Abstract 17412: Induction of Endoplasmic Reticulum (ER) Stress in Endothelial and Peripheral Mononuclear Cells Isolated From Healthy Adults After Intravenous Lipid Infusion
Introduction: Endoplasmic reticulum (ER) stress has been demonstrated in atherosclerosis susceptible endothelium and in monocytes and macrophages of atherosclerotic plaques in humans. Initially ER stress plays an adaptive role, but more prolonged activation can signal apoptosis. Insulin resistant states, including obesity and diabetes type 2 are characterized by elevated basal and post-prandial free fatty acids (FFA), which are known to induce ER stress in experimental models.
Objective: To study ER stress in endothelial and peripheral blood mononuclear cells (PBMCs) of healthy adults after acute elevation of free fatty acids.
Methods: 12 healthy human subjects with no risk factors for cardiovascular disease were recruited. Peripheral mononuclear and venous endothelial cells were isolated before and after 5 hours of intravenous administration of a triglyceride emulsion (10% Intralipid) with heparin, which mimics post-prandial dyslipidemia. Levels of triglycerides, FFA, total cholesterol, HDL, glucose and insulin were measured before and after the infusion. Real time PCR was performed to quantify the expression of ER-stress related genes. Quantitative immunofluorescence and confocal microscopy were performed to evaluate expression of ER stress proteins.
Results: Triglycerides, FFA and glucose increased and HDL and insulin decreased post-Intralipid. In PBMCs ATF6 and spliced XBP-1 gene expression increased by 2.0 and 2.5 fold respectively (both P<0.05), while CHOP and GADD34 decreased by approximately 67% and 74% respectively (both P<0.01) with similar changes at the protein level. Moreover, confocal microscopy revealed that ATF6 post-Intralipid was localized in the nucleus of PBMCs, suggesting activation. In endothelial cells the protein levels of ATF6 and phosphorylated IRE1 increased by 45% and 23% respectively (both P<0.05).
Conclusions: As ATF6 and IRE1 mainly participate in the early adoptive response and CHOP and GADD34 induce apoptosis, our results suggest that elevated FFA for 5 hours can trigger a protective ER stress response in PBMCs and endothelial cells of healthy adults. These data provide insight on the role of FFA and ER stress in the function of mononuclear and endothelial cells in insulin resistant states in humans.
- © 2013 by American Heart Association, Inc.