growth of beneficial bacteria and improving clinical status. However, studies on the effects of berry fruits on gut microbiota in CKD are scarce, and a better understanding of the possible mechanisms of action of berry fruits on gut microbiota is needed to guide future clinical studies and clinical practice in CKD. The objective was to discuss how berry fruits (blueberry, cranberry, raspberry, and strawberry) could be a therapeutic strategy to modulate the gut microbiota and possibly reverse the dysbiosis in CKD. Overall, available evidence shows that berry fruits can promote an increase in diversity by affecting the abundance of mucus-producing bacteria and short-chain fatty acids. Moreover, these fruits can increase the expression of mRNA involved in tight junctions in the gut such as occludin, tight junction protein 1 (TJP1), and mucin. Studies on the exact amount of berries leading to these effects show heterogeneous findings. However, it is known that, with 5 mg/day, it is already possible to observe some effects in animal models. Wild berries could possibly improve the uremic condition by reducing the levels of uremic toxins via modulation of the gut microbiota. In the long term, this could be an excellent strategy for patients with CKD. Therefore, clinical studies are encouraged to evaluate better these effects on CKD as well as the safe amount of these fruits in order to promote a better quality of life or even the survival of these patients.

Dietary Intake and Nutritional Status in Diabetic and Nondiabetic Patients With Chronic Kidney Disease Stage 4-5 (NutriDiab Study)

OBJECTIVES

The aim of the present study was to assess the dietary intake and nutritional status of patients with chronic kidney disease (CKD) stage 4-5 according to the presence of diabetes.

METHODS

This observational and cross-sectional study included adult patients with CKD stage 4-5 referred to a nephrology unit, between October 2018 and March 2019. Daily dietary intake was evaluated by 24-hour dietary inquiry and urine excretion. Nutritional status was assessed by measuring body composition using bioimpedance analysis and muscle function using handgrip strength. Undernutrition was considered using the protein energy wasting score.

RESULTS

A total of 75 CKD patients were included, 36 (48%) of whom had diabetes; median age (interquartile range) was 71 (60-80) years. The median weight-adjusted dietary energy intake (DEI) was 22.6 (19.1-28.2) kcal/kg/day and the mean weight-adjusted dietary protein intake (DPI) was 0.86 ± 0.19 g/kg/day. There was no significant difference in DEI and DPI between patients with diabetes and those without, except for weight-adjusted DPI which was significantly lower in diabetic patients (P = .022). In univariate analysis, diabetes was associated with weight-adjusted DPI (coefficient [95% confidence interval] -0.237 [-0.446; -0.004] kcal/kg/day; P = .040), but this association did not remain significant in multivariate analysis. Nutritional status did not differ significantly between diabetic and nondiabetic patients except for lean tissue mass, which was lower in diabetic patients (P = .046). The proportion of patients with protein energy wasting was not significantly different between diabetic and nondiabetic patients (13.9% vs. 10.2%, respectively).

CONCLUSIONS

In the present cohort, DPI and DEI were not significantly different between diabetic and nondiabetic CKD patients. Diabetes was not found to be associated with dietary intakes in CKD stage 4-5 patients.

Bowel habits were associated with mortality in chronic kidney disease: results from a nationwide prospective cohort study

PURPOSE

Bowel habits may affect the prognosis in the chronic kidney disease (CKD) patients. This study aimed to explore the association of bowel habits with cardiovascular and all-cause mortality in CKD.

METHODS

2460 CKD patients in the National Health and Nutrition Examination Survey (NHANES) from 2005 through 2010 without missing data for bowel habits and mortality were enrolled. Bowel habits including bowel movements (BMs) per week and stools consistency were obtained by standard interview. Mortality status and cause of death were determined by NHANES-linked National Death Index records through 31 December 2015. Cox proportional hazard models and Kaplan-Meier analysis were used to evaluate the association of bowel habits with cardiovascular and all-cause mortality.

