Intestinal Barrier Disturbances in Haemodialysis Patients: Mechanisms, Consequences, and Therapeutic Options

Effect of High Sodium Intake on Gut Tight Junctions' Structure and Permeability to Bacterial Toxins in a Rat Model of Chronic Kidney Disease

INTRODUCTION

Uremic toxicity changes the gut structure and permeability, allowing bacterial toxins to translocate from the lumen to the blood during chronic kidney failure (CKD). Clinical fluid overload and tissue edema without uremia have similar effects but have not been adequately demonstrated and analyzed in CKD.

AIMS

To investigate the effect of sodium intake on the plasma concentration of gut-derived uremic toxins, indoxyl sulfate (IS), and p-cresyl sulfate (pCS) and the expression of genes and proteins of epithelial gut tight junctions in a rat model of CKD.

METHODS

Sham-operated (control group, CG) and five-sixths nephrectomized (5/6Nx) Sprague-Dawley rats were randomly assigned to low (LNa), normal (NNa), or high sodium (HNa) diets., Animals were then sacrificed at 8 and 12 weeks and analyzed for IS and pCS plasma concentrations, as well as for gene and protein expression of thigh junction proteins, and transmission electron microscopy (TEM) in colon fragments.

RESULTS

The HNa 5/6Nx groups had higher concentrations of IS and pCS than CG, NNa, and LNa at eight and twelve weeks. Furthermore, HNa 5/6Nx groups had reduced expression of the claudin-4 gene and protein than CG, NNa, and LNa. HNa had reduced occludin gene expression compared to CG. Occludin protein expression was more reduced in HNa than in CG, NNa, and LNa. The gut epithelial tight junctions appear dilated in HNa compared to NNa and LNa in TEM.

CONCLUSION

Dietary sodium intake and fluid overload have a significant role in gut epithelial permeability in the CKD model.

The effect of intradialytic exercise on calcium, phosphorus and parathyroid hormone: a randomized controlled trial

BACKGROUND

Patients with kidney failure experience derangements of circulating markers of mineral metabolism and dysregulation of skeletal and cardiovascular physiology which results in high mortality rate in these patients. This study aimed to evaluate the effect of intradialytic exercise on regulation of these abnormalities in patients receiving chronic hemodialysis (HD).

METHODS

In this randomized controlled trial conducted in an HD center in Iran, adult patients receiving chronic HD were randomized to intradialytic exercise (60 min) in the second hour of thrice weekly dialysis for 6 months (intervention) or no intradialytic exercise (control). The primary outcomes were serum calcium, serum phosphorous and parathyroid hormone levels. Secondary outcomes were serum alkaline phosphatase and calcium-phosphorous product.

RESULTS

The study included 44 participants randomized to intervention (n = 22) or control (n = 22). During the 6-month intervention period, significant between-group changes were observed in all primary and secondary outcomes between the intervention and control groups. Statistical analyses reveal a significant increase in serum calcium (P < 0.05) as well as a significant decrease in serum phosphorous, parathyroid hormone, alkaline phosphatase and calcium-phosphorous product (P < 0.05).

CONCLUSION

Intradialytic exercise performed for at least 60 min during thrice weekly dialysis sessions improves bone mineral metabolism in adult patients receiving HD. Further studies should focus on observing and comparing the effect of different types of exercise on bone mineral disorders and all-cause mortality in HD patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04916743, Registered on 08/06/2021. Registered trial name: The Effect of Intradialytic Exercise on Calcium, Phosphorous and Parathyroid Hormone: A Randomized Controlled Trial.

The pathogenic role of intestinal flora metabolites in diabetic nephropathy

With the increasing incidence of diabetes, diabetic kidney disease has become a major cause of chronic kidney disease. The role of the gut microbiota in diabetes and its related complications have been extensively investigated; the modulatory effect of the gut microbiota on the host depends on several gut microbial metabolites, particularly short-chain fatty acids, secondary bile acids, and trimethylamine N-oxide. In this review, we focused on the evidence related to the pathogenic role of each of the gut microbial metabolites in diabetic nephropathy. The main novel therapies targeting the gut microbiota include probiotics, dietary prebiotics, synbiotic supplements, and faecal microbiota transplants, although there is no standard treatment principle. Further research is therefore needed to elucidate the link between gut microbes and diabetic nephropathy, and more therapeutic targets should be explored to treat diabetic nephropathy with dysbiosis of the gut microbes.

