Molecular Mechanism Of Nobiletin To Alleviate Sarcopenia In D-galactose-induced Aging Mice

Skeletal muscle atrophy is a disease of age-related loss of skeletal muscle mass and function,also known as sarcopenia,which can impair exercise ability,increase the risk of fractures,diabetes,and other illnesses,and severely affect the quality of life of senior.However,no effective drugs are approved for clinical use to prevent or treat sarcopenia.Nobiletin(Nob)is a natural polymethylate flavonoid extracted from citrus peel,which has various biological functions,including antioxidant,anti-inflammatory,and anti-diabetic effects,as well as the ability to improve mitochondrial function and maintain metabolic homeostasis.D-galactose(D-gal)-induced oxidative stress and inflammation have been shown to mimic aging conditions and lead to sarcopenia.Here,we used D-gal to establish in vivo and in vitro sarcopenia models,whice were treated with Nob to systematically explore its effects of Nob on sarcopenia and its potential mechanisms,with the aim to provide theoretical support for the use of Nob for the prevention and treatment of sarcopenia.The main investigations and results are as follows:1.To clarify the effect of Nob on sarcopenia,we first used D-gal-induced C57BL/6J mice to establish a model of sarcopenia in vivo.The mice were injected subcutaneously for 10 weeks at a dose of 500 mg/kg/day,and subjected to gavage with Nob at a dose of 100 mg/kg/day to evaluated the effects of Nob on skeletal muscle mass and function in D-gal-induced aging mice.The results showed that,Nob significantly increased the body weight,lean mass and hindlimb muscle mass,and markedly enhanced muscle endurance and grip strength in D-gal-induced aging mice(P<0.05).Additionally,Nob significantly improved glucose tolerance,cold tolerance,and basal metabolic capacity in D-gal-induced aging mice(P<0.05).In summary,these results suggest that Nob improves skeletal muscle mass and function in D-gal-induced aging mice.2.To explore the effects of Nob on the skeletal muscle structure and components in D-gal-induced aging mice,we used the skeletal muscle as the research object to evaluate the effects of Nob on myofiber structure and components in different treatment groups.The findings demonstrated no significant difference in the number of myofibers among different treatment groups(P>0.05).Nob increased the main structural protein components of myofibers(actin,myosin,troponin complex and myosin heavy chain),improved the ultrastructure myofibers,and markedly increased the cross-sectional area of muscle fibers(15.16% increase)in D-gal-induced aging mice(P<0.05).3.To elucidate the mechanism underlying the Nob-mediated alleviation of sarcopenia in D-gal-induced aging mice,the skeletal muscle of mice in different treatment groups was used as the research object to explore the effects of Nob on the factors affecting skeletal muscle protein homeostasis.The results showed that,Nob intervention improved the mitochondrial structure of myofibers,significantly increased the production of ATP,decreased the production of ROS and MDA and inflammation levels,and enhanced the activity of antioxidant enzyme SOD in D-gal-induced aging mice.Additionally,Nob intervention improves skeletal muscle atrophy by activating the m TOR/AKT pathway to promote protein synthesis,and inhibited the expression of muscle-specific atrophy protein MAFbx/Mu RF1 to block protein degradation in D-galinduced aging mice.4.To further explore the molecular mechanism of Nob in alleviating D-gal induced sarcopenia.We used 20 g/L D-gal-induced C2C12 myoblasts to establish an in vitro model of sarcopenia and evaluated the effects of Nob on D-gal-induced C2C12 cell function and protein homeostasis.The findings demonstrated that,Nob treatment significantly improved autophagy,and mitochondrial function,increased ATP production,decreased ROS production,inhibited inflammation,and prevented cell senescence and apoptosis in D-gal-induced C2C12 cells.Additionally,Nob improved the myotube area by activating m TOR/AKT pathway to promote protein synthesis,and inhibiting the expression of MAFbx/Mu RF1 to block protein degradation in D-galinduced C2C12 cells(P<0.05).