Els transportadors de glucosa de difusió facilitada (GLUTs) són proteïnes essencials per permetre l'entrada de glucosa dins la cèl·lula. Concretament, el GLUT4 s'ha descrit com la isoforma més important per al manteniment de la glucèmia, ja que és el mediador de l'acció de la insulina per incrementar la taxa de captació de glucosa. Fins ara en peixos només s'han identificat quatre isoformes de GLUTs, i entre elles hi destaca el GLUT4, el qual va ser clonat per primera vegada en truita comuna ("Salmo trutta"). A l'inici d'aquesta tesi ja existien algunes evidències sobre la regulació de la insulina sobre l'expressió d'aquest transportador in vivo. No obstant, es desconeixia si l'acció de la insulina era un efecte directe sobre el teixit muscular o bé actuava a través d'altres mediadors. Per altra banda, tampoc es coneixia l'acció de la insulina sobre la proteïna GLUT4 de truita. Per tant, en aquesta tesi hem intentat resoldre aquestes qüestions per poder contribuir a un millor coneixement d'un dels elements importants que intervé en el metabolisme dels carbohidrats en els peixos teleostis.En aquest estudi es va demostrar que els nivells d'insulina circulants són capaços de modular el contingut de proteïna GLUT4 in vivo en el múscul esquelètic de truita i que aquesta regulació és específica del tipus de fibra muscular. També es va demostrar que els efectes de la insulina sobre l'expressió de GLUT4 en el múscul esquelètic de truita són deguts a l'acció directa d'aquesta sobre les cèl·lules musculars. L'expressió basal de GLUT4 augmenta al llarg de la diferenciació de les cèl·lules musculars de truita i, paral·lelament, també augmenta lleugerament l'expressió de GLUT1. La insulina i l'IGF-I estimulen l'expressió de GLUT4 i els seus efectes són més evidents en miotubs. La insulina, en general, promou l'acumulació d'ARN missatger de GLUT1 en les cèl·lules musculars de truita. Per altra banda, l'IGF-I augmenta l'expressió de GLUT1 en mioblasts.En aquesta tesi també es va estudiar la regulació del tràfic del GLUT4 de truita per la insulina en cèl·lules musculars L6. Amb aquest objectiu es va generar una línia estable de cèl·lules L6 que expressaven el GLUT4 de truita amb un epítop myc a la seva porció extracel·lular (btGLUT4myc). La insulina va estimular l'aparició del btGLUT4myc a la membrana plasmàtica, augmentant així la captació de glucosa en aquestes cèl·lules. No obstant, en estat basal un major percentatge de btGLUT4myc estava ja present a la superfície cel·lular comparat amb el GLUT4myc de rata. Els experiments d'internalització de GLUT4myc van demostrar que l'endocitosi del btGLUT4myc és més lenta que la del GLUT4myc de rata. Per tant, aquests resultats suggereixen que les diferències observades entre el tràfic del GLUT4 de truita i el GLUT4 de rata poden ser degudes a diferències en alguns motius aminoacídics dels quals en mamífers s'ha demostrat que participen en la internalització i la retenció intracel·lular del transportador en estat basal. També s'ha vist que la insulina estimula la translocació de btGLUT4 en les cèl·lules musculars de truita i com a conseqüència augmenta el transport de glucosa en aquestes cèl·lules. Per altra banda, els estudis d'immunofluorescència van demostrar que en estat basal el btGLUT4 es troba a l'interior de les cèl·lules de truita i concentrat a la regió perinuclear, tal i com s'ha descrit prèviament en mamífers.En conjunt podem concloure que els mecanismes de regulació de la insulina sobre el GLUT4 en el múscul esquelètic ja existeixen en els vertebrats inferiors, malgrat que presenten algunes diferències respecte als mamífers. Així, podem veure que al llarg de l'evolució s'ha perfeccionat la regulació de la captació de glucosa fins arribar a ser un mecanisme eficient que permet una recuperació ràpida de la glucèmia. / In the present work, we demostrated that insulin plasma levels may modulate GLUT4 protein content in vivo in trout skeletal muscle, but in a fiber-type dependent manner. Furthermore, insulin stimulates GLUT4 gene expression in trout skeletal muscle by acting directly on muscle cells. Basal GLUT4 expression increases throughout differentiation of muscle cells, as well as GLUT1 expression. Insulin and IGF-I increase GLUT4 mRNA levels, but their effects are more pronounced in fully differentiated myotubes. Insulin promotes