The role of the gastrointestinal tract and microbiota on uremic toxins and chronic kidney disease development

Is the enteric nervous system a lost piece of the gut-kidney axis puzzle linked to chronic kidney disease?

The enteric nervous system (ENS) regulates numerous functional and immunological attributes of the gastrointestinal tract. Alterations in ENS cell function have been linked to intestinal outcomes in various metabolic, intestinal, and neurological disorders. Chronic kidney disease (CKD) is associated with a challenging intestinal environment due to gut dysbiosis, which further affects patient quality of life. Although the gut-related repercussions of CKD have been thoroughly investigated, the involvement of the ENS in this puzzle remains unclear. ENS cell dysfunction, such as glial reactivity and alterations in cholinergic signaling in the small intestine and colon, in CKD are associated with a wide range of intestinal pathways and responses in affected patients. This review discusses how the ENS is affected in CKD and how it is involved in gut-related outcomes, including intestinal permeability, inflammation, oxidative stress, and dysmotility.

Oat Dietary Fiber Delays the Progression of Chronic Kidney Disease in Mice by Modulating the Gut Microbiota and Reducing Uremic Toxin Levels

Chronic kidney disease (CKD) has emerged as a significant public health concern. In this article, we investigated the mechanism of oat dietary fiber in regulating CKD. Our findings indicated that the gut microbiota of CKD patients promoted gut microbiota dysbiosis and kidney injury in CKD mice. Intervention with oat-resistant starch prepared by ultrasonic combined enzymatic hydrolysis (ORSU) and oat β-glucan with a molecular weight of 5 × 104 Da (OBGM) elevated the levels of short-chain fatty acids (SCFAs) and regulated gut dysbiosis in the gut-humanized CKD mice. ORSU and OBGM also reduced CKD-related uremic toxins such as creatinine, indoxyl sulfate (IS), and p-cresol sulfate (PCS) levels; reinforced the intestinal barrier function of the gut-humanized CKD mice; and mitigated renal inflammation and fibrosis via the NF-κB/TGF-β pathway. Therefore, ORSU and OBGM might delay the progression of CKD by modulating the gut microbiota to reduce uremic toxins levels. Our results explain the mechanism of oat dietary fiber aimed at mitigating CKD.

Exploring the Preventive and Therapeutic Mechanisms of Probiotics in Chronic Kidney Disease through the Gut-Kidney Axis

Gut dysbiosis contributes to deterioration of chronic kidney disease (CKD). Probiotics are a potential approach to modulate gut microbiota and gut-derived metabolites to alleviate CKD progression. We aim to provide a comprehensive view of CKD-related gut dysbiosis and a critical perspective on probiotic function in CKD. First, this review addresses gut microbial alterations during CKD progression and the adverse effects associated with the changes in gut-derived metabolites. Second, we conduct a thorough examination of the latest clinical trials involving probiotic intervention to unravel critical pathways via the gut-kidney axis. Finally, we propose our viewpoints on limitations, further considerations, and future research prospects of probiotic adjuvant therapy in alleviating CKD progression. Enhancing our understanding of host-microbe interactions is crucial for gaining precise insights into the mechanisms through which probiotics exert their effects and identifying factors that influence the effectiveness of probiotics in developing strategies to optimize their use and enhance clinical outcomes.

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.

Gut Microbiota Interventions to Retain Residual Kidney Function

Residual kidney function for patients with chronic kidney disease (CKD) is associated with better quality of life and outcome; thus, strategies should be implemented to preserve kidney function. Among the multiple causes that promote kidney damage, gut dysbiosis due to increased uremic toxin production and endotoxemia need attention. Several strategies have been proposed to modulate the gut microbiota in these patients, and diet has gained increasing attention in recent years since it is the primary driver of gut dysbiosis. In addition, medications and faecal transplantation may be valid strategies. Modifying gut microbiota composition may mitigate chronic kidney damage and preserve residual kidney function. Although various studies have shown the influential role of diet in modulating gut microbiota composition, the effects of this modulation on residual kidney function remain limited. This review discusses the role of gut microbiota metabolism on residual kidney function and vice versa and how we could preserve the residual kidney function by modulating the gut microbiota balance.

Gut microbiota dysbiosis in AKI to CKD transition

BACKGROUND AND AIM

The symptoms of acute kidney injury (AKI) include a sudden drop-in glomerular filtration rate (GFR), a rise in serum creatinine (sCr), blood urea nitrogen (BUN), and electrolytes, which leads to a rapid loss of kidney function. Chronic kidney disease progresses when AKI symptoms persist for over three months or 90 days. Numerous prevalent secondary risk factors, including diabetes, hypertension, obesity, and heart illness, are directly or indirectly linked to the development of AKI and the switch from AKI to CKD. Recently, the change of intestinal bacteria known as "gut dysbiosis" has been linked to distant organ dysfunction, including the heart, lungs, kidneys, and brain. Indirectly or directly, gut dysbiosis contributes to the progression of CKD and AKI. However, the effects of gut dysbiosis and the mechanism of action in the progression from AKI to CKD are unknown or need further investigation. The mechanism by which gut dysbiosis initiates AKI's progression to CKD should be explicitly concerned. The review primarily focuses on the action of gut dysbiosis in kidney disease, the effects of dysbiosis, the characterisation of dysbiosis and its pathogenic products, the various pathogenic routes and mechanism involved in expediting the transition from AKI to CKD.

CONCLUSION

We identified and briefly reviewed the impacts of dysbiosis in various situations such as hypoxia, mitochondrial induced reactive oxygen species (mtROS), aryl hydrocarbon receptor (AhR) activation and microbiota derived uremic toxemic substances profoundly to push AKI to CKD conditions.

Food, gut barrier dysfunction, and related diseases: A new target for future individualized disease prevention and management

Dysfunction of gut barrier is known as "leaky gut" or increased intestinal permeability. Numerous recent scientific evidences showed the association between gut dysfunction and multiple gastrointestinal tract (GI) and non-GI diseases. Research also demonstrated that food plays a crucial role to cause or remedy gut dysfunction related to diseases. We reviewed recent articles from electronic databases, mainly PubMed. The data were based on animal models, cell models, and human research in vivo and in vitro models. In this comprehensive review, our aim focused on the relationship between dietary factors, intestinal permeability dysfunction, and related diseases. This review synthesizes currently available literature and is discussed in three parts: (a) the mechanism of gut barrier and function, (b) food and dietary supplements that may promote gut health, and food or medication that may alter gut function, and (c) a table that organizes the synthesized information by general mechanisms for diseases related to leaky gut/intestinal permeability and associated dietary influences. With future research, dietary intervention could be a new target for individualized disease prevention and management.

