Date Published: June 14, 2019
Publisher: Public Library of Science
Author(s): Mina Fujitani, Takafumi Mizushige, Fuminori Kawabata, Keisuke Uozumi, Machi Yasui, Kohsuke Hayamizu, Kenji Uchida, Shinji Okada, Bhattarai Keshab, Taro Kishida, Aldrin V. Gomes.
The promotion of muscle recovery after immobilization is important to preserve an optimum health status. Here, we examined the effect of dietary Alaska pollack protein (APP) on skeletal muscle weight after atrophy induced by hind limb immobilization using plaster immobilization technique. Rat left limb was casted with a wetted plaster cast under anesthesia. After 2 weeks of feeding, the cast was removed and the rats were divided into three groups, namely, a baseline group, high-fat casein diet group, and high-fat APP diet group. After 3 weeks of feeding, the skeletal muscles (soleus, extensor digitorum longus [EDL], and gastrocnemius) were sampled. The estimated weight gains of soleus, gastrocnemius, and EDL muscle in the immobilized limbs were significantly larger in the rats fed with APP diet as compared with those fed with casein diet. In soleus muscle, dietary APP increased the expression of Igf1 and Myog genes in the immobilized limbs after the recovery period.
A number of studies have found that unloading or reduced muscle activity induces significant muscle atrophy [1, 2]. Although skeletal muscle has an inherent capacity to recover from atrophy, the maintenance and recovery of muscle mass and function after disuse sometimes can be slow, inefficient and incomplete [3, 4]. Resistance exercise is not always relevant in specific physio-pathological situations. Thus, the advancement of alternative approaches to promote muscle recovery following disuse is important. Dietary approaches for the positive effects on muscle recovery after immobilization have been examined. Martin et.al. reported that recovery kinetics varied between diets and the diet supplemented with whey proteins promoted faster recovery of isometric force and concentric power output than a casein-rich diet using plaster immobilization technique, although muscle weight change was not observed . Magne et.al. and Savary-Auzeloux et al. reported that leucine supplementation to diet increased muscle weight in similar models [6, 7].
The weights of skeletal muscles were compared between unimmobilized and immobilized limbs in the baseline group at week 0 (Fig 2). Gastrocnemius and soleus muscle weights significantly decreased by immobilization. Estimated skeletal muscle weight gain during the recovery period of 3 weeks were compared between high-fat casein diet group and high-fat APP diet group to evaluate the dietary APP effect on muscle recovery. The estimated weight gains of soleus, gastrocnemius, and EDL muscle in the immobilized limbs were significantly larger in the rats fed with APP diet as compared with those fed with casein diet (19%, 26%, and 29% larger, respectively) (Fig 3). These three muscle weights in the immobilized limbs after recovery were significantly larger in the rats fed with APP diet as compared with those fed with casein diet (Table 2). Food intake, energy intake, and protein intake, of the rats fed with APP diet were significantly lower than that of the rats fed with casein diet, although no significant difference was observed between APP and casein groups in body weight gain (Table 2).
In our previous studies, dietary APP tended to increase gastrocnemius muscle weight without immobilization after 4 weeks of feeding with no significant difference and significantly increased gastrocnemius and EDL muscle weights after 8 weeks of feeding [8, 9]. In the present study, after immobilization, dietary APP intake significantly increased the estimated weight gains of in gastrocnemius, soleus, and EDL muscles as compared with casein intake during 3 weeks of the recovery period (Fig 3). This suggests that the effect of dietary APP on skeletal muscle would be strong in the recovery of atrophy than in the normal state. Although dietary APP significantly increased the estimated weight gains of these three muscle weights in contralateral unimmobilized limbs (S1 Fig), it is difficult to evaluate the stimulatory effects of APP on skeletal muscle in unimmobilized limbs because unimmobilized limbs could be over worked or otherwise effected by the immobilization of the other limb. The result suggests that dietary APP may exert the stimulatory effects on skeletal muscle weights, regardless of the degree of muscle disuse atrophy before its supplementation. Dietary APP supplementation may be an alternative approach to stimulate muscle recovery for patients being unable to perform physical exercise.