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Open Access Original investigation

GLUT4 content decreases along with insulin resistance and high levels of inflammatory markers in rats with metabolic syndrome

Natalia M Leguisamo1, Alexandre M Lehnen1, Ubiratan F Machado2, Maristela M Okamoto2, Melissa M Markoski1, Graziela H Pinto1 and Beatriz D Schaan13*

Author Affiliations

1 Laboratório de Experimentação Animal e Laboratório de Cardiologia Molecular e Celular, Instituto de Cardiologia/Fundação, Universitária de Cardiologia, Av. Princesa Isabel, 395. Bairro Santana, Porto Alegre, RS, 90620 001, Brazil

2 Departamento de Fisiologia e Biofísica do Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil

3 Serviço de Endocrinologia, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

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Cardiovascular Diabetology 2012, 11:100  doi:10.1186/1475-2840-11-100

Published: 16 August 2012

Abstract

Background

Metabolic syndrome is characterized by insulin resistance, which is closely related to GLUT4 content in insulin-sensitive tissues. Thus, we evaluated the GLUT4 expression, insulin resistance and inflammation, characteristics of the metabolic syndrome, in an experimental model.

Methods

Spontaneously hypertensive neonate rats (18/group) were treated with monosodium glutamate (MetS) during 9 days, and compared with Wistar-Kyoto (C) and saline-treated SHR (H). Blood pressure (BP) and lipid levels, C-reactive protein (CRP), interleukin 6 (IL-6), TNF-α and adiponectin were evaluated. GLUT4 protein was analysed in the heart, white adipose tissue and gastrocnemius. Studies were performed at 3 (3-mo), 6 (6-mo) and 9 (9-mo) months of age.

Results

MetS rats were more insulin resistant (p<0.001, all ages) and had higher BP (3-mo: p<0.001, 6-mo: p = 0.001, 9-mo: p = 0.015) as compared to C. At 6 months, CRP, IL-6 and TNF-α were higher (p<0.001, all comparisons) in MetS rats vs H, but adiponectin was lower in MetS at 9 months (MetS: 32 ± 2, H: 42 ± 2, C: 45 ± 2 pg/mL; p<0.001). GLUT4 protein was reduced in MetS as compared to C rats at 3, 6 and 9-mo, respectively (Heart: 54%, 50% and 57%; Gastrocnemius: 37%, 56% and 50%; Adipose tissue: 69%, 61% and 69%).

Conclusions

MSG-treated SHR presented all metabolic syndrome characteristics, as well as reduced GLUT4 content, which must play a key role in the impaired glycemic homeostasis of the metabolic syndrome.

Keywords:
Monosodium glutamate; Spontaneously hypertensive rats; Glucose transporter 4