Potential link between high FIB-4 score and chronic kidney disease in metabolically healthy men

Although the association between non-alcoholic fatty liver disease and chronic kidney disease (CKD) has been well known, it is unclear whether Fibrosis-4 (FIB-4) score is a predictor of CKD development. We performed this retrospective cohort study, with a longitudinal analysis of 5-year follow-up data from Japanese annual health check-ups. Participants with CKD (estimated glomerular filtration rate [eGFR] < 60 mL/min/1.73 m² and/or proteinuria) and a habit of alcohol consumption were excluded. The cut-off FIB-4 score was 1.30, indicating increased risk of liver fibrosis. Overall, 5353 participants (men only) were analyzed without exclusion criteria. After propensity score matching, high FIB-4 score (≥ 1.30) was not an independent risk factor for incident CKD (odds ratio [OR] 1.57; 95% confidence interval [CI] 0.97-2.56). However, high FIB-4 score was a significant risk factor for CKD in non-obese (OR 1.92; 95% CI 1.09-3.40), non-hypertensive (OR 2.15; 95% CI 1.16-3.95), or non-smoking (OR 1.88; 95% CI 1.09-3.23) participants. In these participants, FIB-4 score was strongly associated with eGFR decline in the multiple linear regression analysis (β = - 2.8950, P = 0.011). Therefore, a high FIB-4 score may be significantly associated with CKD incidence after 5 years in metabolically healthy participants.

Pre-transplant Ratio of Firmicutes/Bacteroidetes of Gut Microbiota as a Potential Biomarker of Allograft Rejection in Renal Transplant Recipients

The advent of technologies has made allogenic transplantation a potential curative therapy for end-stage renal diseases, but the episodes of rejection still remain as one of the challenges in the post-transplant scenario. In the recent years, several human and animal studies have elucidated that gut microbial dysbiosis is closely linked with allogenic transplantation and post-transplant complications. But most of the studies focused on the use of high through-put sequencing technologies to analyze gut microbiota despite of its high cost, analysis and time constraints. Hence, in this work we aimed to study the impact of the two dominant gut phyla Firmicutes and Bacteroidetes on 38 renal transplant recipients, before and after transplantation and to find its association with allograft rejection. Significant changes (p<0.01) were observed in the relative abundances of the phyla Firmicutes and Bacteroidetes at pre- and post-transplant period. We have also found that the recipients who had an increase in Firmicutes/Bacteroidetes (F/B) ratio before transplant were highly prone to rejection in the first-year post-transplant. The Receiver Operating Characteristic (ROC) curve analysis has shown that the ratio of F/B were able to discriminate between rejection and non-rejection cases with an Area under the ROC Curve (AUC) of 0.91. Additionally, we observed that the ratio of F/B have reduced during the time of rejection postulating that gut microbial dysbiosis has more association with rejection. Thus, the assessment of F/B ratio using qPCR would be of a more practical approach for diagnosis and monitoring of graft function in a cost-effective and timely manner.

Correlation of inflammatory biomarkers with the diversity of Bacteroidaceae, Bifidobacteriaceae, Prevotellaceae and Lactobacillaceae families in the intestinal microbiota of patients with end stage renal disease

PURPOSE

Serum levels of inflammatory cytokines and uremic toxins, and their inter-correlations with the diversity of Bacteroidaceae, Bifidobacteriaceae, Prevotellaceae and Lactobacillaceae families in intestinal microbiota were investigated in patients with end stage renal disease (ESRD).

METHODS

Stool and blood samples from 20 ESRD patients on maintenance hemodialysis were collected. DNA genome of the bacterial composition of the stool samples was extracted and evaluated by the sequencing analysis of 16S rRNA genes. Serum levels of inflammatory cytokines and uremic toxins were then analyzed.

RESULTS

The mean serum concentrations of TNF-α, IL-6, indoxyl sulfate (IS) and p-cresol (PC) were 305.99 ​± ​12.03 ​ng/L, 159.95 ​± ​64.22 ​ng/L, 36.76 ​± ​5.09 ​μg/mL and 0.39 ​± ​0.15 ​μg/mL, respectively. The most significant positive correlation was observed between Prevotellaceae family and total antioxidant capacity (TAC), Lactobacilli species and CRP and PC, as well as Scardovia wiggsiae and IS (p ​< ​0.001). A negative correlation was also found between Bacteroides clarus and PC. Patients with ESRD on maintenance hemodialysis had elevated levels of PC and IS and increased levels of the inflammatory markers. The most positive correlation was found between microbiota and CRP and PC, while the most negative one was between microbiota and IL-1 and TAC.

CONCLUSIONS

The abundance and diversity of Bacteroidaceae, Bifidobacteriaceae, Prevotellaceae and Lactobacillaceae families and their correlations with clinical parameters could provide benefits in the ESRD patients but they could not promote the symptoms.

Curcumin Supplementation (Meriva®) Modulates Inflammation, Lipid Peroxidation and Gut Microbiota Composition in Chronic Kidney Disease

Chronic kidney disease (CKD) subjects suffer from high risk of cardiovascular mortality, and any intervention preventing the progression of CKD may have an enormous impact on public health. In the last decade, there has been growing awareness that the gut microbiota (GM) can play a pivotal role in controlling the pathogenesis of systemic inflammatory state and CKD progression. To ameliorate the quality of life in CKD subjects, the use of dietary supplements has increased over time. Among those, curcumin has demonstrated significant in vitro anti-inflammatory properties. In this pilot study, 24 CKD patients and 20 healthy volunteers were recruited. CKD patients followed nutritional counselling and were supplemented with curcumin (Meriva^®) for six months. Different parameters were evaluated at baseline and after 3-6 months: uremic toxins, metagenomic of GM, and nutritional, inflammatory, and oxidative status. Curcumin significantly reduced plasma pro-inflammatory mediators (CCL-2, IFN-γ, and IL-4) and lipid peroxidation. Regarding GM, after 6 months of curcumin supplementation, Escherichia-Shigella was significantly lower, while Lachnoclostridium was significant higher. Notably, at family level, Lactobacillaceae spp. were found significantly higher in the last 3 months of supplementation. No adverse events were observed in the supplemented group, confirming the good safety profile of curcumin phytosome after long-term administration.

Higher dietary inflammatory index is associated with increased all-cause mortality in adults with chronic kidney disease

BACKGROUND

Diet property grounded on inflammatory potential, evaluated by the dietary inflammatory index (DII), has been proven to be connected with mortality, while studies of adults with chronic kidney disease (CKD) are scarce.

OBJECTIVE

The purpose of this research was to evaluate the interrelationships between DII and all-cause mortality among adults with CKD.

METHODS

In the National Health and Nutrition Examination Survey (NHANES) 2001-2006, we identified and evaluated data of 4,554 adults with CKD. DII scores were calculated from 24 h of dietary consumption at baseline. Vital status was followed through 31 December 2015. The association of all-cause mortality with DII score was assessed using the Kaplan-Meier curve and the Cox regression analysis.

RESULTS

After an average follow-up of 132.103 months, a total of 1,246 (27.36%) deaths were recorded. The death rates in the DII tertile categories were 24.04, 26.81, and 31.23%, respectively. The Kaplan-Meier curve showed increased death risks for the high DII tertile as compared with the low DII tertile. After we adjusted for a broad range of possible confounders, the estimation between extreme tertiles of DII scores presented a positive and significant association with all-cause mortality [hazard ratio (HR): 1.21, 95% CI: 1.05-1.39].

CONCLUSION

Our results confirm the hypothesis that proinflammatory diets contribute to the increased all-cause mortality in adults with CKD.