An update review on hemodynamic instability in renal replacement therapy patients

BACKGROUND

Hemodynamic instability in patients undergoing kidney replacement therapy (KRT) is one of the most common and essential factors influencing mortality, morbidity, and the quality of life in this patient population.

METHOD

Decreased cardiac preload, reduced systemic vascular resistance, redistribution of fluids, fluid overload, inflammatory factors, and changes in plasma osmolality have all been implicated in the pathophysiology of hemodynamic instability associated with KRT.

RESULT

A cascade of these detrimental mechanisms may ultimately cause intra-dialytic hypotension, reduced tissue perfusion, and impaired kidney rehabilitation. Multiple parameters, including dialysate composition, temperature, posture during dialysis sessions, physical activity, fluid administrations, dialysis timing, and specific pharmacologic agents, have been studied as possible management modalities. Nevertheless, a clear consensus is not reached.

CONCLUSION

This review includes a thorough investigation of the literature on hemodynamic instability in KRT patients, providing insight on interventions that may potentially minimize factors leading to hemodynamic instability.

Homeostasis in the Gut Microbiota in Chronic Kidney Disease

The gut microbiota consists of trillions of microorganisms, fulfilling important roles in metabolism, nutritional intake, physiology and maturation of the immune system, but also aiding and abetting the progression of chronic kidney disease (CKD). The human gut microbiome consists of bacterial species from five major bacterial phyla, namely Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria, and Verrucomicrobia. Alterations in the members of these phyla alter the total gut microbiota, with a decline in the number of symbiotic flora and an increase in the pathogenic bacteria, causing or aggravating CKD. In addition, CKD-associated alteration of this intestinal microbiome results in metabolic changes and the accumulation of amines, indoles and phenols, among other uremic metabolites, which have a feedforward adverse effect on CKD patients, inhibiting renal functions and increasing comorbidities such as atherosclerosis and cardiovascular diseases (CVD). A classification of uremic toxins according to the degree of known toxicity based on the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence was selected to identify the representative uremic toxins from small water-soluble compounds, protein-bound compounds and middle molecules and their relation to the gut microbiota was summarized. Gut-derived uremic metabolites accumulating in CKD patients further exhibit cell-damaging properties, damage the intestinal epithelial cell wall, increase gut permeability and lead to the translocation of bacteria and endotoxins from the gut into the circulatory system. Elevated levels of endotoxins lead to endotoxemia and inflammation, further accelerating CKD progression. In recent years, the role of the gut microbiome in CKD pathophysiology has emerged as an important aspect of corrective treatment; however, the mechanisms by which the gut microbiota contributes to CKD progression are still not completely understood. Therefore, this review summarizes the current state of research regarding CKD and the gut microbiota, alterations in the microbiome, uremic toxin production, and gut epithelial barrier degradation.

Assessment of Gut leakage Induced Systemic Inflammation in Children on Chronic Hemodialysis

BACKGROUND: Children with chronic kidney disease (CKD) are at high risk to develop GIT complications such as intestinal wall edema and increased permeability which contributes to chronic systemic inflammation that increases morbidity and mortality burden. AIM: This study aim was to show the relationship between inflammation and increased intestinal permeability in children on hemodialysis (HD). METHODS: The study included 50 children with CKD on regular HD of variable duration; their age range was (5−16) years and 40 controls. They were followed up at Nephrology clinic- Eldemerdash hospital. Complete history taking, physical examination were done. Laboratory measurement in the form of zonulin, tumor necrosis factor-alpha (TNF-alpha), high sensitive C-reactive protein (hs-CRP), and alpha1-antitrypsin (AAT) were quantified in serum by ELISA method. RESULTS: There was a highly significant decrease in anthropometric measures (weight, height and BMI) and their corresponding z score in cases compared to controls with p ≤ 0.001. Furthermore, there was significant increase of levels of zonulin, TNF-alpha, AAT, and hs-CRP in cases compared to controls with p value of 0.009, 0.001, 0.002, and 0.003, respectively. There was significant positive correlation between zonulin and (TNF-alpha, AAT, hs-CRP, and creatinine) with P values (0.003, 0.001, 0.001, and 0.001), respectively. Zonulin is negatively correlated with weight for age Z score (WAZ) and height with p value (0.01 and 0.018), respectively. TNF-alpha and hs-CRP were negatively correlated with WAZ with P-values of 0.02 and 0.01, respectively. CONCLUSION: Children with CKD on chronic hemodialysis had elevated levels of zonulin, TNF-alpha, hs-CRP, and AAT which reflects gut permeability induced systemic inflammatory state.

