Circadian and long term variation of certain metabolites in fasted rat, implications

Abstract

In order to clarify subtle metabolic changes and the time course of metabolic variations associated with the central mechanisms of feeding and satiety, serum obtained from fasted rats during various hunger stages was profiled using a gas chromatography-mass spectrometry-computer system. On the basis of this work, chronobiological changes in metabolites following fasting were also evaluated. It was found that sampling method was critically important for determining the levels of organic acids. Changes in the time course of these organic acids were mainly divided into two patterns: a progressive increase over long-term starvation and a transient increase at about 36 hr of starvation. The levels of free fatty acids, 3-hydroxybutyrate, 2-deoxytetronate and 3-deoxypentonate were elevated around twilight after 24 and 36 hr of fasting. It was concluded that these organic acids were probably the compounds which elicit feeding behavior.