Specific alterations in gut microbiota in patients with chronic kidney disease: an updated systematic review

BACKGROUND

Emerging evidence demonstrates that gut dysbiosis is implicated in the pathogenesis of chronic kidney disease (CKD) with underlying mechanisms involving mucosal and/or systematic immunity or metabolic disorders. However, the profile of gut microbiota in patients with CKD has not been completely explored.

METHODS

Databases from their date of inception to 31 March 2020 were systematically searched for case-control or cross-sectional studies comparing the gut microbial profiles in adult patients with CKD or end-stage renal disease (ESRD) with those in healthy controls. Quantitative analysis of alterations in gut microbial profiles was conducted.

RESULTS

Twenty-five studies with a total of 1436 CKD patients and 918 healthy controls were included. The present study supports the increased abundance of, phylum Proteobacteria and Fusobacteria, genus Escherichia_Shigella, Desulfovibrio, and Streptococcus, while lower abundance of genus Roseburia, Faecalibacterium, Pyramidobacter, Prevotellaceae_UCG-001, and Prevotella_9 in patients with CKD; and increased abundance of phylum Proteobacteria, and genus Streptococcus and Fusobacterium, while lower abundance of Prevotella, Coprococcus, Megamonas, and Faecalibacterium in patients with ESRD. Moreover, higher concentrations of trimethylamine-N-oxide and p-cresyl sulfate and lower concentrations of short-chain fatty acids were observed. Gut permeability in patients with CKD was not determined due to the heterogeneity of selected parameters.

CONCLUSIONS

Specific alterations of gut microbial parameters in patients with CKD were identified. However, a full picture of the gut microbiota could not be drawn from the data due to the differences in methodology, and qualitative and incomplete reporting of different studies.

Roux-en-Y gastric bypass potentially improved intestinal permeability by regulating gut innate immunity in diet-induced obese mice

Roux-en-Y gastric bypass (RYGB) has been demonstrated to be the most effective treatment for morbid obesity, yet the impact of RYGB on intestinal permeability is not fully known. In this work, we subjected obese mice to RYGB and sham operation procedures. Serum lipopolysaccharide (LPS) level, inflammatory cytokines and intestinal permeability were measured at 8 weeks post surgery. In contrast to sham surgery, RYGB reduced body weight, improved glucose tolerance and insulin resistance, and decreased serum levels of LPS, IL6 and TNFα. Intestinal permeability of the common limb and colon was significantly improved in the RYGB group compared to the sham group. The mRNA levels of IL1β, IL6, and TLR4 in the intestine were significantly decreased in the RYGB group compared with the sham group. The expression levels of intestinal islet-derived 3β (REG3β), islet-derived 3γ (REG3γ) and intestinal alkaline phosphatase (IAP) were higher in the RYGB group than in the sham group. In conclusion, in a diet-induced obesity (DIO) mouse model, both decreased intestinal permeability and attenuated systemic inflammation after RYGB surgery were associated with improved innate immunity, which might result from enhanced production of IAP and antimicrobial peptides.

Association of Sarcopenia and Gut Microbiota Composition in Older Patients with Advanced Chronic Kidney Disease, Investigation of the Interactions with Uremic Toxins, Inflammation and Oxidative Stress

Sarcopenia is a prevalent condition in chronic kidney disease (CKD). We determined gut microbiota (gMB) composition in CKD patients with or without sarcopenia. Furthermore, we investigated whether in these patients, there was any association between gMB, uremic toxins, inflammation and oxidative stress. We analyzed gMB composition, uremic toxins (indoxyl sulphate and p-cresyl sulphate), inflammatory cytokines (interleukin 10, tumor necrosis factor α, interleukin 6, interleukin 17, interleukin 12 p70, monocyte chemoattractant protein-1 and fetuin-A) and oxidative stress (malondialdehyde) of 64 elderly CKD patients (10 < eGFR < 45 mL/min/1.73 m², not on dialysis) categorized as sarcopenic and not-sarcopenic. Sarcopenia was defined according to European Working Group on Sarcopenia in Older People 2 criteria. Sarcopenic patients had a greater abundance of the Micrococcaceae and Verrucomicrobiaceae families and of Megasphaera, Rothia, Veillonella, Akkermansia and Coprobacillus genera. They had a lower abundance of the Gemellaceae and Veillonellaceae families and of Acidaminococcus and Gemella genera. GMB was associated with uremic toxins, inflammatory cytokines and MDA. However, uremic toxins, inflammatory cytokines and MDA were not different in sarcopenic compared with not-sarcopenic individuals, except for interleukin 10, which was higher in not-sarcopenic patients. In older CKD patients, gMB was different in sarcopenic than in not-sarcopenic ones. Several bacterial families and genera were associated with uremic toxins and inflammatory cytokines, although none of these latter substantially different in sarcopenic versus not-sarcopenic patients.

Uremic Toxins, Oxidative Stress, Atherosclerosis in Chronic Kidney Disease, and Kidney Transplantation

Patients with chronic kidney disease (CKD) are at a high risk for cardiovascular disease (CVD), and approximately half of all deaths among patients with CKD are a direct result of CVD. The premature cardiovascular disease extends from mild to moderate CKD stages, and the severity of CVD and the risk of death increase with a decline in kidney function. Successful kidney transplantation significantly decreases the risk of death relative to long-term dialysis treatment; nevertheless, the prevalence of CVD remains high and is responsible for approximately 20-35% of mortality in renal transplant recipients. The prevalence of traditional and nontraditional risk factors for CVD is higher in patients with CKD and transplant recipients compared with the general population; however, it can only partly explain the highly increased cardiovascular burden in CKD patients. Nontraditional risk factors, unique to CKD patients, include proteinuria, disturbed calcium, and phosphate metabolism, anemia, fluid overload, and accumulation of uremic toxins. This accumulation of uremic toxins is associated with systemic alterations including inflammation and oxidative stress which are considered crucial in CKD progression and CKD-related CVD. Kidney transplantation can mitigate the impact of some of these nontraditional factors, but they typically persist to some degree following transplantation. Taking into consideration the scarcity of data on uremic waste products, oxidative stress, and their relation to atherosclerosis in renal transplantation, in the review, we discussed the impact of uremic toxins on vascular dysfunction in CKD patients and kidney transplant recipients. Special attention was paid to the role of native and transplanted kidney function.

Microbiome modulation to correct uremic toxins and to preserve kidney functions

PURPOSE OF REVIEW

The association between dysbiosis and CKD is well established. This review focuses on the current understanding of microbiome, in normal individuals and CKD patients, in order to hypothesize how to correct uremic toxins levels and preserve the renal function and reduce associated comorbidities. Here we discuss our current opinion on microbiome modulation in order to manage the CKD-associated dysbiosis.

RECENT FINDINGS

Emerging evidence confirms the role of gut microbiome in the progression of CKD. In this scenario, the need is felt to set up multifaceted approaches for dysbiosis management. Among many strategies able to improve gut wellness, a crucial approach is represented by the functional nutrition. At the same time, drug-based treatments show significant results in microbiome modulation. Furthermore, we examine here the potentialities of fecal microbiome transplantation (FMT) in CKD, an approach currently applied in Clostridium difficile infection.