mRNA accumulation in trout muscle cells. IGF-I increases GLUT1 expression in myoblasts.We also studied the regulation of trout GLUT4 traffic by insulin in L6 muscle cells. To address this issue we generated a stable cell line of L6 cells that express the myc-tagged trout GLUT4 (btGLUT4myc). Insulin stimulates btGLUT4myc translocation to the plasma membrane, resulting in an enhanced glucose uptake in these cells. However, in the basal state a higher percentage of btGLUT4myc is already present at the cell surface compared to rat-GLUT4myc. Internalization experiments of GLUT4myc demonstrated that btGLUT4myc endocytosis is slower than that of rat-GLUT4myc. Therefore, these data suggest that these differences between mammalian and fish GLUT4 in terms of traffic could be related to differences in the sequence of certain protein motifs shown to be important for internalization and intracellular retention of GLUT4. Moreover, insulin also stimulates the translocation of endogenous GLUT4 in trout muscle cells leading to an increased glucose transport activity in these cells. On the other hand, immunofluorescence experiments revealed that under basal conditions btGLUT4 is located in the cytoplasm of trout muscle cells and concentrated in the perinuclear region.Overall, we may conclude that the mechanisms of insulin regulation on GLUT4 in skeletal muscle already exist in lower vertebrates, although they present some differences compared to mammals. Thus, glucose transport regulation has been improved through evolution to become an efficient mechanism that allows a rapid recovery of glycaemia.

The focus of this thesis is to characterise the interactions between GLUT4-related SNARE proteins – syntaxin4, SNAP23 and VAMP2 – and a regulatory protein, Munc18c. GLUT4 is the primary insulin-regulated glucose transporter and is presentin fat and muscle cells. GLUT4 is held in intracellular pools of vesicles until it is transported to the cell surface upon insulin stimulation. Insulin initiates a cellular signalling cascade via the insulin receptor on the cell membrane, which in turn stimulates GLUT4 vesicles to move to the cell surface where they fuse to the plasmamembrane via SNARE proteins. SNAREs are membrane-anchored proteins present on both vesicle and target membranes that form a tight complex which brings themembranes together for fusion. Fusion of vesicles to the target membrane releases the vesicular cargo.SNARE-mediated membrane fusion is a conserved mechanism that controls many other vesicle fusion processes such as neurotransmitter release and yeast vesicular trafficking. However, the regulation of the SNARE mechanism is not fully understood. SNAREs can interact with many other proteins that could act as regulatory factors,and studies have focused primarily on a group of effector proteins called Sec1p/Munc18 (SM) proteins. SM proteins were discovered and characterised because they bind to one type of SNARE protein, syntaxin. The SM protein that interacts with the GLUT4-related SNARE, syntaxin4, is Munc18c.The aim of this thesis was to investigate Munc18c interactions with SNARE proteins, principally syntaxin4, using biochemical techniques with purified recombinant proteins. This work was carried out in several stages including: 1) development of methods to produce and purify GLUT4-related SNARE proteins, SNARE complexes and Munc18c, 2) development of an assay to quantify Munc18c interactions with binding partners using surface plasmon resonance, 3) investigation into interactions between Munc18c and SNARE ternary complex, 4) characterising Munc18c interactions with syntaxin4, and 5) developing a method to produce selenomethionine-containing Munc18c in a baculovirus system to be used in structural studies. The methods and outcomes of these experiments are described inthis thesis. There were two major outcomes from this work. Firstly, Munc18c interacts with SNARE ternary complex, and secondly, Munc18c requires only the N-terminal 29residues of syntaxin4 for an interaction to occur. These results were determined using pulldown assays with purified proteins, as well as other chromatographic methods to show that protein complexes were formed. The steps taken to develop these binding assays are also discussed. Initial crystallisation conditions forMunc18c-HIS and a peptide consisting of