Is there interaction between gut microbial profile and cardiovascular risk in chronic kidney disease patients?

Heat-treated and/or lysozyme-treated Enterococcus faecalis (FK-23) improves the progression of renal disease in a unilateral ischemia-reperfusion injury rat model

The prevalence of chronic kidney disease (CKD) is increasing owing to the elderly population. Here, we investigated the effects of heat-treated Enterococcus faecalis (FK-23) and lysozyme-treated FK-23 (LFK) on the progression of CKD in rats. A CKD model was established using male Wistar rats by subjecting them to right nephrectomy (1K), followed by ischemia and reperfusion (IR). FK-23 or LFK was fed ad libitum as a mixed diet after right nephrectomy. Animals subjected to renal ischemia-reperfusion injury (IRI) showed increased plasma creatinine and blood urea nitrogen levels. Furthermore, in the kidneys, collagen accumulation and α-smooth muscle actin, indicative of fibroblast activation and fibrosis-related gene and protein expression, increased 3 weeks after IRI. FK-23 and LFK suppressed the increase in the mRNA levels of some of these genes. The increase in oxidative stress markers, 4-hydroxy-2-nonenal, endothelial nitric oxide synthase, and nitrotyrosine in the kidney, as well as increased plasma uremic toxins after IRI, were also ameliorated by FK-23 and LFK. Metagenomic analysis of fecal samples revealed that gut microbial alteration caused by IRI was also ameliorated by LFK treatment. These results suggest that Enterococcus faecalis ingredients may improve CKD progression by suppressing oxidative stress and correcting the balance of the intestinal microflora.

Dysbiosis of Gut Microbiota in Patients with Chronic Kidney Disease

Objective The gut bacterial microbiota is altered in patients with chronic kidney disease (CKD). However, the bacterial composition at each stage of CKD is unclear in these patients, including those receiving renal replacement therapy. We herein report the changes in the gut microbiota among patients with CKD. Methods A total of 93 individuals were recruited for the study. Seventy-three patients had stage 3-5 CKD, including those receiving renal replacement therapy (CKD group), and 20 were age- and sex-matched controls (CKD stage 1-2). The gut microbiome composition was analyzed using a 16S ribosomal RNA gene-based sequencing protocol. Results At the genus level, the butyrate-producing bacteria Lachnospira, Blautia, Coprococcus, Anaerostipes, and Roseburia were more abundant in the control group (linear discriminant analysis score of >3) than in the CKD group. Lachnospira was more abundant in the control group than in patients with CKD stage 3a. Compared to the control group, multiplex butyrate-producing bacteria were deficient in patients with CKD stage 3b-5D, including in patients receiving renal replacement therapy. Conclusion Our findings highlight the fact that the gut bacterial composition, including butyrate-producing bacteria, deteriorates from CKD stage 3b. Even after renal replacement therapy, the bacterial composition did not change.

Causal relationship between gut microbiota and kidney diseases: a two-sample Mendelian randomization study

Background

The interplay between gut microbiome genera and inflammatory kidney-related diseases, such as nephrotic syndrome, glomerulonephritis, tubulo-interstitial nephritis, and chronic kidney disease, has been observed. However, the causal relationships between specific bacterial genera and these renal diseases have not been fully elucidated.

Objective

To investigate the potential causal links between different genera of the gut microbiome and the susceptibility to various renal conditions utilizing two-sample Mendelian randomization (MR) analyses.

Materials and methods

Genome-wide association study (GWAS) summary statistics of gut microbiota and inflammatory kidney-related diseases were obtained from published GWASs. Two-sample MR analyses were conducted using methods including inverse-variance weighted (IVW), MR Egger, and others to identify potential causal links between gut microbial genera and renal conditions. Sensitivity analyses, including Cochran's Q test and the MR-PRESSO global test, were performed to validate the robustness of the results and detect horizontal pleiotropy. In addition, a reverse MR analysis was conducted to assess reverse causation possibilities.

Results

By synthesizing insights from both primary and sensitivity analyses, this study unveiled critical associations of 12 bacterial genera with nephrotic syndrome, 7 bacterial genera with membranous nephropathy, 3 bacterial genera with glomerulonephritis, 4 bacterial genera with acute tubulo-interstitial nephritis, 6 bacterial genera with chronic tubulo-interstitial nephritis, and 7 bacterial genera with chronic kidney disease. Various genera were pinpointed as having either positive or negative causal relationships with these renal conditions, as evidenced by specific ranges of IVW-OR values (all P< 0.05). The congruence of the sensitivity analyses bolstered the primary findings, displaying no marked heterogeneity or horizontal pleiotropy. Notably, the reverse MR analysis with nephritis as the exposure did not reveal any causal relationships, thereby strengthening the resilience and validity of the primary associations.

