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The article relates the authors' perspective concerning the use of peritoneal membrane for long-term dialysis. The authors contend that the expansion of peritoneal dialysis (PD) is limited by the incapacity of the peritoneal membrane to perform the needed solute and water transport in the long term. They argue that the functional consequence of this capacity limitation is ultrafiltration failure related to the damage induced by PD fluids and peritonitis.

BACKGROUND Hypothalamic cholinergic neurotransmission plays a major role in the regulation of GH secretion. Pyridostigmine, a cholinesterase inhibitor, is able to decrease hypothalamic somatostatinergic tone and release GH in normal subjects. Blockade of muscarinic receptor with pirenzepine blunts the GH release in several clinical situations. However, little information is available on the role played by central cholinergic pathways in GH regulation in uraemic patients. OBJECTIVE We aimed to assess GH responses to GHRH after pretreatment with pyridostigmine and pirenzepine in a group of uraemic patients undergoing peritoneal dialysis (PD). GH responses of the patients treated with recombinant human erythropeitin (rhEPO) were compared to patients without treatment. DESIGN We studied 14 male patients on PD and nine control subjects. All subjects underwent three endocrine test in random order after an overnight fast. Each subject received GHRH (100 μg, i.v. in bolus at 0 minutes). Sixty minutes before the injection of GHRH subjects were given oral placebo, pyridostigmine (120 mg), or pirenzepine (100 mg). MEASUREMENTS Blood samples for GH were collected at -60, 0, 15, 30, 45, 60 and 90 minutes The hormonal secretory responses were studied by a time-averaged (area under the curves, AUC) and time-independent (peak values) analysis. RESULTS Baseline GH concentrations were similar in patients and controls. GH responses to placebo plus GHRH were also comparable in patients and controls (peak 26.6 ± 3.8 vs. 33.2 ± 4.4 mU/l, AUC 28.2 ± 3.4 vs. 27.8 ± 4.6 mU/h/l). Pyridostigmine administration induced a significant potentiation of GH responses to GHRH both in patients (peak 43.2 ± 5.2 mU/l, AUC 47.6 ± 6.0 mU/h/l; P < 0.01) and in control subjects (peak 79.2 ± 8.6 mU/l, AUC 78.0 ± 9.4 mU/h/l; P < 0.01). However, the increment in GH peak and AUC was significantly (P < 0.05) greater in controls in relation to values found in... [ABSTRACT FROM AUTHOR]

A system for sorbent‐assisted peritoneal dialysis (SAPD) has been developed that continuously recirculates dialysate via a tidal mode using a single‐lumen peritoneal catheter with the regeneration of spent dialysate by means of sorbents. SAPD treatment may improve plasma clearance by the maintenance of a high plasma‐to‐dialysate concentration gradient and by increasing the mass transfer area coefficient (MTAC) of solutes. The system is designed for daily 8‐hr treatment (12 kg, nighttime system). A wearable system (2.3 kg, daytime system) may further enhance the clearance of phosphate and organic waste solutes during the day. Uremic pigs (n = 3) were treated with the day‐ (n = 3) and nighttime system (n = 15) for 4–8 hr per treatment. Plasma clearance (Cl), MTAC, and total mass transport (MT) of urea, creatinine, phosphate, and potassium were compared with a static dwell (n = 28). Cl, MTAC, and MT of urea, creatinine, phosphate, and potassium were low in the pig as compared to humans due to the pig's low peritoneal transport status and could be enhanced only to a limited extent by SAPD treatment compared with a static dwell (nighttime system: Cl urea: ×1.5 (p =.029), Cl creatinine: ×1.7 (p =.054), Cl phosphate: ×1.5 (p =.158), Cl potassium: ×1.6 (p =.011); daytime system: Cl creatinine: ×2.7 (p =.040), Cl phosphate: ×2.2 (p =.039)). Sorbent‐assisted peritoneal dialysis treatment in a uremic pig model is safe and enhances small solute clearance as compared to a static dwell. Future studies in humans or animal species with higher peritoneal transport should elucidate whether our SAPD system enhances clearance to a clinically relevant extent as compared to conventional PD. [ABSTRACT FROM AUTHOR]

