| As the most abundant mono-mucleotide in sow’s milk,the content of UMP is the most abundant mononucleic acid in the milk,and its content is several times as the other mono-mucleotide even in the late stage of lactation.Therefore,the present study was to investigated the effects of UMP and UR,a well-known gastro-intestinal metabolic of UMP in vivo,on the intestinal development and function of the piglets.Twenty-one Duroc × Landrace × Yorkshire piglets(12 ± 1 days old,3.32 ± 0.05 kg)were randomly allotted into 3 groups(n = 7)and received milk replacer ad libitum.The piglets were orally administered with physiological saline(control group),476 mg UMP(UMP group)or 348 mg UR(UR group)in 10 mL physiological saline per day for 10 days,respectively.During the experiment,the data of feed intake,mental status,diarrhea condition of piglets were observed,and the temperature and humidity of piglets house were observed.After fasting for 12 h at the end of the test,the blood samples were collected after slaughter,and the intestinal samples were collected for histomorphology and molecular biological analysis.Total RNA was extracted from the intestinal mucosa,and the level of related expression of tight junction proteins and pyrimidine nucleotide metabolic enzymes were detected by qRT-PCR.The apoptosis levels of intestinal epithelial cells were detected by TUNEL and in vitro experiments.The results revealed that:(1)The effects of UMP/UR on the growth performance.Oral supplementation of UMP and UR in segregated early-weaned piglets improved the ADG(P < 0.05),and greatly reduced the rate of diarrhea(P < 0.05)and diarrhea index(P < 0.05)as compared to the control.Specifically,the final body weights of the piglets were 3.64 ± 0.21 kg,4.08 ± 0.19 kg,3.91 ± 0.11 kg in control,UMP and UR group,respectively.The ADG of the early-weaned piglets in control group was 34.67 ± 11.16 g.It increased to 73.80 ± 11.67 g in UMP group(P < 0.05)and to 71.17± 6.66 g(P < 0.05)in UR group,respectively.Our results found that the oral administration of UR increased the villus length/crypt depth ratio(V/C)in jejunum(P < 0.05).However,no significant difference was found in these three indexs of piglets among the three groups(P > 0.05).(2)Relative gene expressions of pyrimidine nucleotide metabolic enzymesIn duodenum mucosa,the expression of UMPS,CMPK1,RRM2,UPRT,CTPS1 and CTPS2 increased significantly in UR group(P < 0.05).No significant difference was found in UMP group in pyrimidine nucleotide metabolic enzymes,compared to the control.Compared to the control group,both UMP and UR decreased the expression of CAD and RRM2 at jejunum mucosa(P < 0.05)and CTPS1 at ileum mucosa(P < 0.05).(3)Relative gene expressions of tight junction proteinsCompared to the Control,oral administration of UR increased the relative expression of Claudin-3 and E-cadherin in duodenum mucosa(P < 0.05),while oral administration of UMP had no significant effect on these two genes.There was no significant effect of UR and UMP on ZO-1 and occludin in duodenal mucosa relative to the control.While compared with UMP group,UR increased the expression of ZO-1 and occludin in duodenal mucosa(P < 0.05)significantly.However,there was no effect of UMP and UR on the expression of tight junction protein gene in jejunum and ileum mucosa(P > 0.05).In addition,comparing to the other two groups,UR induced the expression of ZO-1 or Occludin-1 in duodenum mucosa(P < 0.05).(4)Levels of apoptosis of small intestineThe TUNEL results showed that compared with the control group,UR and UMP increased the positive expression and apoptosis of the intestinal epithelial cells of the top of villus at duodenum.However,little effect of apoptosis of UMP and UR on intestinal epithelial cells at jejunum and ileum.Besides,UMP and UR decreased in cell viability of IPEC-J2 cells significantly with values of 10 mM and 50 mM.And UMP(10mM)and UR(50mM)treatment extremely increased late apoptosis ratio(%)in cells relative to the control cells(P < 0.01).Take a conclusion,oral administration of UR and UMP could reduce the risk of diarrhea,improve the small intestinal morphology,up-regulate tight junction protein expression in duodenum,enhence the metabolic process in the intestine of the piglets.Moreover,UMP and UR promote the epithelial cells renewal,benefit for intestinal development and health,which may explain the improvement of growth performance and high V/C ratio in segregated early-weaned piglets. |
