Multiple techniques collectively reveal the attenuation of kidney injury by trimethylamine N ‐oxide (TMAO) production manipulation

The microbiome-derived metabolite trimethylamine N-oxide is associated with chronic kidney disease risk

Previous studies have established a correlation between the microbiome-derived metabolite trimethylamine N-oxide (TMAO) and decreased renal function, but with great heterogeneity. Moreover, population-based evidence remains scarce, particularly in Chinese populations. We designed a meta-analysis and a population-based cross-sectional study in China to examine the associations between TMAO and chronic kidney disease (CKD). In meta-analysis, among 2125 pooled subjects with 1240 controls and 885 CKD patients, a significant association was observed between TMAO and CKD, with a standardized mean difference of - 0.93 (95% confidence interval: - 1.11, - 0.75). Meta-regression analysis identified gender, age, and body mass index (BMI) as significant heterogeneity factors. In our population-based study of 5584 subjects with an estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2 from Sijing community, 100 developed CKD in 2 years. We matched 195 controls by age and gender from the 5484 non-CKD subjects. Male subjects and alcohol consumers exhibited a lower risk of CKD with adjusted odds ratio (OR) of 0.471 (P < 0.05) and 0.320 (P < 0.05), respectively. When comparing subjects in the lowest tertile of TMAO, adjusted OR reached to 1.243 (P > 0.05) for those in the middle and 2.123 (P < 0.05) in the highest tertile (P for trend < 0.05). TMAO demonstrated a moderate capacity to distinguish CKD from non-CKD subjects (AUC = 0.614, P < 0.01). Our findings indicate TMAO is significantly associated with the risk of CKD, and suggest age, gender, and BMI may confound the relationship between TMAO and CKD. KEY POINTS: • Subjects with elevated TMAO levels have an increased risk of CKD. • TMAO demonstrates a moderate capacity to distinguish CKD from non-CKD cases. • Age, gender and BMI may confound the relationship between TMAO and CKD.

Gut microbiota regulates oxidative stress and inflammation: a double-edged sword in renal fibrosis

Gut microbiota is a complex and dynamic system that plays critical roles in human health and various disease. Progressive chronic kidney disease (CKD) suggests that patients irreversibly progress to end-stage kidney disease and need renal replacement treatments, including dialysis and transplantation. Ample evidence indicates that local oxidative stress and inflammation play pivotal roles in the pathogenesis and progression of CKD and dysbiosis of gut microbiota. CKD is always accompanied by intestinal inflammation and oxidative stress, which lead to rapid systemic translocation of bacterial-derived uraemic toxins, including indoxyl sulphate, phenyl sulphate and indole-3-acetic acid, and the consequent development and aggravation of renal fibrosis. Although inflammation and oxidative stress have been extensively discussed, there is a paucity of reports on the effects of gut microbiota on renal fibrosis and gut microbiota mediation of oxidative stress and inflammation. This review provides an overview of gut microbiota on inflammation and oxidative stress in renal fibrosis, briefly discusses regulation of the gut flora using microecological preparations and natural products, such as resveratrol, curcumin and emodin as treatments for CKD, and provides a clear pathophysiological rationale for the design of promising therapeutic strategies.

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.

Metabolomics reveals soluble epoxide hydrolase as a therapeutic target for high-sucrose diet-mediated gut barrier dysfunction

Highsucrose diet (HSD) was reported as a causative factor for multiorgan injuries. The underlying mechanisms and therapeutic strategies remain largely uncharted. In the present study, by using a metabolomics approach, we identified the soluble epoxide hydrolase (sEH) as a therapeutic target for HSD-mediated gut barrier dysfunction. Specifically, 16-week feeding on an HSD caused gut barrier dysfunction, such as colon inflammation and tight junction impairment in a murine model. A metabolomics analysis of mouse colon tissue showed a decrease in the 5(6)-epoxyeicosatrienoic acid [5(6)-EET] level and an increase in soluble epoxide hydrolase, which is related to HSD-mediated injuries to the gut barrier. The mice treated with a chemical inhibitor of sEH and the mice with genetic intervention by intestinal-specific knockout of the sEH gene significantly attenuated HSD-caused intestinal injuries by reducing HSD-mediated colon inflammation and improving the impaired tight junction caused by an HSD. Further, in vitro studies showed that treatment with 5(6)-EET, but not its hydrolytic product 5,6-dihydroxyeicosatrienoic acid (5,6-DiHET), significantly ablated high sucrose-caused intestinal epithelial inflammation and impaired tight junction. Additionally, 5(6)-EET is anti-inflammatory and improves gut epithelial tight junction while 5,6-DiHET cannot do so. This study presents an underlying mechanism of and a therapeutic strategy for the gut barrier dysfunction caused by an HSD.

