Effects of tea polyphenols on brain structure and function of hippocampus in aged type 2 diabetes mellitus rats with anxiety and depression-like behavior.

OBJECTIVES

This study aimed to investigate changes in brain structure and function of hippocampus in aged type 2 diabetes mellitus (T2DM) rats and the effects of tea polyphenol (TP) intervention using magnetic resonance imaging (MRI) and tissue-level molecular analyses.

METHODS

Rats were randomly assigned to six groups: Control, Aged, Aged T2DM, Aged T2DM + TP, Aged T2DM + rosiglitazone, and Aged T2DM + piracetam intervention groups. Anxiety- and depression-like behaviors were assessed using the open field test, the forced swimming test and elevated plus maze. Brain structure, blood flow and neuro-associated metabolites were evaluated via MRI. The number of nerve cells, neurons, microglia and astrocytes, the expression of BDNF/CREB/p-CREB protein, the levels of inflammatory factors, and the integrity of the myelin sheath in the hippocampus were evaluated. Relationships between behavioral, cellular and molecular changes and MRI-derived indicators were evaluated by Pearson correlation analysis.

RESULTS

Aged T2DM rats exhibited severe anxiety- and depression-like behaviors accompanied by brain atrophy, reduced blood flow and decreased brain metabolites. At the microstructural level, the number of hippocampal neurons in the Aged T2DM group was significantly reduced, accompanied by increased counts of microglia and astrocytes. Meanwhile, the expression levels of hippocampal p-CREB and BDNF were decreased, the concentration of the inflammatory factor IL-1β, IL-6, TNF-α was elevated, and myelin integrity was impaired. Intervention with TP alleviated anxiety- and depression-like behavior, with MRI-detected abnormalities and in vitro histopathological molecular changes improved (except for myelin integrity).

CONCLUSION

TP intervention mitigated alterations in brain structure and function as well as anxiety and depression-like behaviors in aged T2DM rats.