Association between uremic toxins and depression in patients with chronic kidney disease undergoing maintenance hemodialysis

The Role of the Gut Microbiota in Complications among Hemodialysis Patients

The composition of the gut microbiota varies among end-stage renal disease (ESRD) patients on the basis of their mode of renal replacement therapy (RRT), with notably more pronounced dysbiosis occurring in those undergoing hemodialysis (HD). Interventions such as dialysis catheters, unstable hemodynamics, strict dietary restrictions, and pharmacotherapy significantly alter the intestinal microenvironment, thus disrupting the gut microbiota composition in HD patients. The gut microbiota may influence HD-related complications, including cardiovascular disease (CVD), infections, anemia, and malnutrition, through mechanisms such as bacterial translocation, immune regulation, and the production of gut microbial metabolites, thereby affecting both the quality of life and the prognosis of patients. This review focuses on alterations in the gut microbiota and its metabolites in HD patients. Additionally, understanding the impact of the gut microbiota on the complications of HD could provide insights into the development of novel treatment strategies to prevent or alleviate complications in HD patients.

Comparison of depression and suicide between dialysis and kidney transplant recipients in Korea: a nationwide population study

Background

Kidney transplantation (KT) improves physical and psychological prognoses for patients with end-stage kidney disease (ESKD). However, few comparative studies have examined depression and suicide rates among patients with ESKD treated with dialysis versus KT.

Methods

Data on 21,809 patients with ESKD were extracted from the Korean National Health Insurance Service database, extending from January 2002 to December 2018. These patients exhibited no history of depression or insomnia before starting renal replacement therapy. Outcomes were compared between dialysis and KT recipients using 1:2 propensity score matching (PSM).

Results

Of the patients, 17,649 received dialysis (hemodialysis, 15,537; peritoneal dialysis, 2,112), while 4,160 underwent KT. Of those on dialysis, 45.04% (7,949) experienced insomnia, compared to 25.72% (1,070) of KT recipients (P<0.001). Depression was more frequent among dialysis recipients (22.77%, 4,019) than KT recipients (8.61%, 358; P<0.001). Additionally, those on dialysis had a higher incidence of suicide (0.19%, 33) than recipients of KT (0.12%, 5; P=0.047). After PSM, the hazard ratio (HR) for depression in patients on dialysis compared to KT recipients was 1.76 (95% confidence interval [CI], 1.56-1.99). In subgroup analysis, the relative likelihood of depression among dialysis recipients was particularly high for residents of urban areas (HR, 2.10; 95% CI, 1.80-2.44) and patients under 65 years old (HR, 1.82; 95% CI, 1.62-2.09).

Conclusions

KT recipients exhibit a lower suicide rate than patients on dialysis. Furthermore, KT is associated with a lower prevalence of depression among Korean patients with ESKD, particularly urban residents and individuals under 65 years old.

Body Composition Parameters Correlate to Depression Symptom Levels in Patients Treated with Hemodialysis and Peritoneal Dialysis

The aim of this study was to investigate the determinants of depression and nutritional status and their associations in patients treated with hemodialysis (HD) and peritoneal dialysis (PD) and the differences according to the type of treatment. There were fifty-three patients treated with maintenance HD and twenty patients treated with PD enrolled in this cross-sectional study. Body composition, anthropometric parameters, and clinical and laboratory parameters were collected for each participant. Depression was assessed with the Beck Depression Inventory II (BDI-II) and risk of malnutrition with the Malnutrition Inflammation Score (MIS). The results suggest a positive association between the level of depression and the percentage of fat mass and obesity parameters in PD and HD participants. Muscle mass and fat-free mass in HD, phase angle (PhA), and serum albumin levels in PD were negatively associated with the value of BDI-II. Participants treated with HD were found to have higher levels of pessimism and loss of interest in sex compared with PD. There is a need to integrate multidisciplinary psychological and nutritional assessment into the usual care of dialysis patients.