RESULTS

A total of 2460 CKD patients with an average age of 60.80 ± 0.57 years were enrolled. During an average follow-up of 87.47 ± 0.98 months, 144 cardiovascular and 669 all-cause deaths were documented. Reporting 3 or fewer BMs per week was associated with cardiovascular (HR = 1.83, 95% CI: 1.06, 3.17) and all-cause mortality (HR = 1.71, 95% CI: 1.20, 2.43). More than 10 BMs per week also increased the risk of all-cause mortality (HR = 1.21, 95% CI: 1.01, 1.45). Hard stools consistency increased the risk of all-cause mortality (HR= 2.00, 95% CI: 1.48, 2.70) compared with those reporting normal stools.

CONCLUSION

Low stool frequency and hard stool consistency were associated with an increased risk of mortality in patients with CKD.

An Overview of Chronic Kidney Disease Pathophysiology: The Impact of Gut Dysbiosis and Oral Disease

Chronic kidney disease (CKD) is a severe condition and a significant public health issue worldwide, carrying the burden of an increased risk of cardiovascular events and mortality. The traditional factors that promote the onset and progression of CKD are cardiometabolic risk factors like hypertension and diabetes, but non-traditional contributors are escalating. Moreover, gut dysbiosis, inflammation, and an impaired immune response are emerging as crucial mechanisms in the disease pathology. The gut microbiome and kidney disease exert a reciprocal influence commonly referred to as "the gut-kidney axis" through the induction of metabolic, immunological, and endocrine alterations. Periodontal diseases are strictly involved in the gut-kidney axis for their impact on the gut microbiota composition and for the metabolic and immunological alterations occurring in and reciprocally affecting both conditions. This review aims to provide an overview of the dynamic biological interconnections between oral health status, gut, and renal pathophysiology, spotlighting the dynamic oral-gut-kidney axis and raising whether periodontal diseases and gut microbiota can be disease modifiers in CKD. By doing so, we try to offer new insights into therapeutic strategies that may enhance the clinical trajectory of CKD patients, ultimately advancing our quest for improved patient outcomes and well-being.

Gutted: constipation in children with chronic kidney disease and on dialysis

Functional constipation is a common problem in otherwise healthy children. Children with chronic kidney disease (CKD) and on dialysis have additional disease-related risk factors including the uremic milieu, fluid and dietary restrictions, and decreased physical activity, as well as treatment-related risk factors such as dialysis therapy and polypharmacy that contribute to and compound the problem. Constipation causes significant distress for children and their caregivers. In children on peritoneal dialysis, severe constipation can impede catheter function and ultrafiltration. Accumulating evidence points to a possible bidirectional relationship between constipation and CKD, potentially mediated by gut dysbiosis with consequent increased generation of gut-derived uremic toxins and disruption of intestinal epithelium integrity leading to translocation of noxious luminal contents into the circulation inducing systemic inflammation. Effective management of constipation is required but there is little published data on the safety and effectiveness of treatments in adults or children with CKD. In this review, we discuss the diagnosis and epidemiology of functional constipation, provide an overview of its pathophysiology, summarize the therapeutic management, and reflect on the challenges in children with CKD.

Targeting the Gut Microbiota in Kidney Disease: The Future in Renal Nutrition and Metabolism

There is increasing interest in the therapeutic potential of manipulating the gut microbiome of patients with chronic kidney disease (CKD). This is because there is a substantial deviation from a balanced gut microbiota profile in CKD, with many deleterious downstream effects. Nutritional interventions such as plant-based diets with reduced animal protein intake and the use of probiotics, prebiotics, and synbiotics may alter the microbiome. This article aims to briefly describe what is known about the gut microbiome in patients with CKD, factors contributing to gut dysbiosis, and outline important evidence gaps. Future potential therapies, including restoring the microbiota with food and microbiota-based and metabolomic-based therapies, are also discussed.

Frailty in kidney transplant candidates and recipients: pathogenesis and intervention strategies

ABSTRACT

With the rapid aging of the global population posing a serious problem, frailty, a non-specific state that reflects physiological senescence rather than aging in time, has become more widely addressed by researchers in various medical fields. A high prevalence of frailty is found among kidney transplant (KT) candidates and recipients. Therefore, their frailty has become a research hotspot in the field of transplantation. However, current studies mainly focus on the cross-sectional survey of the incidence of frailty among KT candidates and recipients and the relationship between frailty and transplantation. Research on the pathogenesis and intervention is scattered, and relevant review literature is scarce. Exploring the pathogenesis of frailty in KT candidates and recipients and determining effective intervention measures may reduce waiting list mortality and improve the long-term quality of life of KT recipients. Therefore, this review explains the pathogenesis and intervention measures for frailty in KT candidates and recipients to provide a reference for the formulation of effective intervention strategies.