SUMMARY

The gut microbiome plays a pivotal role in the pathophysiology of CKD. The vicious cycle triggered by kidney function decline leads to gut dysbiosis. Considering the gut microbiome as a therapeutic target in CKD, multiple approaches aimed at its modulation should be envisioned to preserve kidney function. Dietary interventions and pharmacological strategies are able to improve microbiome dysbiosis, oxidative stress and fibrosis. Additionally, FMT could represent a promising novel therapy in the management of CKD-associated dysbiosis.

Nutrition-Based Management of Inflammaging in CKD and Renal Replacement Therapies

Access to renal transplantation guarantees a substantial improvement in the clinical condition and quality of life (QoL) for end-stage renal disease (ESRD) patients. In recent years, a greater number of older patients starting renal replacement therapies (RRT) have shown the long-term impact of conservative therapies for advanced CKD and the consequences of the uremic milieu, with a frail clinical condition that impacts not only their survival but also limits their access to transplantation. This process, referred to as “inflammaging,” might be reversible with a tailored approach, such as RRT accompanied by specific nutritional support. In this review, we summarize the evidence demonstrating the presence of several proinflammatory substances in the Western diet (WD) and the positive effect of unprocessed food consumption and increased fruit and vegetable intake, suggesting a new approach to reduce inflammaging with the improvement of ESRD clinical status. We conclude that the Mediterranean diet (MD), because of its modulative effects on microbiota and its anti-inflammaging properties, may be a cornerstone in a more precise nutritional support for patients on the waiting list for kidney transplantation.

Can curcumin supplementation reduce plasma levels of gut-derived uremic toxins in hemodialysis patients? A pilot randomized, double-blind, controlled study

BACKGROUND

Gut dysbiosis is common in patients with chronic kidney disease (CKD) and is closely related to inflammatory processes. Some nutritional strategies, such as bioactive compounds present in curcumin, have been proposed as an option to modulate the gut microbiota and decrease the production of uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (pCS) and indole-3 acetic acid (IAA).

OBJECTIVE

To evaluate the effects of curcumin supplementation on uremic toxins plasma levels produced by gut microbiota in patients with CKD on hemodialysis (HD).

METHODS

Randomized, double-blind trial in 28 patients [53.6 ± 13.4 years, fourteen men, BMI 26.7 ± 3.7 kg/m², dialysis vintage 37.5 (12-193) months]. Fourteen patients were randomly allocated to the curcumin group and received 100 mL of orange juice with 12 g carrot and 2.5 g of turmeric and 14 patients to the control group who received the same juice but without turmeric three times per week after HD sessions for three months. IS, pCS, IAA plasma levels were measured by reverse-phase high-performance liquid chromatography RESULTS: After three months of supplementation, the curcumin group showed a significant decrease in pCS plasma levels [from 32.4 (22.1-45.9) to 25.2 (17.9-37.9) mg/L, p = 0.009], which did not occur in the control group. No statistical difference was observed in IS and IAA levels in both groups.

CONCLUSION

The oral supplementation of curcumin for three months seems to reduce p-CS plasma levels in HD patients, suggesting a gut microbiota modulation.

The influence of the prebiotic gum acacia on the intestinal microbiome composition in rats with experimental chronic kidney disease

Chronic kidney disease (CKD) is a globally common and important disease and there are evidence for a bidirectional relationship between microbiota and CKD. The aim of the study was to examine the influence of prebiotic - gum acacia (GA) on the intestinal microbiota in rats with adenine-induced CKD. Animals were randomly distributed into four equal groups (n = 6): control, adenine, GA and adenine + GA groups. CKD was induced by adenine (0.75% w/w) given in the diet daily for four weeks, and GA was administered in drinking water at a concentration of 15% w/v. The 16s rRNA analysis was performed on Illumina Miseq targeting V3-V4 region to characterize microbial composition. The abundance of Actinobacteria, Proteobacteria, Tenericutes and Verrucomicrobia bacteria was increased in adenine-induced CKD, and GA treatment successfully reversed those levels. Interestingly, alpha and beta diversity index were both reduced with GA treatment in rats with CKD. Short chain fatty acids (SCFAs) measurement and PICRUSt analysis have shown that GA treatment completely restored the depleted butyrate level and various perturbated functional pathways, respectively, in CKD rats. Taking together, our results suggest that GA supplementation has a beneficial role in treating CKD, through an increased production of butyrate, as well as its anti-inflammatory, antioxidant capacity and anti-nitrosative properties.

An LC-MS/MS analytical method for the determination of uremic toxins in patients with end-stage renal disease

End-stage renal disease (ESRD) is the last stage of chronic kidney disease, characterized by the progressive accumulation of uremic toxins (UTs). Hemodialysis is the standard approach to remove UTs from the body. Creatinine and urea levels are important indices of hemodialysis effectiveness, but the utility of those markers to estimate the removal of UTs, especially protein-binding UTs is limited. We developed an LC-MS/MS method for the quantification of UTs and to provide markers for evaluating hemodialysis effectiveness. These substances were extracted from serum samples after acetonitrile precipitation of protein and then separated on a HILIC column. The flow rate was 0.6 mL/min with a run time of 8.0 min for the negative ion mode and positive ion mode each. In this study 26 UTs were determined in normal subjects and in patients with ESRD before and after hemodialysis; serum levels were significantly higher in patients with ESRD than in subjects with normal renal function. A significant decrease in a variety of serum UTs were observed in patients after dialysis treatment, but no change in the levels of orotic acid, CMPF, kynurenic acid, p-cresol sulfate, phenyl-β-d-glucuronide, 4-ethylphenyl sulfate and 3-indolyl-β-d-glucopyranoside was found. These results show that some UTs could not be completely removed by hemodialysis. In addition, some biomarkers of different types of UTs are proposed for evaluating hemodialysis effectiveness.

Impact of gut microbiota: How it could play roles beyond the digestive system on development of cardiovascular and renal diseases

In recent years, a significant interest in gut microbiota-host crosstalk has increased due to the involvement of gut bacteria on host health and diseases. Gut dysbiosis, a change in the gut microbiota composition alters host-microbiota interactions and induces gut immune dysregulation that have been associated with pathogenesis of several diseases, including cardiovascular diseases (CVD) and chronic kidney diseases (CKD). Gut microbiota affect the host, mainly through the immunological and metabolism-dependent and metabolism-independent pathways. In addition to these, the production of trimethylamine (TMA)/trimethylamine N-oxide (TMAO), uremic toxins and lipopolysaccharides (LPS) by gut microbiota are involved in the pathogenesis of CVD and CKD. Given the current approaches and challenges that can reshape the bacterial composition by restoring the balance between host and microbiota. In this review, we discuss the complex interplay between the gut microbiota, and the heart and the kidney, and explain the gut-cardiovascular axis and gut-kidney axis on the development and progression of cardiovascular diseases and chronic kidney diseases. In addition, we discuss the interplay between gut and kidney on hypertension or cardiovascular pathology.

