Cardiovascular Mapping in Cirrhosis From the Compensated Stage to Hepatorenal Syndrome: A Magnetic Resonance Study.

INTRODUCTION: Arterial vasodilation and hyperdynamic circulation are considered hallmarks of the pathophysiological mechanisms of decompensation in cirrhosis. However, detailed characterization of peripheral, splanchnic, renal, and cardiac hemodynamic have not previously been published in a spectrum from healthy stage to advanced decompensated liver disease with hepatorenal syndrome-acute kidney injury (HRS-AKI). METHODS: We included 87 patients with cirrhosis and 27 healthy controls in this prospective cohort study. The population comprised patients with compensated cirrhosis (n = 27) and decompensated cirrhosis (n = 60); patients with decompensated cirrhosis were further separated into subsets of responsive ascites (33), refractory ascites (n = 16), and HRS-AKI (n = 11). We measured portal pressure and assessed regional blood flow by magnetic resonance imaging. RESULTS: Patients with compensated cirrhosis experienced higher azygos venous flow and higher hepatic artery flow fraction of cardiac index than controls ( P < 0.01), but other flow parameters were not significantly different. Patients with decompensated cirrhosis experienced significantly higher cardiac index ( P < 0.01), higher superior mesenteric artery flow ( P = 0.01), and lower systemic vascular resistance ( P < 0.001) compared with patients with compensated cirrhosis. Patients with HRS-AKI had the highest cardiac output and lowest renal flow of all groups ( P < 0.01 and P = 0.02, respectively). Associations of single hemodynamic parameters were stronger with model for end-stage liver disease than with portal pressure. DISCUSSION: The regional cardiocirculatory changes seem closely linked to clinical symptoms with 3 distinguished hemodynamic stages from compensated to decompensated cirrhosis and, finally, to HRS-AKI. The attenuated renal perfusion despite high cardiac output in patients with HRS-AKI challenges the prevailing pathophysiological hypothesis of cardiac dysfunction as a causal factor in HRS-AKI. Finally, magnetic resonance imaging seems an accurate and reliable noninvasive method to assess hemodynamics and has potential as a diagnostic tool in patients with cirrhosis.

Basophil sensitivity reflects long-term clinical outcome of subcutaneous immunotherapy in grass pollen-allergic patients.

BACKGROUND: Allergic rhinoconjunctivitis is a public health problem. Allergen Immunotherapy is an effective and safe treatment, that modifies the natural course of allergic disease and induces long-term tolerance. OBJECTIVE: To correlate basophil and antibody biomarkers of subcutaneous immunotherapy to clinical outcomes and cellular changes in target tissue. METHODS: Adults suffering from allergic rhinoconjunctivitis due to grass pollen allergy were randomized to receive subcutaneous immunotherapy (n = 18) or to an open control group (n = 6). Patients reported daily symptom and medication scores and weekly rhinitis related quality of life scores during four pollen seasons. Biomarkers were measured every 3 months for three years treatment and every 6 months in the follow-up year. Nasal and cutaneous allergen challenge tests were performed annually. Leukocyte subsets were assessed in nasal mucosa biopsies at baseline and after treatment. RESULTS: Subcutaneous immunotherapy led to a 447-fold decrease in basophil sensitivity during the first treatment year. This remained 100-fold lower than baseline during the 3 year-treatment period and 10-fold lower during the follow-up year (n = 18, P = .03). Decrease in basophil sensitivity after three weeks of treatment predicted long-term improvement in seasonal combined symptom and medication scores (á¿¥=-0.69, P = .0027) during three years of treatment. AUC of IgE-blocking factor correlated to nasal allergen challenge (á¿¥ = 0.63, P = .0012) and SPT (á¿¥ = 0.45, P = .03). Plasma cell numbers in the nasal mucosa increased during treatment (P = .02). CONCLUSION: Decrease in basophil sensitivity after three weeks of subcutaneous allergen immunotherapy predicted the clinical outcome of this treatment.

Synthetic retinoid AM80 inhibits IL-17 production of gamma delta T cells and ameliorates biliary atresia in mice.

