The osmo-metabolic approach: a novel and tantalizing glucose-sparing strategy in peritoneal dialysis

Transitioning to peritoneal dialysis: it does not matter where you come from

INTRODUCTION

Patients with end-stage renal disease (ESRD) frequently change renal replacement (RRT) therapy modality due to medical or social reasons. We aimed to evaluate the outcomes of patients under peritoneal dialysis (PD) according to the preceding RRT modality.

METHODS

We conducted a retrospective observational single-center study in prevalent PD patients from January 1, 2010, to December 31, 2017, who were followed for 60 months or until they dropped out of PD. Patients were divided into three groups according to the preceding RRT: prior hemodialysis (HD), failed kidney transplant (KT), and PD-first.

RESULTS

Among 152 patients, 115 were PD-first, 22 transitioned from HD, and 15 from a failing KT. There was a tendency for ultrafiltration failure to occur more in patients transitioning from HD (27.3% vs. 9.6% vs. 6.7%, p = 0.07). Residual renal function was better preserved in the group with no prior RRT (p < 0.001). A tendency towards a higher annual rate of peritonitis was observed in the prior KT group (0.70 peritonitis/year per patient vs. 0.10 vs. 0.21, p = 0.065). Thirteen patients (8.6%) had a major cardiovascular event, 5 of those had been transferred from a failing KT (p = 0.004). There were no differences between PD-first, prior KT, and prior HD in terms of death and technique survival (p = 0.195 and p = 0.917, respectively) and PD efficacy was adequate in all groups.

CONCLUSIONS

PD is a suitable option for ESRD patients regardless of the previous RRT and should be offered to patients according to their clinical and social status and preferences.

Oxidative stress reduction by icodextrin-based glucose-free solutions in peritoneal dialysis: Support for new promising approaches

BACKGROUND

Oxidative stress (OxSt) and inflammation are common in CKD and are known CV and mortality risk factors. In peritoneal dialysis (PD) OxSt and Inflammation even increase due to the use of glucose-based solutions.

PATIENTS AND METHODS

This study analyzed in 15 PD patients the effect of 3 and 6 months of treatment with icodextrin-based glucose-free solutions on OxSt and inflammation, evaluating p22phox protein expression (Western blot), NADPH oxidase subunit, essential for OxSt activation, MYPT-1 phosphorylation state, marker of RhoA/Rho kinase pathway (ROCK) activity, involved in the induction of OxSt (Western blot) and Malondialdehyde (MDA) production (fluorimetric assay). Interleukin (IL)-6 blood level (chemiluminescence assay) has been measured and used as a marker of inflammation.

RESULTS

p22phox protein expression, MYPT 1 phosphorylation, and MDA were reduced after 3 months from the start of icodextrin (1.28 ± 0.18 d.u. vs. 1.50 ± 0.19, p = 0.049; 0.89 ± 0.03 vs. 0.98 ± 0.03, p = 0.004; 4.20 ± 0.18 nmol/mL vs. 4.84 ± 0.32 nmol/mL, p = 0.045, respectively). In a subgroup of 9 patients who continued the treatment up to 6 months, MYPT-1 phosphorylation was further reduced at 6 months compared to baseline (0.84 ± 0.06 vs. 0.99 ± 0.04, p = 0.043), while p22phox protein expression was reduced only at 6 months versus baseline (1.03 ± 0.05 vs. 1.68 ± 0.22, p = 0.021). In this subgroup, MDA was reduced at 6 months versus baseline (4.03 ± 0.24 nmol/mL vs. 4.68 ± 0,32, p = 0.024) and also versus 3 months (4.03 ± 0.24 vs. 4.35 ± 0.21, p = 0.008). IL-6 level although reduced both at 3 and 6 months, did not reach statistical significance.

CONCLUSIONS

The reduction of OxSt with icodextrin-based PD solutions, although obtained in a small patients cohort and in a limited time duration study, strongly supports the rationale of using osmo-metabolic agents-based fluids replacing glucose-based fluids. Ongoing studies with these agents will provide information regarding preservation of peritoneal membrane integrity, residual renal function, and reduction of CVD risk factors such as OxSt and inflammation.

