Effects of aerobic and resistance exercise training on leukemia inhibitory factor in skeletal muscles of aging mice

Abstract

Introduction Aging is an inevitable phenomenon in all living creature, deteriorating the body composition and physical activity capacity leading to mortality. Specially, age-related loss of muscle mass and strength are defined as Sarcopenia. Leukemia inhibitory factor, LIF, is not only known as a newly discovered myokine but also, an important player in skeletal muscle hypertrophy and regeneration following exercise and injury status. However, there is no study that reports a change of LIF expression in a chronic and regular exercise. As such, there was no relating study the expression of LIF during aging. Therefore, the purpose of this study is to investigate 12 weeks of resistance and aerobic exercise on expression of LIF in skeletal muscle of aging mice.

Methods Twenty 19 months old male C57BL/6 mice were randomly assigned to each of the following groups: OLD-CON, sedentary aging mice group (n=6)

OLD-AEX, 12 weeks of treadmill exercise group (n=7), OLD-REX, 12 weeks of resistance ladder climbing exercise group (n=7). Following 1 week of adaptation, OLD-AEX was performed for 12 weeks of forced treadmill exercise 3 days per week, and OLD-REX was performed for 12 weeks of resistance ladder climbing 3 days per week. During the intervention period, food intake was measured every week and grip strength and hanging tests were measured every two weeks. Body composition was measured by DXA (Dual Energy X-ray Absorptiometry) and LIF protein level was detected by using ELISA in each of muscle, including soleus (SOL), gastrocnemius (GAS), tibialis anterior (TA), and extensor digitorum longus (EDL). Western blotting analysis were performed to measure muscle pro-inflammatory factor, tumor necrosis factor-alpha (TNF- α) and interleukin-1 beta (IL-1β) in soleus muscle. Moreover, physical activity test was measured at the end of period.

Results There was no significant difference between groups in the body composition and weekly body weight change. The change of grip strength was significantly increased in OLE-AEX compare to OLD-CON. Muscle cross sectional area was significantly increased in OLD-AEX and OLD-REX compare to OLD-CON. The free weight hanging test was no significant difference between each groups, but weighted bearing hanging test was significantly increased in OLD-AEX compare to OLD-CON. Also, physical activity test was significantly increased in both of OLD-AEX and OLD-REX compare to OLD-CON. Both of OLD-AEX and OLD-REX LIF protein levels in SOL, EDL, and GAS were significantly decreased compare to OLD-CON. However, TA LIF protein level was significantly decreased in OLD-REX. In addition, there was a negative correlation between SOL LIF protein level and hindlimb lean mass. TNF- α and IL-1β protein expression in soleus muscle were no significant difference between each groups. Negative correlation was found between soleus muscle LIF protein level and hindlimb lean mass.

Conclusion 12 weeks of aerobic and resistance exercise training increased the grip strength, muscle cross sectional area, weighted hanging time, and physical activity. However, 12 weeks of aerobic and resistance exercise training decreased LIF protein levels in hindlimb muscle, and there was a negative correlation between soleus muscle LIF protein level and hinblimb lean mass.