title: Acute nutrient regulation of the mitochondrial glutathione redox state in pancreatic β-cells.
abstract: The glucose stimulation of insulin secretion by pancreatic β-cells depends on increased production of metabolic coupling factors, among which changes in NADPH and ROS (reactive oxygen species) may alter the glutathione redox state (EGSH) and signal through changes in thiol oxidation. However, whether nutrients affect EGSH in β-cell subcellular compartments is unknown. Using redox-sensitive GFP2 fused to glutaredoxin 1 and its mitochondria-targeted form, we studied the acute nutrient regulation of EGSH in the cytosol/nucleus or the mitochondrial matrix of rat islet cells. These probes were mainly expressed in β-cells and reacted to low concentrations of exogenous H2O2 and menadione. Under control conditions, cytosolic/nuclear EGSH was close to -300 mV and unaffected by glucose (from 0 to 30 mM). In comparison, mitochondrial EGSH was less negative and rapidly regulated by glucose and other nutrients, ranging from -280 mV in the absence of glucose to -299 mV in 30 mM glucose. These changes were largely independent from changes in intracellular Ca(2+) concentration and in mitochondrial pH. They were unaffected by overexpression of SOD2 (superoxide dismutase 2) and mitochondria-targeted catalase, but were inversely correlated with changes in NAD(P)H autofluorescence, suggesting that they indirectly resulted from increased NADPH availability rather than from changes in ROS concentration. Interestingly, the opposite regulation of mitochondrial EGSH and NAD(P)H autofluorescence by glucose was also observed in human islets isolated from two donors. In conclusion, the present study demonstrates that glucose and other nutrients acutely reduce mitochondrial, but not cytosolic/nuclear, EGSH in pancreatic β-cells under control conditions.
authors.affiliation: *Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels B-1200, Belgium.
authors.forename: Hilton K
authors.initials: HK
authors.lastname: Takahashi
authors.affiliation: *Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels B-1200, Belgium.
authors.forename: Laila R B
authors.initials: LR
authors.lastname: Santos
authors.affiliation: *Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels B-1200, Belgium.
authors.forename: Letícia P
authors.initials: LP
authors.lastname: Roma
authors.affiliation: *Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels B-1200, Belgium.
authors.forename: Jessica
authors.initials: J
authors.lastname: Duprez
authors.affiliation: †Laboratory for Diabetes Cell Therapy, Institute for Research in Biotherapy, University Hospital St-Eloi, Montpellier 34295, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Broca
authors.affiliation: †Laboratory for Diabetes Cell Therapy, Institute for Research in Biotherapy, University Hospital St-Eloi, Montpellier 34295, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Wojtusciszyn
authors.affiliation: *Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels B-1200, Belgium.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Jonas
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D024483:Vitamin K 3 / Q000378:metabolism
chemical_list: D007328:Insulin; D017382:Reactive Oxygen Species; D009249:NADP; D024483:Vitamin K 3; D006861:Hydrogen Peroxide; D002374:Catalase; D005978:Glutathione; D005947:Glucose; D002118:Calcium