High glucose dialysate-induced peritoneal fibrosis: Pathophysiology, underlying mechanisms and potential therapeutic strategies

JPH203 alleviates peritoneal fibrosis via inhibition of amino acid-mediated mTORC1 signaling

BACKGROUND AND AIMS

The mesothelial-mesenchymal transition (MMT) of mesothelial cells has been recognized as a critical process during progression of peritoneal fibrosis (PF). Despite its crucial role in amino acid transport and metabolism, the involvement of L-type amino acid transporter 1 (LAT1) and the potential therapeutic role of its inhibitor, JPH203, in fibrotic diseases remain unexplored. Considering the paucity of research on amino acid-mediated mTORC1 activation in PF, our study endeavors to elucidate the protective effects of JPH203 against PF and explore the involvement of amino acid-mediated mTORC1 signaling in this context.

METHODS

We established the transforming growth factor beta 1 (TGF-β1) induced MMT model in primary human mesothelial cells and the peritoneal dialysis fluid (PDF) induced PF model in mice. The therapeutic effects of JPH203 on PF were then examined on these two models by real-time quantitative polymerase chain reaction, western blotting, immunofluorescence staining, Masson's trichrome staining, H&E staining, picro-sirius red staining, and immunohistochemistry. The involvement of amino acid-mediated mTORC1 signaling was screened by RNA sequencing and further verified by western blotting in vitro.

RESULTS

LAT1 was significantly upregulated and JPH203 markedly attenuated fibrotic phenotype both in vitro and in vivo. RNA-seq unveiled a significant enrichment of mTOR signaling pathway in response to JPH203 treatment. Western blotting results indicated that JPH203 alleviates PF by inhibiting amino acid-mediated mTORC1 signaling, which differs from the direct inhibition observed with rapamycin.

CONCLUSION

JPH203 alleviates PF by inhibiting amino acid-mediated mTORC1 signaling.

Dyslipidemia in Peritoneal Dialysis: Implications for Peritoneal Membrane Function and Patient Outcomes

Dyslipidemia is a common metabolic complication in patients undergoing peritoneal dialysis (PD) and has traditionally been viewed primarily in terms of cardiovascular risk. Current guidelines do not recommend initiating lipid-lowering therapy in dialysis patients due to insufficient evidence of its benefits on cardiovascular mortality. However, the impact of dyslipidemia in PD patients may extend beyond cardiovascular concerns, influencing PD-related outcomes such as the peritoneal ultrafiltration rate, residual kidney function, PD technique survival, and overall mortality. This review challenges the traditional perspective by discussing dyslipidemia's potential role in PD-related complications, which may account for the observed link between dyslipidemia and increased all-cause mortality in PD patients. It explores the pathophysiology of dyslipidemia in PD, the molecular mechanisms linking dyslipidemia to peritoneal membrane dysfunction, and summarizes clinical evidence supporting this hypothesis. In addition, this paper examines the potential for therapeutic strategies to manage dyslipidemia to improve peritoneal membrane function and patient outcomes. The review calls for future research to investigate dyslipidemia as a potential contributor to peritoneal membrane dysfunction and to develop targeted interventions for PD patients.

Peritoneal fibrosis: from pathophysiological mechanism to medicine

Peritoneal dialysis (PD) is currently one of the effective methods for treating end-stage renal disease (ESRD). However, long-term exposure to high concentration glucose in peritoneal dialysis environment could lead to peritoneal fibrosis (PF), impaired peritoneal filtration function, decreased peritoneal dialysis efficiency, and even withdrawal from peritoneal dialysis in patients. Considerable evidence suggests that peritoneal fibrosis after peritoneal dialysis is related to crucial factors such as mesothelial-to-mesenchymal transition (MMT), inflammatory response, and angiogenesis, etc. In our review, we summarize the pathophysiological mechanisms and further illustrate the future strategies against PF.

Rationale and design of ELIXIR, a randomized, controlled trial to evaluate efficacy and safety of XyloCore, a glucose-sparing solution for peritoneal dialysis

Peritoneal dialysis adoption and technique survival is affected by limitations related to peritoneal membrane longevity and metabolic alterations. Indeed, almost all peritoneal dialysis fluids exploit glucose as an osmotic agent that rapidly diffuses across the peritoneal membrane, potentially resulting in metabolic abnormalities such as hyperglycemia, hyperinsulinemia, obesity, and hyperlipidemia. Moreover, glucose-degradation products generated during heat sterilization, other than glucose itself, induce significant morphological and functional changes in the peritoneum leading to ultrafiltration failure. The partial substitution of glucose with osmotic agents characterized by a better local and systemic biocompatibility has been suggested as a potential strategy to innovate peritoneal dialysis fluids. The approach aims to minimize glucose-associated toxicity, preserving the peritoneal membrane welfare and counteracting common comorbidities. In this work, we report the clinical trial design of ELIXIR, a phase III randomized, controlled, blinded outcome assessment study comparing Xylocore®, an innovative formulation based on Xylitol and l-carnitine, to standard glucose-based regimens, in end-stage kidney disease patients treated with continuous ambulatory peritoneal dialysis; 170 patients will be randomized (1:1) to receive XyloCore® or to continue their pre-randomization peritoneal dialysis (PD) therapy with glucose-only PD solutions, for 6 months. The primary study's objective is to demonstrate the noninferiority of XyloCore® in terms of Kt/V urea, for which a clinically acceptable noninferiority margin of -0.25 has been determined, assuming that all patients will be treated aiming to a minimum target of 1.7 and an optimal target of 2.0.