syntaxin4 residues 1-20 have been identified using crystallisation screens. The interactions determined for Munc18c binding to Sx4 are in direct contrast to those of neuronal SM protein, Munc18a, and its interaction with neuronal SNARE proteins - Munc18a does not bind to its ternary complex and binds to the entire cytoplasmic domain of Sx1a. Rather, the Munc18c:Sx4 interactions are similar to that for the yeast SM protein, Sly1p, which can interact with both its SNARE ternary complex and with its syntaxin via the Nterminal residues. Another interesting outcome of this research was that syntaxin4 binds to metals (cobalt and nickel). This finding represents the first reported for a syntaxin interacting with metals. Preliminary results indicate that un-tagged syntaxin4 can bind to cobalt resin, and to nickel immobilised on a chip. This interesting and novel property of syntaxin4 binding was serendipitously discovered while investigating conditions for the Munc18c assay. Overall, I have shown that Munc18c, the SM protein involved in GLUT4 trafficking, interacts with SNARE proteins in a different manner to its mammalian counterpart inneurons, Munc18a, and is more like Sly1p, a yeast ER-Golgi SM protein. Munc18c interacts with SNARE complexes and only the N-terminal residues of syntaxin4.These interactions demonstrate that the regulatory mechanism for SNARE-mediated fusion is conserved between yeast and mammals. This finding has several implications for the role of Munc18c in the exocytosis of GLUT4-containing vesicles. Munc18c could act at several stages in the fusion process via syntaxin4 binding.These interactions could involve binding to other proteins (such as synip or tomosyn), conformational switching of syntaxin4 or interaction with metal ions to induce conformational changes in the proteins. Finally, these studies of GLUT4 exocytosis contribute to our understanding of glucose transport disorders such as Type 2 diabetes and could one day pave the way for the design of therapeutic agents.

Phosphatidylinositol 5-phosphate (PtdIns5P) is the least well-characterised member of the phosphoinositide family of essential regulatory phospholipids. PtdIns5P levels are altered within cells in response to a number of stimuli and evidence is accumulating to suggest that it possesses important functions in cellular signalling. However, the physiological role of this lipid remains imperfectly understood. Previous studies have shown that PtdIns5P is elevated in adipocytes in response to insulin, and microinjection of PtdIns5P into these cells promotes plasma membrane insertion of the insulin-regulated glucose transporter GLUT4 (Sbrissa et al., 2004). This finding suggests a potential role of PtdIns5P as a mediator in insulin-stimulated glucose uptake, a process essential for efficient glucose homeostasis. As approximately 75% of postprandial glucose disposal is carried out by skeletal muscle, it is important to investigate the role of PtdIns5P in the response of this tissue to insulin. Therefore, this work has used differentiated myotubes of the rat muscle cell line, L6, to explore the effects of altered PtdIns5P levels on insulin-stimulated glucose uptake. This cell model had not been previously used in the laboratory so it first required characterisation. Here insulin is shown to stimulate a transient increase of PtdIns5P in L6 myotubes, indicative of a signalling role in response to insulin. This project developed several tools to further investigate this potential role for PtdIns5P in the insulin response of myotubes. One such development was the successful overexpression of the PtdIns5P 4-kinase PIP4KIIalpha in these cells, which was able to abolish the insulin-stimulated PtdIns5P rise. This correlated with a loss of insulin-stimulated glucose uptake (upon PIP4KIIalpha expression). Interestingly, artificial elevation of PtdIns5P in L6 myotubes increases glucose uptake in the absence of stimulation. This phenomenon appears to result from the activation of PI3-kinase signalling, as it is abolished by the PI3-kinase inhibitor wortmannin, and involves activation of the PI3-kinase effector Akt. These results are consistent with the idea that insulin-stimulated PtdIns5P production contributes to the robust PI3-kinase/Akt activation necessary for insulin-stimulated glucose uptake in muscle.

