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Krediet RT. Physiology of peritoneal dialysis; pathophysiology in long-term patients. Front Physiol 2024; 15:1322493. [PMID: 39193440 PMCID: PMC11347314 DOI: 10.3389/fphys.2024.1322493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 07/10/2024] [Indexed: 08/29/2024] Open
Abstract
The microvascular wall of peritoneal tissues is the main barrier in solute and water transport in the initial phase of peritoneal dialysis (PD). Small solute transport is mainly by diffusion through inter-endothelial pores, as is hydrostatic fluid transport with dissolved solutes. Water is also transported through the intra-endothelial water channel aquaporin-1(AQP-1) by a glucose-induced crystalloid osmotic gradient (free water transport). In the current review the physiology of peritoneal transport will be discussed both during the first years of PD and after long-term treatment with emphasis on the peritoneal interstitial tissue and its role in free water transport. Attention will be paid to the role of glucose-induced pseudohypoxia causing both increased expression of fibrogenetic factors and of the glucose transporter GLUT-1. The former leads to peritoneal fibrosis, the latter to a reduced crystalloid osmotic gradient, explaining the decrease in free water transport as a cause of ultrafiltration failure. These phenomena strongly suggest that the extremely high dialysate glucose concentrations are the driving force of both morphologic and functional peritoneal alterations that may develop during long-term PD.
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Malho Guedes A, Marques RC, Domingos AT, Laranjo C, Silva AP, Rodrigues A, Krediet RT. Peritoneal Protein Loss With Time in Peritoneal Dialysis. Semin Dial 2024; 37:242-248. [PMID: 38420712 DOI: 10.1111/sdi.13194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/22/2023] [Accepted: 01/28/2024] [Indexed: 03/02/2024]
Abstract
Longitudinal evolution of peritoneal protein loss (PPL), a reflection of hydrostatic pressure-driven leak of plasma proteins through the large-pore pathway, is not clear. Time on PD causes loss of mesothelial cells, vasculopathy, and increased thickness of the submesothelial fibrous layer. Are these structural changes associated with progressive increase of PPL, in a parallel with the rise in the D/P creatinine? The aim of the present study was to identify longitudinal changes of PPL over time. This single-center, longitudinal study included 52 peritoneal dialysis (PD) patients with a median follow-up of 26.5 months, evaluated at two different time points with a minimum interval of 6 months. Repeated measures analysis was performed using paired sample t-test or the nonparametric Wilcoxon signed-rank test, depending on the distribution. After a median interval of 15.5 months, lower levels of residual renal function and urine volume, lower Kt/V, and creatinine clearance were found. D/P creatinine and PPL were stable, but a decrease in ultrafiltration was present. Systemic inflammation, nutrition, and volume overload showed no significant change with time on PD. Analysis of a subpopulation with over 48 months between initial and subsequential assessment (n = 11) showed again no difference in inflammation, nutritional and hydration parameters from baseline, but importantly PPL decreased after more than 4 years on PD (mean difference 1.2 g/24, p = 0.033). D/P creatinine and dip of sodium remained unchanged. The absence of deleterious effects of time on PD is reassuring, pointing to the benefit of updated PD prescription, including the standard use of more biocompatible solutions towards membrane preservation and adjusted prescription avoiding overhydration and inflammation while maintaining nutritional status. After controlling for confounders, PPL may act as a biomarker of acquired venous vasculopathy, even if small pore fluid transport rates and free water transport are preserved.
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Affiliation(s)
- Anabela Malho Guedes
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
- Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar, e ITR - Laboratory for Integrative and Translational Research in Population Health, Universidade do Porto, Porto, Portugal
| | | | - Ana Teresa Domingos
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
| | - Céu Laranjo
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
| | - Ana Paula Silva
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
| | - Anabela Rodrigues
- Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar, e ITR - Laboratory for Integrative and Translational Research in Population Health, Universidade do Porto, Porto, Portugal
- Serviço de Nefrologia, Centro Hospitalar Universitário de Santo António, Porto, Portugal
| | - Raymond T Krediet
- Division of Nephrology, Department of Medicine, Amsterdam University Medical Centre, Amsterdam, The Netherlands
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Zou C, Zhang X, Xu Y, Yin J. Recent Advances Regarding Polyphenol Oxidase in Camellia sinensis: Extraction, Purification, Characterization, and Application. Foods 2024; 13:545. [PMID: 38397522 PMCID: PMC10887689 DOI: 10.3390/foods13040545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 01/31/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
Polyphenol oxidase (PPO) is an important metalloenzyme in the tea plant (Camellia sinensis). However, there has recently been a lack of comprehensive reviews on Camellia sinensis PPO. In this study, the methods for extracting PPO from Camellia sinensis, including acetone extraction, buffer extraction, and surfactant extraction, are compared in detail. The main purification methods for Camellia sinensis PPO, such as ammonium sulfate precipitation, three-phase partitioning, dialysis, ultrafiltration, ion exchange chromatography, gel filtration chromatography, and affinity chromatography, are summarized. PPOs from different sources of tea plants are characterized and systematically compared in terms of optimal pH, optimal temperature, molecular weight, substrate specificity, and activators and inhibitors. In addition, the applications of PPO in tea processing and the in vitro synthesis of theaflavins are outlined. In this review, detailed research regarding the extraction, purification, properties, and application of Camellia sinensis PPO is summarized to provide a reference for further research on PPO.