Serum Sphingosine-1-phosphate level and peritonitis in peritoneal dialysis patients

BACKGROUND

Given the important role of Sphingosine-1-phosphate (S1P) in maintaining the hemostasis in intestinal barrier function and regulation of inflammation and immune, we hypothesize that S1P might be a biomarker to predict peritonitis in peritoneal dialysis (PD) patients.

METHODS

In this case-control study, 78 stable, continuous ambulatory peritoneal dialysis patients were enrolled and followed for the episode of PD associated peritonitis. Patients were divided into two groups by whether or not they had peritonitis during follow-up: non-peritonitis (n = 65) and peritonitis (n = 13) group. S1P was analyzed by enzyme-linked immunosorbent assay. Logistic regression analysis was used to assess factors associated with peritonitis. The variables identified by univariable regression models (p < 0.1) were further selected into the multivariable logistic regression model to determine whether they could independently affect peritonitis.

RESULTS

Patients with peritonitis had a lower level of S1P than that of patients without peritonitis (1.3 ng/mL IQ 0.8, 3.6 ng/mL vs. 2.8 ng/mL IQ 1.5, 5.4 ng/mL, p = 0.018). The peritonitis group had lower serum albumin, lower blood leukocyte, lower hemoglobin and lower platelet count as compared to the non-peritonitis group. Logistic regression analysis showed that S1P (OR = 0.381, 95% CI = 0.171-0.848, p = 0.018), blood leukocyte count (OR = 0.438, 95% CI = 0.207-0.925, p = 0.030), and serum albumin (OR = 0.732, 95% CI = 0.556-0.962, p = 0.025) were independent factors associated with peritonitis in the present PD population.

CONCLUSION

Our study showed that S1P was an independent determinant of subsequent peritonitis in PD patients. S1P might serve as a biomarker to predict peritonitis in PD patients.

Circulating endotoxin and inflammation: associations with fitness, physical activity and the effect of a six-month programme of cycling exercise during haemodialysis

BACKGROUND

Intradialytic cycling (IDC) may provide cardiovascular benefit to individuals receiving haemodialysis, but the exact mechanism behind these improvements remains unclear. The primary aim of this study was to investigate the effect of a six-month programme of IDC on circulating endotoxin (secondary analysis from the CYCLE-HD trial). Secondary aims were to investigate changes in circulating cytokines (IL-6, IL-10, TNF-α, CRP and IL6/IL-10), and their associations with physical activity, fitness and cardiovascular outcomes.

METHODS

Participants were randomised to either a six-month programme of IDC (thrice weekly, moderate intensity cycling at RPE 12-14) in addition to usual care (n = 46), or usual care only (control group; n = 46). Outcome measures were obtained at baseline and then again at six months.

RESULTS

There was no significant (P=0.137) difference in circulating endotoxin between groups at 6-months (IDC group: 0.34±0.08 EU/mL; control group: 0.37±0.07 EU/mL). There were no significant between group difference in any circulating cytokine following the 6-month programme of IDC. Higher levels of physical activity and fitness were associated with lower levels of endotoxin, IL-6, CRP, and IL-6/IL-10.

CONCLUSIONS

Our data show no change in circulating endotoxin or cytokines following a 6-month programme of IDC. However, higher levels of physical activity outside of haemodialysis were associated with lower levels of inflammation.

