Effect Of Leucine On Intestinal Function And Energy Metabolism In Intrauterine Growth Retardation Early Weaner Piglets

Intrauterine growth retardation(IUGR)widely exists in human neonates and multiparous mammals.It is a serious complication of pregnancy and can cause high morbidity and mortality rates,and even has a lasting adverse effects on the growth and development and health of humans and manmmals.Leucine,as an essential amino acids(EAA)for animal growth and development,is the most abundant branched-chain amino acids(BCAA)in many dietary protein,involved in multiple metabolic processes in the body,and it has a vital role in promoting the animal growth and strengthening the immunity,as well as improving the digestion and absorption of nutrients.Thus,this experiment was designed to investigate the regulatory role of leucine on intestinal function and energy metabolism in IUGR piglets during early weaning period,for providing a theoretical basis and reference to the rearing of IUGR piglets and clinical application of infant nutrition.1.Effects of leucine on intestinal histology and immune function in intrauterine growth retarded piglets during early weaning periodSixteen normal birth weight(NBW)and sixteen IUGR piglets were selected in accordance with birth weight from sixteen pregnant sows with the similar parity and bodily condition and parturition date.When one NBW piglet was chosen from a sow,the other IUGR piglet was also selected from the same sow.Both NBW and IUGR piglets were weaned on 14th day and fed a control diet without L-leucine supplementation or a control diet plus 0.35%L-Ieucine supplementation from 14 to 35 days of age,respectively.Thus,all piglets were randomly distributed into 4 groups:NC(NBW+control diet),NL(NBW + leucine diet),IC(IUGR + control diet)and IL(IUGR + leucine diet)with 8 piglets(4 males and 4 females)each.At 35 days of age,all piglets were killed by intramuscular injection of sodium pentobarbital(50 mg/kg of body weight)at 12 h after the last meal.The intestinal histology and intra-epithelial immune cell numbers,contents of TNF-a,IL-2 and IL-10 and mRNA expressions of TNF-a,IL-2 and IL-10 in the ileal mucosa were measured.The results showed that:(1)Compared with NBW piglets,the VH,VCR,VW and VS in the duodenum,jejunum and ileum were obviously decreased(P<0.05),while the CD in the duodenum,jejunum and ileum were markedly increased(P<0.05)in IUGR piglets.Dietary 0.35%L-leucine addition significantly increased(P<0.05)the VH and VCR in the duodenum,the VCR in the jejunum,and the VH,VCR and VW in the ileum,and had a trend to decrease(P=0.081)the CD in the ileum of IUGR piglets.(2)In comparison with NBW piglets,the numbers of GC and IEL in the jejunum and ileum were significantly decreased(P<0.05)in IUGR piglets.Dietary 0.35%L-leucine supplementation markedly increased(P<0.05)the numbers of GC and IEL in the ileum and the number of IEL in the duodenum,and had a trend to increase(P=0.097)the number of IEL in the jejunum of IUGR piglets.(3)In comparison with NBW piglets,IUGR piglets had obviously higher(P<0.05)TNF-a content and significantly lower(P<0.05)IL-10 content in the ileal mucosa.By 0.35%L-leucine addition,TNF-a content displayed a tendency toward to decrease(P=0.051),while IL-10 content was significantly increased(P<0.05)in the ileal mucosa of IUGR piglets.(4)Compared with NBW piglets,TNF-a mRNA expression was obviously up-regulated(P<0.05),IL-2 mRNA expression had a trend to down-regualte(P=0.099),and IL-10 mRNA expression was significantly down-regualted(P<0.05)in the ileal mucosa of IUGR piglets.A tendency for down-regualted(P=0.073)TNF-a mRNA expression,and significantly up-regulated(P<0.05)IL-2 and IL-10 mRNA expressions in the ileal mucosa of IUGR piglets fed a leucine diet.In conclusion,dietary supplementation with 0.35%L-leucine in IUGR piglets during early weaning period could enhance intestinal immune function and repair intestinal damage as indicated by improved intestinal histology,increased intra-epithelial immune cell numbers and alleviated intestinal inflammatory response.2.Effects of leucine on intestinal redox state and mtDNA biogenesis,and mitochondrial function in intrauterine growth retardation piglets during early weaning periodThe experiment was designed same with the experiment 1.The contents of DNA,RNA,and Protein,activities of antioxidative enzyme,contents of MDA,ATP,and mtDNA,and mRNA expression of genes involved in mtDNA biogenesis and mitochondrial function in the jejunal mucosa were investigated.The results showed that:(1)In comparison with NBW piglets,IUGR piglets obviously reduced(P<0.05)the DNA content in the jejunal mucosa.There was a trend towards increased the DNA content(P=0.064)and RNA/DNA(P=0.089)ratio in the jejunal mucosa of IUGR piglets supplemented with leucine diet.