Rhubarb Enema Improved Colon Mucosal Barrier Injury in 5/6 Nephrectomy Rats May Associate With Gut Microbiota Modification

Chronic kidney disease (CKD) is often accompanied with colon mucosal barrier damage and gut microbiota disturbance, which strongly associate with up-regulated inflammation and kidney tubulointerstitial fibrosis. However, few interventions could protect the damaged barrier effectively. Rheum palmatum L or rhubarb is a common herbal medicine which is widely used to protect the colon mucosal barrier. In previous studies, we found that rhubarb intervention may reduce renal inflammation and tubulointerstitial fibrosis, via gut microbiota modification. However, whether intestinal barrier function could be improved by rhubarb intervention and the relationship with intestinal flora are still unknown. Therefore, we investigated the effects of rhubarb enema on intestinal barrier, and further analyzed the relationship with gut microbiota in 5/6 nephrectomy rats. Results indicated that rhubarb enema improved the intestinal barrier, regulated gut microbiota dysbiosis, suppressed systemic inflammation, and alleviated renal fibrosis. More specifically, rhubarb enema treatment inhibited the overgrowth of conditional pathogenic gut bacteria, including Akkermansia, Methanosphaera, and Clostridiaceae in CKD. The modification of gut microbiota with rhubarb intervention displayed significant correlation to intestinal barrier markers, TLR4–MyD88–NF-κB inflammatory response, and systemic inflammation. These results revealed that rhubarb enema could restore intestinal barrier by modifying several functional enteric bacteria, which may further explain the renal protection mechanism of the rhubarb enema.

Adverse Impact of Desulfovibrio spp. and Beneficial Role of Anaerostipes spp. on Renal Function: Insights from a Mendelian Randomization Analysis

Background: The microbiota composition is now considered as one of the main modifiable risk factors for health. No controlled study has been performed on the association between microbiota composition and renal function. We applied Mendelian randomization (MR) to estimate the casual impact of eight microbiota genera on renal function and the risk of chronic kidney disease (CKD). Methods: MR was implemented by using summary-level data from the largest-ever genome-wide association studies (GWAS) conducted on microbiota genera, CKD and renal function parameters. The inverse-variance weighted method (IVW), weighted median (WM)-based method, MR-Egger, MR-Robust Adjusted Profile Score (RAPS), MR-Pleiotropy RESidual Sum and Outlier (PRESSO) were applied. A sensitivity analysis was conducted using the leave-one-out method. Results: The Anaerostipes genus was associated with higher estimated glomerular filtration rate (eGFR) in the overall population (IVW: β = 0.003, p = 0.021) and non-diabetes mellitus (DM) subgroup (IVW: β = 0.003, p = 0.033), while it had a non-significant association with the risk of CKD and eGFR in DM patients. Subjects with higher abundance of Desulfovibrio spp. had a significantly lower level of eGFR (IVW: β = −0.001, p = 0.035); the same results were observed in non-DM (IVW: β = −0.001, p = 0.007) subjects. Acidaminococcus, Bacteroides, Bifidobacterium, Faecalibacterium, Lactobacillus and Megamonas had no significant association with eGFR in the overall population, DM and non-DM subgroups (IVW: p > 0.105 for all groups); they also presented no significant association with the risk of CKD (IVW: p > 0.201 for all groups). Analyses of MR-PRESSO did not highlight any outlier. The pleiotropy test, with very negligible intercept and insignificant p-value, also indicated no chance of pleiotropy for all estimations. The leave-one-out method demonstrated that the observed links were not driven by single single-nucleotide polymorphism. Conclusions: Our results suggest an adverse association of Desulfovibrio spp. and a beneficial association of Anaerostipes spp. with eGFR. Further studies using multiple robust instruments are needed to confirm these results.

Prebiotic Therapy with Inulin Associated with Low Protein Diet in Chronic Kidney Disease Patients: Evaluation of Nutritional, Cardiovascular and Psychocognitive Parameters

A relationship between dysbiotic gut microbiome and chronic kidney disease (CKD) has been recently documented; it contributes to CKD-related complications, including cardiovascular disease. Aim: We tested how a low-protein diet (LPD)-with or without oral inulin supplementation as a prebiotic-modulates some inflammatory, atherosclerosis and endothelial dysfunction indices and nutritional markers, as well as psychocognitive functions in CKD patients. We conducted a prospective, case-control study on CKD patients on conservative therapy, divided in two groups: the intervention group treated with LPD (0.6 g/kg/day) plus inulin (19 g/day) and a control group treated with LPD without inulin, for six consecutive months. Clinical and hematochemical parameters as well as instrumental, and psychocognitive assessments (by SF-36 survey and MMSE, HAM-D, BDI-II) were recorded in all the participants at baseline (T0), at three months (T1) and at six months (T2). A total of 41 patients were enrolled: 18 in the intervention group and 23 in the control group. At T2, in both groups, we observed a significant reduction of serum nitrogen and phosphorus (p ≤ 0.01) and serum uric acid (p ≤ 0.03), and an improvement in metabolic acidosis (bicarbonates, p ≤ 0.01; base excess, p ≤ 0.02). Moreover, at T2 the intervention group showed a reduction in serum insulin (p = 0.008) and fasting glucose levels (p = 0.022), HOMA-IR (p = 0.004), as well as lower total serum cholesterol (p = 0.012), triglycerides (p = 0.016), C-reactive protein (p = 0.044) and homocysteine (p = 0.044) and higher HDL (p < 0.001) with respect to baseline. We also observed a significant amelioration of some quality of life and functional status indices (SF-36 survey) among the intervention group compared to controls, without a significant improvement in the cognitive state (MMSE). On the other hand, an amelioration in mood (by HAM-D and BDI-II) was found in the intervention group and in controls (only by BID-II). In conclusion, LPD in association with oral inulin supplementation improved glycemic and lipid metabolism and ameliorated the systemic inflammatory state, likely reducing cardiovascular risk in CKD patients and this may represent a promising therapeutic option, also improving quality of life and mood.

Indoxyl sulfate induces intestinal barrier injury through IRF1-DRP1 axis-mediated mitophagy impairment

Rationale: The dysfunctional gut-kidney axis forms a vicious circle, which eventually becomes a catalyst for the progression of chronic kidney disease (CKD) and occurrence of related complications. However, the pathogenic factors of CKD-associated intestinal dysfunction and its mechanism remain elusive. Methods: We first identified the protein-bound uremic toxin indoxyl sulfate (IS) as a possible contributor to intestinal barrier injury. Transepithelial electrical resistance, permeability assay and transmission electron microscopy were carried out to evaluate the damaging effect of IS on intestinal barrier in intestinal epithelial cells, IS-injected mice and CKD mice. In vitro and in vivo experiments were performed to investigate the role of IS in intestinal barrier injury and the underlying mechanism. Finally, CKD mice treated with AST-120 (an oral adsorbent for IS) and gene knockout mice were used to verify the mechanism and to explore possible interventions for IS-induced intestinal barrier injury. Results: Transepithelial electrical resistance and the expressions of tight junction-related genes were significantly suppressed by IS in intestinal epithelial cells. In vitro experiments demonstrated that IS inhibited the expression of dynamin-related protein 1 (DRP1) and mitophagic flux, whereas DRP1 overexpression attenuated IS-induced mitophagic inhibition and intestinal epithelial cell damage. Furthermore, IS suppressed DRP1 by upregulating the expression of interferon regulatory factor 1 (IRF1), and IRF1 could directly bind to the promoter region of DRP1. Additionally, the decreased expression of DRP1 and autophagosome-encapsulated mitochondria were observed in the intestinal tissues of CKD patients. Administration of AST-120 or genetic knockout of IRF1 attenuated IS-induced DRP1 reduction, mitophagic impairment and intestinal barrier injury in mice. Conclusions: These findings suggest that reducing IS accumulation or targeting the IRF1-DRP1 axis may be a promising therapeutic strategy for alleviating CKD-associated intestinal dysfunction.