BACKGROUND & AIMS: Recent evidence suggests that Interleukin (IL)-17-producing gamma delta ( γδ ) T cells are the dominant pathogenic cellular component in designated autoimmune or inflammatory diseases, including biliary atresia (BA). We have previously demonstrated that retinoids effectively suppress T-helper cell (Th) 17 differentiation. METHODS: Here, we established an in vitro system, enabling investigations of the effect of AM80 on the IL-17 production of γδ T cells. Additionally, we tested the therapeutic effect of AM80 in the Rotavirus-induced mouse model of BA. Co-incubation of γδ T cells with IL-23 and anti-CD28 mAb proved most effective in inducing an IL-17 response in vitro. The effect of AM80 on human CCR6+CD26+ V δ 2 cells was assessed by flow cytometry. RESULTS: AM80 efficiently reduced IL-17 production by murine γδ T cells and the expression of the master transcription factor Retinoid-Orphan-Receptor- γ t (ROR γτ ) in a dose-dependent manner. The fraction of human CCR6+CD26+ V δ 2 cells was significantly reduced by co-incubation with AM80. Moreover, AM80 also inhibited IL-17 production by liver-infiltrating γδ T cells isolated from animals suffering from BA. Intraperitoneal treatment with AM80 ameliorated BA-associated inflammation. However, AM80 treatment was not sufficient to control disease progression in the murine model, despite reduced inflammatory activity in the animals. CONCLUSIONS: Retinoids are very efficient in down-regulating IL-17 production by γδ T cells in vitro and, to a lesser extent, in the BA mouse model. However, retinoids do not suffice for the control of disease progression. Thus, our data suggest that IL-17 is not the only factor contributing to the pathogenesis of BA. LAY SUMMARY: Biliary atresia (BA) is a rare disease which affects infants, causing progressive liver failure in most children, and is the most common indication for paediatric liver transplantation. We have previously demonstrated that IL-17, produced by γδ T cells, contributes to hepatic inflammation in the murine model of BA and is increased in the livers of infants suffering from the disease. In the study at hand, we demonstrate that treatment with AM80, a synthetic retinoid with superior pharmacological properties, effectively inhibits the IL-17 production of gamma delta T cells without generating systemic immunosuppression. Although all-trans retinoic acid (ATRA) has been demonstrated to suppress differentiation of IL-17-producing conventional T-helper cells (Th17) in vitro, the therapeutic application of ATRA in vivo is limited by the compound's potential side effects caused by its instability and lack of receptor specificity. Our study is the first to show that AM80 suppresses the IL-17 production of γδ T cells in a very efficient manner and that hepatic inflammation is ameliorated in mice suffering from BA. However, AM80 treatment does not suffice to block the disease progression. We conclude that factors other than IL-17 drive the progressive inflammation in BA. The addition of retinoids to the treatment regime of children suffering from BA might decrease the disease burden; however, further research is needed to clarify the pathomechanism and possible therapeutic interventions in humans.

Hepatocyte growth factor levels in livers and serum at Kasai-portoenterostomy are not predictive of clinical outcome in infants with biliary atresia.

Biliary atresia (BA) is characterized by progressive destruction of the biliary system leading to liver fibrosis and deterioration of liver function. Serum hepatocyte growth factor (HGF) has been shown to be increased in cirrhotic diseases including BA. The aim of this study was to investigate the prognostic value of HGF levels in sera and liver tissue for the further disease course. A total of 49 serum and liver samples from infants with BA were acquired during Kasai-portoenterostomy (KPE) and analyzed by multiplex immunoassay including HGF, as marker of liver regeneration, and Interleukin 6 (IL-6) as a marker of inflammation. Both mediators showed no correlation with the outcome defined as favorable (survival with native liver (SNL)) or, in contrast, rapid deterioration of liver function requiring transplantation. Our data suggest that the degree of liver regeneration indicated by high levels of HGF within the liver is a dismissible factor in the post-KPE disease course.

Cardiac dysfunction in cirrhosis: a 2-yr longitudinal follow-up study using advanced cardiac imaging.

