Microbiome-metabolome reveals the contribution of gut-kidney axis on kidney disease

Impact of gut microbiota in chronic kidney disease: natural polyphenols as beneficial regulators

Chronic kidney disease (CKD) poses a severe health risk with high morbidity and mortality, profoundly affecting patient quality of life and survival. Despite advancements in research, the pathophysiology of CKD remains incompletely understood. Growing evidence links CKD with shifts in gut microbiota function and composition. Natural compounds, particularly polyphenols, have shown promise in CKD treatment due to their antioxidant and anti-inflammatory properties and their ability to modulate gut microbiota. This review discusses recent progress in uncovering the connections between gut microbiota and CKD, including microbiota changes across different kidney diseases. We also examine metabolite alterations,such as trimethylamine-N-oxide, tryptophan derivatives, branched-chain amino acids, short-chain fatty acids, and bile acids,which contribute to CKD progression. Further, we outline the mechanisms through which polyphenols exert therapeutic effects on CKD, focusing on signaling pathways like nuclear factor kappa-B (NF-κB), mitogen-activated protein kinase (MAPK), mammalian target of rapamycin (mTOR), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), phosphatidylin-ositol-3-kinase (PI3K)/protein kinase B (Akt), and toll like receptors (TLR), as well as their impact on gut microbiota. Lastly, we consider how dietary polyphenols could be harnessed as bioactive drugs to slow CKD progression. Future research should prioritize multi-omics approaches to identify patients who would benefit from polyphenolic interventions, enabling personalized treatment strategies to enhance therapeutic efficacy.

Quercetin ameliorates hyperuricemic nephropathy through improving gut dysfunctions and decreasing gut bacteria-derived uremic toxins

BACKGROUND

Hyperuricemia (HUA) is closely associated with gut dysbiosis, yet the role of microbial metabolism in hyperuricemic nephropathy (HN) remains poorly understood. Quercetin has shown urate-lowering and nephroprotective effects, but its therapeutic mechanisms, particularly in modulating the gut microbiome and microbial metabolism, remain elusive.

PURPOSE

This study investigates the therapeutic effects of quercetin on HN and explores its role in regulating host-microbial co-metabolism.

METHODS

A spontaneous HUA rat model (Uox-/- rats) was used to evaluate the therapeutic effect of quercetin. Multi-omics analyses, including gut microbiome profiling, peripheral untargeted metabolome, and targeted quantification of gut bacteria-derived uremic toxins, were performed. An integrated network analysis was conducted to uncover potential host-microbe metabolic interactions.

RESULTS

Quercetin treatment significantly reduced serum uric acid, creatinine, and blood urea nitrogen, ameliorated renal inflammation, fibrosis and oxidative stress, and improved gut dysbiosis and intestinal barrier dysfunction. Notably, high-dose quercetin downregulated Blautia, a key gut bacterium associated with uremic toxin production, and suppressed microbial phenylalanine metabolism, leading to decreased levels of gut bacteria-derived nephrotoxic metabolites (e.g., 3-phenyllactic acid, hippuric acid, and N-acetyl-l-phenylalanine). These uremic toxins were positively correlated with markers of kidney injury and proinflammatory cytokines. Mechanistically, quercetin modulated microbial enzymatic pathways involved in phenylalanine metabolism, thereby disrupting the formation of nephrotoxic metabolites and alleviating renal damage.

CONCLUSIONS

This study provides multi-omics evidence that quercetin ameliorates HN by regulating gut dysfunctions and decreasing gut bacteria-derived uremic toxins through host-microbial co-metabolism. These findings highlight the therapeutic potential of microbiota-targeted interventions in HUA-associated kidney diseases.

Altered fecal microbial and metabolic profiles reveal potential mechanisms underlying anemia in patients with chronic renal failure

The gut microbiomes communicate with the kidney and may play a crucial role in the development of anemia in patients with chronic renal failure (CRF). However, the alterations in microbiota and their association with functional metabolites remain unclear. We performed metagenomics and untargeted metabolomics in a cohort of 30 patients with anemia of CRF and 20 healthy controls (HCs) to identify the characteristics of the gut microbiome and explore its potential interactions with the host. Decreased microbiota diversity and significant compositional differences were observed in the patients with anemia of CRF. We identified six gut microbiotas significantly changed in the patients with anemia of CRF, particularly Faecalibacterium prausnitzii, Prevotella copri, and Escherichia coli, which were closely correlated with hemoglobin (Hb) levels and estimated glomerular filtration rate (eGFR). These changes were accompanied by functional alterations in distinctive microbial pathways. Further fecal and serum metabolomics revealed fecal 12-KETE-LTB4 in arachidonic acid metabolism, uracil and L-aspartic acid in beta-alanine metabolism, gulonic acid in ascorbate and aldarate metabolism, accompanied by the top 15 differential serum metabolites that were closely correlated with Hb levels. Furthermore, we observed a complex co-occurrence between anemia of CRF-related gut microbiota species and the characterized metabolites. Moreover, a non-invasive model incorporating Faecalibacterium prausnitzii and Prevotella copri, combined with fecal 12-KETE-LTB4, uracil, L-aspartic acid, and gulonic acid, distinguished the patients with anemia of CRF from HCs (area under the curve: 0.879). Collectively, our results suggest that a disordered gut microbiome associated with functional metabolites may be a non-invasive diagnostic and therapeutic target for anemia of CRF.IMPORTANCEAnemia is a prevalent complication in patients with chronic renal failure (CRF), which is associated with a high burden of morbidity and adverse clinical outcomes. Various evidence suggests that gut microbiota dysbiosis may contribute to the pathogenesis of anemia in CRF, although the mechanism is still obscure. This work provides substantial evidence identifying the specific characteristics of the gut microbiomes accompanied by functional alterations in anemia of CRF. We highlight the intricate interactions among the anemia of CRF-related gut microbiome and the functional metabolites, which may regulate toxic accumulation, oxidative stress, and immune-inflammatory responses to induce and exacerbate anemia in patients with CRF. Furthermore, we found that evaluating the gut microbiota and fecal metabolites in combination might be a non-invasive prognostic indicator of CRF-induced anemia. These findings provide important insights into the role of gut microbiota in the mechanism of anemia in CRF.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT05543291.

Dietary butyric acid intake, kidney function, and survival: The National Health and Nutrition Examination Surveys, 2005-2018

BACKGROUND

Although preclinical data support the hypothesis that butyric acid supplementation improves kidney health, the clinical significance of dietary butyric acid intake in patients with chronic kidney disease (CKD) remains unconfirmed in large-sample studies. This study aimed to investigate the association between dietary butyric acid intake and all-cause mortality in the United States population, stratified by kidney function.

METHODS

We examined the relationship between dietary butyric acid intake, assessed through a 24-h dietary recall, and all-cause mortality among 23,008 consecutive adult participants from the National Health and Nutrition Examination Surveys (NHANES, 2005-2018), categorized by impaired versus normal kidney function (estimated glomerular filtration rate <60 vs ≥ 60 mL/min/1.72 m2), using multivariable Cox models. We also employed a restricted cubic spline based on Cox regression models to elucidate the nonlinear relationship between dietary butyric acid intake and mortality in patients.

RESULT

In participants with impaired kidney function, high dietary butyric acid intake was associated with lower mortality, while lower intake levels (reference) showed no such association: adjusted HRs (aHRs) were 0.67 (95 % CI: 0.45, 1.00), 0.65 (95 % CI: 0.45, 0.94), and 0.58 (95 % CI: 0.38, 0.89) for intake levels of the square root of butyric acid 0.25-0.45, 0.45-0.75, and >0.75 g/day, respectively. However, in participants with normal kidney function, no association between butyric acid levels and mortality was observed. Additionally, we identified an L-shaped association between the levels of the square root of dietary butyric acid intake and all-cause mortality in the CKD population, reaching a plateau at 0.52 g/day (butyric acid intake of approximately 0.27 g/day).

CONCLUSION

This study revealed a nonlinear association between high dietary butyric acid intake and reduced all-cause mortality in patients with chronic kidney disease. A plateau occurs after 0.27 g/day, and for individuals with CKD whose butyric acid intake is below approximately 0.27 g/day, increasing a butyrate-rich diet or supplementing with butyric acid preparations may help prevent progression to renal failure and associated adverse outcomes in CKD patients, thereby reducing mortality. Therefore, it can be considered a new therapeutic strategy for the treatment of chronic kidney disease.

Gut microbiota-derived metabolite phenylacetylglutamine in cardiovascular and metabolic disease

The aging of population coupled with unhealthy dietary habits among residents has led to a rise in the incidence of cardiovascular and metabolic diseases (CVMDs). Extensive research has highlighted the role of gut microbiota-derived metabolites in CVMDs. Among these metabolites, phenylacetylglutamine (PAGln), a meta-organismal prothrombotic metabolite, has been proved to promote the progression of CVMDs. This bacterial derived metabolite is a byproduct of amino acid comes from phenylalanine (Phe) in the diet. There are increasing evidence showing that the level of PAGln is associated with the risk of developing CVMDs. To provide a comprehensive understanding of the role of PAGln in CVMDs, this review delves into the production and metabolic pathways of PAGln and discusses the links of PAGln and the pathogenesis of CVMDs.

