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

• DOI: 10.1210/jc.2011-0149
• Publication Date: 2011-05-26T04:34:31Z
• Authors: Thomas S. Nielsen; Mikkel H. Vendelbo; Niels Jessen; Steen B. Pedersen; Jens O. Jørgensen; Sten Lund; Niels Møller
• Keywords: Adult; Male; 0301 basic medicine; Cross-Over Studies; C-Peptide; Human Growth Hormone; Biopsy; Lipolysis; Subcutaneous Fat; Calorimetry, Indirect; Cell Cycle Proteins; Fasting; Lipase; Fatty Acids, Nonesterified; 3. Good health; Young Adult; 03 medical and health sciences; Glucose Clamp Technique; Humans; Insulin; RNA, Messenger; Exercise

Abstract

Context: 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.

Design and Participants: 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% VO2max). Subcutaneous abdominal adipose tissue (AT) biopsies were taken at t = 30 and 270 min.

Setting: 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.