Molecular Diagnosis And Preliminary Intervention Of Sarcopenia Based On Metabolomics

Objective:With the aggravation of population aging,age-related diseases have become an important issue.Older adults,as a special group,have both health problems caused by single disease and geriatric syndrome caused by various factors.Sarcopenia is a geriatric syndrome which is characterized by age-related loss of muscle mass,low muscle strength,and/or low physical performance and is associated with multiple adverse health outcomes,such as falls,fractures,disability,hospitalizations,and even death.The gap in the field of molecular diagnosis of sarcopenia still exists due to the lack of effective laboratory indexes to diagnose sarcopenia around the world.Besides,because of the complex and unclear pathogenesis of sarcopenia,current strategies are mainly focused on nonpharmacological treatments.Exploring efficient therapeutic interventions for sarcopenia has always been the highlights and difficulties in this field.Metabolomics is a new omics technology following genomics,transcriptomics and proteomics,which can be used for qualitative and quantitative analysis of small molecular metabolites in biological samples such as cells,tissues and body fluids.Different from other omics technologies,metabolomics is located in downstream of gene and protein networks which is the best tool for determining phenotypes and can be utilized to identify disease-specific biomarkers and mechanisms.Thus,the aim of the present study was to identify metabolic changes and related metabolic pathways in the plasma of people with sarcopenia based on metabolomics.In addition,we plan to divide sarcopenic people into several subtypes using metabolomic data by consensus cluster analysis and compare the prognosis of different subtypes.Materials and Methods:Part Ⅰ: The present study was conducted to investigate the prevalence of sarcopenia among Han community-dwelling older adults in Sichuan based on West China Health and Aging Trend study.The logistics regression analysis was used to analyze the associated factors of sarcopenia.Part Ⅱ: We performed the plasma metabolomic characterization of sarcopenia using paired older adults with sarcopenia and without sarcopenia.Linear regression model was used to identify metabolites associated with skeletal mass.Metabo Analyst was used to explore the important metabolic pathways of metabolites.Meanwhile,we tried to establish diagnosis model of SMI using lasso regression.Part Ⅲ: Consensus cluster analysis was used to classify subtype of sarcopenia.Then,extensive bioinformatic analysis such as enrichment analysis and prognosis analysis between different subtypes were carried out.Part Ⅳ: In this part,we validated the results of metabolomics through animal experiments in order to observe whether supplementation of sarcosine can promote the regeneration and repair of gastrocnemius muscle in middle-aged and old mice after CTX injury.Results:Part Ⅰ:1.The prevalence of sarcopenia among Han community-dwelling middle-aged and older adults is 22.3% in Sichuan.2.Age,sex,hypertension,COPD,malnutrition and blood biomarkers such as TBIL,ALT,HDL,FT4,fasting insulin and Vitamin D were associated with sarcopenia.Part Ⅱ:1.Linear regression results showed that ketoleucine was positively associated with SMI in both men and women.In addition,some metabolites,such as prasterone sulfate,pantothenic acid,ascorbic acid,EPA and α-ketoglutaric acid,were also positively associated with SMI,which was consistent with previous studies.2.These metabolites significantly associated with SMI were mainly lipids,fatty acids and amino acids.Alanine,aspartate and glutamate metabolism and Citrate cycle(TCA cycle)metabolism pathways participated in the pathological process of sarcopenia.3.We established a predicted model of SMI using lasso regression.The diagnosis efficiency was higher in male than female(R:0.741 vs 0.591).We calculated the difference between the SMI values based on metabolomics(m SMI)and actual SMI values and divided participants into “m SMI <SMI,residual <-0.5”,“m SMI =SMI,-0.5<residual < 0.5”and “m SMI >SMI,residual > 0.5” group.The rates of SMI and grip strength decreased in 2019 were higher in “m SMI <SMI” group than the other two groups.Part Ⅲ:1.People with sarcopenia are divided into two subtypes based on consensus cluster analysis and lower SMI was observed in type I.2.According to the results of Mann-Whitney U test,we found that amino acids,sugars,fatty acids and lipids were mostly decreased in type I compared to nonsarcopenic group.These differential metabolites plays an important role in metabolic pathways such as Alanine,aspartate and glutamate metabolism,Patothenate and Co A biosynthesis,Citrate cycle(TCA cycle)and Pyruvate metabolism.3.Finally,the rates of SMI decreased in 2019 decreased were higher in type I.Part Ⅳ:1.Through linear regression and the Mann-Whitney U test,we found that sarcosine was significantly decreased in sarcopenia and positively associated with SMI.2.The results of Western Blot showed that compared with CTX+ Na Cl group,the expression levels of PAX7,MYOD and MYOG in CTX+ Sarcosine group increased,especially PAX7.The results of HE stains showed that compared with the CTX+ Na Cl group,muscle regeneration was obvious in the CTX+ Sarcosine group.Conclusion:1.The prevalence of sarcopenia among Han community-dwelling middle-aged and older adults is relatively high in Sichuan.Age,sex,hypertension,COPD,malnutrition and blood biomarkers such as TBIL,ALT,HDL,FT4,fasting insulin and Vitamin D were associated with sarcopenia.2.The metabolites significantly associated with SMI were mainly lipids,fatty acids and amino acids,which were positively associated with SMI in both men and women.Alanine,aspartate and glutamate metabolism and Citrate cycle(TCA cycle)metabolism pathways participated in the pathological process of sarcopenia.3.Lower SMI and poorer prognosis were shown in the subtype of sarcopenia with significantly decreased level of amino acids,carbohydrates,fatty acids,and lipids.4.Sarcosine,which was significantly decreased in sarcopenia and positively associated with SMI,accelerated muscle repair and regeneration in middle-aged and old mice after CTX injury.