title: Leptin reduces the expression and increases the phosphorylation of the negative regulators of GLUT4 traffic TBC1D1 and TBC1D4 in muscle of ob/ob mice.
abstract: Leptin improves insulin sensitivity in skeletal muscle. Our goal was to determine whether proteins controlling GLUT4 traffic are altered by leptin deficiency and in vivo leptin administration in skeletal muscle of wild type and ob/ob mice. Leptin-deficient ob/ob mice were divided in three groups: control, leptin-treated (1 mg/kg/d) and leptin pair-fed ob/ob mice. Microarray analysis revealed that 1,546 and 1,127 genes were regulated by leptin deficiency and leptin treatment, respectively. Among these, we identified 24 genes involved in intracellular vesicle-mediated transport in ob/ob mice. TBC1 domain family, member 1 (Tbc1d1), a negative regulator of GLUT4 translocation, was up-regulated (P = 0.001) in ob/ob mice as compared to wild types. Importantly, leptin treatment reduced the transcript levels of Tbc1d1 (P<0.001) and Tbc1d4 (P = 0.004) in the leptin-treated ob/ob as compared to pair-fed ob/ob animals. In addition, phosphorylation levels of TBC1D1 and TBC1D4 were enhanced in leptin-treated ob/ob as compared to control ob/ob (P = 0.015 and P = 0.023, respectively) and pair-fed ob/ob (P = 0.036 and P = 0.034, respectively) mice. Despite similar GLUT4 protein expression in wild type and ob/ob groups a different immunolocalization of this protein was evidenced in muscle sections. Leptin treatment increased GLUT4 immunoreactivity in gastrocnemius and extensor digitorum longus sections of leptin-treated ob/ob mice. Moreover, GLUT4 protein detected in immunoprecipitates from TBC1D4 was reduced by leptin replacement compared to control ob/ob (P = 0.013) and pair-fed ob/ob (P = 0.037) mice. Our findings suggest that leptin enhances the intracellular GLUT4 transport in skeletal muscle of ob/ob animals by reducing the expression and activity of the negative regulators of GLUT4 traffic TBC1D1 and TBC1D4.
authors.affiliation: Metabolic Research Laboratory, Universidad de Navarra, Pamplona, Spain.
authors.forename: Neira
authors.initials: N
authors.lastname: Sáinz
authors.forename: Amaia
authors.initials: A
authors.lastname: Rodríguez
authors.forename: Victoria
authors.initials: V
authors.lastname: Catalán
authors.forename: Sara
authors.initials: S
authors.lastname: Becerril
authors.forename: Beatriz
authors.initials: B
authors.lastname: Ramírez
authors.forename: Andoni
authors.initials: A
authors.lastname: Lancha
authors.forename: Emma
authors.initials: E
authors.lastname: Burgos-Ramos
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez-Ambrosi
authors.forename: Gema
authors.initials: G
authors.lastname: Frühbeck
mesh_terms: D000818:Animals; D020690:GTPase-Activating Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D055442:Metabolome / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics
chemical_list: D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D020738:Leptin; D009687:Nuclear Proteins; C495693:Slc2a4 protein, mouse; C095906:Tbc1d1 protein, mouse; C505647:Tbc1d4 protein, mouse