Intestinal metabolites, chronic kidney disease and renal transplantation: Enigma Variations?

Safety and outcomes of hip and knee replacement surgery in liver transplant recipients

BACKGROUND

Liver transplant (LT) is becoming increasingly common with improved life expectancy. Joint replacement is usually a safe procedure; however, its safety in LT recipients remains understudied.

AIM

To evaluate the mortality, outcome, and 90-d readmission rate in LT patients undergoing hip and knee replacement surgery.

METHODS

Patients with history of LT who underwent hip and knee replacement surgery between 2016 and 2019 were identified using the National Readmission Database.

RESULTS

A total of 5046119 hip and knee replacement surgeries were identified. 3219 patients had prior LT. Mean age of patients with no history of LT was 67.51 [95% confidence interval (CI): 67.44-67.58], while it was 64.05 (95%CI: 63.55-64.54) in patients with LT. Patients with history of LT were more likely to have prolonged length of hospital stay (17.1% vs 8.4%, P < 0.001). The mortality rate for patients with no history of LT was 0.22%, while it was 0.24% for patients with LT (P = 0.792). Patients with history of LT were more likely to have re-admissions within 90 d of initial hospitalization: 11.4% as compared to 6.2% in patients without history of LT (P < 0.001). The mortality rate between both groups during readmission was not statistically different (1.9% vs 2%, P = 0.871) respectively.

CONCLUSION

Hip and knee replacements in patients with history of LT are not associated with increased mortality; increased re-admissions were more frequent in this cohort of patients. Chronic kidney disease and congestive heart failure appear to predict higher risk of readmission.

Recent advances of gut microbiota in chronic kidney disease patients

Chronic kidney disease (CKD) is a worldwide public health issue and has ultimately progressed to an end-stage renal disease that requires life-long dialysis or renal transplantation. However, the underlying molecular mechanism of these pathological development and progression remains to be fully understood. The human gut microbiota is made up of approximately 100 trillion microbial cells including anaerobic and aerobic species. In recent years, more and more evidence has indicated a clear association between dysbiosis of gut microbiota and CKD including immunoglobulin A (IgA) nephropathy, diabetic kidney disease, membranous nephropathy, chronic renal failure and end-stage renal disease. The current review describes gut microbial dysbiosis and metabolites in patients with CKD thus helping to understand human disease. Treatment with prebiotics, probiotics and natural products can attenuate CKD through improving dysbiosis of gut microbiota, indicating a novel intervention strategy in patients with CKD. This review also discusses therapeutic options, such as prebiotics, probiotics and natural products, for targeting dysbiosis of gut microbiota in patients to provide more specific concept-driven therapy strategy for CKD treatment.

Evaluation of Salivary Indoxyl Sulfate with Proteinuria for Predicting Graft Deterioration in Kidney Transplant Recipients

Acute kidney injury (AKI) is a significant risk factor for developing chronic kidney disease and progression to end-stage renal disease in elderly patients. AKI is also a relatively common complication after kidney transplantation (KTx) associated with graft failure. Since the lifespan of a transplanted kidney is limited, the risk of the loss/deterioration of graft function (DoGF) should be estimated to apply the preventive treatment. The collection of saliva and urine is more convenient than collecting blood and can be performed at home. The study aimed to verify whether non-invasive biomarkers, determined in saliva and urine, may be useful in the prediction of DoGF in kidney transplant recipients (KTRs) (n = 92). Salivary and serum toxins (p-cresol sulfate, pCS; indoxyl sulfate, IS) concentrations were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Urinary proteins, hemoglobin, and glucose were measured using a semi-quantitative strip test. Salivary IS (odds ratio (OR) = 1.19), and proteinuria (OR = 3.69) were demonstrated as independent factors for the prediction of DoGF. Satisfactory discriminatory power (area under the receiver operating characteristic curve (AUC) = 0.71 ± 0.07) and calibration of the model were obtained. The model showed that categories of the increasing probability of the risk of DoGF are associated with the decreased risk of graft survival. The non-invasive diagnostic biomarkers are a useful screening tool to identify high-risk patients for DoGF.

The effects of Fushen Granule on the composition and function of the gut microbiota during Peritoneal Dialysis-Related Peritonitis

BACKGROUND

Peritoneal dialysis (PD) is an acknowledged treatment for patients with irreversible kidney failure. The treatment usually causes peritoneal dialysis-related peritonitis (PDRP), a common complication of PD that can lead to inadequate dialysis, gastrointestinal dysfunction, and even death. Recent studies indicated that Fushen Granule (FSG), a Chinese herbal formula, improves the treatment of PD. However, the mechanism of how FSG plays its role in the improvement is still unclear. Gut microbiota has been closely related to the development of various diseases. We carried out a randomized controlled trial to assess whether FSG can modulate the gut microbiota during PDRP treatment.

