title: Norepinephrine infusion during moderate-intensity exercise increases glucose production and uptake.
abstract: A role for the increase in circulating norepinephrine (NE) during intense exercise [IE; > or = 80% maximum O(2) uptake (VO(2max))] in the marked increment in glucose rate of production (Ra) during IE is hypothesized. Seven fit male subjects (27 +/- 2 yr old; body mass index, 23 +/- 1 kg/m(2); VO(2max), 63 +/- 5 mL/kg.min) underwent 40 min of postabsorptive moderate-intensity (53% VO(2max)) cycle ergometer exercise (126 +/- 14 W), once without [control (CON)] and once with NE infusion (0.1 microg/kg.min) from 30-40 min (NE). With infusion, plasma NE reached 15.9 +/- 1.0 nM (8-fold rest, 2-fold CON). Ra doubled to 4.40 +/- 0.44 in CON, but rose to 7.55 +/- 0.68 mg/kg.min with NE infusion (P = 0.003). Ra correlated strongly (r(2) = 0.92, P < 0.02) with plasma NE during and immediately after infusion. With NE infusion, peak glucose uptake [rate of disappearance (Rd), 6.57 +/- 0.59 vs. 4.53 +/- 0.55 mg/kg.min, P < 0.02] and glucose metabolic clearance rate (P < 0.05) were higher than in CON. Glycemia rose minimally during the NE infusion but did not differ between groups at any time during exercise. Glucagon-to-insulin ratio increased minimally, and epinephrine increased approximately 2.5- to 3-fold at peak but did not differ between groups. Thus, NE infusion during moderate exercise led to increments in Ra and Rd in fit individuals, supporting a possible contributory role for the increase of plasma NE in IE. NE effects on Rd and metabolic clearance rate during exercise may differ from its effects at rest.
authors.affiliation: McGill Nutrition and Food Science Centre, Royal Victoria, Montréal, Québec, Canada, H3A 1A1.
authors.forename: S H
authors.initials: SH
authors.lastname: Kreisman
authors.forename: N
authors.initials: N
authors.lastname: Ah Mew
authors.forename: J B
authors.initials: JB
authors.lastname: Halter
authors.forename: M
authors.initials: M
authors.lastname: Vranic
authors.forename: E B
authors.initials: EB
authors.lastname: Marliss
mesh_terms: D000328:Adult; D015444:Exercise; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009638:Norepinephrine / Q000097:blood / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D019289:Pyruvic Acid / Q000097:blood
chemical_list: D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose; D009638:Norepinephrine