eNOS and p38 MAPK, but not ROS levels, are involved in the protective effect of metformin. Cells were incubated for 24 h in the presence or absence of palmitate (125 μM), with or without metformin (500 μM), L-NAME (1 mM), SB203580 (10 μM), SP600125 (5 μM), AICAR (200 μM), Compound C (10 μM) or vehicle. (A) Metformin protects cells from lipoapoptosis, an effect that is lost upon co-incubation with L-NAME but is mimicked by SB203580 and SP600125. (B) 25 μM of carboxy-H2DCFDA was added to each well for 30 min and ROS levels were subsequently measured. Bars represent mean ± SEM. * p < 0.05 vs. control, # p < 0.05 vs. palmitate with Kruskal-Wallis one-way analysis of variance on ranks. n = 4 (A), n = 3 (B).