TNF and Cerebral ischemia: In addition, sham operation failed to produce the significant change of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels in metabolic syndrome rats with cerebral ischemia but MCAO significantly increased the levels of both substances mentioned earlier in the hippocampus (P value < 0.001 all, compared to the HCHF+sham operation+vehicle group).