Gut-derived trimethylamine N-oxide promotes CCR2-mediated macrophage infiltration in acute kidney injury

BACKGROUND

Inflammation is crucial in the development of acute kidney injury (AKI) and subsequent chronic kidney disease (CKD) following renal ischaemia-reperfusion (IR) injury. Gut microbiota metabolites trigger inflammation and affect IR-induced renal damage. Yet the driving factors and mechanisms are unclear. Trimethylamine N-oxide (TMAO), a gut-derived choline metabolite, is a strong pro-inflammatory factor that increases in patients with AKI and CKD. We hypothesized that TMAO can promote renal injury caused by IR.

METHODS

Mice subjected to unilateral renal IR to induce AKI and CKD were fed a high-choline diet to observe the effects of TMAO on kidney inflammation, fibrosis and macrophage dynamics.

RESULTS

A choline-rich diet altered the gut microbiota and elevated TMAO levels, exacerbating IR-induced AKI and subsequent CKD. Single-cell analysis identified a distinct subset of CCR2+ macrophages derived from monocytes as key responders to TMAO, intensifying immune cell interactions and worsening renal injury. TMAO promoted sustained CCR2 expression after IR, increasing macrophage infiltration. CCR2 deletion and antagonist RS-102895 improved TMAO-induced inflammation and fibrosis and alleviated renal injury induced by IR.

CONCLUSIONS

Our study provides valuable insights into the link between TMAO and IR-induced renal inflammation and fibrosis, emphasizing the critical role of TMAO-mediated macrophage infiltration via CCR2 as a key therapeutic target in the acute and chronic phases after IR.

The gut microbiota derived metabolite trimethylamine N-oxide: Its important role in cancer and other diseases

An expanding body of research indicates a correlation between the gut microbiota and various diseases. Metabolites produced by the gut microbiota act as mediators between the gut microbiota and the host, interacting with multiple systems in the human body to regulate physiological or pathological functions. However, further investigation is still required to elucidate the underlying mechanisms. One such metabolite involved in choline metabolism by gut microbes is trimethylamine (TMA), which can traverse the intestinal epithelial barrier and enter the bloodstream, ultimately reaching the liver where it undergoes oxidation catalyzed by flavin-containing monooxygenase 3 (FMO3) to form trimethylamine N-oxide (TMAO). While some TMAO is eliminated through renal excretion, remaining amounts circulate in the bloodstream, leading to systemic inflammation, endoplasmic reticulum (ER) stress, mitochondrial stress, and disruption of normal physiological functions in humans. As a representative microbial metabolite originating from the gut, TMAO has significant potential both as a biomarker for monitoring disease occurrence and progression and for tailoring personalized treatment strategies for patients. This review provides an extensive overview of TMAO sources and its metabolism in human blood, as well as its impact on several major human diseases. Additionally, we explore the latest research areas related to TMAO along with future directions.

Association Between Trimethylamine N-oxide and Adverse Kidney Outcomes and Overall Mortality in Type 2 Diabetes Mellitus

CONTEXT

Type 2 diabetes (T2D) is the major contributor to chronic kidney disease and end-stage kidney disease (ESKD). The influence of trimethylamine N-oxide (TMAO) on kidney outcomes in T2D remains unclear.

OBJECTIVE

To examine the association between fasting serum TMAO levels and adverse kidney outcomes in patients with T2D.