Cardiopulmonary and metabolic physiology during hemodialysis and inter/intradialytic exercise

Hemodialysis is associated with numerous symptoms and side effects that, in part, may be due to subclinical hypoxia. However, acute cardiopulmonary and metabolic physiology during hemodialysis is not well defined. Intradialytic and interdialytic exercise appear to be beneficial and may alleviate these side effects. To better understand these potential benefits, the acute physiological response to exercise should be evaluated. The aim of this study was to compare and characterize the acute physiological response during hemodialysis, intradialytic exercise, and interdialytic exercise. Cardiopulmonary physiology was evaluated during three conditions: 1) hemodialysis without exercise (HD), 2) intradialytic exercise (IDEx), and 3) interdialytic exercise (Ex). Exercise consisted of 30-min constant load cycle ergometry at 90% V̇O₂AT (anaerobic threshold). Central hemodynamics (via noninvasive bioreactance) and ventilatory gas exchange were recorded during each experimental condition. Twenty participants (59 ± 12 yr, 16/20 male) completed the protocol. Cardiac output (Δ = -0.7 L/min), O₂ uptake (Δ = -1.4 mL/kg/min), and arterial-venous O₂ difference (Δ = -2.0 mL/O₂/100 mL) decreased significantly during HD. Respiratory exchange ratio exceeded 1.0 throughout HD and IDEx. Minute ventilation was lower (P = 0.001) during IDEx (16.5 ± 1.1 L/min) compared with Ex (19.8 ± 1.0 L/min). Arterial-venous O₂ difference was partially restored further to IDEx (4.6 ± 1.9 mL/O₂/100 mL) compared with HD (3.5 ± 1.2 mL/O₂/100 mL). Hemodialysis altered cardiopulmonary and metabolic physiology, suggestive of hypoxia. This dysregulated physiology contributed to a greater physiological demand during intradialytic exercise compared with interdialytic exercise. Despite this, intradialytic exercise partly normalized cardiopulmonary physiology during treatment, which may translate to a reduction in the symptoms and side effects of hemodialysis.NEW & NOTEWORTHY This study is the first, to our knowledge, to directly compare cardiopulmonary and metabolic physiology during hemodialysis, intradialytic exercise, and interdialytic exercise. Hemodialysis was associated with increased respiratory exchange ratio, blunted minute ventilation, and impaired O₂ uptake and extraction. We also identified a reduced ventilatory response during intradialytic exercise compared with interdialytic exercise. Impaired arterial-venous O₂ difference during hemodialysis was partly restored by intradialytic exercise. Despite dysregulated cardiopulmonary and metabolic physiology during hemodialysis, intradialytic exercise was well tolerated.

Mechanisms of Cerebral Microvascular Disease in Chronic Kidney Disease

Numerous studies report linkage between chronic kidney disease (CKD) and cerebrovascular disease. This association has been particularly strong for cerebral small vessel disease. Significant findings have emerged from studies ranging from case reports, small case series, and larger cohort investigations. The latter show a relationship between declining renal function, microvascular disease, and cognitive impairment. One troubling aspect has been the relative paucity of mechanistic investigations addressing the CKD-cerebrovascular disease linkage. Nevertheless, mechanistic observations have begun to emerge, showing cerebral microhemorrhage development in animal models of CKD independent of hypertension, an important co-morbidity in clinical studies. Initial cell culture studies show endothelial monolayer disruption by CKD serum, consistent with blood-brain barrier injury. It is noteworthy that CKD serum is known to contain multiple plausible mediators of microvascular injury. Further studies are on the horizon to address the critical question of potential linkage of renal dysfunction with vascular cognitive impairment.

Trace element imbalances in patients undergoing chronic hemodialysis therapy - Report of an observational study in a cohort of Portuguese patients

INTRODUCTION

Patients with end-stage renal disease undergoing hemodialysis therapy are at risk of developing deficiencies of essential trace elements and/or overload of toxic trace elements, both of which may significantly affect their clinical status of. Those imbalances may result from the disease itself but also from the quality of the therapeutic process, namely the hemodialysis process, which has greatly evolved in the last decades. Thus, old observations that have been assumed as very well-proven have been recently questioned. In this case-control study we evaluate the current trace elements status in a group of Portuguese patients under hemodialysis therapy.

MATERIAL AND METHODS

Serum samples from patients (n = 93), collected for the routine periodic control of Al levels, were analyzed for a wide panel of trace elements (Li, Al, Mn, Co, Ni, Cu, Zn, Se, Rb, Sr, Mo, Cd, Ba, Pb) using inductively coupled plasma mass spectrometry technique (hemodialysis patients' group). For comparison purposes, samples of individuals with no evidence of renal disease according to standard laboratory analytical criteria (n = 50) were also analyzed (control group).