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.

The effects of synbiotics on indoxyl sulphate level, constipation, and quality of life associated with constipation in chronic haemodialysis patients: a randomized controlled trial

Background

Gut microbiota dysbiosis in patients with chronic kidney disease on haemodialysis (CKD-HD) creates an increase in proteolytic bacteria activity, leading to an increase in the production of uraemic toxins, such as indoxyl sulphate, worsening of constipation symptoms and reducing patients’ quality of life. Improving gut microbiota dysbiosis is expected to improve this condition. This study aimed to evaluate the effect of synbiotics on indoxyl sulphate levels, constipation symptoms, and constipation-related quality of life in haemodialysis patients.

Methods

This was a double-blinded randomized controlled clinical trial with a parallel design involving haemodialysis patients. We included chronic haemodialysis patients with gastrointestinal complaints, difficulty defecating, faeces with hard consistency, or a bowel movement frequency of fewer than three times per week. Patients were randomly divided into two groups (synbiotics (Lactobacillus acidophilus and Bifidobacterium longum 5x10⁹ CFU) and placebo) for 60 days of oral intervention. All participants, caregivers, and outcome assessors were blinded to group assignment. The primary outcome was a decrease in indoxyl sulphate toxin levels. Meanwhile, improvement in constipation symptoms (measured using the Patient Assessment of Constipation: Symptoms (PAC-SYM) questionnaire) and improvement in constipation-related quality of life (measured using the Patient Assessment of Constipation Quality of Life (PAC-QOL) questionnaire) were assessed as secondary outcomes.

Results

We included 60 patients (30 intervention; median age of 51.23 (13.57) years, 33.3% male; 30 control; median age of 52.33 (11.29) years, 36.7% male). There was no significant difference in terms of pre- and postintervention indoxyl sulphate toxin levels in the synbiotics group compared to the placebo group (p=0.438). This study found an improvement in constipation symptoms (p = 0.006) and constipation-related quality of life (p=0.001) after synbiotic administration.

Conclusion

Two months of synbiotic supplementation did not lower indoxyl sulphate toxin levels. Nevertheless, it had a major effect in improving constipation and quality of life affected by constipation in patients undergoing chronic haemodialysis.

Trial registration

NCT04527640 (date of first registration: 26/08/2020)

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02890-9.

Adherence to Caloric and Protein Recommendations in Older Hemodialysis Patients: A Multicenter Study

Hemodialysis (HD) patients are characterized by malnutrition, which adversely affects their survival. The development of malnutrition is influenced, among other factors, by improper diet and the advanced age of patients. The study aimed to assess the nutritional status and adherence to dietary recommendations among older patients. The multicenter study included 179 stable HD patients. The nutritional status was assessed by a 7-point Subjective Global Assessment (SGA). Anthropometry and body composition was analyzed. The diet was assessed based on the 3-day food diary and the Food Frequency Questionnaire with 6 answers (FFQ-6). Blood laboratory tests were performed. Based on the 7-point SGA, malnutrition was diagnosed in 38.5% of HD patients. The decreased content of the muscle tissue (LTI < 14 kg/m2) was observed in 70.4% of the examined patients and the decreased concentration of s-albumin was observed in 44.1% of patients. Older patients had significantly lower LTI. 26% of patients consumed less than 25 kcal/kg body weight and less than 0.8 g protein/kg body weight. Older patients’ diets contained significantly fewer calories. There were significant differences between nutrient intake on a weekday with dialysis, a weekday without dialysis, and a weekend day without dialysis. The lowest intake of nutrients was observed on the day of dialysis. Nutritional education and the determination of whether food is permitted during hemodialysis are necessary to improve patients’ nutrition.

