Gut microbiota and chronic kidney disease: evidences and mechanisms that mediate a new communication in the gastrointestinal-renal axis

Canagliflozin attenuates kidney injury, gut-derived toxins, and gut microbiota imbalance in high-salt diet-fed Dahl salt-sensitive rats

PURPOSE

To investigate the effects of canagliflozin (20 mg/kg) on Dahl salt-sensitive (DSS) rat gut microbiota and salt-sensitive hypertension-induced kidney injury and further explore its possible mechanism.

METHODS

Rats were fed a high-salt diet to induce hypertension and kidney injury, and physical and physiological indicators were measured afterwards. This study employed 16S rRNA sequencing technology and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based metabolic profiling combined with advanced differential and association analyses to investigate the correlation between the microbiome and the metabolome in male DSS rats.

RESULTS

A high-salt diet disrupted the balance of the intestinal flora and increased toxic metabolites (methyhistidines, creatinine, homocitrulline, and indoxyl sulfate), resulting in severe kidney damage. Canagliflozin contributed to reconstructing the intestinal flora of DSS rats by significantly increasing the abundance of Corynebacterium spp., Bifidobacterium spp., Facklamia spp., Lactobacillus spp., Ruminococcus spp., Blautia spp., Coprococcus spp., and Allobaculum spp. Moreover, the reconstruction of the intestinal microbiota led to significant changes in host amino acid metabolite concentrations. The concentration of uremic toxins, such as methyhistidines, creatinine, and homocitrulline, in the serum of rats was decreased by canagliflozin, which resulted in oxidative stress and renal injury alleviation.

CONCLUSION

Canagliflozin may change the production of metabolites and reduce the level of uremic toxins in the blood circulation by reconstructing the intestinal flora of DSS rats fed a high-salt diet, ultimately alleviating oxidative stress and renal injury.

Gut microbiota dynamics and association with chronic kidney disease: A longitudinal study within the PREDIMED-Plus trial

AIMS

Chronic kidney disease (CKD) represents a global health concern, disproportionately affecting the elderly with heightened cardiovascular risk. The emerging focus on the gut microbiota's role in CKD pathophysiology represents a pivotal area in nephrology; however, the evidence on this topic is limited. This observational prospective study, in the framework of the PREDIMED-Plus trial, investigates associations between gut microbiota composition and the 1-year trajectory of CKD in 343 participants aged 55-75 years with high cardiovascular risk.

MATERIALS AND METHODS

Kidney function was assessed at baseline and at 1-year of follow-up through the estimated glomerular filtration rate based on cystatin C (eGFR-CysC) and CKD defined by eGFR-CysC <60 mL/min/1.73 m2. Participants were grouped based on their 1-year CKD trajectory: Group 1 maintained normal status or improved from CKD to normal, while Group 2 maintained CKD or worsened from normal to CKD. Fecal microbiota composition was assessed through 16S sequencing.

KEY FINDINGS

We observed differences in gut microbiota composition between CKD trajectory groups. Notably, the baseline relative abundance of Lachnoclostridium and Lachnospira, both butyrate-producing genera, was lower in participants maintaining or progressing to CKD. Longitudinally, a decrease in Lachnospira abundance was associated with CKD progression. The improved Chao1 index after 1-year follow-up suggests a link between enhanced microbial richness and stable/better kidney function.

SIGNIFICANCE

The findings underscore the potential of gut microbiota analysis in non-invasively monitoring CKD, especially in older populations, and hint at future interventions targeting gut microbiota to manage CKD progression. Further research is needed for causal relationships and generalizability.

Identification of renal protective gut microbiome derived-metabolites in diabetic chronic kidney disease: An integrated approach using network pharmacology and molecular docking

Metabolites from the gut microbiota define molecules in the gut-kidney cross talks. However, the mechanistic pathway by which the kidneys actively sense gut metabolites and their impact on diabetic chronic kidney disease (DCKD) remains unclear. This study is an attempt to investigate the gut microbiome metabolites, their host targeting genes, and their mechanistic action against DCKD. Gut microbiome, metabolites, and host targets were extracted from the gutMgene database and metabolites from the PubChem database. DCKD targets were identified from DisGeNET, GeneCard, NCBI, and OMIM databases. Computational examination such as protein-protein interaction networks, enrichment pathway, identification of metabolites for potential targets using molecular docking, hubgene-microbes-metabolite-samplesource-substrate (HMMSS) network architecture were executed using Network analyst, ShinyGo, GeneMania, Cytoscape, Autodock tools. There were 574 microbial metabolites, 2861 DCKD targets, and 222 microbes targeting host genes. After screening, we obtained 27 final targets, which are used for computational examination. From enrichment analysis, we found NF-ΚB1, AKT1, EGFR, JUN, and RELA as the main regulators in the DCKD development through mitogen activated protein kinase (MAPK) pathway signalling. The (HMMSS) network analysis found F.prausnitzi, B.adolescentis, and B.distasonis probiotic bacteria that are found in the intestinal epithelium, colonic region, metabolize the substrates like tryptophan, other unknown substrates might have direct interaction with the NF-kB1 and epidermal growth factor receptor (EGFR) targets. On docking of these target proteins with 3- Indole propionic acid (IPA) showed high binding energy affinity of -5.9 kcal/mol and -7.4kcal/mol. From this study we identified, the 3 IPA produced by F. prausnitzi A2-165 was found to have renal sensing properties inhibiting MAPK/NF-KB1 inflammatory pathway and would be useful in treating CKD in diabetics.

Bifidobacterium bifidum alleviates adenine-induced acute kidney injury in mice by improving intestinal barrier function

Acute kidney injury (AKI) is a kind of critical kidney disease characterized by tubular injury, rapid decline of renal function and renal inflammation, with high clinical incidence. AKI has been shown to be associated with dysregulation of the gut microbiota and impaired intestinal barrier. Bifidobacterium has a positive impact on the treatment of many diseases. However, little is known about the role and mechanism of Bifidobacterium in AKI. Based on previous experiments, Bifidobacterium bifidum FL228.1 and FL276.1, which can relieve intestinal inflammation, and Bifidobacterium bifidum ZL.1, which has anti-inflammatory potential, were screened. This study aimed to investigate the effects of Bifidobacterium bifidum FL228.1, FL276.1 and ZL.1 on AKI, focusing on their role in the gut microbiota composition and intestinal barrier function. Our results showed that Bifidobacterium bifidum FL228.1, FL276.1 and ZL.1 effectively improved kidney function in mice with AKI by regulating the gut microbiota dysregulation, inhibiting intestinal inflammation and rebuilding the intestinal mucosal barrier. In addition, intervention with probiotics turned the gut microbiota disturbance caused by AKI into a normalized trend, reversed the adverse outcome of microbiota imbalance, and increased the abundance of potentially beneficial bacteria Bifidobacterium and Faecalibaculum. In summary, Bifidobacterium bifidum FL228.1, FL276.1, and ZL.1 alleviate adenine-induced AKI based on the gut-kidney axis. Although their mechanisms of action are different, their effect on alleviating AKI is almost the same.

Gut microbiota dysbiosis in hyperuricaemia promotes renal injury through the activation of NLRP3 inflammasome

BACKGROUND

The prevalence of hyperuricaemia (HUA), a metabolic disorder characterized by elevated levels of uric acid, is on the rise and is frequently associated with renal injury. Gut microbiota and gut-derived uremic toxins are critical mediators in the gut-kidney axis that can cause damage to kidney function. Gut dysbiosis has been implicated in various kidney diseases. However, the role and underlying mechanism of the gut microbiota in HUA-induced renal injury remain unknown.

RESULTS

A HUA rat model was first established by knocking out the uricase (UOX). HUA rats exhibited apparent renal dysfunction, renal tubular injury, fibrosis, NLRP3 inflammasome activation, and impaired intestinal barrier functions. Analysis of 16S rRNA sequencing and functional prediction data revealed an abnormal gut microbiota profile and activation of pathways associated with uremic toxin production. A metabolomic analysis showed evident accumulation of gut-derived uremic toxins in the kidneys of HUA rats. Furthermore, faecal microbiota transplantation (FMT) was performed to confirm the effects of HUA-induced gut dysbiosis on renal injury. Mice recolonized with HUA microbiota exhibited severe renal injury and impaired intestinal barrier functions following renal ischemia/reperfusion (I/R) surgery. Notably, in NLRP3-knockout (NLRP3-/-) I/R mice, the deleterious effects of the HUA microbiota on renal injury and the intestinal barrier were eliminated.

