Multitissue 2H/13C flux analysis reveals reciprocal upregulation of renal gluconeogenesis in hepatic PEPCK-C–knockout mice
Mohsin Rahim, Clinton M. Hasenour, Tomasz K. Bednarski, Curtis C. Hughey, David H. Wasserman, Jamey D. Young
Mohsin Rahim, Clinton M. Hasenour, Tomasz K. Bednarski, Curtis C. Hughey, David H. Wasserman, Jamey D. Young
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Resource and Technical Advance Hepatology Metabolism

Multitissue 2H/13C flux analysis reveals reciprocal upregulation of renal gluconeogenesis in hepatic PEPCK-C–knockout mice

Abstract

The liver is the major source of glucose production during fasting under normal physiological conditions. However, the kidney may also contribute to maintaining glucose homeostasis in certain circumstances. To test the ability of the kidney to compensate for impaired hepatic glucose production in vivo, we developed a stable isotope approach to simultaneously quantify gluconeogenic and oxidative metabolic fluxes in the liver and kidney. Hepatic gluconeogenesis from phosphoenolpyruvate was disrupted via liver-specific knockout of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C; KO). 2H/13C isotopes were infused in fasted KO and WT littermate mice, and fluxes were estimated from isotopic measurements of tissue and plasma metabolites using a multicompartment metabolic model. Hepatic gluconeogenesis and glucose production were reduced in KO mice, yet whole-body glucose production and arterial glucose were unaffected. Glucose homeostasis was maintained by a compensatory rise in renal glucose production and gluconeogenesis. Renal oxidative metabolic fluxes of KO mice increased to sustain the energetic and metabolic demands of elevated gluconeogenesis. These results show the reciprocity of the liver and kidney in maintaining glucose homeostasis by coordinated regulation of gluconeogenic flux through PEPCK-C. Combining stable isotopes with mathematical modeling provides a versatile platform to assess multitissue metabolism in various genetic, pathophysiological, physiological, and pharmacological settings.

Authors

Mohsin Rahim, Clinton M. Hasenour, Tomasz K. Bednarski, Curtis C. Hughey, David H. Wasserman, Jamey D. Young

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Figure 3

Liver PEPCK-C–KO mice exhibit significant renal gluconeogenesis compared with WT littermates.

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Liver PEPCK-C–KO mice exhibit significant renal gluconeogenesis compared...
(A) Absolute hepatic fluxes for WT (n = 7) and KO (n = 4) mice, analyzed by a 2-tailed t test where *P < 0.05. The map represents the hepatic compartment shown in Figure 2B and Supplemental Table 1. Measured metabolic nodes are shown in green (Supplemental Tables 2 and 3). Arrows with green highlighting represent fluxes that are reduced in the livers from KO mice compared with WT littermates. (B) Absolute renal fluxes for WT (n = 7) and KO (n = 4) mice, analyzed by a 2-tailed t test where *P < 0.05. The map represents the renal compartment shown in Figure 2B and Supplemental Table 1. Measured metabolic nodes are shown in green (Supplemental Tables 2 and 3). Arrows with red highlighting represent fluxes that are increased in the kidneys from KO mice compared with WT littermates. (C and D) Pck1 and Pck2 fold change in the liver (C) and kidney (D) of KO (n = 4) relative to WT (n = 4) mice. Differences between group means were assessed by a 2-tailed t test (*P < 0.05, †P < 0.10). Protein expression was normalized to total protein content in each lane. (E) Plasma glucagon concentration after ~20 hours of fasting in WT (n = 4) and KO (n = 6) mice, analyzed by a 2-tailed t test where *P < 0.05. (F). Fold change in gene expression in kidneys of KO (n = 4) relative to WT (n = 4) mice, analyzed by a 2-tailed t test where *P < 0.05.