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Affiliation(s)
- Chun Zou
- Key Laboratory of Biology, Tea Research Institute, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Hangzhou 310008, China
| | - Xin Zhang
- Key Laboratory of Biology, Tea Research Institute, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Hangzhou 310008, China
| | - Yongquan Xu
- Key Laboratory of Biology, Tea Research Institute, Chinese Academy of Agricultural Sciences, Ministry of Agriculture and Rural Affairs, Hangzhou 310008, China
| | - Junfeng Yin
- National Engineering Research Center for Tea Processing, Hangzhou 310008, China
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Malho Guedes A, Calças Marques R, Ribeiro B, Fernandes MT, Faísca M, Silva AP, Bragança J, Rodrigues A. Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths. Front Med (Lausanne) 2022; 9. [DOI: https:/doi.org/10.3389/fmed.2022.884061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023] Open
Abstract
Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162–31.854), LBMI (p = 0.008; 95%CI: 1.720–11.219) and performing CAPD (p = 0.023; 95%CI: 4.375–54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235–2.913), overhydration (HR: 10.034, 95%CI: 1.426–70.587) and lower PPL (HR: 0.576, 95%CI: 0.339–0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.
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Malho Guedes A, Calças Marques R, Ribeiro B, Fernandes MT, Faísca M, Silva AP, Bragança J, Rodrigues A. Peritoneal Protein Loss, Inflammation, and Nutrition: Refuting Myths. Front Med (Lausanne) 2022; 9:884061. [PMID: 35692552 PMCID: PMC9178188 DOI: 10.3389/fmed.2022.884061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/11/2022] [Indexed: 11/17/2022] Open
Abstract
Peritoneal protein loss (PPL) has been correlated with mortality, malnutrition and inflammation. More recently overhydration was brought to the equation. This study aims to review classic and recent factors associated with PPL. Prevalent and incident peritoneal dialysis (PD) patients were included. Dialysate and serum IL-6 was obtained during PET. Hydration and nutritional status were assessed by bio-impedance. Linear regression and Cox regression were performed. The 78 included patients presented median values of PPL 4.8 g/24 h, serum IL-6: 5.1 pg/mL, and IL-6 appearance rate 153.5 pg/min. Mean extracellular water excess (EWexc) was 0.88 ± 0.94 L, and lean body mass index (LBMI) 17.3 ± 2.4 kg/m2. After mean follow-up of 33.9 ± 29.3 months, 12 patients died. Linear univariable analysis showed positive associations between PPL and small solute transport, body composition (LBMI and EWexc), comorbidities and performing CAPD (vs. cycler). PPL correlated positively with dialysate appearance rate of IL-6, but not with serum IL-6. Linear multivariable analysis confirmed positive association between PPL and EWexc (p = 0.012; 95%CI: 4.162-31.854), LBMI (p = 0.008; 95%CI: 1.720-11.219) and performing CAPD (p = 0.023; 95%CI: 4.375-54.190). In survival analysis, no relationship was found between mortality and PPL. Multivariable Cox regression showed Charlson Comorbidity Index (HR: 1.896, 95%CI: 1.235-2.913), overhydration (HR: 10.034, 95%CI: 1.426-70.587) and lower PPL (HR: 0.576, 95%CI: 0.339-0.978) were predictors for mortality. Overhydration, was a strong predictor of PPL, overpowering variables previously reported as determinants of PPL, namely clinical correlates of endothelial dysfunction or local inflammation. PPL were not associated with malnutrition or higher mortality, emphasizing the importance of volume overload control in PD patients.
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Affiliation(s)
- Anabela Malho Guedes
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
- Faculdade de Medicina e Ciências Biomédicas, Universidade do Algarve, Faro, Portugal
- UMIB - Unidade Multidisciplinar de Investigação Biomédica, ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | | | - Brigitte Ribeiro
- Faculdade de Medicina e Ciências Biomédicas, Universidade do Algarve, Faro, Portugal
| | - Mónica T. Fernandes
- Escola Superior de Saúde, Universidade do Algarve, Faro, Portugal
- Algarve Biomedical Center, Universidade do Algarve, Faro, Portugal
- Algarve Biomedical Center Research Institute, Universidade do Algarve, Faro, Portugal
| | | | - Ana Paula Silva
- Serviço de Nefrologia, Centro Hospitalar Universitário do Algarve, Faro, Portugal
- Faculdade de Medicina e Ciências Biomédicas, Universidade do Algarve, Faro, Portugal
| | - José Bragança
- Faculdade de Medicina e Ciências Biomédicas, Universidade do Algarve, Faro, Portugal
- Algarve Biomedical Center, Universidade do Algarve, Faro, Portugal
- Algarve Biomedical Center Research Institute, Universidade do Algarve, Faro, Portugal
- Champalimaud Research Program, Champalimaud Center for the Unknown, Lisbon, Portugal
| | - Anabela Rodrigues
- UMIB - Unidade Multidisciplinar de Investigação Biomédica, ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
- Serviço de Nefrologia, Centro Hospitalar Universitário do Porto, Porto, Portugal
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal
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