RESULTS

The results showed significant differences between the two groups, with higher values in hemodialysis patients group for Al (14.6 vs. 9.5 μg/L), Co, Ni, Sr, Mo (4.5 vs. 1.4 μg/L), Cd (0.058 vs. 0.025 μg/L) and Pb (0.55 vs. 0.30 μg/L); and lower values in hemodialysis patients group for Li (4.0 vs. 75.8 μg/L), Mn, Cu (943.5 vs. 1038.5 μg/L), Zn (943.5 vs. 1038.5 μg/L), Se (71.5 vs. 103.8 μg/L), Rb (202.4 vs. 300.3 μg/L) and Ba (0.65 vs. 8.7 μg/L).

CONCLUSION

This study confirms that hemodialysis patients tend to present significant trace elements imbalances, which may be related to the higher morbidity and mortality observed in this specific patients' group.

Choice of Single-Staged Reconstruction of Nasal Defect

INTRODUCTION

The nasal defect is still a challenge for plastic surgeon now. Many surgical options are reported in previous literatures. There are few studies reported about the 1-staged repair of large nasal defect. In this article, the authors describe the experience about the nasal reconstruction in the last 8 years.

PATIENTS AND METHODS

Fifty-two patients diagnosed with nasal defect were retrospectively examined between 2011 and 2018. All of them performed under local anesthesia and received 1-staged surgical method.

RESULTS

In the authors' patients, the mean size of the defect was 2.16 cm. Nine patients were treated by nasolabial flap, and 30 patients were treated by local flap. The modified auricular composite tissue flap was used in 5 patients. There were no major postoperative complications. All patients were satisfied with aesthetically nasal contours as well as inconspicuous scars when follow-up.

CONCLUSION

Single-staged reconstruction is still considered the first choice for nasal defect. The design of flap depends on the surrounding condition and the size of defect. Locoregional flaps are still considered as an ideal choice for nasal reconstruction in most patients. O-Z flap and modified auricular free flap could be an option for large-sized defect of nasal alar and nasal tip.

The Effects of Synbiotic Supplementation on Metabolic Status in Diabetic Patients Undergoing Hemodialysis: a Randomized, Double-Blinded, Placebo-Controlled Trial

This study was conducted to evaluate the effects of synbiotic supplementation on metabolic profiles in diabetic patients undergoing hemodialysis (HD). This randomized, double-blinded, placebo-controlled clinical trial was performed in 60 diabetic HD patients. Participants were randomly assigned into two groups to receive either synbiotic capsule, containing Lactobacillus acidophilus, Lactobacillus casei, and Bifidobacterium bifidum (2 × 10⁹ CFU/g each), plus 0.8 g/day of inulin (n = 30) or placebo (n = 30) for 12 weeks. Synbiotic supplementation significantly decreased fasting plasma glucose (β - 13.56 mg/dL; 95% CI, - 23.82, - 3.30; P = 0.01), insulin levels (β - 5.49 μIU/mL; 95% CI, - 6.92, - 4.05; P < 0.001), and insulin resistance (β - 2.25; 95% CI, - 3.02, - 1.48; P < 0.001), while increased the quantitative insulin sensitivity check index (β 0.02; 95% CI, 0.01, 0.02; P < 0.001) compared with the placebo. Additionally, synbiotic intake resulted in a significant reduction in high-sensitivity C-reactive protein (β - 2930.48 ng/mL; 95% CI, - 3741.15, - 2119.80; P < 0.001) and malondialdehyde levels (β - 0.60 μmol/L; 95% CI, - 0.99, - 0.20; P = 0.003). Moreover, we found a significant increase in total antioxidant capacity (β 142.99 mmol/L; 95% CI, 61.72, 224.25; P = 0.001) and total glutathione levels (β 131.11 μmol/L; 95% CI, 89.35, 172.87; P < 0.001) in the synbiotic group compared with the placebo group. Overall, synbiotic supplementation for 12 weeks had beneficial effects on glycemic control, biomarkers of inflammation, and oxidative stress in diabetic patients under HD. This study was registered in the Iranian website (www.irct.ir) for registration of clinical trials (http://www.irct.ir: IRCT2017090133941N17). http://www.irct.ir: IRCT2017090133941N17.

