Cafeteria Diet-Induced Obesity Worsens Experimental CKD.

Obesity is a significant risk factor for chronic kidney disease (CKD). This study aimed to evaluate the impact of obesity on the development of kidney fibrosis in a model of cafeteria diet rats undergoing 5/6th nephrectomy (SNx). Collagen 1, 3, and 4 expression, adipocyte size, macrophage number, and the expression of 30 adipokines were determined. Collagen 1 expression in kidney tissue was increased in Standard-SNx and Cafeteria-SNx (7.1 ± 0.6% and 8.9 ± 0.9 tissue area, respectively). Renal expression of collagen 3 and 4 was significantly increased (p < 0.05) in Cafeteria-SNx (8.6 ± 1.5 and 10.9 ± 1.9% tissue area, respectively) compared to Cafeteria (5.2 ± 0.5 and 6.3 ± 0.6% tissue area, respectively). Adipocyte size in eWAT was significantly increased by the cafeteria diet. In Cafeteria-SNx, we observed a significant increase in macrophage number in the kidney (p = 0.01) and a consistent tendency in eWAT. The adipokine level was higher in the Cafeteria groups. Interleukin 11, dipeptidyl peptidase 4, and serpin 1 were increased in Cafeteria-SNx. In the kidney, collagen 3 and 4 expressions and the number of macrophages were increased in Cafeteria-SNx, suggesting an exacerbation by preexisting obesity of CKD-induced renal inflammation and fibrosis. IL11, DPP4, and serpin 1 can act directly on fibrosis and participate in the observed worsening CKD.

Implications of Senescent Cell Burden and NRF2 Pathway in Uremic Calcification: A Translational Study.

Increased senescent cell burden and dysregulation of the nuclear factor erythroid 2-related factor 2 (NRF2) pathway have been associated with numerous age-related pathologies; however, their role in promoting vascular calcification (VC) in chronic kidney disease (CKD) has yet to be determined. We investigated whether senescence and NRF2 pathways may serve as drivers of uremia-induced VC using three complementary approaches: a novel model of induced VC in 5/6-nephrectomized rats supplemented with high phosphate and vitamin D; epigastric arteries from CKD patients with established medial calcification; and vascular smooth muscle cells (VSMCs) incubated with uremic serum. Expression of p16Ink4a and p21Cip1, as well as γ-H2A-positive cells, confirmed increased senescent cell burden at the site of calcium deposits in aortic sections in rats, and was similarly observed in calcified epigastric arteries from CKD patients through increased p16Ink4a expression. However, uremic serum-induced VSMC calcification was not accompanied by senescence. Expression of NRF2 and downstream genes, Nqo1 and Sod1, was associated with calcification in uremic rats, while no difference was observed between calcified and non-calcified EAs. Conversely, in vitro uremic serum-driven VC was associated with depleted NRF2 expression. Together, our data strengthen the importance of senescence and NRF2 pathways as potential therapeutic options to combat VC in CKD.

Gut-Kidney Axis Investigations in Animal Models of Chronic Kidney Disease.

Chronic kidney disease (CKD) is an incurable disease in which renal function gradually declines, resulting in no noticeable symptoms during the early stages and a life-threatening disorder in the latest stage. The changes that accompany renal failure are likely to influence the gut microbiota, or the ecosystem of micro-organisms resident in the intestine. Altered gut microbiota can display metabolic changes and become harmful to the host. To study the gut-kidney axis in vivo, animal models should ideally reproduce the disorders affecting both the host and the gut microbiota. Murine models of CKD, but not dog, manifest slowed gut transit, similarly to patient. Animal models of CKD also reproduce altered intestinal barrier function, as well as the resulting leaky gut syndrome and bacterial translocation. CKD animal models replicate metabolic but not compositional changes in the gut microbiota. Researchers investigating the gut-kidney axis should pay attention to the selection of the animal model (disease induction method, species) and the setting of the experimental design (control group, sterilization method, individually ventilated cages) that have been shown to influence gut microbiota.

Vascular calcification in different arterial beds in ex vivo ring culture and in vivo rat model.