Selective therapeutic efficacy of tyrosine kinase inhibitor sorafenib on the restoration of methylglyoxal-induced peritoneal fibrosis

Peritoneal fibrosis, a common complication observed in long-term peritoneal dialysis patients, can gradually lead to ultrafiltration failure and the development of encapsulating peritoneal sclerosis. Although mechanisms of peritoneal fibrosis have been proposed, effective therapeutic options are unsatisfactory. Recently, several tyrosine kinase inhibitors have proven to be anti-fibrosis in rodent models. To assess the potential therapeutic effects of tyrosine kinase inhibitors on peritoneal fibrosis in the larger animal model, a novel porcine model of peritoneal fibrosis induced by 40 mM methylglyoxal in 2.5 % dialysate was established, and two different doses (20 mg/kg and 30 mg/kg) of sorafenib were given orally to evaluate their therapeutic efficacy in this study. Our results showed that sorafenib effectively reduced adhesions between peritoneal organs and significantly diminished the thickening of both the parietal and visceral peritoneum. Angiogenesis, vascular endothelial growth factor A production, myofibroblast infiltration, and decreased endothelial glycocalyx resulting from dialysate and methylglyoxal stimulations were also alleviated with sorafenib. However, therapeutic efficacy in ameliorating loss of mesothelial cells, restoring decreased ultrafiltration volume, and improving elevated small solutes transport rates was limited. In conclusion, this study demonstrated that sorafenib could potentially be used for peritoneal fibrosis treatment, but applying sorafenib alone might not be sufficient to fully rescue methylglyoxal-induced peritoneal defects.

Dialysate cyclophilin A as a predictive marker for historical peritonitis in patients undergoing peritoneal dialysis

Introduction

No markers have been used to diagnose historical peritoneal dialysis (PD)-related peritonitis. Cyclophilin A (CypA) is associated with glucose toxicity and inflammation. We hypothesize that dialysate CypA can be a marker for historical peritonitis (at least 3 months free from peritonitis).

Method

An enzyme-linked immunosorbent assay kit was used to measure the concentration of dialysate CypA. Clinical and laboratory data were collected to correlate with historical peritonitis. Mann-Whitney U test and Chi-square test were used for analysis. Receiver operating characteristic (ROC) analysis was used to evaluate predictive power.

Results

Out of a total of 31 patients who had undergone PD for at least 2 years, 18 had no history of PD-related peritonitis, while 13 had experienced PD-related peritonitis at least once. Overall, the patients in this population were in good health (normal white blood cell count, no anemia, normal electrolyte and serum albumin levels). There were no significant differences between patients with and without a history of peritonitis, except for blood white blood cell count (5650.6 ± 1848.4 vs. 7154.6 ± 2056.8, p = 0.032) and dialysate CypA value (24.27 ± 22.715 vs. 54.41 ± 45.63, p = 0.020). In the univariate analysis, only the dialysate CypA level showed a statistically significant association with historical peritonitis (HR = 1.030, 95 % CI = 1.010-1.062, p = 0.046). The AUC for dialysate CypA (>34.83 ng/mL) was 0.748, with a sensitivity of 0.615 and specificity of 0.833.

Conclusion

PD peritonitis poses a significant threat to the long-term use of peritoneal dialysis. Based on our study, even in the absence of concurrent infection, dialysate CypA can serve as a predictive marker for historical peritonitis, demonstrating high predictive power along with fair sensitivity and good specificity.

Luteolin blocks the ROS/PI3K/AKT pathway to inhibit mesothelial-mesenchymal transition and reduce abdominal adhesions

BACKGROUND

Postoperative abdominal adhesion (PAA) is a common postoperative complication. Clinically, various methods have been used to prevent the occurrence of PAA, such as drugs and physiotherapy; however, no satisfactory results have been obtained. Luteolin (LUT) is a natural flavonoid that reduces inflammation and acts as an antioxidant. This research aimed to examine the impact and mechanism of LUT in reducing PAA.

METHODS

C57/BL6 mice were used in vivo experiments. PAA model was established using a brush friction method. Visual scoring and hematoxylin and eosin staining were used to score the severity of adhesions. Network pharmacology was used to infer potential targets and core pathways of LUT. Hydrogen peroxide (H2O2) was used to induce oxidative stress in vitro, while the reactive oxygen species (ROS) assay kit was used to evaluate oxidative stress levels. Western blotting, cell immunofluorescence, and multiple immunofluorescence assays were used to detect α-SMA, vimentin, E-cadherin, collagen I, or AKT phosphorylation level. Scratch assay was used to detect cell migration.

RESULTS

LUT reduced the degree of PAA in mice. It attenuated H2O2-induced ROS production and reversed mesothelial-mesenchymal transition (MMT) in HMrSV5 cells. Network pharmacology analysis showed that LUT likely exerted anti-adhesion activity by regulating the PI3K-Akt signaling pathway. Phosphorylated Akt levels were significantly reduced in LUT-treated HMrSV5 cells. LUT also significantly reduced the expression of vimentin and collagen I in adherent tissues and upregulated E-cadherin expression.

CONCLUSION

LUT blocks the ROS/PI3K/AKT pathway, thereby inhibiting MMT and reducing PAA. To this end, LUT has potential in PAA therapy.