CONCLUSION

Our results demonstrate that HUA-induced gut dysbiosis contributes to the development of renal injury, possibly by promoting the production of gut-derived uremic toxins and subsequently activating the NLRP3 inflammasome. Our data suggest a potential therapeutic strategy for the treatment of renal diseases by targeting the gut microbiota and the NLRP3 inflammasome. Video Abstract.

Gut microbiota mediates the protective effects of β-hydroxybutyrate against cisplatin-induced acute kidney injury

The gut microbiota has been reported to be perturbed by chemotherapeutic agents and to modulate side effects. However, the critical role of β-hydroxybutyrate (BHB) in the regulation of the gut microbiota and the pathogenesis of chemotherapeutic agents related nephrotoxicity remains unknown. We conducted a comparative analysis of the composition and function of gut microbiota in healthy, cisplatin-challenged, BHB-treated, and high-fat diet-treated mice using 16 S rDNA gene sequencing. To understand the crucial involvement of intestinal flora in BHB's regulation of cisplatin -induced nephrotoxicity, we administered antibiotics to deplete the gut microbiota and performed fecal microbiota transplantation (FMT) before cisplatin administration. 16 S rDNA gene sequencing analysis demonstrated that both endogenous and exogenous BHB restored gut microbiota dysbiosis and cisplatin-induced intestinal barrier disruption in mice. Additionally, our findings suggested that the LPS/TLR4/NF-κB pathway was responsible for triggering renal inflammation in the gut-kidney axis. Furthermore, the ablation of the gut microbiota ablation using antibiotics eliminated the renoprotective effects of BHB against cisplatin-induced acute kidney injury. FMT also confirmed that administration of BHB-treated gut microbiota provided protection against cisplatin-induced nephrotoxicity. This study elucidated the mechanism by which BHB affects the gut microbiota mediation of cisplatin-induced nephrotoxicity by inhibiting the inflammatory response, which may help develop novel therapeutic approaches that target the composition of the microbiota.

Cardiometabolic comorbidities and complications of obesity and chronic kidney disease (CKD)

Obesity and chronic kidney disease are two ongoing progressive clinical pandemics of major public health and clinical care significance. Because of their growing prevalence, chronic indolent course and consequent complications both these conditions place significant burden on the health care delivery system especially in developed countries like the United States. Beyond the chance coexistence of both of these conditions in the same patient based on high prevalence it is now apparent that obesity is associated with and likely has a direct causal role in the onset, progression and severity of chronic kidney disease. The causes and underlying pathophysiology of this are myriad, complicated and multi-faceted. In this review, continuing the theme of this special edition of the journal on " The Cross roads between Endocrinology and Nephrology" we review the epidemiology of obesity related chronic kidney disease (ORCKD), and its various underlying causes and pathophysiology. In addition, we delve into the consequent comorbidities and complications associated with ORCKD with particular emphasis on the cardio metabolic consequences and then review the current body of evidence for available strategies for chronic kidney disease modulation in ORCKD as well as the potential unique role of weight reduction and management strategies in its improvement and risk reduction.

Revitalizing the Gut Microbiome in Chronic Kidney Disease: A Comprehensive Exploration of the Therapeutic Potential of Physical Activity

Both physical inactivity and disruptions in the gut microbiome appear to be prevalent in patients with chronic kidney disease (CKD). Engaging in physical activity could present a novel nonpharmacological strategy for enhancing the gut microbiome and mitigating the adverse effects associated with microbial dysbiosis in individuals with CKD. This narrative review explores the underlying mechanisms through which physical activity may favorably modulate microbial health, either through direct impact on the gut or through interorgan crosstalk. Also, the development of microbial dysbiosis and its interplay with physical inactivity in patients with CKD are discussed. Mechanisms and interventions through which physical activity may restore gut homeostasis in individuals with CKD are explored.

Small Intestinal Bacterial Overgrowth (SIBO) and Twelve Groups of Related Diseases-Current State of Knowledge

The human gut microbiota creates a complex microbial ecosystem, characterized by its high population density, wide diversity, and complex interactions. Any imbalance of the intestinal microbiome, whether qualitative or quantitative, may have serious consequences for human health, including small intestinal bacterial overgrowth (SIBO). SIBO is defined as an increase in the number of bacteria (103-105 CFU/mL), an alteration in the bacterial composition, or both in the small intestine. The PubMed, Science Direct, Web of Science, EMBASE, and Medline databases were searched for studies on SIBO and related diseases. These diseases were divided into 12 groups: (1) gastrointestinal disorders; (2) autoimmune disease; (3) cardiovascular system disease; (4) metabolic disease; (5) endocrine disorders; (6) nephrological disorders; (7) dermatological diseases; (8) neurological diseases (9); developmental disorders; (10) mental disorders; (11) genetic diseases; and (12) gastrointestinal cancer. The purpose of this comprehensive review is to present the current state of knowledge on the relationships between SIBO and these 12 disease groups, taking into account risk factors and the causal context. This review fills the evidence gap on SIBO and presents a biological-medical approach to the problem, clearly showing the groups and diseases having a proven relationship with SIBO, as well as indicating groups within which research should continue to be expanded.

Exercise in Diabetic Nephropathy: Protective Effects and Molecular Mechanism

Diabetic nephropathy (DN) is a serious complication of diabetes, and its progression is influenced by factors like oxidative stress, inflammation, cell death, and fibrosis. Compared to drug treatment, exercise offers a cost-effective and low-risk approach to slowing down DN progression. Through multiple ways and mechanisms, exercise helps to control blood sugar and blood pressure and reduce serum creatinine and albuminuria, thereby alleviating kidney damage. This review explores the beneficial effects of exercise on DN improvement and highlights its potential mechanisms for ameliorating DN. In-depth understanding of the role and mechanism of exercise in improving DN would pave the way for formulating safe and effective exercise programs for the treatment and prevention of DN.

Adenine's impact on mice's gut and kidney varies with the dosage administered and relates to intestinal microorganisms and enzyme activities

This study aimed to investigate the effects of different dosages of adenine on intestinal microorganisms and enzyme activities, laying the experimental groundwork for subsequent exploration of the microbial mechanisms underlying diarrhea with kidney yang deficiency syndrome. Twenty-four mice were assigned to the following four groups: the control (NC) group, low-dosage adenine (NML) group, middle-dosage adenine (NMM) group, and high-dosage adenine (NMH) group. Mice in the NML, NMM, and NMH groups received 25 mg/(kg·d), 50 mg/(kg·d), and 100 mg/(kg·d) of adenine, respectively, 0.4 mL/each, once a day for 14 days. The NC group received 0.4 mL sterile water. Parameters including body weight, rectal temperature, intestinal microorganisms, enzyme activities, and microbial activity were measured. Results indicated that mice in the experimental group displayed signs of a poor mental state, curled up with their backs arched, and felt sleepy and lazy, with sparse fur that was easily shed, and damp bedding. Some mice showed fecal adhesion contamination in the perianal and tail areas. Dosage-dependent effects were observed, with decreased food intake, body weight, rectal temperature, and microbial activity and increased water intake and fecal water content. Enzyme activity analyses revealed significantly higher activities of protease, sucrase, amylase, and cellulase in intestinal contents and lactase, sucrase, amylase, and cellulase in the mucosa of the NMM group compared to those of other groups. Ultimately, the higher adenine dosage was associated with more pronounced symptoms of kidney yang deficiency syndrome, with 50 mg/kg adenine exhibiting the most substantial impact on the number of intestinal microbial colonies and enzyme activities.

