FIGURE 3.

LPS stimulates FA uptake and incorporation into DAG and TAG. A, adding FA during the chase increased the retention of [³H]TAG. Cells were loaded with FA and [³H]oleate overnight, washed, and re-incubated for 96 h in cDMEM containing 25 μm palmitate and 50, 100, or 150 μm oleate. Open box, no LPS; closed box, LPS (5 ng/ml). n = 4, p < 0.0001, two-way analysis of variance. B, LPS stimulates FA uptake and incorporation into TAG. FA-loaded macrophages were incubated with or without LPS (5 ng/ml) for 18 h prior to adding nonradioactive palmitate (20 μm) and 1 μCi/ml [³H]palmitate. ³H dpm were measured in the lipid extract at each time point. n = 4. C, in the same experiments, LPS significantly increased the incorporation of [³H]palmitate into TAG. Symbols (as in A) show mean + 1 S.D. Similar results were obtained when [³H]oleate was used instead of [³H]palmitate (not shown). D, LPS stimulated incorporation of ¹⁴C from [¹⁴C]glucose into DAG and TAG. Bars show mean and the upper value from two experiments; n = 3–4 in each experiment, p < 0.001 for each comparison of control and LPS-exposed cells. E, after LPS exposure for 72 h, [¹⁴C]palmitate and [³H]oleate were still taken up and incorporated into TAG. Radiolabeled FA were added to washed cells in cDMEM containing 20 μm nonradioactive oleate and palmitate (4 nmol each/well). Cells were harvested for analysis 5 h later. F and G, after FA-loaded cells had been exposed to LPS or vehicle for 18 h, Tc (7.5 μm), [¹⁴C]palmitate (1 μCi/ml), and 20 μm unlabeled palmitate were added for 4 h. Tc prevented LPS-induced increases in fatty acid uptake (F) and palmitate incorporation into TAG (G). n = 4/group; similar results were obtained for palmitate incorporation into DAG and in two additional experiments. Mean + 1 S.D. *, p < 0.05; **, p < 0.01; ***, p < 0.001.