Homeostasis in the Gut Microbiota in Chronic Kidney Disease

The gut microbiota consists of trillions of microorganisms, fulfilling important roles in metabolism, nutritional intake, physiology and maturation of the immune system, but also aiding and abetting the progression of chronic kidney disease (CKD). The human gut microbiome consists of bacterial species from five major bacterial phyla, namely Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria, and Verrucomicrobia. Alterations in the members of these phyla alter the total gut microbiota, with a decline in the number of symbiotic flora and an increase in the pathogenic bacteria, causing or aggravating CKD. In addition, CKD-associated alteration of this intestinal microbiome results in metabolic changes and the accumulation of amines, indoles and phenols, among other uremic metabolites, which have a feedforward adverse effect on CKD patients, inhibiting renal functions and increasing comorbidities such as atherosclerosis and cardiovascular diseases (CVD). A classification of uremic toxins according to the degree of known toxicity based on the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence was selected to identify the representative uremic toxins from small water-soluble compounds, protein-bound compounds and middle molecules and their relation to the gut microbiota was summarized. Gut-derived uremic metabolites accumulating in CKD patients further exhibit cell-damaging properties, damage the intestinal epithelial cell wall, increase gut permeability and lead to the translocation of bacteria and endotoxins from the gut into the circulatory system. Elevated levels of endotoxins lead to endotoxemia and inflammation, further accelerating CKD progression. In recent years, the role of the gut microbiome in CKD pathophysiology has emerged as an important aspect of corrective treatment; however, the mechanisms by which the gut microbiota contributes to CKD progression are still not completely understood. Therefore, this review summarizes the current state of research regarding CKD and the gut microbiota, alterations in the microbiome, uremic toxin production, and gut epithelial barrier degradation.

Probiotics ameliorate IgA nephropathy by improving gut dysbiosis and blunting NLRP3 signaling

Background

Recently, a few studies have indicated a relationship between the gut microbiota and IgA nephropathy (IgAN). Whether the gut microbiota participates in the pathogenesis of IgAN and whether probiotics are effective in treating IgAN are still controversial. Therefore, this study aimed to identify the differences in the structure of the gut microbiota between IgAN and controls and to evaluate the efficacy and mechanism of probiotics in the treatment of IgAN.

Methods

To address this question, 35 IgAN patients and 25 healthy volunteers were enrolled, and a mouse IgAN model was also constructed. The stool microbes were analyzed by 16S rRNA high-throughput sequencing to identify the differential strains between IgAN and healthy controls. The impact of probiotics on the structure of the intestinal flora and the efficacy of the probiotics in the treatment of IgAN were evaluated.

Results

Although the microflora structure of mice and humans was not the same, both patients and mice with IgAN exhibited gut microbiota dysbiosis, with all subjects presenting an evident decrease in Bifidobacterium levels. The Bifidobacterium proportion was negatively correlated with proteinuria and hematuria levels, indicating that the decreased Bifidobacterium abundance could be related to IgAN severity. Probiotic treatment containing Bifidobacterium in IgAN mice could significantly alleviate gut dysbiosis, specifically by increasing the proportion of beneficial bacteria and reducing the abundance of potentially pathogenic bacteria. Moreover, both probiotics and their metabolites, short-chain fatty acids (SCFAs), could attenuate IgAN clinicopathological manifestations by inhibiting the NLRP3/ASC/Caspase 1 signaling pathway.

Conclusions

Supplementation with probiotics mainly containing Bifidobacterium could markedly improve gut dysbiosis in IgAN. Moreover, both probiotics and their SCFA metabolites could attenuate the clinicopathological manifestations of IgAN by inhibiting the NLRP3/ASC/Caspase 1 signaling pathway. Therefore, probiotics have potential as an adjunctive therapy for IgAN.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03585-3.

Emerging trends and focus for the link between the gastrointestinal microbiome and kidney disease

