The uremic toxin indoxyl sulfate exacerbates reactive oxygen species production and inflammation in 3T3-L1 adipose cells

Inflammation and oxidative stress are common features of patients with chronic kidney disease (CKD) and many uremic solutes retained in these patients could be involved in these processes, among which protein-bound solutes such as indoxyl sulfate (IS). White adipose tissue recently gained attention as an important source of inflammation and oxidative stress. To examine the effect of IS on adipocytes, 3T3-L1 adipose cells were incubated with IS to mimic the conditions encountered in uremic patients. Incubation of adipose cells with IS increased reactive oxygen species production generated mainly through activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase since it was prevented by the NADPH oxidase inhibitor apocynin. Exposure to IS furthermore exacerbated the secretion of tumor necrosis factor-α and interleukin-6 by adipose cells. This inflammatory response was prevented by NADPH oxidase inhibition pinpointing the pivotal role of intracellular oxidative stress. IS induces adipocyte perturbation and promotes inflammatory state mainly through induction of oxidative stress. IS, a uremic toxin, accumulates in CKD patients could, therefore, be an important mediator of adipocyte dysfunction in these patients.

Is there interaction between gut microbial profile and cardiovascular risk in chronic kidney disease patients?

AIM

To evaluate the gut microbial profile in chronic kidney disease (CKD) patients and evaluate the possible relationship with inflammation and cardiovascular risk.

PATIENTS & METHODS

Markers inflammation plasma and bacterial community profile (denaturing gradient gel electrophoresis) were analyzed.

RESULTS

The average number of bands was not different in healthy individuals and CKD patients. The number of bands was negatively associated with plasma levels of VCAM-1 in patients. Flavobacteriaceae bacterium and Listeria monocytogenes were found in patients and Lachnospiraceae bacterium and Butyrivibrio crossotus in healthy individuals.

CONCLUSION

Although CKD patients did not present altered gut microbial profile, the sequencing of bands suggested a different microbiota between groups. The result suggests a possible relationship between gut microbiota and cardiovascular risk in CKD patients.

NRF2 and NF-κB mRNA expression in chronic kidney disease: a focus on nondialysis patients

PURPOSE

To evaluate nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappaB (NF-κB) mRNA expression in nondialysis chronic kidney disease (CKD) patients, comparing with data from hemodialysis (HD) patients and healthy individuals.

METHODS

Twenty nondialysis CKD patients (62.0 ± 8.1 years old, 11 men, estimated glomerular filtration rate of 36.8 ± 13.6 mL/min/1.73 m(2)), twenty HD patients (55.0 ± 15.2 years old, 13 men, and dialysis vintage of 76.5 ± 46.3 months) and eleven healthy individuals (50.9 ± 8.0 years old, 6 men) were enrolled in the study. The peripheral blood mononuclear cells were isolated and processed for the evaluation of expression of NF-κB and Nrf2 by quantitative real-time polymerase chain reaction.

RESULTS

Nrf2 mRNA expression was significantly higher in nondialysis (1.12 ± 0.57) when compared to HD patients (0.58 ± 0.35, p = 0,006) but similar to healthy individuals (1.13 ± 0.64). Inversely, NF-κB mRNA expression was lower in nondialysis (1.21 ± 0.71) when compared to HD patients (2.08 ± 0.7, p < 0.0001) and similar to healthy individuals (1.04 ± 0.22). Nrf2 mRNA was positively correlated with NF-κB mRNA expression in nondialysis CKD patients (r = 0.52, p = 0.02) and healthy individuals (r = 0.77, p < 0.006). By contrast, Nrf2 mRNA was inversely correlated with NF-κB mRNA expression (r = -0.65, p = 0.003) in HD patients.

CONCLUSION

Nondialysis CKD patients may conserve regular homeostatic balance between Nrf2 and NF-κB expressions, being comparable to healthy individuals. However, HD patients seem to have Nrf2 downregulation and NF-κB upregulation. Thus, the association among Nrf2 and NF-κB expressions and nutritional status, kidney disease progression or immune deregulation deserve further investigation.

