Sodium tungstate regulates food intake and body weight through activation of the hypothalamic leptin pathway.

AIMS: Sodium tungstate is an anti-obesity drug targeting peripheral tissues. In vivo, sodium tungstate reduces body weight gain and food intake through increasing energy expenditure and lipid oxidation, but it also modulates hypothalamic gene expression when orally administered, raising the possibility of a direct effect of sodium tungstate on the central nervous system. METHODS: Sodium tungstate was administered intraperitoneally (ip) to Wistar rats, and its levels were measured in cerebrospinal fluid through mass spectrometry. Body weight gain and food intake were monitored for 24 h after its administration in the third ventricle. Hypothalamic protein was obtained and subjected to western blot. In vitro, hypothalamic N29/4 cells were treated with 100 µM sodium tungstate or 1 nM leptin, and protein and neural gene expression were analysed. RESULTS: Sodium tungstate crossed the blood-brain barrier, reaching a concentration of 1.31 ± 0.07 mg/l in cerebrospinal fluid 30 min after ip injection. When centrally administered, sodium tungstate decreased body weight gain and food intake and increased the phosphorylation state of the main kinases and proteins involved in leptin signalling. In vitro, sodium tungstate increased the phosphorylation of janus kinase-2 (JAK2) and extracellular signal-regulated kinase-1/2 (ERK1/2), but the activation of each kinase did not depend on each other. It regulated c-myc gene expression through the JAK2/STAT system and c-fos and AgRP (agouti-related peptide) gene expression through the ERK1/2 pathway simultaneously and independently. CONCLUSIONS: Sodium tungstate increased the activity of several kinases involved in the leptin signalling system in an independent way, making it a suitable and promising candidate as a leptin-mimetic compound in order to manage obesity.

NG2 and GFAP co-expression after differentiation in cells transfected with mutant GFAP and in undifferentiated glioma cells. / Coexpresión de NG2/GFAP tras la diferenciación en células transfectadas con las mutaciones de GFAP y en células procedentes de gliomas indiferenciados.

INTRODUCTION: Alexander disease is a rare disorder caused by mutations in the gene coding for glial fibrillary acidic protein (GFAP). In a previous study, differentiation of neurospheres transfected with these mutations resulted in a cell type that expresses both GFAP and NG2. OBJECTIVE: To determine the effect of molecular marker mutations in comparison to undifferentiated glioma cells simultaneously expressing GFAP and NG2. METHODS: We used samples of human glioblastoma (GBM) and rat neurospheres transfected with GFAP mutations to analyse GFAP and NG2 expression after differentiation. We also performed an immunocytochemical analysis of neuronal differentiation for both cell types and detection of GFAP, NG2, vimentin, Olig2, and caspase-3 at 3 and 7 days from differentiation. RESULTS: Both the cells transfected with GFAP mutations and GBM cells showed increased NG2 and GFAP expression. However, expression of caspase-3-positive cells was found to be considerably higher in transfected cells than in GBM cells. CONCLUSIONS: Our results suggest that GFAP expression is not the only factor associated with cell death in Alexander disease. Caspase-3 expression and the potential role of NG2 in increasing resistance to apoptosis in cells co-expressing GFAP and NG2 should be considered in the search for new therapeutic strategies for the disease.

Role of iduronate-2-sulfatase in glucose-stimulated insulin secretion by activation of exocytosis.

Iduronate-2-sulfatase (IDS) is a lysosomal enzyme expressed in pancreatic islets responsible for the degradation of proteoglycans such as perlecan and dermatan sulfate. Previous findings of our group demonstrated the involvement of IDS in the normal pathway of lysosomal degradation of secretory peptides, suggesting a role of this enzyme in beta-cell secretory functionality. The present study was undertaken to characterize the effect of IDS overexpression on insulin release. INS1E cells were transiently transfected with a construct encoding human IDS (hIDS). hIDS overexpression was associated with a gain of function detected by a reduction in heparan sulfate content. hIDS potentiated the glucose-stimulated insulin secretory response compared with controls (61%) with no changes in insulin mRNA levels or insulin peptide content. Results on quantification of the exocytotic process showed a significant increase in hIDS-transfected cells compared with controls. Furthermore, ultramorphological analysis demonstrated an increase in the number of granules in the immediate vicinity of the plasma membrane in hIDS-transfected cells and a decrease in total vesicles per square micrometer. hIDS overexpression induced phosphorylation of protein kinase C (PKC) alpha and its newly myristoylated alanine-rich C kinase substrate, MARCKS. We conclude that IDS has a role in glucose-stimulated insulin secretion via a mechanism that involves the activation of exocytosis through phosphorylation of PKCalpha and MARCKS.