The gut microbiota profile of adults with kidney disease and kidney stones: a systematic review of the literature

Background

There is mounting evidence that individuals with kidney disease and kidney stones have an abnormal gut microbiota composition. No studies to date have summarised the evidence to categorise how the gut microbiota profile of these individuals may differ from controls. Synthesis of this evidence is essential to inform future clinical trials. This systematic review aims to characterise differences of the gut microbial community in adults with kidney disease and kidney stones, as well as to describe the functional capacity of the gut microbiota and reporting of diet as a confounder in these studies.

Methods

Included studies were those that investigated the gut microbial community in adults with kidney disease or kidney stones and compared this to the profile of controls. Six scientific databases (CINHAL, Medline, PubMed, Scopus, Web of Science and Cochrane Library), as well as selected grey literature sources, were searched. Quality assessment was undertaken independently by three authors. The system of evidence level criteria was employed to quantitatively evaluate the alteration of microbiota by strictly considering the number, methodological quality and consistency of the findings. Additional findings relating to altered functions of the gut microbiota, dietary intakes and dietary methodologies used were qualitatively summarised.

Results

Twenty-five articles met the eligibility criteria and included data from a total of 892 adults with kidney disease or kidney stones and 1400 controls. Compared to controls, adults with kidney disease had increased abundances of several microbes including Enterobacteriaceae, Streptococcaceae, Streptococcus and decreased abundances of Prevotellaceae, Prevotella, Prevotella 9 and Roseburia among other taxa. Adults with kidney stones also had an altered microbial composition with variations to Bacteroides, Lachnospiraceae NK4A136 group, Ruminiclostridium 5 group, Dorea, Enterobacter, Christensenellaceae and its genus Christensenellaceae R7 group. Differences in the functional potential of the microbial community between controls and adults with kidney disease or kidney stones were also identified. Only three of the 25 articles presented dietary data, and of these studies, only two used a valid dietary assessment method.

Conclusions

The gut microbiota profile of adults with kidney disease and kidney stones differs from controls. Future study designs should include adequate reporting of important confounders such as dietary intake to assist with interpretation of findings.

Beta-glucans in advanced CKD: role in endotoxaemia and inflammation

Background/aims

(1–3)-β-D glucans (BG) are cellular components of yeasts and fungi. Elevated blood levels may be an adjunct in diagnosing invasive fungal infection, though can be high in dialysis patients without fungaemia. BG can also induce false positive signals in endotoxin detection assays (Limulus Amoebocyte Lysate [LAL] assay). We explored the relationship between BG levels, renal impairment, endotoxaemia and inflammation.

Methods

We measured serum BG levels, markers of inflammation and blood endotoxin levels in 20 controls, 20 with stages 1–3 chronic kidney disease (CKD), 20 with stages 4–5 CKD, 15 on peritoneal dialysis (PD) and 60 on haemodialysis (HD). Another 30 patients were studied before and after HD initiation.

Results

BG levels increased with advancing CKD, being highest in HD patients, 22% of whom had elevated levels (> 80 pg/ml). Levels increased significantly following HD initiation. Levels also correlated positively with CRP, TNFα, IL-6 levels, independently of CKD stage. Blood endotoxin was detectable by LAL assays in 10–53% of the CKD cohort, being most prevalent in the HD group, and correlating positively with BG levels. Adding BG blocking agent to the assay reduced endotoxin detection confining it to only 5% of HD patients. Levels of inflammatory markers were higher in those with detectable endotoxin - whether false- or true positives.

Conclusion

BG levels increased with decreasing renal function, being highest in dialysis patients. High BG levels were associated with false positive blood endotoxin signals, and with markers of inflammation, independently of CKD stage. The cause for high BG levels is unknown but could reflect increased gut permeability and altered mononuclear phagocytic system function.

