Bajo Ma

Serum concentrations of leptin, adiponectin and resistin, and their relationship with cardiovascular disease in patients with end‐stage renal disease

Background and Objective  High levels of some adipocytokines have been reported in patients with chronic renal failure, but little information is available on adipocytokine concentrations in uraemic patients under different modalities of therapy. Our aims were (1) to quantify the serum concentrations of leptin, adiponectin and resistin in uraemic patients on peritoneal dialysis (PD) and haemodialysis (HD), in comparison with patients on conservative management, and (2) to study the relationships between adipocytokine levels and previous atherosclerotic vascular disease.

Eating behavior disorders in uremia: a question of balance in appetite regulation.

Eating and appetite disorders are frequent complications of the uremic syndrome which contribute to malnutrition in dialysis patients. The data suggest that uremic anorexia may occur with or without abdominal and visceral fat accumulation despite a lower food intake. This form of obesity (i.e., with low food intake and malnutrition) is more common in dialysis patients than obesity with high food intake. This article reviews the current knowledge regarding mechanisms responsible for appetite regulation in normal conditions and in uremic patients. Anorexia in dialysis patients has been historically considered as a sign of uremic toxicity due to ‘‘inadequate’’ dialysis as judged by uncertain means (‘‘middle molecule’’ accumulation, Kt/V, ‘‘peak‐concentration hypothesis,’’ and others). We propose the tryptophan‐serotonin hypothesis, based on a uremia‐induced disorder in patients’ amino acid profile—low concentrations of large neutral and branched‐chain amino acids with high tryptophan levels. A high rate of tryptophan transport across the blood‐brain barrier increases the synthesis of serotonin, a major appetite inhibitor. Inflammation may also play a role in the genesis of anorexia and malnutrition. For example, silent infection with Helicobacter pylori may be a source of cytokines with cachectic action; its eradication improves appetite and nutrition. The evaluation of appetite should take into account cultural and social aspects. Uremic patients showed a universal trend to carbohydrate preference and red meat refusal compared to healthy people. In contrast, white meat was less problematic. Uremic patients also have a remarkable attraction for citrics and strong flavors in general. Eating preferences or refusals have been related to the predominance of some appetite peptide modulators. High levels of cholecystokinin (CCK) (a powerful anorexigen) are associated with early satiety for carbohydrates and neuropeptide Y (NPY) (an orexigen) with repeated food intake. Obesity and elevated body mass index often falsely suggest a good nutritional status. In uremic patients (a hyperinsulinemia state), disorders in the regulation of fat distribution (insulin, leptin, insulin‐like growth factor [IGF]‐1, fatty acids, and disorders in receptors for insulin, lipoprotein lipase, mitochondrial uncoupling protein‐2, and β3‐adrenoreceptors) may cause abdominal fat accumulation without an increase in appetite. Finally, appetite regulation in uremia is highly complex. Disorders in adipose tissue, gastrointestinal and neuropeptides, retained or hyperproduced inflammatory end products, and central nervous system changes may all play a role. Uremic anorexia may be explained by a hypothalamic hyperserotoninergic state derived from a high concentration of tryptophan and low branched‐chain amino acids.

Alternative activation of macrophages in human peritoneum: implications for peritoneal fibrosis

