title: Protein kinase C-β contributes to impaired endothelial insulin signaling in humans with diabetes mellitus.
abstract: BACKGROUND
  Abnormal endothelial function promotes atherosclerotic vascular disease in diabetes. Experimental studies indicate that disruption of endothelial insulin signaling, through the activity of protein kinase C-β (PKCβ) and nuclear factor κB, reduces nitric oxide availability. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes mellitus.
  
  
  RESULTS
  We measured protein expression and insulin response in freshly isolated endothelial cells from patients with type 2 diabetes mellitus (n=40) and nondiabetic controls (n=36). Unexpectedly, we observed 1.7-fold higher basal endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 in patients with diabetes mellitus (P=0.007) without a difference in total eNOS expression. Insulin stimulation increased eNOS phosphorylation in nondiabetic subjects but not in diabetic patients (P=0.003), consistent with endothelial insulin resistance. Nitrotyrosine levels were higher in diabetic patients, indicating endothelial oxidative stress. PKCβ expression was higher in diabetic patients and was associated with lower flow-mediated dilation (r=-0.541, P=0.02). Inhibition of PKCβ with LY379196 reduced basal eNOS phosphorylation and improved insulin-mediated eNOS activation in patients with diabetes mellitus. Endothelial nuclear factor κB activation was higher in diabetes mellitus and was reduced with PKCβ inhibition.
  
  
  CONCLUSIONS
  We provide evidence for the presence of altered eNOS activation, reduced insulin action, and inflammatory activation in the endothelium of patients with diabetes mellitus. Our findings implicate PKCβ activity in endothelial insulin resistance.
authors.affiliation: Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Corey E
authors.initials: CE
authors.lastname: Tabit
authors.forename: Sherene M
authors.initials: SM
authors.lastname: Shenouda
authors.forename: Monica
authors.initials: M
authors.lastname: Holbrook
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Fetterman
authors.forename: Soroosh
authors.initials: S
authors.lastname: Kiani
authors.forename: Alissa A
authors.initials: AA
authors.lastname: Frame
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Kluge
authors.forename: Aaron
authors.initials: A
authors.lastname: Held
authors.forename: Mustali M
authors.initials: MM
authors.lastname: Dohadwala
authors.forename: Noyan
authors.initials: N
authors.lastname: Gokce
authors.forename: Melissa G
authors.initials: MG
authors.lastname: Farb
authors.forename: James
authors.initials: J
authors.lastname: Rosenzweig
authors.forename: Neil
authors.initials: N
authors.lastname: Ruderman
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Vita
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Hamburg
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D003925:Diabetic Angiopathies / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D008698:Mesylates / Q000494:pharmacology; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D011758:Pyrroles / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: C434605:5,21 - 12,17-dimetheneo-18H-dibenzo(i,o)pyrrolo(3,4-1)(1,8)diazacyclohexandecine-18,10(19H)dione,8((dimethylamino)methyl)-6,7,8,9,10,11-hexahydro,monomethanesulfonate; D007004:Hypoglycemic Agents; D007328:Insulin; D008698:Mesylates; D016328:NF-kappa B; D011758:Pyrroles; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D011493:Protein Kinase C; D064546:Protein Kinase C beta