title: Acute vagal stimulation attenuates cardiac metabolic response to β-adrenergic stress.
abstract: The effects of vagal stimulation (VS) on cardiac energy substrate metabolism are unknown. We tested the hypothesis that acute VS alters the balance between free fatty acid (FFA) and carbohydrate oxidation and opposes the metabolic effects of β-adrenergic stimulation. A clinical-type selective stimulator of the vagal efferent fibres was connected to the intact right vagus in chronically instrumented dogs. VS was set to reduce heart rate by 30 beats min(-1), and the confounding effects of bradycardia were then eliminated by pacing the heart at 165 beats min(-1). [(3)H]Oleate and [(14)C]glucose were infused to measure FFA and glucose oxidation. The heart was subjected to β-adrenergic stress by infusing dobutamine at 5, 10 and 15 μg kg(-1) min(-1) before and during VS. VS did not significantly affect baseline cardiac performance, haemodynamics or myocardial metabolism. However, at peak dobutamine stress, VS attenuated the increase in left ventricular pressure-diameter area from 235.9 ± 72.8 to 167.3 ± 55.8%, and in cardiac oxygen consumption from 173.9 ± 23.3 to 127.89 ± 6.2% (both P < 0.05), and thus mechanical efficiency was not enhanced. The increase in glucose oxidation fell from 289.3 ± 55.5 to 131.1 ± 20.9% (P < 0.05), while FFA oxidation was not increased by β-adrenergic stress and fell below baseline during VS only at the lowest dose of dobutamine. The functional and in part the metabolic changes were reversed by 0.1 mg kg(-1) atropine i.v. Our data show that acute right VS does not affect baseline cardiac metabolism, but attenuates myocardial oxygen consumption and glucose oxidation in response to adrenergic stress, thus functioning as a cardio-selective antagonist to β-adrenergic activation.
authors.affiliation: Department of Physiology, New York Medical College, Valhalla, NY, USA.
authors.forename: Claudio
authors.initials: C
authors.lastname: Vimercati
authors.forename: Khaled
authors.initials: K
authors.lastname: Qanud
authors.forename: Itamar
authors.initials: I
authors.lastname: Ilsar
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Mitacchione
authors.forename: Roberto
authors.initials: R
authors.lastname: Sarnari
authors.forename: Daniella
authors.initials: D
authors.lastname: Mania
authors.forename: Ryan
authors.initials: R
authors.lastname: Faulk
authors.forename: William C
authors.initials: WC
authors.lastname: Stanley
authors.forename: Hani N
authors.initials: HN
authors.lastname: Sabbah
authors.forename: Fabio A
authors.initials: FA
authors.lastname: Recchia
mesh_terms: D058665:Adrenergic beta-1 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D003326:Coronary Circulation; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006439:Hemodynamics; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D058665:Adrenergic beta-1 Receptor Agonists; D005230:Fatty Acids, Nonesterified; D011943:Receptors, Adrenergic, beta; D004280:Dobutamine; D005947:Glucose