Free fatty acids induce endothelial dysfunction and activate protein kinase C and nuclear factor-κB pathway in rat aorta.
BACKGROUND
Insulin resistance is associated with an inappropriate elevation of plasma free fatty acids (FFAs) and endothelial dysfunction. In this study, we asked if elevated circulating FFA levels led to impaired insulin signaling and endothelial dysfunction in-vivo via activation of PKC-mediated inflammatory pathways.


METHODS
Sprague-Dawley (S-D) rats were infused with 1) 20% intralipid+heparin (FFA group) or 2) saline alone (Control group) for 6h. The intact aorta thoracica and aorta abdominalis were then removed. Aortic rings were isolated and evaluated for endothelial-dependent and non-dependent relaxation in an organ bath. The activities of eNOS and PKC were measured in endothelial homogenates prepared from endothelial cells harvested from the aorta. The expression levels of insulin signaling molecules IRS-1, Akt, eNOS, ERK1/ERK2, PKC-α, NFκB-p65 subunit and IκB-α in rat aortic endothelium were determined by immunohistochemistry and Western blot.


RESULTS
Elevation of FFAs resulted in a 35.9% reduction in the response to acetylcholine (p < 0.01), a 26% decline in plasma NOx levels (p < 0.05), a 53% decrease in eNOS activity and a 34 ± 9% inhibition in IRS-1 tyrosine phosphorylation (p < 0.05). We also found a 46% decrease in Akt phosphorylation and a 36% decrease in eNOS phosphorylation. FFA-induced endothelial insulin resistance was associated with 82% increase in total membrane-associated PKC activity, a 1.7-fold increase in total PKC-α protein, 1.29-fold decrease in IκB-α expression levels and 1.47-fold increase in NF-κB p65 subunit expression in rat aortic endothelium.


CONCLUSIONS
The molecular mechanisms underlying FFA-induced endothelial insulin resistance and eNOS inhibition may provide an important link implicating the PKC and IκB-α/NF-κB pathways in FFA-mediated inhibition of vascular insulin signaling.
Li
Hua
H
Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu City, Sichuan Province, PR China.
Li
Hongliang
H
Bao
Yige
Y
Zhang
Xiangxun
X
Yu
Yerong
Y
D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D001011:Aorta / Q000378:metabolism*; D015153:Blotting, Western; D004655:Emulsions / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D005217:Fat Emulsions, Intravenous / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D006493:Heparin / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010743:Phospholipids / Q000494:pharmacology; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013024:Soybean Oil / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D000925:Anticoagulants; D004655:Emulsions; D005217:Fat Emulsions, Intravenous; D005230:Fatty Acids, Nonesterified; D020672:I-kappa B Proteins; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D010743:Phospholipids; C545823:soybean oil, phospholipid emulsion; D000072000:NF-KappaB Inhibitor alpha; D009569:Nitric Oxide; D014443:Tyrosine; D013024:Soybean Oil; D006493:Heparin; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D051571:Protein Kinase C-alpha