title: Diosgenin ameliorates palmitate-induced endothelial dysfunction and insulin resistance via blocking IKKβ and IRS-1 pathways.
abstract: OBJECTIVE
  We investigated whether diosgenin, a widely used steroidal sapogenin, exerted protection against palmitate (PA)-induced inflammation and insulin resistance in the endothelium.
  
  
  METHODS
  Human umbilical vein endothelial cells (HUVECs) were pretreated with diosgenin for 30 min, and then incubated with 100 μmol/L PA for 30 min or 24 h with or without insulin. IKKβ, p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, Akt and eNOS activation were determined by Western blot analysis. Levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), endothelin-1 (ET-1) and plasminogen activator inhibitor-1 (PAI-1) were measured with ELISA Kits. Intracellular nitric oxide (NO) was viewed with fluorescence microscopy. Effects of diosgenin on insulin-mediated vasodilation was investigated in the isolated rat aortic rings.
  
  
  RESULTS
  Diosgenin significantly reduced PA-enhanced IKKβ and NF-κB phosphorylation with inhibition of TNF-α and IL-6 production in endothelial cells at the concentrations of 0.1, 1 and 10 μmol/L, well demonstrating its anti-inflammatory activity in an IKKβ/NF-κB-dependent fashion. Meanwhile, diosgenin attenuated PA-induced serine phosphorylation (S307) of IRS-1 and restored IRS-1 tyrosine phosphorylation in response to insulin. The beneficial modulation of serine/tyrosine phosphorylation of IRS-1 by diosgenin contributed to the improvement of insulin signaling along PI3K/Akt/eNOS pathways and thereby increased insulin-mediated NO production. Salicylate (5 mmol/L), an inhibitor of IKKβ, showed similar activities as diosgenin. Diosgenin also remarkably inhibited ET-1 and PAI-1 production in the endothelial cells, and markedly restored the loss of insulin-mediated vasodilation in the presence of PA.
  
  
  CONCLUSIONS
  The above-mentioned evidence suggests that diosgenin ameliorated endothelial dysfunction involved in insulin resistance through an IKKβ/IRS-1-dependent manner, shows potential application in the treatment for the cardiovascular diseases including atherosclerosis.
authors: Department of Pharmacology of Chinese Materia Medica, China Pharmaceutical University, Longmian Road, Nanjing 211198, China.
authors: Kang
authors: K
authors: Liu
authors: Wenwen
authors: W
authors: Zhao
authors: Xuejiao
authors: X
authors: Gao
authors: Fang
authors: F
authors: Huang
authors: Junping
authors: J
authors: Kou
authors: Baolin
authors: B
authors: Liu
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002478:Cells, Cultured; D004144:Diosgenin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology; D004797:Enzyme-Linked Immunosorbent Assay; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D018836:Inflammation Mediators / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D019308:Palmitic Acid / Q000494:pharmacology*; D010766:Phosphorylation; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020156:Salicylic Acid / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000893:Anti-Inflammatory Agents; D019332:Endothelin-1; C508600:IL6 protein, human; C526292:IRS1 protein, human; D018836:Inflammation Mediators; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; D017395:Plasminogen Activator Inhibitor 1; C051321:SERPINE1 protein, human; D014409:Tumor Necrosis Factor-alpha; D019308:Palmitic Acid; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; D004144:Diosgenin; D020156:Salicylic Acid