Investigation of a targeted panel of gut microbiome-derived toxins in children with chronic kidney disease

BACKGROUND

The gut-kidney axis is implicated in chronic kidney disease (CKD) morbidity. We describe how a panel of gut microbiome-derived toxins relates to kidney function and neurocognitive outcomes in children with CKD, consisting of indoleacetate, 3-indoxylsulfate, p-cresol glucuronide, p-cresol sulfate, and phenylacetylglutamine.

METHODS

The Chronic Kidney Disease in Children (CKiD) cohort is a North American multicenter prospective cohort that enrolled children aged 6 months to 16 years with estimated glomerular filtration rate (eGFR) 30-89 ml/min/1.73 m2. Data from the 2-year study visit were used for this analysis. Toxin quantification (Metabolon Inc., Durham, NC) was performed with ultra-high performance liquid chromatography/tandem mass spectrometry. Executive function and echocardiograms were assessed. Regression analysis examined the association of toxin levels with eGFR, CKD etiology, and neurocognitive and cardiac assessments (adjusted for age, sex, and urine protein:creatinine [UPCR]).

RESULTS

There were 150 CKiD participants included in this study. All toxins levels were significantly inversely correlated with eGFR (Spearman's rho - 0.45 to - 0.69). Children with non-glomerular CKD had significantly higher levels of 3-indoxylsulfate, phenylacetylglutamine, and p-cresol glucuronide. The toxin levels did not associate with neurocognitive outcomes. P-cresol glucuronide and phenylacetylglutamine negatively associated with left ventricular mass index z score, but did not associate with left ventricular hypertrophy.

CONCLUSIONS

Children with CKD have high levels of circulating gut microbiome-derived toxins. The levels of these toxins are strongly correlated with eGFR. There appear to be differences in toxin level based on glomerular versus non-glomerular etiology, even when accounting for the differences in eGFR between these two subgroups. In this sample, we did not detect any associations between these toxin levels and neurocognitive or cardiac outcomes.

Risk Factors for Chronic Kidney Disease in Patients With Crohn's Disease

BACKGROUND

Patients with inflammatory bowel diseases (IBD), including Crohn's disease (CD), are at risk of complications, including kidney disease. It is important to identify IBD patients at higher risk of chronic kidney disease (CKD) to improve prevention and treatment. Here, we investigated the clinical and metabolomic characteristics of CD patients who develop CKD.

METHODS

We identified adult CD patients with (CD + CKD, n = 87) and selected CD patients without CKD (CD controls) matched by age, race, and gender. We collected data on demographic characteristics (age, smoking status, ethnicity, gender), IBD characteristics (diagnosis, Montreal classification, medication use, IBD-related surgeries, perianal disease), and kidney-related factors (primary sclerosing cholangitis, end-stage renal disease, hypertension, diabetes, organ transplantation, and nephrolithiasis). Univariate and multivariate analyses were conducted and odds ratios were calculated to identify risk factors for CKD. Serum samples were collected for untargeted metabolomic analysis.

RESULTS

Chronic kidney disease was far more common in CD patients than UC patients. Crohn's disease patients with kidney stones had a 10-fold higher risk of developing CKD than those without kidney stones. Crohn's disease patients with more than 2 IBD-related surgeries had a 7.3-fold higher risk of developing CKD than those who had not undergone surgery. There was no relationship between the number of biologics used or mesalamine use and the risk of CKD. The serum of CD + CKD patients had elevated levels of pro-inflammatory metabolites and those linked to kidney injury.

CONCLUSIONS

We recommend regular kidney function monitoring and ensuring proper hydration to prevent or manage potential kidney-related complications in CD patients. Patients with resections and kidney stones are particularly vulnerable.

Morroniside alleviates cisplatin-induced renal injury and gut dysbiosis via the gut-kidney axis and ferroptosis

BACKGROUND

The clinical use of cisplatin as a chemotherapeutic agent is limited owing to its nephrotoxicity. Oxidative stress and ferroptosis are responsible for cisplatin-induced renal injury.

PURPOSE

The protective effects of morroniside against cisplatin-induced renal injury were evaluated and its underlying molecular mechanisms were elucidated.

METHODS

An animal model of cisplatin-induced renal injury was established using male C57BL/6 mice. Renal function was assessed by measuring serum creatinine (CRE), uric acid (UA), and blood urea nitrogen (BUN) levels. Antioxidant enzyme activity and pro-inflammatory cytokine levels were determined, and histological studies of renal and colon tissues were performed. Western blotting and immunohistochemical analysis were performed to determine the expression of ferroptosis-related proteins and nuclear factor erythroid 2-related factor (Nrf)2 signaling pathway. Gut microbiota were analyzed using 16S rRNA sequencing. Cisplatin- or erastin-induced renal tubular epithelial cell (HK-2 cells) models were established. Intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential were measured. The expression of Nrf2, heme oxygenase 1 (HO-1), tumor protein 53 (p53) and glutathione peroxidase (GPX)4 proteins were determined using immunofluorescence.

RESULTS

Morroniside significantly ameliorated cisplatin-induced renal dysfunction, as evidenced by decreased serum CRE, UA, and BUN levels. It reduced pro-inflammatory cytokine levels, enhanced antioxidant enzyme levels, and improved renal and colon histology. Morroniside corrected gut dysbiosis, reduced ROS levels, increased mitochondrial membrane potential, and decreased HK-2 cell apoptosis, alleviating cisplatin- or erastin-induced oxidative stress and ferroptosis.

CONCLUSION

Morroniside mitigated cisplatin-induced renal injury by inhibiting ferroptosis through the GPX4/p53 pathway, reducing oxidative stress via Nrf2/HO-1 axis, and improving gut microbiota dysbiosis, indicating its potential in mitigating cisplatin-induced renal injury.

Association of the gut microbiome with diabetic nephropathy and the mediated effect of metabolites: friend or enemy?

OBJECTIVE

The effects of gut microbiome and its metabolites on diabetic nephropathy (DN) have been inadequately elucidated. The aim of this study is to assess the causal effect of gut microbiome on DN and the mediated effect of metabolites by a two-step Mendelian randomization (MR).

METHODS

Datasets of gut microbiome, metabolites, and DN were acquired in genome-wide association studies and screened for single nucleotide polymorphisms according to the underlying assumptions of MR. Subsequently, inverse variance weighted was used as the primary method for MR analysis to assess the causal effect of gut microbiome on DN and the mediated effect of metabolites. Finally, MR-Egger intercept, Cochran's Q test, and leave-one-out sensitivity analysis were used to assess the horizontal pleiotropy, heterogeneity, and robustness of the results, respectively.

RESULTS

The MR analysis demonstrated that Parabacteroides merdae increased the genetic susceptibility to DN by reducing acetylcarnitine (C2) to propionylcarnitine (C3) ratio (mediated proportion 8.95%, mediated effect 0.024) and alpha-ketobutyrate to 3-methyl-2-oxovalerate ratio (mediated proportion 19.90%, mediated effect 0.053). MR Egger showed that these results lack horizontal pleiotropy (p ≥ 0.05). Cochran's Q and sensitivity analysis suggested these results had no heterogeneity (p ≥ 0.05) and were robust.

CONCLUSION

Our findings revealed the pathway by which Parabacteroides merdae increased the genetic susceptibility to DN by regulating acetylcarnitine (C2) to propionylcarnitine (C3) ratio and alpha-ketobutyrate to 3-methyl-2-oxovalerate ratio. It provides new genetic insights for understanding the pathogenesis of DN and related drug research.

Bidirectional Interaction Between Chronic Kidney Disease and Porphyromonas gingivalis Infection Drives Inflammation and Immune Dysfunction

Introduction: Chronic kidney disease (CKD) is characterized by a decline in renal function, increased mortality, and significant impairments in the immune system and function of immune cells. These alterations are often derived by uremic toxins, which, in turn, modify the immune system's response to infections. Our research investigates the progression of Porphyromonas gingivalis (P. gingivalis) infection during CKD and its subsequent impact on kidney failure. Methods: We utilized two infectious models, a chamber model representing short-term local inflammation and alveolar bone loss that mimic chronic infection of periodontium, both in conjunction with a CKD model. Additionally, our in vitro studies employed primary macrophages, osteoclasts, and lymphocytes to characterize the immune responses to P. gingivalis and pathogen-associated molecular patterns (PAMPs) in the presence of uremic toxins. Results and Conclusion: Our findings demonstrate that uremic toxins, such as indoxyl sulfate (IS), alter responses of macrophages and lymphocytes to P. gingivalis. In vivo, CKD significantly enhanced P. gingivalis survival and infection-induced alveolar bone loss. The increased distribution of pathogen within peripheral tissues was associated with altered inflammatory responses, indicating that CKD promotes infection. Moreover, P. gingivalis-infected mice exhibited a marked increase in renal inflammation, suggesting that the relationship between uremia and infection is bidirectional, with infection exacerbating kidney dysfunction. Furthermore, we observed that infected CKD mice exhibit decreased serum immunoglobulin G (IgG) levels compared to infected mice without CKD, implying that uremia is associated with immune dysfunction characterized by immunodepression and impaired B lymphocyte function.

