Dietary Alaska pollack protein improves skeletal muscle weight recovery after immobilization-induced atrophy in rats

Abstract

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.

Fig 1. Schedule of rat feeding during immobilization and recovery periods.

Left limb was immobilized at knee joint by a plaster and the rats were fed with high-fat casein diet for 2 weeks. After cast removal, five rats were sacrificed (baseline group). The rats were fed with either high-fat casein diet (Cas, n = 14) or high-fat APP diet (APP, n = 14) for the recovery period of 3 weeks and then sacrificed.

Fig 2. Skeletal muscle weights in baseline group.

The weights of soleus, gastrocnemius, and extensor digitorum longus (EDL) muscles in unimmobilized (Unimmob) and immobilized (Immob) limbs from baseline group (n = 4–5) after the immobilization period are shown. Data are expressed as mean ± standard error of mean (SEM). Asterisks indicate significant differences as compared to unimmobilized limbs by Student’s paired t-test. **P < 0.01.

Fig 3. Estimated skeletal muscle weight gains in immobilized limbs during recovery period.

The estimated weight gains of soleus, gastrocnemius, and extensor digitorum longus (EDL) muscles in immobilized limbs of high-fat casein diet group (Cas, n = 14) and high-fat APP diet group (APP, n = 14) during the recovery period are shown. The gains in skeletal muscle weight during the recovery period were estimated according to the following equation: Δskeletal muscle weight = (skeletal muscle weight at week 3 in Cas or APP group)—(average skeletal muscle weight at week 0 in baseline group). Data are expressed as mean ± standard error of mean (SEM). Statistical analysis was performed between Cas and APP group with the Student’s unpaired t-test. *P < 0.05, **P < 0.01.