The temporal relationship between cirrhotic cardiomyopathy, progression of liver disease, and survival remains unknown. Our aim was to investigate the development of structural and functional cardiac changes over time with the progression of cirrhosis and outcome. Sixty-three cirrhotic outpatients (Child class: A = 9, B = 46, C = 8) and 14 healthy controls were included in this 2-yr longitudinal study. Advanced cardiac characteristics such as cardiac MRI with extracellular volume (ECV) quantification, speckle tracking echocardiography, and biomarkers were assessed at 0/6/12/18/24 mo. Patients were followed-up for a median of 30 mo with registration of acute decompensations (ADs), liver transplantations (LTs), and deaths. Patients who progressed, underwent LT or died had more pronounced cardiac dysfunction, structural myocardial changes, and left atrial enlargement. Conversely, limited cardiac deterioration was seen in patients who remained stable or improved in cirrhosis. During follow-up 25 patients developed AD, 4 underwent LT, and 20 died. Mean arterial pressure was the only cardiovascular parameter associated with death in a univariate analysis (P = 0.037), and the main predictors were model for end-stage liver disease and age. However, last-visit myocardial ECV was independently associated with the combined end point of LT/death (P = 0.001), and in patients with AD a low cardiac index was independently associated with death (P = 0.01). Cardiac function seems to deteriorate with the progression of cirrhosis and affects prognosis, especially in patients with AD. Conversely, patients with stable cirrhosis have limited progression in cardiac dysfunction over a 2-yr period with modest impact on survival. The results encourage careful cardiac monitoring in advanced cirrhosis.NEW & NOTEWORTHY For the first time, we have performed advanced cardiac imaging to investigate the development of cirrhotic cardiomyopathy over 2 years. We show that cardiac dysfunction deteriorates with progression of cirrhosis and may affect the prognosis in patients developing acute decompensation. Especially, structural myocardial abnormalities, left atrial enlargement, and a hypodynamic cardiac state seem of importance. Conversely, limited cardiac progression is seen in stable cirrhosis. These findings provide new insight into our understanding of cirrhotic cardiomyopathy.

Long-term outcome and necessity of liver transplantation in infants with biliary atresia are independent of cytokine milieu in native liver and serum.

PURPOSE: Biliary atresia (BA) is a rare disease of unknown pathogenesis in infants characterized by an inflammatory, progressive destruction of the biliary system and deterioration of liver function. The standard treatment for BA is a Kasai-hepatoportoenterostomy (KPE). However, liver transplantation (LTX) becomes necessary in about 50-80% of cases. Therefore, some authors advocate for primary LTX in BA, but this would require early markers to predict which children would benefit from KPE or to show rapid progression to liver cirrhosis (RLC) instead. METHODS: Snap-frozen liver biopsies and sera samples of 57 infants with BA were collected during KPE. Clinical and follow-up data were assessed via the biliary atresia and related diseases registry (BARD-online.com). Protein-levels of 25 pro- and anti-inflammatory mediators of 49 infants were assessed via multiplex protein-immunoassay and analyzed by t-test as well as multidimensional principal component analysis. RESULTS: 22 different immunomodulatory mediators were detectable in livers of children with BA, while serum protein levels were very low to undetectable. Following KPE, 33 BA patients showed RLC that required early LTX, while 24 had favorable course of disease with long-term survival with native liver (SNL). There were no significant differences between RLC and SNL in terms of local (from liver samples) nor systemic (from sera) immunomodulatory mediators. Protein levels were much lower in sera than in livers without statistical correlation. CONCLUSION: Our data suggest that local or systemic immunomodulatory mediators are unsuitable for predicting the disease course of BA. Thus, no deduction for optimal treatment strategy can be drawn. Collectively, we conclude that in BA, the degree of inflammation and protein microenvironment in the liver at the time-point of KPE are dismissible factors for the future course of disease.

Myocardial extracellular volume quantified by magnetic resonance is increased in cirrhosis and related to poor outcome.

BACKGROUND & AIMS: The underlying pathogenesis of cirrhotic cardiomyopathy remains unclear. Structural myocardial changes including diffuse fibrosis may be involved and can be accurately assessed by cardiac MRI (CMR) with quantification of the extracellular volume (ECV).This is the first application of this technique in patients with cirrhosis. We aimed to investigate the presence of diffuse myocardial fibrosis and to determine the relation to disease severity, cardiac function and outcome. METHODS: A prospective study including 52 cirrhotic patients and 10 healthy controls. All patients underwent CMR with ECV quantification, tissue Doppler echocardiography, and biochemical assessments. Patients were followed up for a median of 25 months with registration of death and liver transplantation (LT). RESULTS: Myocardial ECV was higher in the patients compared with healthy controls (31.2 ± 6 vs 27.4 ± 3%, P = .04). Furthermore, ECV increased across the Child Pugh A/B/C classes (26.9 ± 4/31.5 ± 5/34.4 ± 6%, P = .02). Four-teen patients experienced the composite end-point of death/LT during follow-up and these patients had higher ECV (33.2 ± 4 vs 30.4 ± 6%, P = .04). In a univariate Cox regression analysis ECV was associated with poor transplant-free survival (HR 3.6 [1.1-11.6]; P = .03). However, MELD and CRP remained the strongest predictors in a multivariate analysis. ECV correlated with cardiac index (r = 0.44, P = .001), CRP (r = 0.46, P = .001), proANP (r = 0.50, P < .001), and proBNP (r = 0.40, P = .005). CONCLUSIONS: Myocardial ECV is increased in patients with cirrhosis and seems related to disease severity and transplant-free survival. These changes most likely reflect subclinical diffuse myocardial fibrosis and may represent a structural element of cirrhotic cardiomyopathy.

