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Am J Physiol Lung Cell Mol Physiol. 2017 May 1;312(5):L688-L702. doi: 10.1152/ajplung.00364.2016. Epub 2017 Feb 17.

Insulin signaling via the PI3-kinase/Akt pathway regulates airway glucose uptake and barrier function in a CFTR-dependent manner.

Author information

1
Emory+Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia; s.a.molina@emory.edu.
2
Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
3
Emory+Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia.
4
Division of Pulmonology, Allergy & Immunology, Cystic Fibrosis and Sleep, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia; and.
5
Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.

Abstract

Cystic fibrosis-related diabetes is the most common comorbidity associated with cystic fibrosis (CF) and correlates with increased rates of lung function decline. Because glucose is a nutrient present in the airways of patients with bacterial airway infections and because insulin controls glucose metabolism, the effect of insulin on CF airway epithelia was investigated to determine the role of insulin receptors and glucose transport in regulating glucose availability in the airway. The response to insulin by human airway epithelial cells was characterized by quantitative PCR, immunoblot, immunofluorescence, and glucose uptake assays. Phosphatidylinositol 3-kinase/protein kinase B (Akt) signaling and cystic fibrosis transmembrane conductance regulator (CFTR) activity were analyzed by pharmacological and immunoblot assays. We found that normal human primary airway epithelial cells expressed glucose transporter 4 and that application of insulin stimulated cytochalasin B-inhibitable glucose uptake, consistent with a requirement for glucose transporter translocation. Application of insulin to normal primary human airway epithelial cells promoted airway barrier function as demonstrated by increased transepithelial electrical resistance and decreased paracellular flux of small molecules. This provides the first demonstration that airway cells express insulin-regulated glucose transporters that act in concert with tight junctions to form an airway glucose barrier. However, insulin failed to increase glucose uptake or decrease paracellular flux of small molecules in human airway epithelia expressing F508del-CFTR. Insulin stimulation of Akt1 and Akt2 signaling in CF airway cells was diminished compared with that observed in airway cells expressing wild-type CFTR. These results indicate that the airway glucose barrier is regulated by insulin and is dysfunctional in CF.

KEYWORDS:

airway epithelia; cystic fibrosis; cystic fibrosis transmembrane conductance regulator; glucose metabolism; glucose transporter 4; phosphatidylinositol 3-kinase; protein kinase B

PMID:
28213469
PMCID:
PMC5451595
DOI:
10.1152/ajplung.00364.2016
[Indexed for MEDLINE]
Free PMC Article

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