CaMK1D signalling in AgRP neurons promotes ghrelin-mediated food intake.

Hypothalamic AgRP/NPY neurons are key players in the control of feeding behaviour. Ghrelin, a major orexigenic hormone, activates AgRP/NPY neurons to stimulate food intake and adiposity. However, cell-autonomous ghrelin-dependent signalling mechanisms in AgRP/NPY neurons remain poorly defined. Here we show that calcium/calmodulin-dependent protein kinase ID (CaMK1D), a genetic hot spot in type 2 diabetes, is activated upon ghrelin stimulation and acts in AgRP/NPY neurons to mediate ghrelin-dependent food intake. Global Camk1d-knockout male mice are resistant to ghrelin, gain less body weight and are protected against high-fat-diet-induced obesity. Deletion of Camk1d in AgRP/NPY, but not in POMC, neurons is sufficient to recapitulate above phenotypes. In response to ghrelin, lack of CaMK1D attenuates phosphorylation of CREB and CREB-dependent expression of the orexigenic neuropeptides AgRP/NPY in fibre projections to the paraventricular nucleus (PVN). Hence, CaMK1D links ghrelin action to transcriptional control of orexigenic neuropeptide availability in AgRP neurons.

Combined Analysis of Metabolomes, Proteomes, and Transcriptomes of Hepatitis C Virus-Infected Cells and Liver to Identify Pathways Associated With Disease Development.

BACKGROUND & AIMS: The mechanisms of hepatitis C virus (HCV) infection, liver disease progression, and hepatocarcinogenesis are only partially understood. We performed genomic, proteomic, and metabolomic analyses of HCV-infected cells and chimeric mice to learn more about these processes. METHODS: Huh7.5.1dif (hepatocyte-like cells) were infected with culture-derived HCV and used in RNA sequencing, proteomic, metabolomic, and integrative genomic analyses. uPA/SCID (urokinase-type plasminogen activator/severe combined immunodeficiency) mice were injected with serum from HCV-infected patients; 8 weeks later, liver tissues were collected and analyzed by RNA sequencing and proteomics. Using differential expression, gene set enrichment analyses, and protein interaction mapping, we identified pathways that changed in response to HCV infection. We validated our findings in studies of liver tissues from 216 patients with HCV infection and early-stage cirrhosis and paired biopsy specimens from 99 patients with hepatocellular carcinoma, including 17 patients with histologic features of steatohepatitis. Cirrhotic liver tissues from patients with HCV infection were classified into 2 groups based on relative peroxisome function; outcomes assessed included Child-Pugh class, development of hepatocellular carcinoma, survival, and steatohepatitis. Hepatocellular carcinomas were classified according to steatohepatitis; the outcome was relative peroxisomal function. RESULTS: We quantified 21,950 messenger RNAs (mRNAs) and 8297 proteins in HCV-infected cells. Upon HCV infection of hepatocyte-like cells and chimeric mice, we observed significant changes in levels of mRNAs and proteins involved in metabolism and hepatocarcinogenesis. HCV infection of hepatocyte-like cells significantly increased levels of the mRNAs, but not proteins, that regulate the innate immune response; we believe this was due to the inhibition of translation in these cells. HCV infection of hepatocyte-like cells increased glucose consumption and metabolism and the STAT3 signaling pathway and reduced peroxisome function. Peroxisomes mediate ß-oxidation of very long-chain fatty acids; we found intracellular accumulation of very long-chain fatty acids in HCV-infected cells, which is also observed in patients with fatty liver disease. Cells in livers from HCV-infected mice had significant reductions in levels of the mRNAs and proteins associated with peroxisome function, indicating perturbation of peroxisomes. We found that defects in peroxisome function were associated with outcomes and features of HCV-associated cirrhosis, fatty liver disease, and hepatocellular carcinoma in patients. CONCLUSIONS: We performed combined transcriptome, proteome, and metabolome analyses of liver tissues from HCV-infected hepatocyte-like cells and HCV-infected mice. We found that HCV infection increases glucose metabolism and the STAT3 signaling pathway and thereby reduces peroxisome function; alterations in the expression levels of peroxisome genes were associated with outcomes of patients with liver diseases. These findings provide insights into liver disease pathogenesis and might be used to identify new therapeutic targets.

Lysosomes in nutrient signalling: A focus on pancreatic ß-cells.

