Curry B, Biggerstaff J, Zemel MB
We previously demonstrated that calcitriol and leucine modulate adipocyte cytokine production, with corresponding effects on monocyte-vascular endothelial cell adhesion in vitro and ex vivo and on monocyte CD11b and endothelial cell ICAM-1 expression. Recent evidence suggests that adipocyte derived microparticles (ADMs) may serve as a messenger system between adipose tissue and peripheral blood. Therefore, we tested the hypothesis that ADMs isolated from leucine treatment of 3T3-L1 adipocytes will reduce monocyte CD11b expression in fresh human blood. 3T3-L1 cultures were treated with vehicle (control) or 0.5 mM leucine for 48 hrs and the conditioned media (CM) was collected. ADMs were isolated by ultracentrifugation and samples of CM, supernatant fraction, and ADM fraction were incubated with fresh whole blood for 2 and 18 hrs. Monocyte CD11b expression was assessed using flow cytometry and results are presented as the percent of monocytes positive for CD11b ± SEM. After 2 hrs, monocyte CD11b+ decreased from 68.6 ± 3.4% (control) to 47.7 ± 7.6% in the presence of leucine CM, and the leucine ADMs recapitulated this effect. Similarly, leucine ADMs reduced monocyte CD11b+ from 72.1 ± 4.0% (control) to 48.4 ± 2.7% (p <0.05) following 18-hr incubation. These results suggest that leucine treatment of adipocytes reduces CD11b expression on fresh human monocytes and that ADMs mediate some of these effects.
Curry B, Biggerstaff J, Zemel MB. 2013. Effects of leucine and adipocyte derived microparticles on human peripheral blood monocyte CD11b expression. FASEB Journal 27:e46.