Investigating the renoprotective effects of Polygonatum sibiricum polysaccharides (PSP) on D-galactose-induced aging mice: insights from gut microbiota and metabolomics analyses

Introduction

Polygonatum sibiricum polysaccharides (PSP) have been suggested to possess various health benefits, including anti-aging and renoprotective effects. However, the mechanisms underlying PSP's protective effects on kidney function, particularly in the context of aging, remain unclear. This study explores how PSP protects against D-galactose (D-gal)-induced kidney damage in aging mice, focusing on gut microbiota and metabolomics.

Methods

Mice were assigned to five groups: control, model (D-gal), vitamin C, low-dose PSP, and high-dose PSP, and treated for 8 weeks. Kidney pathology was assessed via H&E and Masson's trichrome staining. 16S rRNA sequencing analyzed gut microbiota, and non-targeted metabolomics identified metabolic changes. Correlations between gut bacteria and metabolites were examined.

Results

PSP alleviated renal damage, reducing tubular atrophy, epithelial swelling, and collagen deposition. It increased beneficial gut bacteria (e.g., Lactobacillus, Bifidobacterium) and altered 23 metabolites linked to pathways such as amino acid and sphingolipid metabolism. Gut microbiota and metabolites were strongly correlated, indicating PSP's role in regulating the gut-kidney axis.

Conclusion

PSP protects against age-related kidney damage by modulating gut microbiota and metabolic pathways, highlighting its therapeutic potential for kidney aging through the gut-kidney axis.

Evaluating serum S-Equol, indoxyl sulfate, and TMAO in predicting urinary stones in children: a prospective study

Gut microbiota is vital in maintaining health and has been implicated in urinary stone disease. Patients with and without stones have different microbial compositions. In this context, we assessed serum levels of S-equol, indoxyl sulfate (IS), and trimethylamine N-oxide (TMAO), which are metabolites thought to be associated with gut microbiota, and their prognostic values in predicting stone formation in children with urinary stone disease. The study population consisted of children aged between one month and 18 years with urinary stone disease. The patient group consisted of 44 children with urinary stone disease, and the control group consisted of 44 healthy children who were matched with the patient group in terms of age and gender. The study's primary outcomes were the differences between the groups in serum metabolite levels. Serum S-equol and TMAO levels were significantly lower in the patient group than in the control group. There was no significant difference between the groups in serum IS levels. There were also no significant correlations between serum metabolite levels and age in either group. Children with urinary stone disease had significantly lower serum S-equol and TMAO levels than healthy control subjects, suggesting a possible link between these metabolites and stone formation.

Dietary Guidelines Post Kidney Transplant: Is This the Missing Link in Recovery and Graft Survival?

The physiology of a transplanted kidney is affected from the moment it is separated from the donor. The risk of complications arising from surgery are highly associated with ischemic-reperfusion injury (IRI) due to the effects of hypoxia and oxidative stress during the procurement, preservation and reperfusion procedures. Hypoxia promotes the formation of reactive oxygen species (ROS) and it seems apparent that finding ways of optimising the metabolic milieu for the transplanted kidney would improve recovery and graft survival. Studies have demonstrated the benefits of nutrition and antioxidant compounds in mitigating the disturbance of energy supply to cells post-transplant and at improving long-term graft survival. Particularly in patients who may be nutritionally deficient following long-term dialysis. Despite the high incidence of allograft failure, a search of the literature and grey literature reveals no medical nutriti on therapy guidelines on beneficial nutrient intake to aid transplant recovery and survival. This narrative review aims to summarise current knowledge of specific macro and micronutrients and their effect on allograft recovery and survival in the perioperative period, up to 1-year post transplant, to optimise the metabolic environment and mitigate risk to graft injury.

Perillaldehyde ameliorates sepsis-associated acute kidney injury via inhibiting HSP90AA1-mediated ferroptosis and pyroptosis: Molecular structure and protein interaction of HSP90AA1

Heat shock protein 90α (HSP90AA1) is a molecular chaperone involved in a variety of cellular processes. Special attention is paid to how perillaldehyde ameliorates kidney injury by inhibiting HSP90AA1-mediated iron and pyrotoxicity, and in-depth analysis of the molecular structure and protein interactions of HSP90AA-1. The interaction between perillaldehyde and HSP90AA1 and the effect of perillaldehyde on the molecular structure of HSP90AA1 were analyzed by molecular docking and surface plasmon resonance technique. Western blot and immunohistochemical results showed that perillaldehyde could decrease the expression of HSP90AA1 and change its distribution in the kidney. Molecular docking and surface plasmonic resonance experiments revealed the high affinity binding between perillaldehyde and HSP90AA1, and further analysis showed that perillaldehyde could induce the conformational change of HSP90AA1, thereby inhibiting its function.

Gut microbiota may mediate the causality of statins on diabetic nephropathy: a mediation Mendelian randomization study

BACKGROUND

Increasing evidence indicates that statins may increase the risk of developing diabetic nephropathy (DN). As the gut-kidney axis concept gains traction, it remains unclear whether statins contribute to the onset and progression of DN by modulating gut microbiota.

OBJECTIVE

To investigate the association between statins and DN and the proportion of this association mediated through gut microbiota.

METHOD

This study utilized a two-sample Mendelian randomization (MR) approach and a cross-sectional observational design to investigate the causal relationships among statins, 473 gut microbiota, and DN. Furthermore, mediation MR analysis was employed to explore the potential mediating effects of gut microbiota in the statins-DN relationship.

RESULTS

HMGCR inhibitors were causally linked to the increased incidence of DN (odds ratio [OR]: 0.732, 95% confidence interval [CI] 0.647, 0.828, PFDR = 0.000004). Supporting results from a cross-sectional study based on the Medical Information Marketplace in Intensive Care (MIMIC-IV) database also indicated this association (OR: 0.74, 95% CI: 0.61, 0.91, P = 0.004). Among the 473 identified gut microbiota species, 13 (PFDR < 0.05) were causally associated with DN. The mediation MR analysis revealed that 10 gut microbiota mediated the relationship between statins and DN, acting as either protective or risk factors (P < 0.05). In addition, HMGCR and related proteins may be involved in lipid metabolism, insulin resistance, and AMPK signaling pathway.

CONCLUSION

Statins may become a risk factor for DN by increasing or decreasing the abundance of specific gut microbiota. These specific gut bacteria have the potential to become a new indicator for guiding the clinical use of statins in diabetic patients.

The gut microbiome and dietary metabolites in the treatment of renal cell carcinoma

The gut microbiome is interlinked with renal cell carcinoma (RCC) and its response to systemic treatment. Mounting data suggests that certain elements of the gut microbiome may correlate with improved outcomes. New generation sequencing techniques and advanced bioinformatic data curation are accelerating the investigation of specific markers and metabolites that could predict treatment response. A variety of new therapeutic strategies, such as fecal microbiota transplantation, probiotic supplements, and dietary interventions, are currently being developed to modify the gut microbiome and improve anticancer therapies in patients with RCC. This review discusses the preliminary evidence indicating the role of the microbiome in cancer treatment, the techniques and tools necessary for its proper study and some of the current forms with which the microbiome can be modulated to improve patient outcomes.

Polyphenols-rich Portulaca oleracea L. (purslane) alleviates ulcerative colitis through restiring the intestinal barrier, gut microbiota and metabolites

Ulcerative colitis (UC) is a recurrent intestinal disease caused by a complex of factors, and there are serious adverse effects and tolerance problems associated with the current long-term use of therapeutic drugs. The development of natural food sources and multi-targeted drugs for the treatment of UC is imminent. Portulaca oleracea L. (PO), as a vegetable, has been shown in studies to have an anti-UC effects. However, the relationship between the abundant active ingredients contained in Portulaca oleracea L. and the improvement of intestinal barrier, gut microbiota and metabolites is unclear. In the present study, Portulaca oleracea L. which was found to be rich in phenolic acid-based active ingredients, were effective in alleviating dextran sulfate sodium (DSS)-induced body weight loss, disease activity index (DAI) score and colon length in mice. It also decreased C-reactive protein (CRP) and myeloperoxidase (MPO) responses, reduced the permeation of fluorescein isothiocyanate (FITC)-dextran, lipopolysaccharide (LPS) and evans blue (EB), and improved histopathological scores. Meanwhile, in vitro and in vivo validation revealed the protective effects of purslane on the intestinal barrier indicators ZO-1, Occludin and Claudin-1, and inhibited the expression of inflammation-associated iNOS and NLRP3 proteins through the NF-κB signaling pathway. In addition, purslane increased the diversity of the intestinal flora, enhancing the proportion of the genera Butyricoccus, Dorea and Bifidobacterium and decreasing the percentage of Bacteroides, Turicibacter and Parabacteroides. Serum metabolomics analysis showed that the imbalance of 39 metabolites was significantly reversed after PO deployment. Enrichment analysis showed that Pentose phosphate pathway and Pyruvate metabolism pathway were the key pathways of PO against UC. Overall, purslane effectively improved the intestinal barrier disruption and intestinal inflammation by inhibiting the NF-κB signaling pathway, and adjusted the disorder of gut microbiota and metabolites to exert anti-UC effects.