Regulated insulin secretion from pancreatic ß-cells is a major process maintaining glucose homeostasis in mammals. Enhancing insulin release in response to chronic nutrient overload and obesity-related insulin resistance (pre-diabetes) requires several adaptive cellular mechanisms maintaining ß-cell health under such stresses. Once these mechanisms are overwhelmed, ß-cell failure occurs leading to full-blown Type 2 Diabetes (T2D). Nutrient-dependent macroautophagy represents one such adaptive mechanism in ß-cells. While macroautophagy levels are high and protective in ß-cells in pre-diabetes, they decrease at later stages contributing to ß-cell failure. However, mechanisms compromising macroautophagy in ß-cells remain poorly understood. In this review, we discuss how recently discovered signalling cascades that emanate from the limiting membrane of lysosomes contribute to changes in macroautophagy flux in physiology and disease. In particular, these mechanisms are put into context with ß-cell function highlighting most recently described links between nutrient-dependent lysosomal signalling pathways and insulin secretion. Understanding these mechanisms in response to metabolic stress might pave the way for development of more tailored treatment strategies aimed at preserving ß-cell health.

Histone propionylation is a mark of active chromatin.

Histones are highly covalently modified, but the functions of many of these modifications remain unknown. In particular, it is unclear how histone marks are coupled to cellular metabolism and how this coupling affects chromatin architecture. We identified histone H3 Lys14 (H3K14) as a site of propionylation and butyrylation in vivo and carried out the first systematic characterization of histone propionylation. We found that H3K14pr and H3K14bu are deposited by histone acetyltransferases, are preferentially enriched at promoters of active genes and are recognized by acylation-state-specific reader proteins. In agreement with these findings, propionyl-CoA was able to stimulate transcription in an in vitro transcription system. Notably, genome-wide H3 acylation profiles were redefined following changes to the metabolic state, and deletion of the metabolic enzyme propionyl-CoA carboxylase altered global histone propionylation levels. We propose that histone propionylation, acetylation and butyrylation may act in combination to promote high transcriptional output and to couple cellular metabolism with chromatin structure and function.

Protein kinase D at the Golgi controls NLRP3 inflammasome activation.

The inflammasomes are multiprotein complexes sensing tissue damage and infectious agents to initiate innate immune responses. Different inflammasomes containing distinct sensor molecules exist. The NLRP3 inflammasome is unique as it detects a variety of danger signals. It has been reported that NLRP3 is recruited to mitochondria-associated endoplasmic reticulum membranes (MAMs) and is activated by MAM-derived effectors. Here, we show that in response to inflammasome activators, MAMs localize adjacent to Golgi membranes. Diacylglycerol (DAG) at the Golgi rapidly increases, recruiting protein kinase D (PKD), a key effector of DAG. Upon PKD inactivation, self-oligomerized NLRP3 is retained at MAMs adjacent to Golgi, blocking assembly of the active inflammasome. Importantly, phosphorylation of NLRP3 by PKD at the Golgi is sufficient to release NLRP3 from MAMs, resulting in assembly of the active inflammasome. Moreover, PKD inhibition prevents inflammasome autoactivation in peripheral blood mononuclear cells from patients carrying NLRP3 mutations. Hence, Golgi-mediated PKD signaling is required and sufficient for NLRP3 inflammasome activation.

Liver ubiquitome uncovers nutrient-stress-mediated trafficking and secretion of complement C3.

Adaptation to changes in nutrient availability is crucial for cells and organisms. Posttranslational modifications of signaling proteins are very dynamic and are therefore key to promptly respond to nutrient deprivation or overload. Herein we screened for ubiquitylation of proteins in the livers of fasted and refed mice using a comprehensive systemic proteomic approach. Among 1641 identified proteins, 117 were differentially ubiquitylated upon fasting or refeeding. Endoplasmic reticulum (ER) and secretory proteins were enriched in the livers of refed mice in part owing to an ER-stress-mediated response engaging retro-translocation and ubiquitylation of proteins from the ER. Complement C3, an innate immune factor, emerged as the most prominent ER-related hit of our screen. Accordingly, we found that secretion of C3 from the liver and primary hepatocytes as well as its dynamic trafficking are nutrient dependent. Finally, obese mice with a chronic nutrient overload show constitutive trafficking of C3 in the livers despite acute changes in nutrition, which goes in line with increased C3 levels and low-grade inflammation reported for obese patients. Our study thus suggests that nutrient sensing in the liver is coupled to release of C3 and potentially its metabolic and inflammatory functions.

