The Function Research Of Caloric Restriction In Senile Sarcopenia

Objective:With the aging of population,aging related diseases are getting more and more attention.China’s aging population is expected to rise to 35 percent by2050,making it the world’s oldest country.Sarcopenia has risen to be an important topic which is the potential risk factor for weak,disability and death of the elderly.The dicline of skeletal muscle stem cell self-renewal and differentiation ability play a key role in the development of sarcopenia.As we all know,Caloric restriction（CR）that reduces calorie intake by 20–50%without causing malnutrition is a classical anti-aging intervention,but the mechanism is unclear.Moreover,it is difficult in clinical application due to its hunger and difficulty.It is reported that the levels of Glucocorticoid（GC）are closely related to sarcopenia and aging.Therefore,the regulation of the local concentration of GC may be the key step in regulating the aging process.As a key enzyme that regulates GC activity in local tissues,the expression of 11 beta hydroxylated steroid dehydrogenase（11β-HSD1）in muscle tissue increases significantly during aging,which may play an important role in retarding senile sarcopenia by Caloric restriction.Thus,our study aims to clarify whether the caloric restriction can delay the sarcopenia in the elderly and the possible molecular mechanism.Methods:In vivo study,The C57BL/6J mice were randomly divided into the normal diet group and Caloric restriction group.Then we placed C57BL/6 mice on a calorically restricted diet（60%of the control diet）for 3 months initiated in 19 month old.To assess the changes of muscle,the Dual-energy X-ray was used to detect the body composition,acquire the mass of muscle lean mass.Mice grip strength was measureed by Holding power.The Gastrocnemius muscle and Tibialis anterio were dissected,using hematoxylin-eosin（H&E）staining to observe the cross-sectional area of muscle fiber size.In addition,the expression of the genes was determined by real time PCR,such as aging marker gene(P16^ink4a),muscle protein ubiquitin protein degradation ligase E3s（Atrogin-1,MuRF-1）,and inflammatory cytokines（TNFα）and 11βHydroxysteroid Dehydrogenase（11β-HSD1）.We further established a11β-HSD1 knockout mouse,compared with the same age wild mice,and observed the above indicators.In vitro research,the muscle stem cells of the control group,the caloric restriction mice and the 11β-HSD1 knockout mice were induced and differentiated.The gene expression of 11β-HSD1 and myosin heavy chain（Myosin heavy chains,MyHC）were measured by fluorescence quantitative PCR.Moreover,on the basis of inhibiting the differentiation of muscle stem cells by palmitic acid,11β-HSD1inhibitor BVT.2733 was used to intervene,the morphological changes of the cultured cells were observed and MyHC of the culture cells was detected by immunofluorescence staining.Results:After 3 months caloric restriction（from 19 month old to 22 month old）,the skeletal muscle fiber atrophy was improved,the mice grasping force was enhanced,the aging marker gene P16^ink4a decreased,the atrophy factor Atrogin-1 and MuRF-1decreased,and the inflammatory factor TNF alpha decreased.Our results also suggested that the expression of 11β-HSD1 genes of muscle tissue increased with aging.In response to CR,the expression of 11β-HSD1 genes decreased.The same phenomenons were observed on 11β-HSD1 knockout mice which delayed muscle aging,including increased grip strength,decreased aging marker,atrophy marker and inflammatory factors.At the same time,it was found that the differentiation ability of the muscle stem cells in the caloric restriction mice and 11β-HSD1 knockout mice increased,the differentiation marker MyHC of stem cells increased,the expression of 11β-HSD1decreased significantly.We also found 11β-HSD1 inhibtor（already synthesized）,can reverse differentiation ability of muscle stem cell treated with free fatty acid.Conclusions:These data indicated that Caloric restriction,a classical intervention that could delay the aging,effectively delay the senile Sarcopenia through increasing the differentiation of muscle stem cells.11β-HSD1 may be the target of caloric restriction.Accordingly,we synthesised the 11β-HSD1 inhibitor to develop caloric restriction mimetics in order to provide therapeutic target of anti-aging and delaying sarcopenia...