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Aquaporin-9 Protein Is the Primary Route of Hepatocyte Glycerol Uptake for Glycerol Gluconeogenesis in Mice

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Author

  • Sabina Jelen
  • Soeren Wacker
  • Camilo Aponte-Santamaria
  • Martin Skott
  • Aleksandra Rojek
  • Urban Johanson
  • Per Kjellbom
  • Soren Nielsen
  • Bert L. de Groot
  • Michael Ruetzler

Summary, in English

It has been hypothesized that aquaporin-9 (AQP9) is part of the unknown route of hepatocyte glycerol uptake. In a previous study, leptin receptor-deficient wild-type mice became diabetic and suffered from fasting hyperglycemia whereas isogenic AQP9(-/-) knock-out mice remained normoglycemic. The reason for this improvement in AQP9(-/-) mice was not established before. Here, we show increased glucose output (by 123% +/- 36% S. E.) in primary hepatocyte culture when 0.5 mM extracellular glycerol was added. This increase depended on AQP9 because it was absent in AQP9(-/-) cells. Likewise, the increase was abolished by 25 mu M HTS13286 (IC(50) similar to 2 mu M), a novel AQP9 inhibitor, which we identified in a small molecule library screen. Similarly, AQP9 deletion or chemical inhibition eliminated glycerol-enhanced glucose output in perfused liver preparations. The following control experiments suggested inhibitor specificity to AQP9: (i) HTS13286 affected solute permeability in cell lines expressing AQP9, but not in cell lines expressing AQPs 3, 7, or 8. (ii) HTS13286 did not influence lactate-and pyruvate-dependent hepatocyte glucose output. (iii) HTS13286 did not affect glycerol kinase activity. Our experiments establish AQP9 as the primary route of hepatocyte glycerol uptake for gluconeogenesis and thereby explain the previously observed, alleviated diabetes in leptin receptor-deficient AQP9(-/-) mice.

Publishing year

2011

Language

English

Pages

44319-44325

Publication/Series

Journal of Biological Chemistry

Volume

286

Issue

52

Document type

Journal article

Publisher

American Society for Biochemistry and Molecular Biology

Topic

  • Biological Sciences

Status

Published

ISBN/ISSN/Other

  • ISSN: 1083-351X