Investigating metabolic characteristics of type 2 diabetes mellitus-related cognitive dysfunction and correlating therapeutic effects of Di Dang Tang in animal models

Ethnopharmacological relevance: Di Dang Tang is a classic formula from Shang Han Lun, originally used to treat conditions such as blood stasis and heat accumulation. It is widely applied in the treatment of diabetes and its complications, but its effects on Type 2 Diabetes Mellitus-related Cognitive Dysfunction (T2DM-CD) remain unclear. Aim of the study: The study aimed to investigate the metabolic characteristics of patients with T2DM-CD. Additionally, it sought to evaluate the effects of Di Dang Tang on cognitive function in T2DM-CD model rats by targeting the metabolic pathways identified in the clinical analysis, exploring the underlying mechanisms through animal experiments. Methods: Fasting venous serum was collected from patients with Type 2 Diabetes Mellitus (T2DM) to detect metabolism-related products, and KEGG annotation analysis was performed. Separately, thirty rats were randomly divided using a random number table method, with six rats selected as the blank control group. Twenty-four successfully modeled rats were then randomly divided into the model group and three Di Dang Tang groups (low, medium, and high doses). After administering the medication, the relevant indicators in the rats were assessed. Results: Clinical metabolomics detected 32 key differential metabolites between the T2DM-CD and the blank control groups. Between the T2DM-CD and T2DM groups, 29 key differential metabolites were identified. In animal experiments, blood glucose levels in the model group were significantly higher compared to the blank control group at the same time points, whereas the high dose groups of Di Dang Tang exhibited reduced blood glucose levels at weeks 6 and 8 relative to the model group. In the Morris water maze test, the model group had longer escape latencies than the blank control group. The medium and high dose groups of Di Dang Tang showed shorter latencies. Additionally, compared to the model group, the Di Dang Tang groups spent more time and covered more distance in the target quadrant but had reduced average proximity and fewer platform entries. HE staining observation of the hippocampal CA1 area showed no apparent pathological changes in the blank group, obvious pathological damage in the model group, and no significant pathological changes in the medium and high dose groups of Di Dang Tang. Compared to the blank control group, the model group showed significant increases in the levels of Arachidonic Acid (AA), Ceramide (Cer), Glutamate (Glu), TNF- alpha, IL-1 beta, TG, and LDL-C, and a significant decrease in HDL-C levels. Compared to the model group, the groups of Di Dang Tang significantly modulated the levels of the above indicators. In Western Blot (WB) assays, compared to the blank control group, the model group rats exhibited significantly higher levels of cPLA2, PKC, ERK, and JNK , and significantly lower levels of claudin-5, NMDA, CaMKII, CREB, and BDNF. The Di Dang Tang groups significantly altered the levels of the above indicators compared to the model group. Conclusion: Amino acid metabolism, sphingolipid signaling pathways, glycerophospholipid metabolism, and various signaling pathways play significant roles in the pathogenesis of T2DM-CD. Di Dang Tang can improve learning and memory abilities in T2DM model rats and ameliorate cognitive impairments, potentially by regulating metabolic levels and inflammatory responses.