Conclusion

This study explored the causal associations between several gut microbial genera and the risk of several inflammatory kidney-related diseases, uncovering several associations between specific gut microbial genera and nephrotic syndrome, membranous nephropathy, glomerulonephritis, tubulo-interstitial nephritis, and chronic kidney disease. These findings enhance our understanding of the complex interplay between the gut microbiome and kidney diseases, and they will be beneficial for early diagnosis and subsequent treatment.

Animal protein intake is directly associated with serum level of pentraxin 3 in hemodialysis patients

Inflammation plays an important role in Cardiovascular disease (CVD) pathogenesis as the main cause of mortality in hemodialysis (HD) patients. Despite the relevance of nutrition and dietary intakes for inflammation status, the role of dietary protein sources remains unclear. The aim of this study was to evaluate the association between the different types of dietary protein and pentraxin 3 (PTX3) levels in HD patients. In this multi-center cross-sectional study, 227 adult patients undergoing HD for a minimum 90 days were recruited. A validated 168-item food frequency questionnaire was used to assess dietary intakes. Also, 5 ml blood samples were collected from each patient to measure the concentration of serum PTX3. Overall, 227 patients, including 63 women and 164 men, with a mean age of 58 years, participated in this study. There was a greater intake of animal protein per kilogram dry weight among patients with higher levels of PTX3 (0.46 vs. 0.54 g/kg; P = 0.035). In contrast, consumption of total protein and plant protein per kilogram dry weight was not different across PTX3 levels. Moreover, the chance of increased PTX3 concentration was directly associated with a one-unit increase in animal protein intake per kilogram dry weight, after adjusting for confounders. We did not observe any association between one-unit increases in plant protein intake per kilogram dry weight and chance of increased PTX3. In conclusion, animal protein intake was directly associated with circulating PTX3.

Salivary microbiome in kidney diseases: A narrative review

Many research has been conducted since the microbiota's discovery that have focused on the role it plays in health and disease. Microbiota can be divided into categories like intestinal, oral, respiratory, and skin microbiota based on the specific localized areas. To maintain homeostasis and control immunological response, the microbial populations live in symbiosis with the host. On the other hand, dysbiosis of the microbiota can cause diseases including kidney diseases and the deregulation of body functioning. We discuss the current understanding of how various kidney diseases are caused by the salivary microbiome (SM) in this overview. First, we review the studies on the salivary microbiota in diverse clinical situations. The importance of the SM in diabetic kidney disease, chronic kidney disease, membranous nephropathy, and IgA nephropathy is next highlighted. We conclude that the characteristics of the SM of patients with various kidney diseases have revealed the potential of salivary microbial markers as noninvasive tool for the detection of various kidney diseases.

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 and the Ways to Correct it in Chronic Kidney Disease

Approximately 13% of the Russian population suffers from chronic kidney disease (CKD). Such a high prevalence of the disease, as well as the complexity and high cost of renal replacement therapy, explain the need for developing and implementing new approaches to treat patients at the pre-dialysis stages. The data collected in recent decades highlight the importance of gut microbiota in the progression of CKD. This review provides information about the microbiota composition in healthy individuals and patients with CKD and discusses the mechanisms of interaction in the intestine-kidney system. The article also presents the specifics of the violation of gut microbiota (GM) and correction thereof in CKD.

Gut Microbiota in Chronic Kidney Disease: From Composition to Modulation towards Better Outcomes-A Systematic Review

BACKGROUND

A bidirectional kidney-gut axis was described in patients with chronic kidney disease (CKD). On the one hand, gut dysbiosis could promote CKD progression, but on the other hand, studies reported specific gut microbiota alterations linked to CKD. Therefore, we aimed to systematically review the literature on gut microbiota composition in CKD patients, including those with advanced CKD stages and end-stage kidney disease (ESKD), possibilities to shift gut microbiota, and its impact on clinical outcomes.

MATERIALS AND METHODS

We performed a literature search in MEDLINE, Embase, Scopus, and Cochrane databases to find eligible studies using pre-specified keywords. Additionally, key inclusion and exclusion criteria were pre-defined to guide the eligibility assessment.

RESULTS

We retrieved 69 eligible studies which met all inclusion criteria and were analyzed in the present systematic review. Microbiota diversity was decreased in CKD patients as compared to healthy individuals. Ruminococcus and Roseburia had good power to discriminate between CKD patients and healthy controls (AUC = 0.771 and AUC = 0.803, respectively). Roseburia abundance was consistently decreased in CKD patients, especially in those with ESKD (p < 0.001). A model based on 25 microbiota dissimilarities had an excellent predictive power for diabetic nephropathy (AUC = 0.972). Several microbiota patterns were observed in deceased ESKD patients as compared to the survivor group (increased Lactobacillus, Yersinia, and decreased Bacteroides and Phascolarctobacterium levels). Additionally, gut dysbiosis was associated with peritonitis and enhanced inflammatory activity. In addition, some studies documented a beneficial effect on gut flora composition attributed to synbiotic and probiotic therapies. Large randomized clinical trials are required to investigate the impact of different microbiota modulation strategies on gut microflora composition and subsequent clinical outcomes.