EFFECT OF SELENIUM SUPPLEMENTATION VIA BRAZIL NUT (BERTHOLLETIA EXCELSA, HBK) ON THYROID HORMONES LEVELS IN HEMODIALYSIS PATIENTS: A PILOT STUDY

BACKGROUND

thyroid function depends on trace mineral selenium (Se), being at the active center of the iodothyronine deiodinase that catalyzes the conversion of the thyroxine (T4) to the active form of thyroid hormone, triiodothyronine (T3). Hemodialysis (HD) patients have reduced T3 levels partly due to impaired hormonal conversion that can be related to Se deficiency, a common feature in these patients. This study evaluated the effect of Brazil nuts (richest Se source) on thyroid hormone levels in HD patients.

METHODS

we performed an uncontrolled intervention with 40 HD patients (53.3 ± 16.1 yrs, dialysis vintage 62.0 (8.0 - 207.0) months) that received one nut (≈5g, average 58.1 μg Se/g) per day for three months. Se plasma levels were determined by atomic absorption spectrophotometry with hydride generation and, serum T3, free T4 (FT4), TSH as well as glutathione peroxidase (GPx) activity were measured by ELISA.

RESULTS

all patients were Se deficient and presented low T3 levels at baseline. After intervention, Se plasma levels (from 17.6 ± 11.6 to 153.4 ± 86.1 μg/L), GPx activity (from 33.7 ± 5.9 to 41.4 ± 11.2 nmol/min/mL), T3 (from 27.3 ± 8.8 to 50.2 ± 4.8ng/dL) and FT4 levels (0.87 ± 0.2 to 0.98 ± 0.4 ng/dL) were significantly increased (p < 0.05), while TSH levels were reduced (from 2.17 ± 1.3 to 1.96 ± 1.1 uUI/mL), but not significantly.

CONCLUSION

in conclusion, increasing Se levels via Brazil nut supplementation was associated with improvement in thyroid hormone levels in HD patients, although the amount of Se given was not able to restore T3 to normal levels.

Effects of acute resistance exercise on acyl-ghrelin and obestatin levels in hemodialysis patients: a pilot study

Chronic physical exercises may be beneficial to modulate appetite hormones as acyl-ghrelin (orexigenic) and obestatin (anorexigenic) in chronic kidney disease (CKD) patients; however, there are no data about the effects of acute exercises on these hormones. Thus, the aim of the present study was to assess the effect of acute resistance exercise on appetite hormones (acyl-ghrelin and obestatin) of patients undergoing hemodialysis (HD). Twenty-five patients (44.7 ± 12.9 years, 68% women) on regular HD program were enrolled into two groups, 16 patients performed exercises and 9 patients comprised the control group. The patients performed the exercises in both lower limbs with ankle-cuffs and elastic bands, 30 min after the initiation of hemodialysis session. Blood samples of both the groups were drawn in the morning before and after 30 min with exercise session (exercise group) and, before and after the same time without exercise (control group). Acyl-ghrelin and obestatin plasma levels were measured using an enzyme immunometric assay. Acyl-ghrelin plasma levels did not change in both the groups. However, when stratified by gender the acyl-ghrelin increased significantly right after exercise in men [32.1 pg/mL (25.6-41.2) to 46.0 pg/mL (39.0-59.5)] (p = 0.04). Obestatin plasma levels reduced after a single bout of exercise and changes remained significantly when the sample was stratified by gender. There was no change in obestatin plasma levels in control group. A single bout of resistance exercise seems to modulate the levels of appetite hormones in HD patients.

Gut microbiota and inflammation in chronic kidney disease patients

Inflammation is a multifactorial phenotype that in chronic kidney disease is associated with adverse patient outcomes. Recently, alterations in gut microbiota composition and intestinal barrier have been associated with inflammation and oxidative stress in CKD patients. Vanholder and Glorieux recently critically reviewed [Clin Kidney J (2015) 8 (2): 168-179] the current understanding of the role of gut microbiota in the production of uraemic toxins and the therapeutic implications. Where do we stand now? The basic mechanisms of the gut-kidney crosstalk must still be clarified. In addition, the efficacy and safety of therapeutic strategies to modulate the gut microbiota in order to decrease uraemic toxin production and inflammation in chronic kidney disease should be evaluated. Finally, an impact of such strategies on hard outcomes should be demonstrated before incorporation into routine clinical practice.

