**6. Conclusion**

In this study, the accumulated data led to the conclusion that although cognitive decline and brain mitochondrial dysfunction were observed in obese-insulin-resistant rats, AD was not developed during the pre-diabetic state. In addition, markers indicating the presence of AD were observed in T2DM subjects. Treatment with antidiabetic drugs, traditional medicine, FGF21, and mitochondrial fission inhibitors effectively improved brain mitochondrial function and cognitive function in rats with induced MetS.
