Tannase-Converted Green Tea Extract with High (−)-Epicatechin Inhibits Skeletal Muscle Mass in Aged Mice

The objective of this study was to investigate the effects of tannase-converted green tea extract on body composition, muscle oxidative stress-related factors, and differentiation-related factors. The mean bone-related parameters and body composition were determined by the live dual-energy X-ray absorptiometry (DEXA). Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to determine mRNA expression and protein levels, respectively. The results of total mass testing in the epicatechin control (EC) and middle concentration tannase-converted green tea extract (T1) intake groups were not significantly different compared with those in the control group; however, the high-concentration tannase-converted green tea extract (T2) group showed a significantly higher effect to the lean than that of all other groups (p<0.05). The results of the assay of muscle differentiation-related genes indicated that the expression levels in the EC and T1 groups (p<0.05) and the expression levels in the T2 group (p<0.01) were significantly different in the bicep femoris compared with that in the control group. The results of the SOD gene assay indicate that the expression levels in the EC and T1 groups (p<0.05) and the expression level in the T2 group (p<0.01) were significantly different in the bicep femoris compared with that in the control group. Additionally, SOD gene expression in the T2 group was significantly increased (p<0.05) in the soleus compared with that in the control, EC and T1 groups. Our results suggest that tannase-converted green tea extract prevents muscle loss and regulates the quantity and quality of muscle by the levels of antioxidant stress-related enzymes and muscle differentiation factors to a greater extent than the administration of epicatechin and middle dose green tea extract.