Native potential probiotics and postbiotics improve the gut-kidney axis by the modulation of autophagy signaling pathway

The gut-kidney axis is the bidirectional relationship between the gut microbiota and the kidney function. Chronic inflammatory responses can impair kidney function and probiotics and postbiotics agents can have positive effects on gut health and kidney function by modulating inflammation through affecting autophagy signaling pathway. The aim of the current study was to evaluate the properties of our probiotic and postbiotics to improve kidney health by focusing the autophagy signaling pathway. The probiotic and postbiotics of four Lactobacillus and two Bifidobacterium strains were selected. Dextran sulfate sodium induced colitis in mice, and probiotics and postbiotics treatments were accomplished in animal experiment. A qPCR assay was performed to assess the gene expression involved in the autophagy process in the kidney. In contrast to the dextran sulfate sodium group, both the probiotic and postbiotics cocktails exhibited the capacity to inhibit colitis-associated indicators. Of note, the postbiotics cocktails demonstrated a greater efficacy in preventing colitis-related indicators and also it could display a more pronounced effect in upregulating autophagy-related genes. Our native potential probiotics and postbiotics can be able to reduce gut inflammation and cope with kidney inflammation by triggering autophagy signaling pathway through the considerable impact on gut-organ axis. There is an encouraging concept about the anti-inflammatory effects of our probiotics and postbiotics cocktails with least side effects as a supplementary treatment not only in the gut, but also in the other organs particularly kidneys.

Impact of immune cell metabolism on membranous nephropathy and prospective therapy

Membranous nephropathy (MN) is a primary glomerular disease commonly causing adult nephrotic syndrome. Characterized by thickened glomerular capillary walls due to immune complex deposition, MN is a complex autoimmune disorder. Its pathogenesis involves immune deposit formation, complement activation, and a heightened risk of renal failure. Central to MN is immune system dysfunction, particularly the dysregulation of B and T cell responses. B cells contribute to renal injury through the production of autoantibodies, particularly IgG targeting the phospholipase A2 receptor (PLA2R) on podocytes, while T cells modulate immune responses that influence disease progression. Metabolic reprogramming alters lymphocyte survival, differentiation, proliferation, and function, potentially triggering autoimmune processes. Although the link between immune cell metabolism and MN remains underexplored, this review highlights recent advances in understanding immune metabolism and its role in MN. These insights may provide novel biomarkers and therapeutic strategies for MN treatment.

Effects of High Amylose-Resistant Starch on Gut Microbiota and Uremic Toxin Levels in Patients With Stage-G3a-G4 Chronic Kidney Disease: A Randomized Trial

OBJECTIVE

This study was designed to determine the effect of 16 weeks of supplementation with Hi-maize 260 resistant starch (RS) on the gut microbiota, uremic toxins (indoxyl sulfate and p-cresyl sulfate [PCS]), markers of inflammation, and oxidative stress along with vascular function in patients with stage G3a-G4 chronic kidney disease (CKD).

DESIGN AND METHODS

This was a double-blind, placebo-controlled, parallel-arm, randomized controlled trial. Sixty-eight patients with stage-G3a-G4 CKD were randomized to either RS with usual care or placebo and usual care. Patients attended four testing sessions as follows: two baseline (BL) visits and follow-up visits at 8 and 16 weeks. Fasting blood samples, resting brachial and central blood pressures, along with arterial stiffness, were collected at visits (1 or 2) and weeks 8 and 16. A stool sample was collected for analysis of microbial composition at BL and week 16. Patients were randomized after the BL visits.

RESULTS

Patients receiving the RS had a reduction in PCS at week 16. This reduction was associated with a decrease in microbial α-diversity between BL and week 16 (Chao1 P = .014, Shannon P = .017, phylogenetic diversity P = .046, and Simpson P = .017) as well as increases in Subdoligranulum (P = .03) and Oscillospiraceae Unclassified Clostridiales Group 002 (P = .02) and decreases in Bacteroides (P = .009).There were no changes in microbial beta diversity and other biomarkers or markers of vascular function following the 16-week period.

CONCLUSION

Sixteen weeks of supplementation of RS in patients with stage-G3a-G4 CKD led to changes in microbial composition that were associated with a significant reduction in PCS.

CKD patients comorbid with hypertension are associated with imbalanced gut microbiome

Intestinal flora has been linked to chronic kidney disease (CKD) and hypertension, respectively. This study aimed to investigate the microbial community among 54 individuals without CKD, 46 hypertensive CKD patients (CKD_HTN), and 48 non-hypertensive CKD patients. Variations in microbial diversity were detected in CKD. The Prevotella-dominated type progressively increased from CKD to CKD_HTN. Based on the variation patterns, we identified six distinct clusters. Klebsiella, Turicibacter, and Enterobacter were enriched in CKD, whereas Escherichia and Mogibacterium were elevated, and Blautia and Clostridium were reduced in CKD_HTN. Enhanced phenylalanine metabolism and siderophore group nonribosomal peptides biosynthesis from non-CKD to CKD were observed, particularly in CKD with hypertension. The connections between genera and KEGG pathways suggest an impact of microbial dysbiosis on metabolism. Our findings demonstrate that imbalances in gut microorganisms and functions are associated with increased susceptibility to hypertension in CKD patients and could be targeted for improving kidney function in CKD.

Theaflavin-3,3'-digallate (TF3) attenuated constipation by promoting gastrointestinal motility and modulating the gut microbiota: A comparative study of TF3 and the anti-constipation drug mosapride in mice

TF3 is a functional pigment formed during the process of black tea. This study aims to explore the anti-constipation effects of TF3 and compare its efficacy with the anti-constipation drug mosapride. Result showed that both TF3 and mosapride increased fecal water content and promoted gastrointestinal (GI) motility, but TF3 was more effective in restoring excitatory neurotransmitters like gastrin (Gas), motilin (MTL), and substance P (SP). TF3 uniquely altered the gut microbiota profile and restored the bacterial community at the phylum level. TF3 targeted specific bacteria such as Alloprevotella, Bacteroides, and Parabacteroides, while mosapride affected different bacterial groups. Significant changes in Bacteroides and Prevotellaceae UCG-001 were linked to constipation improvement. Importantly, TF3 did not synergize with mosapride in alleviating constipation. These findings highlight TF3's unique role in modulating gut microbiota to relieve constipation and suggest great potential to develop functional foods with anti-constipation properties using tea-derived polyphenols.

Relationship between dietary consumption of live microbes with mortality in adults with chronic kidney disease

BACKGROUND

The connection between gut dysbiosis and chronic kidney disease (CKD) has been recognized, but, the effect of dietary intake of live microbes on the prognosis of CKD is still unclear. This analysis examined the relationship of dietary live microbe intake with mortality among adults with CKD.

METHODS

For this study, information was gathered from the National Health and Nutrition Examination Survey 1999-2018, which included 8725 adult participants with CKD. MedHi refers to the live microbial content of food beyond 104 CFU/g. To elucidate the link between MedHi dietary live microbe intake and mortality from all-cause and cardiovascular disease (CVD), we implemented a weighted multivariate Cox regression analysis.

RESULTS

In contrast to survivors, non-survivors had a lower intake of dietary live microbes. The findings from the multivariable model indicated a negative and linear relationship between an increment of 100 g in MedHi foods and reduced mortality from all-causes and CVD. Likewise, participants in the highest MedHi food group exhibited a 20% and 26% decreased risk of all-cause and CVD mortality, respectively, compared to those in the lowest MedHi food group. Stratified analyses conducted on various subgroups yielded consistent findings.

CONCLUSION

A significant inverse linear relationship was found between high dietary live microbe consumption and reduced all-cause and CVD mortality.

Gut microbiota: A new key of understanding for Panax notoginseng against multiple disorders and biotransformation

ETHNOPHARMACOLOGICAL RELEVANCE

Panax notoginseng (Burkill) F.H.Chen(P. notoginseng) has been widely used as an herbal medicine for reducing swelling, relieving pain, promoting blood circulation and stopping bleeding, with notable therapeutic effects on obesity, liver diseases, colitis, Alzheimer's disease, chronic kidney disease and other diseases.

AIM OF THE STUDY

This review highlighted the close link and bidirectional effects between P. notoginseng and gut microbiota, with the ultimate aim of providing new insights into the potential mechanisms of pharmacological effects of P. notoginseng in the treatment of different diseases and PNS transformation.

MATERIALS AND METHODS

By means of some reputable databases (PubMed, China National Knowledge Infrastructure (CNKI), Google Scholar, etc.), we screened the published articles related to P. notoginseng from 1998 to 2024, including original research, clinical trials and review on raw materials and chemical constituents of P. notoginseng. Then, we employed the keywords "gut microbiota", "intestinal microbiota", "gut biotransformation" and "intestinal" to exclude the articles that do not in line with our topic. Plant information was obtained from www.worldfloraonline.org using "Panax notoginseng (Burkill) F.H.Chen" as the keyword.