BACKGROUND Depending on the cytokine microenvironment, macrophages (Mϕ) can adopt a proinflammatory (M1) or a profibrotic (M2) phenotype characterized by the expression of cell surface proteins such as CD206 and CD163 and soluble factors such as CC chemokine ligand 18 (CCL18). A key role for Mϕ in fibrosis has been observed in diverse organ settings. We studied the Mϕ population in a human model of peritoneal dialysis in which continuous stress due to dialysis fluids and recurrent peritonitis represent a risk for peritoneal membrane dysfunction reflected as ultrafiltration failure (UFF) and peritoneal fibrosis. METHODS We used flow cytometry and quantitative reverse transcription-polymerase chain reaction to analyse the phenotype of peritoneal effluent Mϕ and tested their ability to stimulate the proliferation of human fibroblasts. Mϕ from non-infected patients were compared with those from patients with active peritonitis. Cytokine production was evaluated by enzyme-linked immunosorbent assay (ELISA) in spent dialysates and cell culture supernatants. RESULTS CD206(+) and CD163(+) M2 were found within peritoneal effluents by flow cytometry analysis, with increased frequencies of CD163(+) cells during peritonitis (P = 0.003). TGFB1, MMP9 and CCL18 messenger RNA (mRNA) levels in peritoneal macrophages (pMϕ) were similar to those found in M2 cells differentiated in vitro. The ability of pMϕ to stimulate fibroblast proliferation correlated with CCL18 mRNA levels (r = 0.924, P = 0.016). CCL18 production by pMϕ was confirmed by immunostaining of cytospin samples and ELISA. Moreover, CCL18 effluent concentrations correlated with decreased peritoneal function, which was evaluated as dialysate to plasma ratio of creatinine (r = 0.724, P < 0.0001), and were significantly higher in patients with UFF (P = 0.0025) and in those who later developed sclerosing peritonitis (P = 0.024). CONCLUSIONS M2 may participate in human peritoneal fibrosis through the stimulation of fibroblast cell growth and CCL18 production as high concentrations of CCL18 are associated with functional deficiency and fibrosis of the peritoneal membrane.

Effects of rapamycin on the epithelial-to-mesenchymal transition of human peritoneal mesothelial cells

The preservation of the peritoneal membrane is crucial for long-term survival in peritoneal dialysis. Epithelial-to-mesenchymal transition (EMT) is a process demonstrated in mesothelial cells (MC), responsible for negative peritoneal changes and directly related to PD. EMT enables neovascularization and fibrogenic capabilities in MC. Vascular endothelial growth factor (VEGF) is the mediator for neo-vascularization. Rapamycin is a potent immunosuppressor with antifibrotic action in renal allografts and has a demonstrated anti-VEGF effect. We performed this study with the hypothesis that rapamycin may regulate the EMT of MC. MC from human omentum were cultured. When mesothelial cells reached confluence, some of them were stimulated with r-TGF-ß (1 ng/mL) to induce EMT, co-administered with rapamycin (0.2, 2, 4, 20 and 40 nM). Other groups of cells received similar doses of rapamycin or r-TGF-ß, separately. Cells were analyzed at 6, 24, 48 hours and 7 days. As markers of EMT we included α-SMA, E-cadherin and snail nuclear factor by quantitative RT-PCR. EMT markers and regulators demonstrated the following changes with rapamycin: E-cadherin (a protective gene for EMT) increased 2.5-fold relative to controls under 40 nM, at 24h. Importantly, rapamycin inhibited snail expression induced by TGF-ß at 6h, whereas TGF-ß increased snail 10fold. At day 7, rapamycin showed no anti-EMT properties. An important decrease in α-SMA expression by MC after rapamycin addition was observed. In conclusion, rapamycin shows a mild protective effect on EMT, as it increases E-cadherin and decreases α-SMA expression. Consequently, rapamycin might partially regulate the epithelial-to-mesenchymal transition of mesothelial cells.

Serum ghrelin concentrations in patients with chronic renal failure undergoing dialysis

Background   Ghrelin is a recently discovered protein hormone mainly synthesized in the gastric endocrine cells. This hormone not only is a potent growth hormone secretagogue but also is involved in the regulation of food ingestion and energy metabolism. Derangements in ghrelin secretion in patients with chronic renal failure (CRF) have not been fully evaluated.