Introdução: Embora estatinas sejam benéficas após o infarto agudo do miocárdio (IAM), pouco se sabe sobre seus efeitos quando usadas previamente ao evento. Objetivo: Avaliar o efeito do uso prévio de atorvastatina sobre a função cardiovascular, inflamação e GLUT4 no coração de ratos após IAM (oclusão artéria coronária). Métodos: Ratos Wistar-Kyoto, machos, foram tratados com atorvastatina (20mg/kg) ou veículo (gavagem), 14 dias antes do IAM ou cirurgia sham e avaliação ecocardiográfica 48h pós-IAM (Protocolo A) ou + 7 dias de atorvastatina após IAM e avaliação ecocardiográfica 7 dias pós-IAM (Protocolo B), divididos 16/grupo: C (sham+veículo), I (IAM+veículo), CAt (sham+atorvastatina) e IAt (IAM+atorvastatina). Foram avaliados parâmetros funcionais ecocardiográficos, marcadores inflamatórios plasmáticos e GLUT4 no coração (Western blot). Resultados: A área de infarto foi ~50% nos grupos I e IAt. No protocolo A, a fração de encurtamento foi ~60% maior no grupo IAt vs. I (C:50,9±3,9; CAt:47,9±4,0; I:20,7±3,4; IAt:33,4±3,5 %; p=0,036), o que não ocorreu no protocolo B. A fração de ejeção apresentou redução nos animais após IAM (Protocolo A: ~37%; B: ~30%) e a atorvastatina não melhorou este índice. Houve aumento de GLUT4 (miocárdio, membrana plasmática) pelo IAM 48h pós-IAM: C:35,7±6,0; CAt:32,2±10,9; I:49,8±9,8; IAt:54,1±6,3 UA/g tecido; p<0,001, sem benefício pela atorvastatina, e redução 7 dias pós-IAM: C:50,2±4,4; CAt:52,3±3,1; I:39,0±7,9; IAt:26,4±11,0 UA/g tecido; p<0,001, com prejuízo pela atorvastatina (redução de 32% na membrana plasmática). O IAM determinou aumento de marcadores inflamatórios no plasma, não revertido pelo uso de atorvastatina. Conclusão: Atorvastatina prévia ao IAM melhora a contratilidade no miocárdio precocemente independente do GLUT4 cardíaco, efeito que não foi mantido quando da avaliação mais tardia. / Background: Although statins are beneficial after acute myocardial infarction (AMI), its effects when used prior to this event remains unclear. Aim: To evaluate the effect of prior use of atorvastatin on cardiovascular function, inflammatory state and GLUT4 expression in the rat heart after myocardial infarction (coronary artery occlusion). Methods: Wistar-Kyoto male rats were treated with atorvastatin (20mg/kg) or vehicle (gavage), 14 days before the AMI or sham surgery, and echocardiographic evaluation 48 hours after AMI (protocol A) or atorvastatin + 7 days after AMI and echocardiography 7 days after AMI (Protocol B), allocated 16/grupo: C (sham + vehicle), I (AMI + vehicle), CAt (sham + atorvastatin) and IAt (AMI + atorvastatin). Functional echocardiographic parameters, plasma inflammatory markers and GLUT4 in the heart (Western blot) were measured. Results: Infarcted area was ~50% in groups I and IAt. In protocol A, left ventricular fractional shortening was ~60% higher in the IAt vs. I (C: 50.9 ± 3.9; CAt: 47.9 ± 4.0; I: 20.7 ± 3.4; IAt: 33.4 ± 3.5%, p=0.036), which not occur in protocol B. Ejection fraction was reduced in the animals after acute myocardial infarction (Protocol A: ~37%, B: ~30%) and atorvastatin did not improve this parameter. There was an increase of GLUT4 (plasma membrane) in the Protocol A (C: 35.7 ± 6.0; CAt: 32.2 ± 10.9, I: 49.8 ± 9.8; IAt: 54.1 ± 6.3 AU/g tissue, p<0.001) with no benefit by atorvastatin, and reduction in the Protocolo B (C: 50.2 ± 4.4; CAt: 52.3 ± 3.1; I: 39, 0 ± 7.9; IAt: 26.4 ± 11.0 AU/g tissue, p<0.001), damage by atorvastatin (32% reduction in the plasma membrane). The AMI resulted in an increase of inflammatory markers in plasma, not reversed by the use of atorvastatin. Conclusion: Atorvastatin prior to AMI improves myocardial contractility in early heart independent of GLUT4, an effect that was not maintained when evaluating later.