RESULTS

P. notoginseng elevated certain probiotics including Lactobacillus, Bifidobacterium and Akkermansia, while simultaneously reducing pathogenic bacteria such as Prevotellaceae, Enterococcus, Enterobacter and Helicobacter, to fight various diseases. Meanwhile, considering to the low oral bioavailability and degradable properties of Panax notoginseng saponin (PNS), gut microbiota converted it into protopanaxatriol(PPT) and protopanaxadiol(PPD) mainly through deglycosylation reactions to enhance the bioactivity.

CONCLUSION

Increasing evidences suggest that gut microbiota may play a vital role for P. notoginseng exerting on beneficial effects on the prevention and treatment of metabolic disorders, liver diseases, neurological diseases, chronic kidney diseases, vascular diseases, colitis, and other diseases, as well as for biotransformation of P. notoginseng.

Activation of gut metabolite ACSL4/LPCAT3 by microplastics in drinking water mediates ferroptosis via gut-kidney axis

The environmental pollutant Benzo[a]pyrene (BaP) is commonly found in the environment, with microplastics (MPs) acting as the primary carriers of BaP into living organisms, increasing its availability in the body. However, the specific pathways and mechanisms through which MPs carrying pollutants cause kidney damage are not fully understood. This study aimed to investigate the routes and mechanisms of kidney injury in mice to low concentrations of both MPs and BaP. The combination of polystyrene (PS) and BaP disrupted lipid metabolism in the kidneys, leading to a form of cell death known as ferroptosis. However, this effect was not observed in HK-2 cells in vitro, indicating a cell-specific response. Interestingly, in HIEC-6 cells, both PS and BaP directly induced ferroptosis. These findings confirm that exposure to both PS and BaP can disrupt metabolic homeostasis in the kidneys, contributing to kidney dysfunction and cell death.

Characteristics, pathogenic and therapeutic role of gut microbiota in immunoglobulin A nephropathy

Immunoglobulin A nephropathy (IgAN) is the most prevalent glomerulonephritis in the world, and it is one of the leading causes of end-stage kidney disease. It is now believed that the pathogenesis of IgAN is the mesangial deposition of immune complex containing galactose-deficient IgA1, resulting in glomerular injury. Current treatments for IgAN include supportive care and immunosuppressive therapy. A growing number of studies found that the gut microbiota in IgAN was dysregulated. Gut microbiota may be involved in the development and progression of IgAN through three main aspects: destruction of intestinal barrier, changes in metabolites and abnormal mucosal immunity. Interestingly, therapies by modulating the gut microbiota, such as fecal microbiota transplantation, antibiotic treatment, probiotic treatment, Chinese herbal medicine Zhen Wu Tang treatment, gluten-free diet, and hydroxychloroquine treatment, can improve IgAN. In this review, the alteration of gut microbiota in IgAN, potential pathogenic roles of gut microbiota on IgAN and potential approaches to treat IgAN by modulating the gut microbiota are summarized.

Navigating the microbial maze: unraveling the connection between gut microbiome and pediatric kidney and urinary tract disease

The gut microbiome is made up of trillions of bacteria, viruses, archaea, and microbes that play a significant role in the maintenance of normal physiology in humans. Recent research has highlighted the effects of the microbiome and its dysbiosis in the pathogenesis and maintenance of kidney disease, especially chronic kidney disease (CKD) and its associated cardiovascular disease. While studies have addressed the kidney-microbiome axis in adults, how dysbiosis may uniquely impact pediatric kidney disease patients is not well-established. This narrative review highlights all relevant studies focusing on the microbiome and pediatric kidney disease that were published between 7/2015 and 7/2023. This review highlights pediatric-specific considerations including growth and bone health as well as emphasizing the need for increased pediatric research. Understanding microbiome-kidney interactions may allow for novel, less invasive interventions such as dietary changes and the use of probiotics to improve preventive care and ameliorate long-term morbidity and mortality in this vulnerable population.

Nephropathy II Decoction Attenuates Renal Fibrosis via Regulating TLR4 and Gut Microbiota Along the Gut-Kidney Axis

Nephropathy II Decoction (NED) is a widely used Chinese medicinal formulation for managing chronic kidney disease (CKD). Despite its extensive application, the precise mechanisms underlying its therapeutic effects remain poorly understood. This study aims to elucidate the role of NED in attenuating renal fibrosis and to explore its impact on the gut-kidney axis. The principal constituents of NED were analyzed using ultra-performance LC-tandem mass spectrometry (UPLC-MS/MS). A bilateral renal ischemia-reperfusion injury (bIRI) model was employed to induce fibrosis. RT-qPCR was utilized to assess the expression of mRNA related to the toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) and nuclear factor-κB (NF-κB) signaling pathway. Western blotting analysis was performed to identify changes in renal fibrosis markers, TLR4/MyD88/NF-κB pathway proteins, and the colon proteins ZO-1 and Occludin-1. Serum levels of uremic toxins were quantified using enzyme-linked immunosorbent assay (ELISA), and 16S ribosomal RNA (rRNA) gene sequencing was conducted to explore changes in the gut microbiome of the mice. Our study demonstrated that mice in the NED group exhibited reduced serum creatinine, blood urea nitrogen, and urinary protein levels, alongside improvements in kidney damage and a decrease in renal fibrosis markers. In the bIRI group, TLR4/MyD88/NF-κB protein and mRNA levels, as well as intestinal tight junction proteins and enterogenic uremic toxins, were significantly reduced. NED treatment reversed these changes and modified the gut microbiota. Furthermore, fecal microbial transplantation (FMT) alleviated kidney damage and fibrosis in bIRI mice. In summary, NED ameliorates kidney injury and fibrosis by modulating the gut microbiota and may further attenuate fibrosis through the inhibition of TLR4 expression, thereby influencing the gut-kidney axis.

Recent status and trends of innate immunity and the gut-kidney aixs in IgAN: A systematic review and bibliometric analysis

BACKGROUND

There is a significant global demand for precise diagnosis and effective treatment of IgA nephropathy (IgAN), with innate immunity, particularly the complement system, exerting a profound influence on its pathogenesis. Additionally, the gut-kidney axis pathway is vital in the emergence and development of IgAN.

METHODS

We conducted a comprehensive search in the Web of Science database, spanning from January 1, 2000 to December 18, 2023. The gathered literature underwent a visual examination through CiteSpace, VOSviewer, and Scimago Graphica to delve into authors, nations, organizations, key terms, and other pertinent elements.

RESULT

Between 2000 and 2023, a total of 720 publications were identified, out of which 436 publications underwent screening for highly relevant literature analysis. The average annual number of articles focusing on IgAN, innate immunity, and the gut-kidney axis is approximately 31, with an upward trend observed. In terms of research impact encompassing publication count and authorship, the United States emerged as the leading contributor. Prominent keywords included "complement", "activation", "microbe", "gut-kidney axis", "C4d deposition", "alternative pathway" and "B cells" along with other prospective hot topics.

CONCLUSION

The correlation between IgAN and innate immunity is a focal point in current scientific research. Recent literature underscores the significance of the gut-kidney axis, where intestinal microorganisms and metabolites may influence IgAN. The complement system, a key component of innate immunity, also has a crucial function.Advancements in prevention, diagnosis, and treatment hinge on unraveling this intricate relationship.

Probiotic interventions in peritoneal dialysis: A review of underlying mechanisms and therapeutic potentials

Peritoneal dialysis (PD) is a commonly used modality for kidney replacement therapy for patients with end-stage kidney disease (ESKD). PD offers many benefits, including home-based care, greater flexibility, and preservation of residual kidney function compared to in-center hemodialysis. Nonetheless, patients undergoing PD often face significant challenges, including systemic inflammation, PD-related peritonitis, metabolic disorders, and cardiovascular issues that can negatively affect their quality of life and treatment outcomes. Recent studies have demonstrated the crucial role of the gut microbiome in overall health and treatment results, supporting the hypothesis that probiotics may bring potential benefits to the general population of ESKD patients. However, specific data on probiotic use in PD patients are limited. This opinion review aims to summarize the current knowledge on the relationship between PD and the gut microbiome and offers a novel perspective by specifically exploring how probiotic interventions could improve the outcomes of PD treatment. The review also outlines some clinical data supporting the effectiveness of probiotics in patients undergoing PD and considers the difficulties and restrictions in their application. Based on the current knowledge gaps, this study seeks to explore future research directions and their implications for clinical practice.

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

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

Research progress on the association between TMAO and vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) is a common complication in patients with chronic kidney disease (CKD) and a major risk factor for increased cardiovascular mortality in patients with CKD. Its pathology and pathogenesis are complex and have not been fully elucidated. Trimethylamine N-oxide (TMAO) is an enteric-borne uremic toxin that has been found to play a role in the progression of VC. This article mainly reviews the metabolism of TMAO, the relationship between TMAO and VC in CKD patients, and possible treatments for TMAO, aiming to further explore the mechanism of VC occurrence in CKD patients and provide potential diagnostic and treatment strategies.

The potential mediating role of the gut microbiome and metabolites in the association between PFAS and kidney function in young adults: A proof-of-concept study

BACKGROUND

Chronic kidney disease (CKD) affects over 10 % of the global population and can lead to kidney failure and death. Exposure to per- and polyfluoroalkyl substances (PFAS) is associated with increased risk of CKD, yet studies examining the mechanisms linking PFAS and kidney function are lacking. In this exploratory study, we examined longitudinal associations of PFAS exposure with kidney function, and tested if associations were mediated by altered gut bacterial taxa or plasma metabolites using a multi-omics mediation analysis.

