The results showed that 4‐day hyperglycemia plus 4‐day normoglycemia (HG(4d) + LG(4d)/CTL) treatment significantly suppressed mRNA levels of ZO1 and CLDN1, compared with the LG plus 4‐day normoglycemia (LG(4d) + LG(4d)/CTL) treatment. Here, CLDN1 is linked to Hyperglycemia.