title: Sirtuin3 Dysfunction Is the Key Determinant of Skeletal Muscle Insulin Resistance by Angiotensin II.
abstract: BACKGROUND
  Angiotensin II promotes insulin resistance. The mechanism underlying this abnormality, however, is still poorly defined. In a different setting, skeletal muscle metabolism and insulin signaling are regulated by Sirtuin3.
  
  
  OBJECTIVE
  Here, we investigate whether angiotensin II-induced insulin resistance in skeletal muscle is associated with Sirtuin3 dysregulation and whether pharmacological manipulation of Sirtuin3 confers protection.
  
  
  METHODS
  Parental and GLUT4-myc L6 rat skeletal muscle cells exposed to angiotensin II are used as in vitro models of insulin resistance. GLUT4 translocation, glucose uptake, intracellular molecular signals such as mitochondrial reactive oxygen species, Sirtuin3 protein expression and activity, along with its downstream targets and upstream regulators, are analyzed both in the absence and presence of acetyl-L-carnitine. The role of Sirtuin3 in GLUT4 translocation and intracellular molecular signaling is also studied in Sirtuin3-silenced as well as over-expressing cells.
  
  
  RESULTS
  Angiotensin II promotes insulin resistance in skeletal muscle cells via mitochondrial oxidative stress, resulting in a two-fold increase in superoxide generation. In this context, reactive oxygen species open the mitochondrial permeability transition pore and significantly lower Sirtuin3 levels and activity impairing the cell antioxidant defense. Angiotensin II-induced Sirtuin3 dysfunction leads to the impairment of AMP-activated protein kinase/nicotinamide phosphoribosyltransferase signaling. Acetyl-L-carnitine, by lowering angiotensin II-induced mitochondrial superoxide formation, prevents Sirtuin3 dysfunction. This phenomenon implies the restoration of manganese superoxide dismutase antioxidant activity and AMP-activated protein kinase activation. Acetyl-L-carnitine protection is abrogated by specific Sirtuin3 siRNA.
  
  
  CONCLUSIONS
  Our data demonstrate that angiotensin II-induced insulin resistance fosters mitochondrial superoxide generation, in turn leading to Sirtuin3 dysfunction. The present results also highlight Sirtuin3 as a therapeutic target for the insulin-sensitizing effects of acetyl-L-carnitine.
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Macconi
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Perico
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Lorena
authors.initials: L
authors.lastname: Longaretti
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Morigi
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri, Clinical Research Center for Rare Diseases "Aldo e Cele Daccò", Via Camozzi 3, 24020 Ranica, Bergamo, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Cassis
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Buelli
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri, Clinical Research Center for Rare Diseases "Aldo e Cele Daccò", Via Camozzi 3, 24020 Ranica, Bergamo, Italy.
authors.forename: Norberto
authors.initials: N
authors.lastname: Perico
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy; Unit of Nephrology and Dialysis, Azienda Ospedaliera Papa Giovanni XXIII, Piazza OMS 1, 24127 Bergamo, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Remuzzi
authors.affiliation: IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", Centro Anna Maria Astori, Science and Technology Park Kilometro Rosso, Via Stezzano 87, 24126 Bergamo, Italy.
authors.forename: Ariela
authors.initials: A
authors.lastname: Benigni
mesh_terms: D000108:Acetylcarnitine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D007333:Insulin Resistance; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D056566:Sirtuin 3 / Q000502:physiology*
chemical_list: D017382:Reactive Oxygen Species; D000804:Angiotensin II; D000108:Acetylcarnitine; D056566:Sirtuin 3