Orientador: Patricia Monteiro Seraphim / Banca: Marcelo Papoti / Banca: Solange Marta Franzói de Moraes / Resumo: Durante a obesidade ocorre aumento de ácidos graxos livres na circulação e, conseqüentemente aumento do conteúdo de proteínas com efeitos negativos na sinalização da insulina. Objetivo: Avaliar o efeito do treinamento aeróbio na modulação de RNAm de GLUT4, TNF-a e SOCS3 em tecidos musculares esqueléticos e a sensibilidade à insulina periférica de ratos obesos por dieta hiperlipídica. Métodos: Ratos obesos por dieta hiperlipídica foram submetidos ao protocolo de treinamento aeróbio. A sensibilidade à insulina e o conteúdo de RNAm de TNF-a, SOCS3 e GLUT4 foram comparadas entre os grupos: obesos sedentários (OS) e exercitados (OE), controles sedentários (CS) e exercitados (CE).Resultados: Os animais alimentados com dieta hiperlipídica apresentaram prejuízo da sensibilidade à insulina e aumento de RNAm de TNF-a e SOCS3. Mas o treinamento aeróbio ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: During obesity there is increase in free fatty acids circulation and consequently increase of the protein content with negative effects on insulin signaling. Objective: To evaluate the effect of aerobic training on modulation of GLUT4, TNF-a and SOCS3 mRNA in skeletal muscle tissue and peripheral insulin sensitivity in obese rats induced by high fat diet. Methods: Obese rats were subjected to an aerobic training protocol. Insulin sensitivity and TNF-a , SOCS3 and GLUT4 mRNA content were compared among the groups: obese sedentary (OS) and exercised (OE), sedentary controls (CS) and exercised (CE). Results: Obese group presented impaired insulin sensitivity and increased mRNA of TNF-a and SOCS3, while the aerobic training reversed all of these changes, especially in oxidative muscle. Conclusions: Aerobic ... (Complete abstract click electronic access below) / Mestre

Orientador: Patrícia Monteiro Seraphim / Banca: Ismael Forte Freitas Júnior / Banca: Cecília Edna Mareze da Costa / Resumo: A gravidez é um período de ajustes metabólicos e, quando associado ao tabagismo provoca alterações que trazem malefícios tanto à saúde materna quanto à saúde fetal. Assim, o estudo investigou o efeito da exposição à fumaça de cigarro sobre a expressão do transportador de glicose GLUT4 e parâmetros séricos e morfométricos de ratas prenhes e sua prole. Foram utilizadas ratas Wistar divididas em: CG- controle sacrificadas após a gestação, com prole adotada pelo grupo CL; CL - controle sacrificadas após o término da lactação; FG - expostas à fumaça de cigarro até o período gestacional e sacrificadas posteriormente, com prole adotada pelo grupo FL; FG - expostas à fumaça de cigarro até o fim da amamentação e posteriormente sacrificadas. As proles foram divididas por sexo e de acordo com a exposição ou não da rata à fumaça. Foram coletados sangue e tecidos para análise de glicemia e do conteúdo gênico e protéico de GLUT4. Nas ratas expostas à fumaça de cigarro, houve redução de peso corpóreo e de tecido adiposo, aumento da glicemia e modulação do transportador GLUT4 no músculo esquelético. Nas proles, houve... