(A) S6K activity was assayed in the MBH of rats fed NC or HFD for 1 d. (B) At 12 d after MBH cannulation, rats fed NC or HFD for 1 d were fasted for 5 h and injected with 0, 4, or 40 μU insulin for 5 min. After 40 min, the MBH was harvested and processed for S6K assay. (C) Rats were fed HFD for 0, 1, 3, or 7 d. On the last day, all rats were fed 20 g NC or HFD. After 5 h of fasting, the MBH was harvested and processed for S6K assay. *P < 0.05 versus NC.