FIGURE 4.

Agonist exposure decreases lipolysis and etomoxir-inhibitable β-oxidation. A, TLR agonists decrease lipolytic activity in cell lysates. Macrophages were incubated for 48 h with or without LPS (5 ng/ml), PAM (1 μg/ml), or poly(I:C) (15 μg/ml), lysed, and assayed to measure their ability to release [³H]oleate from [³H]triolein. Bars show mean + 1 S.E. from three independent experiments, each with n = 3. Each agonist decreased lysate lipolytic activity relative to unstimulated control cells (p < 0.001 for all comparisons with control). B, LPS exposure decreases FA β-oxidation. Cells were loaded overnight with FA containing trace amounts of [³H]oleate and [³H]palmitate. They were then exposed to LPS (5 ng/ml) or media control for 18 h before they were washed; etomoxir (0.2 mm) was added to block mitochondrial FA uptake, and incubation was continued for 18–24 h. FA-loaded, LPS-exposed cells released less ³H₂O from retained [³H]oleate and [³H]palmitate than did FA-loaded cells (no LPS). Etomoxir blocked ³H₂O accumulation in the presence and absence of LPS. n = 4. C, Etomoxir-inhibitable ³H₂O accumulation in the media was significantly less in cells exposed to LPS. Mean + 1 S.D. of three independent experiments. D, etomoxir treatment increased the amount of ³H-fatty acid that was retained in TAG, with and without LPS exposure. Data are representative of three experiments, each with n = 4. E, etomoxir-induced lipid retention was confirmed by counting the lipid droplets in cells stained with Nile Red and DAPI. >200 cells were analyzed per condition in each of four experiments. Et, etomoxir. *, p < 0.05; **, p < 0.01; ***, p < 0.001.