title: Oleate induces KATPchannel-dependent hyperpolarization in mouse hypothalamic glucose-excited neurons without altering cellular energy charge.
abstract: The unsaturated fatty acid, oleate exhibits anorexigenic properties reducing food intake and hepatic glucose output. However, its mechanism of action in the hypothalamus has not been fully determined. This study investigated the effects of oleate and glucose on GT1-7 mouse hypothalamic cells (a model of glucose-excited (GE) neurons) and mouse arcuate nucleus (ARC) neurons. Whole-cell and perforated patch-clamp recordings, immunoblotting and cell energy status measures were used to investigate oleate- and glucose-sensing properties of mouse hypothalamic neurons. Oleate or lowered glucose concentration caused hyperpolarization and inhibition of firing of GT1-7 cells by the activation of ATP-sensitive K+channels (KATP). This effect of oleate was not dependent on fatty acid oxidation or raised AMP-activated protein kinase activity or prevented by the presence of the UCP2 inhibitor genipin. Oleate did not alter intracellular calcium, indicating that CD36/fatty acid translocase may not play a role. However, oleate activation of KATPmay require ATP metabolism. The short-chain fatty acid octanoate was unable to replicate the actions of oleate on GT1-7 cells. Although oleate decreased GT1-7 cell mitochondrial membrane potential there was no change in total cellular ATP or ATP/ADP ratios. Perforated patch and whole-cell recordings from mouse hypothalamic slices demonstrated that oleate hyperpolarized a subpopulation of ARC GE neurons by KATPactivation. Additionally, in a separate small population of ARC neurons, oleate application or lowered glucose concentration caused membrane depolarization. In conclusion, oleate induces KATP-dependent hyperpolarization and inhibition of firing of a subgroup of GE hypothalamic neurons without altering cellular energy charge.
authors.affiliation: Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
authors.forename: Selma
authors.initials: S
authors.lastname: Dadak
authors.affiliation: Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK.
authors.forename: Craig
authors.initials: C
authors.lastname: Beall
authors.affiliation: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Vlachaki Walker
authors.affiliation: Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
authors.forename: Marc P M
authors.initials: MPM
authors.lastname: Soutar
authors.affiliation: Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
authors.forename: Rory J
authors.initials: RJ
authors.lastname: McCrimmon
authors.affiliation: Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK. Electronic address: m.l.j.ashford@dundee.ac.uk.
authors.forename: Michael L J
authors.initials: MLJ
authors.lastname: Ashford
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002460:Cell Line; D005947:Glucose / Q000494:pharmacology*; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D054086:KATP Channels / Q000187:drug effects*; D053078:Membrane Potential, Mitochondrial; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D019301:Oleic Acid / Q000494:pharmacology*
chemical_list: D054086:KATP Channels; D019301:Oleic Acid; D000255:Adenosine Triphosphate; D055372:AMP-Activated Protein Kinases; D005947:Glucose
keywords: K(ATP); fatty acid oxidation; glucose sensing; hypothalamus; mitochondria; oleate