Psychosocial Burden of Itch among Renal Transplant Recipients

Itch is the most common symptom of chronic dermatoses. Moreover, itch may be associated with systemic disorders. Chronic kidney disease—associated itch (CKD-aI) may affect up to 20% of renal transplant recipients (RTR). The aim of the study was to assess psychosocial burden of itch in RTR. The study was performed on a group of 129 RTR, out of which 54 (41.9%) experienced itch in the previous 3 days. A specially designed questionnaire assessing anxiety, depression, stigmatization, and quality of life was used. Results: Patients suffering from itch in the previous 3 days achieved significantly higher scores in GAD-7 (p < 0.001), BDI (p < 0.001), HADS total score (p < 0.001), HADS Depression (p = 0.004), and HADS Anxiety (p < 0.001). Severity of itch correlated positively with HADS, stigmatization scale, and GAD-7. Itch in RTR was associated with higher incidence of depression assessed with BDI (OR 3.7). Moreover, higher prevalence of anxiety was found among patients suffering from CKD-aI, assessed with HADS A and GAD-7 (OR 2.7 and OR 4.8, respectively) The results of our study clearly demonstrate that itch among RTR is a significant burden. Higher prevalence of depression and anxiety in this groups indicate the necessity of addressing itch relief as a part of holistic approach to patients after renal transplantation.

Chronic kidney disease and neurological disorders: are uraemic toxins the missing piece of the puzzle?

Chronic kidney disease (CKD) perturbs the crosstalk with others organs, with the interaction between the kidneys and the heart having been studied most intensively. However, a growing body of data indicates that there is an association between kidney dysfunction and disorders of the central nervous system. In epidemiological studies, CKD is associated with a high prevalence of neurological complications, such as cerebrovascular disorders, movement disorders, cognitive impairment and depression. Along with traditional cardiovascular risk factors (such as diabetes, inflammation, hypertension and dyslipidaemia), non-traditional risk factors related to kidney damage (such as uraemic toxins) may predispose patients with CKD to neurological disorders. There is increasing evidence to show that uraemic toxins, for example indoxyl sulphate, have a neurotoxic effect. A better understanding of factors responsible for the elevated prevalence of neurological disorders among patients with CKD might facilitate the development of novel treatments. Here, we review (i) the potential clinical impact of CKD on cerebrovascular and neurological complications, (ii) the mechanisms underlying the uraemic toxins' putative action (based on pre-clinical and clinical research) and (iii) the potential impact of these findings on patient care.

p-Cresol Sulfate Caused Behavior Disorders and Neurodegeneration in Mice with Unilateral Nephrectomy Involving Oxidative Stress and Neuroinflammation

Protein-bound uremic toxins, such as p-cresol sulfate (PCS), can be accumulated with declined renal function and aging and is closely linked with central nervous system (CNS) diseases. In the periphery, PCS has effects on oxidative stress and inflammation. Since oxidative stress and inflammation have substantial roles in the pathogenesis of neurological disorders, the CNS effects of PCS were investigated in unilateral nephrectomized C57/BL/6 mice. Unlike intact mice, unilateral nephrectomized mice showed increased circulating levels of PCS after exogenous administration. Upon PCS exposure, the unilateral nephrectomized mice developed depression-like, anxiety-like, and cognitive impairment behaviors with brain PCS accumulation in comparison with the nephrectomy-only group. In the prefrontal cortical tissues, neuronal cell survival and neurogenesis were impaired along with increased apoptosis, oxidative stress, and neuroinflammation. Circulating brain-derived neurotrophic factors (BDNF) and serotonin were decreased in association with increased corticosterone and repressor element-1 silencing transcription factor (REST), regulators involved in neurological disorders. On the contrary, these PCS-induced changes were alleviated by uremic toxin absorbent AST-120. Taken together, PCS administration in mice with nephrectomy contributed to neurological disorders with increased oxidative stress and neuroinflammation, which were alleviated by PCS chelation. It is suggested that PCS may be a therapeutic target for chronic kidney disease-associated CNS diseases.

Microbiota issue in CKD: how promising are gut-targeted approaches?

In chronic kidney disease (CKD), the progressive decline in the renal excretory function leads to accumulation of urea and toxins in the blood. The CKD-associated dysbiosis of gut microbiota further contributes to uremia by increasing intestinal toxins production. Gut microbiota is involved in a complex network of human organs, mediated by microbial metabolites: in CKD, gut-heart and gut-brain axes may have a role in increased cardiovascular risk and neuropsychiatric disorders. While the cardiovascular toxicity of some microbial molecules is well known, their presumptive neurotoxicity needs to be confirmed by specific studies. In this review, we describe gut-heart and gut-brain axes in CKD, with an overview of the experimental and human studies characterizing CKD-associated gut microbiota, and we discuss the benefits coming from new approaches aimed at gut manipulation. Microbiota metabolism is emerging as a modifiable non-traditional risk factor in nephrology. In order to take advantage of this issue, it is necessary to consider the microbiota manipulation as part of the nutritional management of CKD. Integrating the low-protein nutritional approach with prebiotic, probiotic and synbiotic supplementation is a promising tool to control disease progression and comorbidities, though an extensive validation in large-scale clinical trials is still required.

