AJP - Endocrinology and Metabolism, Vol 267, Issue 5 E801-E804, Copyright © 1994 by American Physiological Society
Paraxanthine (metabolite of caffeine) mimics caffeine's interaction with sympathetic control of thermogenesis
A. G. Dulloo, J. Seydoux and L. Girardier
Department of Physiology, University of Geneva, Switzerland.
The notion that paraxanthine (the major dimethylated by-product of
caffeine) may be a biologically active metabolite that could mediate some
of the effects of caffeine was tested in relation to the well-established
property of caffeine as a thermogenic stimulant. From studies measuring the
in vitro respiration rates of rat brown adipose tissue in the basal state
and in response to ephedrine (an enhancer of norepinephrine release from
sympathetic nerve endings), it is shown that paraxanthine has the same
potency as its parent compound, caffeine, in interacting with the
adrenergic system to potentiate thermogenesis. These data provide the first
direct demonstration of a physiological effect of the main metabolite of
caffeine and raise the possibility that paraxanthine may contribute
importantly to the ability of caffeine to potentiate the thermogenic
effects of well-known stimuli of the sympathetic nervous system such as
cold exposure, moderate exercise, and sympathomimetic drugs.
