The Effects Of Feeding Systems On Meat Quality And Differentiation Of Skeletal Muscle Satellite Cells Of Sunit Sheep

The objective of this study was to investigate the effects of feeding system on carcass traits?meat quality?muscle fiber types and the differerntiation of skeletal muscle satellite cells(SMSCs).The regulation of SMSCs'regeneration and multiptential differentiation affected by feeding system were analyzed.The molecular mechanism of myogenesis and adipogenesis of SMSCs to alter the muscle mess were studied.To investigate the effects of feeding system on skeletal muscle mess and intramuscular fat content,the mouse SMSCs were separated and cultured in vitro,and the induction of high glucose and AICAR,and the co-work of high glucose and AICAR on SMSCs'regeneration and differentiation were analyzed.In general,the present study was to analyse the variation of feeding system affect sheep meat quality via alting differentiation of muscle stem cells,and thus improve the captivity sheep meat quality.24 Sunit sheep of 12 months old were raised in pasture and captivity,respectively.To analyze the effects of feeding systems on meat quality via regulating the regeneration and differentiantion of skeletal muscle satellite cells(SMSCs),meat quality and carcass yield of Sunit sheep were investigated,and the genes and protein expression related to the muscle messwere detected by RT-PCR and western blotting.The results showed that:The live weight?body length?body height and chest depth were significant higher in pasture than in captivity(P<0.05).The carcass weight?carcass length?carcass height?meat-bone ratio and lean weight were significant higher in pasture than in captivity(P<0.05).The dressing percentage?lean yield and meat production ratio were significant higher in captivity than in pasture(P<0.05).The pH1 and pH24 value of longissimus dorsi muscle(LD muscle)were significant higher in captivity than in pasture(P<0.05).The redness a*was higher in captivity than in pasture(P<0.05),the yellowness b*was lower captivity than in pasture(P<0.05),which resulted in no significant difference between two groups(P>0.05).There were no significantly change in cooking loss?shear force or intramuscular fat content in two groups(P>0.05).The Myosin heavy chain genes expression were detected by RT-PCR to analyzed the effects of feeding systems on myofiber type transformation.The results showed that there were no differences of MyHCI and MyHCIIx gene expression in two groups(P>0.05).The MyHCIIa gene expression was significant higher in captivity than in pasture(P<0.05).The MyHCIIb gene expression was significant lower in captivity than in pasture(P<0.05),indicating that there was a shift in muscle from glycolytic to oxidative fiber type in captivity Sunit sheep.The expression of specific proteins of SMSCs?myoblasts?adipoblasts and brown adipocytes were measured by western blotting,the results showed that Pax7 expression was significant lower in captivity than in pasture(P<0.05).MyoD expression was significant lower in captivity than in pasture(P<0.05)as well.There was no significant difference of PPARg in two groups(P>0.05).UCP-1 expression was significant higher in captivity than in pasture(P<0.05),indicated that the variation of feeding system can affect the activation and differentiation of SMSCs.The correlation of meat quality and genes and proteins expression showed that pH1?pH24 value were negative related to b*value(P<0.05);Pax7 expression was negative related to pH1?pH24 value(P<0.05),and positive correlated with b*value(P<0.05);MyHCI expression was positive correlated with L value(P<0.05);MyHCIIa expression was negative related to b*value(P<0.05);MyHCIIb expression was negative related to pH1?pH24 value(P<0.05),and negative related to a*value(P<0.05),and positive correlated with b*value(P<0.05).It came out the results that the less yellowness of meat color and higher pH value of captivity Sunit sheep were induced by inactivation and myogenesis of SMSCs which was resulted from lack of physical exercise.In order to investigate the effects of feeding systems on SMSCs regeneration and differerntiation,the mouse skeletal muscle satellite cells were separated and cultured.The effects of high glucose?AICAR and synergistic effects of two on SMSCs regeneration and differerntiation were studied.The results showed that:15mM glucose induced SMSCs differentiated into Myf5+ cells;25mM glucose induced SMSCs differentiated into brown adipocytes;25mM glucose induced SMSCs differentiated into adipoblasts.Which indicated that high concentration of blood glucose can induce myogenic stem cells tranformation into adipocytes or brown adipocytes.300?M AICAR activated SMSCs and myogenesis.It demonstrated that the activation of AMPK can regulate SMSCs regeneration and myogenesis.The co-work of 25mM glucose and AICAR affected SMSCs withdraw from the multipotency pathway and maintained the regeneration pathway.The co-work of 35mM glucose and AICAR can induce the multipotential differentiation of SMSCs immediately,though it didn't last long enough to the final period.