Astragaloside IV Mitigated Diabetic Nephropathy by Restructuring Intestinal Microflora and Ferroptosis

SCOPE

To investigate the underlying mechanism of Astragaloside IV (AS-IV) in ameliorating diabetic nephropathy (DN) by regulating intestinal microbiota ecology and intestinal mucosal barrier.

METHODS AND RESULTS

Genetically db/db mice are used to establish DN mouse model to monitor the therapeutic effects of AS-IV and fecal microbiota transplantation (FMT) against DN. Supplementation with AS-IV dramatically attenuates several clinical indicators of DN in db/db mice. In addition, AS-IV markedly improves intestinal barrier function, modifies intestinal permeability, and reduces inflammation. Moreover, AS-IV treatment remarkably improves intestinal dysbiosis in db/db mice, characterized by an elevated abundance of Akkermansia, Ligilactobacillus, and Lactobacillus, indicating the fundamental role of the microbiome in DN progression. Furthermore, FMT derived from AS-IV-treated db/db mice is potentially efficient in antagonizing renal dysfunction, rebalancing gut microbiota, and improving intestinal permeability in recipient db/db mice. AS-IV-enriched Akkermansia muciniphila dramatically alleviates DN and intestinal mucosal barrier dysfunction in db/db mice. Intriguingly, AS-IV intervention dramatically diminishes ferroptosis in the kidney and colon tissues. CONCLUSION : Intestinal microbiome alterations and ferroptosis modulation by AS-IV may play instrumental roles in this mechanism, providing compelling evidence for the role of the gut-renal axis in DN.

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

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

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.

Huang Gan Formula Alleviates Systemic Inflammation and Uremia in Adenine-Induced Chronic Kidney Disease Rats May Associate with Modification of Gut Microbiota and Colonic Microenvironment

Purpose

This study aims to investigate the effects of Huang Gan formula (HGF), a Chinese herbal prescription used for chronic kidney disease (CKD), on the regulation of the gut microbiota and colonic microenvironment of CKD.

Methods

CKD rats were induced by 150 mg/kg adenine gavage for 4 weeks, then orally treated with or without 3.6 g/kg or 7.2 g/kg of HGF for 8 weeks. The renal function and structure were analyzed by biochemical detection, hematoxylin and eosin, Masson's trichrome, Sirius red and immunochemical staining. Average fecal weight and number in the colon were recorded to assess colonic motility. Further, the changes in the gut microbiota and colonic microenvironment were evaluated by 16S rRNA sequencing, RT-PCR or immunofluorescence. The levels of inflammatory cytokines, uremic toxins, and NF-κB signaling pathway were detected by RT-PCR, ELISA, chloramine-T method or Western blotting. Redundancy analysis biplot and Spearman's rank correlation coefficient were used for correlation analysis.

Results

HGF significantly improved renal function and pathological injuries of CKD. HGF could improve gut microbial dysbiosis, protect colonic barrier and promote motility of colonic lumens. Further, HGF inhibited systemic inflammation through a reduction of TNF-α, IL-6, IL-1β, TGF-β1, and a suppression of NF-κB signaling pathway. The serum levels of the selected uremic toxins were also reduced by HGF treatment. Spearman correlation analysis suggested that high-dose HGF inhibited the overgrowth of bacteria that were positively correlated with inflammatory factors (eg, TNF-α) and uremic toxins (eg, indoxyl sulfate), whereas it promoted the proliferation of bacteria belonging to beneficial microbial groups and was positively correlated with the level of IL-10.

Conclusion

Our results suggest that HGF can improve adenine-induced CKD via suppressing systemic inflammation and uremia, which may associate with the regulations of the gut microbiota and colonic microenvironment.

Gut Microbiota's Oxalate-Degrading Activity and Its Implications on Cardiovascular Health in Patients with Kidney Failure: A Pilot Prospective Study

Background and Objectives: The present study aims to investigate the association between gut microbiota's oxalate-degrading activity (ODA) and the risk of developing cardiovascular disease (CVD) over a three-year follow-up period in a cohort of patients undergoing kidney replacement therapy (KRT). Additionally, various factors were examined to gain insight into the potential mechanisms underlying the ODA-CVD link. Materials and Methods: A cohort of 32 KRT patients and 18 healthy volunteers was enrolled in this prospective observational pilot study. Total fecal ODA, routine clinical data, plasma oxalic acid (POx), serum indoxyl sulfate, lipid profile, oxidative stress, and proinflammatory markers were measured, and the patients were followed up for three years to assess CVD events. Results: The results revealed that patients with kidney failure exhibited significantly lower total fecal ODA levels compared to the healthy control group (p = 0.017), with a higher proportion showing negative ODA status (≤-1% per 0.01 g) (p = 0.01). Negative total fecal ODA status was associated with a significantly higher risk of CVD events during the three-year follow-up period (HR = 4.1, 95% CI 1.4-16.3, p = 0.003), even after adjusting for potential confounders. Negative total fecal ODA status was significantly associated with elevated POx and indoxyl sulfate levels and linked to dyslipidemia, increased oxidative stress, and inflammation, which are critical contributors to CVD. Conclusions: The findings contribute novel insights into the relationship between gut microbiota's ODA and cardiovascular health in patients undergoing KRT, emphasizing the need for further research to elucidate underlying mechanisms and explore potential therapeutic implications of targeting gut microbiota's ODA in this vulnerable population.

Short-term use of ceftriaxone sodium leads to intestinal barrier disruption and ultrastructural changes of kidney in SD rats

OBJECTIVE

Antibiotic treatments are known to disturb gut microbiota, but their effects on the mucosal barrier and extraintestinal diseases are rarely discussed. The aim of this study was to evaluate and visualize the impact of antibiotics on colonic mucus and the microbial community, and to assess whether intestinal dysbacteriosis is involved in the pathogenesis and progression of extraintestinal diseases in vivo.

MATERIALS AND METHODS

Twenty-one SD rats were randomly assigned into three groups followed by different experimental treatments. The albumin-creatinine ratio, urinary protein and occult blood semi-quantified test were tested. Fecal samples were collected at different time points (0,4, and 12 weeks) for 16S rRNA gene sequencing. Colon and kidney specimens were examined using light microscopy and transmission electron microscopy (TEM) to identify morphological changes.

RESULTS

Ceftriaxone intervention for one week did not cause any symptoms of diarrhea or weight loss, but the alpha and beta diversities of gut microbiota decreased quickly and significantly, a lower Firmicutes/Bacteroidetes (F/B) ratio was observed. At week 12, although the alpha and beta diversities increased to a level similar to that of the control (CON) group, LEfSe analysis indicated that the microbial community composition still differed significantly in each group. In addition, KEGG metabolic prediction revealed different metabolic functions in each group. TEM examination of colon revealed that dramatic morphological changes were observed in the ceftriaxone (Cef) group, wherein microvilli were misaligned and shortened significantly and morphologically intact bacteria were seen on the epithelial cell surface. TEM examination of kidneys from the Cef group showed characteristic glomerular changes in the form of widely irregularly thickened glomerular basement membrane (GBM) and foot process fusion or effacement; mild thickening of the GBM and foot process fusion was detected when ceftriaxone and Resatorvid (TAK242, an inhibitor of TLR4 signaling) are used together in the ceftriaxone + TAK242 (TAK) group.

CONCLUSIONS

Short-term use of ceftriaxone induced dynamic changes of gut microbiota and lead to intestinal barrier disruption and ultrastructural changes of kidneys in the SD rats. Moreover, interference with the TLR4-dependent signaling pathway can alleviate the damage to the intestinal barrier and kidney.

Gut-Kidney-Heart: A Novel Trilogy

The microbiota represents a key factor in determining health and disease. Its role in inflammation and immunological disorders is well known, but it is also involved in several complex conditions, ranging from neurological to psychiatric, from gastrointestinal to cardiovascular diseases. It has recently been hypothesized that the gut microbiota may act as an intermediary in the close interaction between kidneys and the cardiovascular system, leading to the conceptualization of the "gut-kidney-heart" axis. In this narrative review, we will discuss the impact of the gut microbiota on each system while also reviewing the available data regarding the axis itself. We will also describe the role of gut metabolites in this complex interplay, as well as potential therapeutical perspectives.

