S Crochet, E Godet, C Berri, S Métayer-Coustard, S Tesseraud, E Cailleau-Audouin, E Coudert, A Collin, T Bordeau, J Dupont, C Praud
Glucose transport into cells is the first limiting step for the regulation of glucose homeostasis. In mammals, it is mediated by a family of facilitative glucose transporters (GLUTs) (encoded by SLC2A* genes), with a constitutive role (GLUT1), or insulin-sensitive transporters (GLUT4, GLUT8 and GLUT12). Compared to mammals, the chicken shows high levels of glycaemia and relative insensitivity to exogenous insulin. To date, only GLUT1, -8 and -12 have been described in chicken skeletal muscles but not fully characterized, whereas GLUT4 was reported as lacking. The aim of the present study was to determine the changes in the expression of the SLC2A1, SLC2A8 and SLC2A12 genes, encoding GLUT1, -8 and -12 proteins respectively, during ontogenesis and how the respective expression of these three genes is affected by the muscle type and the nutritional or insulin status of the bird (fed, fasted or insulin immuno-neutralized). SLC2A1 was mostly expressed in the glycolytic pectoralis major muscle during embryogenesis and 5 days post-hatching while SLC2A8 was mainly expressed at hatching. SLC2A12 expression increased regularly from 12 days in ovo up to 5 days post-hatching. In the mixed-type sartorius muscle, the expression of SLC2A1 and SLC2A8 remained unchanged while that of SLC2A12 was gradually increased during early muscle development. The expression of SLC2A1 and SLC2A8 was greater in oxidative and oxido-glycolytic muscles than in glycolytic muscles. The expression of SLC2A12 differed considerably between muscles but not necessarily in relation to muscle contractile or metabolic type. The expression of SLC2A1, SLC2A8 and SLC2A12 was reduced by fasting and insulin immuno-neutralization in the pectoralis major muscle, while in the leg muscles only SLC2A12 was impaired by insulin immuno-neutralization. Our findings clearly indicate differential regulation of the expression of three major glucose transporters in skeletal muscles, with some type-related features. They provide new insights to improve the understanding of the fine regulation of glucose utilization in chicken muscles.