CONCLUSIONS

Patients with CKD had an altered gut microbiome profile, even at early disease stages. Different abundance at genera and species levels could be used in clinical models to discriminate between healthy individuals and patients with CKD. ESKD patients with an increased mortality risk could be identified through gut microbiota analysis. Modulation therapy studies are warranted.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

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.

Dietary protein sources and risk of diabetic nephropathy in women: A case-control study

BACKGROUND

Several studies have investigated the association between dietary protein and the risk of diabetic nephropathy (DN); however, there is no agreement on the type of dietary protein sources that might increase the risk of DN. This study was conducted to investigate the associations between different protein sources and the odds of DN developing in Iranian women with existing type 2 diabetes.

METHODS

In this case-control study, 105 women with DN and 105 controls, matched for age and diabetes duration, were selected from the Kowsar Diabetes Clinic in Semnan, Iran. Dietary intake was assessed using a validated and reliable food frequency questionnaire. Dietary protein patterns were estimated using the factor analysis method. Multivariate logistic regression was performed to examine the association between protein patterns and the odds of developing DN.

RESULTS

Two patterns were identified: the Mediterranean-based Dietary Protein Sources (MDPS) pattern which is rich in low-fat dairy, fish, poultry, soy, and legumes, and the Western-based Dietary Protein Sources (WDPS) pattern, rich in red and processed meats, eggs, and high-fat dairy. After adjusting for several confounders, greater adherence (third vs. the first tertile) to the MDPS pattern was associated with lower odds of DN (OR = 0.03; 95 % CI: 0.00, 0.10). In contrast, a strong positive association was observed between adherence to the WDPS pattern and DN (OR = 2.81; 95 % CI: 1.09-7.21).

CONCLUSIONS

Our results show that there is a potential association between the type of protein sources consumed and the odds of DN development in women with type 2 diabetes. Further studies are needed to confirm these findings.

Probiotic fermentation of Ganoderma lucidum fruiting body extracts promoted its immunostimulatory activity in mice with dexamethasone-induced immunosuppression

Ganoderma lucidum is a legendary traditional Chinese medicine with various bioactivities. This study was conducted (a) to explore the in vitro fermentation of the water extracts of G. lucidum fruiting body with Lactobacillus acidophilus and Bifidobacterium breve and (b) to investigate the effect of fermentation broth (GLFB) on dexamethasone (DEX)-induced immunosuppressed mice. Our results demonstrated that probiotic fermentation of G. lucidum fruiting body extracts underwent structural changing of major ganoderic acid components, such as ganoderic acid A (GA) into GC2, and this fermentation process involves changing of several metabolic pathways in the probiotic strains. GLFB could significantly improve the immunity, intestinal integrity, and gut microbiota dysbiosis in DEX-treated mice, and the immunostimulatory activity of GLFB was found closely related to its direct regulation on the expansion of CD4⁺ T cells in Peyer's patches of mice. These data implied that probiotic fermentation of G. lucidum fruiting body extracts promoted its immunostimulatory activity via biotransformation of components such as GA. This research provides a theoretical support for the development and application of G. lucidum fermentation by probiotics.

Molecular Mechanisms of Obesity-Linked Cardiac Dysfunction: An Up-Date on Current Knowledge

Obesity is defined as excessive body fat accumulation, and worldwide obesity has nearly tripled since 1975. Excess of free fatty acids (FFAs) and triglycerides in obese individuals promote ectopic lipid accumulation in the liver, skeletal muscle tissue, and heart, among others, inducing insulin resistance, hypertension, metabolic syndrome, type 2 diabetes (T2D), atherosclerosis, and cardiovascular disease (CVD). These diseases are promoted by visceral white adipocyte tissue (WAT) dysfunction through an increase in pro-inflammatory adipokines, oxidative stress, activation of the renin-angiotensin-aldosterone system (RAAS), and adverse changes in the gut microbiome. In the heart, obesity and T2D induce changes in substrate utilization, tissue metabolism, oxidative stress, and inflammation, leading to myocardial fibrosis and ultimately cardiac dysfunction. Peroxisome proliferator-activated receptors (PPARs) are involved in the regulation of carbohydrate and lipid metabolism, also improve insulin sensitivity, triglyceride levels, inflammation, and oxidative stress. The purpose of this review is to provide an update on the molecular mechanisms involved in obesity-linked CVD pathophysiology, considering pro-inflammatory cytokines, adipokines, and hormones, as well as the role of oxidative stress, inflammation, and PPARs. In addition, cell lines and animal models, biomarkers, gut microbiota dysbiosis, epigenetic modifications, and current therapeutic treatments in CVD associated with obesity are outlined in this paper.

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.