Prevalence of depression and suicidal ideation increases proportionally with renal function decline, beginning from early stages of chronic kidney disease

Depression and suicidal ideation are prevalent mental health problems in patients with chronic kidney disease (CKD. However, the association between mental health problems and kidney disease has been investigated in severe cases only. Thus, this study evaluated the relationship between mental health problems and renal function in a community-based prospective cohort study comprising patients with mild to moderate kidney disease. A total of 44,938 participants who were participated in Korean National Health and Nutrition Examination Survey IV, V, and VI from 2007 to 2014 were enrolled. Estimated glomerular filtration rate (eGFR) was calculated using the CKD Epidemiology Collaboration equation. The study outcome was the prevalence of depression and suicidal ideations assessed by self-reporting surveys. Logistic regression analysis was performed to evaluate the relationship between renal function and outcomes. The mean age of the study subjects was 49.2 ± 16.6 years, and the mean eGFR was 94.0 mL/min/1.73 m. The prevalence of depression and suicidal ideation increased with decreasing eGFR. Multivariate logistic regression analysis showed that the risk of depression increased in subjects with eGFR <45 mL/min/1.73 m [odds ratio (OR) 1.47; 95% confidence interval (CI) 1.09-1.98]. The risk of suicidal ideation gradually increased in groups with eGFR <90 mL/min/1.73 m (OR, 1.11; 95% CI, 1.03-1.20), even after adjustments for confounding variables. In conclusion, depression and suicidal ideation are related closely with renal dysfunction. The risk of having depression and suicidal ideation increased even in patient with mild renal dysfunction. Therefore, evaluation and management strategies regarding mental health problems should be taken into account throughout all stages of CKD.

Timing of Dialysis Initiation: What Has Changed Since IDEAL?

The optimal timing of initiation of maintenance dialysis in patients with end-stage renal disease currently is unknown. This transition period is one of exceptionally high vulnerability for patients; annual mortality rates in stage 5 chronic kidney disease through the first year of maintenance dialysis exceed 20%. The results of the Initiating Dialysis Early and Late (IDEAL) study, a randomized trial that tested the impact of dialysis initiation at two different levels of kidney function on outcomes, showed no significant difference in survival or other patient-centered outcomes between treatment groups. These data have challenged the established paradigm of using estimates of glomerular filtration as the primary guide for initiation of maintenance dialysis and illustrate the compelling need for research to optimize the high-risk transition period from chronic kidney disease to end-stage renal disease. This article reviews the findings of the IDEAL study and summarizes the evolution of research findings, updated clinical practice guidelines, and trends in dialysis initiation practices in the United States in the 6 years since the publication of the results from IDEAL. Complementary strategies to the use of estimated glomerular filtration rate to optimally time the initiation of maintenance dialysis and potentially improve patient-centered outcomes also are considered.

Diurnal and Long-term Variation in Plasma Concentrations and Renal Clearances of Circulating Markers of Kidney Proximal Tubular Secretion

BACKGROUND

The renal proximal tubule is essential for removing organic solutes and exogenous medications from the circulation. We evaluated diurnal, prandial, and long-term biological variation of 4 candidate endogenous markers of proximal tubular secretion.

METHODS

We used LC-MS to measure plasma and urine concentrations of hippurate (HA), cinnamoylglycine (CMG), indoxyl sulfate (IS), and p-cresol sulfate (PCS) in 25 healthy adults. We measured plasma concentrations of secreted solutes at 13 time points over a 24-h period, and again after 2 weeks and 14 weeks of follow-up. We further measured 24-h renal clearances of secreted solutes at baseline, 2 weeks, and 14 weeks.

RESULTS

Plasma concentrations of secreted solutes varied over the 24-h baseline period. Diurnal variation was greatest for HA, followed by CMG, IS, and PCS. Plasma concentrations of HA (P = 0.002) and IS (P = 0.02), but not CMG and PCS, increased significantly following meals. Long-term intraindividual biological variation (CV_I) in plasma concentrations of secreted solutes over 14 weeks varied from 21.8% for IS to 67.3% for PCS, and exceeded that for plasma creatinine (CV_I, 7.1%). Variation in 24-h renal clearances was similar among the secreted solutes [intraindividual variation (CV_A+I), 33.6%-47.3%] and was lower using pooled plasma samples from each study visit.

