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Biophysical assessment of AQP9 as real membrane pathway in hepatocyte glycerol uptake
Author(s) -
Calamita Giuseppe,
Fanelli Elena,
Svelto Maria,
Gena Patrizia
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.1000.7
Subject(s) - glycerol , hepatocyte , aquaporin , phloretin , gluconeogenesis , chemistry , glycerol kinase , medicine , endocrinology , biochemistry , metabolism , biology , in vitro
Glycerol, released from adipocytes, flows through bloodstream to liver where it is taken up to supply gluconeogenesis. Although glycerol is central to metabolic homeostasis, the molecular mechanism underlying the glycerol uptake across the hepatocyte basolateral plasma membrane (BLPM) is mostly elusive. Here, we evaluate biophysically whether AQP9, an aquaglyceroporin channel, is entry route in liver glycerol uptake. Facilitated diffusion of glycerol across the hepatocyte BLPM was proved by the low Ea (3.5 kcal/mol) and strong phloretin and HgCl 2 inhibitions characterizing the transport of glycerol. Fasting ( vs feeding) markedly increased liver AQP9 expression in a time‐dependent manner. The highest levels of AQP9 transcript and protein were seen after 18 h of fasting. AQP9 returned to basal levels after 72 h refeeding. Of note, both the BLPM glycerol permeability and AQP9 protein extents changed accordingly to the variations in plasma glycerol levels. The expression of AQP8, the other hepatocyte aquaporin, was unchanged. Overall, these results prove real functional relevance for AQP9 in liver glycerol uptake and suggest a new important player underlying metabolic and energy (dys)balance.