The Gut-Organ Axis within the Human Body: Gut Dysbiosis and the Role of Prebiotics

The human gut microbiota (GM) is a complex microbial ecosystem that colonises the gastrointestinal tract (GIT) and is comprised of bacteria, viruses, fungi, and protozoa. The GM has a symbiotic relationship with its host that is fundamental for body homeostasis. The GM is not limited to the scope of the GIT, but there are bidirectional interactions between the GM and other organs, highlighting the concept of the "gut-organ axis". Any deviation from the normal composition of the GM, termed "microbial dysbiosis", is implicated in the pathogenesis of various diseases. Only a few studies have demonstrated a relationship between GM modifications and disease phenotypes, and it is still unknown whether an altered GM contributes to a disease or simply reflects its status. Restoration of the GM with probiotics and prebiotics has been postulated, but evidence for the effects of prebiotics is limited. Prebiotics are substrates that are "selectively utilized by host microorganisms, conferring a health benefit". This study highlights the bidirectional relationship between the gut and vital human organs and demonstrates the relationship between GM dysbiosis and the emergence of certain representative diseases. Finally, this article focuses on the potential of prebiotics as a target therapy to manipulate the GM and presents the gaps in the literature and research.

Pharmacomicrobiomics of Classical Immunosuppressant Drugs: A Systematic Review

The clinical response to classical immunosuppressant drugs (cIMDs) is highly variable among individuals. We performed a systematic review of published evidence supporting the hypothesis that gut microorganisms may contribute to this variability by affecting cIMD pharmacokinetics, efficacy or tolerability. The evidence that these drugs affect the composition of intestinal microbiota was also reviewed. The PubMed and Scopus databases were searched using specific keywords without limits of species (human or animal) or time from publication. One thousand and fifty five published papers were retrieved in the initial database search. After screening, 50 papers were selected to be reviewed. Potential effects on cIMD pharmacokinetics, efficacy or tolerability were observed in 17/20 papers evaluating this issue, in particular with tacrolimus, cyclosporine, mycophenolic acid and corticosteroids, whereas evidence was missing for everolimus and sirolimus. Only one of the papers investigating the effect of cIMDs on the gut microbiota reported negative results while all the others showed significant changes in the relative abundance of specific intestinal bacteria. However, no unique pattern of microbiota modification was observed across the different studies. In conclusion, the available evidence supports the hypothesis that intestinal microbiota could contribute to the variability in the response to some cIMDs, whereas data are still missing for others.

Probiotics mitigate kidney damage after exposure to Sri Lanka's local groundwater from chronic kidney disease with uncertain etiology (CKDu) prevalent area in zebrafish

Groundwater in Sri Lanka, contaminated with environmental toxins, is suspected to potentially induce chronic kidney disease of uncertain etiology (CKDu) in humans. This study aims to elucidate the potential mitigating effects of probiotics on kidney damage induced by exposure to this local groundwater (LW) in zebrafish. We used zebrafish as a model organism and exposed them to local groundwater to evaluate the risk of CKDu. Probiotics were then added at a concentration of 108 colony-forming units per milliliter (CFU/mL). Our findings revealed that exposure to local groundwater resulted in abnormalities, such as tail deletion and spinal curvature in zebrafish larvae. However, the addition of probiotics mitigated these effects, improving the hatching rate, heart rate, length, weight, deformity rate, survival rate, and abnormal behavior of zebrafish. It also positively influenced the differential expression levels of kidney development and immunity-related genes (dync2h1, foxj1, pkd2, gata3, slc20a1, il1β, and lyso). Furthermore, exposure to LW decreased both the diversity and abundance of microbiota in zebrafish larvae. However, treatment with probiotics, such as L. plantarum and L. rhamnosus partially restored the disrupted gut microbiota and significantly impacted the cellular process pathways of the microbial community, as determined by KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis. In conclusion, this study highlights the risks associated with Sri Lanka's local groundwater from a CKDu prevalent area and confirms the beneficial effects of different probiotics. These findings may provide new insights into bacterial function in host kidney health.

A pilot study of alterations of the gut microbiome in canine chronic kidney disease

Introduction

Gut dysbiosis has been noted in humans and animals with chronic kidney disease (CKD). However, little is known about the gut microbiome in canine patients with CKD. This study aimed to analyze and compare the gut microbiome profiles of healthy and CKD dogs, including differences in the gut microbiome between each CKD stage.

Methods

The study was conducted on 29 client-owned dogs who underwent physical examination, complete blood count (CBC), serum biochemistry, and urinalysis. The gut microbiome profile of healthy dogs (n = 10) and dogs with CKD (n = 19) was analyzed employing 16S rRNA sequencing.

Results

Significant differences were seen in the composition of the gut microbiome, with increased operational taxonomic units from the phylum Proteobacteria (p = 0.035), family Enterobacteriaceae (p < 0.001), and genus Enterococcus (p = 0.002) in dogs with CKD, and a decrease in the genus Ruminococcus (p = 0.007). Furthermore, an increase in both the progression of CKD and abundance of genus Klebsiella (Jonckheere-Terpstra test statistic value (JT) = 2.852, p = 0.004) and Clostridium (JT = 2.018, p = 0.044) was observed.

Discussion

Our study demonstrated that in dogs with CKD, the composition of the gut microbiome varied depending on the stage of CKD. Alterations in gut microbiome composition observed in CKD patients are characterized by an increase in proteolytic bacteria and a decrease in saccharolytic bacteria. These findings suggest specific gut microbiota could be targeted for clinical management of uremic dogs with CKD.

The role of probiotics in tissue engineering and regenerative medicine

Tissue engineering and regenerative medicine (TERM) as an emerging field is a multidisciplinary science and combines basic sciences such as biomaterials science, biology, genetics and medical sciences to achieve functional TERM-based products to regenerate or replace damaged or diseased tissues or organs. Probiotics are useful microorganisms which have multiple effective functions on human health. They have some immunomodulatory and biocompatibility effects and improve wound healing. In this article, we describe the latest findings on probiotics and their pro-healing properties on various body systems that are useable in regenerative medicine. Therefore, this review presents a new perspective on the therapeutic potential of probiotics for TERM.

The altered composition of gut microbiota and biochemical features as well as dietary patterns in a southern Chinese population with recurrent renal calcium oxalate stones

The correlation among gut microbiota, biochemical features, and dietary patterns in recurrent stone formers has been inadequately investigated in the Chinese population. Forty-two patients with calcium oxalate stones (CaOxS group), including 34 recurrent stone formers (RS group), and 40 nonstone healthy subjects (NS group) from Changshu Hospital Affiliated with Soochow University, were prospectively recruited. Food frequency questionnaires were completed by participants, fasting vein blood was extracted, 24-h urine was collected for biochemical detection, and fecal samples were gathered for 16S ribosomal RNA (rRNA) gene sequencing. BMI; serum levels of triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), magnesium, and creatinine; and urine levels of magnesium in stone formers were significantly different from those of controls, and RS patients showed significantly low serum phosphate and high urine phosphate levels. Celery, bamboo shoots, and pickled food were the favored foods of local stone formers. Patients with recurrent stones had altered microbiota composition, with Escherichia, Fusobacterium, and Epulopiscium being the predominant pathogenic genera. The gut microbiota in RS patients had stronger functions in fatty acid and amino acid degradation but weaker functions in their biosynthesis. The pathogenic genera were positively correlated with BMI; serum levels of TGs and creatinine; urine levels of calcium, phosphate, and uric acid (UA); and celery, bamboo shoots, and pickled food intake. The abundance of Escherichia and Fusobacterium and the levels of serum magnesium and creatinine were the most relevant factors associated with stone recurrence and could be validated as biomarkers of recurrence. Our research provides a novel prevention strategy for the recurrence of renal calcium oxalate stones in the Han Chinese population of southern China.

