title: Effect of inhaled terbutaline on substrate utilization and 300-kcal time trial performance.
abstract: In a randomized, double-blind crossover design, we investigated the effect of the beta2-agonist terbutaline (TER) on endurance performance and substrate utilization in nine moderately trained men [maximum oxygen uptake (V̇O(2 max)) 58.9 ± 3.1 ml·min(-1)·kg(-1)]. Subjects performed 60 min of submaximal exercise (65-70% of V̇O(2 max)) immediately followed by a 300-kcal time trial with inhalation of either 15 mg of TER or placebo (PLA). Pulmonary gas exchange was measured during the submaximal exercise, and muscle biopsies were collected before and after the exercise bouts. Time trial performance was not different between TER and PLA (1,072 ± 145 vs. 1,054 ± 125 s). During the submaximal exercise, respiratory exchange ratio, glycogen breakdown (TER 266 ± 32, PLA 195 ± 28 mmol/kg dw), and muscle lactate accumulation (TER 20.3 ± 1.6, PLA 13.2 ± 1.2 mmol/kg dw) were higher (P < 0.05) with TER than PLA. There was no difference between TER and PLA in net muscle glycogen utilization or lactate accumulation during the time trial. Intramyocellular triacylglycerol content did not change with treatment or exercise. Pyruvate dehydrogenase-E1α phosphorylation at Ser(293) and Ser(300) was lower (P < 0.05) before submaximal exercise with TER than PLA, with no difference after the submaximal exercise and the time trial. Before submaximal exercise, acetyl-CoA carboxylase 2 (ACC2) phosphorylation at Ser(221) was higher (P < 0.05) with TER than PLA. There was no difference in phosphorylation of alpha 5'-AMP-activated protein kinase (αAMPK) at Thr(172) between treatments. The present study suggests that beta2-agonists do not enhance 300-kcal time trial performance, but they increase carbohydrate metabolism in skeletal muscles during submaximal exercise independent of AMPK and ACC phosphorylation, and that this effect diminishes as drug exposure time, exercise duration, and intensity are increased.
authors.affiliation: Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, Denmark; Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark; Anderskalsen@gmail.com.
authors.forename: Anders
authors.initials: A
authors.lastname: Kalsen
authors.affiliation: Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, Denmark; Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Morten
authors.initials: M
authors.lastname: Hostrup
authors.affiliation: Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, Denmark;
authors.forename: Sebastian
authors.initials: S
authors.lastname: Karlsson
authors.affiliation: Norwegian Doping Control Laboratory, Oslo University Hospital, Oslo, Norway; and School of Pharmacy, University of Oslo, Oslo, Norway.
authors.forename: Peter
authors.initials: P
authors.lastname: Hemmersbach
authors.affiliation: Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Jens
authors.initials: J
authors.lastname: Bangsbo
authors.affiliation: Respiratory Research Unit, Bispebjerg University Hospital, Copenhagen, Denmark;
authors.forename: Vibeke
authors.initials: V
authors.lastname: Backer
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000280:Administration, Inhalation; D058666:Adrenergic beta-2 Receptor Agonists / Q000008:administration & dosage*; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects*; D005080:Exercise Test; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D010807:Physical Endurance; D012119:Respiration / Q000187:drug effects; D013647:Task Performance and Analysis; D013726:Terbutaline / Q000008:administration & dosage*; D013997:Time Factors; D055815:Young Adult
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D001786:Blood Glucose; D019344:Lactic Acid; D006003:Glycogen; D055372:AMP-Activated Protein Kinases; C520105:ACACB protein, human; D000103:Acetyl-CoA Carboxylase; D013726:Terbutaline
keywords: exercise performance; substrate utilization; terbutaline