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Previous issue date: 2009-07-31 / Financiadora de Estudos e Projetos / Myostatin (MSTN) is a secreted growth factor expressed in skeletal muscle and negatively regulates skeletal muscle mass. MSTN is also expressed in adipose tissue. Recent data suggest that MSTN regulates adipogenesis and energy metabolism. Aims: The objective of this study was to determine the influence of exercise in the expression of myostatin (MSTN) and its receptor in fat and muscle in obese and insulin resistant rats. Methods: Adult male Wistar rats were housed under controlled conditions (20-220 C, 10-14h light-dark cycle) and were allowed free access to standard rodent chow (control group, CG) or HF diet (58% Kcal from fat, high-fat group, HG) during 12 weeks. Glucose tolerance test (GTT) and insulin tolerance test (ITT) were performed
before and at 3, 4, 8 and 12 weeks after diet regimen. After 12 weeks, CG and HG rats were randomly assigned to a swimming training group (CGE and HGE) or a sedentary group (CGS and HGS). CGE and HE swam individually in water tanks (50x30cm) at 340 C, for 45 minutes at 0900h and 1700h, 5 day week-1, for 4 weeks. After this period, rats were submitted again to GTT and ITT and then killed by decapitation. GTT area under the curve was lower in HE compared to HGS. White gastrocnemius muscle and fat pads were dissected, weighted, immediately cooled in liquid nitrogen and stored at - 700 C for subsequent analysis. The mRNA levels were quantified by real time RT-PCR. The animals were maintained according to the local University Committee guidelines for the care and use of laboratory animals. Results: HG developed insulin resistance according to GTT and ITT tests. Adipose fat pads (epididymal, retropritoneal and mesenteric) were 2 to 3 times heavier in high-fat fed groups (HGS and HGE) compared to standard chow fed groups (CGS and CGE). In HGS, the expression of MSTN was significantly higher in mesenteric fat and lower in epididymal fat and Brown tissue adipose (BAT) compared to CGS rats. The expression of ActRIIB significantly decreased in epididymal fat and BAT. The training resulted in decreased of expression of expression of MSTN in muscle and mesenteric fat and increased expression in BAT of CGE compared CGS. The expression of ActRIIB increased significantly in mesenteric fat and BAT in CGE compared to CGS. The expression of MSTN decreased in mesenteric fat and increased in epididymal fat and BAT in HGE compared to HGS. The expression of ActRIIB decreased in muscle and mesenteric fat and increased in BAT in HGE compared to HGS. Conclusions: These data suggest that the expression of MSTN in fat tissues may be involved in the metabolic response of rats submitted to high fat diet and exercise. / Miostatina (MSTN) é um fator de crescimento expresso e secretado pelo músculo esquelético que regula negativamente a massa muscular. MSTN é também expressa no tecido adiposo em menores quantidades. Dados recentes sugerem que a MSTN regula a adipogênese e o metabolismo energético. Objetivo: Verificar o efeito da dieta hiperlipídica e exercício na expressão da MSTN e de seu receptor (ActRIIB) no músculo esquelético e tecido adiposo na obesidade dietética e resistência insulínica. Métodos: Ratos Wistar adultos realizaram testes de tolerância à glicose (TTG) e
tolerância à insulina (TTI) antes e após 3, 4, 8 e 12 semanas sob alimentação com dieta padrão (Grupo Controle, GC) ou dieta hiperlipídica (Grupo dieta hiperlipídica, GH). Após 12 semanas, os ratos dos GC e GH foram, aleatoriamente, separados nos grupos Controle Exercício (GCE), Dieta Hiperlipídica Exercício (GHE), Controle Sedentário (GCS) e Dieta Hiperlipídica Sedentário (GHS). GCE e GHE nadaram em tanques individuais (50 x 30cm) a 34ºC, por 45 minutos, às 9h e 17h, 5 dias semana, durante 4 semanas. Após esse período, os ratos foram submetidos à TTG e sacrificados por decapitação. Músculo Gastrocnêmio e tecido adiposo foram dissecados, pesados, imediatamente congelados e estocados a -80ºC. O RNAm da MSTN e ActRIIB foi quantificado por RT-PCR. Resultados: GH desenvolveu resistência insulínica de acordo com TTG e TTI. O treinamento aumentou a sensibilidade à insulina no GHE. No GHS, a expressão de MSTN foi significativamente maior na gordura mesentérica e menor na
gordura epididimal e tecido adiposo marrom (TAM) comparado ao GCS. A expressão de ActRIIB diminuiu significativamente na gordura epididimal e TAM do GHS comparada ao GCS. O treinamento resultou em redução significativa da expressão de
MSTN no músculo e gordura mesentérica e aumento no TAM do GCE comparado ao GCS. A expressão de ActRIIB diminuiu significativamente na gordura mesentérica e TAM no GCE comparado ao GCS. A expressão de MSTN diminuiu na gordura
mesentérica e aumentou na gordura epididimal e TAM no GHE comparada ao GHS. A expressão de ActRIIB diminuiu no músculo e gordura mesentérica e aumentou no TAM no GHE comparado ao GHS. Conclusão: Esses dados sugerem que a expressão de MST e ActRIIB no tecido adiposo pode estar envolvida na resposta metabólica de ratos submetidos à dieta hiperlipídica e exercício.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufscar.br:ufscar/1312 |
| Date | 31 July 2009 |
| Creators | Bueno, Patricia de Godoy |
| Contributors | Leal, Ângela Merice de Oliveira |
| Publisher | Universidade Federal de São Carlos, Programa de Pós-graduação em Ciências Fisiológicas, UFSCar, BR |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFSCAR, instname:Universidade Federal de São Carlos, instacron:UFSCAR |
| Rights | info:eu-repo/semantics/openAccess |
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