METHODS

Forty-two PDRP patients were recruited into the clinical trial, and they were randomly divided into control(CON), probiotics(PRO) or Fushen granule group(FSG). To check whether FSG improve the PD treatment, we assessed the clinical parameters, including albumin(ALB), hemoglobin(HGB), blood urea nitrogen(BUN) and creatinine(CR). Fecal samples were collected before hospitalization and discharge, and stored at -80°C within 1 hour. And we assessed the microbial population and function by applying the 16S rRNA gene sequencing and functional enrichment analysis.

RESULTS

Compared to control group, ALB is improved in both probiotics and FSG groups, while HGB is increased but BUN and CR is reduced in FSG group. Sequencing of 16S rRNA genes revealed that FSG and PRO affected the composition of the microbial community. FSG significantly increased a abundant represented by Bacteroides, Megamonas and Rothia, which was significantly correlated with the improvements in carbohydrate and amino acid metabolism.

CONCLUSIONS

This study demonstrates that FSG ameliorates the nutritional status and improves the quality of life by enriching beneficial bacteria associated with metabolism. These results indicate that FSG as alternative medicine is a promising treatment for patients with PDRP.

Less arterial stiffness in kidney transplant recipients than chronic kidney disease patients matched for renal function

BACKGROUND

Chronic kidney disease is associated with a high cardiovascular risk. Compared with glomerular filtration rate-matched CKD patients (CKDps), we previously reported a 2.7-fold greater risk of global mortality among kidney transplant recipients (KTRs). We then examined aortic stiffness [evaluated by carotid-femoral pulse wave velocity (CF-PWV)] and cardiovascular risk in KTRs compared with CKDps with comparable measured glomerular filtration rate (mGFR).

METHODS

We analysed CF-PWV in two cohorts: TransplanTest (KTRs) and NephroTest (CKDps). Propensity scores were calculated including six variables: mGFR, age, sex, mean blood pressure (MBP), body mass index (BMI) and heart rate. After propensity score matching, we included 137 KTRs and 226 CKDps. Descriptive data were completed by logistic regression for CF-PWV values higher than the median (>10.6 m/s).

RESULTS

At 12 months post-transplant, KTRs had significantly lower CF-PWV than CKDps (10.1 versus 11.0 m/s, P = 0.008) despite no difference at 3 months post-transplant (10.5 versus 11.0 m/s, P = 0.242). A lower occurrence of high arterial stiffness was noted among KTRs compared with CKDps (38.0% versus 57.1%, P < 0.001). It was especially associated with lower mGFR, older age, higher BMI, higher MBP, diabetes and higher serum parathyroid hormone levels. After adjustment, the odds ratio for the risk of high arterial stiffness in KTRs was 0.40 (95% confidence interval 0.23-0.68, P < 0.001).

CONCLUSIONS

Aortic stiffness was significantly less marked in KTRs 1 year post-transplant than in CKDps matched for GFR and other variables. This observation is compatible with the view that the pathogenesis of post-transplant cardiovascular disease differs, at least in part, from that of CKD per se.

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

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

Difference in Profiles of the Gut-Derived Tryptophan Metabolite Indole Acetic Acid between Transplanted and Non-Transplanted Patients with Chronic Kidney Disease

BACKGROUND

Uremic toxins have emerged as potential mediators of morbidity and mortality in patients with chronic kidney disease (CKD). Indole-3-acetic acid (IAA, a tryptophan-derived uremic toxin) might be a useful biomarker in patients with CKD. The objectives of the present study were to (i) describe IAA concentrations in a cohort of non-transplanted patients with CKD and a cohort of transplanted patients with CKD, and (ii) investigate the possible relationship between IAA levels and adverse outcomes in the two cohorts.

METHODS

Levels of free and total IAA were assayed in the two prospective CKD cohorts (140 non-transplanted patients and 311 transplanted patients). Cox multivariate analyses were used to evaluate the association between IAA levels and outcomes (mortality, cardiovascular events, and graft loss).

RESULTS

In the non-transplanted CKD cohort, free and total IAA increased progressively with the CKD stage. In the transplanted CKD cohort, free and total IAA levels were elevated at the time of transplantation but had fallen substantially at one-month post-transplantation. Indole acetic acid concentrations were lower in transplanted patients than non-dialysis non-transplanted patients matched for estimated glomerular filtration rate (eGFR), age, and sex. After adjustment for multiple confounders, the free IAA level predicted overall mortality and cardiovascular events in the non-transplanted CKD cohort (hazard ratio [95% confidence interval]: 2.5 [1.2-5.1] and 2.5 [1.3-4.8], respectively). In the transplanted CKD cohort, however, no associations were found between free or total IAA on one hand, and mortality, CV event, or graft survival on the other.

