title: Aquaporin-9 protein is the primary route of hepatocyte glycerol uptake for glycerol gluconeogenesis in mice.
abstract: 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 μM HTS13286 (IC(50) ~ 2 μM), 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.
authors.affiliation: From the Water and Salt Research Center, Department of Biomedicine, Aarhus University, Wilhelm Meyers Allè, DK-8000 Aarhus C, Denmark.
authors.forename: Sabina
authors.initials: S
authors.lastname: Jelen
authors.forename: Sören
authors.initials: S
authors.lastname: Wacker
authors.forename: Camilo
authors.initials: C
authors.lastname: Aponte-Santamaría
authors.forename: Martin
authors.initials: M
authors.lastname: Skott
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Rojek
authors.forename: Urban
authors.initials: U
authors.lastname: Johanson
authors.forename: Per
authors.initials: P
authors.lastname: Kjellbom
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Bert L
authors.initials: BL
authors.lastname: de Groot
authors.forename: Michael
authors.initials: M
authors.lastname: Rützler
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003451:Cryoprotective Agents / Q000378:metabolism / Q000494:pharmacology; D003920:Diabetes Mellitus / Q000235:genetics / Q000378:metabolism; D005943:Gluconeogenesis / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000235:genetics / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism* / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D019289:Pyruvic Acid / Q000378:metabolism; D054411:Receptors, Leptin / Q000235:genetics / Q000378:metabolism
chemical_list: C491638:Aqp9 protein, mouse; D020346:Aquaporins; D003451:Cryoprotective Agents; D054411:Receptors, Leptin; D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose; D005990:Glycerol
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