NAFLD as a driver of chronic kidney disease

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are worldwide public health problems, affecting up to 25-30% (NAFLD), and up to 10-15% (CKD) of the general population. Recently, it has also been established that there is a strong association between NAFLD and CKD, regardless of the presence of potential confounding diseases such as obesity, hypertension and type 2 diabetes. Since NAFLD and CKD are both common diseases that often occur alongside other metabolic conditions, such as type 2 diabetes or metabolic syndrome, elucidating the relative impact of NAFLD on the risk of incident CKD presents a substantial challenge for investigators working in this research field. A growing body of epidemiological evidence suggests that NAFLD is an independent risk factor for CKD and recent evidence also suggests that associated factors such as metabolic syndrome, dysbiosis, unhealthy diets, platelet activation and processes associated with ageing could also contribute mechanisms linking NAFLD and CKD. This narrative review provides an overview of the literature on: a) the evidence for an association and causal link between NAFLD and CKD and b) the underlying mechanisms by which NAFLD (and factors strongly linked with NAFLD) may increase the risk of developing CKD.

The Regulation of Host Intestinal Microbiota by Polyphenols in the Development and Prevention of Chronic Kidney Disease

Polyphenols are essential antioxidants in our regular diet, and have shown potential antibacterial effects. Other important biological effects, such as anticancer or antibacterial activities, have been demonstrated by some polyphenols. In recent years, the benefits of polyphenols to human health have attracted increasing attention from the scientific community. Recent studies have shown that polyphenols such as anthocyanin, catechin, chlorogenic acid, and resveratrol can inhibit pathogenic bacteria such as Escherichia coli and Salmonella to help regulate intestinal microflora. An imbalance of intestinal microflora and the destruction of intestinal barrier function have been found to have a potential relationship with the occurrence of chronic kidney disease (CKD). Specifically, they can aberrantly trigger the immune system to cause inflammation, increase the production of uremic toxins, and further worsen the condition of CKD. Therefore, the maintenance of intestinal microflora and the intestinal tract in a stable and healthy state may be able to "immunize" patients against CKD, and treat pre-existing disease. The use of common antibiotics may lead to drug resistance in pathogens, and thus beneficial polyphenols may be suitable natural substitutes for antibiotics. Herein we review the ability of different polyphenols, such as anthocyanin, catechin, chlorogenic acid, and resveratrol, to regulate intestinal microorganisms, inhibit pathogenic bacteria, and improve inflammation. In addition, we review the ability of different polyphenols to reduce kidney injury, as described in recent studies.

Gut microbiota; an overlooked effect of phosphate binders

Hyperphosphatemia is a mineral bone-disease that increases cardiovascular complications and all-cause mortality in chronic kidney disease (CKD) patients. Oral phosphate binders absorb the dietary phosphate to prevent its high plasma levels. Moreover, they can adsorb some uremic toxins and decrease inflammation. A few recent studies highlight an ignored effect of phosphate binders on gut microbiota. Phosphorous is a major nutrient for survival and reproduction of bacteria and its intestinal concentration may impact the activity and composition of the gut microbiota. CKD is a state of an altered gut microbiome and bacterial-derived uremic toxins stimulate cardiovascular disease and systemic inflammation. The identification of the impact of phosphate binders on gut opens a new era in nephrology and fill the existing gap in interpretation of beneficial effects of phosphate binders. This review aims to highlight the impact of oral phosphate binders on the gut microbiome in CKD.

Effect of Low-Protein Diet and Inulin on Microbiota and Clinical Parameters in Patients with Chronic Kidney Disease

Introduction: The gut microbiota has coevolved with humans for a mutually beneficial coexistence and plays an important role in health and disease. A dysbiotic gut microbiome may contribute to progression to chronic kidney disease (CKD) and CKD-related complications such as cardiovascular disease. Microbiota modulation through the administration of prebiotics may represent an important therapeutic target. Aim: We sought to evaluate the effects of a low-protein diet (LPD) (0.6 g/kg/day) with or without the intake of the prebiotic inulin (19 g/day) on microbiota and clinical parameters in CKD patients. Materials and Methods: We performed a longitudinal, prospective, controlled, and interventional study on 16 patients: 9 patients treated with LPD (0.6 g/kg/day) and inulin (19 g/day) and 7 patients (control group) treated only with LPD (0.6 g/kg/day). Clinical evaluations were performed and fecal samples were collected for a subsequent evaluation of the intestinal microbiota in all patients. These tests were carried out before the initiation of LPD, with or without inulin, at baseline (T0) and at 6 months (T2). The microbiota of 16 healthy control (HC) subjects was also analyzed in order to identify potential dysbiosis between patients and healthy subjects. Results: Gut microbiota of CKD patients was different from that of healthy controls. The LPD was able to significantly increase the frequencies of Akkermansiaceae and Bacteroidaceae and decrease the frequencies of Christensenellaceae, Clostridiaceae, Lactobacillaceae, and Pasteurellaceae. Only Bifidobacteriaceae were increased when the LPD was accompanied by oral inulin intake. We showed a significant reduction of serum uric acid (SUA) and C-reactive protein (CRP) in patients treated with LPD and inulin (p = 0.018 and p = 0.003, respectively), an improvement in SF-36 (physical role functioning and general health perceptions; p = 0.03 and p = 0.01, respectively), and a significant increase of serum bicarbonate both in patients treated with LPD (p = 0.026) or with LPD and inulin (p = 0.01). Moreover, in patients treated with LPD and inulin, we observed a significant reduction in circulating tumor necrosis factor alpha (TNF-α) (p = 0.041) and plasma nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX2) (p = 0.027) levels. We did not find a significant difference in the circulating levels of Interleukin (IL)-1β (p = 0.529) and IL-6 (p = 0.828) in the two groups. Conclusions: LPD, associated or not with inulin, modified gut microbiota and modulated inflammatory and metabolic parameters in patients with CKD. Our results suggest that interventions attempting to modulate the gut microbiome may represent novel strategies to improve clinical outcomes in CKD patients and may provide useful therapeutic effects.

An Automated Microrobotic Platform for Rapid Detection of C. diff Toxins

OBJECTIVE

Clostridium difficile (C. diff) infection leads to hundreds of nosocomial infections, and early diagnosis of this toxin-mediated disease is important. This paper aims to develop a microrobotic system and related methods that enable the automated and rapid detection of toxins secreted by C. diff that exist in patient's stool.

