title: Hyperinsulinemia induces insulin resistance on glucose and lipid metabolism in a human adipocytic cell line: paracrine interaction with myocytes.
abstract: BACKGROUND
  Adipocytes release a variety of factors which deregulation could provide the basis for complications such as insulin resistance, an early defect on the onset of type 2 diabetes. Such insulin resistance can initially be overcome by compensatory hyperinsulinemia, but the prolonged presence of the hormone can be detrimental for insulin sensitivity.
  
  
  OBJECTIVE
  The objective of the study was to dissect the molecular mechanisms that may regulate hyperinsulinemia-induced insulin resistance in a human liposarcoma cell line and its paracrine interactions with a human rhabdomyosarcoma cell line.
  
  
  METHODS
  We studied glucose uptake, lipolysis, insulin signaling, and secretion pattern at different days of adipocyte differentiation in the presence of insulin.
  
  
  RESULTS
  Adipocytes differentiated for 14 d gain insulin sensitivity on glucose uptake and inhibition of lipolysis, but prolonged cultures develop an insulin-resistant state characterized by an increase in phosphatase and tensin homolog-deleted on chromosome 10 expression and defects in insulin signaling at the insulin receptor substrate-1/AKT level. The secretion pattern of nonesterified fatty acids, IL-6, adiponectin, leptin, and monocyte chemotactic protein-1 was in keeping with the changes in insulin sensitivity during differentiation. An inverse biphasic response was also observed in human myocytes when they were cultured with various adipocyte-conditioned media, although insulin resistance was detected earlier than in adipocytes. This behavior mimics hyperinsulinemia because insulin action was restored when adipocytes were cultured in the absence of the hormone. Pharmacological treatment of adipocytes with a liver X receptor agonist reestablishes insulin-stimulated glucose uptake, whereas treatment with a peroxisome proliferator-activated receptor-gamma agonist restored the antilipolytic action of insulin.
  
  
  CONCLUSIONS
  Hyperinsulinemia deregulates adipocyte secretion pattern, producing insulin resistance in adipocytes and myocytes, a situation that can be ameliorated with nuclear receptor agonists.
authors.affiliation: Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, Complutense University, 28040 Madrid, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Fernández-Veledo
authors.forename: Iria
authors.initials: I
authors.lastname: Nieto-Vazquez
authors.forename: Javier
authors.initials: J
authors.lastname: de Castro
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Ramos
authors.forename: Silke
authors.initials: S
authors.lastname: Brüderlein
authors.forename: Peter
authors.initials: P
authors.lastname: Möller
authors.forename: Margarita
authors.initials: M
authors.lastname: Lorenzo
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006845:Hydrocarbons, Fluorinated; D006946:Hyperinsulinism / Q000378:metabolism*; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000378:metabolism; D050356:Lipid Metabolism; D000071518:Liver X Receptors; D032342:Muscle Cells / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
chemical_list: D018932:Chemokine CCL2; D004268:DNA-Binding Proteins; D005230:Fatty Acids, Nonesterified; D005947:Glucose; D006845:Hydrocarbons, Fluorinated; D015850:Interleukin-6; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D013449:Sulfonamides; C111835:CCL2 protein, human; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides