Norepinephrine transporter function and autonomic control of metabolism.
Genetic variability, numerous medications, and some illicit drugs influence norepinephrine transporter (NET) function; however, the metabolic consequences of NET inhibition are poorly understood. We performed a randomized, double-blind, cross-over trial in 15 healthy subjects who ingested 8 mg of the selective NET inhibitor reboxetine or placebo. Energy expenditure and substrate oxidation rates were determined by indirect calorimetry before and during iv infusion of 0.25, 0.5, 1, and 2 micro g isoproterenol/min. Adipose tissue metabolism was studied by microdialysis before and during local isoproterenol perfusion. At rest, energy expenditure and substrate oxidation rates did not differ between reboxetine and placebo treatment. At 1 micro g/min isoproterenol, energy expenditure was significantly increased in men (+15%) and women (+20%) with both reboxetine and placebo treatment. However, carbohydrate oxidation rate was significantly higher with reboxetine compared with placebo. Baseline and isoproterenol-stimulated adipose tissue blood flow was about 2-fold higher with reboxetine vs. placebo. Furthermore, glucose supply and metabolism was significantly increased and lipid mobilization much more stimulated in adipose tissue under reboxetine when compared with placebo at all isoproterenol concentrations used. We conclude that acute NET inhibition increases adipose tissue glucose uptake and metabolism. While lipid mobilization is increased, overall lipid oxidation is decreased during beta-adrenergic stimulation. This effect cannot be explained by increased systemic or adipose tissue norepinephrine concentrations. Instead, NET inhibition may sensitize adipose tissue to beta-adrenergic stimulation.
Boschmann
Michael
M
German Institute of Human Nutrition, 14558 Potsdam, Germany.
Schroeder
Christoph
C
Christensen
Niels Juel
NJ
Tank
Jens
J
Krupp
Goetz
G
Biaggioni
Italo
I
Klaus
Susanne
S
Sharma
Arya M
AM
Luft
Friedrich C
FC
Jordan
Jens
J
D000273:Adipose Tissue / Q000098:blood supply / Q000737:chemistry / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage; D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D001783:Blood Flow Velocity; D002153:Calorimetry, Indirect; D050260:Carbohydrate Metabolism; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000378:metabolism; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000008:administration & dosage; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D017551:Microdialysis; D009025:Morpholines / Q000008:administration & dosage; D009638:Norepinephrine / Q000032:analysis; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010084:Oxidation-Reduction; D010919:Placebos; D011187:Posture; D000077593:Reboxetine; D013484:Supination; D027981:Symporters / Q000037:antagonists & inhibitors / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D009025:Morpholines; D050484:Norepinephrine Plasma Membrane Transport Proteins; D010919:Placebos; C493227:SLC6A2 protein, human; D027981:Symporters; D000077593:Reboxetine; D005947:Glucose; D007545:Isoproterenol; D009638:Norepinephrine