Background: Autosomal dominant polycystic kidney disease (ADPKD) and neurofibromatosis type 1 (NF1) are both autosomal dominant disorders with a high rate of novel mutations. However, the two disorders have distinct and well‐delineated genetic, biochemical, and clinical findings. Only a few cases of coexistence of ADPKD and NF1 in a single individual have been reported, but the possible implications of this association are unknown. Methods: We report an ADPKD male belonging to a family of several affected members in three generations associated with NF1 and optic pathway gliomas. The clinical diagnosis of ADPKD and NF1 was performed by several image techniques. Results: Linkage analysis of ADPKD family was consistent to the PKD2 locus by a nonsense mutation, yielding a truncated polycystin‐2 by means of next‐generation sequencing. The diagnosis of NF1 was confirmed by mutational analysis of this gene showing a 4‐bp deletion, resulting in a truncated neurofibromin, as well. The impact of this association was investigated by analyzing putative genetic interactions and by comparing the evolution of renal size and function in the proband with his older brother with ADPKD without NF1 and with ADPKD cohorts. Conclusion: Despite the presence of both conditions there was not additive effect of NF1 and PKD2 in terms of the severity of tumor development and/or ADPKD progression. [ABSTRACT FROM AUTHOR]

Autosomal dominant polycystic kidney disease (ADPKD) is a heterogeneous inherited disease characterized by renal and extrarenal manifestations with progressive fluid‐filled cyst development leading to end‐stage renal disease. The rate of disease progression in ADPKD exhibits high inter‐ and intrafamilial variability suggesting involvement of modifier genes and/or environmental factors. Renal hypouricemia (RHUC) is an inherited disorder characterized by impaired tubular uric acid transport with severe complications, such as acute kidney injury and chronic kidney disease (CKD). However, the two disorders have distinct and well‐delineated genetic, biochemical, and clinical findings. Only a few cases of coexistence of ADPKD and RHUC (type 1) in a single individual have been reported. We report a family with two members: an ADPKD 24‐year‐old female which presented bilateral renal cysts in utero and hypouricemia since age 5, and her mother with isolated hypouricemia. Next‐generation sequencing identified two mutations in two genes PKD1 and SLC2A9 in this patient and one isolated SLC2A9 mutation in her mother, showing RHUC type 2, associated to CKD. The coexistence of these two disorders provides evidence of SLC2A9 variant could act as a modifier change, with synergistic actions, that could promote cystogenesis and rapid ADPKD progression. This is the first case of coexistence of PKD1 and SLC2A9 mutations treated with tolvaptan. [ABSTRACT FROM AUTHOR]

Several cases of patients with anaphylactic or systemic hypersensitivity reactions to polysulfone (PS) hemodialysis (HD) membranes and tolerance to cellulose triacetate (CTA) membranes have recently been reported. To investigate the mechanisms involved in PS hypersensitivity, basophil, T cell, and complement activation were analyzed in acute-phase samples from two patients with systemic reactions to PS-based membranes. Basophil and T cell activation, as well as higher serum tryptase levels were detected in acute-phase samples compared with basal levels. Complement levels (C3 and C4) were decreased in acute-phase samples from PS-allergic patients to a higher extent than in samples from control donors taken at the same time points, indicating complement activation during the acute reactions. An experimental external circuit was established on pediatric membranes after rinsing with low or high priming volumes of saline solution, to analyze basophils, T cells, and complement activation in blood samples from 10 PS-allergic and 8 nonallergic HD patients upon contact with PS-based or CTA membranes. Predialysis and postdialysis samples were collected. Basophils from PS-allergic patients exhibited increased degranulation, and T cells showed significantly increased activation after contact with PS-based membranes primed with low volumes of saline. No activation was detected in leukocytes from nonallergic patients under the same experimental conditions. Membrane priming with high volumes of saline abrogated activation of basophils and T cells. However, basophils from allergic donors showed significantly higher responses to Fcεc stimulation after contact with PS membranes. Basophil degranulation and elevated serum tryptase levels in allergic patients during acute reactions support the systemic activation of mast cells and basophils during hypersensitivity reactions to PS-based membranes. A leachable component of the membranes might be responsible for cell activation in some patients. [ABSTRACT FROM AUTHOR]