The clinical value of the relationship between gastrointestinal microbiome imbalance and its corresponding interventions with kidney disease is emerging. This study describes the hotspots and evolution of gastrointestinal microbiome and kidney disease research over the past three decades by scientific collaboration networks and finally predicts future trends in the field through bibliometric analysis and visualization studies. CiteSpace was used to explore the original articles from January 1990 to August 2021 to visualize the knowledge network of journals, countries, institutions, authors, references, and keywords in this field. Publications were extracted from Web of Science Core Collection database using the terms “gastrointestinal microbiome” and “kidney disease” (and their synonyms in MeSH). A total of 2145 publications with 93880 references in 102 journals were included in the analyses. The number of studies combining gastrointestinal microbiomes with kidney diseases has increased significantly over the past two decades. The United States is the leading country in the number of documents, and the leading institution is the Cleveland Clinic. The most landmark articles in the field are on chronic renal failure, L-Carnitin, and cardiovascular disease. The pathogenesis of uremia toxin is an emerging trend in gastrointestinal microbiomes and kidney diseases. In addition, probiotic or synbiotic supplements have strong clinical value in adjusting abnormal intestinal symbiotic environments. This study demonstrates a growing understanding of the interaction between gut microbiota and kidney disease over time. Using microbial supplements to improve the living conditions of kidney disease patients is a promising and hot research focus. Based on publications extracted from the database, this study may provide clinicians and researchers with valuable information to identify potential collaborators and partner institutions and better predict their dynamic progression.

Effect of 8-week intake of the n-3 fatty acid-rich perilla oil on the gut function and as a fuel source for female athletes: a randomised trial

Previous studies have examined the effects of n-3 fatty acid intake in supplement form or fish oil capsules, but there are few studies based on other foods. Perilla oil is a traditional Japanese seed oil rich in n-3 fatty acids. This randomised trial aimed to determine the appropriate n-3 fatty acid dose through consumption of perilla oil, which improves gut function and microbiota in trained athletes, and the amount of fat fuel required to provide energy to athletes involved in high-intensity training to improve athletic performance. Thirty-six female athletes training six times per week were randomly assigned to three groups according to perilla oil intake: 9 g/d (high oil intake (HOI)), 3 g/d (low oil intake (LOI)) and placebo-supplementation (PLA) groups. The HOI and LOI groups had perilla oil-containing jelly and the PLA group had placebo jelly for 8 weeks. Gut microbiota, constipation score and urinary biochemical index were measured pre- and post-intervention. The spoilage bacteria, Proteobacteria, significantly decreased (P = 0·036, d = 0·53), whereas Butyrate-producing bacteria, Lachnospiraceae, significantly increased (P = 0·007, d = 1·2) in the HOI group. Urinary indoxyl sulphate significantly decreased in the HOI group only (P = 0·010, d = 0·82). Changes in the constipation score were significantly lower in the HOI group (P = 0·020) and even lower in the LOI group (P = 0·073) than in the PLA group; there were significant differences between groups (P = 0·035). Therefore, perilla oil intake may improve gut function and microbiota in athletes, with higher doses resulting in further improvement.

Gut Dysbiosis and Kidney Diseases

Gut dysbiosis is defined as disorders of gut microbiota and loss of barrier integrity, which are ubiquitous on pathological conditions and associated with the development of various diseases. Kidney diseases are accompanied with gut dysbiosis and metabolic disorders, which in turn contribute to the pathogenesis and progression of kidney diseases. Microbial alterations trigger production of harmful metabolites such as uremic toxins and a decrease in the number of beneficial ones such as SCFAs, which is the major mechanism of gut dysbiosis on kidney diseases according to current studies. In addition, the activation of immune responses and mitochondrial dysfunction by gut dysbiosis, also lead to the development of kidney diseases. Based on the molecular mechanisms, modification of gut dysbiosis via probiotics, prebiotics and synbiotics is a potential approach to slow kidney disease progression. Fecal microbiota transplantation (FMT) and genetic manipulation of the gut microbiota are also promising choices. However, the clinical use of probiotics in kidney disease is not supported by the current clinical evidence. Further studies are necessary to explore the causal relationships of gut dysbiosis and kidney diseases, the efficiency and safety of therapeutic strategies targeting gut-kidney axis.

The relationship between uremic toxins and symptoms in older men and women with advanced chronic kidney disease

Background

Patients with stage 4/5 chronic kidney disease (CKD) suffer from various symptoms. The retention of uremic solutes is thought to be associated with those symptoms. However, there are relatively few rigorous studies on the potential links between uremic toxins and symptoms in patients with CKD.

Methods

The EQUAL study is an ongoing observational cohort study of non-dialyzed patients with stage 4/5 CKD. EQUAL patients from Germany, Poland, Sweden and the UK were included in the present study (n = 795). Data and symptom self-report questionnaires were collected between April 2012 and September 2020. Baseline uric acid and parathyroid hormone and 10 uremic toxins were quantified. We tested the association between uremic toxins and symptoms and adjusted P-values for multiple testing.

