title: Insulin prevents mitochondrial generation of H₂O₂ in rat brain.
abstract: The mitochondrial electron transport system (ETS) is a main source of cellular ROS, including hydrogen peroxide (H₂O₂). The production of H₂O₂ also involves the mitochondrial membrane potential (ΔΨm) and oxygen consumption. Impaired insulin signaling causes oxidative neuronal damage and places the brain at risk of neurodegeneration. We evaluated whether insulin signaling cross-talks with ETS components (complexes I and F₀F₁ATP synthase) and ΔΨm to regulate mitochondrial H₂O₂ production, in tissue preparations from rat brain. Insulin (50 to 100 ng/mL) decreased H₂O₂ production in synaptosomal preparations in high Na(+) buffer (polarized state), stimulated by glucose and pyruvate, without affecting the oxygen consumption. In addition, insulin (10 to 100 ng/mL) decreased H₂O₂ production induced by succinate in synaptosomes in high K(+) (depolarized state), whereas wortmannin and LY290042, inhibitors of the PI3K pathway, reversed this effect; heated insulin had no effect. Insulin decreased H₂O₂ production when complexes I and F₀F₁ATP synthase were inhibited by rotenone and oligomycin respectively suggesting a target effect on complex III. Also, insulin prevented the generation of maximum level of ∆Ψm induced by succinate. The PI3K inhibitors and heated insulin maintained the maximum level of ∆Ψm induced by succinate in synaptosomes in a depolarized state. Similarly, insulin decreased ROS production in neuronal cultures. In mitochondrial preparations, insulin neither modulated H2O2 production or oxygen consumption. In conclusion, the normal downstream insulin receptor signaling is necessary to regulate complex III of ETS avoiding the generation of maximal ∆Ψm and increased mitochondrial H2O2 production.
authors.affiliation: Departamento de Bioquímica, ICBS, UFRG, Programa de Pós Graduação em Ciências Biológicas-Bioquímica, Rua Ramiro Barcelos, 2600 anexo, CEP 90035-003, Porto Alegre, RS, Brazil. alexandrep.muller@gmail.com
authors.forename: Alexandre Pastoris
authors.initials: AP
authors.lastname: Muller
authors.forename: Clarissa Branco
authors.initials: CB
authors.lastname: Haas
authors.forename: Juliana
authors.initials: J
authors.lastname: Camacho-Pereira
authors.forename: Andressa Wigner
authors.initials: AW
authors.lastname: Brochier
authors.forename: Jussânia
authors.initials: J
authors.lastname: Gnoatto
authors.forename: Eduardo Rigon
authors.initials: ER
authors.lastname: Zimmer
authors.forename: Diogo Onofre
authors.initials: DO
authors.lastname: de Souza
authors.forename: Antonio
authors.initials: A
authors.lastname: Galina
authors.forename: Luis Valmor
authors.initials: LV
authors.lastname: Portela
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000648:ultrastructure*; D002540:Cerebral Cortex / Q000166:cytology; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation / Q000187:drug effects; D018698:Glutamic Acid / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology*; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects; D013997:Time Factors
chemical_list: D007328:Insulin; D016877:Oxidants; D017382:Reactive Oxygen Species; D018698:Glutamic Acid; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide
keywords: Brain metabolism; H(2)O(2) production; Insulin signaling; Mitochondria