Exploring the Therapeutic Potential of Peritoneal Dialysis (PD) in the Treatment of Neurological Disorders

Peritoneal dialysis (PD) is a well-established renal replacement therapy commonly employed in clinical practice. While its primary application is in the treatment of kidney disease, its potential in addressing other systemic disorders, including neurological diseases, has garnered increasing interest. This study provides a comprehensive overview of the related technologies, unique advantages, and clinical applications of PD in the context of neurological disorders. By exploring the mechanism underlying PD, its application in neurological diseases, and associated complications, we addressed the feasibility and benefits of PD as an adjunct therapy for various neurological conditions. Our study aims to highlight its role in detoxification and symptom management, as well as its advantages over other universally accepted methods of renal replacement therapy. Our goal is to bring to the spotlight the therapeutic potential of PD in neurological diseases, such as stroke, stimulate further research, and broaden the scope of its application in the clinical setting.

The Peritoneal Membrane and its Role in Peritoneal Dialysis

A healthy and functional peritoneal membrane is key to achieve sufficient ultrafiltration and to restore fluid balance, a major component of high-quality prescription in patients treated with peritoneal dialysis (PD). Variability in membrane function at the start of PD or changes over time on treatment influence dialysis prescription and outcomes, and dysfunction of the peritoneal membrane contributes to fluid overload and associated complications. In this review, we summarize the current knowledge about the structure, function and pathophysiology of the peritoneal membrane with a focus on clinical implications for patient-centered care. We also discuss the molecular and genetic mechanisms of solute and water transport across the peritoneal membrane, including the role of aquaporin water channels in crystalloid vs. colloid osmosis; why and how to assess membrane function using peritoneal equilibration tests; the etiologies of membrane dysfunction and their specific management; and the impact of genetic variation on membrane function and outcomes in patients treated with PD. This review also identifies the gaps in current knowledge and perspectives for future research to improve our understanding of the peritoneal membrane and, ultimately, to improve the care of patients treated with PD.

Narrative Review of glycaemic management in people with diabetes on peritoneal dialysis

There is an increasing number of people with diabetes on peritoneal dialysis (PD) worldwide. However, there is a lack of guidelines and clinical recommendations for managing glucose control in people with diabetes on PD. The aim of this review is to provide a summary of the relevant literature and highlight key clinical considerations with practical aspects in the management of diabetes in people undergoing PD. A formal systematic review was not conducted because of the lack of sufficient and suitable clinical studies. A literature search was performed using PubMed, MEDLINE, Central, Google Scholar and ClinicalTrials.gov., from 1980 through February 2022. The search was limited to publications in English. This narrative review and related guidance have been developed jointly by diabetologists and nephrologists, who reviewed all available current global evidence regarding the management of diabetes in people on PD.We focus on the importance of individualized care for people with diabetes on PD, the burden of hypoglycemia, glycemic variability in the context of PD and treatment choices for optimizing glucose control. In this review, we have summarized the clinical considerations to guide and inform clinicians providing care for people with diabetes on PD.

Peritoneal dialysis in the modern era

The practice and clinical outcomes of peritoneal dialysis (PD) have demonstrated significant improvement over the past 20 years. The aim of this review is to increase awareness and update healthcare professionals on current PD practice, especially with respect to patient and technique survival, patient modality selection, pathways onto PD, understanding patient experience of care and use prior to kidney transplantation. These improvements have been impacted, at least in part, by greater emphasis on shared decision-making in dialysis modality selection, the use of advanced laparoscopic techniques for PD catheter implantation, developments in PD connecting systems, glucose-sparing strategies, and modernising technology in managing automated PD patients remotely. Evidence-based clinical guidelines such as those prepared by national and international societies such as the International Society of PD have contributed to improved PD practice underpinned by a recognition of the place of continuous quality improvement processes.

How peritoneal dialysis transforms the peritoneum and vasculature in children with chronic kidney disease-what can we learn for future treatment?

Children with chronic kidney disease (CKD) suffer from inflammation and reactive metabolite-induced stress, which massively accelerates tissue and vascular aging. Peritoneal dialysis (PD) is the preferred dialysis mode in children, but currently used PD fluids contain far supraphysiological glucose concentrations for fluid and toxin removal and glucose degradation products (GDP). While the peritoneal membrane of children with CKD G5 exhibits only minor alterations, PD fluids trigger numerous molecular cascades resulting in major peritoneal membrane inflammation, hypervascularization, and fibrosis, with distinct molecular and morphological patterns depending on the GDP content of the PD fluid used. PD further aggravates systemic vascular disease. The systemic vascular aging process is particularly pronounced when PD fluids with high GDP concentrations are used. GDP induce endothelial junction disintegration, apoptosis, fibrosis, and intima thickening. This review gives an overview on the molecular mechanisms of peritoneal and vascular transformation and strategies to improve peritoneal and vascular health in patients on PD.

