Activation of leukocytes by postprandial lipemia in healthy volunteers

Activation of leukocytes is obligatory for inflammation and atherogenesis by adhering to the endothelium via specific ligands. Although in vitro studies have shown that triglycerides (TG) can activate leukocytes, it is unknown whether this occurs in vivo. Using flowcytometry, we studied the expression of leukocyte activation markers CD11A, CD11B, CD62L (all involved in endothelium adhesion) and CD66B (a neutrophil degranulation marker) during a 6 h fat challenge (50 g/m2) and a water test in 10 healthy males (52 +/- 3 years). After fat, neutrophil counts were increased between t=1 and t =6 h, with a maximum at t=3 h (+32% versus t=0, P <0.05), while they remained unchanged after water. Both tests showed gradual lymphocyte count increments. The expression of activation markers on lymphocytes was low and showed comparable responses after both tests. After fat, a significant increase up to a maximum at t=6 h was seen for CD11B on monocytes and on neutrophils for CD11B, CD62L and CD66B. Postprandial activation of monocytes and neutrophils was higher after fat than after water. The maximal postprandial TG increment was significantly related to the increase of CD11B on monocytes (Pearson's R=0.64, P <0.05). In conclusion, postprandially there is a TG-specific increase of neutrophil counts and increased activation of monocytes and neutrophils. These results are suggestive of a pro-inflammatory situation that may correspond with increased adhesive capacity of these cells contributing to the inflammatory component of atherosclerosis.