Interleukin 17, Produced by γδ T Cells, Contributes to Hepatic Inflammation in a Mouse Model of Biliary Atresia and Is Increased in Livers of Patients.

BACKGROUND & AIMS: Biliary atresia (BA) is a rare disease in infants, with unknown mechanisms of pathogenesis. It is characterized by hepatobiliary inflammatory, progressive destruction of the biliary system leading to liver fibrosis, and deterioration of liver function. Interleukin (IL) 17A promotes inflammatory and autoimmune processes. We studied the role of IL17A and cells that produce this cytokine in a mouse model of BA and in hepatic biopsy samples from infants with BA. METHODS: We obtained peripheral blood and liver tissue specimens from 20 patients with BA, collected at the time of Kasai portoenterostomy, along with liver biopsies from infants without BA (controls). The tissue samples were analyzed by reverse transcription quantitative polymerase chain reaction (PCR), in situ PCR, and flow cytometry analyses. BA was induced in balb/cAnNCrl mice by rhesus rotavirus infection; uninfected mice were used as controls. Liver tissues were collected from mice and analyzed histologically and by reverse transcriptase PCR; leukocytes were isolated, stimulated, and analyzed by flow cytometry and PCR analyses. Some mice were given 3 intraperitoneal injections of a monoclonal antibody against IL17 or an isotype antibody (control). RESULTS: Livers from rhesus rota virus-infected mice with BA had 7-fold more Il17a messenger RNA than control mice (P = .02). γδ T cells were the exclusive source of IL17; no T-helper 17 cells were detected in livers of mice with BA. The increased number of IL17a-positive γδ T cells liver tissues of mice with BA was associated with increased levels of IL17A, IL17F, retinoid-orphan-receptor C, C-C chemokine receptor 6, and the IL23 receptor. Mice that were developing BA and given antibodies against IL17 had lower levels of liver inflammation and mean serum levels of bilirubin than mice receiving control antibodies (191 µmol/L vs 78 µmol/L, P = .002). Liver tissues from patients with BA had 4.6-fold higher levels of IL17 messenger RNA than control liver tissues (P = .02). CONCLUSIONS: In livers of mice with BA, γδ T cells produce IL17, which is required for inflammation and destruction of the biliary system. IL17 is up-regulated in liver tissues from patients with BA, compared with controls, and might serve as a therapeutic target.

Biliary atresia: unity in diversity.

Biliary atresia (BA) is a rare disease of unknown origin and unsatisfying outcome. Single, multicenter and national evaluations of epidemiological and outcome data on BA have been periodically published over the course of decades. However, the diversity of the registered parameters and outcome measures impede comparability and cumulative analysis of these very worthwhile studies. Taking into account the fact that BA is a good example of translational research and transition of patients from pediatric surgery and hepatology to transplant surgery and hepatology in general, the interdisciplinary community should make every effort to develop a common platform upon which further activities are conducted. Extending this topic to BA-related diseases might increase the acceptance of research studies and enhance the effectiveness of any recommendations outlined therein. The use of the Internet-based communication platform and registry on http://www.bard-online.com represents the first step in this direction, and the database should be viewed as a helpful tool that guides further activities.

Biliary atresia and other cholestatic childhood diseases: Advances and future challenges.