Vascular calcification is a risk factor for cardiovascular and kidney diseases. Medial calcification may differently affect the arterial tree depending on vessel location and smooth muscle injury. The aim was to map the anatomical distribution of vascular calcifications on different arteries and artery locations, in cultured artery rings (ex vivo) and in a rat model of elastocalcinosis (in vivo). Vascular calcification was assessed histologically (von Kossa staining of the media) and by calcium content measurement. Arteries of different sizes were harvested from untreated rats for ring culture and from the vitamin D3-nicotine (VDN) rat model for direct observation. When cultured in pro-calcifying conditions, thoracic aorta exhibited similar calcification from the arch to the diaphragm. Calcification increased in abdominal aorta along with the reduction in cross sectional area. Carotid and renal arteries exhibited similar ex vivo calcification. In VDN rats, calcification was greater in carotid artery than in aorta, and was accompanied by fibrosis and apoptosis. Ex vivo, calcification was increased by the induction of lesions on arteries. Along the vascular tree, calcification of the arterial wall increases with the narrowing of vessels in ex vivo ring culture and in vivo. The observed differences represent local susceptibility of the vessels to the calcifying processes.

Renal insufficiency and chronic kidney disease - Promotor or consequence of pathological post-translational modifications.

More than 840 million people, representing almost 10% of world population, were estimated to have chronic kidney disease (CKD) in 2017. In CKD, many systemic changes relative to oxidative stress, inflammation, energy balance or neuroendocrine signalling are observed and can be linked to dysfunctional proteins, including protein post-translational modifications (PTMs). Recent technical advances enabled the detection of PTMs and allowed understanding their participation in CKD pathophysiology and kidney damage. In this review article, the interconnections between CKD and PTMs, both as causes and consequences, are described. PTMs, particularly non-enzymatic PTMs, are frequently observed in CKD, as they are the direct consequence of systemic changes following the decline in kidney function. Other PTMs, mainly enzymatic ones, are critical for proper kidney physiology. Still, both types of PTMs have been shown to induce damage not only in kidney but also in other organs (brain, cardiovascular system). Therapeutic approaches focusing on metabolic changes responsible for PTMs alteration have shown interesting results. Targeting specific PTMs responsible for kidney damage is also being considered, which could lead to the development of innovative treatments.

Prevention of vascular calcification by the endogenous chromogranin A-derived mediator that inhibits osteogenic transdifferentiation.

The adrenal glands participate in cardiovascular (CV) physiology and the pathophysiology of CV diseases through their effects on sodium and water metabolism, vascular tone and cardiac function. In the present study, we identified a new adrenal compound controlling mesenchymal cell differentiation that regulates osteoblastic differentiation in the context of vascular calcification. This peptide was named the "calcification blocking factor" (CBF) due to its protective effect against vascular calcification and is released from chromogranin A via enzymatic cleavage by calpain 1 and kallikrein. CBF reduced the calcium content of cells and thoracic aortic rings under calcifying culture conditions, as well as in aortas from animals treated with vitamin D and nicotine (VDN animals). Furthermore, CBF prevented vascular smooth muscle cell (VSMC) transdifferentiation into osteoblast-like cells within the vascular wall via the sodium-dependent phosphate transporter PIT-1 and by inhibition of NF-κB activation and the subsequent BMP2/p-SMAD pathway. Pulse pressure, a marker of arterial stiffness, was significantly decreased in VDN animals treated with CBF. In line with our preclinical data, CBF concentration is significantly reduced in diseases characterized by increased calcification, as shown in patients with chronic kidney disease. In preparation for clinical translation, the active site of the native 19-AS long native CBF was identified as EGQEEEED. In conclusion, we have identified the new peptide CBF, which is secreted from the adrenal glands and might prevent vascular calcification by inhibition of osteogenic transdifferentiation. The anti-calcific effects of CBF and short active site may therefore promote the development of new tools for the prevention and/or treatment of vascular calcification.

A history of uraemic toxicity and of the European Uraemic Toxin Work Group (EUTox).

