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Journal of Nutrition Vol. 110 No. 5 May 1980, pp. 876-882
Copyright © 1980 by American Society for Nutrition
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Dietary Control of Circadian Variations in Serum Insulin, Glucagon and Hepatic Cyclic AMP1

Martin Tiedgen and Hans J. Seitz

Institut für Physiologische Chemie, Universitäts-Krankenhaus Eppendorf, Martinistr. 52, 2000 Hamburg 20, W. Germany

The effect of a high-protein diet (favoring hepatic glucose production) and of a high-carbohydrate diet (favoring glucose utilization) on the concentration of insulin and glucagon in the blood and on adenosine 3',5'-cyclic monophosphate (cyclic AMP) in the liver was investigated during a 24-hour cycle in rats. Feeding a high-protein diet resulted within 3 hours in an increase in the concentration of insulin (+100%) and glucagon (+220%). Whereas feeding a high-carbohydrate diet again induced a rise in insulin (+140%), no alterations in glucagon were observed. Hepatic cyclic AMP oscillated up or down under the protein or carbohydrate diet, respectively. A correlation between the insulin/glucagon molar ratio and the concentration of hepatic cyclic AMP was found. Proteinbound cyclic AMP, an indicator of protein kinase activation, corresponded closely to total cyclic AMP tissue concentration. The activity of a gluconeogenic key enzyme, P-enolpyruvate carboxykinase oscillated in parallel to hepatic cyclic AMP. Our data demonstrate that the protein and carbohydrate content of the diet determines the shape of circadian variation of hepatic cyclic AMP, insulin and glucagon.

KEY WORDS: • circadian variations • insulin • glucagon • hepatic cyclic AMP • dietary carbohydrate/protein content

1 Supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich -34- Endokrinologie.

Manuscript received 4 October 1979.




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