METHODS

Seventy-eight young adults from the Children's Health Study were included in this longitudinal cohort study. At baseline, seven plasma PFAS and untargeted plasma metabolomics were measured using liquid chromatography/mass-spectrometry. Baseline gut bacterial abundance was characterized using 16S rRNA sequencing and examined at the genus level. At follow-up, serum creatinine and cystatin-C concentrations were quantified to estimate glomerular filtration rate (eGFR). High-dimensional multi-omics analyses were conducted to assess the association between baseline PFAS exposure with follow-up eGFR, mediated by gut microbiome and circulating metabolite levels.

RESULTS

PFAS burden score, a variable developed to estimate exposure to chemical mixtures, was associated with kidney function. Each standard deviation increase in baseline PFAS burden score was associated with a 2.4 % lower eGFR at follow-up (95 % CI:[0.1 %,4.8 %]). Following high-dimensional mediation analyses with the microbiome and circulating metabolites, a joint component (characterized by reduced Lachnospiraceae and 17b-estradiol and increased succinate, retinoate and dodecanoic acid) and a metabolite component (characterized by increased hypotaurine and decreased D-pinitol and ureidopropionate) mediated 38 % and 50 % of the effect between PFAS burden score and eGFR, respectively.

CONCLUSION

Our proof-of-concept analysis provides the first evidence that reduced short-chain fatty acid-producing bacteria and anti-inflammatory metabolites may link PFAS exposure with impaired kidney function. This study raises the possibility of future targeted interventions that can alter gut microbiome or circulating metabolite profiles to prevent PFAS induced kidney damage.

Chronic exposure to polystyrene microplastics induces renal fibrosis via ferroptosis

With the increasing prevalence of microplastics (MPs) in the environment, human health has become a growing concern. After entering the human body, MPs accumulate in the kidneys, indicating that the kidneys are their major target organs. This study investigated nephrotoxicity associated with MPs, with a specific focus on polystyrene (PS) MPs and amino-functionalized polystyrene (PS-NH2) MPs. Although previous studies have documented the nephrotoxic effects associated with short-term exposure to MPs, the mechanisms of kidney toxicity caused by chronic long-term exposure to MPs remain largely unclear. In animal models, mice were exposed to MPs (10 mg/L) at concentrations that are accessible to humans, administered via drinking water over a period of six months. These findings indicate that MPs can induce renal fibrosis by facilitating the onset of inflammation and accumulation of a substantial number of inflammatory cells. Our in vitro study showed that long-term exposure to MPs (60 μg/mL) induced ferroptosis in renal tubular epithelial cells via ferritinophagy and secreted TGF-β1, leading to renal fibroblast activation. Conversely, the application of Fer-1, a ferroptosis inhibitor, prevents ferroptosis in renal epithelial cells and reverses the activation of renal fibroblasts. Our study identified a novel toxicity mechanism for renal fibrosis induced by MPs exposure, offering new insights into the detrimental effects of environmental MPs on human health.

Identification of serum biomarkers for chronic kidney disease using serum metabolomics

This study aimed to identify biomarkers for chronic kidney disease (CKD) by studying serum metabolomics. Serum samples were collected from 194 non-dialysis CKD patients and 317 healthy controls (HC). Using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS), untargeted metabolomics analysis was conducted. A random forest model was developed and validated in separate sets of HC and CKD patients. The serum metabolomic profiles of patients with chronic kidney disease (CKD) exhibited significant differences compared to healthy controls (HC). A total of 314 metabolites were identified as significantly different, with 179 being upregulated and 135 being downregulated in CKD patients. KEGG enrichment analysis revealed several key pathways, including arginine biosynthesis, phenylalanine metabolism, linoleic acid metabolism, and purine metabolism. The diagnostic efficacy of the classifier was high, with an area under the curve of 1 in the training and validation sets and 0.9435 in the cross-validation set. This study provides comprehensive insights into serum metabolism in non-dialysis CKD patients, highlighting the potential involvement of abnormal biological metabolism in CKD pathogenesis. Exploring metabolites may offer new possibilities for the management of CKD.

Suyin Detoxification Granule alleviates trimethylamine N-oxide-induced tubular ferroptosis and renal fibrosis to prevent chronic kidney disease progression

BACKGROUND

Trimethylamine N-oxide (TMAO), a gut microbiota metabolite, is a risk factor for chronic kidney disease (CKD) progression. Suyin Detoxification Granule (SDG) is a traditional Chinese medicine preparation that has been proven to significantly reduce renal function damage and serum TMAO levels in patients with CKD. However, its specific mechanism remains unclear.

PURPOSE

This study investigated the role of TMAO-induced ferroptosis in CKD, and further explored the mechanism of SDG in improving TMAO-induced kidney injury.

METHODS

A TMAO renal tubular epithelial cell injury model was constructed in vitro. After using freeze-dried powder of Suyin Detoxification Prescription (SDP), proteomic analysis, Western blotting, ferroptosis phenotype-related detection, and ELISA were performed to explore its mechanism. In vivo, a adenine-induced CKD model was established, with or without a high-choline diet to observe the impact of TMAO on CKD, and SDG or 3,3-Dimethyl-1-butanol (DMB, a TMAO inhibitor) was used for intervention. The composition of gut microbiota was analyzed using 16SrRNA sequencing, and the effect of SDG on gut-derived TMAO-induced kidney injury under the background of CKD was evaluated by pathological staining, immunoblotting, immunohistochemistry, and fluorescence staining.

RESULTS

In vitro, TMAO could induce ferroptosis and secrete profibrotic factors in NRK-52E cells. SDP could inhibit TMAO-induced ferroptosis and reduce the secretion of profibrotic factors. The amelioration of ferroptosis by SDP was also verified in RSL3-induced cells. In vivo, our results demonstrated that gut-derived TMAO could promote CKD progression by inducing tubular ferroptosis, profibrotic factors expression and renal fibrosis. In addition, we illustrated that SDG might reduce circulating TMAO levels by down-regulating the gut microbiota related to TMAO (including Muribaculaceae, Bacteroides and Ruminococcaceae_UCG-010). Furthermore, SDG could prevent CKD progression by reducing TMAO-induced renal damage.

CONCLUSION

SDG reduced circulating TMAO levels by regulating gut microbiota and inhibited TMAO-induced renal tubular ferroptosis, profibrotic factors secretion, and renal fibrosis to prevent CKD progression.

Traditional Chinese medicine improved diabetic kidney disease through targeting gut microbiota

CONTEXT

Diabetic kidney disease (DKD) affects nearly 40% of diabetic patients, often leading to end-stage renal disease that requires renal replacement therapies, such as dialysis and transplantation. The gut microbiota, an integral aspect of human evolution, plays a crucial role in this condition. Traditional Chinese medicine (TCM) has shown promising outcomes in ameliorating DKD by addressing the gut microbiota.

OBJECTIVE

This review elucidates the modifications in gut microbiota observed in DKD and explores the impact of TCM interventions on correcting microbial dysregulation.

METHODS

We searched relevant articles from databases including Web of Science, PubMed, ScienceDirect, Wiley, and Springer Nature. The following keywords were used: diabetic kidney disease, diabetic nephropathy, gut microbiota, natural product, TCM, Chinese herbal medicine, and Chinese medicinal herbs. Rigorous criteria were applied to identify high-quality studies on TCM interventions against DKD.

RESULTS

Dysregulation of the gut microbiota, including Lactobacillus, Streptococcus, and Clostridium, has been observed in individuals with DKD. Key indicators of microbial dysregulation include increased uremic solutes and decreased short-chain fatty acids. Various TCM therapies, such as formulas, tablets, granules, capsules, and decoctions, exhibit unique advantages in regulating the disordered microbiota to treat DKD.

CONCLUSION

This review highlights the importance of targeting the gut-kidney axis to regulate microbial disorders, their metabolites, and associated signaling pathways in DKD. The Qing-Re-Xiao-Zheng formula, the Shenyan Kangfu tablet, the Huangkui capsule, and the Bekhogainsam decoction are potential candidates to address the gut-kidney axis. TCM interventions offer a significant therapeutic approach by targeting microbial dysregulation in patients with DKD.

