LB039 - WHOLE-BODY RESISTANCE TRAINING USING WEIGHT PULLING ENHANCES SKELETAL MUSCLE MASS AND INDUCES MUSCLE-SPECIFIC ADAPTATIONS IN MTORC1 AND MTORC2 SIGNALING IN MICE

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LB039

WHOLE-BODY RESISTANCE TRAINING USING WEIGHT PULLING ENHANCES SKELETAL MUSCLE MASS AND INDUCES MUSCLE-SPECIFIC ADAPTATIONS IN MTORC1 AND MTORC2 SIGNALING IN MICE

K. Uemichi1,*, R. Mori2, S. Fujita2

1Research Organization of Science and Technology, 2College of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan

 

Rationale: The mechanistic target of rapamycin (mTOR) signaling pathway plays a central role in regulating skeletal muscle protein synthesis in response to exercise and nutrient availability. Two distinct mTOR complexes, mTORC1 and mTORC2, have both been implicated in the regulation of protein synthesis in rodent models of localized muscle contraction. However, the long-term adaptations in mTORC1 and mTORC2 signaling in response to whole-body resistance exercise remain unclear.

Methods: Weight Pulling (WP) is a mouse model of whole-body resistance exercise in which animals pull a weighted cart. Ten-week-old male C57BL/6J mice were assigned to either a control or WP group. WP mice performed 8-12 sets of exercise per session, three times per week, for 26 sessions. Skeletal muscle mass and mTOR signaling responses in forelimb and hindlimb muscles were analyzed.

Results: Maximum pulling capacity progressively increased throughout training. Compared with the control group, the WP group exhibited significantly greater muscle mass in the biceps brachii, triceps brachii, and soleus muscles. Phosphorylation of NDRG1 Thr346, an indicator of mTORC2 activity, was significantly elevated in forelimb muscles following WP, whereas 4E-BP1 Thr37/46, an mTORC1 downstream target, was unchanged. In the soleus, total abundance of mTORC1 signaling components, including S6K1, rpS6, and 4E-BP1, was significantly increased after WP training.

Conclusion: WP-induced whole-body resistance training increased muscle mass and was associated with muscle-specific adaptations in mTOR signaling. These findings suggest that whole-body resistance training may enhance mTORC1 signaling capacity in the soleus and activate mTORC2 signaling in forelimb muscles, although the magnitude and pattern of these adaptations differ among muscles.

Disclosure of Interest: None declared