CONCLUSIONS

Plasma concentrations of HA, CMG, IS, and PCS fluctuate within individuals throughout the day and over weeks. Renal clearances of these secreted solutes, which serve as estimates of renal proximal tubule secretion, are also subject to intraindividual biological variation that can be improved by additional plasma measurements.

Tryptophan metabolism, its relation to inflammation and stress markers and association with psychological and cognitive functioning: Tasmanian Chronic Kidney Disease pilot study

Background

Adults with chronic kidney disease (CKD) exhibit alterations in tryptophan metabolism, mainly via the kynurenine pathway, due to higher enzymatic activity induced mainly by inflammation. Indoles produced by gut-microflora are another group of tryptophan metabolites related to inflammation and conditions accompanying CKD. Disruptions in tryptophan metabolism have been associated with various neurological and psychological disorders. A high proportion of CKD patients self-report symptoms of depression and/or anxiety and decline in cognitive functioning. This pilot study examines tryptophan metabolism in CKD and explores associations with psychological and cognitive functioning.

Methods

Twenty-seven adults with CKD were part of 49 patients recruited to participate in a prospective pilot study, initially with an eGFR of 15–29 mL/min/1.73 m². Only participants with viable blood samples and complete psychological/cognitive data at a 2-year follow-up were included in the reported cross-sectional study. Serum samples were analysed by Liquid Chromatography coupled to Mass Spectrometry, for tryptophan, ten of its metabolites, the inflammation marker neopterin and the hypothalamic–pituitary–adrenal (HPA) axis marker cortisol.

Results

The tryptophan breakdown index (kynurenine / tryptophan) correlated with neopterin (Pearson R = 0.51 P = 0.006) but not with cortisol. Neopterin levels also correlated with indoxyl sulfate (R = 0.68, P < 0.0001) and 5 metabolites of tryptophan (R range 0.5–0.7, all P ≤ 0.01), which were all negatively related to eGFR (P < 0.05). Higher levels of kynurenic acid were associated with lower cognitive functioning (Spearman R = −0.39, P < 0.05), while indole-3 acetic acid (IAA) was correlated with anxiety and depression (R = 0.52 and P = 0.005, R = 0.39 and P < 0.05, respectively).

Conclusions

The results of this preliminary study suggest the involvement of inflammation in tryptophan breakdown via the kynurenine pathway, yet without sparing tryptophan metabolism through the 5-HT (serotonin) pathway in CKD patients. The multiple moderate associations between indole-3 acetic acid and psychological measures were a novel finding. The presented pilot data necessitate further exploration of these associations within a large prospective cohort to assess the broader significance of these findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0387-3) contains supplementary material, which is available to authorized users.

Depression, quality of life, and body composition in patients with end-stage renal disease: a cohort study

Objective:

To prospectively evaluate depressive symptoms, nutritional status, and quality of life (QoL) and search for possible associations in patients with end-stage renal disease undergoing hemodialysis.

Methods:

A cohort study of 104 adult patients with end-stage renal disease undergoing hemodialysis was conducted. Anthropometric, clinical, and biochemical variables were evaluated after a midweek hemodialysis session. The participants’ body composition was assessed by direct segmental multi-frequency bioimpedance analysis. The WHOQOL-Bref questionnaire was used to evaluate QoL. Participants were separated into two groups - depressive symptoms and no depressive symptoms - at inclusion and evaluated annually for 2 years thereafter using the Beck Depression Inventory. Survival analysis used the Kaplan-Meier method and Cox regression analysis for the goodness of fit of associated factors. All-cause mortality was the outcome of interest.

Results:

Participants’ mean age was 55.3±15.6 years, 60% were male, and the median time on hemodialysis was 17.5 (8.0-36.8) months. Thirty-two patients had depressive symptoms and a significantly lower QoL compared with the 72 patients in the no depressive symptoms group. The fitted outcome model showed that lean body mass had a protective effect against all-cause mortality (hazard ratio [HR] = 0.89; 95%CI 0.80-0.99; p = 0.038).

Conclusion:

Depressive symptoms were highly prevalent in the cohort, and correlated with the physical and psychological components of the QoL life questionnaire, as well as with C-reactive protein and phosphorus levels. Lean body mass was protective for the assessed outcome.