The impact of DMARD and anti-TNF therapy on functional characterization of short-term T-cell activation in patients with rheumatoid arthritis--a follow-up study.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by a systemic dysfunction of T-cells. In this study we tested the impact of DMARD and anti-TNF agents on short-term activation characteristics of T-cells. We enrolled 12 patients with newly diagnosed RA (naïve RA) who were treated with methothrexate (MTX) and glucocorticsteroid (GCS) and 22 patients with established RA non responding to conventional DMARD therapy who were treated with different anti-TNF agents. Nine healthy volunteers served as controls. Blood samples were taken at baseline, then at 4th and 8th week of therapy. The characteristics of several intracellular activation processes during short-term activation of T-cells including cytoplasmic Ca(2+) level, mitochondrial Ca(2+) level, reactive oxygen species (ROS) and nitric oxide (NO) generation were determined by a novel flow-cytometry technique. At baseline, the tested processes were comparable to controls in naïve RA. During GCS therapy, cytoplasmic Ca(2+) level and ROS generation decreased. After the addition of MTX to GCS cytoplasmic Ca(2+) level became comparable to controls, while ROS generation decreased further. In DMARD non responders, cytoplasmic Ca(2+) level was higher than controls at baseline. The cytoplasmic Ca(2+) level became comparable to controls and ROS generation decreased during each of the three anti-TNF-α agent therapies. Mitochondrial Ca(2+) level and NO generation were unaltered in all of the patient groups. These results indicate that intracellular machinery is affected in T-cells of RA patients. This may alter the behavior of T-cells during activation. Different therapeutic approaches may modulate the abnormal T-cell functions.

Adaptive immunity in ankylosing spondylitis: phenotype and functional alterations of T-cells before and during infliximab therapy.

Our aim was to assess the phenotype of T-cell subsets in patients with ankylosing spondylitis (AS), a chronic inflammatory rheumatic disease. In addition, we also tested short-term T-cell activation characteristics. Measurements were done in 13 AS patients before and during the intravenous therapy with anti-TNF agent infliximab (IFX). Flow cytometry was used to determine T-cell subsets in peripheral blood and their intracellular signaling during activation. The prevalence of Th2 and Th17 cells responsible for the regulation of adaptive immunity was higher in AS than in 9 healthy controls. Although IFX therapy improved patients' condition, immune phenotype did not normalize. Cytoplasmic and mitochondrial calcium responses of CD4+ and CD8+ cells to a specific activation were delayed, while NO generation was increased in AS. NO generation normalized sooner upon IFX than calcium response. These results suggest an abnormal immune phenotype with functional disturbances of CD4+ and CD8+ cells in AS.

Kinetic measurements using flow cytometry: new methods for monitoring intracellular processes.

The aim of our work was to establish flow cytometry methods for the characterization of mitochondrial Ca(2+) levels, plasma membrane potential, and superoxide generation and to relate kinetics to that of cytoplasmic Ca(2+) levels during short-term activation of T-lymphocytes. We monitored the change of fluorescence absorbance of sequentially measured Jurkat cells for 12 min. The cells were stained with the fluorescent dyes Fluo3-AM, Rhod2/AM, di-BA-C4-(5), or dihydroethidium and then were stimulated with increasing doses of phytohemagglutinin (PHA) or were treated with rotenone. Double-logistic function was fitted to cytoplasmic Ca(2+) signal and mitochondrial Ca(2+) levels, whereas logistic function was fitted to plasma membrane potential and superoxide levels. The calculated function parameters were area under the curve (AUC), maximum (Max), time to reach maximum (t(max)), slope at the first 50% value of Max (Slope), and ending (End) values, respectively. We found significant dose-response relationship between PHA dose and cytoplasmic Ca(2+) signals (AUC, Max, Slope: P<0.05), mitochondrial Ca(2+) levels (AUC and Max: P<0.05), and plasma membrane potential (AUC and End values: P<0.05). In rotenone-treated cells, superoxide generation increased in a dose-dependent manner (P<0.05 for AUC and End values, respectively). The present methodology provides an opportunity for monitoring and characterizing mitochondrial Ca(2+) levels, plasma membrane potential, and superoxide generation in PHA-activated or rotenone-treated Jurkat cells with flow cytometry.

Lymphocyte calcium influx kinetics in multiple sclerosis treated without or with interferon ß.

Kv1.3 and IKCa1 potassium channels play an important role in the maintenance of calcium-influx during lymphocyte activation and present a possible target for selective immunomodulation. We investigated the calcium-influx characteristics of Th1, Th2, CD4, CD8 T-lymphocytes isolated from multiple sclerosis patients without or with interferon-beta therapy, and its modulation by Kv1.3 and IKCa1 channel inhibitors using flow cytometry. Specific immunomodulation of the CD8 subset can be reached through inhibition of Kv1.3 channels in multiple sclerosis patients without interferon-beta. However, this effect is not specific enough concerning all lymphocyte subsets influencing the autoimmune response, since it also affects anti-inflammatory Th2 cells.