METHODS

Between October 2016 and June 2020, patients with T2D were recruited and monitored every 3 months until December 2021. Serum TMAO levels were assessed using liquid chromatography-mass spectrometry. The primary kidney outcomes were doubling of serum creatinine levels or progression to ESKD necessitating dialysis; the secondary kidney outcome was a rapid 30% decline in estimated glomerular filtration rate within 2 years. All-cause mortality was also evaluated.

RESULTS

Among the 440 enrolled patients with T2D, those in the highest serum TMAO tertile (≥0.88 μM) were older, had a longer diabetes duration, elevated blood urea nitrogen, and lower estimated glomerular filtration rate. Over a median follow-up period of 4 years, 26 patients (5.9%) had a doubling of serum creatinine level or progression to ESKD. After propensity score weighting, the patients in the highest serum TMAO tertile had a 6.45-fold increase in the risk of doubling of serum creatinine levels or progression to ESKD and 5.86-fold elevated risk of rapid decline in kidney function compared with those in the lowest tertile. Additionally, the stepwise increase in serum TMAO was associated with all-cause mortality.

CONCLUSION

Patients with T2D with elevated circulating TMAO levels are at higher risk of doubling serum creatinine, progressing to ESKD, and mortality. TMAO is a potential biomarker for kidney function progression and mortality in patients with T2D.

Multi-omics analysis of kidney tissue metabolome and proteome reveals the protective effect of sheep milk against adenine-induced chronic kidney disease in mice

Chronic kidney disease (CKD) is characterized by impaired renal function and is associated with inflammation, oxidative stress, and fibrosis. Sheep milk contains several bioactive molecules with protective effects against inflammation and oxidative stress. In the current study, we investigated the potential renoprotective effects of sheep milk and the associated mechanisms of action in an adenine-induced CKD murine model. Sheep milk delayed renal chronic inflammation (e.g., significant reduction in levels of inflammatory factors Vcam1, Icam1, Il6, and Tnfa), fibrosis (significant reduction in levels of fibrosis factors Col1a1, Fn1, and Tgfb), oxidative stress (significant increase in levels of antioxidants and decrease in oxidative markers), mineral disorders, and renal injury in adenine-treated mice (e.g. reduced levels of kidney injury markers NGAL and KIM-1). The combined proteomics and metabolomics analyses showed that sheep milk may affect the metabolic processes of several compounds, including proteins, lipids, minerals, and hormones in mice with adenine-induced chronic kidney disease. In addition, it may regulate the expression of fibrosis-related factors and inflammatory factors through the JAK1/STAT3/HIF-1α signaling pathway, thus exerting its renoprotective effects. Therefore, sheep milk may be beneficial for patients with CKD and should be evaluated in preclinical and clinical studies.

Antibiotic-induced intestinal microbiota depletion can attenuate the acute kidney injury to chronic kidney disease transition via NADPH oxidase 2 and trimethylamine-N-oxide inhibition

Intestinal microbiota and their metabolites affect systemic inflammation and kidney disease outcomes. Here, we investigated the key metabolites associated with the acute kidney injury (AKI)-to chronic kidney disease (CKD) transition and the effect of antibiotic-induced microbiota depletion (AIMD) on this transition. In 61 patients with AKI, 59 plasma metabolites were assessed to determine the risk of AKI-to-CKD transition. An AKI-to-CKD transition murine model was established four weeks after unilateral ischemia-reperfusion injury (IRI) to determine the effects of AIMD on the gut microbiome, metabolites, and pathological responses related to CKD transition. Human proximal tubular epithelial cells were challenged with CKD transition-related metabolites, and inhibitory effects of NADPH oxidase 2 (NOX2) signals were tested. Based on clinical metabolomics, plasma trimethylamine N-oxide (TMAO) was associated with a significantly increased risk for AKI-to-CKD transition [adjusted odds ratio 4.389 (95% confidence interval 1.106-17.416)]. In vivo, AIMD inhibited a unilateral IRI-induced increase in TMAO, along with a decrease in apoptosis, inflammation, and fibrosis. The expression of NOX2 and oxidative stress decreased after AIMD. In vitro, TMAO induced fibrosis with NOX2 activation and oxidative stress. NOX2 inhibition successfully attenuated apoptosis, inflammation, and fibrosis with suppression of G2/M arrest. NOX2 inhibition (in vivo) showed improvement in pathological changes with a decrease in oxidative stress without changes in TMAO levels. Thus, TMAO is a key metabolite associated with the AKI-to-CKD transition, and NOX2 activation was identified as a key regulator of TMAO-related AKI-to-CKD transition both in vivo and in vitro.

