Theaflavins decrease skeletal muscle wasting in disuse atrophy induced by hindlimb suspension in mice

Abstract

We previously found that a single dose of theaflavins induced skeletal muscle metabolic changes. In this study, we examined the effect of theaflavins on disuse muscle atrophy model mice by hindlimb suspension. Mice were assigned to 4 groups; ground-vehicle, ground-theaflavins, suspension-vehicle, and suspension-theaflavins, dosed with theaflavins (250 mg/kg/day) for 2 weeks. The peak of myotube size of cross sectional area was significantly moved to the smaller side in the suspension-vehicle group compared with the ground-vehicle group, and these shifts were significantly reduced by the treatment with theaflavins in both soleus and extensor digitorum longus. The level of phosphorylated eukaryotic translation initiation factor 4E-binding protein (4EBP)-1, located downstream of the Akt/mTOR pathway, was significantly different between suspension-vehicle and suspension-theaflavins in soleus. The ratio of forkhead box O (FoxO) 3a to phosphorylated FoxO3a significantly increased in soleus or tended to rise in extensor digitorum longus of suspension-vehicle group compared with ground-vehicle. In contrast, these changes were not observed in suspension-theaflavins group. These results suggested that theaflavins inhibited the progress of disuse muscle atrophy through modulation of protein metabolism.

Keywords: FoxO3a; hindlimb suspension; skeletal muscle atrophy; theaflavins.

Fig. 1

The evaluation of skeletal muscle atrophy induced by hindlimb suspension with or without theaflavins; representative myofiber cross section of SOL stained with HE (A) and distribution of cross-sectional area of SOL (B). Statistical analyses were performed by Wilcoxon and Mann-Whitney U tests (Table 2).

Fig. 2

The evaluation of skeletal muscle atrophy induced by hindlimb suspension with or without theaflavins; representative myofiber cross section of EDL stained with HE (A) and distribution of cross-sectional area of EDL (B). Each value represents mean and SD (n = 6, each). Statistical analyses were performed by Wilcoxon and Mann-Whitney U tests (Table 2).

Fig. 3

Ratio of phosphorylated Akt to Akt, phosphorylated 4EBP-1 to 4EBP-1, FoxO 3a to phosphorylated FoxO and ubiquitin of SOL. Each value represents mean and SD (n = 6, each). Statistical analyses were performed by two-way ANOVA followed by Dunnett’s test. Significant differences between experimental groups; *p<0.05.

Fig. 4

Ratio of phosphorylated Akt to Akt, phosphorylated 4EBP-1 to 4EBP-1, FoxO 3a to phosphorylated FoxO and ubiquitin of EDL. Each value represents mean and SD (n = 6, each). Statistical analyses were performed by two-way ANOVA followed by Dunnett’s test. Significant difference between experimental groups; *p<0.05.

Fig. 5

Possible mechanism of action of theaflavins on the disuse muscle atrophy.