The uraemic syndrome is a complex clinical picture developing in the advanced stages of chronic kidney disease, resulting in a myriad of complications and a high early mortality. This picture is to a significant extent defined by retention of metabolites and peptides that with a preserved kidney function are excreted or degraded by the kidneys. In as far as those solutes have a negative biological/biochemical impact, they are called uraemic toxins. Here, we describe the historical evolution of the scientific knowledge about uraemic toxins and the role played in this process by the European Uraemic Toxin Work Group (EUTox) during the last two decades. The earliest knowledge about a uraemic toxin goes back to the early 17th century when the existence of what would later be named as urea was recognized. It took about two further centuries to better define the role of urea and its link to kidney failure, and one more century to identify the relevance of post-translational modifications caused by urea such as carbamoylation. The knowledge progressively extended, especially from 1980 on, by the identification of more and more toxins and their adverse biological/biochemical impact. Progress of knowledge was paralleled and impacted by evolution of dialysis strategies. The last two decades, when insights grew exponentially, coincide with the foundation and activity of EUTox. In the final section, we summarize the role and accomplishments of EUTox and the part it is likely to play in future action, which should be organized around focus points like biomarker and potential target identification, intestinal generation, toxicity mechanisms and their correction, kidney and extracorporeal removal, patient-oriented outcomes and toxin characteristics in acute kidney injury and transplantation.

The renal patient seen by non-renal physicians: the kidney embedded in the 'milieu intérieur'.

Chronic kidney disease is defined as a decrease in renal function or evidence of kidney injury for >3 months. This represents an oversimplification that may confuse physicians. Thus kidney function is equated to glomerular filtration rate, which represents one of multiple kidney functions. Some potentially more important renal functions are lost earlier, such as the production for the anti-ageing factor Klotho. Overall, these changes modify the emergent properties of the body, altering the relationships between different organs and systems, in a manner that is difficult to predict the response to interventions based on normal physiology concepts, as there is a novel steady state of interorgan relations. In this regard we now discuss the impact of CKD on heart failure; osteomuscular and joint pain and bone fragility and fractures; and osteosarcopaenia as seen by a cardiologist, a rheumatologist and a geriatrician.

Data Sharing Under the General Data Protection Regulation: Time to Harmonize Law and Research Ethics?

The General Data Protection Regulation (GDPR) became binding law in the European Union Member States in 2018, as a step toward harmonizing personal data protection legislation in the European Union. The Regulation governs almost all types of personal data processing, hence, also, those pertaining to biomedical research. The purpose of this article is to highlight the main practical issues related to data and biological sample sharing that biomedical researchers face regularly, and to specify how these are addressed in the context of GDPR, after consulting with ethics/legal experts. We identify areas in which clarifications of the GDPR are needed, particularly those related to consent requirements by study participants. Amendments should target the following: (1) restricting exceptions based on national laws and increasing harmonization, (2) confirming the concept of broad consent, and (3) defining a roadmap for secondary use of data. These changes will be achieved by acknowledged learned societies in the field taking the lead in preparing a document giving guidance for the optimal interpretation of the GDPR, which will be finalized following a period of commenting by a broad multistakeholder audience. In parallel, promoting engagement and education of the public in the relevant issues (such as different consent types or residual risk for re-identification), on both local/national and international levels, is considered critical for advancement. We hope that this article will open this broad discussion involving all major stakeholders, toward optimizing the GDPR and allowing a harmonized transnational research approach.

Measuring intradialyser transmembrane and hydrostatic pressures: pitfalls and relevance in haemodialysis and haemodiafiltration.

BACKGROUND: Post-dilutional haemodiafiltration (HDF) with high convection volumes (HCVs) could improve survival. HCV-HDF requires a significant pressure to be applied to the dialyser membrane. The aim of this study was to assess the pressure applied to the dialysers in HCV-HDF, evaluate the influence of transmembrane pressure (TMP) calculation methods on TMP values and check how they relate to the safety limits proposed by guidelines. METHODS: Nine stable dialysis patients were treated with post-dilutional HCV-HDF with three different convection volumes [including haemodialysis (HD)]. The pressures at blood inlet (Bi), blood outlet (Bo) and dialysate outlet (Do) were continuously recorded. TMP was calculated using two pressures (TMP2: Bo, Do) or three pressures (TMP3: Bo, Do, Bi). Dialysis parameters were analysed at the start of the session and at the end of treatment or at the first occurrence of a manual intervention to decrease convection due to TMP alarms. RESULTS: During HD sessions, TMP2 and TMP3 remained stable. During HCV-HDF, TMP2 remained stable while TMP3 clearly increased. For the same condition, TMP3 could be 3-fold greater than TMP2. This shows that the TMP limit of 300 mmHg as recommended by guidelines could have different effects according to the TMP calculation method. In HCV-HDF, the pressure at the Bi increased over time and exceeded the safety limits of 600 mmHg provided by the manufacturer, even when respecting TMP safety limits. CONCLUSIONS: This study draws our attention to the dangers of using a two-pressure points TMP calculation, particularly when performing HCV-HDF.