Resistant starch type-2 enriched cookies modulate uremic toxins and inflammation in hemodialysis patients: a randomized, double-blind, crossover and placebo-controlled trial

BACKGROUND

The aim of this study was to evaluate the effect of resistant starch (RS) enriched cookies supplementation on mRNA expression of nuclear transcription factors (nuclear erythroid 2-related factor, Nrf2; nuclear factor kappa-B, NF-κB), involved with inflammation and on uremic toxins levels produced by the gut microbiota in hemodialysis (HD) patients.

METHODS

A randomized, double-blind, placebo-controlled crossover study with 26 HD patients was conducted. The patients were assigned to either resistant starch enriched cookies (16 g of RS per day) or placebo cookies supplementation during the first four weeks. After the washout period, patients were supplemented again, in the form of a crossover, for another 4 weeks. Nrf2, NF-κB, and antioxidant enzymes mRNA expression were measured by rt-PCR and protein expression by western blotting assay from isolated peripheral blood mononuclear cells (PBMC). Oxidative stress and inflammatory biomarkers, as well as uremic toxins, were evaluated. Intention-to-treat analysis was performed, using the proc mixed procedure in SAS.

RESULTS

In RS group, post-treatment mean mRNA Nrf2 expression was market increased from baseline values, associated with a high expression of NQO1 protein. Besides, IS plasma levels were reduced in the RS group. No significant difference was observed in the placebo group.

CONCLUSION

Our results suggested that resistant starch enriched cookies may be a good nutritional strategy to reduce indoxyl sulfate levels derived from the gut microbiota and also attenuate the inflammation in hemodialysis patients.

The Effects of High-Protein Diets on Kidney Health and Longevity

Although high-protein diets continue to be popular for weight loss and type 2 diabetes, evidence suggests that worsening renal function may occur in individuals with-and perhaps without-impaired kidney function. High dietary protein intake can cause intraglomerular hypertension, which may result in kidney hyperfiltration, glomerular injury, and proteinuria. It is possible that long-term high protein intake may lead to de novo CKD. The quality of dietary protein may also play a role in kidney health. Compared with protein from plant sources, animal protein has been associated with an increased risk of ESKD in several observational studies, including the Singapore Chinese Health Study. Potential mediators of kidney damage from animal protein include dietary acid load, phosphate content, gut microbiome dysbiosis, and resultant inflammation. In light of such findings, adopting current dietary approaches that include a high proportion of protein for weight reduction or glycemic control should be considered with care in those at high risk for kidney disease. Given the possibility of residual confounding within some observational studies and the conflicting evidence from previous trials, long-term studies including those with large sample sizes are warranted to better ascertain the effects of high protein intake on kidney health.

Pilot Study of Probiotic Supplementation on Uremic Toxicity and Inflammatory Cytokines in Chronic Kidney Patients

Background:

Bacterial metabolism contributes to the generation of uremic toxins in patients with chronic kidney disease (CKD). It has been investigated the use of probiotics in the reduction of uremic toxins intestinal production.

Objective:

The aim of this pilot study was to evaluate the effect of probiotic supplementation on reducing the production of uremic toxins and the inflammatory profile of CKD patients.

Methods:

We performed a randomized, blind, placebo-controlled, crossover study on patients with CKD stages 3 and 4. The intervention was a probiotic formulation composed of Lactobacillus acidophilus strains given orally three times a day for 3 months. Changes in uremic toxins (p-Cresylsulfate and Indoxyl Sulfate) and serum inflammatory cytokines were the primary endpoints.

Results:

Of the 44 patients randomized, 25 completed the study (mean age 51 ± 9.34, 64% female, mean eGFR 36 ± 14.26 mL/min/1.73m², mean BMI 28.5 ± 5.75 kg/m²). At 3 months, there were no significant changes in any of the studied biomarkers including p-cresylsulfate (p = 0.57), Indoxyl sulfate (p = 0.08) and interleukin-6 (p = 0.55).

Conclusion:

Lactobacillus acidophilus strains given as probiotic were not able to reduce serum levels of uremic toxins and biomarkers of inflammation in CKD patients in stage 3 and 4.

Plant-Based Diets, the Gut Microbiota, and Trimethylamine N-Oxide Production in Chronic Kidney Disease: Therapeutic Potential and Methodological Considerations

High circulating trimethylamine-N-oxide (TMAO) is associated with an increased risk of cardiovascular disease and mortality in people with chronic kidney disease (CKD). In individuals with CKD, reduced kidney function leads to decreased excretion of TMAO, which results in accumulation in the circulation. Higher circulating TMAO has been linked to higher intake of animal-based foods in omnivorous diets. Thus, plant-based diets have been suggested as an intervention to slow the progression of CKD and reduce cardiovascular risk, perhaps explained in part by reduced TMAO production. This article reviews the current evidence on plant-based diets as a dietary intervention to decrease gut-derived TMAO production in patients with CKD, while highlighting methodological issues that present challenges to advancing research and subsequent translation of this approach. Overall, we find that plant-based diets are promising for reducing gut-derived TMAO production in patients with CKD but that further interventional studies are warranted.