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pregnancy is a period of metabolic adjustments, and when associated with cigarette smoke causes changes both to maternal health as the fetal. The study has investigated the effect of cigarette smoke exposure on the expression of glucose transporter GLUT4 and morphometric parameters and serum of pregnant smoker rats and their offspring. Wistar rats were divided in: CG- nonsmokers sacrificed after pregnancy with offspring adopted by CL; CL - nonsmoker group sacrificed after the end of lactation; FG - smoker group sacrificed after pregnancy with offspring adopted by FL; FL - smoker sacrificed after the end of lactation. The offspring was divided by sex and according to the protocol of their mothers. Blood and tissue were collected for analysis of glucose and the content of GLUT4 gene and protein. In smoker mothers, body weight and adipose tissue were reduced, glucose level was increased, and GLUT4 expression was higher in skeletal muscle. In offspring... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:22:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-02Bitstream added on 2014-06-13T18:06:59Z : No. of bitstreams: 1 costa_acp_me_prud.pdf: 1159841 bytes, checksum: 03f044a1d82a9ea541e10e2423c0d059 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Durante a obesidade ocorre aumento de ácidos graxos livres na circulação e, conseqüentemente aumento do conteúdo de proteínas com efeitos negativos na sinalização da insulina. Objetivo: Avaliar o efeito do treinamento aeróbio na modulação de RNAm de GLUT4, TNF-a e SOCS3 em tecidos musculares esqueléticos e a sensibilidade à insulina periférica de ratos obesos por dieta hiperlipídica. Métodos: Ratos obesos por dieta hiperlipídica foram submetidos ao protocolo de treinamento aeróbio. A sensibilidade à insulina e o conteúdo de RNAm de TNF-a, SOCS3 e GLUT4 foram comparadas entre os grupos: obesos sedentários (OS) e exercitados (OE), controles sedentários (CS) e exercitados (CE).Resultados: Os animais alimentados com dieta hiperlipídica apresentaram prejuízo da sensibilidade à insulina e aumento de RNAm de TNF-a e SOCS3. Mas o treinamento aeróbio... / During obesity there is increase in free fatty acids circulation and consequently increase of the protein content with negative effects on insulin signaling. Objective: To evaluate the effect of aerobic training on modulation of GLUT4, TNF-a and SOCS3 mRNA in skeletal muscle tissue and peripheral insulin sensitivity in obese rats induced by high fat diet. Methods: Obese rats were subjected to an aerobic training protocol. Insulin sensitivity and TNF-a , SOCS3 and GLUT4 mRNA content were compared among the groups: obese sedentary (OS) and exercised (OE), sedentary controls (CS) and exercised (CE). Results: Obese group presented impaired insulin sensitivity and increased mRNA of TNF-a and SOCS3, while the aerobic training reversed all of these changes, especially in oxidative muscle. Conclusions: Aerobic ... (Complete abstract click electronic access below)

