Effect of HFD on phosphorylation of ERK (A), Akt (B), JNK (C), and IRS-1Ser307 (D). On the left, representative Western blots are shown. On the right, the densitometric analysis of phosphorylation level is shown. No differences were observed between controls at the different time points, which were thus considered as a single control group. Data are presented as mean ± SD. *P < 0.05 versus controls.