Risk of major depression in patients with chronic renal failure on different treatment modalities: A matched-cohort and population-based study in Taiwan

The influence of different treatment modalities on the risk of developing major depression in patients with chronic renal failure (CRF) is not well understood. We aimed to explore the incidence of major depression among patients with CRF who were on different dialysis modalities, who had received renal transplantation (RT), and those who had not yet received any of the aforementioned renal replacement therapies. We conducted a population-based retrospective cohort study using a national health insurance research database. This study investigated 89,336 study controls, 17,889 patients with chronic kidney disease on conservative treatment, 3823 patients on hemodialysis (HD), 351 patients on peritoneal dialysis (PD), and 322 patients who had RT. We followed all individuals until the occurrence of major depression or the date of loss to follow-up. The PD group had the highest risk (hazard ratio [HR] 2.43; 95% confidence interval [CI] 1.26-4.69), whereas the RT group had the lowest risk (HR 0.18; 95% CI 0.03-1.29) of developing major depression compared with the control group. Patients initiated on PD had a higher risk of developing major depression than patients initiated on HD (pairwise comparison: HR 2.20; 95% CI 1.09-4.46). Different treatment modalities are associated with different risks of developing major depression in patients with CRF. Among renal replacement therapies, patients who have had RT have the lowest risk of developing major depression. Patients who initiate renal therapy on PD may have a higher risk of major depression compared with patients who initiate renal therapy on HD.

Impact of prenatal environmental stress on cortical development

Prenatal exposure of the developing brain to various types of environmental stress increases susceptibility to neuropsychiatric disorders such as autism, attention deficit hyperactivity disorder and schizophrenia. Given that even subtle perturbations by prenatal environmental stress in the cerebral cortex impair the cognitive and memory functions, this review focuses on underlying molecular mechanisms of pathological cortical development. We especially highlight recent works that utilized animal exposure models, human specimens or/and induced Pluripotent Stem (iPS) cells to demonstrate: (1) molecular mechanisms shared by various types of environmental stressors, (2) the mechanisms by which the affected extracortical tissues indirectly impact the cortical development and function, and (3) interaction between prenatal environmental stress and the genetic predisposition of neuropsychiatric disorders. Finally, we discuss current challenges for achieving a comprehensive understanding of the role of environmentally disturbed molecular expressions in cortical maldevelopment, knowledge of which may eventually facilitate discovery of interventions for prenatal environment-linked neuropsychiatric disorders.

Neurological disorders in a murine model of chronic renal failure

Cardiovascular disease is highly prevalent in patients with chronic renal failure (CRF). However, data on the impact of CRF on the cerebral circulatory system are scarce—despite the fact that stroke is the third most common cause of cardiovascular death in people with CRF. In the present study, we examined the impact of CRF on behavior (anxiety), recognition and ischemic stroke severity in a well-defined murine model of CRF. We did not observe any significant increases between CRF mice and non-CRF mice in terms of anxiety. In contrast, CRF mice showed lower levels of anxiety in some tests. Recognition was not impaired (vs. controls) after 6 weeks of CRF but was impaired after 10 weeks of CRF. Chronic renal failure enhances the severity of ischemic stroke, as evaluated by the infarct volume size in CRF mice after 34 weeks of CRF. Furthermore, neurological test results in non-CRF mice tended to improve in the days following ischemic stroke, whereas the results in CRF mice tended to worsen. In conclusion, we showed that a murine model of CRF is suitable for evaluating uremic toxicity and the associated neurological disorders. Our data confirm the role of uremic toxicity in the genesis of neurological abnormalities (other than anxiety).

Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: part III - convergence toward clinical trials

Rapid scientific and technological advances have allowed for a more detailed understanding of the relevance of intestinal microbiota, and the entire body-wide microbiome, to human health and well-being. Rodent studies have provided suggestive evidence that probiotics (e.g. lactobacillus and bifidobacteria) can influence behavior. More importantly, emerging clinical studies indicate that the administration of beneficial microbes, via supplementation and/or fecal microbial transplant (FMT), can influence end-points related to mood state (glycemic control, oxidative status, uremic toxins), brain function (functional magnetic resonance imaging fMRI), and mental outlook (depression, anxiety). However, despite the advances in the area of gastro-biological psychiatry, it becomes clear that there remains an urgent need to explore the value of beneficial microbes in controlled clinical investigations. With the history explored in this series, it is fair to ask if we are now on the cusp of major clinical breakthroughs, or are we merely in the quicksand of Autointoxication II?