Maternal High-Fat Diet Controls Offspring Kidney Health and Disease

A balanced diet during gestation is critical for fetal development, and excessive intake of saturated fats during gestation and lactation is related to an increased risk of offspring kidney disease. Emerging evidence indicates that a maternal high-fat diet influences kidney health and disease of the offspring via so-called renal programming. This review summarizes preclinical research documenting the connection between a maternal high-fat diet during gestation and lactation and offspring kidney disease, as well as the molecular mechanisms behind renal programming, and early-life interventions to offset adverse programming processes. Animal models indicate that offspring kidney health can be improved via perinatal polyunsaturated fatty acid supplementation, gut microbiota changes, and modulation of nutrient-sensing signals. These findings reinforce the significance of a balanced maternal diet for the kidney health of offspring.

Regulation of gut microbiota: a novel pretreatment for complications in patients who have undergone kidney transplantation

Kidney transplantation is an effective method to improve the condition of patients with end-stage renal disease. The gut microbiota significantly affects the immune system and can be used as an influencing factor to change the prognoses of patients who have undergone kidney transplantation. Recipients after kidney transplantation showed a lower abundance of Firmicutes and Faecalibacterium prausnitzii and a higher proportion of Bacteroidetes and Proteobacteria. After using prebiotics, synbiotics, and fecal microbiota transplantation to regulate the microbial community, the prognoses of patients who underwent kidney transplantation evidently improved. We aimed to determine the relationship between gut microbiota and various postoperative complications inpatients who have undergone kidney transplantation in recent years and to explore how gut microecology affects post-transplant complications. An in-depth understanding of the specific functions of gut microbiota and identification of the actual pathogenic flora during complications in patients undergoing kidney transplantation can help physicians develop strategies to restore the normal intestinal microbiome of transplant patients to maximize their survival and improve their quality of life.

A novel model of adenine-induced chronic kidney disease-associated gastrointestinal dysfunction in mice: The gut-kidney axis

Although constipation is a common complication of chronic kidney disease (CKD), there is no animal model that can be used to study the association between renal impairment and gastrointestinal function without interfering with the gastrointestinal tract of the model. Therefore, we determined whether adenine could induce CKD in association with gastrointestinal dysfunction. Six-week-old ICR mice were intraperitoneally injected with saline, 25, 50, or 75 mg adenine/kg body weight for 21 days. Blood urea nitrogen (BUN), plasma creatinine, and renal histopathology were evaluated. Defecation status was evaluated from defecation frequency and fecal water content. Colonic smooth muscle contraction was measured by the organ bath technique, and transepithelial electrical resistance (TEER) was measured using an Ussing chamber. In the 50 mg/kg treatment group, BUN and creatinine were significantly increased compared with control, and inflammatory cell infiltration, glomerular necrosis, tubular dilatation, and interstitial fibrosis were observed in renal tissues. Mice in this group also showed a significant decrease in defecation frequency, fecal water content, colonic motility index, and TEER. Overall, 50 mg/kg of adenine was the best dose to induce CKD with associated constipation and intestinal barrier impairment. Therefore, this adenine administration model can be recommended for CKD-associated gastrointestinal dysfunction research.

Dementia, infections and vaccines: 30 years of controversy

This paper reports the proceedings of a virtual meeting convened by the European Interdisciplinary Council on Ageing (EICA), to discuss the involvement of infectious disorders in the pathogenesis of dementia and neurological disorders leading to dementia. We recap how our view of the infectious etiology of dementia has changed over the last 30 years in light of emerging evidence, and we present evidence in support of the implication of infection in dementia, notably Alzheimer's disease (AD). The bacteria and viruses thought to be responsible for neuroinflammation and neurological damage are reviewed. We then review the genetic basis for neuroinflammation and dementia, highlighting the genes that are currently the focus of investigation as potential targets for therapy. Next, we describe the antimicrobial hypothesis of dementia, notably the intriguing possibility that amyloid beta may itself possess antimicrobial properties. We further describe the clinical relevance of the gut-brain axis in dementia, the mechanisms by which infection can move from the intestine to the brain, and recent findings regarding dysbiosis patterns in patients with AD. We review the involvement of specific pathogens in neurological disorders, i.e. SARS-CoV-2, human immunodeficiency virus (HIV), herpes simplex virus type 1 (HSV1), and influenza. Finally, we look at the role of vaccination to prevent dementia. In conclusion, there is a large body of evidence supporting the involvement of various infectious pathogens in the pathogenesis of dementia, but large-scale studies with long-term follow-up are needed to elucidate the role that infection may play, especially before subclinical or clinical disease is present.

Intestinal Lymphatic Dysfunction in Kidney Disease

Kidney disease is associated with adverse consequences in many organs beyond the kidney, including the heart, lungs, brain, and intestines. The kidney-intestinal cross talk involves intestinal epithelial damage, dysbiosis, and generation of uremic toxins. Recent studies reveal that kidney injury expands the intestinal lymphatics, increases lymphatic flow, and alters the composition of mesenteric lymph. The intestinal lymphatics, like blood vessels, are a route for transporting potentially harmful substances generated by the intestines. The lymphatic architecture and actions are uniquely suited to take up and transport large macromolecules, functions that differentiate them from blood vessels, allowing them to play a distinct role in a variety of physiological and pathological processes. Here, we focus on the mechanisms by which kidney diseases result in deleterious changes in intestinal lymphatics and consider a novel paradigm of a vicious cycle of detrimental organ cross talk. This concept involves kidney injury-induced modulation of intestinal lymphatics that promotes production and distribution of harmful factors, which in turn contributes to disease progression in distant organ systems.

Association between Gut Dysbiosis and the Occurrence of SIBO, LIBO, SIFO and IMO

Gut microbiota is the aggregate of all microorganisms in the human digestive system. There are 1014 CFU/mL of such microorganisms in the human body, including bacteria, viruses, fungi, archaea and protozoa. The Firmicutes and Bacteroidetes bacteria phyla comprise 90% of the human gut microbiota. The microbiota support the healthy functioning of the human body by helping with digestion (mainly via short-chain fatty acids and amino acids) and producing short-chain fatty acids. In addition, it exhibits many physiological functions, such as forming the intestinal epithelium, intestinal integrity maintenance, the production of vitamins, and protection against pathogens. An altered composition or the number of microorganisms, known as dysbiosis, disrupts the body's homeostasis and can lead to the development of inflammatory bowel disease, irritable bowel syndrome, and metabolic diseases such as diabetes, obesity and allergies. Several types of disruptions to the gut microbiota have been identified: SIBO (Small Intestinal Bacterial Overgrowth), LIBO (Large Intestinal Bacterial Overgrowth), SIFO (Small Intestinal Fungal Overgrowth), and IMO (Intestinal Methanogen Overgrowth). General gastrointestinal problems such as abdominal pain, bloating, gas, diarrhoea and constipation are the main symptoms of dysbiosis. They lead to malabsorption, nutrient deficiencies, anaemia and hypoproteinaemia. Increased lipopolysaccharide (LPS) permeability, stimulating the inflammatory response and resulting in chronic inflammation, has been identified as the leading cause of microbial overgrowth in the gut. The subject literature is extensive but of limited quality. Despite the recent interest in the gut microbiome and its disorders, more clinical research is needed to determine the pathophysiology, effective treatments, and prevention of small and large intestinal microbiota overgrowth. This review was designed to provide an overview of the available literature on intestinal microbial dysbiosis (SIBO, LIBO, SIFO and IMO) and to determine whether it represents a real threat to human health.

The Gut-Organ-Axis Concept: Advances the Application of Gut-on-Chip Technology

The intestine is considered to be a vital digestive organ to absorb nutrients and is the largest immune organ, while numerous microorganisms coexist with the host. It is well known that the complex interactions between the gut microbiota and the host's immune system inevitably affect the function of other organs, creating an "axis" between them. During the past few years, a new technique based mainly on microfluidics and cell biology has been developed to emulate the structure, function, and microenvironment of the human gut, called the "gut-on-chip". This microfluidic chip provides insight into key aspects of gut function in health and disease, such as the gut-brain axis, gut-liver axis, gut-kidney axis, and gut-lung axis. In this review, we first describe the basic theory of the gut axis and the various composition and parameter monitoring of the gut microarray systems, as well as summarize the development and emerging advances in the gut-organ-on-chip, with a focus on the host-gut flora and nutrient metabolism, and highlight their role in pathophysiological studies. In addition, this paper discusses the challenges and prospects for the current development and further use of the gut-organ-on-chip platform.

