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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2008;28:792.)
© 2008 American Heart Association, Inc.

Clinical and Population Studies

Leukocyte Activation by Triglyceride-Rich Lipoproteins

Arash Alipour; Antonie J.H. H.M van Oostrom; Alisa Izraeljan; Caroline Verseyden; Jennifer M. Collins; Keith N. Frayn; Thijs W.M. Plokker; Jan Willem F. Elte; Manuel Castro Cabezas

From the Department of Internal Medicine (A.A., A.J.H.H.M.v.O., C.V., M.C.C.), University Medical Center Utrecht, the Netherlands; the Department of Internal Medicine (A.A., J.W.F.E., M.C.C.), Sint Franciscus Gasthuis, Rotterdam, The Netherlands; the Department of Cardiology (A.J.H.H.M.v.O., T.W.M.P.), Sint Antonius Hospital, Nieuwegein, The Netherlands; and Nuffield Department of Clinical Medicine (A.I., J.M.C., K.N.F.), University of Oxford, England.

Correspondence to M. Castro Cabezas, MD, PhD, Department of Internal Medicine, Center for Diabetes and Vascular Medicine, St Franciscus Gasthuis Rotterdam, PO Box 10900, 3004 BA Rotterdam, The Netherlands. E-mail m.castrocabezas{at}sfg.nl

Objective— Postprandial lipemia has been linked to atherosclerosis and inflammation. Because leukocyte activation is obligatory for atherogenesis, leukocyte activation by triglyceride-rich lipoproteins (TRLs) was investigated.

Methods and Results— The expression of CD11b and CD66b after incubation with glucose and native and artificial TRLs (NTRL and ATRL) in vivo and in vitro was evaluated by flowcytometry. Oral fat loading tests showed an increased expression of CD11b on monocytes and neutrophils and CD66b on neutrophils. In 11 volunteers, postprandial leukocytes became enriched with meal-derived fatty acids ([1-¹³C]16:0) suggesting uptake of exogenous fat. ApoB binding on leukocytes measured by flowcytometry in 65 subjects was highest on neutrophils and monocytes suggesting adherence of apoB-containing lipoproteins. Physiological concentrations of TRLs showed 62% increased neutrophil CD11b and a dose-dependent increased monocyte CD11b up to 84% in vitro. Incubations with lipid emulsions in the hypertriglyceridemic range showed a 5-fold increased monocyte CD11b expression, which was higher than the positive control (fMLP), and a dose-dependent 2- to 3-fold increased neutrophil CD11b and CD66b. The oxidative scavenger DMTU decreased the neutrophil CD66b expression by 36%.

Conclusion— Acute hypertriglyceridemia is a leukocyte activator most likely by direct interaction between TRLs and leukocytes and uptake of fatty acids. TG-mediated leukocyte activation is an alternative proinflammatory and proatherogenic mechanism of hypertriglyceridemia in part associated to the generation of oxidative stress.

Leukocyte activation by TRLs by membrane-associated CD11b and CD66b was shown. Uptake of meal-derived fatty acids by leukocytes and apoB binding on neutrophils and monocytes was also demonstrated. Hypertriglyceridemia is a leukocyte activator most likely by binding of TRLs to leukocytes and uptake of dietary fatty acids.

Key Words: inflammation • atherosclerosis • leukocytes • triglycerides and flowcytometry