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

Abstract

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 (T ₁) intake groups were not significantly different compared with those in the control group; however, the high-concentration tannase-converted green tea extract (T ₂) 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 T ₁ groups (p < 0.05) and the expression levels in the T ₂ 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 T ₁ groups (p < 0.05) and the expression level in the T ₂ group (p < 0.01) were significantly different in the bicep femoris compared with that in the control group. Additionally, SOD gene expression in the T ₂ group was significantly increased (p < 0.05) in the soleus compared with that in the control, EC and T ₁ 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.

Figure 1

High-performance liquid chromatography chromatogram for catechins in green tea extract (a) and tannase-converted green tea extract under optimum extraction condition (b). GC, (–)-gallocatechin; EGC, (–)-epigallocatechin; EGCG, (–)-epigallocatechingallate; EC, (–)-epicatechin; GCG, (–)-gallocatechingallate; ECG, (–)-epicatechingallate.

Figure 2

Effects of tannase-treated catechin on (a) bone mass, (b) bone mineral content, (c) bone mineral density, (d) bone area, and (e) bone volume in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05  according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle concentration tannase-converted green tea extract (20 mg/kg); T₂: high concentration tannase-converted green tea extract (40 mg/kg).

Figure 3

Effects of tannase-treated catechin on (a) fat, (b) fat percent, and (c) lean mass in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05  according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg).

Figure 4

Effects of tannase-treated catechin on mRNA levels of (a) MyoD, (b) Myf5, and (c) myogenin in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05 according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle-concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg); MyoD: myoblast determination protein; Myf5: myogenic factor 5.

Figure 5

Effects of tannase-treated catechin on mRNA levels of (a) FOXO1 and (b) FOXO3 in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05 according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle-concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg); FOXO1-3: forkhead box protein O1-3.

Figure 6

Effects of tannase-treated catechin on mRNA levels of (a) SOD, (b) CAT, and (c) GST in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences atp < 0.05 according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg); SOD: superoxide dismutase; CAT: catalase; GST: glutathione S-transferase.

Figure 7

Effects of tannase-treated catechin on the protein expression of pS6K, mTOR, and follistatin in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05 according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg); pS6K: p70 S6 kinase; mTOR: the mammalian target of rapamycin.

Figure 8

Effects of tannase-treated catechin on the protein expression of FOXO3a, myostatin, MuRF-1, and atrogin-1 in aged mice. Each value represents the mean ± standard error (SE) for each group (n = 8). Different letters indicate significant differences at p < 0.05 according to Tukey's test. EC: epicatechin (2 mg/kg); T₁: middle-concentration tannase-converted green tea extract (20 mg/kg); T₂: high-concentration tannase-converted green tea extract (40 mg/kg); FOXO3a: forkhead box protein O3a; MuRF-1: muscle RING finger protein-1.