Fibrosis of Peritoneal Membrane as Target of New Therapies in Peritoneal Dialysis

Peritoneal dialysis (PD) is an efficient renal replacement therapy for patients with end-stage renal disease. Even if it ensures an outcome equivalent to hemodialysis and a better quality of life, in the long-term, PD is associated with the development of peritoneal fibrosis and the consequents patient morbidity and PD technique failure. This unfavorable effect is mostly due to the bio-incompatibility of PD solution (mainly based on high glucose concentration). In the present review, we described the mechanisms and the signaling pathway that governs peritoneal fibrosis, epithelial to mesenchymal transition of mesothelial cells, and angiogenesis. Lastly, we summarize the present and future strategies for developing more biocompatible PD solutions.

Dual SGLT1/SGLT2 inhibitor phlorizin reduces glucose transport in experimental peritoneal dialysis

INTRODUCTION

Glucose absorption during peritoneal dialysis (PD) is commonly assumed to occur via paracellular pathways. We recently showed that SGLT2 inhibition did not reduce glucose absorption in experimental PD, but the potential role of glucose transport into cells is still unclear. Here we sought to elucidate the effects of phlorizin, a non-selective competitive inhibitor of sodium glucose co-transporters 1 and 2 (SGLT1 and SGLT2), in an experimental rat model of PD.

METHODS

A 120-min PD dwell was performed in 12 anesthetised Sprague-Dawley rats using 1.5% glucose fluid with a fill volume of 20 mL with (n = 6) or without (n = 6) intraperitoneal phlorizin (50 mg/L). Several parameters for peritoneal water and solute transport were monitored during the treatment.

RESULTS

Phlorizin markedly increased the urinary excretion of glucose, lowered plasma glucose and increased plasma creatinine after PD. Median glucose diffusion capacity at 60 min was significantly lower (p < 0.05) being 196 µL/min (IQR 178-213) for phlorizin-treated animals compared to 238 µL/min (IQR 233-268) in controls. Median fractional dialysate glucose concentration at 60 min (D/D ₀) was significantly higher (p < 0.05) in phlorizin-treated animals being 0.65 (IQR 0.63-0.67) compared to 0.61 (IQR 0.60-0.62) in controls. At 120 min, there was no difference in solute or water transport across the peritoneal membrane.

CONCLUSION

Our findings indicate that a part of glucose absorption during the initial part of the dwell occurs via transport into peritoneal cells.

Aquaporin-1 Facilitates Transmesothelial Water Permeability: In Vitro and Ex Vivo Evidence and Possible Implications in Peritoneal Dialysis

We previously showed that mesothelial cells in human peritoneum express the water channel aquaporin 1 (AQP1) at the plasma membrane, suggesting that, although in a non-physiological context, it may facilitate osmotic water exchange during peritoneal dialysis (PD). According to the three-pore model that predicts the transport of water during PD, the endothelium of peritoneal capillaries is the major limiting barrier to water transport across peritoneum, assuming the functional role of the mesothelium, as a semipermeable barrier, to be negligible. We hypothesized that an intact mesothelial layer is poorly permeable to water unless AQP1 is expressed at the plasma membrane. To demonstrate that, we characterized an immortalized cell line of human mesothelium (HMC) and measured the osmotically-driven transmesothelial water flux in the absence or in the presence of AQP1. The presence of tight junctions between HMC was investigated by immunofluorescence. Bioelectrical parameters of HMC monolayers were studied by Ussing Chambers and transepithelial water transport was investigated by an electrophysiological approach based on measurements of TEA⁺ dilution in the apical bathing solution, through TEA⁺-sensitive microelectrodes. HMCs express Zo-1 and occludin at the tight junctions and a transepithelial vectorial Na⁺ transport. Real-time transmesothelial water flux, in response to an increase of osmolarity in the apical solution, indicated that, in the presence of AQP1, the rate of TEA⁺ dilution was up to four-fold higher than in its absence. Of note, we confirmed our data in isolated mouse mesentery patches, where we measured an AQP1-dependent transmesothelial osmotic water transport. These results suggest that the mesothelium may represent an additional selective barrier regulating water transport in PD through functional expression of the water channel AQP1.