Introdução: Embora estatinas sejam benéficas após o infarto agudo do miocárdio (IAM), pouco se sabe sobre seus efeitos quando usadas previamente ao evento. Objetivo: Avaliar o efeito do uso prévio de atorvastatina sobre a função cardiovascular, inflamação e GLUT4 no coração de ratos após IAM (oclusão artéria coronária). Métodos: Ratos Wistar-Kyoto, machos, foram tratados com atorvastatina (20mg/kg) ou veículo (gavagem), 14 dias antes do IAM ou cirurgia sham e avaliação ecocardiográfica 48h pós-IAM (Protocolo A) ou + 7 dias de atorvastatina após IAM e avaliação ecocardiográfica 7 dias pós-IAM (Protocolo B), divididos 16/grupo: C (sham+veículo), I (IAM+veículo), CAt (sham+atorvastatina) e IAt (IAM+atorvastatina). Foram avaliados parâmetros funcionais ecocardiográficos, marcadores inflamatórios plasmáticos e GLUT4 no coração (Western blot). Resultados: A área de infarto foi ~50% nos grupos I e IAt. No protocolo A, a fração de encurtamento foi ~60% maior no grupo IAt vs. I (C:50,9±3,9; CAt:47,9±4,0; I:20,7±3,4; IAt:33,4±3,5 %; p=0,036), o que não ocorreu no protocolo B. A fração de ejeção apresentou redução nos animais após IAM (Protocolo A: ~37%; B: ~30%) e a atorvastatina não melhorou este índice. Houve aumento de GLUT4 (miocárdio, membrana plasmática) pelo IAM 48h pós-IAM: C:35,7±6,0; CAt:32,2±10,9; I:49,8±9,8; IAt:54,1±6,3 UA/g tecido; p<0,001, sem benefício pela atorvastatina, e redução 7 dias pós-IAM: C:50,2±4,4; CAt:52,3±3,1; I:39,0±7,9; IAt:26,4±11,0 UA/g tecido; p<0,001, com prejuízo pela atorvastatina (redução de 32% na membrana plasmática). O IAM determinou aumento de marcadores inflamatórios no plasma, não revertido pelo uso de atorvastatina. Conclusão: Atorvastatina prévia ao IAM melhora a contratilidade no miocárdio precocemente independente do GLUT4 cardíaco, efeito que não foi mantido quando da avaliação mais tardia. / Background: Although statins are beneficial after acute myocardial infarction (AMI), its effects when used prior to this event remains unclear. Aim: To evaluate the effect of prior use of atorvastatin on cardiovascular function, inflammatory state and GLUT4 expression in the rat heart after myocardial infarction (coronary artery occlusion). Methods: Wistar-Kyoto male rats were treated with atorvastatin (20mg/kg) or vehicle (gavage), 14 days before the AMI or sham surgery, and echocardiographic evaluation 48 hours after AMI (protocol A) or atorvastatin + 7 days after AMI and echocardiography 7 days after AMI (Protocol B), allocated 16/grupo: C (sham + vehicle), I (AMI + vehicle), CAt (sham + atorvastatin) and IAt (AMI + atorvastatin). Functional echocardiographic parameters, plasma inflammatory markers and GLUT4 in the heart (Western blot) were measured. Results: Infarcted area was ~50% in groups I and IAt. In protocol A, left ventricular fractional shortening was ~60% higher in the IAt vs. I (C: 50.9 ± 3.9; CAt: 47.9 ± 4.0; I: 20.7 ± 3.4; IAt: 33.4 ± 3.5%, p=0.036), which not occur in protocol B. Ejection fraction was reduced in the animals after acute myocardial infarction (Protocol A: ~37%, B: ~30%) and atorvastatin did not improve this parameter. There was an increase of GLUT4 (plasma membrane) in the Protocol A (C: 35.7 ± 6.0; CAt: 32.2 ± 10.9, I: 49.8 ± 9.8; IAt: 54.1 ± 6.3 AU/g tissue, p<0.001) with no benefit by atorvastatin, and reduction in the Protocolo B (C: 50.2 ± 4.4; CAt: 52.3 ± 3.1; I: 39, 0 ± 7.9; IAt: 26.4 ± 11.0 AU/g tissue, p<0.001), damage by atorvastatin (32% reduction in the plasma membrane). The AMI resulted in an increase of inflammatory markers in plasma, not reversed by the use of atorvastatin. Conclusion: Atorvastatin prior to AMI improves myocardial contractility in early heart independent of GLUT4, an effect that was not maintained when evaluating later.