CONCLUSION

We demonstrated that levels of IAA increase with the CKD stage, and fall substantially, even normalizing, after kidney transplantation. Free IAA appears to be a valuable outcome-associated biomarker in non-transplanted patients, but-at least in our study setting-not in transplanted patients.

Uremic Toxins and Clinical Outcomes: The Impact of Kidney Transplantation

Non-transplanted and transplanted patients with chronic kidney disease (CKD) differ in terms of mortality and the risk of clinical events. This difference is probably due to the difference of both traditional and non-traditional risk factors. Uremic retention solutes may constitute important non-traditional risk factors in this population. In the present review, we selected a set of uremic toxins that have been associated with harmful effects, and are an appealing target for adjuvant therapy in CKD. For each toxin reviewed here, relevant studies were selected and the relationship with hard clinical outcomes of uremic toxins were compared between non-transplanted CKD patients and transplanted patients taking into account the level of glomerular filtration rate in these two situations.

Microbiota-derived uremic retention solutes: perpetrators of altered nonrenal drug clearance in kidney disease

INTRODUCTION

Scientific interest in the gut microbiota is increasing due to improved understanding of its implications in human health and disease. In patients with kidney disease, gut microbiota-derived uremic toxins directly contribute to altered nonrenal drug clearance. Microbial imbalances, known as dysbiosis, potentially increase formation of microbiota-derived toxins, and diminished renal clearance leads to toxin accumulation. High concentrations of microbiota-derived toxins such as indoxyl sulfate and p-cresol sulfate perpetrate interactions with drug metabolizing enzymes and transporters, which provides a mechanistic link between increases in drug-related adverse events and dysbiosis in kidney disease. Areas covered: This review summarizes the effects of microbiota-derived uremic toxins on hepatic phase I and phase II drug metabolizing enzymes and drug transporters. Research articles that tested individual toxins were included. Therapeutic strategies to target microbial toxins are also discussed. Expert commentary: Large interindividual variability in toxin concentrations may explain some differences in nonrenal clearance of medications. Advances in human microbiome research provide unique opportunities to systematically evaluate the impact of individual and combined microbial toxins on drug metabolism and transport, and to explore microbiota-derived uremic toxins as potential therapeutic targets.

Protein-bound toxins: has the Cinderella of uraemic toxins turned into a princess?

Chronic kidney disease (CKD) has emerged as a global public health problem. Although the incidence and prevalence of CKD vary from one country to another, the estimated worldwide prevalence is 8-16%. The complications associated with CKD include progression to end-stage renal disease (ESRD), mineral and bone disorders, anaemia, cognitive decline and elevated all-cause and cardiovascular (CV) mortality. As a result of progressive nephron loss, patients with late-stage CKD are permanently exposed to uraemic toxins. These toxins have been classified into three groups as a function of the molecular mass: small water-soluble molecules, middle molecules and protein-bound uraemic toxins. The compounds can also be classified according to their origin (i.e. microbial or not) or their protein-binding ability. The present review will focus on the best-characterized protein-bound uraemic toxins, namely indoxylsulfate (IS), indole acetic acid (IAA) and p-cresylsulfate (PCS, a cresol metabolite). Recent research suggests that these toxins accelerate the progression of CV disease, kidney disease, bone disorders and neurological complications. Lastly, we review therapeutic approaches that can be used to decrease toxin levels.

p-Cresyl Sulfate

If chronic kidney disease (CKD) is associated with an impairment of kidney function, several uremic solutes are retained. Some of these exert toxic effects, which are called uremic toxins. p-Cresyl sulfate (pCS) is a prototype protein-bound uremic toxin to which many biological and biochemical (toxic) effects have been attributed. In addition, increased levels of pCS have been associated with worsening outcomes in CKD patients. pCS finds its origin in the intestine where gut bacteria metabolize aromatic amino acids, such as tyrosine and phenylalanine, leading to phenolic end products, of which pCS is one of the components. In this review we summarize the biological effects of pCS and its metabolic origin in the intestine. It appears that, according to in vitro studies, the intestinal bacteria generating phenolic compounds mainly belong to the families Bacteroidaceae, Bifidobacteriaceae, Clostridiaceae, Enterobacteriaceae, Enterococcaceae, Eubacteriaceae, Fusobacteriaceae, Lachnospiraceae, Lactobacillaceae, Porphyromonadaceae, Staphylococcaceae, Ruminococcaceae, and Veillonellaceae. Since pCS remains difficult to remove by dialysis, the gut microbiota could be a future target to decrease pCS levels and its toxicity, even at earlier stages of CKD, aiming at slowing down the progression of the disease and decreasing the cardiovascular burden.