Optimisation of cell and ex vivo culture conditions to study vascular calcification.

Medial vascular calcification (MVC) is a highly prevalent disease associated with a high risk of severe, potentially lethal, complications. While animal studies may not systematically be circumvented, in vitro systems have been proven useful to study disease physiopathology. In the context of MVC, the absence of a clinically relevant standardized in vitro method prevents the appropriate comparison and overall interpretation of results originating from different experiments. The aim of our study is to establish in vitro models mimicking in vivo vascular calcification and to select the best methods to unravel the mechanisms involved in MVC. Human aortic smooth muscle cells and rat aortic rings were cultured in different conditions. The influence of fetal calf serum (FCS), alkaline phosphatase, phosphate and calcium concentrations in the medium were evaluated. We identified culture conditions, including the herein reported Aorta Calcifying Medium (ACM), which allowed a reproducible and specific medial calcification of aortic explants. Studying cells and aortic explants cultured, the involvement of bone morphogenetic protein 2 (BMP2) pathway, fibrosis and apoptosis processes in in vitro MVC were demonstrated. Expression of osteoblastic markers was also observed suggesting the occurrence of transdifferentiation of smooth muscle cells to osteoblasts in our models. The use of these models will help researchers in the field of vascular calcification to achieve reproducible results and allow result comparison in a more consistent way.

Multiplexed MRM-based protein quantification of putative prognostic biomarkers for chronic kidney disease progression in plasma.

Current diagnostic measures for Chronic Kidney Disease (CKD) include detection of reduced estimated glomerular filtration rate (eGFR) and albuminuria, which have suboptimal accuracies in predicting disease progression. The disease complexity and heterogeneity underscore the need for multiplex quantification of different markers. The goal of this study was to determine the association of six previously reported CKD-associated plasma proteins [B2M (Beta-2-microglobulin), SERPINF1 (Pigment epithelium-derived factor), AMBP (Protein AMBP), LYZ (Lysozyme C), HBB (Hemoglobin subunit beta) and IGHA1 (Immunoglobulin heavy constant alpha 1)], as measured in a multiplex format, with kidney function, and outcome. Antibody-free, multiple reaction monitoring mass spectrometry (MRM) assays were developed, characterized for their analytical performance, and used for the analysis of 72 plasma samples from a patient cohort with longitudinal follow-up. The MRM significantly correlated (Rho = 0.5-0.9) with results from respective ELISA. Five proteins [AMBP, B2M, LYZ, HBB and SERPINF1] were significantly associated with eGFR, with the three former also associated with unfavorable outcome. The combination of these markers provided stronger associations with outcome (p < 0.0001) compared to individual markers. Collectively, our study describes a multiplex assay for absolute quantification and verification analysis of previously described putative CKD prognostic markers, laying the groundwork for further use in prospective validation studies.

The CKD plasma lipidome varies with disease severity and outcome.

BACKGROUND: Various alterations in lipid metabolism have been observed in patients with chronic kidney disease (CKD). OBJECTIVES: To determine the levels of lipid species in plasma from CKD and hemodialysis (HD) patients and test their association with CKD severity and patient outcome. METHODS: Seventy-seven patients with CKD stage 2 to HD were grouped into classes of CKD severity at baseline and followed-up for 3.5 years for the occurrence of transition to HD or death (combined outcome). Plasma levels of phosphatidylcholines (PCs), lysophosphatidylcholines (LPCs), sphingomyelins (SMs), and fatty acids were analyzed by flow-injection analysis coupled to tandem mass spectrometry or gas chromatography coupled with mass spectrometry. Kruskal Wallis rank tests and Cox regressions were used to analyze the association of lipids with CKD severity and the risk of combined outcome, respectively. RESULTS: The plasma level of PCs, LPCs, and SMs was decreased in HD patients compared with nondialyzed CKD patients (all P < .05), whereas esterified and/or nonesterified fatty acids level did not change. Thirty-four lipids displayed significantly lower abundance in plasma of HD patients, whereas elaidic acid (C18:1ω9t) level was increased (P < .001). The total amount of LPCs and individual LPCs were associated with better outcome (P < .05). In particular, LPC 18:2 and LPC 20:3 were statistically associated with outcome in adjusted models (P < .05). DISCUSSION: In HD patients, a reduction in plasma lipids is observed. Some of the alterations, namely reduced LPCs, were associated with the risk of adverse outcome. These changes could be related to metabolic dysfunctions.