Effect of Synbiotic and Probiotic Supplementation on Serum Levels of Endothelial Cell Adhesion Molecules in Hemodialysis Patients: a Randomized Control Study

The aim of this study was to investigate the effect of synbiotic and probiotic supplementation on serum vascular dysfunction and necrosis markers in hemodialysis (HD) patients. In this randomized, double-blind, placebo-controlled trial, 75 HD patients were randomly assigned to either the synbiotic or probiotic or placebo group. The patients in the synbiotic group received 15 g of prebiotics and 5 g probiotic powder containing Lactobacillus acidophilus strain T16 (IBRC-M10785), Bifidobacterium bifidum strain BIA-6, Bifidobacterium lactis strain BIA-6, Bifidobacterium longum strain LAF-5 (2.7 × 10⁷ CFU/g each) in sachets (n = 25), whereas the probiotic group received 5 g probiotics same to the first group with 15 g of maltodextrin powder in sachets (n = 25) and the placebo group received 20 g of maltodextrin powder in sachets (n = 25) for 12 weeks. At baseline and the end of the study, serum concentrations of soluble intercellular adhesion molecule type 1 (sICAM-1), soluble vascular cell adhesion molecule type 1 (sVCAM-1), cytokeratin 18 (CK-18) as the necrosis marker, uric acid, and phosphate levels were measured. Feces also were collected for microbiota colony counting. Serum ICAM-1 level reduced significantly in the synbiotic group after the intervention period (P = 0.02), and this reduction was significantly different in the synbiotic group in comparison to the placebo group (P = 0.03). Serum levels of VCAM-1 and CK-18 were not significantly different between the groups. However, the reduction in serum levels of VCAM-1 in the synbiotic group was significantly higher in comparison to the placebo group (P = 0.01). Multivariate linear regression analysis revealed that ∆ phosphate was the sole independent determinant of ∆ICAM-1 (P = 0 < 001). The study indicated that synbiotic supplementation reduced serum ICAM-1 level, which is a risk factor for cardiovascular diseases in HD patients, but has no effect on the necrosis marker. Trial registration: www.irct.ir (IRCT2017041233393N1).

Dietary intake of tyrosine and phenylalanine, and p-cresyl sulfate plasma levels in non-dialyzed patients with chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) present an imbalance of the gut microbiota composition, leading to increased production of uremic toxins like p-cresyl sulfate (PCS), product from bacterial fermentation of the amino acids tyrosine (Tyr) and phenylalanine (Phe) from the diet. Thus, diet may be a determinant in the uremic toxins levels produced by the gut microbiota. The aim of this study was to evaluate the possible relationship between Tyr and Phe intake and PCS plasma levels in non-dialysis CKD patients.

METHODS

Twenty-seven non-dialysis CKD patients (stages 3 and 4) without previous nutritional intervention were evaluated. The dietary intake was evaluated using a 24-hour recall, 3-day food record and protein intake was also estimated by Protein Nitrogen Appearance (PNA). The plasma levels of PCS were measured using reverse phase high performance liquid chromatography.

RESULTS

The evaluated patients (GRF, 34.8 ± 12.4 mL/min, 54.2 ± 14.3 years, BMI, 29.3 ± 6.1 kg/m2) presented mean protein intake of 1.1 ± 0.5 g/kg/day), Tyr of 4.5 ± 2.4 g/day and Phe of 4.6 ± 2.5 g/day. PCS plasma levels (20.4 ± 15.5 mg/L) were elevated and positively associated with both, Tyr (r = 0.58, p = 0.002) and Phe intake (r = 0.53, p = 0.005), even after adjustments for eGFR and age.

CONCLUSION

This study suggests that the diet is an important modulator of the uremic toxins plasma levels produced by the gut microbiota, in non-dialysis CKD patients.

Gut microbiota composition and frailty in elderly patients with Chronic Kidney Disease

Background

Frailty is common in older patients affected by chronic kidney disease (CKD). Since gut microbiota (gMB) may contribute to frailty, we explored possible associations between gMB and frailty in CKD.

Methods

We studied 64 CKD patients (stage 3b-4), categorized as frail (F, 38) and not frail (NF, 26) according to Fried criteria, and 15 controls (C), all older than 65 years. In CKD we assessed serum C-reactive protein, blood neutrophil/lymphocyte ratio, Malnutrition-inflammation Score (MIS); gMB was studied by denaturing gel gradient electrophoresis (DGGE), high-throughput sequencing (16S r-RNA gene), and quantitative real-time PCR (RT-PCR).

