Study On The Mechanism Of LncRNA MAR1 In Aerobic Exercise Promoting Myogenic Differentiation In Sarcopenia Mice

Objective:Sarcopenia is a chronic disease associated with aging,the incidence of which is increasing globally every year,and the mechanisms by which exercise is an effective measure to delay Sarcopenia are unclear.This study will investigate the effects of aerobic exercise on Sarcopenia and the key regulatory mechanisms of lncRNA MAR1 in this process,as well as the effects of aerobic exercise on genes and proteins related to myogenic differentiation,and then elucidate the possible mechanisms of aerobic exercise in delaying Sarcopenia.Methods:Twelve 8-week-old SPF-grade male mice（C57BL/6）were randomly divided into a young control group（YC,n=6）and a young exercise group（YE,n=6）,and twelve 19-month-old mice were randomly divided into an aging control group（AC,n=6）and an aging exercise group（AE,n=6）.Both the YE and AE groups were trained for 12weeks with treadmills（incline 6%,14m/min,30min/d,5d/w）.At the end of the experiment,the body weight of the mice was recorded and the gastrocnemius muscles were weighed after taking both sides;The grip strength of the hind limbs was measured with an electronic dynamometer,and the mice were tested for hanging time using the upside-down test;The morphology of the muscle fibers was observed using HE staining and the cross-sectional area of the muscle fibers was calculated;The levels of lncRNA MAR1,miR-487b,Wnt5a,myogenic differentiation factor（Myo D）,myogenin（Myo G）,myocyte enhancer factor 2C（MEF2C）and myogenic factor 5（Myf5）m RNA were measured by RT-q PCR;The levels of Wnt5a,Myo D,Myo G,MEF2C and Myf5 proteins expression levels were measured by Western blot.Results:1.Compared with the YC group,the AC group showed an increase in body weight and a decrease in muscle mass and muscle index（P<0.05）and showed muscle atrophy;After 12 weeks of exercise,the AE group had increased muscle weight and muscle index compared to the AC group（P<0.05）;The YE group had slightly increased muscle mass and muscle index compared to the YC group,but there was no obvious difference（P>0.05）.2.Compared with the YC group,mice in the AC group showed reduced muscle strength,reduced grip strength in the hind limbs and significantly reduced hanging time（P<0.05）;After 12 weeks of exercise,the AE group showed increased muscle strength,increased grip strength in the hind limbs and longer hanging time compared with the AC group（P<0.05）;The YE group showed a slight increase in muscle strength and hanging time in the hind limbs compared with the YC group,but there was no significant difference（P>0.05）.3.Compared with the YC group,the muscle fibers in the AC group were disordered,with different sizes and morphologies of the myocytes,and the nuclei were more internally displaced,and the muscle cross-sectional area decreased（P<0.05）;After 12weeks of exercise,the muscle fibers in the AE group were neatly arranged,with less variation in cell size and morphology,less inward migration of nuclei,and an increase in muscle cross-sectional area compared to the AC group（P<0.05）;The muscle cross-sectional area of YE group was slightly larger than that of YC group,but there was no marked difference（P>0.05）.4.The levels of each molecule of lncRNA MAR1/miR-487b/Wnt5a signaling pathway were detected.LncRNA MAR1 and Wnt5a levels were significantly decreased and miR-487b levels were significantly increased in the AC group compared to the YC group（p<0.05）;After exercise training,lncRNA MAR1 and Wnt5a levels were significantly increased and miR-487b levels were significantly decreased in the AE group compared to the AC group（p<0.05）;While no significant changes were observed in the YE and YC groups（p>0.05）.5.The m RNA and protein expression of myogenic differentiation-related factors（Myo D,Myo G,MEF2C,Myf5）were found to be decreased in the AC group compared to the YC group（p<0.05）after detection by PCR and WB;After aerobic exercise training,m RNA and protein expression of myogenic differentiation-related factors（Myo D,Myo G,MEF2C,Myf5）were increased in the AE group compared to the AC group（p<0.05）;While there was no significant change in the YE group compared to the YC group（p>0.05）.Conclusion:1.Naturally aging mice have reduced muscle weight,decreased strength and muscle cross-sectional area compared to younger control mice,and these changes can be reversed by aerobic exercise.2.Aerobic exercise may alleviate Sarcopenia by down-regulating lncRNA MAR1levels and participating in the regulation of myogenic differentiation via the lncRNA MAR1/miR-487b/Wnt5a signaling pathway.3.Aerobic exercise may alleviate Sarcopenia by upregulating Wnt5a and activating m RNA and protein expression of myogenic regulatory factors through the Wnt5a/Ca²⁺signaling pathway to enhance the differentiation of myogenic cells.