Effects of Uremic Toxins from the Gut Microbiota on Bone: A Brief Look at Chronic Kidney Disease

Patients with chronic kidney disease (CKD) frequently have mineral and bone disorders (CKD-MBD) that are caused by several mechanisms. Recent research has suggested that uremic toxins from the gut such as p-cresyl sulfate (PCS) and indoxyl sulfate (IS) could also be involved in the development of bone disease in patients with CKD. IS and PCS are produced by microbiota in the gut, carried into the plasma bound to serum albumin, and are normally excreted into the urine. However, in patients with CKD, there is an accumulation of high levels of these uremic toxins. The exact mechanisms of action of uremic toxins in bone disease remain unclear. The purpose of this brief review is to discuss the link between uremic toxins (IS and PCS) and bone mineral disease in chronic kidney disease.

Effect of acute intradialytic strength physical exercise on oxidative stress and inflammatory responses in hemodialysis patients

Background

Oxidative stress and inflammation are common findings in chronic kidney disease (CKD) patients, and they are directly related to the increased risk of developing cardiovascular disease, which is the major cause of death in these patients, particularly for those undergoing hemodialysis (HD). Strength physical exercise is a new therapeutic approach to reduce these complications in CKD patients. Following this, the purpose of this study was to assess the effect of acute intradialytic strength physical exercise on oxidative stress and inflammatory responses in HD patients.

Methods

Sixteen HD patients were studied (11 women; 44.4±14.6 years; body mass index 23.3±4.9 kg/m²; 61.6±43.1 months of dialysis) and served as their own controls. Acute (single session) intradialytic physical exercise were performed at 60% of the one-repetition maximum test for three sets of 10 repetitions for four exercise categories in both lower limbs during 30 minutes. Blood samples were collected on two different days at exactly the same time (30 minutes and 60 minutes after initiating the dialysis—with and without exercise). Antioxidant enzymes activity [superoxide dismutase (SOD), catalase, and glutathione peroxidase], lipid peroxidation marker levels (malondialdehyde), and inflammatory marker levels (high-sensitivity C-reactive protein) were determined.

Results

SOD plasma levels were significantly reduced after acute physical exercise from 244.8±40.7 U/mL to 222.4±28.9 U/mL (P=0.03) and, by contrast, increased on the day without exercise (218.2±26.5 U/mL to 239.4±38.6 U/mL, P=0.02). There was no alteration in plasma catalase, glutathione peroxidase, malondialdehyde, or high-sensitivity C-reactive protein levels in on either day (with or without exercise). Additionally, there was no association between these markers and clinical, anthropometric, or biochemical parameters.

Conclusion

These data suggest that acute intradialytic strength physical exercise was unable to reduce oxidative stress and inflammation, and in addition, it seems to reduce plasma SOD levels, which could exacerbate the oxidative stress in HD patients.

A follow-up study of the chronic kidney disease patients treated with Brazil nut: focus on inflammation and oxidative stress

Brazil nut is the richest known food source of selenium. The supplementation with Brazil nut during 3 months was effective in reducing oxidative stress and inflammation in hemodialysis (HD) patients. However, there are no available data on the antioxidant effect after that supplementation. The objective of this work was to determine if the beneficial effects of one Brazil nut supplementation per day during 3 months for the HD patients could be sustained after 12 months. Twenty-nine HD patients (58.6 % men, 51.0 ± 3.3 years) from RenalCor Clinic, Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study had finished. The plasma levels of antioxidant substances as selenium, glutathione peroxidase (GPx), 8-isoprostane, 8-hydroxy-2-deoxyguanosine (8-OHdG) and cytokines (tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6)) were determined before, after 3 months of supplementation and after 12 months. After 3-months supplementation, cytokines, 8-OHdG and 8-isoprostane plasma levels have decreased and the activity of GPx and selenium plasma levels have increased significantly. Additionally, after 12 months, the values of 8-isoprostane, 8-OHdG and cytokines increased and the activity of GPx and selenium plasma levels decreased significantly. The levels of oxidative stress and inflammation biomarkers after 12 months increased compared to the basal levels. Consequently, it is necessary to motivate patients to adopt different dietary intake patterns.