Biliary Atresia and other cholestatic childhood diseases are rare conditions affecting the function and/or anatomy along the canalicular-bile duct continuum, characterised by onset of persistent cholestatic jaundice during the neonatal period. Biliary atresia (BA) is the most common among these, but still has an incidence of only 1 in 10-19,000 in Europe and North America. Other diseases such as the genetic conditions, Alagille syndrome (ALGS) and Progressive Familial Intrahepatic Cholestasis (PFIC), are less common. Choledochal malformations are amenable to surgical correction and require a high index of suspicion. The low incidence of such diseases hinder patient-based studies that include large cohorts, while the limited numbers of animal models of disease that recapitulate the spectrum of disease phenotypes hinders both basic research and the development of new treatments. Despite their individual rarity, collectively BA and other cholestatic childhood diseases are the commonest indications for liver transplantation during childhood. Here, we review the recent advances in basic research and clinical progress in these diseases, as well as the research needs. For the various diseases, we formulate current key questions and controversies and identify top priorities to guide future research.

Quantitative modelling of amyloidogenic processing and its influence by SORLA in Alzheimer's disease.

The extent of proteolytic processing of the amyloid precursor protein (APP) into neurotoxic amyloid-ß (Aß) peptides is central to the pathology of Alzheimer's disease (AD). Accordingly, modifiers that increase Aß production rates are risk factors in the sporadic form of AD. In a novel systems biology approach, we combined quantitative biochemical studies with mathematical modelling to establish a kinetic model of amyloidogenic processing, and to evaluate the influence by SORLA/SORL1, an inhibitor of APP processing and important genetic risk factor. Contrary to previous hypotheses, our studies demonstrate that secretases represent allosteric enzymes that require cooperativity by APP oligomerization for efficient processing. Cooperativity enables swift adaptive changes in secretase activity with even small alterations in APP concentration. We also show that SORLA prevents APP oligomerization both in cultured cells and in the brain in vivo, eliminating the preferred form of the substrate and causing secretases to switch to a less efficient non-allosteric mode of action. These data represent the first mathematical description of the contribution of genetic risk factors to AD substantiating the relevance of subtle changes in SORLA levels for amyloidogenic processing as proposed for patients carrying SORL1 risk alleles.

σ1B adaptin regulates adipogenesis by mediating the sorting of sortilin in adipose tissue.

Here, we describe altered sorting of sortilin in adipocytes deficient for the σ1B-containing AP-1 complex, leading to the inhibition of adipogenesis. The AP-1 complex mediates protein sorting between the trans-Golgi network and endosomes. Vertebrates express three AP1 σ1 subunit isoforms - σ1A, σ1B and σ1C (also known as AP1S1, AP1S2 and AP1S3, respectively). σ1B-deficient mice display impaired recycling of synaptic vesicles and lipodystrophy. Here, we show that sortilin is overexpressed in adipose tissue from σ1B(-/-) mice, and that its overexpression in wild-type cells is sufficient to suppress adipogenesis. σ1B-specific binding of sortilin requires the sortilin DxxD-x12-DSxxxL motif. σ1B deficiency does not lead to a block of sortilin transport out of a specific organelle, but the fraction that reaches lysosomes is reduced. Sortilin binds to the receptor DLK1, an inhibitor of adipocyte differentiation, and the overexpression of sortilin prevents DLK1 downregulation, leading to enhanced inhibition of adipogenesis. DLK1 and sortilin expression are not increased in the brain tissue of σ1B(-/-) mice, although this is the tissue with the highest expression of σ1B and sortilin. Thus, adipose-tissue-specific and σ1B-dependent routes for the transport of sortilin exist and are involved in the regulation of adipogenesis and adipose-tissue mass.

Additive prognostic value of plasma N-terminal pro-brain natriuretic peptide and coronary artery calcification for cardiovascular events and mortality in asymptomatic patients with type 2 diabetes.

BACKGROUND: In patients with type 2 diabetes, cardiovascular disease (CVD) is the major cause of morbidity and mortality. We evaluated the combination of NT-proBNP and coronary artery calcium score (CAC) for prediction of combined fatal and non-fatal CVD and mortality in patients with type 2 diabetes and microalbuminuria (>30 mg/24-h), but without known coronary artery disease. Moreover, we assessed the predictive value of a predefined categorisation of patients into a high- and low-risk group at baseline. METHODS: Prospective study including 200 patients. All received intensive multifactorial treatment. Patients with baseline NT-proBNP > 45.2 ng/L and/or CAC ≥ 400 were stratified as high-risk patients (n = 133). Occurrence of fatal- and nonfatal CVD (n = 40) and mortality (n = 26), was traced after 6.1 years (median). RESULTS: High-risk patients had a higher risk of the composite CVD endpoint (adjusted hazard ratio [HR] 10.6 (95 % confidence interval [CI] 2.4-46.3); p = 0.002) and mortality (adjusted HR 5.3 (95 % CI 1.2-24.0); p = 0.032) compared to low-risk patients. In adjusted continuous analysis, both higher NT-proBNP and CAC were strong predictors of the composite CVD endpoint and mortality (p ≤ 0.0001). In fully adjusted models mutually including NT-proBNP and CAC, both risk factors remained associated with risk of CVD and mortality (p ≤ 0.022). There was no interaction between NT-proBNP and CAC for the examined endpoints (p ≥ 0.31). CONCLUSIONS: In patients with type 2 diabetes and microalbuminuria but without known coronary artery disease, NT-proBNP and CAC were strongly associated with fatal and nonfatal CVD, as well as with mortality. Their additive prognostic capability holds promise for identification of patients at high risk.