Myelin changes in Alexander disease. / La alteración de la mielina en la enfermedad de Alexander.

INTRODUCTION: Alexander disease (AxD) is a type of leukodystrophy. Its pathological basis, along with myelin loss, is the appearance of Rosenthal bodies, which are cytoplasmic inclusions in astrocytes. Mutations in the gene coding for GFAP have been identified as a genetic basis for AxD. However, the mechanism by which these variants produce the disease is not understood. DEVELOPMENT: The most widespread hypothesis is that AxD develops when a gain of function mutation causes an increase in GFAP. However, this mechanism does not explain myelin loss, given that experimental models in which GFAP expression is normal or mutated do not exhibit myelin disorders. This review analyses other possibilities that may explain this alteration, such as epigenetic or inflammatory alterations, presence of NG2 (+) - GFAP (+) cells, or post-translational modifications in GFAP that are unrelated to increased expression. CONCLUSIONS: The different hypotheses analysed here may explain the myelin alteration affecting these patients, and multiple mechanisms may coexist. These theories raise the possibility of designing therapies based on these mechanisms.

Transmission of high-risk HLA-DQB1 alleles in Chilean type 1 diabetic patients and their parents: stratification by the presence of ICA or GAD65 autoantibodies.

AIM: The purpose of this study was to assess whether the transmission of DQB1*0201 and DQB1*0302 alleles from heterozygous parents to Chilean type 1 diabetic patients depends on the presence of antibodies such as glutamic acid decarboxilase (GAD65) or Islet Cell (ICA) autoantibodies in the affected case. MATERIAL AND METHODS: A study of incident type 1 diabetic cases and parents was carried out in Santiago, Chile during 1997-98. The use of the case-parental design eliminates the possibility that case-controls differences are due to selection of controls whose genetic backgrounds differ systematically from those of cases. HLA-DQB1 polymorphisms were determined in cases and parents from n = 83 families using polymerase chain reaction and oligonucleotide dot-blot analysis. Detection of GAD65 antibodies was performed using a simple radio-binding asssay. Conventional ICA were detected by indirect immunofluorescence. RESULTS: Transmission disequilibrium test indicate a strong association between DQB1*0201 and DQB1*0302 and type I diabetes. When comparing the two subsets of families defined by having an affected child tested negative or positive for GAD65 antibodies (39 and 44 case-parent trios respectively) the probability of transmission of DQB1*0201 significantly differed between such strata (p-value=0.025). The pattern of transmission of DQB1*201 allele was also significantly different in the two subsets of families defined by ICA-or ICA+ cases (23 and 60 trios respectively) (p-value = 0.028). No differences were found in the transmission of DQB1*0302 allele in the different strata defined by the autoimmunity status of the proband. CONCLUSION: Our results reveal that DQB1*0201 allele may display distinct associations with type I diabetes depending on the autoimmunity to ICA and GAD65 autoantibodies.

In vitro proliferation, differentiation and immuno-magnetic bead purification of human myoblasts.

OBJECTIVES: In vitro culture of myoblasts and subsequent grafting into injured myocardium represents a new therapeutic approach for the treatment of myocardial infarct. A major limitation to developing enough myoblasts to engrafting purpose is the isolation and purification. In the present work we purified myoblast from primary culture using an immunomagnetic bead technique. METHODS: Primary culture was obtained by trypsin-EDTA digestion of human muscle biopsies. Cells were cultured in DMEM growth medium containing 10% FBS, 2 mM L-glutamine and antibiotics. Immunotechniques using both monoclonal anti-myosin heavy chain (skeletal fast) and 5.1.H11 antibody combining with flow cytometry did identification of myoblasts. Positive selection was on myoblasts bound to 5.1.H11 incubating with human antimouse IgG coated magnetic beads (Dynabead) and subsequent isolation by magnet, releasing cells from beads with DNAse. RESULTS: More than 59% of primary cell culture are positive to 5.1.H11 and decreasing with passage. The coating of culture dish surface increased specific growth rate of myoblast clones twice. Positive selection allows to increasing concentration of myoblasts from 8.4% in mixed culture to more than 90% without affecting neither viability nor platting efficiency. CONCLUSION: Purification procedure reported here is easy, efficient and requires small amount of sample, which will facilitate the purpose of autologous implant.