Introdução: Embora estatinas sejam benéficas após o infarto agudo do miocárdio (IAM), pouco se sabe sobre seus efeitos quando usadas previamente ao evento. Objetivo: Avaliar o efeito do uso prévio de atorvastatina sobre a função cardiovascular, inflamação e GLUT4 no coração de ratos após IAM (oclusão artéria coronária). Métodos: Ratos Wistar-Kyoto, machos, foram tratados com atorvastatina (20mg/kg) ou veículo (gavagem), 14 dias antes do IAM ou cirurgia sham e avaliação ecocardiográfica 48h pós-IAM (Protocolo A) ou + 7 dias de atorvastatina após IAM e avaliação ecocardiográfica 7 dias pós-IAM (Protocolo B), divididos 16/grupo: C (sham+veículo), I (IAM+veículo), CAt (sham+atorvastatina) e IAt (IAM+atorvastatina). Foram avaliados parâmetros funcionais ecocardiográficos, marcadores inflamatórios plasmáticos e GLUT4 no coração (Western blot). Resultados: A área de infarto foi ~50% nos grupos I e IAt. No protocolo A, a fração de encurtamento foi ~60% maior no grupo IAt vs. I (C:50,9±3,9; CAt:47,9±4,0; I:20,7±3,4; IAt:33,4±3,5 %; p=0,036), o que não ocorreu no protocolo B. A fração de ejeção apresentou redução nos animais após IAM (Protocolo A: ~37%; B: ~30%) e a atorvastatina não melhorou este índice. Houve aumento de GLUT4 (miocárdio, membrana plasmática) pelo IAM 48h pós-IAM: C:35,7±6,0; CAt:32,2±10,9; I:49,8±9,8; IAt:54,1±6,3 UA/g tecido; p<0,001, sem benefício pela atorvastatina, e redução 7 dias pós-IAM: C:50,2±4,4; CAt:52,3±3,1; I:39,0±7,9; IAt:26,4±11,0 UA/g tecido; p<0,001, com prejuízo pela atorvastatina (redução de 32% na membrana plasmática). O IAM determinou aumento de marcadores inflamatórios no plasma, não revertido pelo uso de atorvastatina. Conclusão: Atorvastatina prévia ao IAM melhora a contratilidade no miocárdio precocemente independente do GLUT4 cardíaco, efeito que não foi mantido quando da avaliação mais tardia. / Background: Although statins are beneficial after acute myocardial infarction (AMI), its effects when used prior to this event remains unclear. Aim: To evaluate the effect of prior use of atorvastatin on cardiovascular function, inflammatory state and GLUT4 expression in the rat heart after myocardial infarction (coronary artery occlusion). Methods: Wistar-Kyoto male rats were treated with atorvastatin (20mg/kg) or vehicle (gavage), 14 days before the AMI or sham surgery, and echocardiographic evaluation 48 hours after AMI (protocol A) or atorvastatin + 7 days after AMI and echocardiography 7 days after AMI (Protocol B), allocated 16/grupo: C (sham + vehicle), I (AMI + vehicle), CAt (sham + atorvastatin) and IAt (AMI + atorvastatin). Functional echocardiographic parameters, plasma inflammatory markers and GLUT4 in the heart (Western blot) were measured. Results: Infarcted area was ~50% in groups I and IAt. In protocol A, left ventricular fractional shortening was ~60% higher in the IAt vs. I (C: 50.9 ± 3.9; CAt: 47.9 ± 4.0; I: 20.7 ± 3.4; IAt: 33.4 ± 3.5%, p=0.036), which not occur in protocol B. Ejection fraction was reduced in the animals after acute myocardial infarction (Protocol A: ~37%, B: ~30%) and atorvastatin did not improve this parameter. There was an increase of GLUT4 (plasma membrane) in the Protocol A (C: 35.7 ± 6.0; CAt: 32.2 ± 10.9, I: 49.8 ± 9.8; IAt: 54.1 ± 6.3 AU/g tissue, p<0.001) with no benefit by atorvastatin, and reduction in the Protocolo B (C: 50.2 ± 4.4; CAt: 52.3 ± 3.1; I: 39, 0 ± 7.9; IAt: 26.4 ± 11.0 AU/g tissue, p<0.001), damage by atorvastatin (32% reduction in the plasma membrane). The AMI resulted in an increase of inflammatory markers in plasma, not reversed by the use of atorvastatin. Conclusion: Atorvastatin prior to AMI improves myocardial contractility in early heart independent of GLUT4, an effect that was not maintained when evaluating later.

No description available.