Metabolically-inactive glucagon-like peptide-1(9-36)amide confers selective protective actions against post-myocardial infarction remodelling

BACKGROUND: Glucagon-like peptide-1 (GLP-1) therapies are routinely used for glycaemic control in diabetes and their emerging cardiovascular actions have been a major recent research focus. In addition to GLP-1 receptor activation, the metabolically-inactive breakdown product, GLP-1(9-36)amide, also appears to exert notable cardiovascular effects, including protection against acute cardiac ischaemia. Here, we specifically studied the influence of GLP-1(9-36)amide on chronic post-myocardial infarction (MI) remodelling, which is a major driver of heart failure progression.

METHODS: Adult female C57BL/6 J mice were subjected to permanent coronary artery ligation or sham surgery prior to continuous infusion with GLP-1(9-36)amide or vehicle control for 4 weeks.

RESULTS: Infarct size was similar between groups with no effect of GLP-1(9-36)amide on MI-induced cardiac hypertrophy, although modest reduction of in vitro phenylephrine-induced H9c2 cardiomyoblast hypertrophy was observed. Whilst echocardiographic systolic dysfunction post-MI remained unchanged, diastolic dysfunction (decreased mitral valve E/A ratio, increased E wave deceleration rate) was improved by GLP-1(9-36)amide treatment. This was associated with modulation of genes related to extracellular matrix turnover (MMP-2, MMP-9, TIMP-2), although interstitial fibrosis and pro-fibrotic gene expression were unaltered by GLP-1(9-36)amide. Cardiac macrophage infiltration was also reduced by GLP-1(9-36)amide together with pro-inflammatory cytokine expression (IL-1β, IL-6, MCP-1), whilst in vitro studies using RAW264.7 macrophages revealed global potentiation of basal pro-inflammatory and tissue protective cytokines (e.g. IL-1β, TNF-α, IL-10, Fizz1) in the presence of GLP-1(9-36)amide versus exendin-4.

CONCLUSIONS: These data suggest that GLP-1(9-36)amide confers selective protection against post-MI remodelling via preferential preservation of diastolic function, most likely due to modulation of infiltrating macrophages, indicating that this often overlooked GLP-1 breakdown product may exert significant actions in this setting which should be considered in the context of GLP-1 therapy in patients with cardiovascular disease.

Compte rendu: Jannis Androutsopoulos (dir.) (2014), Mediatization and sociolinguistic change, Berlin/Boston, De Gruyter, coll. « Linguae & litterae. Publications of the School of Language & Literature Freiburg Institute for Advanced Studies, 36 », vii-557 p. [ISBN : 978-3-11-034357-1]

Résumé non disponible

Unesp Ciência, 2012, ano 4, número 36

Revista elaborada pela Assessoria de Comunicação e Imprensa da Reitoria da UNESP

Aquisição Fonético - Fonológica do português europeu dos 18 aos 36 meses

Objetivo: O objetivo deste estudo consistiu na descrição da aquisição fonética e fonológica de crianças falantes do Português Europeu (PE), da região Centro de Portugal Continental, com idades compreendidas entre os [18-­‐36[ meses. Mais especificamente pretendeu-­‐se traçar uma ordem cronológica de aquisição dos fones e verificar quais os processos fonológicos mais utilizados nas 3 faixas etárias ([18-­‐24[, [24-­‐30[, [30-­‐36[ meses). Foi ainda objetivo averiguar se existiam diferenças em relação ao número de fones produzidos adequadamente e ao número de processos fonológicos utilizados entre as faixas etárias e os sexos. Definir a ordem pela qual os fones vão surgindo no discurso da criança, isto é, a sua ordem de aquisição, também foi um objetivo deste estudo. Método: A amostra foi constituída por 69 crianças (2 da faixa etária [18-­‐24[m, 31 dos [24-­‐30[m e 36 dos [30-­‐36[m, de ambos os sexos, que frequentavam 6 creches do distrito de Aveiro. Para recolher os dados recorreu-­‐se a gravações digitais áudio usando as imagens do Teste Fonético-­‐Fonológico-­‐ALPE. Resultados: Na aquisição fonética verificou-­‐se que que a produção de fones aumentou significativamente à medida que a idade avançou. Também foram encontradas diferenças entre as 3 faixas etárias (p<0,05), mas não entre os sexos (p>0,05). Foi ainda possível traçar a ordem cronológica de aquisição de fones: vogais orais < vogais nasais < oclusivas orais < oclusivas nasais < fricativas < líquidas Laterais < líquidas vibrantes. Relativamente à aquisição fonológica não se verificaram diferenças entre as 3 faixas etárias e entre os sexos (p>0,05). Quanto aos processos fonológicos, os mais utilizados foram os de estruturação silábica, nomeadamente a redução de grupo consonântico, palatalização e omissão de consoante final. Conclusão: As conclusões de maior relevo incidem no facto das diferenças nas faixas etárias serem mais notórias para a aquisição fonética do que para a aquisição fonológica. Também se verificou que não existiam diferenças entre os sexos na aquisição fonética-­‐fonológica. Constatou-­‐se que nesta amostra as crianças mais velhas adquiriram mais fones que as crianças das faixas etárias mais precoces.

Connexin-36 contributes to control function of insulin-producing cells.