Blood Pressure Seasonality in Hemodialysis Patients from Five European Cities of Different Latitudes.

BACKGROUND/AIMS: Climate influences the regulation of blood pressure (BP). Our objective was to precisely estimate BP seasonality in hemodialysis (HD) patients from five European cities with marked climate differences. METHODS: Stable prevalent HD patients from 5 European facilities (Santa Cruz de Tenerife (Spain), Seville (Spain), Montpellier (France), Ottignies (Belgium), Umea (Sweden)) present over the years 1995-1999 were included in this historical longitudinal observational study. Individual monthly averages of pre-dialysis BP level were computed from all facility BP measurements (> 90 000 observations). The association between BP level and location, seasons and meteorological measurements was analyzed by mixed models. RESULTS: 261 patients were included and followed-up for a median duration of 2 years (6903 monthly observations). Pre-dialysis SBP and DBP were minimal in summer (July) and maximal in winter (November and December), and mean changes were respectively 4.2 [3.0; 5.4] and 2.0 [1.3; 2.7] mmHg. Seasonality was confirmed in 4 locations (Pseason≤0.001 for SBP and DBP), but not in Umea (both Pseason> 0.05). Seasonal changes in DBP were larger in southern locations (Pinteraction=0.02). BP level was associated with climate parameters: in a positive manner with humidity or rainfall, and inversely with sunshine duration or temperature. The effects of temperature and rainfall on DBP varied with latitude (Pinteraction< 0.02) and were greater in southern locations. CONCLUSION: BP varies with seasons and climate in different European areas and seasonality can be more important in southern locations. These changes in BP deserve attention as they may be responsible for a significant increase in cardiovascular risk which may be preventable.

Correction: Consequences of increasing convection onto patient care and protein removal in hemodialysis.

[This corrects the article DOI: 10.1371/journal.pone.0171179.].

Geographical Variations in Blood Pressure Level and Seasonality in Hemodialysis Patients.

Seasons and climate influence the regulation of blood pressure (BP) in the general population and in hemodialysis patients. It is unknown whether this phenomenon varies across the world. Our objective was to estimate BP seasonality in hemodialysis patients from different geographical locations. Patients from 7 European countries (Spain, Italy, France, Belgium, Germany, United Kingdom, and Sweden) participating in the DOPPS (Dialysis Outcomes and Practice Patterns Study) on years 2005 to 2011 were studied. Factors influencing pre- and postdialysis systolic BP and diastolic BP levels were analyzed by mixed models. There were 9655 patients (median age, 68; 59% male) from 263 facilities, seen every 4 months during a median duration of 1.3 years. Pre- and postdialysis systolic BP increased by a mean estimate of 5.1 mm Hg (95% confidence interval [CI], 3.7-6.4 mm Hg) and 4.4 mm Hg (95% CI, 2.9-5.9 mm Hg) for each 10° increase in latitude (1111 km to the North). In the longitudinal analysis, predialysis systolic BP was lower in summer and higher in winter (difference, 1.7 mm Hg; 95% CI, 1.3-2.2 mm Hg), with greater differences in southern locations (Pinteraction=0.04). Predialysis systolic BP was inversely associated with outdoor temperature (-0.8 mm Hg/7.2°C; 95% CI, -1.0 to -0.5 mm Hg/7.2°C), with steeper slopes in southern locations (Pinteraction=0.005). Results were similar for predialysis diastolic BP. In conclusion, there is a geographical and seasonal gradient of BP in European hemodialysis patients. There is a need to consider these effects when evaluating and treating BP in this population and potentially in others.