Causal Effects of Specific Gut Microbiota on Chronic Kidney Diseases and Renal Function-A Two-Sample Mendelian Randomization Study

BACKGROUND

Targeting the gut microbiota may become a new therapeutic to prevent and delay the progression of chronic kidney disease (CKD). Nonetheless, the causal relationship between specific intestinal flora and CKD is still unclear.

MATERIALS AND METHOD

To identify genetically predicted microbiota, we used summary data from genome-wide association studies on gut microbiota in 18340 participants from 24 cohorts. Furthermore, we genetically predicted the causal relationship between 211 gut microbiotas and six phenotypes (outcomes) (CKD, estimated glomerular filtration rate (eGFR), urine albumin to creatinine ratio (UACR), dialysis, rapid progress to CKD, and rapid decline of eGFR). Four Mendelian randomization (MR) methods, including inverse variance weighted (IVW), MR-Egger, weighted median, and weighted mode were used to investigate the casual relationship between gut microbiotas and various outcomes. The result of IVW was deemed as the primary result. Then, Cochrane's Q test, MR-Egger, and MR-PRESSO Global test were used to detect heterogeneity and pleiotropy. The leave-one method was used for testing the stability of MR results and Bonferroni-corrected was used to test the strength of the causal relationship between exposure and outcome.

RESULTS

Through the MR analysis of 211 microbiotas and six clinical phenotypes, a total of 36 intestinal microflora were found to be associated with various outcomes. Among them, Class Bacteroidia (=-0.005, 95% CI: -0.001 to -0.008, p = 0.002) has a strong causality with lower eGFR after the Bonferroni-corrected test, whereas phylum Actinobacteria (OR = 1.0009, 95%CI: 1.0003-1.0015, p = 0.0024) has a strong causal relationship with dialysis. The Cochrane's Q test reveals that there is no significant heterogeneity between various single nucleotide polymorphisms. In addition, no significant level of pleiotropy was found according to MR-Egger and MR-PRESSO Global tests.

CONCLUSIONS

Through the two-sample MR analysis, we identified the specific intestinal flora that has a causal relationship with the incidence and progression of CKD at the level of gene prediction, which may provide helpful biomarkers for early disease diagnosis and potential therapeutic targets for CKD.

Perturbed gut microbiome and fecal and serum metabolomes are associated with chronic kidney disease severity

BACKGROUND

Chronic kidney disease (CKD) is a severe public health problem associated with a disordered gut microbiome. However, the functional alterations of microbiota and their cross talk with metabolism pathways based on disease severity remain unclear.

RESULTS

We performed metagenomics and untargeted metabolomics in a cohort of 68 patients with CKD of differing severities and 20 healthy controls to characterize the complex interplay between the gut microbiome and fecal and serum metabolites during CKD progression. We identified 26 microbial species that significantly changed in patients with CKD; 18 species changed as the disease progressed, and eight species changed only in a specific CKD group. These distinct changes in gut microbiota were accompanied by functional alterations in arginine and proline, arachidonic acid, and glutathione metabolism and ubiquinone and other terpenoid-quinone biosynthesis pathways during CKD progression. Further metabolomic analyses revealed that the distributions of toxic and pro-oxidant metabolites from these four essential metabolic pathways varied in the feces and serum as CKD progressed. Furthermore, we observed a complex co-occurrence between CKD severity-related bacteria and the characterized metabolites from the four essential metabolic pathways. Notably, Ruminococcus bromii, fecal hydroquinone, and serum creatinine were identified as the main contributors to the integrated network, indicating their key roles in CKD progression. Moreover, a noninvasive model including R. bromii and fecal hydroquinone, L-cystine, and 12-keto-tetrahydro-LTB4 levels classified the CKD severity (area under the curve [AUC]: > 0.9) and had better performance than the serum creatinine level for mild CKD (AUC: 0.972 vs. 0.896).

CONCLUSIONS

Perturbed CKD severity-related gut microbiota may contribute to unbalanced toxic and pro-oxidant metabolism in the gut and host, accelerating CKD progression, which may be an early diagnostic and therapeutic target for CKD. Video Abstract.

Obesity and chronic kidney disease

The prevalence of obesity has increased dramatically during the past decades, which has been a major health problem. Since 1975, the number of people with obesity worldwide has nearly tripled. An increasing number of studies find obesity as a driver of chronic kidney disease (CKD) progression, and the mechanisms are complex and include hemodynamic changes, inflammation, oxidative stress, and activation of the renin-angiotensin-aldosterone system (RAAS). Obesity-related kidney disease is characterized by glomerulomegaly, which is often accompanied by localized and segmental glomerulosclerosis lesions. In these patients, the early symptoms are atypical, with microproteinuria being the main clinical manifestation and nephrotic syndrome being rare. Weight loss and RAAS blockers have a protective effect on obesity-related CKD, but even so, a significant proportion of patients eventually progress to end-stage renal disease despite treatment. Thus, it is critical to comprehend the mechanisms underlying obesity-related CKD to create new tactics for slowing or stopping disease progression. In this review, we summarize current knowledge on the mechanisms of obesity-related kidney disease, its pathological changes, and future perspectives on its treatment.

Show Me What You Have Inside-The Complex Interplay between SIBO and Multiple Medical Conditions-A Systematic Review

The microbiota, as a complex of microorganisms in a particular ecosystem, is part of the wider term-microbiome, which is defined as the set of all genetic content in the microbial community. Imbalanced gut microbiota has a great impact on the homeostasis of the organism. Dysbiosis, as a disturbance in bacterial balance, might trigger or exacerbate the course of different pathologies. Small intestinal bacterial overgrowth (SIBO) is a disorder characterized by differences in quantity, quality, and location of the small intestine microbiota. SIBO underlies symptoms associated with functional gastrointestinal disorders (FGD) as well as may alter the presentation of chronic diseases such as heart failure, diabetes, etc. In recent years there has been growing interest in the influence of SIBO and its impact on the whole human body as well as individual systems. Therefore, we aimed to investigate the co-existence of SIBO with different medical conditions. The PubMed database was searched up to July 2022 and we found 580 original studies; inclusion and exclusion criteria let us identify 112 eligible articles, which are quoted in this paper. The present SIBO diagnostic methods could be divided into two groups-invasive, the gold standard-small intestine aspirate culture, and non-invasive, breath tests (BT). Over the years scientists have explored SIBO and its associations with other diseases. Its role has been confirmed not only in gastroenterology but also in cardiology, endocrinology, neurology, rheumatology, and nephrology. Antibiotic therapy could reduce SIBO occurrence resulting not only in the relief of FGD symptoms but also manifestations of comorbid diseases. Although more research is needed, the link between SIBO and other diseases is an important pathway for scientists to follow.

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

Background

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

Methods

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

Results

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

Conclusion

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

Trial registration

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

Supplementary Information

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

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

Background

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

Methods

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

Results

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

Conclusion

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

Systematic Review Registration

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

Alterations of gut microbial pathways and virulence factors in hemodialysis patients

Alterations in gut microbiota might contribute to uremic toxicity and immune dysregulation in patients with end-stage renal disease. Hemodialysis patients are prone to infection and higher mortality following sepsis. The virulence factors in the gut metagenome have not been well studied in hemodialysis patients, which could be employed by microorganisms to successfully thrive and flourish in their hosts. In this study, we performed shotgun metagenomics sequencing on fecal DNA collected from 16 control subjects and 24 hemodialysis patients. Our analysis shows that a number of microbial species, metabolic pathways, antibiotic resistance, and virulence factors were significantly altered in hemodialysis patients compared with controls. In particular, erythromycin resistance methylase, pyridoxamine 5-phosphate oxidase, and streptothricin-acetyl-transferase were significantly increased in hemodialysis patients. The findings in our study laid a valuable foundation to further elucidate the causative role of virulence factors in predisposing HD patients to infection and to develop treatment strategies to reduce the genetic capacities of antibiotic resistance and virulence factors in HD patients.

