title: GLUT-4 expression is not consistently higher in type-1 than in type-2 fibres of rat and human vastus lateralis muscles; an immunohistochemical study.
abstract: In whole muscle homogenates, the glucose transporter-4 (GLUT-4) content is reported to be higher in muscles consisting predominantly of oxidative (type-1) muscle fibres than in muscles consisting predominantly of glycolytic (type-2) fibres. From these findings, it has been deduced that in rat muscle, oxidative fibres have an intrinsically higher level of GLUT-4 protein than glycolytic fibres. No data is available concerning human muscle. Moreover, the fibre-type-specific expression of GLUT-4 has not yet been examined directly. In this study, the relative abundance of GLUT-4 protein expression in individual fibres of different types within a muscle was compared directly in immunohistochemical assays. The human vastus lateralis muscle and a selection of rat muscles were studied using a novel GLUT-4 antiserum. It is concluded that the pattern of fibre-type-specific GLUT-4 expression differs between human and rats and varies between the different muscles studied, indicating that non-fibre-type-specific factor(s) affect expression of GLUT-4. The observation that within a muscle a fibre-type-specific expression of GLUT-4 was observed indicates that fibre-type-specific factors contribute to GLUT-4 expression as well. Thus, it can be postulated that both fibre-type-dependent and fibre-type-independent factors affect GLUT-4 expression.
authors.affiliation: Department of Movement Sciences, Maastricht University, The Netherlands.
authors.forename: L B
authors.initials: LB
authors.lastname: Borghouts
authors.forename: G
authors.initials: G
authors.lastname: Schaart
authors.forename: M K
authors.initials: MK
authors.lastname: Hesselink
authors.forename: H A
authors.initials: HA
authors.lastname: Keizer
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D051275:Glucose Transporter Type 4; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000737:chemistry*; D009218:Myosins / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
chemical_list: D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; C495694:Slc2a4 protein, rat; D009218:Myosins