METHODS

We utilize the fluorescent magnetic spore-based microrobot (FMSM), a microscale mobile sensing tool, to efficiently detect C. diff toxins by utilizing its property of selective fluorescence responses to C. diff toxins. A plug-and-play (PnP) electromagnetic coil system integrated with fluorescence microscopy is developed for actuation, control and observation of FMSMs. In order to track in real time and accurately obtain the fluorescence parameters of a FMSM under varied background noise in fluorescence signal, an image gradient-based method is proposed. For accelerating the FMSM-toxin interaction in different samples, an automated navigation control scheme for the FMSM is proposed and implemented. Moreover, data post-processing methods that can optimally extract the fluorescence decay trend from the dense and fluctuated fluorescence data are developed.

RESULTS

This automated mobile detection process finishes within only 20 minutes, and the toxin detection result is immediately given by adopting the proposed system and methods. Experimental results on different biological samples confirm the qualitative detection capability. And, C. diff toxins are automatically detected from the clinical stool of infectious patients and the relationship between the fluorescence decay and the toxin concentration is calibrated for semi-quantitative detection purpose.

SIGNIFICANCE

The proposed automated microrobotic platform provides a rapid and low-cost detection technique for C. diff toxins, and it has good competency for future clinical use.

Gastrointestinal Microbiota in Patients with Chronic Kidney Disease: A Systematic Review

Emerging evidence suggests that gastrointestinal (GI) microbiota dysbiosis is associated with chronic kidney disease (CKD) and metabolite concentrations. The purpose of this systematic review was to evaluate and contextualize the research characterizing GI microbiota in patients with CKD. We searched for full-text, peer-reviewed, English studies in PubMed, Cumulative Index to Nursing and Allied Health Literature, Web of Science, and Google Scholar using a combination of MeSH terms and keywords. Eleven of the 20 studies examined GI microbiota in patients with CKD, and 9 studies focused on the effect of interventions on GI microbiota or metabolites. Available data characterizing GI microbiota in patients with CKD suggest a decline in saccharolytic bacteria and an increase in fermenters of nitrogen-containing compounds, serving as a source for circulating uremic toxins. However, studies examined limited sets of predetermined microbes, which do not reflect the entire GI microbial community and its influence on host physiology. We recommend further studies examining the entire microbial community and the potential role in regulating host physiology in CKD.

The Effect of Sevelamer on Serum Levels of Gut-Derived Uremic Toxins: Results from In Vitro Experiments and A Multicenter, Double-Blind, Placebo-Controlled, Randomized Clinical Trial

High serum levels of gut-derived uremic toxins, especially p-cresyl sulfate (pCS), indoxyl sulfate (IS) and indole acetic acid (IAA), have been linked to adverse outcomes in patients with chronic kidney disease (CKD). Sevelamer carbonate could represent an interesting option to limit the elevation of gut-derived uremic toxins. The aim of the present study was to evaluate the adsorptive effect of sevelamer carbonate on different gut-derived protein-bound uremic toxins or their precursors in vitro, and its impact on the serum levels of pCS, IS and IAA in patients with CKD stage 3b/4. For the in vitro experiments, IAA, p-cresol (precursor of pCS) and indole (precursor of IS), each at a final concentration of 1 or 10 µg/mL, were incubated in centrifugal 30 kDa filter devices with 3 or 15 mg/mL sevelamer carbonate in phosphate-buffered saline at a pH adjusted to 6 or 8. Then, samples were centrifuged and free uremic toxins in the filtrates were analyzed. As a control experiment, the adsorption of phosphate was also evaluated. Additionally, patients with stage 3b/4 CKD (defined as an eGFR between 15 and 45 mL/min per 1.73 m²) were included in a multicenter, double-blind, placebo-controlled, randomized clinical trial. The participants received either placebo or sevelamer carbonate (4.8 g) three times a day for 12 weeks. The concentrations of the toxins and their precursors were measured using a validated high-performance liquid chromatography method with a diode array detector. In vitro, regardless of the pH and concentration tested, sevelamer carbonate did not show adsorption of indole and p-cresol. Conversely, with 10 µg/mL IAA, use of a high concentration of sevelamer carbonate (15 mg/mL) resulted in a significant toxin adsorption both at pH 8 (mean reduction: 26.3 ± 3.4%) and pH 6 (mean reduction: 38.7 ± 1.7%). In patients with CKD stage 3b/4, a 12-week course of treatment with sevelamer carbonate was not associated with significant decreases in serum pCS, IS and IAA levels (median difference to baseline levels: −0.12, 0.26 and −0.06 µg/mL in the sevelamer group vs. 1.97, 0.38 and 0.05 µg/mL in the placebo group, respectively). Finally, in vitro, sevelamer carbonate was capable of chelating a gut-derived uremic toxin IAA but not p-cresol and indole, the precursors of pCS and IS in the gut. In a well-designed clinical study of patients with stage 3b/4 CKD, a 12-week course of treatment with sevelamer carbonate was not associated with significant changes in the serum concentrations of pCS, IS and IAA.

Modulation of the Gut Microbiota by Resistant Starch as a Treatment of Chronic Kidney Diseases: Evidence of Efficacy and Mechanistic Insights

Chronic kidney disease (CKD) has been associated with changes in gut microbial ecology, or "dysbiosis," which may contribute to disease progression. Recent studies have focused on dietary approaches to favorably alter the composition of the gut microbial communities as a treatment method in CKD. Resistant starch (RS), a prebiotic that promotes proliferation of gut bacteria such as Bifidobacteria and Lactobacilli, increases the production of metabolites including short-chain fatty acids, which confer a number of health-promoting benefits. However, there is a lack of mechanistic insight into how these metabolites can positively influence renal health. Emerging evidence shows that microbiota-derived metabolites can regulate the incretin axis and mitigate inflammation via expansion of regulatory T cells. Studies from animal models and patients with CKD show that RS supplementation attenuates the concentrations of uremic retention solutes, including indoxyl sulfate and p-cresyl sulfate. Here, we present the current state of knowledge linking the microbiome to CKD, we explore the efficacy of RS in animal models of CKD and in humans with the condition, and we discuss how RS supplementation could be a promising dietary approach for slowing CKD progression.

Effects of Probiotics on Inflammation and Uremic Toxins Among Patients on Dialysis: A Systematic Review and Meta-Analysis

BACKGROUND/OBJECTIVES

We performed this systematic review and meta-analysis to evaluate effects of probiotics on inflammation, uremic toxins, and gastrointestinal (GI) symptoms in end-stage renal disease (ESRD) patients.

METHODS

A literature search was conducted utilizing MEDLINE, EMBASE, and Cochrane Database from inception through October 2017. We included studies that assessed assessing effects of probiotics on inflammatory markers, protein-bound uremic toxins (PBUTs), and GI symptoms in ESRD patients on dialysis. Effect estimates from the individual study were extracted and combined utilizing random effect, generic inverse variance method of DerSimonian and Laird. The protocol for this meta-analysis is registered with PROSPERO; No. CRD42017082137.

