Publications

Abstract

Exercise performed in the fasted state acutely increases fatty acid availability and utilization. Furthermore, activation of energy-sensing pathways and fatty acid metabolic genes can be augmented by fasting and fasted exercise. However, whether a similar effect occurs at higher exercise intensities remains poorly understood. This study aimed to assess the effect of fed and fasted exercise upon post-exercise signaling and mRNA responses during moderate- to high-intensity steady-state exercise. Eight male participants (age: 25 +/- 2 y, O2peak: 47.9 +/- 3.8 mL.kg(-1).min(-1)) performed one hour of cycling at 70% Wmaxin the fasted (FAST) state or two hours following ingestion of a carbohydrate-rich mixed-macronutrient breakfast (FED). Muscle biopsies were collected pre-, immediately and three hours post-exercise from the medial vastus lateralis, whilst venous blood samples were collected throughout the trial. Plasma NEFA and glycerol concentrations were elevated during FAST compared to FED, although substrate utilization during exercise was similar. AMPK(Thr172)phosphorylation was ~2.5-fold elevated post-exercise in both trials and was significantly augmented by ~30% during FAST. CREB(Ser133)phosphorylation was elevated ~2-fold during FAST, although CREB(Ser133)phosphorylation acutely decreased by ~50% immediately post-exercise. mRNA expression of PDK4was ~3-4-fold augmented by exercise and ~2-fold elevated throughout FAST, whilst expression of PPARGC1A mRNA was similarly activated (~10-fold) by exercise in both FED and FAST. In summary, performing moderate- to high-intensity steady-state exercise in the fasted state increases systemic lipid availability, elevates phosphorylation of AMPK(Thr172)and CREB(Ser133), and augments PDK4mRNA expression without corresponding increases in whole body fat oxidation and the mRNA expression of PPARGC1A.