Tavira B, Coto E, Díaz-Corte C, Ortega F, Arias M, Torres A, Díaz JM, Selgas R, López-Larrea C, Campistol JM, Ruiz-Ortega M, Alvarez V, The Pharmacogenetics of Tacrolimus REDINREN Study Group. KCNQ1 gene variants and risk of new-onset diabetes in tacrolimus-treated renal-transplanted patients. Clin Transplant 2011: 25: E284-E291. © 2011 John Wiley & Sons A/S. Recent genome-wide association studies identified single-nucleotide polymorphisms (SNPs) in the gene encoding the pore-forming subunit of the voltage-gated K+ channel ( KCNQ1) as a risk factor for type 2 diabetes. Tacrolimus (Tac) increased the risk of new-onset diabetes after transplantation (NODAT). The aim of this study was to analyze the association between KCNQ1 variants and the risk for NODAT in kidney-transplanted patients who received Tac as primary immunosuppressor. We genotyped three common KCNQ1 SNPs in 145 Spanish patients who received a cadaveric kidney graft and developed NODAT in the first-year post-transplant (the NODAT group), and 260 patients who remained non-diabetics (non-NODAT). In addition, we searched for DNA variants in the whole KCNQ1 coding exons in these patients. SNP rs2237895 (genotype CC) was associated with an increased risk for NODAT in our population (p = 0.008; OR = 1.83, 95% CI = 1.14-2.93), independently of other risk factors as body mass index, recipient age, or tacrolimus dosage. Other KCNQ1 variants were not associated with NODAT in our patients. Our work supported a role for KCNQ1 gene variants as determinants of the risk of developing NODAT among Tac-treated patients. [ABSTRACT FROM AUTHOR]

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. Objective Our aim has been to quantify serum concentrations of total ghrelin in a group of patients with CRF on chronic therapy with both haemodialysis (HD) and peritoneal dialysis (PD) in comparison with a group of patients on conservative management (predialysis). Patients and measurements We studied 68 CRF patients treated by HD ( n = 30, 16 men, age 61·2 ± 1·8 years) and PD groups ( n = 38, 21 men, age 54·4 ± 1·7 years). A group of 19 uraemic patients on conservative management served as the control. Serum concentrations of ghrelin, leptin, insulin, IGF I and GH were measured in all subjects. Results Patients undergoing HD showed similar concentrations of ghrelin in comparison with the control group (9491 ± 787 vs 9280 ± 918 pg/ml, NS). However, PD patients exhibited baseline ghrelin concentrations significantly lower than those found in patients on conservative management (3230 ± 216 pg/ml, P < 0·0001). Men and women showed similar serum ghrelin levels in both HD (9845·9 ± 1071 vs 9085 ± 1194 pg/ml) and PD patients (3214 ± 297 vs 3250 ± 324 pg/ml). Hypertension and diabetes mellitus did not influence ghrelin levels. Serum GH levels were positively correlated with serum ghrelin concentrations in both HD ( r = 0·46, P < 0·05) and PD ( r = 0·53, P < 0·001) patients; however, no relationships between ghrelin, leptin, insulin and IGF I were found. Conclusions These results suggest that PD is accompanied by a striking decrement in baseline ghrelin concentrations in comparison with values found both in HD and control patients. Further studies are necessary to determine mechanisms involved in ghrelin regulation in uraemic patients. [ABSTRACT FROM AUTHOR]

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.We studied 82 dialysis patients treated by PD (n = 44, 23 males and 21 females, mean age 54·4 ± 1·8 years) or HD (n = 38, 22 males and 16 females, age 60·8 ± 1·6 years). A group of 19 uraemic patients on conservative management served as the control. Serum concentrations of leptin, adiponectin and resistin were measured in all subjects. Information on vascular disease (cerebral vascular, peripheral vascular and heart disease) was obtained from a detailed medical history.PD patients showed significantly higher serum leptin concentrations[median (interquartile range), 28·7 (13·0–71·9) µg/l] than those found in patients on HD[9·7 (4·7–31·9) µg/l,P < 0·01] or in conservative management[5·9 (4·3–38·6) µg/l,P < 0·05]. Adiponectin concentrations were similar in the three groups of patients (mean ± SEM, 48·0 ± 4·5 mg/l in PD, 57·7 ± 4·4 mg/l in HD, and 44·4 ± 7·0 mg/l in controls, NS). Patients treated by both PD and HD exhibited resistin concentrations significantly higher than those found in controls (26·3 ± 0·99 and 27·5 ± 1·4 µg/l, respectively,vs.17·3 ± 1·0 µg/l,P < 0·001). Leptin concentrations were positively correlated with body mass index (BMI) (r = 0·287,P < 0·01) and adiponectin levels were negatively related to BMI (r = −0·416,P <0·001) and the homeostatic model assessment (HOMA-R) index (r =−0·216,P < 0·05). Leptin, adiponectin and resistin levels in patients with previous vascular events were similar to those found in patients without these complications. Logistic regression analysis did not demonstrate any relationship between serum adipocytokine concentrations and the presence of vascular disease of any type. A significant relationship between resistin and heart disease[odds ratio (OR) 1·80 (1·03–3·15),P = 0·039] was found when analysing subgroups of patients.These data suggest that leptin levels are higher in PD patients, and resistin levels are higher in PD and HD patients in relation to patients on conservative management, whereas adiponectin concentrations are similar in the three groups. These results do not support the presence of a clinically relevant relationship between adipocytokines and previous episodes of vascular disease in the whole population or in patients classified in subgroups, with the only exception of a relationship between resistin levels and heart disease. [ABSTRACT FROM AUTHOR]

