Purpose: Green tea polyphenols have been reported to improve muscle function in dystrophic mice. The chemical structure of apple polyphenols (APP) is similar to that of tea polyphenols; however, their effects on muscle function have not been examined previously. We examined the effects of dietary intake of APP on gastrocnemius function in Wistar rats.
Methods: Sixteen male rats (11 wk old) were divided into two groups: the 4.8% APP diet group and the control group (N = 8 in each group). Before and after 3 wk of treatment, right-leg tetanic ankle torques were measured. Successive twitch torques (four sessions per minute for 2 min) were also measured to test indications of fatigue. Contralateral (left) legs were used for wet weight measurement and examination of mRNA expression.
Results: Total-body and muscle weights were similar in both the groups. The adipose tissue weight of the APP group was significantly lower than that of the control group (P < 0.05). The isometric torque of the APP group was significantly higher than that of the control group (P < 0.05). During the 2-min experimental period, the relative twitch torques (compared with the initial value) of the APP group were larger than those of the control group. Statistical significance was observed at 90, 105, and 120 s (P < 0.05). Expression of peroxisome proliferator-activated receptors α and δ - positive regulators of lipid oxidation - were significantly higher in the APP group than in the control group (P < 0.05).
Conclusion: We conclude that dietary APP enhance normal muscle function in Wistar rats. Alteration of lipid metabolism might be one of the mechanisms of this phenomenon.