Stable and functional regeneration of pancreatic beta-cell population in nSTZ-rats treated with tungstate.

AIMS/HYPOTHESIS: Sodium tungstate has recently emerged as an effective oral treatment for diabetes. We examined the effects of tungstate administration in the beta-cell mass of the pancreas as well as its therapeutic potential. METHODS: Sodium tungstate was administered via drinking water to healthy and neonatal streptozotocin (nSTZ)-diabetic rats for one month. The pancreas from each rat was removed and morphometric and immunocytochemical studies were carried out. The molecular mechanism of tungstate's action was also studied. RESULTS: In nSTZ rats administration of this compound normalised glycaemia, and increased insulinaemia and islet insulin content. Blood glucose concentrations were normalised as early as on day 4 of treatment, and tungstate treatment produced a partial recovery of beta-cell mass. The rats remained normoglycaemic after tungstate withdrawal. Morphometric studies showed that the increase in beta-cell mass was not due to beta-cell hypertrophy but to hyperplasia, with an increase in islet density in treated diabetic rats. Tungstate treatment increased extra-islet beta-cell replication without modifying intra-islet beta-cell replication rates. Moreover, the treatment induced increases in insulin-positive cells located close to ducts; and in PDX-1 positive cells scattered in the exocrine tissue, suggesting active neogenesis. In islets from treated diabetic rats, tungstate is able to increase the phosphorylation state of PDX-1 through the activation of p38. CONCLUSION/INTERPRETATION: These observations indicate that tungstate treatment is able to regenerate a stable, functional pancreatic beta-cell population which leads to and maintains normoglycaemia.

Islet cell and thyroid antibody prevalence in patients with hepatitis C virus infection: effect of treatment with interferon.

An increased prevalence of hepatitis C virus (HCV) infection in patients with diabetes and a higher prevalence of diabetes in HCV-infected patients have been reported. However, the relationship between these two conditions remains controversial. In addition, although the effect of interferon treatment on thyroid autoimmunity has been extensively reported, its influence on beta-cell autoantibodies has not been investigated. The aims of the study were (1) to evaluate whether autoimmune beta-cell damage could be involved in the development of diabetes mellitus in HCV-infected patients and (2) to determine whether interferon treatment influences the appearance of beta-cell and thyroid autoantibodies. The prevalence of islet cell autoantibodies (glutamic acid decarboxylase antibodies [GADAs], tyrosine phosphatase antibodies [IA-2s], islet cell antibodies [ICAs]) was assessed in 303 non-selected HCV-infected patients (277 non-diabetic and 26 type 2 diabetic patients) and in 273 sex- and age-matched control subjects. ICAs and thyroid autoantibodies were also determined before and 6 and 12 months after treatment with interferon for 24 weeks in a subgroup of 46 HCV-infected patients. GADAs were detected in 4 of 277 (1.4%) HCV-infected non-diabetic patients, 1 of 273 (0.3%) control subjects, and 0 of 26 (0%) HCV-infected patients with diabetes. Anti-IA2s and ICAs were negative in all subjects. Both GADAs and anti-IA2s were negative in all HCV-infected patients treated with interferon. After therapy, only thyroid antibodies became positive in 5 of 46 (10.9%) treated patients, disappearing in all but 1 of these at the 12-month follow-up. Our results suggest that beta-cell autoimmunity is not associated with HCV infection, thus making it unlikely that the increased diabetes mellitus prevalence among HCV-infected patients could be mediated by autoimmune mechanisms. In addition, interferon treatment induces a transient increase in thyroid autoantibodies but does not influence the appearance of beta-cell autoantibodies.