| Mandarin fish(Siniperca chuatsi)is a famous freshwater product in China,which is very popular in the market.This study investigated the changes of antioxidant enzyme activity,digestive enzyme activity,blood biochemical indexes and related gene expression in Mandarin fish under starvation and re-feeding conditions.270 mandarin fish with an average body mass of 46.41g were randomly divided into 3 categories and 9 parallel groups.Under the condition of(24±1)℃ the mandarin fish were starved for different times(0d,7d,14d,21d,28d)and were fed for 7 days after 21 days of starvation.The liver,brain,muscle and serum samples of the control group and the treatment group were taken at the above time points,and the related indexes were determined respectively.The main results are as follows:1 Effects of starvation and re-feeding on activities of antioxidant enzymes in liver and expression of genes to growth relationWith the prolongation of starvation time,the content of GSH and the level of TAOC in the liver of mandarin fish increased,which were significantly higher than those of the control group on the 14th,21st and 28th day of starvation(P<0.05,the same below):The activity of SOD decreased on the 7th day of the experiment,and then gradually increased,which significantly higher than that of the control group on the 28th day:the activity of CAT showed a decreasing trend,which was significantly lower than that of the control group on the 28th day of starvation.After 21 days of starvation stress and 7 days of refeeding,GSH content,T-AOC level,SOD and CAT activity were decreased,and there was no significant difference compared with the control group(P>0.05,the same below).The results showed that:starvation stress could make mandarin fish in the state of oxidative stress,and long-term starvation stress had a significant effect on the liver antioxidant system.The results of re-feeding showed that fasting for 21 days did not cause irreversible damage to liver antioxidant system.In this experiment,with the prolongation of starvation time,the expression of MyoD gene and MRF4 gene in the muscle of mandarin fish increased,which were significantly higher than those in the control group on the 7th day of starvation:the expression of IGF-I gene in the liver increased with the prolongation of starvation time,After 14 days of starvation,IGF-I gene was almost not expressed:after 7 days of re-feeding,MyoD gene had no significant difference with the control group,MRF4 gene expression was further upregulated,IGF-I gene expression was up-regulated,but still significantly lower than the control group.2 Effects of starvation and re-feeding on digestive enzyme activities and blood biochemical indexes of mandarin fishIn the starvation stress experiment,the trypsin activity in liver,intestine and stomach of mandarin fish continued to decrease with starvation time,the decreasing trend of trypsin activity in liver and stomach was retarded in 0-14 days,the decreasing speed was accelerated after 14-28 days of starvation,and the trypsin activity in intestine showed a transient recovery state in 21 days of starvation:the LPS activity in intestine decreased with the prolongation of starvation time The activity of α-AMS in liver,intestines and stomach of mandarin fish decreased with the duration of starvation.The activity of α-AMS in intestines and stomach of mandarin fish was significantly lower than that of the control group only after 28th day of starvation.The activity of α-AMS in liver was significantly lower than that of the control group at the 21th day of starvation:After feeding,the activities of α-AMS,LPS and trypsin in liver were restored,and there no significant difference compared with the control group:the activities of three enzymes in intestine were significantly lower than the control group:the activities of typsin in stomach were restored to the level of the control group,and the activities of α-AMS and LPS were significantly lower than the control group.The results showed that in the 28 days starvation stress experiment,mandarin fish used protein and fat to maintain its life activities.In the early stage of starvation(0-14 days),it tended to use protein to maintain its life activities,and in the late stage of starvation(14-28 days),it began to use lipid to provide energy.Refeeding experiment showed that 21 days of starvation stress did not damage the function of liver organs and physiological functions of mandarin fish,but did damage the digestive ability and function of stomach and intestine.The results showed that GLU in the serum of mandarin fish decreased significantly from 0d to 14d after starvation,and then rose slightly and maintained at a relatively stable level:the content of TP in the serum increased first and then decreased,reached the highest value on the 14th day after starvation,and decreased significantly to the lowest value on the 28th day after starvation;the content of TG and T-CHO in the serum showed a downward trend,which were significantly lower than 0 d value on 7 d and 21 d,respectively.Starvation affected the rate of protein and lipid anabolism of mandarin fish,which increased at first and then decreased,and decreased the rate of lipid anabolism.3 Effects of starvation and re-feeding on the expression of TH,DPSS,PITX2,GnRH2 and PMCH genes in brainIn this experiment,GnRH2 mRNA quantity of mandarin fish decreased significantly after 7 days of starvation,and maintained at a relatively stable low level from 7th day to 28th day.There was no significant difference in GnRH2 expression between the two groups after resuming feeding.PMCH gene expression decreased after 7 days of fasting,and decreased significantly on the 21th day of starvation.After re-feeding,PMCH gene expression increased signifircantly and was higher than that of the control group;The relative expression of DPSS in the starvation group was higher than that in the control group,and was significantly higher than that in the control group on the 14th and 28th day of starvation,and there was no significant difference between the two groups after refeeding;starvation stress had little effect on PITX2 and there was no significant difference between the treatment group and the control group at each time point;the mRNA quantity of TH in the starvation group was significantly higher than that in the control group during the whole experiment,and the expression of TH in the re-feeding group was lower than that in the control group,But it was still significantly higher than that of the control group. |
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