Dysregulation of myelin synthesis and actomyosin function underlies aberrant myelin in CMT4B1 neuropathy.

Charcot-Marie-Tooth type 4B1 (CMT4B1) is a severe autosomal recessive demyelinating neuropathy with childhood onset, caused by loss-of-function mutations in the myotubularin-related 2 (MTMR2) gene. MTMR2 is a ubiquitously expressed catalytically active 3-phosphatase, which in vitro dephosphorylates the 3-phosphoinositides PtdIns3P and PtdIns(3,5)P2, with a preference for PtdIns(3,5)P2 A hallmark of CMT4B1 neuropathy are redundant loops of myelin in the nerve termed myelin outfoldings, which can be considered the consequence of altered growth of myelinated fibers during postnatal development. How MTMR2 loss and the resulting imbalance of 3'-phosphoinositides cause CMT4B1 is unknown. Here we show that MTMR2 by regulating PtdIns(3,5)P2 levels coordinates mTORC1-dependent myelin synthesis and RhoA/myosin II-dependent cytoskeletal dynamics to promote myelin membrane expansion and longitudinal myelin growth. Consistent with this, pharmacological inhibition of PtdIns(3,5)P2 synthesis or mTORC1/RhoA signaling ameliorates CMT4B1 phenotypes. Our data reveal a crucial role for MTMR2-regulated lipid turnover to titrate mTORC1 and RhoA signaling thereby controlling myelin growth.

Mutations in MYO9B are associated with Charcot-Marie-Tooth disease type 2 neuropathies and isolated optic atrophy.

BACKGROUND AND PURPOSE: Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of disorders caused by mutations in at least 100 genes. However, approximately 60% of cases with axonal neuropathies (CMT2) still remain without a genetic diagnosis. We aimed at identifying novel disease genes responsible for CMT2. METHODS: We performed whole exome sequencing and targeted next generation sequencing panel analyses on a cohort of CMT2 families with evidence for autosomal recessive inheritance. We also performed functional studies to explore the pathogenetic role of selected variants. RESULTS: We identified rare, recessive variants in the MYO9B (myosin IX) gene in two families with CMT2. MYO9B has not yet been associated with a human disease. MYO9B is an unconventional single-headed processive myosin motor protein with signaling properties, and, consistent with this, our results indicate that a variant occurring in the MYO9B motor domain impairs protein expression level and motor activity. Interestingly, a Myo9b-null mouse has degenerating axons in sciatic nerves and optic nerves, indicating that MYO9B plays an essential role in both peripheral nervous system and central nervous system axons, respectively. The degeneration observed in the optic nerve prompted us to screen for MYO9B mutations in a cohort of patients with optic atrophy (OA). Consistent with this, we found compound heterozygous variants in one case with isolated OA. CONCLUSIONS: Novel or very rare variants in MYO9B are associated with CMT2 and isolated OA.

SIL1 deficiency causes degenerative changes of peripheral nerves and neuromuscular junctions in fish, mice and human.

BACKGROUND: Marinesco-Sjögren Syndrome (MSS) is a rare neuromuscular condition caused by recessive mutations in the SIL1 gene resulting in the absence of functional SIL1 protein, a co-chaperone for the major ER chaperone, BiP. As BiP is decisive for proper protein processing, loss of SIL1 results in the accumulation of misshaped proteins. This accumulation likely damages and destroys cells in vulnerable tissues, leading to congenital cataracts, cerebellar ataxia, vacuolar myopathy and other MSS phenotypes. Whether the peripheral nervous system (PNS) is affected in MSS has not been conclusively shown. METHODS: To study PNS vulnerability in MSS, intramuscular nerves fibres from MSS patients and from SIL1-deficient mice (woozy) as well as sciatic nerves and neuromuscular junctions (NMJ) from these mice have been investigated via transmission electron microscopic and immunofluorescence studies accompanied by transcript studies and unbiased proteomic profiling. In addition, PNS and NMJ integrity were analyzed via immunofluorescence studies in an MSS-zebrafish model which has been generated for that purpose. RESULTS: Electron microscopy revealed morphological changes indicative of impaired autophagy and mitochondrial maintenance in distal axons and in Schwann cells. Moreover, changes of the morphology of NMJs as well as of transcripts encoding proteins important for NMJ function were detected in woozy mice. These findings were in line with a grossly abnormal structure of NMJs in SIL1-deficient zebrafish embryos. Proteome profiling of sciatic nerve specimens from woozy mice revealed altered levels of proteins implicated in neuronal maintenance suggesting the activation of compensatory mechanisms. CONCLUSION: Taken together, our combined data expand the spectrum of tissues affected by SIL1-loss and suggest that impaired neuromuscular transmission might be part of MSS pathophysiology.

