FIGURE 9.

Influence of amino acid availability on FFA-induced apoptosis is independent of ceramide. A, the influence of medium amino acids and de novo ceramide synthesis inhibition on intracellular palmitoyl-ceramide in H4IIEC3 cells. Ceramide was determined by GC-MS analysis as described under “Experimental Procedures.” Values are expressed as mean ± S.E. (n = 3). *, p < 0.05 for the comparison with untreated cells. B, effect of de novo ceramide synthesis inhibitors on apoptosis in palmitate-treated cells. Cells were incubated with either 1 mm cycloserine or 50 μm fumonisin-B1 under varying amino acid levels with or without 400 μm palmitate. DCF fluorescence and caspase-3/7 activity were measured. Values are expressed as mean ± S.E. (n = 4). Amino acid concentrations are expressed as a magnification ratio in comparison with physiological amino acids (2.15 mm). **, p < 0.01 for the comparison with each palmitate-untreated control (white bars).