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.

CONCLUSION:

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: Kang Liu, Wenwen Zhao, Xuejiao Gao, Fang Huang, Junping Kou, Baolin Liu
• Journal: Atherosclerosis (Atherosclerosis) Vol. 223 Issue 2 Pg. 350-8 (Aug 2012) ISSN: 1879-1484 [Electronic] Ireland
• PMID: 22766331 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Anti-Inflammatory Agents
• Endothelin-1
• IL6 protein, human
• IRS1 protein, human
• Inflammation Mediators
• Insulin Receptor Substrate Proteins
• Interleukin-6
• Plasminogen Activator Inhibitor 1
• SERPINE1 protein, human
• Tumor Necrosis Factor-alpha
• Palmitic Acid
• Nitric Oxide
• NOS3 protein, human
• Nitric Oxide Synthase Type III
• Proto-Oncogene Proteins c-akt
• I-kappa B Kinase
• IKBKB protein, human
• Diosgenin
• Salicylic Acid

Topics

• Animals
• Anti-Inflammatory Agents (pharmacology)
• Blotting, Western
• Cells, Cultured
• Diosgenin (pharmacology)
• Dose-Response Relationship, Drug
• Endothelin-1 (metabolism)
• Endothelium, Vascular (drug effects, enzymology, physiopathology)
• Enzyme-Linked Immunosorbent Assay
• Human Umbilical Vein Endothelial Cells (drug effects, enzymology)
• Humans
• I-kappa B Kinase (metabolism)
• Inflammation Mediators (metabolism)
• Insulin Receptor Substrate Proteins (metabolism)
• Insulin Resistance
• Interleukin-6 (metabolism)
• Microscopy, Fluorescence
• Nitric Oxide (metabolism)
• Nitric Oxide Synthase Type III (metabolism)
• Palmitic Acid (pharmacology)
• Phosphorylation
• Plasminogen Activator Inhibitor 1 (metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• Rats
• Rats, Sprague-Dawley
• Salicylic Acid (pharmacology)
• Signal Transduction (drug effects)
• Tumor Necrosis Factor-alpha (metabolism)
• Vasodilation (drug effects)