Alterations in the gut microbiome and metabolism profiles reveal the possible molecular mechanism of renal injury induced by hyperuricemia in a mouse model of renal insufficiency

Objectives: To investigate the role of the intestinal flora and metabolites in the development of hyperuricemic renal injury in chronic kidney disease (CKD).Methods: Unilaterally nephrectomized mice were fed with adenine and potassium oxonate for 9 weeks. HE staining combined with plasma biochemical indicators was used to evaluate renal pathological and functional changes. We conducted 16S rRNA sequencing and untargeted metabolomics on feces and plasma samples to reveale changes in intestinal microbiota and metabolites.Result: Our analysis revealed significant differences in 15 bacterial genera, with 7 being upregulated and 8 being downregulated. Furthermore, metabolomic analysis revealed changes in the distribution of amino acid and biotin metabolites in basic metabolic pathways in both feces and serum. Specifically, differentially abundant metabolites in feces were associated primarily with histidine metabolism; the biosynthesis of phenylalanine, tyrosine, and tryptophan; and tyrosine metabolism. In plasma, the differentially abundant metabolites were involved in multiple metabolic pathways, including aminoacyl-tRNA biosynthesis; glycine, serine, and threonine amino acid metabolism; valine, leucine, and isoleucine biosynthesis; tyrosine biosynthesis and metabolism; biotin metabolism; and taurine and hypotaurine metabolism. Furthermore, correlation analysis revealed that Akkermansia, UCG-005, Lachnospiraceae_NK4A136_group, Lactococcus, and Butymonas were associated with various differentially abundant metabolites as well as renal function, oxidative stress, and mitophagy. The changes in the intestinal flora observed in hyperuricemia may lead to imbalances in amino acid and biotin metabolism in both the intestine and host, ultimately affecting oxidative stress and mitophagy in mice and accelerating the progression of CKD.Conclusion: Our findings provide insights into a potential pathogenic mechanism by which hyperuricemia exacerbates renal injury in mice with renal insufficiency. Understanding these pathways may offer new therapeutic strategies for managing hyperuricemic renal injury in CKD patients.

Gut microbiota and renal fibrosis

Renal fibrosis represents a critical pathological condition in the progression of renal dysfunction, characterized by aberrant accumulation of extracellular matrix (ECM) and structural alterations in renal tissue. Recent research has highlighted the potential significance of gut microbiota and demonstrated their influence on host health and disease mechanisms through the production of bioactive metabolites. This review examines the role of alterations in gut microbial composition and their metabolites in the pathophysiological processes underlying renal fibrosis. It delineates current therapeutic interventions aimed at modulating gut microbiota composition, encompassing dietary modifications, pharmacological approaches, and probiotic supplementation, while evaluating their efficacy in mitigating renal fibrosis. Through a comprehensive analysis of current research findings, this review enhances our understanding of the bidirectional interaction between gut microbiota and renal fibrosis, establishing a theoretical foundation for future research directions and potential clinical applications in this domain.

Risk factor assessment and microbiome analysis in peritoneal dialysis-related peritonitis reveal etiological characteristics

Background

Peritoneal dialysis-related peritonitis (PDRP) is one of the most common complications of peritoneal dialysis (PD). Understanding the risk factors and etiological characteristics is indispensable for infection prevention and improving the outcome and life quality.

Methods

A total of 70 PD patients were separated into the PDRP group (n=25) and the control group (n=45). Variables, including gender, age, body mass index, primary diseases, and history of basic diseases, in the two groups were analyzed to assess the risk factors of PDRP. Metagenomic next-generation sequencing (mNGS) and microbial culture were compared in detecting pathogenic microorganisms. Gut microbiota analysis was performed in 35 PDRP patients based on mNGS data.

Results

Dialysis time and times of dialysate change were the risk factors of PDRP, and times of dialysate change was the independent risk factor of PDRP (p = 0.046). mNGS produced higher sensitivity (65.79%) than microbial culture (36.84%) in identifying pathogenic microorganisms. Staphylococcus aureus and Klebsiella pneumoniae (four cases) were the most frequent pathogens causing PDRP, followed by Staphylococcus capitis (three cases). β diversity of the gut microbiota was significantly different between patients with fewer times of dialysate change (≤4) and more (>5), as well as between patients with gram-positive (G+) bacterial and gram-negative (G-) bacterial infection.

Conclusion

The dialysis time and times of dialysate changes not only are risk factors for peritonitis in PD patients but also stimulate significant changes in the gut microbiome structure in PDRP patients. These findings may provide a novel viewpoint for the management of patients with PDRP.

Comparative analysis of gut microbiota in incident and prevalent peritoneal dialysis patients with peritoneal fibrosis, correlations with peritoneal equilibration test data in the peritoneal fibrosis cohort

INTRODUCTION

The connection between peritoneal function and gut microbiota in peritoneal fibrosis (PF) patients remains uncertain.

METHODS

Peritoneal equilibration test (PET) was employed to evaluate peritoneal function in patients with peritoneal fibrosis (PF). 16S rRNA sequencing was used to analyze the gut flora in incident peritoneal dialysis (PD) and PF groups, identifying differential microbial communities. Spearman's correlation analysis, conducted using SPSS 26.0, was employed to explore the microbial associations with PF.

RESULTS

In the PF group, the PET showed a 4-h dialysate-to-plasma creatinine ratio (D/PCr) ratio of 0.62 ± 1.01 and a 4-h ultrafiltration (UF) volume of 41.73 ± 76.71 mL with a 2.5% glucose dwell. The alpha diversity between the PD and PF groups did not exhibit a significant difference. The PD and PF groups were predominantly composed of Firmicutes, Tenericutes, and Ignavibacteriae. Linear discriminant analysis effect size (LEfse) analysis indicates that the Firmicutes, Lactobacillales, and Bacilli were significantly enriched in the PD group, whereas Lachnospiraceae, Phenylobacterium, and Caulobacteraceae were enriched among the PF group. The functional prediction of gut microbiota genes revealed variations in metabolic pathways related to lipid transport, energy metabolism, and post-translational protein modifications between the two cohorts. In the PF group, Ignavibacteriae and Bdellovibrio correlated positively with the 4-h D/PCr ratio (p <0.05), while Prevotella negatively correlated with the 4-h UF from 2.5% glucose dwell (p <0.05).

CONCLUSION

The intestinal microbiota of patients newly initiated on peritoneal dialysis significantly differs from that of those with long-term peritoneal dialysis complicated by peritoneal fibrosis, with the latter's peritoneal function potentially linked to Prevotella, Ignavibacteriae, and Bdellovibrio.

Fecal bile acid dysmetabolism and reduced ursodeoxycholic acid correlate with novel microbial signatures in feline chronic kidney disease

Background

Microbial-derived secondary bile acids (SBAs) are reabsorbed and sensed via host receptors modulating cellular inflammation and fibrosis. Feline chronic kidney disease (CKD) occurs with progressive renal inflammation and fibrosis, mirroring the disease pathophysiology of human CKD patients.

Methods

Prospective cross-sectional study compared healthy cats (n = 6) with CKD (IRIS Stage 2 n = 17, Stage 3 or 4 n = 11). Single timepoint fecal samples from all cats underwent targeted bile acid metabolomics. 16S rRNA gene amplicon sequencing using DADA2 with SILVA taxonomy characterized the fecal microbiota.

Results

CKD cats had significantly reduced fecal concentrations (median 12.8 ng/mg, Mann-Whitney p = 0.0127) of the SBA ursodeoxycholic acid (UDCA) compared to healthy cats (median 39.4 ng/mg). Bile acid dysmetabolism characterized by <50% SBAs was present in 8/28 CKD and 0/6 healthy cats. Beta diversity significantly differed between cats with <50% SBAs and > 50% SBAs (PERMANOVA p < 0.0001). Twenty-six amplicon sequence variants (ASVs) with >97% nucleotide identity to Peptacetobacter hiranonis were identified. P. hiranonis combined relative abundance was significantly reduced (median 2.1%) in CKD cats with <50% SBAs compared to CKD cats with >50% SBAs (median 13.9%, adjusted p = 0.0002) and healthy cats with >50% SBAs (median 15.5%, adjusted p = 0.0112). P. hiranonis combined relative abundance was significantly positively correlated with the SBAs deoxycholic acid (Spearman r = 0.5218, adjusted p = 0.0407) and lithocholic acid (Spearman r = 0.5615, adjusted p = 0.0156). Three Oscillospirales ASVs and a Roseburia ASV were also identified as significantly correlated with fecal SBAs.

Clinical and translational importance

The gut-kidney axis mediated through microbial-derived SBAs appears relevant to the spontaneous animal CKD model of domestic cats. This includes reduced fecal concentrations of the microbial-derived SBA UDCA, known to regulate inflammation and fibrosis and be reno-protective. Microbes correlated with fecal SBAs include bai operon containing P. hiranonis, as well as members of Oscillospirales, which also harbor a functional bai operon. Ultimately, CKD cats represent a translational opportunity to study the role of SBAs in the gut-kidney axis, including the potential to identify novel microbial-directed therapeutics to mitigate CKD pathogenesis in veterinary patients and humans alike.

Integrated gut microbiota and serum metabolomics reveal the protective effect of oleanolic acid on liver and kidney-injured rats induced by Euphorbia pekinensis

Euphorbia pekinensis (EP) is a commonly used Chinese medicine treating edema with potential hepatorenal toxicity. However, its toxic mechanism and prevention are remained to be explored. Oleanolic acid (OA) is a triterpene acid with potential hepatorenal protective activities. We investigated the protective effect and potential mechanism of OA on EP-induced hepatorenal toxicity. In this study, rats were given total diterpenes from EP (TDEP, 16 mg/kg) combined with OA (10, 20, 40 mg/kg) by gavage for 4 weeks. The results showed that TDEP administration could lead to a 3-4-fold increasement in hepatorenal biochemical parameters with histopathological injuries, while OA treatment could ameliorate them in a dose-dependent manner. At microbial and metabolic levels, intestinal flora and host metabolism were perturbed after TDEP administration. The disturbance of bile acid metabolism was the most significant metabolic pathway, with secondary bile acids increasing while conjugated bile acids decreased. OA treatment can improve the disorder of intestinal flora and metabolic bile acid spectrum. Further correlation analysis screened out that Escherichia-Shigella, Phascolarctobacterium, Acetatifactor, and Akkermansia were closely related to the bile acid metabolic disorder. In conclusion, oleanolic acid could prevent hepatorenal toxicity induced by EP by regulating bile acids metabolic disorder via intestinal flora improvement.