Lymphocyte activation in type 1 diabetes mellitus: the increased significance of Kv1.3 potassium channels.

Kv1.3 and IKCa1 potassium channels participate in the maintenance of calcium-influx during lymphocyte activation. Kv1.3 channels have a prominent role in specific T cell subsets, presenting a possible target for selective immunomodulation. We investigated the impact of Kv1.3 and IKCa1 channel inhibitors on calcium-influx characteristics in human T cells in type 1 diabetes mellitus. We isolated lymphocytes from 9 healthy and 9 type 1 diabetic individuals and measured the alteration of calcium-influx with flow cytometry in the Th1, Th2, CD4 and CD8 subsets after treatment of samples with specific channel inhibitors. Our results indicate an increased reactivity of type 1 diabetes lymphocytes, which is correlated to their increased sensitivity to Kv1.3 channel inhibition. However, the contribution of Kv1.3 channels to calcium flux is not exclusive for a specific lymphocyte subset as previous reports suggest, but is characteristic for each subset investigated. Therefore, the proposed inhibition of Kv1.3 channels as a novel therapeutic approach for the treatment of type 1 diabetes mellitus may have a major effect on overall lymphocyte function in this disease.

Decreased number of FoxP3+ regulatory T cells in preeclampsia.

Systemic inflammation is characteristic for preeclampsia (PE). A hypothesis for immune dysregulation is that the function of regulatory T cells (CD4(+)FoxP3(+), Tregs) inhibiting the activation of lymphocytes is impaired. We investigated the proportion of Tregs and their cellular network in preeclamptic women. Fifteen preeclamptic and 17 healthy pregnant women were enrolled in the 32nd gestational week (median age 29 (range 22-45) and 32 (range 26-38) years, respectively). PE was diagnosed according to international criteria at a median of 30 gestational weeks (range 21-31). Peripheral blood was taken and blood mononuclear cells were isolated. Flow cytometry was used to determine the proportion of regulatory (CD4+FoxP3+) T cells, lymphoid and myeloid dendritic cells, natural killer and natural killer T cells, naive and memory and activated CD4+ and CD8+cells. The proportion of Tregs and that of naive CD4(+)CD45RA(+) cells was lower in preeclamptic than in control women (p=0.025, p=0.04, respectively). The proportion of other investigated cell types did not differ. Low Treg numbers may support the notion that PE shares similar features to autoimmune disorders. Low Treg numbers are not reflected in the proportion of activated lymphocytes, at least in this stage of pregnancy. This does not exclude, however, the functional alterations of these cell types.

Published genetic variants in retinopathy of prematurity: random forest analysis suggests a negligible contribution to risk and severity.

PURPOSE: Our recent investigations suggested association between severe retinopathy of prematurity (ROP) and some genetic polymorphisms contributing to angiogenesis. While these findings may help to identify specific elements in ROP pathogenesis, the predictive value of these genetic variants at birth is unknown. We applied a high-dimensional nonparametric method called random forest technique (RFT) to evaluate the predictive value of genetic polymorphisms in ROP at birth. METHODS: We used published genetic (i.e., VEGF T(-460)C, G(+ 405)C, and C(-2578)A; IGF-I receptor G(+ 3174)A, angiopoietin II G(-35)C; estrogen receptor PvuII Pp; and endothelial NO-synthase 27-bp b/a and T(-786)C) and birth data of 134 preterm infants without and 103 preterm infants with ROP requiring laser or cryotherapy. We used RFT to determine the relative importance scores (IS) of each clinical parameter at birth and genetic polymorphisms in the prediction of ROP. The accuracy of ROP prediction at birth was calculated when birth data, genotype data, and birth data PLUS genotype data were taken into account. RESULTS: The most important predictors of ROP were prematurity, low birth weight, intrauterine retardation, and Apgar scores with IS values between 7.46 and 13.20. IS values of genotype data were much lower in the range between 0.86 and 4.19. When birth data solely, genotype data solely, and birth data plus genotype data together were used for prediction, the accuracy of prediction was 0.653, 0.636, and 0.674, respectively. CONCLUSIONS: The tested genetic polymorphisms (including those published as significant risk factors of ROP) are not good predictors of ROP at birth.