Physiopathological mechanisms involved in the development of hypertension associated with gut dysbiosis and the effect of nutritional/pharmacological interventions

The gut microbiota dysbiosis represents a triggering factor for cardiovascular diseases, including hypertension. In addition to the harmful impact caused by hypertension on different target organs, gut dysbiosis is capable of causing direct damage to critical organs such as the brain, heart, blood vessels, and kidneys. In this sense, it should be noted that pharmacological and nutritional interventions may influence gut microbiota composition, either inducing or preventing the development of hypertension. Some of the most important nutritional interventions at this level are represented by pro-, pre-, post- and/or syn-biotics, as well as polysaccharides, polyunsaturated fatty acids ω-3, polyphenols and fiber contained in different foods. Meanwhile, certain natural and synthetic active pharmaceutical ingredients, including antibiotics, antihypertensive and immunosuppressive drugs, vegetable extracts and vitamins, may also have a key role in the modulation of both gut microbiota and cardiovascular health. Additionally, gut microbiota may influence drugs and food-derived bioactive compounds metabolism, positively or negatively affecting their biological behavior facing established hypertension. The understanding of the complex interactions between gut microbiome and drug/food response results of great importance to developing improved pharmacological therapies for hypertension prevention and treatment. The purpose of this review is to critically outline the most relevant and recent findings on cardiovascular, renal and brain physiopathological mechanisms involved in the development of hypertension associated with changes in gut microbiota, besides the nutritional and pharmacological interventions potentially valuable for the prevention and treatment of this prevalent pathology. Finally, harmful food/drug interventions on gut microbiota are also described.

Therapeutic Potential of Photobiomodulation for Chronic Kidney Disease

Chronic kidney disease (CKD) is a growing global public health problem. The implementation of evidence-based clinical practices only defers the development of kidney failure. Death, transplantation, or dialysis are the consequences of kidney failure, resulting in a significant burden on the health system. Hence, innovative therapeutic strategies are urgently needed due to the limitations of current interventions. Photobiomodulation (PBM), a form of non-thermal light therapy, effectively mitigates mitochondrial dysfunction, reactive oxidative stress, inflammation, and gut microbiota dysbiosis, all of which are inherent in CKD. Preliminary studies suggest the benefits of PBM in multiple diseases, including CKD. Hence, this review will provide a concise summary of the underlying action mechanisms of PBM and its potential therapeutic effects on CKD. Based on the findings, PBM may represent a novel, non-invasive and non-pharmacological therapy for CKD, although more studies are necessary before PBM can be widely recommended.

Gut microbiota diversity in middle-aged and elderly patients with end-stage diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD), but the mechanism between DKD and ESRD remains unclear. Some experts have put forward the "microbial-centered ESRD development theory", believing that the bacterial load caused by gut microecological imbalance and uremia toxin transfer are the core pathogenic links. The purpose of this study was to analyze the genomic characteristics of gut microbiota in patients with ESRD, specifically DKD or non-diabetic kidney disease (NDKD).

METHODS

In this cross-sectional study, patients with ESRD were recruited in a community, including 22 DKD patients and 22 NDKD patients matched using gender and age. Fecal samples of patients were collected for 16S rDNA sequencing and gut microbiota analysis. The distribution structure, diversity, and abundance of microflora in DKD patients were analyzed by constructing species evolutionary trees and analyzing alpha diversity, beta diversity, and linear discriminant analysis effect size (LEfSe).

RESULTS

The results of our study showed that there were statistically significant differences in the richness and species of gut microbiota at the total level between DKD patients and NDKD patients. The analysis of genus level between the two groups showed significant differences in 16 bacterial genera. Among them, Oscillibacter, Bilophila, UBA1819, Ruminococcaceae UCG-004, Anaerotruncus, Ruminococcaceae, and Ruminococcaceae NK4A214 bacteria in DKD patients were higher than those in NDKD patients.

CONCLUSIONS

16S rDNA sequencing technology was used in this study to analyze the characteristics of intestinal flora in ESRD patients with or without diabetes. We found that there was a significant difference in the intestinal flora of ESRD patients caused by DKD and NDKD, suggesting that these may be potential causative bacteria for the development of ERSD in DKD patients.

Gut Microbiota Mediates the Protective Effects of Traditional Chinese Medicine Formula Qiong-Yu-Gao against Cisplatin-Induced Acute Kidney Injury

Our previous study found that Qiong-Yu-Gao (QYG), a traditional Chinese medicine formula derived from Rehmanniae Radix, Poria, and Ginseng Radix, has protective effects against cisplatin-induced acute kidney injury (AKI), but the underlying mechanisms remain unknown. In the present study, the potential role of gut microbiota in the nephroprotective effects of QYG was investigated. We found that QYG treatment significantly attenuated cisplatin-induced AKI and gut dysbiosis, altered the levels of bacterial metabolites, with short-chain fatty acids (SCFAs) such as acetic acid and butyric acid increasing and uremic toxins such as indoxyl sulfate and p-cresyl sulfate reducing, and suppressed histone deacetylase expression and activity. Spearman's correlation analysis found that QYG-enriched fecal bacterial genera Akkermansia, Faecalibaculum, Bifidobacterium, and Lachnospiraceae_NK4A136_group were correlated with the altered metabolites, and these metabolites were also correlated with the biomarkers of AKI, as well as the indicators of fibrosis and inflammation. The essential role of gut microbiota was further verified by both the diminished protective effects with antibiotics-induced gut microbiota depletion and the transferable renal protection with fecal microbiota transplantation. All these results suggested that gut microbiota mediates the nephroprotective effects of QYG against cisplatin-induced AKI, potentially via increasing the production of SCFAs, thus suppressing histone deacetylase expression and activity, and reducing the accumulation of uremic toxins, thereby alleviating fibrosis, inflammation, and apoptosis in renal tissue. IMPORTANCE Cisplatin-induced acute kidney injury is the main limiting factor restricting cisplatin's clinical application. Accumulating evidence indicated the important role of gut microbiota in pathogenesis of acute kidney injury. In the present study, we have demonstrated that gut microbiota mediates the protective effects of traditional Chinese medicine formula Qiong-Yu-Gao against cisplatin-induced acute kidney injury. The outputs of this study would provide scientific basis for future clinical applications of QYG as prebiotics to treat cisplatin-induced acute kidney injury, and gut microbiota may be a promising therapeutic target for chemotherapy-induced nephrotoxicity.

Faecal Microbiota Transplantation and Chronic Kidney Disease

Faecal microbiota transplantation (FMT) has attracted increasing attention as an intervention in many clinical conditions, including autoimmune, enteroendocrine, gastroenterological, and neurological diseases. For years, FMT has been an effective second-line treatment for Clostridium difficile infection (CDI) with beneficial outcomes. FMT is also promising in improving bowel diseases, such as ulcerative colitis (UC). Pre-clinical and clinical studies suggest that this microbiota-based intervention may influence the development and progression of chronic kidney disease (CKD) via modifying a dysregulated gut–kidney axis. Despite the high morbidity and mortality due to CKD, there are limited options for treatment until end-stage kidney disease occurs, which results in death, dialysis, or kidney transplantation. This imposes a significant financial and health burden on the individual, their families and careers, and the health system. Recent studies have suggested that strategies to reverse gut dysbiosis using FMT are a promising therapy in CKD. This review summarises the preclinical and clinical evidence and postulates the potential therapeutic effect of FMT in the management of CKD.