Peritoneal dialysis promotes microbial-driven biosynthesis pathways of sesquiterpenes and triterpenes compounds in end-stage renal disease patients

The concept of the gut-kidney axis is gaining significant attention due to the close relationship between gut microbiota and kidney disease. Peritoneal dialysis is recognized as a crucial renal replacement therapy for end-stage renal disease (ESRD). The alterations in gut microbiota and related mechanisms after receiving this dialysis method are not fully understood. This study conducted shotgun metagenomic sequencing on fecal samples from 11 end-stage renal disease patients who did not receive dialysis (ESRD_N) and 7 patients who received peritoneal dialysis (ESRD_P). After quality control and correlation analysis of the data, our study is aimed at exploring the impact of peritoneal dialysis on the gut microbiota and health of ESRD patients. Our research findings indicate that the complexity and aggregation characteristics of gut microbiota interactions increase in ESRD_P. In addition, the gut microbiota drives the biosynthesis pathways of sesquiterpenes and triterpenes in ESRD_P patients, which may contribute to blood purification and improve circulation. Therefore, our research will lay the foundation for the prevention and treatment of ESRD.

LPS-related muscle loss is associated with the alteration of Bacteroidetes abundance, systemic inflammation, and mitochondrial morphology in a weaned piglet model

We previously demonstrated that lipopolysaccharide (LPS) injection-induced immune stress could impair muscle growth in weaned piglets, but the precise mechanisms behind this remain elusive. Here, we found that chronic immune stress induced by LPS resulted in a significant reduction of 36.86% in the total muscle mass of piglets at 5 d post-treatment compared with the control group. At 1 d, prior to muscle mass loss, multiple alterations were noted in response to LPS treatment. These included a reduction in the abundance of Bacteroidetes, an increase in serum concentrations of pro-inflammatory cytokines, compromised mitochondrial morphology, and an upregulation in the expression of dynamin-related protein 1 (Drp1), a critical protein involved in mitochondrial fission. We highlight a strong negative correlation between Bacteroidetes abundance and the levels of serum pro-inflammatory cytokines, corroborated by in vivo intervention strategies in the musculature of both pig and mouse models. Mechanistically, the effects of Bacteroidetes on inflammation and muscle mass loss may involve the signaling pathway of the tauro-β-muricholic acid-fibroblast growth factor 15. Furthermore, the induction of overexpression of inflammatory cytokines, achieved without LPS treatment through oral administration of recombinant human IL-6 (rhIL-6), led to increased levels of circulating cytokines, subsequently causing a decrease in muscle mass. Notably, pre-treatment with Mdivi-1, an inhibitor of Drp-1, markedly attenuated the LPS-induced elevation in reactive oxygen species levels and rescued the associated decline in muscle mass. Collectively, these data indicate that LPS-induced muscle mass loss was linked to the reduction of Bacteroidetes abundance, increased inflammation, and the disruption of mitochondrial morphology. These insights offer promising avenues for the identification of potential therapeutic targets aimed at mitigating muscle mass loss.

Elucidating the genetic relationship between ulcerative colitis and diabetic kidney disease: a bidirectional Mendelian randomization study

Introduction

Ulcerative colitis (UC) and diabetic kidney disease (DKD) are chronic disorders with multifaceted pathogenesis, posing significant challenges in clinical management. While substantial efforts have been made to investigate the individual causes of these diseases, the interplay between UC and DKD is not well understood. This study aims to elucidate the genetic association between UC and DKD through Mendelian randomization (MR) analysis, offering new insights into common biological pathways and potential clinical implications.

Methods

We conducted a bidirectional two-sample MR study utilizing data from large-scale genome-wide association studies (GWAS) for both UC and DKD. Instrumental variables (IVs) were meticulously selected according to genome-wide significance and stringent statistical criteria, ensuring robust causal inference. Various MR methodologies, including inverse variance weighting (IVW), were employed to assess the causal relationships between UC and DKD. Sensitivity analyses were also performed to validate the robustness of our findings.

Results

Our analysis revealed a significant causal relationship between genetic predisposition to UC and increased susceptibility to DKD. Specifically, individuals with a genetic susceptibility to UC exhibited a 17.3% higher risk of developing DKD. However, we found no evidence of a causal link between DKD and the risk of developing UC. Additionally, we identified shared genetic risk factors and molecular pathways linking UC and DKD, thereby highlighting potential therapeutic targets.

Discussion

This study underscores the intricate genetic interplay between UC and DKD, suggesting that individuals with UC may be at an elevated risk for developing DKD. Understanding these shared genetic pathways could facilitate the development of early detection strategies and targeted interventions for individuals at risk of DKD. Ultimately, these insights could lead to improved clinical outcomes for patients suffering from both conditions.

TMAO is involved in kidney-yang deficiency syndrome diarrhea by mediating the "gut-kidney axis"

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a harmful metabolite dependent on the intestinal microbiota and excreted through the kidneys. According to numerous investigations, rich circulation concentrations of TMAO have been linked to kidney and gastrointestinal disorders. Through the "gut-kidney axis" mediated by TMAO, this research attempted to clarify the microbiological causes of kidney-yang deficiency syndrome diarrhea.

METHODS

Adenine and Folium Sennae were used to create a mouse model of kidney-yang deficiency syndrome diarrhea. 16S rRNA sequencing was used to identify the traits of the intestinal mucosal microbiota. ELISA was used to assess TMAO, transforming growth factor-β1 (TGF-β1), interleukin-1β (IL-1β), and NOD-like receptor thermal protein domain associated protein 3 (NLRP3). Kidney tissue fibrosis was evaluated using Masson's trichrome staining, and immunohistochemical labeling was used to investigate the protein expression of occludin and Zonula Occludens-1(ZO-1) in small intestine tissue. Microbial activity was determined by using fluorescein diacetate (FDA) hydrolysis spectrophotometry.

RESULTS

TMAO showed a positive correlation with NLRP3, IL-1β and TGF-β1, all of which exhibited substantial increases (P < 0.05). Significant renal fibrosis and decreased ZO-1 and occludin expression in small intestine tissues were detected in the model group. The sequencing results revealed alterations in both α and β diversities of small intestinal mucosal microbiota. Elevated TMAO concentrations were potentially associated with increasing Firmicutes/Bacteroidota (F/B) ratios, Streptococcus, Pseudomonas and unclassified Clostridia UCG 014, but with decreasing Rothia and RB41 abundances.

CONCLUSION

This study establishes a link between intestinal microbiota dysbiosis and elevated TMAO concentrations. TMAO can activate inflammatory responses and cytokines, contributing to kidney-yang deficiency syndrome diarrhea via the "gut-kidney axis". Moreover, TMAO may coincide with disruptions in the intestinal barrier and renal fibrosis. Dysfunction of the "gut-kidney axis" further elevates TMAO levels, perpetuating a vicious cycle.

Microbial and Metabolic Profiling of Obese and Lean Luchuan Pigs: Implications for Phenotypic Divergence

Luchuan (LC) pigs are a Chinese breed renowned for their distinctive black and white coloring, superior meat quality and rapid reproduction, but their growth rate is slow. Over the course of approximately two decades of controlled breeding, the LC pigs maintained at the Shanghai Academy of Agricultural Sciences (Shanghai, China) have diverged into two phenotypes: one characterized by obesity (FLC) and the other by leanness (LLC). Recent studies indicate a correlation between microorganisms and the differentiation of host phenotypes. In this study, we examined the fecal microbiota profiles and serum metabolites of FLC and LLC pigs. The body weight, chest circumference, and alanine aminotransferase and aspartate aminotransferase enzyme activities were increased in the FLC pigs compared to the LLC pigs. Conversely, the levels of the Fusobacterium and Streptococcus genera were lower in the FLC pigs, while the number of Firmicutes, Lactobacillus, Phascolartobacterium, and Rikenellaceae_RC9_gut_group members were higher. A total of 52 metabolites were altered between the two groups, with many playing crucial roles in prolactin signaling, oocyte meiosis, and aldosterone-regulated sodium reabsorption pathways. The correlation analyses demonstrated a significant association between the modified microbiota and metabolites and the phenotypic variations observed in the LC pigs. Specifically, Jeotgalicoccus was positively correlated with the body weight and chest circumference, but was negatively correlated with metabolites such as 2-mercaptobenzothiazole and N1-pyrazin-2-yl-4-chlorobenzamide, which were positively associated with Bacteroides. These results provide compelling evidence for a novel relationship between the gut microbiome and metabolome in the phenotypic differentiation of LC pigs.