Tetrandrine down-regulates expression of miRNA-155 to inhibit signal-induced NF-κB activation in a rat model of diabetes mellitus.

AIMS: This study is to investigate expression of miRNA-155 and the related signaling pathway in a rat model of diabetes mellitus (DM). METHODS: Thirty-six SD rats were divided into control, DM, and tetrandrine groups. A rat model of DM was constructed by tail vein injection with alloxan. Levels of related cytokines in serum samples were detected. The mRNA levels of IκBα and TNF-α in pancreatic islet tissues were detected by real-time PCR. Protein expression of IκBα and TNF-α was detected by western blotting. Expression of miRNA-155 in pancreatic islet tissues and serum samples was detected by real-time PCR. RESULTS: Compared with those in the control and the tetrandrine groups, activities of methane dicarboxylic aldehyde and reactive oxygen species in serum samples and pancreatic islet mitochondria tissues in the DM group were increased (P < 0.05), while activity of superoxide dismutase in the DM group was decreased (P < 0.05). Activities of haemoglobin A1c and glucose in serum samples in the DM group were increased, while insulin in the DM group was decreased (P < 0.05). The mRNA and protein levels of IκBα in pancreatic islet tissues in the DM group were decreased (P < 0.05), while the mRNA and protein levels of TNF-α in the DM group were increased (P < 0.05). Expression of miRNA-155 in pancreatic islet tissues and serum samples in the DM group was increased (P < 0.05). CONCLUSION: Tetrandrine prevented injury in rat pancreatic islet caused by alloxan, which was related with decreased oxidative stress, down-regulated miRNA-155 and decreased TNF-α in the NF-κB signaling pathway. These results indicate that tetrandrine plays an important role in DM by regulating expression of miRNA-155.