Results

No differences in alpha diversity between CKD and C and between F and NF patients emerged, but high-throughput sequencing showed significantly higher abundance of potentially noxious bacteria (Citrobacter, Coprobacillus, etc) and lower abundance of saccharolytic and butyrate-producing bacteria (Prevotella spp., Faecalibacterium prausnitzii, Roseburia spp.), in CKD respect to C. Mogibacteriaceae family and Oscillospira genus abundance was positively related to inflammatory indices in the whole CKD cohort, while that of Akkermansia, Ruminococcus and Eubacterium genera was negatively related. Compared with NF, in F there was a higher abundance of some bacteria (Mogibacteriacee, Coriobacteriacee, Eggerthella, etc), many of which have been described as more abundant in other diseases.

Conclusions

These results suggest that inflammation and frailty could be associated to gMB modifications in CKD.

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.

Are There Potential Applications of Fecal Microbiota Transplantation beyond Intestinal Disorders?

Intestinal microbial dysbiosis is associated with various intestinal and extraintestinal disorders. Fecal microbiota transplantation (FMT), a type of fecal bacteriotherapy, is considered an effective therapeutic option for recurrent Clostridium difficile infection (rCDI) and also has important value in other intestinal diseases including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). The purpose of this review is to discuss promising therapeutic value in extraintestinal diseases associated with gut microbial dysbiosis, including liver, metabolic, chronic kidney, neuropsychiatric, allergic, autoimmune, and hematological diseases as well as tumors.

Western Indian Rural Gut Microbial Diversity in Extreme Prakriti Endo-Phenotypes Reveals Signature Microbes

Heterogeneity amidst healthy individuals at genomic level is being widely acknowledged. This, in turn, is modulated by differential response to environmental cues and treatment regimens, necessitating the need for stratified/personalized therapy. We intend to understand the molecular determinants of Ayurvedic way (ancient Indian system of medicine) of endo-phenotyping individuals into distinct constitution types termed “Prakriti,” which forms the basis of personalized treatment. In this study, we explored and analyzed the healthy human gut microbiome structure within three predominant Prakriti groups from a genetically homogenous cohort to discover differentially abundant taxa, using 16S rRNA gene based microbial community profiling. We found Bacteroidetes and Firmicutes as major gut microbial components in varying composition, albeit with similar trend across Prakriti. Multiple species of the core microbiome showed differential abundance within Prakriti types, with gender specific signature taxons. Our study reveals that despite overall uniform composition of gut microbial community, healthy individuals belonging to different Prakriti groups have enrichment of specific bacteria. It highlights the importance of Prakriti based endo-phenotypes to explain the variability amongst healthy individuals in gut microbial flora that have important consequences for an individual's health, disease and treatment.

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.

[Micro-inflammation and digestive bacterial translocation in chronic kidney disease]

Micro-inflammation has been recognized as a major factor associated with the poor prognosis of patients with chronic kidney disease. Those patients have an increased rate of pro-inflammatory markers like interleukin 6, C-Reactive protein, Tumor Necrosis Factor α and fibrinogen. Among multiple and complex causes of micro-inflammation the gut microbiota could be an important actor considering the dysbiosis in chronic kidney disease which would enhance the synthesis of uremic toxins with cardiovascular toxicity and the bacterial translocation. This review details the role of the gut microbiota in human pathology and in chronic kidney disease focusing on the bacterial translocation that could occur because of an impaired digestive permeability. This bacterial translocation could induce a chronic immune response and could take part in the raise of pro-inflammatory markers in chronic kidney disease. New therapeutic strategies aiming at preventing metabolic and cardiovascular complications could emerge from the understanding of the relationships between gut microbiota and host in this particular pathology.

Structural and functional differences in gut microbiome composition in patients undergoing haemodialysis or peritoneal dialysis

Complications of end-stage renal disease (ESRD) are critically related to inflammation. The gut microbiome is a key driver of inflammation. Since dialysis modalities may differently influence the gut microbiome, we aimed to compare the effects of haemodialysis (HD) and peritoneal dialysis (PD) on patients' gut microbiome composition and function. We therefore studied faecal microbiome composition and function as well as inflammation and gut permeability in 30 patients with ESRD (15 HD, 15 PD) and compared to 21 healthy controls. We found an increase in potentially pathogenic species and a decrease in beneficial species in patients on HD and to a lesser extend in patients on PD when compared to controls. These changes in taxonomic composition also resulted in differences in predicted metagenome functions of the faecal microbiome. In HD but not in PD, changes in microbiome composition were associated with an increase in c-reactive protein (CRP) but not with intestinal inflammation or gut permeability. In conclusion microbiome composition in ESRD differs from healthy controls but also between modes of dialysis. These differences are associated with systemic inflammation and cannot completely be explained by dialysis vintage. The mode of renal replacement therapy seems to be an important driver of dysbiosis in ESRD.

