Authors: C Beall D L Hamilton J Gallagher L Logie K Wright M P Soutar S Dadak F B Ashford E Haythorne Q Du A Jovanović R J McCrimmon M L J Ashford
Publish Date: 2012/07/04
Volume: 55, Issue: 9, Pages: 2432-2444
Abstract
Hypothalamic glucoseexcited GE neurons contribute to wholebody glucose homeostasis and participate in the detection of hypoglycaemia This system appears defective in type 1 diabetes in which hypoglycaemia commonly occurs Unfortunately it is at present unclear which molecular components required for glucose sensing are produced in individual neurons and how these are functionally linked We used the GT17 mouse hypothalamic cell line to address these issuesElectrophysiological recordings coupled with measurements of gene expression and protein levels and activity were made from unmodified GT17 cells and cells in which AMPactivated protein kinase AMPK catalytic subunit gene expression and activity were reducedHypothalamic GT17 neurons express the genes encoding glucokinase and ATPsensitive K+ channel KATP subunits K ir 62 and Sur1 and exhibit GEtype glucosesensing behaviour Lowered extracellular glucose concentration hyperpolarised the cells in a concentrationdependent manner an outcome that was reversed by tolbutamide Inhibition of glucose uptake or metabolism hyperpolarised cells showing that energy metabolism is required to maintain their resting membrane potential Short hairpin shRNA directed to Ampkα2 also known as Prkaa2 reduced GT17 cell AMPKα2 but not AMPKα1 activity and lowered the threshold for hypoglycaemiainduced hyperpolarisation shAmpkα1 also known as Prkaa1 had no effect on glucosesensing or AMPKα2 activity Decreased uncoupling protein 2 Ucp2 mRNA was detected in AMPKα2reduced cells suggesting that AMPKα2 regulates UCP2 levelsWe have demonstrated that GT17 cells closely mimic GE neuron glucosesensing behaviour and reducing AMPKα2 blunts their responsiveness to hypoglycaemic challenge possibly by altering UCP2 activity These results show that suppression of AMPKα2 activity inhibits normal glucosesensing behaviour and may contribute to defective detection of hypoglycaemia
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