(2)Compared with NBW piglets,Mn-SOD and T-AOC activities and ATP content were significantly reduced(P<0.05),and CAT(P=0.074)and GPx(P=0.087)activities exhibited a trend to reduce,while MDA content had a trend to enhance(P=0.063)in the jejunal mucosa of IUGR piglets.With 0.35%L-leucine supplementation,Mn-SOD and T-AOC activities were markedly enhanced(P<0.05),but MDA content was obviously reduced(P<0.05),and ATP content had a tendency toward to enhance(P=0.097)in the jejunal mucosa of IUGR piglets.(3)The mtDNA content in the jejunal mucosa was significantly lower(P<0.05)by IUGR piglets compared with their normal counterparts,however,treatment with leucine partially recovered(P=0.063)the mtDNA content in the jejunal mucosa of IUGR piglets.(4)Compared with NBW piglets,a significantly down-regulation(P<0.05)in NRF1,TFAM,ATPs,CcOX V,Cytc,and Glucokinase mRNA expressions,and a trend towards down-regulated(P=0.074)PGC1α mRNA expression were noted in the jejunal mucosa of IUGR piglets.Treatment with leucine alleviated the down-regulation(P<0.05)in PGC1α,TFAM,ATPs,CcOX I mRNA expressions,and had a tendency toward to up-regulate(P=0.068)CcOX V mRNA expression in the jejunal mucosa of IUGR piglets.In conclusion,dietary supplementation with 0.35%L-leucine could have protective effects on intestinal oxidative stress and mitochondrial dysfunction by improving mtDNA content and mRNA expression of genes involved in mtDNA biogenesis and mitochondrial function,reinforcing the antioxidant capacity,and promoting the growth and development in the intestinal mucosa of IUGR piglets during early weaning period.3.Effects of leucine on intestinal digestive and absorptive functions and energy metabolism in intrauterine growth retardation piglets during early weaning periodThe experiment was designed same with the experiment 1.The activities of digestive and absorptive marked enzymes in the jejunal mucosa and endogenous digestive enzymes in the intestinal contents,contents of Ins and IGF-1 and activities of glucose metabolic enzymes and mRNA expression of genes involved in glucose transport and energy metabolism in the jejunal mucosa were analyzed.The results showed that:(1)Compared with NBW piglets,the sucrase activity had a trend to decrease(P=0.084),the activities of maltase,lactase,AKP,and Na+/K+-ATPase were significantly decreased(P<0.05)in the jejunal mucosa of IUGR piglets.After 0.35%L-leucine supplementation,the maltase(P=0.082)and Na+/K+-ATPase(P=0.062)activities displayed a tendency toward to increase,and AKP activity was significantly increased(P<0.05)in the jejunal mucosa of IUGR piglets.(2)In comparison with NBW piglets,IUGR piglets obviously decreased(P<0.05)the amylase activity in the jejunal and ileal contents and the lipase activity in the ileal contents,and had a trend to decrease(P=0.071)the amylase activity in the duodenal contents.Dietary 0.35%L-leucine supplementation markedly enhanced(P<0.05)the activities of amylase and lipase in the duodenal,jejunal and ileal contents and the chymotrypsin activity in the duodenal contents,and had a tendency toward to increase(P=0.090)the chymotrypsin activity in the jejunal contents of IUGR piglets.(3)The contents of Ins and IGF-1 were significantly reduced(P<0.05)in the jejunal mucosa of IUGR piglets compared with their normal counterparts,while dietary supplementation with 0.35%L-leucine obviously enhanced(P<0.05)the contents of Ins and IGF-1 in the jejunal mucosa of IUGR piglets.(4)In comparison with NBW piglets,the activities of PK in the jejunal mucosa and MDH in the jejunal mitochondria were markedly decreased(P<0.05)in IUGR piglets.After 0.35%L-leucine supplemention,the activities of MDH and SDH in the jejunal mitochondria were markedly increased(P<0.05)in IUGR piglets.(5)Compared with NBW piglets,SGLT1 and mTOR mRNA expressions were significantly down-regulated(P<0.05)and PK mRNA expressions had a trend to down-regulate(P=0.071)in the jejunal mucosa of IUGR piglets.Dietary supplementation with 0.35%L-leucine obviously up-regulated(P<0.05)SGLT1,GLUT2,and mTOR mRNA expressions in the jejunal mucosa of IUGR piglets.In conclusion,dietary supplementation with 0.35%L-leucine could effectively improve the abnormal intestinal digestive and absorptive function and energy metabolism in IUGR piglets during early weaning period through increasing the activities of digestive and absorptive marked enzymes,endogenous digestive enzymes,and glucose metabolic enzymes,as well as the secretion of Ins and IGF-1 and their related genes mRNA expression in the intestine.In summary,it was found that the impaired intestinal immune function,increased oxidative stress,disordered mitochondrial function,poor digestive and absorptive ability,and abnormal energy metabolism in IUGR early weaning piglets,which might be associated with the change of gene transcription level.Dietary supplementation with 0.35%L-leucine could partly promote intestinal growth and development,repair intestinal function and alleviate abnormal metabolism.