title: Essential Role of IGFIR in the Onset of Male Brown Fat Thermogenic Function: Regulation of Glucose Homeostasis by Differential Organ-Specific Insulin Sensitivity.
abstract: Brown fat is a thermogenic tissue that generates heat to maintain body temperature in cold environments and dissipate excess energy in response to overfeeding. We have addressed the role of the IGFIR in the brown fat development and function. Mice lacking IGFIR exhibited normal brown adipose tissue/body weight in knockout (KO) vs control mice. However, lack of IGFIR decreased uncoupling protein 1 expression in interscapular brown fat and beige cells in inguinal fat. More importantly, the lack of IGFIR resulted in an impaired cold acclimation. No differences in the total fat volume were found in the KO vs control mice. Epididymal fat showed larger adipocytes but with a lower number of adipocytes in KO vs control mice at age 12 months. In addition, KO mice showed a sustained moderate hyperinsulinemia and hypertriglyceridemia upon time and hepatic insulin insensitivity associated with lipid accumulation, with the outcome of a global insulin resistance. In addition, we found that the expression of uncoupling protein 3 in the skeletal muscle was decreased and its expression was increased in the heart in parallel with the expression of beta-2 adrenergic receptors. Upon nonobesogenic high-fat diet, we found a severe insulin resistance in the liver and in the skeletal muscle, but unchanged insulin sensitivity in the heart. In conclusion, our data suggest that IGFIR it is not an essential growth factor in the brown fat development in the presence of the IR and very high plasma levels of IGF-I, but it is indispensable for full brown fat functionality.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Vanesa
authors.initials: V
authors.lastname: Viana-Huete
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Carlos
authors.initials: C
authors.lastname: Guillén
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Ana
authors.initials: A
authors.lastname: García-Aguilar
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Gema
authors.initials: G
authors.lastname: García
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Silvia
authors.initials: S
authors.lastname: Fernández
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: C R
authors.initials: CR
authors.lastname: Kahn
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Complutense University-Madrid, Madrid 28040, Spain; Spanish Diabetes and Metabolic Research Network (V.V.-H., C.G., A.G.-A., G.G., S.F., M.B.), Institute of Health Carlos III, Madrid 28029, Spain; and Joslin Diabetes Center (C.R.K.), Harvard Medical School, Boston, MA 02215.
authors.forename: Manuel
authors.initials: M
authors.lastname: Benito
mesh_terms: D000064:Acclimatization; D017667:Adipocytes / Q000378:metabolism; D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D003080:Cold Temperature; D004822:Epididymis / Q000378:metabolism; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D006706:Homeostasis; D006946:Hyperinsulinism / Q000235:genetics; D015228:Hypertriglyceridemia / Q000235:genetics; D007333:Insulin Resistance; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009928:Organ Specificity; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022722:Thermogenesis
chemical_list: C519530:insulin-like growth factor-1, mouse; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D005947:Glucose