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Adrenergic Metabolic and Hemodynamic Effects of Octopamine in the Liver
Department of Biochemistry, University of Maringá, Avenida Colombo 5790, Maringá 87020900, Brazil
All authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 21 September 2013; in revised form: 21 October 2013 / Accepted: 22 October 2013 / Published: 5 November 2013
Abstract: The fruit extracts of Citrus aurantium (bitter orange) are traditionally used as weight-loss products and as appetite suppressants. A component of these extracts is octopamine, which is an adrenergic agent. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of octopamine on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways and hemodynamics. Octopamine increased glycogenolysis, glycolysis, oxygen uptake, gluconeogenesis and the portal perfusion pressure. Octopamine also accelerated the oxidation of exogenous fatty acids (octanoate and oleate), as revealed by the increase in 14CO2 production derived from 14C labeled precursors. The changes in glycogenolysis, oxygen uptake and perfusion pressure were almost completely abolished by α1-adrenergic antagonists. The same changes were partly sensitive to the β-adrenergic antagonist propranolol. It can be concluded that octopamine accelerates both catabolic and anabolic processes in the liver via adrenergic stimulation. Acceleration of oxygen uptake under substrate-free perfusion conditions also means acceleration of the oxidation of endogenous fatty acids, which are derived from lipolysis. All these effects are compatible with an overall stimulating effect of octopamine on metabolism, which is compatible with its reported weight-loss effects in experimental animals.
Keywords: liver; octopamine; glycogenolysis; gluconeogenesis; oxygen uptake
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de Oliveira, A.L.; de Paula, M.N.; Comar, J.F.; Vilela, V.R.; Peralta, R.M.; Bracht, A. Adrenergic Metabolic and Hemodynamic Effects of Octopamine in the Liver. Int. J. Mol. Sci. 2013, 14, 21858-21872.
de Oliveira AL, de Paula MN, Comar JF, Vilela VR, Peralta RM, Bracht A. Adrenergic Metabolic and Hemodynamic Effects of Octopamine in the Liver. International Journal of Molecular Sciences. 2013; 14(11):21858-21872.
de Oliveira, Andrea L.; de Paula, Mariana N.; Comar, Jurandir F.; Vilela, Vanessa R.; Peralta, Rosane M.; Bracht, Adelar. 2013. "Adrenergic Metabolic and Hemodynamic Effects of Octopamine in the Liver." Int. J. Mol. Sci. 14, no. 11: 21858-21872.