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). A cross-sectional study in the setting of a dialysis unit of a general hospital. We studied 108 dialysis patients treated by PD ( n = 54, 32 males and 22 females, mean age 61·0 ± 1·4 years) or HD ( n = 54, 31 males and 23 females, age 62·6 ± 1·5 years). A group of 42 healthy subjects of similar age, sex and body mass index (BMI) served as the control group. Baseline serum concentrations of GH, insulin, IGF-I, IGFBP-1 and IGFBP-3 were measured in all patients and control subjects. Fasting serum concentrations of IGF-I and its binding proteins (IGFBP-1 and IGFBP-3) were significantly higher in dialysis patients than in subjects with normal renal function. IGF-I (248·9 ± 23·4 vs. 205·5 ± 15·5 µg/l, NS), IGFBP-3 (5·6 ± 0·4 vs. 5·5 ± 0·2 mg/l, NS) and IGFBP-1 (36·1 ± 5·9 vs. 44·1 ± 6·5 µg/l, NS) concentrations were similar in both groups of dialysis (PD vs. HD) patients. However, GH (2·3 ± 0·3 vs. 1·1 ± 0·1 µg/l, P < 0·001) and insulin (40·4 ± 4·5 vs. 30·1 ± 3·1 µU/ml, P < 0·05) levels were significantly higher in the PD group than in the HD group. Both groups of dialysis patients showed significantly higher levels of insulin than healthy subjects (14·7 ± 1·9 µU/ml, P < 0·0001 and P < 0·01 for PD and HD, respectively). In both groups of dialysis patients, IGF-I correlated inversely with IGFBP-1 (PD group r = −0·46, P = 0·0006; HD group r = −0·57, P = 0·0001) and directly with IGFBP-3 (PD group r = 0·44, P = 0·001; HD group r = 0·73, P = 0·001). No correlation between insulin and IGFBP-1 was found in any of the groups studied. These findings demonstrate that adult dialysis patients have elevated IGF-I, IGFBP-1 and IGFBP-3 serum concentrations compared with subjects with normal renal function. Only GH and insulin show statistically significant differences in relation to type of dialysis. Finally, the negative correlation between IGF-I and IGFBP-1 and the positive correlation between IGF-I and IGFBP-3 are maintained in both groups of adult dialysis patients. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Congenital nephrogenic diabetes insipidus (NDI) is a rare condition characterized by severe polyuria, due to the inability of the kidneys to concentrate urine in response to arginine vasopressin (AVP). In the majority of the cases, the disease shows an X‐linked inherited pattern, although an autosomal recessive inheritance was also observed. Methods: We report a patient with a severe NDI diagnosed during the neonatal period. Because the patient was female without a family history of congenital NDI, her disease was thought to exhibit an autosomal recessive form. Results: A full mutation analysis of AVP receptor 2 (AVPR2; MIM#300538) gene showed no mutations. However, direct Sanger sequencing of the aquaporin 2 (AQP2) revealed an apparently homozygous mutation at nucleotide position NM_000486.5:c.374C>T (p.Thr125Met) in exon 2. Further customized multiplex ligation‐dependent probe amplification (MLPA), single‐nucleotide polymorphism (SNP) array analysis, and long‐range polymerase chain reaction (PCR) followed by Sanger sequencing showed a heterozygous exonic deletion comprising exons 2, 3, and partially 4 of AQP2. Conclusion: This is the first case of a compound heterozygote patient with a missense mutation involving NM_000486.5:exon2:c.374C>T (p.Thr125Met) and a gross deletion of at least exons 2, 3, and partially 4 on the AQP2 to present with a severe NDI phenotype. [ABSTRACT FROM AUTHOR]