Short-chain fatty acids: a link between prebiotics and microbiota in chronic kidney disease

Under physiologic conditions, the human gut microbiota performs several activities essential to the body health. In contrast, their imbalances exacerbate some actions which can promote a cascade of metabolic abnormalities, and vice versa. Numerous diseases, including chronic kidney disease, are associated with gut microbiota imbalance, and among several strategies to re-establish gut symbiosis, prebiotics seem to represent an effective nonpharmacological approach. Prebiotics fermentation by gut microbiota produce short-chain fatty acids, which improve the gut barrier integrity and function, and modulate the glucose and lipid metabolism as well as the inflammatory response and immune system. Therefore, this literature review intends to discuss the beneficial effects of prebiotics in human health through short-chain fatty acids production, with a particular interest on chronic kidney disease.

Red meat intake in chronic kidney disease patients: Two sides of the coin

Red meat is an important dietary source of high biological value protein and micronutrients such as vitamins, iron, and zinc that exert many beneficial functions. However, high consumption of animal protein sources, especially red meat, results in an increased intake of saturated fat, cholesterol, iron, and salt, as well as an excessive acid load. Red meat intake may lead to an elevated production of uremic toxins by the gut microbiota, such as trimethylamine n-oxide (TMAO), indoxyl sulfate, and p-cresyl sulfate. These uremic toxins are associated with increased risk for cardiovascular (CV) mortality. Limiting the intake of red meat in patients with chronic kidney disease (CKD) thus may be a good strategy to reduce CV risk, and may slow the progression of kidney disease. In the present review, we discuss the role of red meat in the diet of patients with CKD. Additionally, we report on a pilot study that focused on the effect of a low-protein diet on TMAO plasma levels in nondialysis CKD patients.

Probiotic Supplementation in Chronic Kidney Disease: A Double-blind, Randomized, Placebo-controlled Trial

OBJECTIVE

The objective of the study was to evaluate the effects of probiotic supplementation on the gut microbiota profile and inflammatory markers in chronic kidney disease patients undergoing maintenance hemodialysis (HD).

DESIGN AND METHODS

This was a randomized, double-blind, placebo-controlled study. Forty-six HD patients were assigned to receive 1 of 2 treatments: probiotic (n = 23; Streptococcus thermophilus, Lactobacillus acidophilus e Bifidobacterialongum, 90 billion colony-forming units per day) or placebo (n = 23) daily for 3 months. Blood and feces were collected at baseline and after intervention. The inflammatory markers (C-reactive protein and interleukin-6) were analyzed by immunoenzymatic assay (enzyme-linked immunosorbent assay). Uremic toxins plasma levels (indoxyl sulfate, p-cresyl sulfate, and indole-3-acetic acid) were obtained by Reversed-Phase High-Performance Liquid Chromatography. Routine laboratory parameters were measured by standard techniques. Fecal pH was measured by the colorimetric method, and the gut microbiota profile was assessed by Denaturing Gradient Gel Electrophoresis analysis.

RESULTS

Sixteen patients remained in the probiotic group (11 men, 53.6 ± 11.0 year old, 25.3 ± 4.6 kg/m²) and 17 in the placebo group (10 men, 50.3 ± 8.5 year old, 25.2 ± 5.7 kg/m²). After probiotic supplementation there was a significant increase in serum urea (from 149.6 ± 34.2 mg/dL to 172.6 ± 45.0 mg/dL, P = .02), potassium (from 4.4 ± 0.4 mmol/L to 4.8 ± 0.4 mmol/L, P = .02), and indoxyl sulfate (from 31.2 ± 15.9 to 36.5 ± 15.0 mg/dL, P = .02). The fecal pH was reduced from 7.2 ± 0.8 to 6.5 ± 0.5 (P = .01). These parameters did not change significantly in placebo group. Changes in the percentage delta (Δ) between groups were exhibited with no statistical differences observed. The inflammatory markers and gut profile were not altered by supplementation.

CONCLUSIONS

Aprobiotic supplementation failed to reduce uremic toxins and inflammatory markers. Therefore, probiotic therapy should be chosen with caution in HD patients. Further studies addressing probiotic therapy in chronic kidney disease patients are needed.

The molecular mechanisms of hemodialysis vascular access failure

The arteriovenous fistula has been used for more than 50 years to provide vascular access for patients undergoing hemodialysis. More than 1.5 million patients worldwide have end stage renal disease and this population will continue to grow. The arteriovenous fistula is the preferred vascular access for patients, but its patency rate at 1 year is only 60%. The majority of arteriovenous fistulas fail because of intimal hyperplasia. In recent years, there have been many studies investigating the molecular mechanisms responsible for intimal hyperplasia and subsequent thrombosis. These studies have identified common pathways including inflammation, uremia, hypoxia, sheer stress, and increased thrombogenicity. These cellular mechanisms lead to increased proliferation, migration, and eventually stenosis. These pathways work synergistically through shared molecular messengers. In this review, we will examine the literature concerning the molecular basis of hemodialysis vascular access malfunction.

Could physical exercise help modulate the gut microbiota in chronic kidney disease?