How to Improve the Biocompatibility of Peritoneal Dialysis Solutions (without Jeopardizing the Patient's Health)

Peritoneal dialysis (PD) is an important, if underprescribed, modality for the treatment of patients with end-stage kidney disease. Among the barriers to its wider use are the deleterious effects of currently commercially available glucose-based PD solutions on the morphological integrity and function of the peritoneal membrane due to fibrosis. This is primarily driven by hyperglycaemia due to its effects, through multiple cytokine and transcription factor signalling-and their metabolic sequelae-on the synthesis of collagen and other extracellular membrane components. In this review, we outline these interactions and explore how novel PD solution formulations are aimed at utilizing this knowledge to minimise the complications associated with fibrosis, while maintaining adequate rates of ultrafiltration across the peritoneal membrane and preservation of patient urinary volumes. We discuss the development of a new generation of reduced-glucose PD solutions that employ a variety of osmotically active constituents and highlight the biochemical rationale underlying optimization of oxidative metabolism within the peritoneal membrane. They are aimed at achieving optimal clinical outcomes and improving the whole-body metabolic profile of patients, particularly those who are glucose-intolerant, insulin-resistant, or diabetic, and for whom daily exposure to high doses of glucose is contraindicated.

Biological Effects of XyloCore, a Glucose Sparing PD Solution, on Mesothelial Cells: Focus on Mesothelial-Mesenchymal Transition, Inflammation and Angiogenesis

Glucose-based solutions remain the most used osmotic agents in peritoneal dialysis (PD), but unavoidably they contribute to the loss of peritoneal filtration capacity. Here, we evaluated at a molecular level the effects of XyloCore, a new PD solution with a low glucose content, in mesothelial and endothelial cells. Cell viability, integrity of mesothelial and endothelial cell membrane, activation of mesothelial and endothelial to mesenchymal transition programs, inflammation, and angiogenesis were evaluated by several techniques. Results showed that XyloCore preserves mesothelial and endothelial cell viability and membrane integrity. Moreover XyloCore, unlike glucose-based solutions, does not exert pro-fibrotic, -inflammatory, and -angiogenic effects. Overall, the in vitro evidence suggests that XyloCore could represent a potential biocompatible solution promising better outcomes in clinical practice.

Mild sodium reduction in peritoneal dialysis solution improves hypertension in end stage kidney disease: a case-report study

Introduction

Blood Pressure (BP) control is largely unsatisfied in End Stage Kidney Disease (ESKD) principally due to sodium retention. Peritoneal Dialysis (PD) is the most common type of home dialysis, using a peritoneal membrane to remove sodium, though sodium removal remains challenging.

Methods

This is a case-study reporting two consecutive ESKD patients treated by a novel peritoneal PD solution with a mildly reduced sodium content (130 mmol/L) to treat hypertension.

Results

In the first case, a 78-year-old woman treated by Continuous Ambulatory PD (CAPD) with standard solution (three 4 h-dwells per day 1.36% glucose 132 mmol/L) showed resistant hypertension confirmed by ambulatory blood pressure monitoring (ABPM), reporting 24 h-BP: 152/81 mmHg, day-BP:151/83 mmHg and night-ABP: 153/75 mmHg, with inversion of the circadian systolic BP rhythm (1.01), despite use of three anti-hypertensives and a diuretic at adequate doses. No sign of hypervolemia was evident. We then switched from standard PD to low-sodium solution in all daily dwells. A six-months low-sodium CAPD enabled us to reduce diurnal (134/75 mmHg) and nocturnal BP (122/67 mmHg), restoring the circadian BP rhythm, with no change in ultrafiltration or residual diuresis. Diet and drug prescription were unmodified too.