Iron Administration, Infection, and Anemia Management in CKD: Untangling the Effects of Intravenous Iron Therapy on Immunity and Infection Risk

Patients with chronic kidney disease (CKD) are at increased risk for infection, attributable to immune dysfunction, increased exposure to infectious agents, loss of cutaneous barriers, comorbid conditions, and treatment-related factors (eg, hemodialysis and immunosuppressant therapy). Because iron plays a vital role in pathogen reproduction and host immunity, it is biologically plausible that intravenous iron therapy and/or iron deficiency influence infection risk in CKD. Available data from preclinical experiments, observational studies, and randomized controlled trials are summarized to explore the interplay between intravenous iron and infection risk among patients with CKD, particularly those receiving maintenance hemodialysis. The current evidence base, including data from a recent randomized controlled trial, suggests that proactive judicious use of intravenous iron (in a manner that minimizes the accumulation of non-transferrin-bound iron) beneficially replaces iron stores while avoiding a clinically relevant effect on infection risk. In the absence of an urgent clinical need, intravenous iron therapy should be avoided in patients with active infection. Although serum ferritin concentration and transferrin saturation can help guide clinical decision making about intravenous iron therapy, definition of an optimal iron status and its precise determination in individual patients remain clinically challenging in CKD and warrant additional study.

The Efficacy of Prebiotic, Probiotic, and Synbiotic Supplementation in Modulating Gut-Derived Circulatory Particles Associated With Cardiovascular Disease in Individuals Receiving Dialysis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

This systematic review and meta-analyses provide an up-to-date synthesis on the effects of supplementation on circulating levels of toxic metabolites, markers of uremia and inflammation, blood lipids, and other clinical outcomes.

METHODS

Seventeen databases were searched, supplemented with internet and hand searching. Randomized controlled trials of adult end-stage renal-disease individuals receiving either hemodialysis or peritoneal dialysis were eligible. Trials were restricted to those which had administered a prebiotic, probiotic, or synbiotic as an oral supplement. Primary outcomes were measures of circulating endotoxin, indoxyl-sulphate, and p-cresyl sulfate.

RESULTS

Twenty-one trials were eligible (1152 randomized participants), of which 16 trials were considered to have a high risk of bias. The number of trials available for meta-analysis varied for each primary outcome. Synthesized data indicated that supplementation significantly reduced circulating levels of endotoxin (standardized mean difference, -0.61; 95% confidence interval, -1.03 to -0.20; P = .004; I² = 0%), indoxyl-sulphate (-0.34; -0.64 to -0.04; P = .02; I² = 0%), and p-cresyl sulfate (-0.34; -0.61 to -0.07; P = .01; I² = 0%). For secondary outcomes, supplementation significantly reduced gastrointestinal symptoms (-0.54; -1.02 to -0.07; P = .02; I² = 0%).

CONCLUSIONS

Supplementation reduces toxic metabolites associated with cardiovascular disease and mortality in individuals receiving dialysis. However, the majority of trials included were low in quality.

Acute haemodynamic changes during haemodialysis do not exacerbate gut hyperpermeability

INTRODUCTION

The gastrointestinal tract is a potential source of inflammation in dialysis patients. In vitro studies suggest breakdown of the gut barrier in uraemia leading to increased intestinal permeability and it is hypothesised that haemodialysis exacerbates this problem due to mesenteric ischaemia induced by blood volume changes during treatment.

METHOD

The effect of haemodialysis on intestinal permeability was studied in ten haemodialysis patients and compared with five controls. Intestinal permeability was assessed by measuring the differential absorption of four orally administered sugar probes which provides an index of small and whole bowel permeability. A multi-sugar solution (containing lactulose, rhamnose, sucralose and erythritol) was orally administered after an overnight fast. Plasma levels of all sugar probes were measured hourly for 10 h post-administration. In haemodialysis patients, the procedure was carried out twice - once on a non-dialysis day and once immediately after haemodialysis.

RESULTS

Area under curve (AUC) for lactulose:rhamnose (L:R) ratio and sucralose:erythritol (S:E) ratio was similar post-dialysis and on non-dialysis days. AUC for L:R was higher in haemodialysis patients compared with controls (0.071 vs. 0.034, P=0.001), AUC for S:E ratio was not significantly different. Levels of lactulose, sucralose and erythritol were elevated and retained longer in haemodialysis patients compared with controls due to dependence of sugars on kidney function for clearance.

CONCLUSION

We found no significant acute changes in intestinal permeability in relation to the haemodialysis procedure. Valid comparison of intestinal permeability between controls and haemodialysis patients was not possible due to the strong influence of kidney function on sugar levels.

Suppression of Gut Bacterial Translocation Ameliorates Vascular Calcification through Inhibiting Toll-Like Receptor 9-Mediated BMP-2 Expression

Aims

Vascular calcification (VC) is a primary risk factor for cardiovascular mortality in chronic renal failure (CRF) patients; thus, effective therapeutic targets are urgently needed to be explored. Here, we identified the role of intestinal bacterial translocation in CRF-related VC.