The Dual Roles of Protein-Bound Solutes as Toxins and Signaling Molecules in Uremia

In patients with severe kidney disease, renal clearance is compromised, resulting in the accumulation of a plethora of endogenous waste molecules that cannot be removed by current dialysis techniques, the most often applied treatment. These uremic retention solutes, also named uremic toxins, are a heterogeneous group of organic compounds of which many are too large to be filtered and/or are protein-bound. Their renal excretion depends largely on renal tubular secretion, by which the binding is shifted towards the free fraction that can be eliminated. To facilitate this process, kidney proximal tubule cells are equipped with a range of transport proteins that cooperate in cellular uptake and urinary excretion. In recent years, innovations in dialysis techniques to advance uremic toxin removal, as well as treatments with drugs and/or dietary supplements that limit uremic toxin production, have provided some clinical improvements or are still in progress. This review gives an overview of these developments. Furthermore, the role protein-bound uremic toxins play in inter-organ communication, in particular between the gut (the side where toxins are produced) and the kidney (the side of their removal), is discussed.

The impact of prebiotic fructooligosaccharides on gut dysbiosis and inflammation in obesity and diabetes related kidney disease

Obesity is an extensive health problem worldwide that is frequently associated with diabetes. It is a risk factor for the development of several diseases including diabetic nephropathy. Recent studies have reported that gut dysbiosis aggravates the progression of obesity and diabetes by increasing the production of uremic toxins in conjunction with gut barrier dysfunction which then leads to increased passage of lipopolysaccharides (LPS) into the blood circulatory system eventually causing systemic inflammation. Therefore, the modification of gut microbiota using a prebiotic supplement may assist in the restoration of gut barrier function and reduce any disturbance of the inflammatory response. In this review information has been compiled concerning the possible mechanisms involved in an increase in obesity, diabetes and kidney dysfunction via the exacerbation of the inflammatory response and its association with gut dysbiosis. In addition, the role of fructooligosaccharides (FOS), a source of prebiotic widely available commercially, on the improvement of gut dysbiosis and attenuation of inflammation on obese and diabetic conditions has been reviewed. The evidence confirms that FOS supplementation could improve the pathological changes associated with obesity and diabetes related kidney disease, however, knowledge concerning the mechanisms involved is still limited and needs further elucidation.

Intestinal Carriage of Extended-spectrum β-lactamase and Carbapenemase-producing Enterobacteriaceae in Hemodialysis Patients

Background: Gastrointestinal colonization with resistant pathogens is significant because they could be easily transmitted to other hosts or spread to different microbiota through mobile genetic elements. Objectives: This study assessed the prevalence of fecal carriage of extended-spectrum β-lactamase-producing and carbapenemase-producing Enterobacteriaceae (ESBL-E and CPE, respectively) among hemodialysis patients and the factors affecting its occurrence in a hospital in Tehran. Methods: From January 2018 to May 2019, 150 hemodialysis patients referred to a hospital in Tehran were sampled in this study. Stool samples of the patients were diluted in saline and cultured on MacConkey agar plates containing cefotaxime, ceftazidime, imipenem, and meropenem discs. The clinical data were analyzed to identify the risk factors using a logistic regression model. Results: The colonization rate of ESBL-E was 48.6%, while only 2% of patients were identified as the carriers of CPE (3 of 150). A higher prevalence rate was obtained for intestinal carriage of ESBL-E among hemodialysis patients aged 18 to 42 years using multivariate analysis. The prevalence rate of multidrug-resistant isolates was 73.8%. The blaCTX-M1 gene was identified as the most prevalent ESBL gene. Among carbapenemase-encoding genes, blaKPC and blaoxa-48 were found in 12 and two isolates, respectively. Conclusions: These results demonstrated a high prevalence rate of ESBLs among hemodialysis patients, although this rate was low for carbapenemases. Therefore, more control measures should be taken in hospitals to prevent the spread of antibiotic resistance genes in healthcare settings.

Sources, Processing-Related Transformation, and Gut Axis Regulation of Conventional and Potential Prebiotics

One strategy to achieve a balanced intestinal microbiota is to introduce prebiotics. Some substances present in the diet, such as soybean extracts, koji glycosylceramides, grape extracts, tea polyphenols, and seaweed extracts, can be considered as potential prebiotics, because they can selectively stimulate the proliferation of beneficial bacteria in the intestine. However, the discovery of novel prebiotics also involves advances in screening methods and the use of thermal and non-thermal processing techniques to modify and enhance the properties of beneficial organisms. The health benefits of prebiotics are also reflected by their participation in regulating the microbiota in different gut axes. In the present review, we introduced the field of prebiotics, focusing on potential prebiotic substances, the process of screening potential prebiotics, the transformation of prebiotics by food-processing technologies, and the roles of prebiotics on gut axis regulation, which, it is hoped, will promote the discovery and utilization of novel prebiotics.

Can resveratrol supplementation reduce uremic toxins plasma levels from the gut microbiota in non-dialyzed chronic kidney disease patients?

BACKGROUND

Uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (pCS), and indole-3-acetic acid (IAA) produced by the gut microbiota are recognized as risk factors for many comorbidities, including cardiovascular diseases. Chronic kidney disease (CKD) patients have an accumulation of these toxins and nutritional strategies have been proposed to mitigate gut dysbiosis and, consequently, reduce these toxins. This study aimed to evaluate the effects of resveratrol supplementation on the plasma levels of IS, pCS, and IAA in non-dialyzed CKD patients.

METHODS

In this placebo-controlled crossover study, twenty non-dialyzed patients were randomly divided into two groups: they received either one capsule/day containing 500 mg of trans-resveratrol (63 ± 7.5 years, glomerular filtration ratio (GFR): 34 ± 14 mL/min, body mass index (BMI): 26.8 ± 5.6 kg/m²) or a placebo containing 500 mg wheat flour (62 ± 8.4 years, GFR: 34 ± 13 mL/min, BMI: 28.6 ± 4.4 kg/m²) during four weeks. After eight weeks of washout (no supplementation), another four weeks of supplementation with crossover was initiated. IS, IAA, and pCS plasma levels were quantified by the Reverse Phase High-Efficiency Liquid Chromatography method with fluorescent detection. The mRNA expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor kappa B (NF-κB) in peripheral blood mononuclear cells was evaluated by polymerase chain reaction. C-reactive protein (CRP) plasma levels were also evaluated.

RESULTS

As expected, the uremic toxins levels were negatively correlated with GFR, but no effect of trans-resveratrol supplementation was found on levels of IS, IAA, and pCS. There was a positive correlation between IS and Nrf2 (r = 0.24, p = 0.03) and also between IS and CRP (r = 0.21, p = 0.05).

CONCLUSION

Supplementation with trans-resveratrol did not reduce the plasma levels of IS, pCS, and IAA in non-dialyzed CKD patients. The interactions among uremic toxins and anti- and pro-inflammatory pathways deserve more studies.

Structural modulation of gut microbiota during alleviation of experimental passive Heymann nephritis in rats by a traditional Chinese herbal formula

BACKGROUND

Jianpi-Qushi-Heluo formula (JQHF) has been used to treat idiopathic membranous nephropathy (IMN) in hospitals for many years.

PURPOSE

Elucidating the protective effect and exploring the potential mechanism of JQHF against IMN.

METHODS

Passive Heymann nephritis (PHN) was induced in rats by a single tail vein injection of anti-Fx1A antiserum. Then, the animals were treated with JQHF at 16.2 g/kg or 32.4 g/kg, with benzepril (10 mg/kg) as a positive control. Renal function was evaluated by biochemical measurements and pathological testing. Fecal samples were collected before and after treatment to analyze the gut microbiota composition by shotgun whole metagenome sequencing.

RESULTS

JQHF exhibited potent efficacy in ameliorating PHN at both doses, as revealed by decreasing the deposition of IgG and C5b-9, relieving podocyte injury, and reducing glomerular and tubular cell apoptosis. The lower dose was corresponding to the clinical dosage and showed better therapeutic effects than the higher dose. Metagenomic analysis showed that gavage with 16.2 g/kg of JQHF shifted the structure of the gut microbiota in PHN rats and significantly increased the relative abundances of Prevotella copri, Lactobacillus vaginalis and Subdoligranulum variabile. Particularly, S. variabile was strongly negatively correlated with serum levels of TC and TG, the deposition of IgG and C5b-9, and apoptosis of glomerular cells.

CONCLUSIONS

The JQHF is an effective agent for the treatment of experimental PHN. The PHN-allevating effect of JQHF is associated with specific alternation of gut microbiota.