RESUMO
ObjectiveTo determine the mechanism of Yitangkang in correcting excessive apoptosis of skeletal muscle cells to improve insulin resistance （IR） by inhibiting the advanced glycation end product （AGE）/receptor for the advanced glycation end product （RAGE） signaling pathway. Method① In vitro experiments. Yitangkang-medicated serum was prepared. C2C12 cells were divided into a blank group， a model group， high-， medium-， and low-dose Yitangkang-medicated serum groups （40， 20， and 10 g·kg-1）， and a RAGE inhibitor group. The IR model was induced by palmitic acid in C2C12 cells except for those in the blank group. After the corresponding intervention methods were conducted，the cell viability and glucose consumption level of each group were determined. In addition，the apoptosis rate was determined using flow cytometry. The mRNA and protein expression levels of the important apoptotic proteins ［B-cell lymphoma 2 （Bcl-2）， Bcl-2-associated X protein （Bax）， p53， cysteinyl aspartate-specific protease-3 （Caspase-3）， and cysteinyl aspartate-specific protease-9 （Caspase-9）］ were determined using Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot. ② In vivo experiments. Ninety-six eligible Wistar rats were divided into a blank group， a model group， high-，medium-，and low-dose Yitangkang groups （40， 20， and 10 g·kg-1）， and a western medicine group （pioglitazone hydrochloride，1.35 mg·kg-1）. The IR model was induced using high-glucose and high-fat feed for diabetes combined with intraperitoneal injection of low-dose streptozotocin （STZ） in animals and verified by the hyperinsulinemic-euglycemic clamp （HEC） test. After the model was determined successfully， the rats in each group were given intragastric administration of drugs as required. Terminal deoxynucleotidyl transferase dUTP nick end labeling （TUNEL） assay was performed to determine the number of positive apoptotic cells in the skeletal muscle tissues of rats in each group，while Real-time polymerase chain reaction（Real-time PCR） and Western blot were performed to determine the mRNA and protein expression levels of the important apoptotic proteins Bcl-2， Bax， p53， Caspase-3， and Caspase-9. Result① In vitro experiments. compared with the blank group， the model groups showed increased apoptosis rate of C2C12 cells and decreased cell viability and glucose consumption （P<0.01）. Compared with the model group， the Yitangkang-medicated serum groups and the RAGE inhibitor group showed decreased apoptosis rate of C2C12 cells and increased cell viability and glucose consumption （P<0.01）. Compared with the blank group， the model group showed decreased expression levels of Bcl-2 mRNA and protein in C2C12 cells and increased mRNA and protein expression levels of Bax， p53， Caspase-3， and Caspase-9 （P<0.01）. Compared with the model group， the Yitangkang-medicated serum groups and the RAGE inhibitor group showed increased expression levels of Bcl-2 mRNA and protein in C2C12 cells （P<0.01） and decreased mRNA and protein expression levels of Bax， p53， Caspase-3， and Caspase-9 （P<0.05， P<0.01）. ② In vivo experiments. The number of positive apoptotic cells in the skeletal muscle tissues of rats in the model group significantly increased as compared with that in the blank group （P<0.01）. The number of positive apoptotic cells in the skeletal muscle tissues of rats in the Yitangkang groups and the western medicine group decreased as compared with that in the model group （P<0.01）. Compared with the blank group， the model group showed decreased expression levels of Bcl-2 mRNA and protein in skeletal muscle tissues of rats and increased mRNA and protein expression levels of Bax， p53， Caspase-3， and Caspase-9 （P<0.01）. Compared with the model group， the Yitangkang groups and the western medicine group showed increased expression levels of Bcl-2 mRNA and protein in skeletal muscle tissues of rats （P<0.01） and decreased mRNA and protein expression levels of Bax， p53， Caspase-3， and Caspase-9 （P<0.05， P<0.01）. The medium-dose Yitangkang showed a similar effect as RAGE inhibitor， and the effect was equivalent to that of pioglitazone hydrochloride. ConclusionYitangkang can inhibit skeletal muscle cell apoptosis by inhibiting the AGE/RAGE signaling pathway.
RESUMO
Objective To observe the effect of Chinese herbal compound Yitangkang on the expressions of advanced glyclation end-products (AGEs) and the receptor of advanced glyclation end-products mRNA(RAGE-mRNA) in rats with diabetic nephropathy(DN),and to discuss the mechanism of the formulas in the treatment of DN. Methods The rat model of DN were established by intraperitoneal injection of strepotozotocin(STZ). After 8 weeks intervention with medications, the expression of renal RAGEs mRNA was detected by Real-time PCR, renal RAGE by immunohistochemistry, and renal content of AGEs by spectrophotometry. Results Compared with normal control group, the expression of renal RAGEs mRNA and RAGEs in diabetic nephropathy rats were increased significantly(P<0.01). Compared with DN group, the expression of renal RAGEs mRNA and RAGEs in three doses Yitangkang groups and western medicine group were decreased significantly(P<0.01). Conclusion Chinese herbal compound Yitangkang could protect kidney of diabetic nephropathy rats,and the mechanism is related to its loweirng renal expression of RAGEs mRNA, RAGEs and AGEs content.