(A) Increased levels of total and individual ceramide species in response to SPTLC1 and SPTLC2 overexpression in AC16 cells (n = 4). (B) Increased cellular apoptosis in response to SPTLC1 and -2 overexpression compared with controls. Percentage of apoptotic cells quantified by annexin-V staining (n = 4, 20×). (C) Analysis of cellular oxidative metabolism by Seahorse analysis. Oxygen consumption rates were measured continuously throughout the experimental period starting at baseline and after addition of oligomycin (Oligo, 1 μM) and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FFCP1, 1 μM). Rot, rotenone; anti, antimycin. (D) Averaged data of basal respiration, ATP turnover, H+ leak, and respiratory capacity in AC16 cells in response to SPTLC1 and SPTLC2 overexpression and controls (n = 3). (E) Cellular ceramide levels in AC16 cells in response to myriocin treatment (n = 5–8 per group). Two-tailed Student’s t test was used for 2 group comparisons ,and one-way ANOVA was used for 3 group comparisons (*P < 0.05, **P < 0.01, ***P < 0.001 versus control).