title: Genetic obesity alters recruitment of TANK-binding kinase 1 and AKT into hypothalamic lipid rafts domains.
abstract: Lipid rafts (LRs) are membrane subdomains enriched in cholesterol, glycosphingolipids and sphingolipids containing saturated fatty acid. Signaling proteins become concentrated in these microdomains mainly by saturated fatty acid modification, thus facilitating formation of protein complexes and activation of specific signaling pathways. High intake of saturated fatty acids promotes inflammation and insulin resistance, in part by disrupting insulin signaling pathway. Here we investigate whether lipid-induced toxicity in obesity correlates with altered composition of insulin signaling proteins in LRs in the brain. Our results showed that insulin receptor (IR) is highly concentrated in LRs fraction in comparison with soluble or postsynaptic density (PSD) fractions. Analysis of LRs domains from hippocampus of obese mouse showed a significant decrease of IR and its downstream signaling protein AKT, while in the PSD fraction we detected partial decrease of AKT and no changes in the IR concentration. No changes were shown in the soluble extract. In hypothalamus, genetic obesity also decreases interaction of AKT, but we did not detect changes in the IR distribution. However, in this structure genetic obesity increases recruitment of the IR negative regulator TANK-binding kinase 1 (TBK1) into LRs and PSD fraction. No changes of AKT, IR and TBK1 were found in soluble fractions of obese in comparison with lean mice. In vitro studies showed that incubation with saturated palmitic acid but not with unsaturated docosahexaenoic acid (DHA) or palmitoleic acid decreases association of IR and AKT and increases TBK1 recruitment into LRs and PSD domains, emulating what happens in the obese mice. TBK1 recruitment to insoluble domains correlates with decreases of IR tyrosine phosphorylation and ser473 AKT phosphorylation, markers of insulin resistance. These data support the hypothesis that hyperlipidemia associated with genetic obesity alters targeting of TBK1 and insulin signaling proteins into insoluble LRs domains.
authors.affiliation: Departamento de Farmacologia, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico; Centro de Investigación y Desarrollo en Ciencias de la Salud, Universidad Autonoma de Nuevo Leon, Monterrey, Mexico. Electronic address: ilsedelint@hotmail.com.
authors.forename: Ilse
authors.initials: I
authors.lastname: Delint-Ramirez
authors.affiliation: Centro de Investigación y Desarrollo en Ciencias de la Salud, Universidad Autonoma de Nuevo Leon, Monterrey, Mexico; Departamento de Bioquímica, Universidad Autónoma de Nuevo León, Monterrey, Mexico.
authors.forename: Roger
authors.initials: R
authors.lastname: Maldonado Ruiz
authors.affiliation: Departamento Fisiología de la Nutrición, Instituto Nacional de Ciencias Medicas y Nutrición, Mexico.
authors.forename: Ivan
authors.initials: I
authors.lastname: Torre-Villalvazo
authors.affiliation: Departamento de Bioquímica, Universidad Autónoma de Nuevo León, Monterrey, Mexico; Gene Therapy Unit, Centro de Investigación y Desarrollo en Ciencias de la Salud, Universidad Autonoma de Nuevo Leon, Monterrey, Mexico.
authors.forename: Lizeth
authors.initials: L
authors.lastname: Fuentes-Mera
authors.affiliation: Departamento de Farmacologia, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Garza Ocañas
authors.affiliation: Departamento Fisiología de la Nutrición, Instituto Nacional de Ciencias Medicas y Nutrición, Mexico.
authors.forename: Armando
authors.initials: A
authors.lastname: Tovar
authors.affiliation: Centro de Investigación y Desarrollo en Ciencias de la Salud, Universidad Autonoma de Nuevo Leon, Monterrey, Mexico; Departamento de Bioquímica, Universidad Autónoma de Nuevo León, Monterrey, Mexico. Electronic address: acm590@hotmail.com.
authors.forename: Alberto
authors.initials: A
authors.lastname: Camacho
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D007031:Hypothalamus / Q000166:cytology / Q000201:enzymology*; D021962:Membrane Microdomains / Q000201:enzymology*; D051379:Mice; D008820:Mice, Obese; D009765:Obesity / Q000201:enzymology* / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*
chemical_list: C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: AKT; Hypothalamus and lipotoxicity; Insulin receptor; Insulin resistance; Obesity; TBK1