Methods and Results

Antibiotic supplementation by oral gavage significantly suppressed intestinal bacterial translocation, CRF-related VC, and aortic osteogenic gene and Toll-like receptor (TLR) gene expression in CRF rats. Furthermore, TLR4 and TLR9 activation in vascular smooth muscle cells (VSMCs) aggravated inorganic phosphate- (Pi-) induced calcification. TLR9 inhibition, but not TLR4 inhibition, by both a pharmacological inhibitor and genetic methods could significantly reduce CRF rats' serum or CRF-induced VC. Interestingly, bone morphogenic protein-2 (BMP-2) levels were increased in the aorta and sera from CRF rats. Increased BMP-2 levels were also observed in VSMCs treated with TLR9 agonist, which was blocked by NF-κB inhibition. Both siRNA knockdown of BMP-2 and NF-κB inhibitor significantly blocked TLR9 agonist-induced VSMC calcification.

Conclusions

Gut bacterial translocation inhibited by oral antibiotic significantly reduces CRF-related VC through inhibition of TLR9/NF-κB/BMP-2 signaling.

The effect of bovine colostrum supplementation on intestinal injury and circulating intestinal bacterial DNA following exercise in the heat

Purpose

Exercise-induced changes in intestinal permeability are exacerbated in the heat. The aim of this study was to determine the effect of 14 days of bovine colostrum (Col) supplementation on intestinal cell damage (plasma intestinal fatty acid-binding protein, I-FABP) and bacterial translocation (plasma bacterial DNA) following exercise in the heat.

Methods

In a double-blind, placebo-controlled, crossover design, 12 males completed two experimental arms (14 days of 20 g/day supplementation with Col or placebo, Plac) consisting of 60 min treadmill running at 70% maximal aerobic capacity (30 °C, 60% relative humidity). Blood samples were collected pre-exercise (Pre-Ex), post-exercise (Post-Ex) and 1 h post-exercise (1 h Post-Ex) to determine plasma I-FABP concentration, and bacterial DNA (for an abundant gut species, Bacteroides).

Results

Two-way repeated measures ANOVA revealed an arm × time interaction for I-FABP (P = 0.005, with greater Post-Ex increase in Plac than Col, P = 0.01: Plac 407 ± 194% of Pre-Ex vs Col, 311 ± 134%) and 1 h Post-Ex (P = 0.036: Plac 265 ± 80% of Pre-Ex vs Col, 229 ± 56%). There was no interaction (P = 0.904) but there was a main effect of arm (P = 0.046) for plasma Bacteroides/total bacterial DNA, with lower overall levels evident in Col.

Conclusion

This is the first investigation to demonstrate that Col can be effective at reducing intestinal injury following exercise in the heat, but exercise responses (temporal pattern) of bacterial DNA were not influenced by Col (although overall levels may be lower).

Hemodynamic Instability during Dialysis: The Potential Role of Intradialytic Exercise

Acute haemodynamic instability is a natural consequence of disordered cardiovascular physiology during haemodialysis (HD). Prevalence of intradialytic hypotension (IDH) can be as high as 20–30%, contributing to subclinical, transient myocardial ischemia. In the long term, this results in progressive, maladaptive cardiac remodeling and impairment of left ventricular function. This is thought to be a major contributor to increased cardiovascular mortality in end stage renal disease (ESRD). Medical strategies to acutely attenuate haemodynamic instability during HD are suboptimal. Whilst a programme of intradialytic exercise training appears to facilitate numerous chronic adaptations, little is known of the acute physiological response to this type of exercise. In particular, the potential for intradialytic exercise to acutely stabilise cardiovascular hemodynamics, thus preventing IDH and myocardial ischemia, has not been explored. This narrative review aims to summarise the characteristics and causes of acute haemodynamic instability during HD, with an overview of current medical therapies to treat IDH. Moreover, we discuss the acute physiological response to intradialytic exercise with a view to determining the potential for this nonmedical intervention to stabilise cardiovascular haemodynamics during HD, improve coronary perfusion, and reduce cardiovascular morbidity and mortality in ESRD.