title: Mouse hypothalamic GT1-7 cells demonstrate AMPK-dependent intrinsic glucose-sensing behaviour.
abstract: OBJECTIVE
  Hypothalamic glucose-excited (GE) neurons contribute to whole-body 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 GT1-7 mouse hypothalamic cell line to address these issues.
  
  
  METHODS
  Electrophysiological recordings, coupled with measurements of gene expression and protein levels and activity, were made from unmodified GT1-7 cells and cells in which AMP-activated protein kinase (AMPK) catalytic subunit gene expression and activity were reduced.
  
  
  RESULTS
  Hypothalamic GT1-7 neurons express the genes encoding glucokinase and ATP-sensitive K(+) channel (K(ATP)) subunits K                            (                               ir                            )                            6.2 and Sur1 and exhibit GE-type glucose-sensing behaviour. Lowered extracellular glucose concentration hyperpolarised the cells in a concentration-dependent 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 (sh)RNA directed to Ampkα2 (also known as Prkaa2) reduced GT1-7 cell AMPKα2, but not AMPKα1, activity and lowered the threshold for hypoglycaemia-induced hyperpolarisation. shAmpkα1 (also known as Prkaa1) had no effect on glucose-sensing or AMPKα2 activity. Decreased uncoupling protein 2 (Ucp2) mRNA was detected in AMPKα2-reduced cells, suggesting that AMPKα2 regulates UCP2 levels.
  
  
  CONCLUSIONS
  We have demonstrated that GT1-7 cells closely mimic GE neuron glucose-sensing 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 glucose-sensing behaviour and may contribute to defective detection of hypoglycaemia.
authors: Medical Research Institute, Division of Cardiovascular & Diabetes Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK.
authors: C
authors: C
authors: Beall
authors: D L
authors: DL
authors: Hamilton
authors: J
authors: J
authors: Gallagher
authors: L
authors: L
authors: Logie
authors: K
authors: K
authors: Wright
authors: M P
authors: MP
authors: Soutar
authors: S
authors: S
authors: Dadak
authors: F B
authors: FB
authors: Ashford
authors: E
authors: E
authors: Haythorne
authors: Q
authors: Q
authors: Du
authors: A
authors: A
authors: Jovanović
authors: R J
authors: RJ
authors: McCrimmon
authors: M L J
authors: ML
authors: Ashford
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002460:Cell Line / Q000378:metabolism*; D007003:Hypoglycemia / Q000235:genetics* / Q000503:physiopathology; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism; D051379:Mice; D024101:Mitochondrial Proteins / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D000071246:Uncoupling Protein 2
chemical_list: D007328:Insulin; D007473:Ion Channels; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; C000604390:Ucp2 protein, mouse; D000071246:Uncoupling Protein 2; C548179:Prkaa1 protein, mouse; D055372:AMP-Activated Protein Kinases