title: Adiponectin deletion impairs insulin signaling in insulin-sensitive but not insulin-resistant 3T3-L1 adipocytes.
abstract: OBJECTIVE
  Previous reports have demonstrated that the adipocyte-derived peptide adiponectin is closely associated with insulin resistance due to its insulin-sensitizing and anti-inflammatory properties in peripheral tissues; however the autocrine effects of adiponectin remain elusive. This study investigated regulatory effects of adiponectin on glucose transport and insulin signaling in insulin-sensitive or insulin-resistant 3T3-L1 adipocytes.
  
  
  METHODS
  3T3-L1 fibroblasts were transfected with non-target or adiponectin (ADN) siRNA and differentiated. Chronic treatment with insulin (24h, 100 nM) was employed to induce insulin resistance in differentiated adipocytes. Insulin-stimulated glucose transport was measured and protein and mRNA levels were assessed by Western blot and RT-PCR.
  
  
  RESULTS
  Prolonged incubation with insulin significantly reduced insulin-stimulated glucose uptake, suggesting the development of insulin resistance and adiponectin mRNA expression. In this insulin-resistant condition, adiponectin deletion did not alter insulin-stimulated glucose uptake. In insulin-sensitive adipocytes, adiponectin ablation reduced insulin-stimulated glucose uptake, expression of IRS-1 and GLUT4, and GLUT4 translocation to the membrane. Adiponectin knockdown did not affect the activation of AKT and p38MAPK (phosphorylation form/total form), but significantly decreased the activation of AMPK in insulin-responsive adipocytes.
  
  
  CONCLUSIONS
  Adiponectin deficiency suppresses insulin-induced glucose uptake, insulin signaling, and the AMPK pathway only in insulin-responsive 3T3-L1 adipocytes.
authors.affiliation: Department of Nutritional Science and Food Management, Ewha Womans University, Seoul, Republic of Korea.
authors.forename: Eugene
authors.initials: E
authors.lastname: Chang
authors.affiliation: Diabetes Research Institute, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Jung Mook
authors.initials: JM
authors.lastname: Choi
authors.affiliation: Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Se Eun
authors.initials: SE
authors.lastname: Park
authors.affiliation: Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Rhee
authors.affiliation: Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Won-Young
authors.initials: WY
authors.lastname: Lee
authors.affiliation: Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Oh
authors.affiliation: Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Park
authors.affiliation: Diabetes Research Institute, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea; Division of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: cydoctor@chol.com.
authors.forename: Cheol-Young
authors.initials: CY
authors.lastname: Park
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D052242:Adiponectin / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D017931:DNA Primers / Q000235:genetics; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D051379:Mice; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D052242:Adiponectin; D017931:DNA Primers; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C495693:Slc2a4 protein, mouse; D005947:Glucose
keywords: Adipocytes; Adiponectin; Insulin resistance; Insulin signaling