title: Fasting, but not exercise, increases adipose triglyceride lipase (ATGL) protein and reduces G(0)/G(1) switch gene 2 (G0S2) protein and mRNA content in human adipose tissue.
abstract: BACKGROUND
  Fasting and exercise are characterized by increased lipolysis, but the underlying mechanisms are not fully understood.
  
  
  OBJECTIVE
  The study was designed to test whether fasting and exercise affect mRNA and protein levels of adipose triglyceride lipase (ATGL) and G(0)/G(1) switch gene 2 (G0S2), a recently discovered ATGL inhibitor, in humans.
  
  
  METHODS
  We studied eight healthy men (age, 25.5 ± 4.3 yr) for 6 h (a 4-h basal and a 2-h clamp period) on three occasions in a randomized crossover design: 1) in the basal state and after; 2) 72-h fasting; and 3) 1-h exercise (65% VO(2max)). Subcutaneous abdominal adipose tissue (AT) biopsies were taken at t = 30 and 270 min.
  
  
  METHODS
  The study was conducted at a university hospital research unit.
  
  
  RESULTS
  Circulating free fatty acids and GH were increased, and C-peptide was decreased by both fasting and exercise. During fasting, insulin failed to suppress free fatty acid levels, suggesting AT insulin resistance. ATGL protein was increased 44% (P < 0.001), and G0S2 mRNA and protein were decreased 56% (P = 0.02) and 54% (P = 0.01), respectively, after fasting, but both ATGL and G0S2 were unaffected by exercise. Protein levels of hormone-sensitive lipase and comparative gene identification-58 were unaffected throughout.
  
  
  CONCLUSIONS
  We found increased AT content of ATGL and decreased protein and mRNA content of the ATGL inhibitor G0S2, suggesting increased ATGL activity during fasting, but not after short-term exercise. These findings are compatible with the notion that the ATGL-G0S2 complex is an important long-term regulator of lipolysis under physiological conditions such as fasting in humans.
authors: Medical Research Laboratories, Aarhus University Hospital, 8000 Aarhus C, Denmark. tsn@farm.au.dk
authors: Thomas S
authors: TS
authors: Nielsen
authors: Mikkel H
authors: MH
authors: Vendelbo
authors: Niels
authors: N
authors: Jessen
authors: Steen B
authors: SB
authors: Pedersen
authors: Jens O
authors: JO
authors: Jørgensen
authors: Sten
authors: S
authors: Lund
authors: Niels
authors: N
authors: Møller