Effects Of Succinate On Muscle Growth And Pork Quality

The growth of skeletal muscle,hypertrophy of muscle fiber,and deposition of protein are closely related to the meat production performance of livestock and poultry.A large number of studies have shown that breeds,endocrine hormones,nutritional levels and exercise training can affect skeletal muscle protein turnover.There are many signaling pathways involved in skeletal muscle hypertrophy,including insulin signaling pathway,ubiquitin proteasome pathway and autophagy lysosome pathway.Succinate?SUA?,also known as succinic acid,is an important intermediate in tricarboxylic acid cycle?TCA?,which is widely found in plants and many animal tissues.Exercise can significantly increase the level of succinate.In recent years,there are many reports have been shown that succinate can act as a bioactive signal molecule,and play an important regulatory role in cell metabolism,substrate level phosphorylation,ketone body utilization,and haemoglobin metabolism.However,it is still unclear whether the succinate produced by exercise has an important regulatory effect on skeletal muscle hypertrophy and protein synthesis.In order to comprehensive investigate the effect of succinate on muscle growth and pork quality,this experiment was firstly analyzed the protein synthesis in C2C12 cells and the expression level of protein in the related pathway was analyzed by using the total protein content,myotubes diameter,western blot assay,immunocytochemistry,assay of Ca²⁺and co?immunoprecipitation.In vivo,30 8?week?old C57BL6/J male mice were randomly divided into three groups?n=10?.Different concentrations of succinate?0,150 and 300 mg/kg?were injected in intraperitoneal.Then,analyze the pathways associated with protein synthesis and the protein deposition in gastrocnemius muscle by western blot assay and immunohistochemistry.Moreover,a total of 72 healthy fattening pigs,which their average weight is around 55kg,were randomly divided into two groups?control group:basal diet fed to fattening pigs,treatment group:feeding the basal diet fed with 1%succinate additive?.Each group had 3 replicates with 12 fattening pigs per replicate.Pre-feeding was conducted for 2 days,then 42 test days.During the test period,the fattening pigs were fed four times a day,and they were allowed to feed freely and freely drink water daily.Observe their health status and record the amount of each feed intake.After the end of the trial,weighing,and then slaughtered to receive blood sample and the longissimus dorsi muscle to determine the relevant muscle quality indicators.Our in vitro study showed that succinate could dose-dependently increase protein synthesis in C2C12 myotube,and enhance the phosphorylation level of mTOR,S6,eIF4E,4E-BP1 and FoxO3a.Furthermore,we found that 20mM succinate dramatically increased Ca²⁺.Under the effect of succinate,the phospho-ERK level and the crosstalk between ERK and Akt were elevated.Meanwhile,either ERK antagonist or mTOR inhibitor could notably abolish the effect of succinate on protein synthesis.Our in vivo study also confirmed that succinate could dose-dependently increase the protein synthesis,and the phosphorylation level of ERK and FoxO3a in gastrocnemius muscle.The vivo study on fattening pigs also show that 1%succinate could dramatically reduce cooking loss,and slightly reduce the L^*_45min of pork,it has some certain influence on improving pork quality.In summary,these findings demonstrated that succinate might promoted skeletal muscle protein deposition,and further promote the growth of muscle;to some extent,improve pork quality.The results of this study are helpful for the in-depth understanding of the effects of succinate on muscle growth and pork quality,provide new ideas for further improving meat quality as well.