Paper spray mass spectrometry combined with machine learning as a rapid diagnostic for chronic kidney disease

A new analytical method for chronic kidney disease (CKD) detection utilizing paper spray mass spectrometry (PS-MS) combined with machine learning is presented. The analytical protocol is rapid and simple, based on metabolic profile alterations in urine. Anonymized raw urine samples were deposited (10 μL each) onto pointed PS-MS sample strips. Without waiting for the sample to dry, 75 μL of acetonitrile and high voltage were applied to the strips, using high resolution mass spectrometry measurement (15 s per sample) with polarity switching to detect a wide range of metabolites. Random forest machine learning was used to classify the resulting data. The diagnostic performance for the potential diagnosis of CKD was evaluated for accuracy, sensitivity, and specificity, achieving results >96% for the training data and >91% for validation and test data sets. Metabolites selected by the classification model as up- or down-regulated in healthy or CKD samples were tentatively identified and in agreement with previously reported literature. The potential utilization of this approach to discriminate albuminuria categories (normo, micro, and macroalbuminuria) was also demonstrated. This study indicates that PS-MS combined with machine learning has the potential to be used as a rapid and simple diagnostic tool for CKD.

Deliverables from Metabolomics in Kidney Disease: Adenine, New Insights, and Implication for Clinical Decision-Making

BACKGROUND

Chronic kidney disease (CKD) presents a persistent global health challenge, characterized by complex pathophysiology and diverse progression patterns. Metabolomics has emerged as a valuable tool in unraveling the intricate molecular mechanisms driving CKD progression.

SUMMARY

This comprehensive review provides a summary of recent progress in the field of metabolomics in kidney disease with a focus on spatial metabolomics to shed important insights to enhancing our understanding of CKD progression, emphasizing its transformative potential in early disease detection, refined risk assessment, and the development of targeted interventions to improve patient outcomes.

KEY MESSAGE

Through an extensive analysis of metabolic pathways and small-molecule fluctuations, bulk and spatial metabolomics offers unique insights spanning the entire spectrum of CKD, from early stages to advanced disease states. Recent advances in metabolomics technology have enabled spatial identification of biomarkers to provide breakthrough discoveries in predicting CKD trajectory and enabling personalized risk assessment. Furthermore, metabolomics can help decipher the complex molecular intricacies associated with kidney diseases for exciting novel therapeutic approaches. A recent example is the identification of adenine as a key marker of kidney fibrosis for diabetic kidney disease using both untargeted and targeted bulk and spatial metabolomics. The metabolomics studies were critical to identify a new biomarker for kidney failure and to guide new therapeutics for diabetic kidney disease. Similar approaches are being pursued for acute kidney injury and other kidney diseases to enhance precision medicine decision-making.

Investigation of the Metabolism of Astragaloside IV in a Puromycin-Damaged Rat Model by UPLC-Q-TOF-MS/MS Analysis

