title: Insulin Signaling in Bupivacaine-induced Cardiac Toxicity: Sensitization during Recovery and Potentiation by Lipid Emulsion.
abstract: BACKGROUND
  The impact of local anesthetics on the regulation of glucose homeostasis by protein kinase B (Akt) and 5'-adenosine monophosphate-activated protein kinase (AMPK) is unclear but important because of the implications for both local anesthetic toxicity and its reversal by IV lipid emulsion (ILE).
  
  
  METHODS
  Sprague-Dawley rats received 10 mg/kg bupivacaine over 20 s followed by nothing or 10 ml/kg ILE (or ILE without bupivacaine). At key time points, heart and kidney were excised. Glycogen content and phosphorylation levels of Akt, p70 s6 kinase, s6, insulin receptor substrate-1, glycogen synthase kinase-3β, AMPK, acetyl-CoA carboxylase, and tuberous sclerosis 2 were quantified. Three animals received Wortmannin to irreversibly inhibit phosphoinositide-3-kinase (Pi3k) signaling. Isolated heart studies were conducted with bupivacaine and LY294002-a reversible Pi3K inhibitor.
  
  
  RESULTS
  Bupivacaine cardiotoxicity rapidly dephosphorylated Akt at S473 to 63 ± 5% of baseline and phosphorylated AMPK to 151 ± 19%. AMPK activation inhibited targets downstream of mammalian target of rapamycin complex 1 via tuberous sclerosis 2. Feedback dephosphorylation of IRS1 to 31 ± 8% of baseline sensitized Akt signaling in hearts resulting in hyperphosphorylation of Akt at T308 and glycogen synthase kinase-3β to 390 ± 64% and 293 ± 50% of baseline, respectively. Glycogen accumulated to 142 ± 7% of baseline. Irreversible inhibition of Pi3k upstream of Akt exacerbated bupivacaine cardiotoxicity, whereas pretreating with a reversible inhibitor delayed the onset of toxicity. ILE rapidly phosphorylated Akt at S473 and T308 to 150 ± 23% and 167 ± 10% of baseline, respectively, but did not interfere with AMPK or targets of mammalian target of rapamycin complex 1.
  
  
  CONCLUSIONS
  Glucose handling by Akt and AMPK is integral to recovery from bupivacaine cardiotoxicity and modulation of these pathways by ILE contributes to lipid resuscitation.
authors.affiliation: From the Department of Anesthesiology (M.R.F., K.K., R.R., A.Y., K.L., R.M., G.W.) and Department of Medicine (I.R., M.B.), and Neuroscience Program (M.R.F.), University of Illinois at Chicago, Chicago, Illinois; and Research and Development Service, Jesse Brown Veterans Affairs Medical Center (M.R.F., K.K., R.R., A.Y., K.L., I.R., G.W.), Chicago, Illinois.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Fettiplace
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kowal
authors.forename: Richard
authors.initials: R
authors.lastname: Ripper
authors.forename: Alexandria
authors.initials: A
authors.lastname: Young
authors.forename: Kinga
authors.initials: K
authors.lastname: Lis
authors.forename: Israel
authors.initials: I
authors.lastname: Rubinstein
authors.forename: Marcelo
authors.initials: M
authors.lastname: Bonini
authors.forename: Richard
authors.initials: R
authors.lastname: Minshall
authors.forename: Guy
authors.initials: G
authors.lastname: Weinberg
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D000762:Anesthesia Recovery Period; D000779:Anesthetics, Local / Q000633:toxicity*; D000818:Animals; D015153:Blotting, Western; D002045:Bupivacaine / Q000633:toxicity*; D066126:Cardiotoxicity / Q000378:metabolism; D004195:Disease Models, Animal; D004357:Drug Synergism; D005217:Fat Emulsions, Intravenous / Q000378:metabolism / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000187:drug effects / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000779:Anesthetics, Local; D005217:Fat Emulsions, Intravenous; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D055372:AMP-Activated Protein Kinases; D002045:Bupivacaine