Efectos de la diálisis y del estado urémico sobre la modulación del apetito y el síndrome MIA (malnutrición, inflamación y ateroesclerosis) en pacientes en diálisis

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina. Departamento de Medicina. Fecha de lectura: 25 de enero de 2007

Angiogenesis and Lymphangiogenesis in Peritoneal Dialysis

The ultrafiltration failure during peritoneal dialysis (PD) is related to inflammatory responses induced by bio-incompatible PD fluids, which may lead to deterioration of peritoneal membrane (PM) function. Mesothelial cells, lymphocytes, macrophages and other cell types present in the peritoneal cavity are stimulated to produce cytokines and growth factors that promote pathological processes. Due to these factors, blood and lymphatic vessels proliferate and could be responsible for hyperfiltration and PM failure type III and IV. Vessels proliferation may be related to fibrosis, being the cause and/or effect of the mesenchymal conversion of different cell types such as mesothelial (MMT), bone marrow-derived (fibrocytes) or endothelial (vascular- and lymph-endo-MT) cells. Lymphangiogenesis in PD is a poorly analysed process; however, its contribution to peritoneal function disorders has been recently recognized. VEGF production is associated with blood and lymphatic vessels proliferation, while specifically lymphangiogenesis is mainly regulated by VEGF-C and VEGF-D. Excessive lymphatic fluid drainage from the abdominal cavity may be related with macromolecule and isosmotic solutions reuptake and convective reabsorption of solutes that were cleared from plasma by diffusion. Some drugs have been shown to modulate tissue fibrosis, MMT, EndoMT, angiogenesis and lymphangiogenesis and could represent interesting therapeutic strategies to protect the PM

Pharmacological Preservation of Peritoneal Membrane in Peritoneal Dialysis

Peritoneal dialysis (PD) is an established renal replacement therapy for renal disease. It is based on the capacity of the peritoneum to act as a semipermeable membrane for the exchange of toxic solutes and water, which is called ultrafiltration capacity. Peritoneal membrane (PM) is lined by a monolayer of mesothelial cells (MCs), which lay on an extracellular matrix bed where other cell types and blood and lymphatic vessels can be found. Long-term exposure to hyperosmotic PD fluids (PDFs), peritonitis or hemoperitoneum causes peritoneal injury by the generation of an inflammatory state. Inflammatory cells and their mediators initiate a cascade of reactions promoting alterations in peritoneal cells, loss of MCs, fibrosis, vasculopathy, and angiogenesis, leading to ultrafiltration failure. Recent studies support that the so-called “mesothelial to mesenchymal transition” process of the MCs runs parallel to the anatomical and functional ridging of PM, which suggests that its inhibition might slow down or stop the PM damage. The fight against PM damage begins with the improvement in PDF biocompatibility. Complementary to this, an alternative approach to preserve the PM might be the use of pharmacological agents or molecular strategies. Here, we explain the existing research models for the development of new therapies and analyze several therapeutic options tested with them

Abnormalities in Glucose Metabolism, Appetite-Related Peptide Release, and Pro-inflammatory Cytokines Play a Central Role in Appetite Disorders in Peritoneal Dialysis

Background: Appetite disorders are frequent and scantly studied in peritoneal dialysis (PD) patients and are associated with malnutrition and cardiovascular complications.Objective: We investigated the relationship between uremic insulin resistance, pro-inflammatory cytokines, and appetite-related peptides release (ARPr) with eating-behavior disorders in PD patients.Methods: We included 42 PD patients (12 suffering anorexia, 12 obese with high food-intake, and 18 asymptomatic) and 10 controls. We measured blood levels of ARPr including orexigens [neuropeptide-Y (NPY), ghrelin, and nitric-oxide], anorexigens [cholecystokinin, insulin, corticotropin-releasing factor, leptin, and adiponectin (Ad)], and cytokines (TNF-α, sTNFα-R2, and IL-6) both at baseline and after administering a standard-food stimulus (SFS). We also measured the expression of TNF-α, leptin and Ad-encoding mRNAs in abdominal adipose tissue. We compared these markers with eating motivation measured by a Visual Analog Scale (VAS).Results: Anorexics showed both little appetite, measured by a VAS, and low levels of orexigens that remained constant after SFS, coupled with high levels of anorexigens at baseline and after SFS. Obeses showed higher appetite, increased baseline levels of orexigens, lower baseline levels of anorexigens and cytokines and two peaks of NPY after SFS. The different patterns of ARPr and cytokines pointed to a close relationship with uremic insulin resistance. In fact, the euglycemic–hyperglycemic clamp reproduced these disorders. In anorexics, TNF-α fat expression was increased. In obese patients, leptin expression in fat tissue was down-regulated and showed correlation with the appetite.Conclusion: In PD, appetite is governed by substances that are altered at baseline and abnormally released. Such modulators are controlled by insulin metabolism and cytokines and, while anorexics display inflammatory predominance, obese patients predominantly display insulin resistance