Results

Symptoms were more frequent in women than in men with stage 4/5 CKD, while levels of various uremic toxins were higher in men. Only trimethylamine N-oxide (TMAO; positive association with fatigue), p-cresyl sulfate (PCS) with constipation and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (negative association with shortness of breath) demonstrated moderately strong associations with symptoms in adjusted analyses. The association of phenylacetylglutamine with shortness of breath was consistent in both sexes, although it only reached statistical significance in the full population. In contrast, TMAO (fatigue) and PCS and phenylacetylglutamine (constipation) were only associated with symptoms in men, who presented higher serum levels than women.

Conclusion

Only a limited number of toxins were associated with symptoms in persons with stage 4/5 CKD. Other uremic toxins, uremia-related factors or psychosocial factors not yet explored might contribute to symptom burden.

The Fecal Microbiota Transplantation: A Remarkable Clinical Therapy for Slow Transit Constipation in Future

Slow transit constipation is a common condition that would be difficult to treat in clinical practice with a widespread incidence in the population. Pharmacotherapy and surgery are common treatment modalities. However, the clinical effect is limited, and patients still suffer from it. As the researchers strived in this field for decades, the profound relationship between slow transit constipation and fecal microbiota transplantation has comprehensively been sustained. It is very pivotal to maintain intestinal homeostasis, the structure function and metabolic function of symbiotic bacteria, which can inhibit the engraftment of intestinal pathogens. This mini review explains the treatment effects and possible mechanisms of the fecal microbiota transplantation in treating slow transit constipation. Simultaneously, it is found that there is significant improvement in the disease by adjusting the intestinal microbes like fecal microbiota transplantation. Fecal microbiota transplantation has efficient therapeutic effects in slow transit constipation compared with traditional therapies.

Bacterial metabolites and cardiovascular risk in children with chronic kidney disease

Cardiovascular complications are the major cause of the marked morbidity and mortality associated with chronic kidney disease (CKD). The classical cardiovascular risk factors such as diabetes and hypertension undoubtedly play a role in the development of cardiovascular disease (CVD) in adult CKD patients; however, CVD is just as prominent in children with CKD who do not have these risk factors. Hence, the CKD-specific pathophysiology of CVD remains incompletely understood. In light of this, studying children with CKD presents a unique opportunity to analyze CKD-associated mechanisms of CVD more specifically and could help to unveil novel therapeutic targets.

Here, we comprehensively review the interaction of the human gut microbiome and the microbial metabolism of nutrients with host immunity and cardiovascular end-organ damage. The human gut microbiome is evolutionary conditioned and modified throughout life by endogenous factors as well as environmental factors. Chronic diseases, such as CKD, cause significant disruption to the composition and function of the gut microbiome and lead to disease-associated dysbiosis. This dysbiosis and the accompanying loss of biochemical homeostasis in the epithelial cells of the colon can be the result of poor diet (e.g., low-fiber intake), medications, and underlying disease. As a result of dysbiosis, bacteria promoting proteolytic fermentation increase and those for saccharolytic fermentation decrease and the integrity of the gut barrier is perturbed (leaky gut). These changes disrupt local metabolite homeostasis in the gut and decrease productions of the beneficial short-chain fatty acids (SCFAs). Moreover, the enhanced proteolytic fermentation generates unhealthy levels of microbially derived toxic metabolites, which further accumulate in the systemic circulation as a consequence of impaired kidney function. We describe possible mechanisms involved in the increased systemic inflammation in CKD that is associated with the combined effect of SCFA deficiency and accumulation of uremic toxins. In the future, a more comprehensive and mechanistic understanding of the gut–kidney–heart interaction, mediated largely by immune dysregulation and inflammation, might allow us to target the gut microbiome more specifically in order to attenuate CKD-associated comorbidities.

Gut Microbiome-Derived Uremic Toxin Levels in Hemodialysis Patients on Different Phosphate Binder Therapies

Introduction

Constipation is prevalent in patients with kidney failure partly due to the use of medication, such as phosphate binders. We hypothesized that serum levels of gut microbiome-derived uremic toxins (UTOX) may be affected by the choice of phosphate binder putatively through its impact on colonic transit time. We investigated two commonly prescribed phosphate binders, sevelamer carbonate (SEV) and sucroferric oxyhydroxide (SFO), and their association with gut microbiome-derived UTOX levels in hemodialysis (HD) patients.

