title: Pannexin 1 is required for full activation of insulin-stimulated glucose uptake in adipocytes.
abstract: OBJECTIVE
  Defective glucose uptake in adipocytes leads to impaired metabolic homeostasis and insulin resistance, hallmarks of type 2 diabetes. Extracellular ATP-derived nucleotides and nucleosides are important regulators of adipocyte function, but the pathway for controlled ATP release from adipocytes is unknown. Here, we investigated whether Pannexin 1 (Panx1) channels control ATP release from adipocytes and contribute to metabolic homeostasis.
  
  
  METHODS
  We assessed Panx1 functionality in cultured 3T3-L1 adipocytes and in adipocytes isolated from murine white adipose tissue by measuring ATP release in response to known activators of Panx1 channels. Glucose uptake in cultured 3T3-L1 adipocytes was measured in the presence of Panx1 pharmacologic inhibitors and in adipocytes isolated from white adipose tissue from wildtype (WT) or adipocyte-specific Panx1 knockout (AdipPanx1 KO) mice generated in our laboratory. We performed in vivo glucose uptake studies in chow fed WT and AdipPanx1 KO mice and assessed insulin resistance in WT and AdipPanx1 KO mice fed a high fat diet for 12 weeks. Panx1 channel function was assessed in response to insulin by performing electrophysiologic recordings in a heterologous expression system. Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients.
  
  
  RESULTS
  Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP. Pharmacologic inhibition or selective genetic deletion of Panx1 from adipocytes decreased insulin-induced glucose uptake in vitro and in vivo and exacerbated diet-induced insulin resistance in mice. Further, we identify insulin as a novel activator of Panx1 channels. In obese humans Panx1 expression in adipose tissue is increased and correlates with the degree of insulin resistance.
  
  
  CONCLUSIONS
  We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis.
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA ; Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Samantha E
authors.initials: SE
authors.lastname: Adamson
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Akshaya K
authors.initials: AK
authors.lastname: Meher
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Yu-Hsin
authors.initials: YH
authors.lastname: Chiu
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Joanna K
authors.initials: JK
authors.lastname: Sandilos
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Nathaniel P
authors.initials: NP
authors.lastname: Oberholtzer
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Natalie N
authors.initials: NN
authors.lastname: Walker
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Hargett
authors.affiliation: Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA ; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Seaman
authors.affiliation: Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA ; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Shayn M
authors.initials: SM
authors.lastname: Peirce-Cottler
authors.affiliation: Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA ; Department of Physiology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Brant E
authors.initials: BE
authors.lastname: Isakson
authors.affiliation: Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA ; Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Coleen A
authors.initials: CA
authors.lastname: McNamara
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Susanna R
authors.initials: SR
authors.lastname: Keller
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Thurl E
authors.initials: TE
authors.lastname: Harris
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Bayliss
authors.affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA ; Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Norbert
authors.initials: N
authors.lastname: Leitinger
keywords: Adipocyte; Extracellular ATP; Glucose uptake; Pannexin 1