Role of altered intestinal microbiota in systemic inflammation and cardiovascular disease in chronic kidney disease

The normal intestinal microbiota plays a major role in the maintenance of health and disease prevention. In fact, the alteration of the intestinal microbiota has been shown to contribute to the pathogenesis of several pathological conditions, including obesity and insulin resistance, among others. Recent studies have revealed profound alterations of the gut microbial flora in patients and animals with chronic kidney disease (CKD). Alterations in the composition of the microbiome in CKD may contribute to the systemic inflammation and accumulation of gut-derived uremic toxins, which play a central role in the pathogenesis of accelerated cardiovascular disease and numerous other CKD-associated complications. This review is intended to provide a concise description of the potential role of the CKD-associated changes in the gut microbiome and its potential role the pathogenesis of inflammation and uremic toxicity. In addition, the potential efficacy of pre- and pro-biotics in the restoration of the microbiome is briefly described.

Systemic inflammation and oxidative stress in hemodialysis patients are associated with down-regulation of Nrf2

BACKGROUND

Oxidative stress and inflammation are common features and the main mediators of progression of chronic kidney disease (CKD) and its cardiovascular complications. Under normal conditions, oxidative stress activates the transcription factor, nuclear factor E2-related factor 2 (Nrf2), which is the master regulator of genes encoding antioxidant and detoxifying enzymes and related proteins. The available data on expression of Nrf2 and its key target gene products in CKD patients is limited. We therefore investigated this topic in a group of CKD patients on hemodialysis.

METHODS

Twenty adult hemodialysis (HD) patients (aged 54.9 ± 15.2 years) and 11 healthy individuals (aged 50.9 ± 8.0 years) were enrolled. Peripheral blood mononuclear cells (PBMC) were isolated and processed for expression of nuclear factor-κB (NF-κB), Nrf2, heme oxygenase-1 and NADPH: quinoneoxidoreductase 1 (NQO1) by quantitative real-time polymerase chain reaction and western blot analysis. Plasma malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-α) levels were measured.

RESULTS

Peripheral blood mononuclear cells from HD patients had significantly lower NQO1 and Nrf2 mRNA expressions (0.58 ± 0.35 vs. 1.13 ± 0.64, p = 0.005), and significantly higher NF-κB expression (2.18 ± 0.8 vs. 1.04 ± 0.22, p = 0.0001) compared to the healthy individuals. The NF-κB expression was inversely correlated with Nrf2 levels (r = -0.54, p < 0.01) in CKD patients. Plasma MDA and TNF-α levels were significantly higher in CKD patients than in the healthy individuals.

CONCLUSIONS

Up-regulation of NFκB in the CKD patients' PBMC is coupled to down-regulation of Nrf2 and NQO1 expression. These observations are consistent with recent findings in CKD animals and point to the contribution of the impaired Nrf2 system in the pathogenesis of oxidative stress and inflammation in hemodialysis patients.

Fructose intake: is there an association with uric acid levels in nondialysis-dependent chronic kidney disease patients?

INTRODUCTION

Fructose intake has increased dramatically in consequence of the consumption of fructose-based sweetened foods and beverages. Research suggests that high fructose intake has a strong association with uric acid (UA) levels and worse prognosis of chronic kidney disease (CKD).

OBJECTIVE

The aim of this study was to investigate the influence of fructose intake on plasma UA levels in nondialysis- dependent CKD patients.

METHODS

Fifty-two patients on stages 3-5 (64.2 ± 9.6 years, 24 men, glomerular filtration rate of 30.5 ± 10.3 ml/ min) were divided into two groups: high fructose intake (>50 g/d, n=29, 61.7 ± 9.3 years) and low fructose intake (