[Mechanism of tea polyphenols improving the sarcopenia in the aged type 2 diabetes model rats via mitochondrial quality control].

OBJECTIVE

To explore whether tea polyphenols(TP) improve sarcopenia in the aged type 2 diabetes(T2DM)model rats via mitochondrial quality control(MQC).

METHODS

A total of 55 2-month-old male SD rats were randomly divided into the control group(n=10), the aged model group(aged, n=10) and the aging T2DM model group(n=35). The aging T2DM model group rats were fed with high-sugar and high-fat diet and intraperitoneally injected with 50 mg/kg D-galactose daily. After 4 weeks, the aging T2DM model group rats were given a single intraperitoneal injection of 30 mg/kg streptozotocin(STZ). After STZ injection for 2 weeks, fasting blood glucose(FBG) ≥ 16.7 mmol/L was defined as successful T2DM model. When the model was successfully induced, the 30 model rats were randomly divided into aged T2DM group(Mod), 300 mg/kg TP teatment group(TP) and 3 mg/kg rosiglitazone treatment group(RSG) according to FBG, with 10 rats in each group. Each group was treated with 50 mg/kg D-galactose to induce senescence and fed with high glucose and fat for 8 weeks. Western blot was used to detect the expression of P53 protein in gastnemius muscle tissue of the model group at the end of the experiment, which was higher than that of the control group, indicating that the aging T2DM model was successfully established. FBG was detected by the blood glucose meter, gastnemius muscle relative weights was calculated, the microstructure of mitochondria of gastnemius muscle was observed by transmission electron microscope(TEM), the expression of mitochondrial biosynthesis-related proteins PGC-1α, mitochondrial dynamics-related proteins(OPA1, DRP1) and mitochondrial autophagy-related proteins(P62, LC3) in gastnemius muscle were detected by western blot.

RESULTS

Compared with the control group, the level of FBG and the expression of P53 in the Mod group were increased(P<0.01). The gastnemius muscle relative weights, the expression level of PGC-1α, OPA1 and the ratio of LC3II/LC3I were decreased(P<0.01). The expression level of P62 and DRP1 were significantly increased(P<0.01). The number of mitochondria decreased, the volume decreased and a large number of vacuolization, and there were no obvious autophagolysosomes and fission and fusion. After 8 weeks, compared with the Mod group, the number of mitochondria in the gastrocnemius of TP and RSG groups, vacuolization, fission and fusion were improved, and the autophagolysosomes was significantly increased. The expression levels of P53, DRP1 and P62, the level of FBG in the TP group were significantly decreased(P<0.01, P<0.05). The expression levels of OPA1 and PGC-1α, the ratios of LC3II/LC3I and gastnemius muscle relative weights were significantly increased(P<0.05, P<0.01).

CONCLUSION

TP can improve the sarcopenia in the aged T2DM model rats, and its mechanism is related to the regulation of mitochondrial quality control.