Sortilin, encoded by the cardiovascular risk gene SORT1, and its suggested functions in cardiovascular disease.

Several genome-wide association studies have linked novel loci to a wide range of cardiovascular phenotypes including low-density lipoprotein (LDL)-cholesterol, early onset myocardial infarction, coronary artery calcification, coronary artery stenosis, and abdominal aorta aneurysm. Especially, one locus, namely, 1p13.3, has attracted much attention. This locus harbors four candidate genes, CELSR2, PSRC1, MYBPHL, and SORT1. SORT1 encodes sortilin, a type I sorting receptor that has recently been implicated in LDL-cholesterol metabolism, VLDL secretion, PCSK9 secretion, and development of atherosclerotic lesions. Furthermore, sortilin also seems to be involved in the development of atherosclerosis, by mechanisms not directly involving LDL-cholesterol, but possibly resulting from the attenuated secretion of proinflammatory cytokines, such as IL6 and TNFα, which accompanies lack of sortilin in immune cells. Sortilin seems to play an important role in the development of cardiovascular disease and have functions beyond regulating LDL-cholesterol.

ABSENCE OF A THYROID PHENOTYPE IN SORTILIN-DEFICIENT MICE.

OBJECTIVE: The Vps10p family member sortilin is expressed in thyroid epithelial cells where it contributes to recycling of the thyroid hormone precursor thyroglobulin (Tg), a process that is thought to render hormone release more effective. Here we investigated the functional impact of sortilin in the thyroid gland using sortilin-deficient mice. METHODS: We measured free T4, thyroid-stimulating hormone (TSH) and Tg serum levels and studied thyroid morphology in 14 sortilin-deficient (Sort1)(-/-)and 12 wildtype (WT) mice. RESULTS: Serum free T4 levels did not differ between Sort1(-/-)and WT females but were significantly lower in Sort1(-/-)males compared with WT (P = .0424). Neither serum TSH nor Tg levels differed between Sort1(-/-)and WT mice, regardless of sex. On the same line, no thyroid histology differences were observed. CONCLUSION: Our findings seem to exclude a role of sortilin in thyroid hormone secretion, although it is possible that the absence of sortilin may result in a thyroid phenotype if combined with other molecular defects of thyroid hormone synthesis and secretion or under iodine deficiency.

Human sorCS1 binds sortilin and hampers its cellular functions.

Sortilin and sorCS1 [sortilin-related Vps10p (vacuolar protein sorting/targeting protein 10) domain-containing receptor 1], both members of the Vps10p-D (Vps10p-domain) receptor family, are synthesized as precursor proteins and are converted into their mature form by enzymatic cleavage of a short N-terminal propeptide. SorCS1 does not bind its propeptide, but sortilin is able to bind not just its own propeptide, but also that of sorCS1. In the present study we show that the propeptide region of sorCS1 contains two separate sites for binding to sortilin and that only one of these sites is removed from human (as opposed to mouse) sorCS1 during processing. This leaves mature human sorCS1 with a sortilin-binding N-terminus, which allows formation of a complex between the two receptors in solution and on cell membranes. Furthermore, we find that the interaction with sorCS1 has a pronounced effect on sortilin's ability to mediate the cellular uptake of alternative ligands, and to hamper its facilitation of CNTF (ciliary neutrophic factor) signalling and the induction of phosphorylated STAT3 (signal transducer and activator of transcription 3). Thus the present study reveals a novel regulatory mechanism and suggest an entirely new role for sorCS1 as a modulator of sortilin function.

Sortilin and SorLA display distinct roles in processing and trafficking of amyloid precursor protein.