Poesía

Compilación de poesía de 5 autores

Aislamiento de microorganismos a partir del fluido digestivo de larvas de Rhynchophorus palmarum (Coleoptera: Curculionidae)

A The objective was to isolate bacteria, yeasts and an ascomycete fungus from the digestive fluid of Rhynchophorus palmarum larvae. The larvae were acquired in typical product markets of the Amazon. The specimens were selected according to their approximate weight and size, to later be dissected under sterile conditions and obtain a suspension of intestinal fluid, which was diluted and sown in solid and liquid medium. For microbial isolation, approaches were considered for the culture of bacteria and fungi or yeasts, both under aerobic, anaerobic and microaerophilic conditions. The isolated colonies were brought up to pure cultures, obtaining a total of fourteen isolates, mostly represented by Gram negative bacilli and, to a lesser extent, by fungi and yeasts. Regarding their oxygen requirement, most of the isolates correspond to aerobic microorganisms, with a scarce presence of anaerobic and microaerophilic isolates.Se tuvo como objetivo aislar bacterias, levaduras y un hongo ascomiceto, a partir del fluido digestivo de larvas de Rhynchophorus palmarum. Las larvas fueron adquiridas en mercados de productos típicos de la Amazonia. Los ejemplares se seleccionaron de acuerdo a su peso y talla aproximados, para luego ser disecados en condiciones de esterilidad y obtener una suspensión de fluido intestinal, que fue diluida y sembrada en medio sólido y líquido. Para el aislamiento microbiano, se consideraron aproximaciones para el cultivo de bacterias y hongos o levaduras, tanto en condiciones aeróbicas como anaeróbicas y microaerófilas. Las colonias aisladas se llevaron hasta cultivos puros, obteniéndose un total de catorce aislados, representados en su mayoría por bacilos Gram negativos y, en menor proporción por hongos y levaduras. En cuanto a su requerimiento de oxígeno, la mayoría de los aislados corresponde a microorganismos aeróbicos, con una escasa presencia de aislados anaeróbicos y microaerófilos

Functional relevance of the switch of VEGF receptors/co-receptors during peritoneal dialysis-induced mesothelial to mesenchymal transition

Vascular endothelial growth factor (VEGF) is up-regulated during mesothelial to mesenchymal transition (MMT) and has been associated with peritoneal membrane dysfunction in peritoneal dialysis (PD) patients. It has been shown that normal and malignant mesothelial cells (MCs) express VEGF receptors (VEGFRs) and co-receptors and that VEGF is an autocrine growth factor for mesothelioma. Hence, we evaluated the expression patterns and the functional relevance of the VEGF/VEGFRs/co-receptors axis during the mesenchymal conversion of MCs induced by peritoneal dialysis. Omentum-derived MCs treated with TGF-β1 plus IL-1β (in vitro MMT) and PD effluent-derived MCs with non-epithelioid phenotype (ex vivo MMT) showed down-regulated expression of the two main receptors Flt-1/VEGFR-1 and KDR/VEGFR-2, whereas the co-receptor neuropilin-1 (Nrp-1) was up-regulated. The expression of the Nrp-1 ligand semaphorin-3A (Sema-3A), a functional VEGF competitor, was repressed throughout the MMT process. These expression pattern changes were accompanied by a reduction of the proliferation capacity and by a parallel induction of the invasive capacity of MCs that had undergone an in vitro or ex vivo MMT. Treatment with neutralizing anti-VEGF or anti-Nrp-1 antibodies showed that these molecules played a relevant role in cellular proliferation only in naïve omentum-derived MCs. Conversely, treatment with these blocking antibodies, as well as with recombinant Sema-3A, indicated that the switched VEGF/VEGFRs/co-receptors axis drove the enhanced invasion capacity of MCs undergoing MMT. In conclusion, the expression patterns of VEGFRs and co-receptors change in MCs during MMT, which in turn would determine their behaviour in terms of proliferation and invasion in response to VEGFThis work was supported by grant SAF2010-21249 from the ‘‘Ministerio de Economía y Competitividad’’ to M.L.C. and by grant S2010/BMD-2321 from ‘‘Comunidad Autónoma de Madrid’’ to M.L.C. and R.S. This work was also partially supported by grants PI 09/0776 from ‘‘Fondo de Investigaciones Sanitarias’’ to A.A., and RETICS 06/0016 (REDinREN, Fondos FEDER, EU) to R.S

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 processThis work was supported by grant SAF2010-21249 from the ‘‘Ministerio de Economia y Competitividad’’ to MLC and by grant S2010/BMD-2321 from ‘‘Comunidad Autónoma de Madrid’’ to MLC and RS. This work was also partially supported by grants PI 09/0776 from ‘‘Fondo de Investigaciones Sanitarias’’ to AA, and RETICS 06/0016 (REDinREN, Fondos FEDER, EU) to R