title: Akt, AS160, metabolic risk factors and aerobic fitness in middle-aged women.
abstract: OBJECTIVE
  This study investigated the association between the basal (rest) insulin-signaling proteins, Akt, and the Akt substrate AS160, metabolic risk factors, inflammatory markers and aerobic fitness, in middle-aged women with varying numbers of metabolic risk factors for type 2 diabetes.
  
  
  METHODS
  Sixteen women (n=16) aged 51.3 +/- 5.1 (mean +/- SD) years provided muscle biopsies and blood samples at rest. In addition, anthropometric characteristics and aerobic power were assessed and the number of metabolic risk factors for each participant was determined (IDF criteria).
  
  
  RESULTS
  The mean number of metabolic risk factors was 1.6 +/- 1.2. Total Akt was negatively correlated with IL-1beta (r = -0.45, p = 0.046), IL-6 (r = -0.44, p = 0.052) and TNF-alpha (r = -0.51, p = 0.025). Phosphorylated AS160 was positively correlated with HDL (r = 0.58, p = 0.024) and aerobic fitness (r = 0.51, p = 0.047). Furthermore, a multiple regression analysis revealed that both HDL (t = 2.5, p = 0.032) and VO2peak (t = 2.4, p = 0.037) were better predictors for phosphorylated AS160 than TNF-alpha or IL-6 (p > 0.05).
  
  
  CONCLUSIONS
  Elevated inflammatory markers and increased metabolic risk factors may inhibit insulin-signaling protein phosphorylation in middle-aged women, thereby increasing insulin resistance under basal conditions. Furthermore, higher HDL and fitness levels are associated with an increased AS160 phosphorylation, which may in turn reduce insulin resistance.
authors.affiliation: Institute of Sport, Exercise and Active Living, School of Sport and Exercise Science, Victoria University, Melbourne, Australia. itamar.levinger@vu.edu.au
authors.forename: Itamar
authors.initials: I
authors.lastname: Levinger
authors.forename: Kirsten F
authors.initials: KF
authors.lastname: Howlett
authors.forename: Jonathan
authors.initials: J
authors.lastname: Peake
authors.forename: Andrew
authors.initials: A
authors.lastname: Garnham
authors.forename: David L
authors.initials: DL
authors.lastname: Hare
authors.forename: George
authors.initials: G
authors.lastname: Jerums
authors.forename: Steve
authors.initials: S
authors.lastname: Selig
authors.forename: Craig
authors.initials: C
authors.lastname: Goodman
mesh_terms: D001786:Blood Glucose; D001794:Blood Pressure; D015153:Blotting, Western; D005260:Female; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000378:metabolism* / Q000503:physiopathology; D007333:Insulin Resistance / Q000502:physiology; D008075:Lipoproteins, HDL / Q000097:blood; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D010766:Phosphorylation; D010809:Physical Fitness / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012307:Risk Factors; D014280:Triglycerides / Q000097:blood; D055105:Waist Circumference
chemical_list: D001786:Blood Glucose; D020690:GTPase-Activating Proteins; D008075:Lipoproteins, HDL; C518767:TBC1D4 protein, human; D014280:Triglycerides; D051057:Proto-Oncogene Proteins c-akt