The second case was a 61-year-old woman in standard CAPD (three 5 h-dwells per day) suffering from hypertension confirmed by ABPM (mean 24 h-ABP: 139/84 mmHg; mean day-ABP:144/88 mmHg and mean night-ABP:124/70 mmHg). She was switched from 132-Na CAPD to 130-Na CAPD, not changing dialysis schedule. No fluid expansion was evident. During low-sodium CAPD, antihypertensive therapy (amlodipine 10 mg and Olmesartan 20 mg) has been reduced until complete suspension. After 6 months, we repeated ABPM showing a substantial reduction in mean 24 h-ABP (117/69 mmHg), mean diurnal ABP (119/75 mmHg) and mean nocturnal ABP (111/70 mmHg). Ultrafiltration and residual diuresis remained unmodified. No side effects were reported in either cases.

Conclusions

This case-report study suggests that mild low-sodium CAPD might reduce BP in hypertensive ESKD patients.

A New Peritoneal Dialysis Solution Containing L-Carnitine and Xylitol for Patients on Continuous Ambulatory Peritoneal Dialysis: First Clinical Experience

Peritoneal dialysis (PD) is a feasible and effective renal replacement therapy (RRT) thanks to the dialytic properties of the peritoneal membrane (PM). Preservation of PM integrity and transport function is the key to the success of PD therapy, particularly in the long term, since the prolonged exposure to unphysiological hypertonic glucose-based PD solutions in current use is detrimental to the PM, with progressive loss of peritoneal ultrafiltration capacity causing technique failure. Moreover, absorbing too much glucose intraperitoneally from the dialysate may give rise to a number of systemic metabolic effects. Here we report the preliminary results of the first clinical experience based on the use in continuous ambulatory PD (CAPD) patients of novel PD solutions obtained through partly replacing the glucose load with other osmotically active metabolites, such as L-carnitine and xylitol. Ten CAPD patients were treated for four weeks with the new solutions. There was good tolerance to the experimental PD solutions, and no adverse safety signals were observed. Parameters of dialysis efficiency including creatinine clearance and urea Kt/V proved to be stable as well as fluid status, diuresis, and total peritoneal ultrafiltration. The promising tolerance and local/systemic advantages of using L-carnitine and xylitol in the PD solution merit further research.

A Novel Formulation of Glucose-Sparing Peritoneal Dialysis Solutions with l-Carnitine Improves Biocompatibility on Human Mesothelial Cells

The main reason why peritoneal dialysis (PD) still has limited use in the management of patients with end-stage renal disease (ESRD) lies in the fact that the currently used glucose-based PD solutions are not completely biocompatible and determine, over time, the degeneration of the peritoneal membrane (PM) and consequent loss of ultrafiltration (UF). Here we evaluated the biocompatibility of a novel formulation of dialytic solutions, in which a substantial amount of glucose is replaced by two osmometabolic agents, xylitol and l-carnitine. The effect of this novel formulation on cell viability, the integrity of the mesothelial barrier and secretion of pro-inflammatory cytokines was evaluated on human mesothelial cells grown on cell culture inserts and exposed to the PD solution only at the apical side, mimicking the condition of a PD dwell. The results were compared to those obtained after exposure to a panel of dialytic solutions commonly used in clinical practice. We report here compelling evidence that this novel formulation shows better performance in terms of higher cell viability, better preservation of the integrity of the mesothelial layer and reduced release of pro-inflammatory cytokines. This new formulation could represent a step forward towards obtaining PD solutions with high biocompatibility.

Proteomic Research in Peritoneal Dialysis

Peritoneal dialysis (PD) is an established home care, cost-effective renal replacement therapy (RRT), which offers several advantages over the most used dialysis modality, hemodialysis. Despite its potential benefits, however, PD is an under-prescribed method of treating uremic patients. Infectious complications (primarily peritonitis) and bio-incompatibility of PD solutions are the main contributors to PD drop-out, due to their potential for altering the functional and anatomical integrity of the peritoneal membrane. To improve the clinical outcome of PD, there is a need for biomarkers to identify patients at risk of PD-related complications and to guide personalized interventions. Several recent studies have shown that proteomic investigation may be a powerful tool in the prediction, early diagnosis, prognostic assessment, and therapeutic monitoring of patients on PD. Indeed, analysis of the proteome present in PD effluent has uncovered several proteins involved in inflammation and pro-fibrotic insult, in encapsulating peritoneal sclerosis, or even in detecting early changes before any measurable modifications occur in the traditional clinical parameters used to evaluate PD efficacy. We here review the proteomic studies conducted thus far, addressing the potential use of such omics methodology in identifying potential new biomarkers of the peritoneal membrane welfare in relation to dialytic prescription and adequacy.