Glucose-lowering activity of dark tea protein extract by modulating spleen-brain axis of diabetic mice.

The present study was to explore the glucose-lowering effects of the previously characterized dark tea (Camellia sinensis L) protein extract (DTPE) from Heimaojian on spleen-brain axis of diabetic mice. DTPE was orally administrated (50-100 mg/kg) to alloxan-induced mice for 21 days, biochemical assay and transcriptome profiling (RNA-Seq) were performed. The results showed that DTPE can improve glucose tolerance. Compared with model group, at day 21, the fasting blood glucose values were significantly (p<0.05) decreased by 44.9% (13.8 vs 7.6 mmol/L) and 51.4% (13.8 vs 6.7 mmol/L) for high dose of DTPE (100 mg/kg) and drug metformin (125 mg/kg) groups, respectively. Subsequently, transcriptome profiling (RNA-Seq) was performed on the spleen and brain of diabetic mice. Totally, 52 spleen-derived and 47 brain-derived differentially expressed genes related to the synthesis, transport and metabolism of glucose were identified. The regulatory network analysis indicated that DTPE may exert glucose-lowering effects through a 37-gene sub-network related to metabolism, Parkinson's disease, oxidative phosphorylation and immunity. In summary, for the first time, the present data revealed that dark tea-derived DTPE could exert a potential anti-hyperglycemic effect by modulating spleen-brain axis.