Control of Blood Glucose in the Absence of Hepatic Glucose Production During Prolonged Fasting in Mice

Induction of Renal and Intestinal Gluconeogenesis by Glucagon

  1. Fabienne Rajas
  1. Institut National de la Santé et de la Recherche Médicale, U855, Lyon, France; the Université de Lyon, Lyon, France; and the Université Lyon 1, Villeurbanne, France
  1. Corresponding author: Fabienne Rajas, fabienne.rajas{at}univ-lyon1.fr.

Abstract

OBJECTIVE Since the pioneering work of Claude Bernard, the scientific community has considered the liver to be the major source of endogenous glucose production in all postabsorptive situations. Nevertheless, the kidneys and intestine can also produce glucose in blood, particularly during fasting and under protein feeding. The aim of this study was to better define the importance of the three gluconeogenic organs in glucose homeostasis.

RESEARCH DESIGN AND METHODS We investigated blood glucose regulation during fasting in a mouse model of inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc−/− mice), encoding a mandatory enzyme for glucose production. Furthermore, we characterized molecular mechanisms underlying expression changes of gluconeogenic genes (G6pc, Pck1, and glutaminase) in both the kidneys and intestine.

RESULTS We show that the absence of hepatic glucose release had no major effect on the control of fasting plasma glucose concentration. Instead, compensatory induction of gluconeogenesis occurred in the kidneys and intestine, driven by glucagon, glucocorticoids, and acidosis. Moreover, the extrahepatic action of glucagon took place in wild-type mice.

CONCLUSIONS Our study provides a definitive quantitative estimate of the capacity of extrahepatic gluconeogenesis to sustain fasting endogenous glucose production under the control of glucagon, regardless of the contribution of the liver. Thus, the current dogma relating to the respective role of the liver and of extrahepatic gluconeogenic organs in glucose homeostasis requires re-examination.

Footnotes

  • Received April 29, 2011.
  • Accepted September 18, 2011.

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

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  1. Diabetes vol. 60 no. 12 3121-3131
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