Neuromuscular Junction Changes in a Mouse Model of Charcot-Marie-Tooth Disease Type 4C.

The neuromuscular junction (NMJ) appears to be a site of pathology in a number of peripheral nerve diseases. Charcot-Marie-Tooth (CMT) 4C is an autosomal recessive, early onset, demyelinating neuropathy. Numerous mutations in the SH3TC2 gene have been shown to underlie the condition often associated with scoliosis, foot deformities, and reduced nerve conduction velocities. Mice with exon 1 of the Sh3tc2 gene knocked out demonstrate many of the features seen in patients. To determine if NMJ pathology is contributory to the pathomechanisms of CMT4C we examined NMJs in the gastrocnemius muscle of SH3TC2-deficient mice. In addition, we performed proteomic assessment of the sciatic nerve to identify protein factors contributing to the NMJ alterations and the survival of demyelinated axons. Morphological and gene expression analysis of NMJs revealed a lack of continuity between the pre- and post-synaptic apparatus, increases in post-synaptic fragmentation and dispersal, and an increase in expression of the gamma subunit of the acetylcholine receptor. There were no changes in axonal width or the number of axonal inputs to the NMJ. Proteome investigations of the sciatic nerve revealed altered expression of extracellular matrix proteins important for NMJ integrity. Together these observations suggest that CMT4C pathology includes a compromised NMJ even in the absence of changes to the innervating axon.

Basilic vein transposition versus biosynthetic prosthesis as vascular access for hemodialysis.

BACKGROUND: Vascular access (VA) complications account for a significant number of hospital admissions in dialysis and have substantial costs. A native arteriovenous fistula (AVF) cannot be successfully obtained in all patients. At our center, we established an autogenous brachial-basilic AVF (BBAVF) in the upper arm in patients with a failed forearm fistula or with superficial vessels that were unsuitable for preparing a good site for VA. In most of these patients, we resort to prosthetic materials for creating a functioning VA as the last strategy. The present study compared the outcomes of BBAVF and AV graft (AVG) in patients undergoing long-term hemodialysis in whom there was no other possibility of creating a VA. METHODS: We analyzed 57 complex patients, 27 randomized to receive AVG and 30 randomized to BBAVF, between 2002 and 2008. The Omniflow II Vascular Prosthesis (Bio Nova International Pty Ltd, North Melbourne, VIC, Australia), the latest-generation collagen-polyester composite, was used to create the prosthetic VA. Primary patency (PP) and secondary patency (SP) rates were calculated using the Kaplan-Meier test. The log-rank test was used to compare PP and SP rates of the single VA. RESULTS: Length of hospital admission time, total intervention time, and mean interval to the first venipuncture for dialysis were longer for BBAVF. In the early postoperative period, patients who received BBAVF had a complication rate similar to those who received AVG; however, patients who received AVG showed a higher rate of long-term adverse events. PP and SP rates were higher for BBAVF than for AVG, although this was not statistically significant for SP. CONCLUSIONS: Our results show that BBAVF should be the first choice in patients with a good life expectancy and who can rely on an available temporary VA. However, given the shorter time to use, AVG could be an alternative in patients with compromised clinical conditions and in whom a temporary VA is not reliable, considering that the long-term outcome may be considered beneficial regardless.

The first human renal transplant and the first xenotransplant in Italy.

The authors describe the first human renal transplantation and the first renal xenotransplant in Italy and the atmosphere at the University of Rome where these transplants were performed. Just a few months after those events, a state law was approved which allowed kidney donation.

A case report of plasma exchange therapy in non-paraneoplastic cerebellar ataxia associated with anti-Yo antibody.

A 71-year-old-woman was admitted to the S. Eugenio Hospital for a history of progressively impaired standing and gait. Anamnesis revealed systemic hypertension, gastric polyposis and juvenile pulmonary tuberculosis. Neurological examination showed a severe truncal and gait ataxia, without any sensory-motor impairment. Motor and somato-sensory evoked potentials were normal. Brain Magnetic Resonance Imaging (MRI) showed minimal signs of chronic ischemia only at a supratentorial level. Cerebral Single Photon Emission Computed Tomography, spinal MRI, total body computed tomography, Esophagogastroduodenoscopy, and finally total body Positron Emission Tomography resulted negative for neoplasms. Oncological serum markers were negative. Serum antibody against Purkinje's cells (Anti-Yo) was detected and titer was 1:80, while normally it should be undetectable. Other autoantibodies (Anti-Hu, Anti-Ri) were undetectable. Two sessions of plasma exchange (PE) were thus performed, leading to a rapid, marked and durable improvement of standing and gait and to a reduction of the autoantibody, which became undetectable. No serious adverse effect was noted. Although no definite therapy for autoimmune cerebellar ataxia has been established, PE should be considered as one of the main therapeutic choices.

