Protective effects of flavonoids in Coreopsis tinctoria Nutt. in a mouse model of type 2 diabetes

Coreopsis tinctoria Nutt., a popular tea drink used in the Xinjiang region of China, has been traditionally used to treat diabetes and chronic metabolic diseases in China, Portugal, and North America. The bioactive extraction and potential mechanism have not been fully elucidated until now.

Traditional herbal medicines usually share network targets due to multicomponent therapeutics. Therefore, we tried to explore the protective effects of C. tinctoria on diabetes and the related molecular mechanism.

A flavonoid-rich fraction of C. tinctoria (CTF) was prepared. After 15 weeks of continuous treatment with CTF, the blood glucose and blood lipid levels of experimental mice were evaluated. Tissue was collected for differentially expressed genes (DEGs), bioinformatics analysis, RT‒PCR and Western blot for target-related DEGs.

After 15 weeks of continuous treatment with CTF, db/db mice showed reversed levels of glucose, insulin, glucagon and glycated hemoglobin A1c. CTF treatment also regulated total cholesterol, triglycerides, low density lipoprotein, nonesterified fatty acid, alanine transaminase, and aspartate transaminase. Major metabolic pathways were found to be dysregulated in the liver using a combined analysis of transcriptomics and network pharmacology. CTF treatment regulated 48.2% of 6357 dysregulated genes in db/db mice. The mitochondrial electron transport chain and tricarboxylic acid cycle were mainly affected. The sequencing data showed that fifty-nine predicted target genes for CTF were reverse regulated. Together with 1528 coexpressed genes, these genes reflected the main characteristics of the whole perturbed transcriptomic profile, i.e., dysregulated mitochondrial metabolism. The important genes of the target and coexpressed genes were further verified at the gene and protein levels.

The results confirm that the metabolic changes induced by hyperglycemia are closely related to mitochondrial metabolism in the liver. CTF alters a core gene set that exerts regulatory effects at the biological pathway level in db/db mice. In conclusion, our data reveal that an important molecular event for CTF treatment is the regulation of mitochondrial metabolism and support the idea that herbs or natural compounds are potential therapeutic substances for mitochondrial dysfunction-related diabetes.