Tamoxifen Ameliorates Peritoneal Membrane Damage by Blocking Mesothelial to Mesenchymal Transition in Peritoneal Dialysis

Mesothelial-to-mesenchymal transition (MMT) is an auto-regulated physiological process of tissue repair that in uncontrolled conditions such as peritoneal dialysis (PD) can lead to peritoneal fibrosis. The maximum expression of peritoneal fibrosis induced by PD fluids and other peritoneal processes is the encapsulating peritoneal sclerosis (EPS) for which no specific treatment exists. Tamoxifen, a synthetic estrogen, has successfully been used to treat retroperitoneal fibrosis and EPS associated with PD. Hence, we used in vitro and animal model approaches to evaluate the efficacy of Tamoxifen to inhibit the MMT as a trigger of peritoneal fibrosis. In vitro studies were carried out using omentum-derived mesothelial cells (MCs) and effluent-derived MCs. Tamoxifen blocked the MMT induced by transforming growth factor (TGF)-β1, as it preserved the expression of E-cadherin and reduced the expression of mesenchymal-associated molecules such as snail, fibronectin, collagen-I, α-smooth muscle actin, and matrix metalloproteinse-2. Tamoxifen-treatment preserved the fibrinolytic capacity of MCs treated with TGF-β1 and decreased their migration capacity. Tamoxifen did not reverse the MMT of non-epitheliod MCs from effluents, but it reduced the expression of some mesenchymal molecules. In mice PD model, we demonstrated that MMT progressed in parallel with peritoneal membrane thickness. In addition, we observed that Tamoxifen significantly reduced peritoneal thickness, angiogenesis, invasion of the compact zone by mesenchymal MCs and improved peritoneal function. Tamoxifen also reduced the effluent levels of vascular endothelial growth factor and leptin. These results demonstrate that Tamoxifen is a therapeutic option to treat peritoneal fibrosis, and that its protective effect is mediated via modulation of the MMT process.

Growth hormone, IGF‐I and its binding proteins (IGFBP‐1 and ‐3) in adult uraemic patients undergoing peritoneal dialysis and haemodialysis

objective  The GH/IGF axis is altered in chronic renal failure (CRF). CRF patients usually show normal or high serum concentrations of GH and IGF‐I, whereas all IGF binding proteins (IGFBP‐1 to ‐6), except IGFBP‐5, considerably increase with declining renal function. The aims of the present study were to quantify serum concentrations of GH, IGF‐I, IGFBP‐1 and IGFBP‐3 in a group of patients with CRF, and determine whether there were differences according to the type of dialysis, that is, peritoneal dialysis (PD) and haemodialysis (HD).

Preserving the Peritoneal Dialysis Membrane in Long-Term Peritoneal Dialysis Patients

A functional peritoneal membrane, which forms a semipermeable barrier between capillary blood flow and the dialysate compartment, is necessary for successful peritoneal dialysis. The relationship between structure and fluid dynamics is the key factor in the removal of a suitable amount of solute and water to assure the continuous replacement of the lost renal function (1). The inception of continuous ambulatory peritoneal dialysis (CAPD) in the late 1970s has led to the appearance of a new class of patients, those who have been treated with PD for over a decade. However, many patients do not remain on peritoneal dialysis long term due to peritoneal functional instability, with ultrafiltration loss and severe anatomical changes (tanned and sclerotic peritoneum) (2, 3-9). The scanty literature available on longitudinal function and/or anatomical changes precludes defining the period for which PD is really possible. J. Dobbie (personal communication) has divided peritoneal membrane durability into (i) dialysis membrane durability, the period in which the membrane provides sufficient solute and water transport, and (ii) vital membrane durability, the period in which the peritoneal membrane remains a selflubricating, nonstick surface allowing normal bowel motility. The tools available for estimation of peritoneal responses to PD include anatomic (biopsy, cytology) (lo), image-dependent (abdominal CT scan, peritoneogram with 99Tc-albumin) (1 l) , and functional measures (convective transport estimated by ultrafiltration capacity and diffusive transport estimated by peritoneal equilibration for small molecular weight solutes) (12-20).