The development and progression of Alzheimer's disease is linked to excessive production of toxic amyloid-ß peptide, initiated by ß-secretase cleavage of the amyloid precursor protein (APP). In contrast, soluble APPα (sAPPα) generated by the α-secretase is known to stimulate dendritic branching and enhance synaptic function. Regulation of APP processing, and the shift from neurotrophic to neurotoxic APP metabolism remains poorly understood, but the cellular localization of APP and its interaction with various receptors is considered important. We here identify sortilin as a novel APP interaction partner. Like the related APP receptor SorLA, sortilin is highly expressed in the CNS, but whereas SorLA mainly colocalizes with APP in the soma, sortilin interacts with APP in neurites. The presence of sortilin promotes α-secretase cleavage of APP, unlike SorLA, which inhibits the generation of all soluble products. Also, sortilin and SorLA both bind and mediate internalization of sAPP but to different cellular compartments. The interaction involves the 6A domain of APP, present in both neuronal and non-neuronal APP isoforms. This is important as sAPP receptors described so far only bind the non-neuronal isoforms, leaving SorLA and sortilin as the only receptors for sAPP generated by neurons. Together, our findings establish sortilin, as a novel APP interaction partner that influences both production and cellular uptake of sAPP.

The pro-neurotrophin receptor sortilin is a major neuronal apolipoprotein E receptor for catabolism of amyloid-ß peptide in the brain.

Apolipoprotein E (APOE) is the major risk factor for sporadic Alzheimer's disease. Among other functions, APOE is proposed to sequester neurotoxic amyloid-ß (Aß) peptides in the brain, delivering them to cellular catabolism via neuronal APOE receptors. Still, the receptors involved in this process remain controversial. Here, we identified the pro-neurotrophin receptor sortilin as major endocytic pathway for clearance of APOE/Aß complexes in neurons. Sortilin binds APOE with high affinity. Lack of receptor expression in mice results in accumulation of APOE and of Aß in the brain and in aggravated plaque burden. Also, primary neurons lacking sortilin exhibit significantly impaired uptake of APOE/Aß complexes despite proper expression of other APOE receptors. Despite higher than normal brain APOE levels, sortilin-deficient animals display anomalies in brain lipid metabolism (e.g., accumulation of sulfatides) seen in APOE-deficient mice, indicating functional deficiency in cellular APOE uptake pathways. Together, our findings identified sortilin as an essential neuronal pathway for APOE-containing lipoproteins in vivo and suggest an intriguing link between Aß catabolism and pro-neurotrophin signaling converging on this receptor.

Diastolic and autonomic dysfunction in early cirrhosis: a dobutamine stress study.

OBJECTIVE. Presence of cardiac dysfunction in patients with advanced cirrhosis is widely accepted, but data in early stages of cirrhosis are limited. Systolic and diastolic functions, dynamics of QT-interval, and pro-atrial natriuretic peptide (pro-ANP) are investigated in patients with early stage cirrhosis during maximal ß-adrenergic drive. MATERIAL AND METHODS. Nineteen patients with Child A (n = 12) and Child B cirrhosis (n = 7) and seven matched controls were studied during cardiac stress induced by increasing dosages of dobutamine and atropine. RESULTS. Pharmacological responsiveness was similar in cirrhosis and controls and the heart rate (HR) increased by 66 ± 15 versus 67 ± 8 min(-1). HR-blood pressure product increased equally by 115% in both cirrhotic patients and controls. However, time to resume HR of 100 beats/min was significantly longer in cirrhosis, p < 0.01. The QTc interval increased after dobutamine infusion in cirrhosis (0.41 ± 0.02 vs. 0.43 ± 0.02 s, p = 0.001) but similar electrophysiological changes were seen in controls. Cardiac volumes increased with the severity of disease. The increased cardiac output was primarily attributed to increased stroke volume. The ejection fraction was similar in patients and controls. Peak filling rate was longer in cirrhosis compared to controls (1.8 ± 0.4 and 1.4 ± 0.2 end-diastolic volume/s, p < 0.01). Pro-ANP was higher in cirrhosis and increased during stress by 13% compared to 0% in controls, p < 0.01. CONCLUSIONS. These findings indicate that patients with early stage cirrhosis exhibit early diastolic and autonomic dysfunction as well as elevated pro-ANP. However, the cardiac chronotropic and inotropic responses to dobutamine stress were normal. The dynamics of ventricular repolarization appears normal in patients with early stage cirrhosis.