RESULTS

Seven clinical trials with 178 ESRD patients were enrolled. There was a significant reduction in serum C-reactive protein (CRP) from baseline to post-probiotic course (≥ 2 months after treatment) with standardized mean difference (SMD) of - 0.42 (95% CI - 0.68 to - 0.16, p = 0.002). When compared to control, patients who received probiotics also had a significant higher degree of reduction in CRP level with SMDs of - 0.37 (95% CI - 0.72 to 0.03, p = 0.04). However, there were no significant changes in serum TNF-alpha or albumin with SMDs of - 0.32 (95% CI - 0.92 to 0.28, p = 0.29) and 0.16 (95% CI - 0.20 to 0.53, p = 0.39), respectively. After probiotic course, there were also significant decrease in PBUTs and improvement in overall GI symptoms (reduction in GI symptom scores) with SMDs of - 0.61 (95% CI - 1.16 to - 0.07, p = 0.03) and - 1.04 (95% CI - 1.70 to - 0.38, p = 0.002), respectively.

CONCLUSION

Our study demonstrates potential beneficial effects of probiotics on inflammation, uremic toxins, and GI Symptoms in ESRD patients. Future large-scale clinical studies are required to assess its benefits on other important clinical outcomes including patient mortality.

Influence of colonic dialysis using Gubenxiezhuo on the distribution of gut microflora in uremia rats

OBJECTIVE

This study aimed to explore the underlying function of Gubenxiezhuo dialysis on the distribution of gut microflora uremia.

METHODS

A uremia rat model was constructed, and the morphology of renal tissue was determined using the hematoxylin-eosin (H&E) staining. Moreover, the blood samples were collected and the expression of IL-1β, IL-6, and CRP was determined using enzyme-linked immunosorbent assay. Following these experiments, the gut tissues of rats were collected and the distribution of gut microbiota was explored using real-time PCR.

RESULTS

Compared with the control group, inflammatory infiltration, apoptosis, and bleeding were significantly upregulated in kidney of uremia rats, and Gubenxiezhuo dialysis could obviously ameliorate these changes. Expression of IL-1β, IL-6, and CRP were significantly elevated in uremic rats and Gubenxiezhuo could significantly attenuate these elevations (p < 0.01). In addition, Gubenxiezhuo dialysis also could attenuate the upregulations of Acinetobacter, Bacillus cereus, Proteus vulgaris, Shigella flexneri, and Escherichia coli , and the downregulation of Bifidobacterium, Lactobacillus, and Helicobacter in the uremia rats ( p < 0.05).

CONCLUSION

Gubenxiezhuo dialysis could significantly ameliorate the inflammatory to modulate the distribution of gut microbiota in uremia.

Gut microbiota-derived D-serine protects against acute kidney injury

Gut microbiota-derived metabolites play important roles in health and disease. D-amino acids and their L-forms are metabolites of gut microbiota with distinct functions. In this study, we show the pathophysiologic role of D-amino acids in association with gut microbiota in humans and mice with acute kidney injury (AKI). In a mouse kidney ischemia/reperfusion model, the gut microbiota protected against tubular injury. AKI-induced gut dysbiosis contributed to the altered metabolism of D-amino acids. Among the D-amino acids, only D-serine was detectable in the kidney. In injured kidneys, the activity of D-amino acid oxidase was decreased. Conversely, the activity of serine racemase was increased. The oral administration of D-serine mitigated the kidney injury in B6 mice and D-serine-depleted mice. D-serine suppressed hypoxia-induced tubular damage and promoted posthypoxic tubular cell proliferation. Finally, the D-serine levels in circulation were significantly correlated with the decrease in kidney function in AKI patients. These results demonstrate the renoprotective effects of gut-derived D-serine in AKI, shed light on the interactions between the gut microbiota and the kidney in both health and AKI, and highlight D-serine as a potential new therapeutic target and biomarker for AKI.

Biotic Supplements for Renal Patients: A Systematic Review and Meta-Analysis

Intestinal dysbiosis is highly pervasive among chronic kidney disease (CKD) patients and may play a key role in disease progression and complications. We performed a systematic review and meta-analysis to evaluate effects of biotic supplements on a large series of outcomes in renal patients. Ovid-MEDLINE, PubMed and CENTRAL databases were searched for randomized controlled trials (RCTs) comparing any biotic (pre-, pro- or synbiotics) to standard therapy or placebo. Primary endpoints were change in renal function and cardiovascular events; secondary endpoints were change in proteinuria/albuminuria, inflammation, uremic toxins, quality of life and nutritional status. Seventeen eligible studies (701 participants) were reviewed. Biotics treatment did not modify estimated glomerular filtration rate (eGFR) (mean difference (MD) 0.34 mL/min/1.73 m²; 95% CI −0.19, 0.86), serum creatinine (MD −0.13 mg/dL; 95% confidence interval (CI) −0.32, 0.07), C-reactive protein (MD 0.75 mg/dL; 95% CI −1.54, 3.03) and urea (standardized MD (SMD) −0.02; 95% CI −0.25, 0.20) as compared to control. Outcome data on the other endpoints of interest were lacking, sparse or in an unsuitable format to be analyzed collectively. According to the currently available evidence, there is no conclusive rationale for recommending biotic supplements for improving outcomes in renal patients. Large-scale, well-designed and adequately powered studies focusing on hard rather than surrogate outcomes are still awaited.

Does Low-Protein Diet Influence the Uremic Toxin Serum Levels From the Gut Microbiota in Nondialysis Chronic Kidney Disease Patients?

OBJECTIVES

To evaluate the effects of low-protein diet (LPD) on uremic toxins and the gut microbiota profile in nondialysis chronic kidney disease (CKD) patients.

DESIGN AND METHODS

Longitudinal study with 30 nondialysis CKD patients (stage 3-4) undergoing LPD for 6 months. Adherence to the diet was evaluated based on the calculation of protein equivalent of nitrogen appearance from the 24-hour urine analysis. Good adherence to LPD was considered when protein intake was from 90% to 110% of the prescribed amount (0.6 g/kg/day). Food intake was analyzed by the 24-hour recall method. The anthropometric, biochemical and lipid profile parameters were measured according to standard methods. Uremic toxin serum levels (indoxyl sulfate, p-cresyl sulfate, indole-3-acetic acid) were obtained by reversed-phase high-performance liquid chromatography (RP-HPLC). Fecal samples were collected to evaluate the gut microbiota profile through polymerase chain reaction and denaturing gradient gel electrophoresis. Statistical analysis was performed by the SPSS 23.0 program software.

RESULTS

Patients who adhered to the diet (n = 14) (0.7 ± 0.2 g/kg/day) presented an improvement in renal function (nonsignificant) and reduction in total and low-density lipoprotein cholesterol (183.9 ± 48.5-155.7 ± 37.2 mg/dL, P = .01; 99.4 ± 41.3-76.4 ± 33.2 mg/dL, P = .01, respectively). After 6 months of nutricional intervention, p-cresyl sulfate serum levels were reduced significantly in patients who adhered to the LPD (19.3 [9.6-24.7] to 15.5 [9.8-24.1] mg/L, P = .03), and in contrast, the levels were increased in patients who did not adhere (13.9 [8.0-24.8] to 24.3 [8.1-39.2] mg/L, P = .004). In addition, using the denaturing gradient gel electrophoresis technique, it was observed change in the intestinal microbiota profile after LPD intervention in both groups, and the number of bands was positively associated with protein intake (r = 0.44, P = .04).

CONCLUSION

LPD seems be a good strategy to reduce the uremic toxins production by the gut microbiota in nondialysis CKD patients.