Astragaloside IV (AS-IV) has been shown to provide renal protection in various kidney injury models. However, the metabolic profile variation of AS-IV in pathological models in vivo is not well established. This study aims to explore the metabolic pathway of AS-IV in vivo in the classical puromycin aminonucleoside (PAN)-induced kidney injury in a rat model. Twelve Wistar rats were randomly divided into the AS-IV (CA) and the PAN+AS-IV (PA) treatment groups. PAN was injected by a single tail intravenous (i. v.) injection at 5 mg/100 g body weight, and AS-IV was administered intragastrically (i. g.) at 40 mg/kg for 10 days. Fecal samples of these rats were collected, and metabolites of AS-IV were detected by ultra-performance liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) to explore the AS-IV metabolic pathway. The metabolic differences between the AS-IV and PAN+AS-IV groups were compared. A total of 25 metabolites were detected, and deglycosylation, deoxygenation, and methyl oxidation were found to be the main metabolic pathways of AS-IV in vivo. The abundance of most of these metabolites in the PAN+AS-IV group was lower than that in the AS-IV treatment group, and differences for seven of them were statistically significant. Our study indicates that AS-IV metabolism is affected in the PAN-induced kidney injury rat model.

Pharmacological activation of constitutive androstane receptor induces female-specific modulation of hepatic metabolism

Background & Aims

The constitutive androstane receptor (CAR) is a nuclear receptor that binds diverse xenobiotics and whose activation leads to the modulation of the expression of target genes involved in xenobiotic detoxification and energy metabolism. Although CAR hepatic activity is considered to be higher in women than in men, its sex-dependent response to an acute pharmacological activation has seldom been investigated.

Methods

The hepatic transcriptome, plasma markers, and hepatic metabolome, were analysed in Car+/+ and Car-/- male and female mice treated either with the CAR-specific agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) or with vehicle.

Results

Although 90% of TCPOBOP-sensitive genes were modulated in a sex-independent manner, the remaining 10% showed almost exclusive female liver specificity. These female-specific CAR-sensitive genes were mainly involved in xenobiotic metabolism, inflammation, and extracellular matrix organisation. CAR activation also induced higher hepatic oxidative stress and hepatocyte cytolysis in females than in males. Hepatic expression of flavin monooxygenase 3 (Fmo3) was almost abolished and was associated with a decrease in hepatic trimethylamine-N-oxide (TMAO) concentration in TCPOBOP-treated females. In line with a potential role in the control of TMAO homeostasis, CAR activation decreased platelet hyper-responsiveness in female mice supplemented with dietary choline.

Conclusions

More than 10% of CAR-sensitive genes are sex-specific and influence hepatic and systemic responses such as platelet aggregation. CAR activation may be an important mechanism of sexually-dimorphic drug-induced liver injury.

Impact and implications

CAR is activated by many drugs and pollutants. Its pharmacological activation had a stronger impact on hepatic gene expression and metabolism in females than in males, and had a specific impact on liver toxicity and trimethylamine metabolism. Sexual dimorphism should be considered when testing and/or prescribing xenobiotics known to activate CAR.

Metabolomics study reveals increased deoxycholic acid contributes to deoxynivalenol-mediated intestinal barrier injury

AIMS

Deoxynivalenol (DON), namely vomitoxin, is one of the most prevalent fungal toxins in cereal crops worldwide. However, the underlying toxic mechanisms of DON remain largely unknown.

MAIN METHODS

DON exposure-caused changes in the murine plasma metabolome and gut microbiome were investigated by an LC-MS/MS-based nontargeted metabolomics approach and sequencing of 16S rRNA in fecal samples, respectively. Cellular models were then used to validate the findings from the metabolomics study.

KEY FINDINGS

DON exposure increased intestinal barrier permeability evidenced by its-mediated decrease in colonic Claudin 5 and E-cadherin, as well as increases in colonic Ifn-γ, Cxcl9, Cxcl10, and Cxcr3. Furthermore, DON exposure resulted in a significant increase in murine plasma levels of deoxycholic acid (DCA). Also, DON exposure led to gut microbiota dysbiosis, which was associated with DON exposure-caused increase in plasma DCA. In addition, we found not only DON but also DCA dose-dependently caused a significant increase in the levels of IFN-γ, CXCL9, CXCL10, and/or CXCR3, as well as a significant decrease in the expression levels of Claudin 5 and/or E-cadherin in the human colonic epithelial cells (NCM460).

SIGNIFICANCE

DON-mediated increase in DCA contributes to DON-caused intestinal injury. DCA may be a potential therapeutic target for DON enterotoxicity.