Connexin-36 (Cx36) is a gap junction protein expressed by the insulin-producing beta-cells. We investigated the contribution of this protein in normal beta-cell function by using a viral gene transfer approach to alter Cx36 content in the insulin-producing line of INS-1E cells and rat pancreatic islets. Transcripts for Cx43, Cx45, and Cx36 were detected by reverse transcriptase-PCR in freshly isolated pancreatic islets, whereas only a transcript for Cx36 was detected in INS-1E cells. After infection with a sense viral vector, which induced de novo Cx36 expression in the Cx-defective HeLa cells we used to control the transgene expression, Western blot, immunofluorescence, and freeze-fracture analysis showed a large increase of Cx36 within INS-1E cell membranes. In contrast, after infection with an antisense vector, Cx36 content was decreased by 80%. Glucose-induced insulin release and insulin content were decreased, whether infected INS-1E cells expressed Cx36 levels that were largely higher or lower than those observed in wild-type control cells. In both cases, basal insulin secretion was unaffected. Comparable observations on basal secretion and insulin content were made in freshly isolated rat pancreatic islets. The data indicate that large changes in Cx36 alter insulin content and, at least in INS-1E cells, also affect glucose-induced insulin release.

TAT-RasGAP317-326-mediated tumor cell death sensitization can occur independently of Bax and Bak.

The increase of cancer specificity and efficacy of anti-tumoral agents are prime strategies to overcome the deleterious side effects associated with anti-cancer treatments. We described earlier a cell-permeable protease-resistant peptide derived from the p120 RasGAP protein, called TAT-RasGAP317-326, as being an efficient tumor-specific sensitizer to apoptosis induced by genotoxins in vitro and in vivo. Bcl-2 family members regulate the intrinsic apoptotic response and as such could be targeted by TAT-RasGAP317-326. Our results indicate that the RasGAP-derived peptide increases cisplatin-induced Bax activation. We found no evidence, using in particular knock-out cells, of an involvement of other Bcl-2 family proteins in the tumor-specific sensitization activity of TAT-RasGAP317-326. The absence of Bax and Bak in mouse embryonic fibroblasts rendered them resistant to cisplatin-induced apoptosis and consequently to the sensitizing action of the RasGAP-derived peptide. Surprisingly, in the HCT116 colon carcinoma cell line, the absence of Bax and Bak did not prevent cisplatin-induced apoptosis and the ability of TAT-RasGAP317-326 to augment this response. Our study also revealed that p53, while required for an efficient genotoxin-induced apoptotic response, is dispensable for the ability of the RasGAP-derived peptide to improve the capacity of genotoxins to decrease long-term survival of cancer cells. Hence, even though genotoxin-induced Bax activity can be increased by TAT-RasGAP317-326, the sensitizing activity of the RasGAP-derived peptide can operate in the absence of a functional mitochondrial intrinsic death pathway.

Inhibition of cell migration and invasion mediated by the TAT-RasGAP317-326 peptide requires the DLC1 tumor suppressor.

TAT-RasGAP317-326, a peptide corresponding to the 317-326 sequence of p120 RasGAP coupled with a cell-permeable TAT-derived peptide, sensitizes the death response of various tumor cells to several anticancer treatments. We now report that this peptide is also able to increase cell adherence, prevent cell migration and inhibit matrix invasion. This is accompanied by a marked modification of the actin cytoskeleton and focal adhesion redistribution. Interestingly, integrins and the small Rho GTP-binding protein, which are well-characterized proteins modulating actin fibers, adhesion and migration, do not appear to be required for the pro-adhesive properties of TAT-RasGAP317-326. In contrast, deleted in liver cancer-1, a tumor suppressor protein, the expression of which is often deregulated in cancer cells, was found to be required for TAT-RasGAP317-326 to promote cell adherence and inhibit migration. These results show that TAT-RasGAP317-326, besides its ability to favor tumor cell death, hampers cell migration and invasion.

A WXW Motif Is Required for the Anticancer Activity of the TAT-RasGAP317-326 Peptide.

TAT-RasGAP317-326, a cell-permeable 10-amino acid-long peptide derived from the N2 fragment of p120 Ras GTPase-activating protein (RasGAP), sensitizes tumor cells to apoptosis induced by various anticancer therapies. This RasGAP-derived peptide, by targeting the deleted in liver cancer-1 (DLC1) tumor suppressor, also hampers cell migration and invasion by promoting cell adherence and by inhibiting cell movement. Here, we systematically investigated the role of each amino acid within the RasGAP317-326 sequence for the anticancer activities of TAT-RasGAP317-326. We report here that the first three amino acids of this sequence, tryptophan, methionine, and tryptophan (WMW), are necessary and sufficient to sensitize cancer cells to cisplatin-induced apoptosis and to reduce cell migration. The WMW motif was found to be critical for the binding of fragment N2 to DLC1. These results define the interaction mode between the active anticancer sequence of RasGAP and DLC1. This knowledge will facilitate the design of small molecules bearing the tumor-sensitizing and antimetastatic activities of TAT-RasGAP317-326.

Boethius, De institutione arithmetica, cum commentariis (2-36). - Gerbertus Remensis, Scholium ad Boethii Arithmeticam Institutionem, lib. II, cap. 1 (36) [fragment].

Au f. 36, une main du XIIIe s. a ajouté un passage du traité de Gerbert intitulé "Scholium ad Boethii Arithmeticam Institutionem".