Adequate protein dietary restriction in diabetic and nondiabetic patients with chronic renal failure.

OBJECTIVE: To evaluate whether a dietary protein restriction is useful for slowing the progression of chronic renal failure (CRF) in diabetic and nondiabetic patients and to analyze the possible risk of malnutrition after such a dietary regimen. DESIGN: Prospective, randomized case-control clinical trial. SETTING: Nephrology outpatients. PATIENTS AND OTHER PARTICIPANTS: A total of 169 patients, 89 affected with CRF and chronic hypertension and 80 affected with overt diabetic nephropathy (24 suffering from type 1 and 56 from type 2 diabetes) and chronic hypertension. INTERVENTION: Diabetic patients and nondiabetic patients were randomly divided into 2 groups: 40 diabetic patients received a low-protein diet (0.8 g/kg/day) and 40 were maintained on a free protein diet; similarly, 44 nondiabetic patients received a low-protein diet (0.6 g/kg/day) and 45 were maintained on a free protein diet. The investigation lasted 1 year. MAIN OUTCOME MEASURE: Renal function and nutritional status. RESULTS: At the end of the study, there were no statistically significant differences in renal function between treated and nontreated diabetic patients, whereas treated nondiabetic patients showed a lower decrease in renal function compared with the nontreated group. In both diabetic and nondiabetic patients, the mean body weight and obesity index decreased significantly in treated patients compared with nontreated ones. Serum albumin and prealbumin were stable in all patients during the whole study time, and there were no other signs of malnutrition. CONCLUSION: An adequate dietary protein restriction is accepted by patients, and it is well tolerated during a 12-month follow-up. Without any sign of malnutrition, it is possible to get near the ideal body weight and to reduce the obesity index and the body mass index, which are both well-established risk factors for developing cardiovascular pathology. In nondiabetic patients only, we observed a significant slowing of the progression of renal damage.

Clinical management of nondialysis patients with chronic kidney disease: a retrospective observational study. Data from the SONDA study (Survey Of Non-Dialysis outpAtients).

BACKGROUND: A lack of awareness of chronic kidney disease (CKD) often results in delayed diagnosis and inadequate treatment. PURPOSE: The objective of this study was to assess the therapeutic management and outcome of nondialysis CKD patients. METHODS: Three hundred ninety-seven patients (54.9% males aged 67.5 ± 14.6 years) were retrospectively screened at the Nephrology Department, GB Grassi Hospital, Rome, Italy. After a baseline visit, patient data were collected every 6 months for a total of 24 months. Clinical characteristics were measured at baseline, then the following outcomes were measured every 6 months: staging of CKD, presence of concomitant diseases, treatment and adherence to Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines for anemia management. RESULTS: Three hundred sixty-eight (92.7%) patients attended at least one visit and 92 (23.2%) patients attended all four visits. Patients were mainly referred to a nephrologist for chronic renal failure (61.7%) or hypertension (42.8%). At baseline, 79.6% of patients had previous hospitalization and 79.1% were receiving antihypertensive medication. Serum creatinine and/or glomerular filtration rate was examined in >90% of patients, whereas parathyroid hormone was rarely examined (5.5%). Vitamin D supplementation was received by 6.5% of patients. The majority of patients were staged at 3 or 4 CKD (32% and 23.9%, respectively) and did not significantly change over time. The use of antithrombotic, antilipidemic and erythropoietin medication increased over the four surveys. The majority of patients (86.8%) achieved hemoglobin K/DOQI target levels. CONCLUSION: These findings demonstrate a current lack of attention of CKD and related disorders (mineral metabolism, electrolyte balance, and anemia) at the level of the general practitioner (GP) and non-nephrology specialist, which can result in both delayed referral and inadequate treatment. By increasing both awareness of CKD and the coordinated relationship between GPs and nephrologists, patient clinical and therapeutic outcome may be improved.

Hemorragia retroperitoneal espontánea Reporte de caso y revisión de la literatura / SPONTANEOUS RETROPERITONEAL HEMORRHAGE: A CASE REPORT AND AN OVERVIEW OF THE LITERATURE

