title: Time-resolved and tissue-specific systems analysis of the pathogenesis of insulin resistance.
abstract: BACKGROUND
  The sequence of events leading to the development of insulin resistance (IR) as well as the underlying pathophysiological mechanisms are incompletely understood. As reductionist approaches have been largely unsuccessful in providing an understanding of the pathogenesis of IR, there is a need for an integrative, time-resolved approach to elucidate the development of the disease.
  
  
  RESULTS
  Male ApoE3Leiden transgenic mice exhibiting a humanized lipid metabolism were fed a high-fat diet (HFD) for 0, 1, 6, 9, or 12 weeks. Development of IR was monitored in individual mice over time by performing glucose tolerance tests and measuring specific biomarkers in plasma, and hyperinsulinemic-euglycemic clamp analysis to assess IR in a tissue-specific manner. To elucidate the dynamics and tissue-specificity of metabolic and inflammatory processes key to IR development, a time-resolved systems analysis of gene expression and metabolite levels in liver, white adipose tissue (WAT), and muscle was performed. During HFD feeding, the mice became increasingly obese and showed a gradual increase in glucose intolerance. IR became first manifest in liver (week 6) and then in WAT (week 12), while skeletal muscle remained insulin-sensitive. Microarray analysis showed rapid upregulation of carbohydrate (only liver) and lipid metabolism genes (liver, WAT). Metabolomics revealed significant changes in the ratio of saturated to polyunsaturated fatty acids (liver, WAT, plasma) and in the concentrations of glucose, gluconeogenesis and Krebs cycle metabolites, and branched amino acids (liver). HFD evoked an early hepatic inflammatory response which then gradually declined to near baseline. By contrast, inflammation in WAT increased over time, reaching highest values in week 12. In skeletal muscle, carbohydrate metabolism, lipid metabolism, and inflammation was gradually suppressed with HFD.
  
  
  CONCLUSIONS
  HFD-induced IR is a time- and tissue-dependent process that starts in liver and proceeds in WAT. IR development is paralleled by tissue-specific gene expression changes, metabolic adjustments, changes in lipid composition, and inflammatory responses in liver and WAT involving p65-NFkB and SOCS3. The alterations in skeletal muscle are largely opposite to those in liver and WAT.
authors.affiliation: Quality of Life, Vascular and Metabolic Disease, TNO, Leiden, The Netherlands. Robert.Kleemann@tno.nl
authors.forename: Robert
authors.initials: R
authors.lastname: Kleemann
authors.forename: Marjan
authors.initials: M
authors.lastname: van Erk
authors.forename: Lars
authors.initials: L
authors.lastname: Verschuren
authors.forename: Anita M
authors.initials: AM
authors.lastname: van den Hoek
authors.forename: Maud
authors.initials: M
authors.lastname: Koek
authors.forename: Peter Y
authors.initials: PY
authors.lastname: Wielinga
authors.forename: Annie
authors.initials: A
authors.lastname: Jie
authors.forename: Linette
authors.initials: L
authors.lastname: Pellis
authors.forename: Ivana
authors.initials: I
authors.lastname: Bobeldijk-Pastorova
authors.forename: Thomas
authors.initials: T
authors.lastname: Kelder
authors.forename: Karin
authors.initials: K
authors.lastname: Toet
authors.forename: Suzan
authors.initials: S
authors.lastname: Wopereis
authors.forename: Nicole
authors.initials: N
authors.lastname: Cnubben
authors.forename: Chris
authors.initials: C
authors.lastname: Evelo
authors.forename: Ben
authors.initials: B
authors.lastname: van Ommen
authors.forename: Teake
authors.initials: T
authors.lastname: Kooistra
mesh_terms: D050154:Adiposity; D000818:Animals; D053318:Apolipoprotein E3 / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005951:Glucose Tolerance Test; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis
chemical_list: D053318:Apolipoprotein E3; D005230:Fatty Acids, Nonesterified