From heart failure and kidney dysfunction to cardiorenal syndrome: TMAO may be a bridge

The study of trimethylamine oxide (TMAO), a metabolite of gut microbiota, and heart failure and chronic kidney disease has made preliminary achievements and been summarized by many researchers, but its research in the field of cardiorenal syndrome is just beginning. TMAO is derived from the trimethylamine (TMA) that is produced by the gut microbiota after consumption of carnitine and choline and is then transformed by flavin-containing monooxygenase (FMO) in the liver. Numerous research results have shown that TMAO not only participates in the pathophysiological progression of heart and renal diseases but also significantly affects outcomes in chronic heart failure (CHF) and chronic kidney disease (CKD), besides influencing the general health of populations. Elevated circulating TMAO levels are associated with adverse cardiovascular events such as HF, myocardial infarction, and stroke, patients with CKD have a poor prognosis as well. However, no study has confirmed an association between TMAO and cardiorenal syndrome (CRS). As a syndrome in which heart and kidney diseases intersect, CRS is often overlooked by clinicians. Here, we summarize the research on TMAO in HF and kidney disease and review the existing biomarkers of CRS. At the same time, we introduced the relationship between exercise and gut microbiota, and appropriately explored the possible mechanisms by which exercise affects gut microbiota. Finally, we discuss whether TMAO can serve as a biomarker of CRS, with the aim of providing new strategies for the detection, prognostic, and treatment evaluation of CRS.

Metabolomic epidemiology offers insights into disease aetiology

Metabolomic epidemiology is the high-throughput study of the relationship between metabolites and health-related traits. This emerging and rapidly growing field has improved our understanding of disease aetiology and contributed to advances in precision medicine. As the field continues to develop, metabolomic epidemiology could lead to the discovery of diagnostic biomarkers predictive of disease risk, aiding in earlier disease detection and better prognosis. In this Review, we discuss key advances facilitated by the field of metabolomic epidemiology for a range of conditions, including cardiometabolic diseases, cancer, Alzheimer's disease and COVID-19, with a focus on potential clinical utility. Core principles in metabolomic epidemiology, including study design, causal inference methods and multi-omic integration, are briefly discussed. Future directions required for clinical translation of metabolomic epidemiology findings are summarized, emphasizing public health implications. Further work is needed to establish which metabolites reproducibly improve clinical risk prediction in diverse populations and are causally related to disease progression.

Urinary microbiota and serum metabolite analysis in patients with diabetic kidney disease

Background

Diabetic kidney disease (DKD) is a common and potentially fatal consequence of diabetes. Chronic renal failure or end-stage renal disease may result over time. Numerous studies have demonstrated the function of the microbiota in health and disease. The use of advanced urine culture techniques revealed the presence of resident microbiota in the urinary tract, undermining the idea of urine sterility. Studies have demonstrated that the urine microbiota is related with urological illnesses; nevertheless, the fundamental mechanisms by which the urinary microbiota influences the incidence and progression of DKD remain unclear. The purpose of this research was to describe key characteristics of the patients with DKD urinary microbiota in order to facilitate the development of diagnostic and therapeutic for DKD.

Methods

We evaluated the structure and composition of the microbiota extracted from urine samples taken from DKD patients (n = 19) and matched healthy controls (n = 15) using 16S rRNA gene sequencing. Meanwhile, serum metabolite profiles were compared using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Associations between clinical characteristics, urine microbiota, and serum metabolites were also examined. Finally, the interaction between urine microbiota and serum metabolites was clarified based on differential metabolite abundance analysis.

Results

The findings indicated that the DKD had a distinct urinary microbiota from the healthy controls (HC). Taxonomic investigations indicated that the DKD microbiome had less alpha diversity than a control group. Proteobacteria and Acidobacteria phyla increased in the DKD, while Firmicutes and Bacteroidetes decreased significantly (P < 0.05). Acidobacteria was the most prevalent microbiota in the DKD, as determined by the Linear discriminant analysis Effect Size (LEfSe) plot. Changes in the urinary microbiota of DKD also had an effect on the makeup of metabolites. Short-chain fatty acids (SCFAs) and protein-bound uremic toxins (PBUTs) were shown to be specific. Then we discovered that arginine and proline metabolism was the primary mechanism involved in the regulation of diabetic kidney disease.

Conclusions

This study placed the urinary microbiota and serum metabolite of DKD patients into a functional framework and identified the most abundant microbiota in DKD (Proteobacteria and Acidobacteria). Arginine metabolites may have a major effect on DKD patients, which correlated with the progression of DKD.

Renal fibrosis in type 2 cardiorenal syndrome: An update on mechanisms and therapeutic opportunities

Cardiorenal syndrome (CRS) is a state of coexisting heart failure and renal insufficiency in which acute or chronic dysfunction of the heart or kidney lead to acute or chronic dysfunction of the other organ.It was found that renal fibrosis is an important pathological process in the progression of type 2 CRS to end-stage renal disease, and progressive renal impairment accelerates the deterioration of cardiac function and significantly increases the hospitalization and mortality rates of patients. Previous studies have found that Hemodynamic Aiteration, RAAS Overactivation, SNS Dysfunction, Endothelial Dysfunction and Imbalance of natriuretic peptide system contribute to the development of renal disease in the decompensated phase of heart failure, but the exact mechanisms is not clear. Therefore, in this review, we focus on the molecular pathways involved in the development of renal fibrosis due to heart failure and identify the canonical and non-canonical TGF-β signaling pathways and hypoxia-sensing pathways, oxidative stress, endoplasmic reticulum stress, pro-inflammatory cytokines and chemokines as important triggers and regulators of fibrosis development, and summarize the therapeutic approaches for the above signaling pathways, including SB-525334 Sfrp1, DKK1, IMC, rosarostat, 4-PBA, etc. In addition, some potential natural drugs for this disease are also summarized, including SQD4S2, Wogonin, Astragaloside, etc.

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.

Chlorogenic Acid Prevents Hyperuricemia Nephropathy via Regulating TMAO-Related Gut Microbes and Inhibiting the PI3K/AKT/mTOR Pathway

Hyperuricemia is an independent hazard factor of renal injury and can induce renal fibrosis, promoting the development of chronic kidney disease (CKD). This study aimed to explore the probability of chlorogenic acid (CGA) as a potential substance for preventing hyperuricemia nephropathy (HN). Pretreatment with CGA downregulated SUA, BUN, and CR levels, relieved oxidative stress and inflammatory response, alleviated kidney fibrosis, and contributed to the prevention of HN. In the gut microbiota, Blautia, Enterococcus, and Faecalibaculum related to trimethylamine N-oxide (TMAO) synthesis were significantly increased in HN rats. In addition, it showed a significant increase in serum TMAO content in HN rats. However, CGA regulated the cascade response of the microbiota-TMAO signaling to reverse the increase of serum TMAO. CGA also decreased the protein expression of protein kinase B (AKT) phosphorylation, phosphatidylinositide 3-kinase (PI3K), and mammalian target of rapamycin (mTOR) by reducing the production of TMAO. CGA delayed kidney fibrosis in HN rats as evidenced by regulating the cascade response of the microbiota-TMAO-PI3K/AKT/mTOR signaling pathway. In summary, CGA can be an excellent candidate for HN prevention.

TMAO as a potential biomarker and therapeutic target for chronic kidney disease: A review

The gut microbiota and its metabolites have become a hotspot of recent research. Trimethylamine N-oxide (TMAO) metabolized by the gut microbiota is closely related to many diseases such as cardiovascular disease, chronic kidney disease, type 2 diabetes, etc. Chronic kidney disease (CKD) is an important contributor to morbidity and mortality from non-communicable diseases. Recently, increasing focus has been put on the role of TMAO in the development and progress of chronic kidney disease. The level of TMAO in patients with chronic kidney disease is significantly increased, and a high level of TMAO deteriorates chronic kidney disease. This article describes the relationship between TMAO and chronic kidney disease and the research progress of drugs targeted TMAO, providing a reference for the development of anti-chronic kidney disease drugs targeted TMAO.