Reportamos el caso de un hombre de 74 años de edad padeciendo una enfermedad renal terminal, actualmente en terapia de reemplazo crónica, tomando warfarina en dosis regulares, quien presentó síntomas de debilidad y dolor agudo en el flanco derecho durante una sesión de diálisis. Fue enviado al Departamento de Emergencias donde una tomografía computada abdominal con administración intravenosa de contraste reveló la presencia de un amplio hematoma que se desarrollaba en el riñón derecho, con extensión continua al tejido graso perirrenal, fascia de Gerota y al espacio pararrenal posterior. Brindándosele monitoreo hemodinámico y estabilidad imagenológica seriada, el paciente se sometió a tratamiento conservador con reposo en cama, administración de antibióticos y terapia de reemplazo de sangre. La warfarina se interrumpió inmediatamente. No fue requerido ningún procedimiento quirúrgico. Posteriormente a la consulta con hematólogos, se sugirió el reemplazo a largo término de la warfarina por heparina cálcica. La hemorragia retroperitoneal espontánea, de origen ya sea renal o de otras estructuras sangrantes, es un evento relativamente raro, aunque potencial amenaza para la vida. Puede deberse a varias condiciones subyacentes. Entre ellas, el paciente que estamos reportando estaba padeciendo una enfermedad renal quística adquirida y estaba tanto en diálisis a largo plazo como en terapia anticoagulante oral. En el caso de hemorragia renal con condiciones hemodinámicas estables y sin otros elementos sospechosos, el tratamiento conservador debe ser tomado en consideración.

We report the case of a 74-year-old man afflicted with end-stage renal disease, currently in chronic repla wea cement therapy, taking warfarin on a regular basis, who presented feelings of kness and acute right flank pain during a dialysis session. He was sent to the Emergency Department where an abdominal computed tomography with intravenous contrast administration revealed the presence of a wide hematoma developing in the right kidney, with continuous extension to perirenal fat tissue, Gerota's fascia and posterior pararenal space. Given hemodynamic monitoring and serial imaging stability, the patient underwent conservative management with bed rest, antibiotic administration and blood replacement therapy. Warfarin was immediately interrupted. No operative treatment was required. After a consultation with hematologists, long term replace ment of warfarin by heparin calcium was suggested. Spontaneous retroperitoneal hemorrhage , related to either renal or other structures bleeding , is a relatively rare event, though potentially life-threatening . It can be due to several undelying conditions. Among them, the patient we are reporting about was afflicted with acquired cystic kidney disease and he was on both long-term dialysis and oral anticoagulant therapy. In the case of renal hemorrhage with stable hemodynamic conditions and no further suspicious elements, conservative management should be considered.

Cardiac troponin I (2nd generation assay) in chronic haemodialysis patients: prevalence and prognostic value.

BACKGROUND: Elevated serum cardiac troponin T (cTnT) levels are frequently observed in chronic dialysis patients and have been shown to be associated with increased morbidity and mortality. The aim of this study was to determine whether cardiac troponin I (cTnI), which is less frequently elevated, has similar clinical significance. METHODS: We studied 101 asymptomatic patients with no clinical evidence of coronary artery disease who were undergoing chronic dialytic treatment. We measured their serum cTnI levels immediately before the start of their dialysis sessions by a second-generation assay (OPUS-DADE). Our study included a year-long follow-up with trimestrial cTnI assays as well as clinical, X-ray and echocardiographic surveillance. We considered patients with serum cTnI > or =0.15 ng/ml as positive and those with levels <0.15 ng/ml as negative. RESULTS: Among the 14 patients with high serum cTnI levels, nine (64%) suffered acute cardiac events during the 12-month follow-up. In contrast, among the 72 patients with low cTnI levels only seven (9.7%) had acute events. In another group of 15 patients with variable cTnI levels, three patients (20%) had cardiac events. CONCLUSION: Based on these results, serum cTnI appears to be a valuable predictive marker of cardiovascular events in asymptomatic dialysis patients. For those patients who might benefit from thorough cardiac investigation and treatment, information on cTnI could be useful in preventing cardiac events.

One year of clinical experience in postdilution hemofiltration with online reinfusion of regenerated ultrafiltrate.

BACKGROUND/AIMS: Hemofiltrate reinfusion (HFR) is characterized by the use of regenerated ultrafiltrate as replacement fluid. We set up a new technique, postdilution HFR (PD-HFR), aiming at increasing purification efficiency, treatment tolerance and at reducing inflammatory states. METHODS: We performed PD-HFR in 6 uremic patients during 1 year. Dialysis efficacy, dialyzer blood loss and the behavior of cytokines were evaluated. RESULTS: No pyrogenic reactions or other adverse events were recorded. Treatment tolerance was excellent. We observed high urea extraction rates and optimal Kt/V values, high beta2-microglobulin (beta2m) extraction rates and a decrease in dialyzer blood loss; also IL-6 and TNF-alpha decreased significantly. CONCLUSIONS: Inversion of the standard HFR configuration has allowed us to improve the removal of both urea and beta2m, and to decrease dialyzer blood loss, with an optimal tolerance. Moreover, the decrease in cytokine levels might attenuate the uremic microinflammatory state.