Abstract
Exercise-induced alterations in adipose tissue insulin and/or β-adrenergic signaling may contribute to increases in whole-body fat oxidation following acute exercise. Thus, we examined changes in insulin (Akt, AS160) and β-adrenergic (PKA) signaling proteins in subcutaneous adipose tissue and whole-body fat oxidation in overweight women following acute high-intensity interval exercise (HIIE). Overweight females completed two experimental sessions in a randomized order: 1) control (bed rest) and 2) HIIE (10 × 4 min running intervals at 90% HRmax, 2-min recovery). Subcutaneous abdominal adipose tissue biopsies were obtained from 10 participants before (pre-), immediately (0hr) after (post-), 2hr post-, and 4hr post-exercise. Plasma glucose and insulin levels were assessed in venous blood samples obtained at each biopsy time-point from a different group of 5 participants (BMI-matched to biopsy group). Fat oxidation rates were estimated using the respiratory exchange ratio (RER) in all participants using indirect calorimetry pre-, 2hr post-, and 4hr post-exercise. RER was decreased (p < 0.05) at 2hr post-exercise after HIIE (0.77 ± 0.04) compared to control (0.84 ± 0.04). Despite higher plasma glucose (p < 0.01) and insulin (p < 0.05) levels at 0hr post-exercise versus control, no significant interaction effects were observed for Akt or AS160 phosphorylation (p > 0.05). Phosphorylation of PKA substrates was unaltered in both conditions (p > 0.05). Collectively, altered β-adrenergic and insulin signaling in subcutaneous adnominal adipose tissue does not appear to explain increased whole-body fat oxidation following acute HIIE.