Role of ABCA1 on membrane cholesterol content,insulin-dependent Akt phosphorylation and glucose uptake in adult skeletal muscle fibers from mice |
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Authors: | Pablo Sánchez-Aguilera Alexis Diaz-Vegas Cristián Campos Oscar Quinteros-Waltemath Hugo Cerda-Kohler Genaro Barrientos Ariel Contreras-Ferrat Paola Llanos |
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Institution: | 1. Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Chile;2. Departamento Ciencias Biológicas, Facultad Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile;3. CEMC, Facultad de Medicina, Universidad de Chile, Chile;4. ACCDiS, Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina, Universidad de Chile, Chile |
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Abstract: | The ATP-binding cassette transporter A1 (ABCA1) promotes cellular cholesterol efflux, leading to cholesterol binding to the extracellular lipid-free apolipoprotein A-I. ABCA1 regulates lipid content, glucose tolerance and insulin sensitivity in adipose tissue. In skeletal muscle, most GLUT4-mediated glucose transport occurs in the transverse tubule, a system composed by specialized cholesterol-enriched invaginations of the plasma membrane. We have reported that insulin resistant mice have higher cholesterol levels in transverse tubule from adult skeletal muscle. These high levels correlate with decreased GLUT4 trafficking and glucose uptake; however, the role of ABCA1 on skeletal muscle insulin-dependent glucose metabolism remains largely unexplored. Here, we evaluated the functional role of the ABCA1 on insulin-dependent signaling pathways, glucose uptake and cellular cholesterol content in adult skeletal muscle. Male mice were fed for 8?weeks with normal chow diet (NCD) or high fat diet (HFD). Compared to NCD-fed mice, ABCA1 mRNA levels and protein content were lower in muscle homogenates from HFD-fed mice. In Flexor digitorum brevis muscle from NCD-fed mice, shABCA1-RFP in vivo electroporation resulted in 65% reduction of ABCA1 protein content, 1.6-fold increased fiber cholesterol levels, 74% reduction in insulin-dependent Akt (Ser473) phosphorylation, total suppression of insulin-dependent GLUT4 translocation and decreased 2-NBDG uptake compared to fibers electroporated with the scrambled plasmid. Pre-incubation with methyl-β cyclodextrin reestablished both GLUT4 translocation and 2-NBDG transport. Based on the present results, we suggest that decreased ABCA1 contributes to the anomalous cholesterol accumulation and decreased glucose transport displayed by skeletal muscle membranes in the insulin resistant condition. |
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Keywords: | 2-NBDG ABCA1 ATP binding cassette transporter A1 AMPK AMP-activated protein kinase DHPR Dihydropyridine receptor DMII Diabetes mellitus type II FDB Flexor digitorum brevis GLUT4 Glucose transporter type 4 HFD High fat diet IR Insulin resistance MβCD Methyl-β-cyclodextrin NCD Normal chow diet shABCA1-RFP Small hairpin RNA against ABCA1 plus red fluorescence protein encoded construct GLUT4 Transverse-tubule system High fat diet Insulin resistance Cholesterol efflux |
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