Chronic kidney disease (CKD) patients have several metabolic disorders caused by chronic oxidative stress and inflammation. The imbalance of gut microbiota has been identified as a factor that may contribute to the development of these disorders, which can promote cardiovascular disease in CKD patients. Among several strategies to modulate gut microbiota, physical exercise could represent a new nonpharmacological approach. Although exercise can reduce cardiovascular risk in CKD patients through its beneficial effects on oxidative stress and inflammation, there are no available data regarding the relationship between exercise and modulation of gut microbiota in CKD patients. This review is intended to provide a brief overview of the hypothesis regarding gut microbiota modulation through physical exercise, with a particular emphasis on CKD.

Resistant starch for modulation of gut microbiota: Promising adjuvant therapy for chronic kidney disease patients?

The gut microbiota has been extensively studied in all health science fields because its imbalance is linked to many disorders, such as inflammation and oxidative stress, thereby contributing to cardiovascular disease, obesity, diabetes and chronic kidney disease (CKD) complications. Novel therapeutic strategies that aim to reduce the complications caused by this imbalance have increased in recent years. Studies have shown that prebiotic supplementation can beneficially modulate the gut microbiota in CKD patients. Prebiotics consist of non-digestible dietary soluble fiber, which acts as a substrate for the gut microbiota. Resistant starch (RS) is a type of dietary fiber that can reach the large bowel and act as a substrate for microbial fermentation; for these reasons, it has been considered to be a prebiotic. Few studies have analyzed the effects of RS on the gut microbiota in CKD patients. This review discusses recent information about RS and the potential role of the gut microbiota, with a particular emphasis on CKD patients.

The Role of the Gut Microbiome on Chronic Kidney Disease

Chronic kidney disease (CKD) is estimated to affect nearly 500 million people worldwide and cardiovascular (CV) disease is a major cause of death in this population. However, therapeutic interventions targeting traditional CV risks are not effective at lowering the incidence of CV events or at delaying the progression of the disease in CKD patients. In recent years, disturbances of normal gut microbiome were recognized in the pathogenesis of diverse chronic diseases. Gut dysbiosis is being unraveled in CKD and pointed as a nontraditional risk factor for CV risk and CKD progression. The most often reported changes in gut microbiome in CKD are related to the lower levels of Bifidobacteriaceae and Lactobacillaceae and to higher levels of Enterobacteriaceae. Although metagenomics brought us an amplified vision on the microbial world that inhabits the human host, it still lacks the sensitivity to characterize the microbiome up to species level, not revealing alterations that occur within specific genus. Here, we review the current state-of-the-art concerning gut dysbiosis in CKD and its role in pathophysiological mechanisms in CKD, particularly in relation with CV risk. Also, the strategies towards prevention and treatment of gut dysbiosis in CKD progression will be discussed.

The gut microbiome, diet, and links to cardiometabolic and chronic disorders

Cardiometabolic diseases (CMDs) have been associated with changes in the composition of the gut microbiota, with links between the host environment and microbiota identified in preclinical models. High-throughput sequencing technology has facilitated in-depth studies of the gut microbiota, bacterial-derived metabolites, and their association with CMDs. Such strategies have shown that patients with CMDs frequently exhibit enrichment or depletion of certain bacterial groups in their resident microbiota compared to healthy individuals. Furthermore, the ability to transfer resident gut microbiota from mice or humans into germ-free mouse models, or between human patients, has enabled researchers to characterize the causative role of the gut microbiota in CMDs. These approaches have helped identify that dietary intake of choline, which is metabolized by the gut microbiota, is associated with cardiovascular outcomes in mice and humans. Trimethylamine N-oxide (TMAO) - a metabolite derived from the gut microbiota - is also associated with poor cardiovascular outcomes in patients with cardiovascular disease and is elevated in patients with chronic kidney disease (CKD). TMAO might represent a biomarker that links the environment and microbiota with CKD. This Review summarizes data suggesting a link between the gut microbiota and derived metabolites with food intake patterns, metabolic alterations, and chronic CMDs.

Gut microbiota and inflammation in chronic kidney disease patients

Inflammation is a multifactorial phenotype that in chronic kidney disease is associated with adverse patient outcomes. Recently, alterations in gut microbiota composition and intestinal barrier have been associated with inflammation and oxidative stress in CKD patients. Vanholder and Glorieux recently critically reviewed [Clin Kidney J (2015) 8 (2): 168-179] the current understanding of the role of gut microbiota in the production of uraemic toxins and the therapeutic implications. Where do we stand now? The basic mechanisms of the gut-kidney crosstalk must still be clarified. In addition, the efficacy and safety of therapeutic strategies to modulate the gut microbiota in order to decrease uraemic toxin production and inflammation in chronic kidney disease should be evaluated. Finally, an impact of such strategies on hard outcomes should be demonstrated before incorporation into routine clinical practice.