Influence of Bicarbonate/Low-GDP Peritoneal Dialysis Fluid (Bicavera) on In Vitro and Ex Vivo Epithelial-to-Mesenchymal Transition of Mesothelial Cells

♦ Background: Peritoneal membrane damage induced by peritoneal dialysis (PD) is largely associated with epithelial-to-mesenchymal transition (EMT) of mesothelial cells (MCs), which is believed to be a result mainly of the glucose degradation products (GDPs) present in PD solutions. ♦ Objectives: This study investigated the impact of bicarbonate-buffered, low-GDP PD solution (BicaVera: Fresenius Medical Care, Bad Homburg, Germany) on EMT of MCs in vitro and ex vivo. ♦ Methods: In vitro studies: Omentum-derived MCs were incubated with lactate-buffered standard PD fluid or BicaVera fluid diluted 1:1 with culture medium. Ex vivo studies: From 31 patients randomly distributed to either standard or BicaVera solution and followed for 24 months, effluents were collected every 6 months for determination of EMT markers in effluent MCs. ♦ Results: Culturing of MCs with standard fluid in vitro resulted in morphology change to a non-epithelioid shape, with downregulation of E-cadherin (indicative of EMT) and strong induction of vascular endothelial growth factor (VEGF) expression. By contrast, in vitro exposure of MCs to bicarbonate/low-GDP solution had less impact on both EMT parameters. Ex vivo studies partially confirmed the foregoing results. The BicaVera group, with a higher prevalence of the non-epithelioid MC phenotype at baseline (for unknown reasons), showed a clear and significant trend to gain and maintain an epithelioid phenotype at medium- and longer-term and to show fewer fibrogenic characteristics. By contrast, the standard solution group demonstrated a progressive and significantly higher presence of the non-epithelioid phenotype. Compared with effluent MCs having an epithelioid phenotype, MCs with non-epithelioid morphology showed significantly lower levels of E-cadherin and greater levels of fibronectin and VEGF. In comparing the BicaVera and standard solution groups, MCs from the standard solution group showed significantly higher secretion of interleukin 8 and lower secretion of collagen I, but no differences in the levels of other EMT-associated molecules, including fibronectin, VEGF, E-cadherin, and transforming growth factor β1. Peritonitis incidence was similar in both groups. Functionally, the use of BicaVera fluid was associated with higher transport of small molecules and lower ultrafiltration capacity. ♦ Conclusions: Effluent MCs grown ex vivo from patients treated with bicarbonate/low-GDP BicaVera fluid showed a trend to acquire an epithelial phenotype, with lower production of proinflammatory cytokines and chemokines (such as interleukin 8) than was seen with MCs from patients treated with a lactate-buffered standard PD solution.

High Stable Serum Adiponectin Levels Are Associated with a Better Outcome in Prevalent Dialysis Patients

Aims: Our aim was to evaluate the prognostic value of 2 measurements of serum adiponectin levels for all-cause mortality and cardiovascular (CV) mortality in uremic patients. Methods: We analyzed 184 patients (19–86 years) undergoing peritoneal dialysis (n = 86) or hemodialysis (n = 98). All patients had 2 measurements of serum adiponectin levels (at baseline and after 1 year). Relationships between adiponectin and mortality were studied by means of survival analysis and Cox regression analysis. Results: During a median follow-up time of 31.2 months, 67 patients (36.4%) died, 26 (14.1%) as a result of CV disease. Mean survival time for CV mortality in patients with 1-year adiponectin values in the upper tertile was significantly higher than that found in patients in the middle and lower tertiles. Hazard ratios (HR) for all-cause mortality per SD change were 0.70 (95% CI, 0.50–0.98; p < 0.05) for baseline adiponectin levels and 0.68 (0.49–0.95; p < 0.05) for mean baseline and 1-year adiponectin levels. Mean adiponectin levels were also negatively related with CV mortality [HR 0.43 (0.21–0.86); p < 0.05] and CV events [HR 0.74 (0.55–0.99); p < 0.05]. Conclusions: In this population of dialysis patients, adiponectin seems to behave as a CV protective factor. Patients with high mean adiponectin levels had a better survival rate.