Methods

Weekly blood samples were collected from 16 anuric HD participants during the 5-week observational period. All participants were on active phosphate binder monotherapy with either SFO or SEV for at least 4 weeks prior to enrollment. Eight UTOX (7 gut microbiome-derived) and tryptophan were quantified using liquid chromatography-mass spectrometry. Serum phosphorus, nutritional, and liver function markers were also measured. For each substance, weekly individual levels, the median concentration per participant, and differences between SFO and SEV groups were reported. Patient-reported bowel movements, by the Bristol Stool Scale (BSS), and pill usage were assessed weekly.

Results

The SEV group reported a 3.3-fold higher frequency of BSS stool types 1 and 2 (more likely constipated, p < 0.05), whereas the SFO group reported a 1.5-fold higher frequency of BSS stool types 5–7 (more likely loose stool and diarrhea, not significant). Participants in the SFO group showed a trend toward better adherence to phosphate binder therapy (SFO: 87.6% vs. SEV: 66.6%, not significant). UTOX, serum phosphorus, nutritional and liver function markers, and tryptophan were not different between the two groups.

Conclusion

There was no difference in the gut microbiome-derived UTOX levels between phosphate binders (SFO vs. SEV), despite SFO therapy resulting in fewer constipated participants. This pilot study may inform study design of future clinical trials and highlights the importance of including factors beyond bowel habits and their association with UTOX levels.

Chronic Kidney Disease-Associated Itch (CKD-aI) in Children-A Narrative Review

Chronic kidney disease (CKD) is a condition of widespread epidemiology and serious consequences affecting all organs of the organism and associated with significant mortality. The knowledge on CKD is rapidly evolving, especially concerning adults. Recently, more data is also appearing regarding CKD in children. Chronic itch (CI) is a common symptom appearing due to various underlying dermatological and systemic conditions. CI may also appear in association with CKD and is termed chronic kidney disease-associated itch (CKD-aI). CKD-aI is relatively well-described in the literature concerning adults, yet it also affects children. Unfortunately, the data on paediatric CKD-aI is particularly scarce. This narrative review aims to describe various aspects of CKD-aI with an emphasis on children, based on the available data in this population and the data extrapolated from adults. Its pathogenesis is described in details, focusing on the growing role of uraemic toxins (UTs), as well as immune dysfunction, altered opioid transmission, infectious agents, xerosis, neuropathy and dialysis-associated aspects. Moreover, epidemiological and clinical aspects are reviewed based on the few data on CKD-aI in children, whereas treatment recommendations are proposed as well, based on the literature on CKD-aI in adults and own experience in managing CI in children.

An Innovative Synbiotic Formulation Decreases Free Serum Indoxyl Sulfate, Small Intestine Permeability and Ameliorates Gastrointestinal Symptoms in a Randomized Pilot Trial in Stage IIIb-IV CKD Patients

Proteolytic dysbiosis of the gut microbiota has been recognized as both a typical feature of chronic kidney disease (CKD) and a risk factor for its progression. Blood accumulation of gut-derived uremic toxins (UTs) like indoxyl sulfate (IS) and p-cresyl sulfate (PCS), intestinal permeability and constipation are typical features accompanying CKD progression and triggering chronic inflammation. In order to verify the efficacy of the innovative synbiotic formulation NATUREN G^® in modulating the levels of circulating UTs, intestinal permeability and gastrointestinal symptoms, we set up a randomized, single-blind, placebo-controlled, pilot trial in stage IIIb-IV CKD patients and in healthy controls. Two-month administration of the synbiotic resulted in a decrease of free IS, as compared with the placebo-treated arm, only in the CKD group. The other UTs did not significantly change, although different trends in time (increase in the placebo arm and decrease in the synbiotic arm) were observed. Moreover, after supplementation, reduction of small intestinal permeability and amelioration of abdominal pain and constipation syndromes were observed only in the CKD group. The obtained results suggest the specificity of action of NATUREN G^® in CKD and justify further validation in a wider study population.