| Maternal nutrition determines early embryonic growth and fetal development.Alterations in fetal health are closely related to the development of chronic diseases in late adulthood.Intrauterine growth retardation(IUGR)has a significant impact on pig production and human health.Protein synthesis is important for animal early growth.In humans and rodents,leucine can regulate hormone secretion,stimulate the synthesis of protein in skeletal muscle and other tissues,but the research about leucine on IUGR piglets growth and nutrition regulation rarely reported.In this paper,IUGR piglets were selected as the research object,and leucine was selected as the experimental material.The aim of this study was to study the regulation of dietary leucine level on the growth and development of IUGR piglets,and to provide reference for the study of nutrition control of different birth weight piglets.This paper is divided into the following four parts:1 Effects of Leucine on Production Performance,Protein Metabolism in IUGR PigletsThe piglets were divided into four groups:8 pigs in each group.There were two levels of leucine in the experiment.The specific groups were as follows:1)NC group:normal weight piglets fed basal diet(1.45%leucine);2)NL group:normal weight piglets dietary supplementation with 0.35%leucine(1.8%leucine);3)IC group:IUGR piglets were fed basal diets(1.45%leucine);4)IL group:IUGR piglets supplemented with 0.35%leucine diets(1.8%leucine).At the age of 35 days,the average daily dietary intake,average daily gain and feed utilization were calculated for each group of piglets.The contents of biochemical indexes,serum free amino acids and serum hormone levels,serum antioxidant levels were evaluated.The results showed that:(1)Dietary leucine could significantly increase the final weight(P<0.05)and average daily gain(P<0.05)of IUGR piglets,but had no significant effect on average daily feed intake(P<0.05).(2)The absolute weight of heart and kidney in IUGR piglets were significantly lower than normal piglets.Dietary supply with leucine increased the absolute and relative weight of liver in IUGR piglets(P<0.05).(3)The level of leucine and valcine in serum of IUGR piglets was significantly lower than normal piglets(P<0.05).Supplemented with leucine increased the level of leucine,methionine and phenylalanine in IUGR piglets(P<0.05),but the level of isoleucine and lysine was significantly lower(P<0.05).(4)Dietary supply with leucine increased the content of total protein in serum of IUGR piglets significantly on the 21st day after the start of the experiment(P<0.05),and the content of urea nitrogen was significantly decreased at the 7th,14th and 21st day(P<0.05).(5)Compared with normal piglets,IUGR piglets were significantly decreased serum ALP and GPT activity on day 21 after initiation of the trial(P<0.05).At the beginning of the experiment and the 21 th day after the start of the experiment,the serum ALP and GPT activity of IUGR piglets were significantly increased(P<0.05),and the serum GOT activity of IUGR piglets were significantly increased at the 7th day(P<0.05).(6)In the IUGR piglets,dietary supply with leucine increased the level of leptin significantly(P<0.05),and decreased the serum cortisol concentration(P<0.05)significantly.(7)Compared with normal piglets,the activity of lysozyme and C3 in IUGR piglets were significantly decreased(P<0.05).Dietary supply with leucine increased the levels of lysozyme activity,C3 and C4 in serum of IUGR piglets significantly(P<0.05).2 Effects of Leucine on Protein Deposition in IUGR PigletsThe design was the same as the test 1.The unit and total RNA and DNA content of normal and IUGR piglets were measured and RNA/DNA was calculated.The results showed that:(1)Dietary supply with leucine decreased the content of RNA in spleen tissue(P<0.05),while the content of RNA in skeletal muscle tissue was significantly increased(P<0.05).(2)Compared with normal piglets,the DNA content in liver and spleen of IUGR piglets was significantly decreased(P<0.05).(3)Compared with normal piglets,the total RNA content in heart,liver,kidney and pancreas of IUGR piglets was significantly decreased(P<0.05).Supplemented with leucine increased had no effect on the total RNA content in organ between IUGR and normal piglets(P>0.05).(4)The content of total DNA in heart,liver,kidney and pancreas of IUGR piglets was significantly lower than that in normal piglets.Supplemented with leucine had no effect on the total DNA content in organ between IUGR and normal piglets(P>0.05).(5)Compared with normal piglets,the RNA/DNA was significantly decreased in the liver and skeletal muscle of IUGR piglets.Dietary supply with leucine decreased the RNA/DNA in heart and spleen of IUGR piglets(P<0.05),and the RNA/DNA in liver and skeletal muscle were significantly increased(P<0.05).3 Effect of leucine on the regulation of protein metabolism in pigletsThe design was the same as the test 1.The mRNA expression on protein synthesis,degradation in liver and skeletal muscle tissue were measured.And the expression of mTOR,S6K1 protein and its phosphorylation in liver and skeletal muscle were evaluated.The results showed that:(1)Compared with normal piglets,the expression of mTOR mRNA in skeletal muscle of IUGR piglets was significantly decreased(P<0.05).The expression of S6K1 and 4EBP-1 mRNA in skeletal muscle of IUGR piglets was significantly up-regulated(P<0.05).(2)Compared with normal piglets,the expression of S6K1 gene in liver of IUGR piglets was significantly decreased(P<0.05).Dietary supply with leucine increased the expression of S6K1,4EBP-1 and mTOR gene in liver of IUGR piglets(P<0.05).(3)Compared with normal piglets,the expression of MuRF-1 and MAFbx mRNA in skeletal muscle of IUGR piglets was significantly up-regulated(P<0.05).The expression of MAFbx and FOXO-1 mRNA in liver of IUGR piglets was significantly down-regulated(P<0.05).(4)The expression of MAFbx gene in the liver of IUGR piglets was significantly lower than that in normal piglets(P<0.05),but the expression of FOXO-3 gene in the liver of IUGR piglets was significantly higher than that in normal piglets(P<0.05).Supplemented with leucine up-regulated the expression of MAFbx gene in the liver of IUGR piglets(P<0.05).(5)Compared with normal piglets,the phosphorylated level of S6K1 in IUGR piglets were significantly lower(P<0.05).Supplemented with leucine increased the phosphorylation state of mTOR and S6K1 in skeletal muscle of IUGR piglets(P<0.05).And the phosphorylated level of mTOR in NL group were significantly higher than those in other groups(P<0.05).4 Effects of Leucine on Insulin Signal Pathway Genes in IUGR PigletsThe design was the same as the test 1.The average daily protein,fat and energy intake of NBW and IUGR piglets were calculated.The levels of serum glucose and insulin,lipid metabolism were measured.The related genes expression of insulin signal pathway and glucose metabolism in liver were analyzed.The results showed that:(1)The total weight gain of IUGR piglets was lower than normal piglets significantly(P<0.05).In the first week,the weight gain of NC group was significantly higher than that of other groups(P<0.05).During the second week,the weight gain of IUGR group was significantly lower than that of normal piglets(P<0.05).In the third week,the weight gain of IC group was lowest(P<0.05).During the experiment,the protein intake of NC group was significantly higher than that of other groups(P<0.05).The protein intake of IC group was the lowest in all experimental groups(P<0.05).(2)Compared with normal piglets,the levels of glucose and insulin in IUGR piglets were significantly decreased at 0d,7d,14d and 21d after the start of the experiment(P<0.05).Dietary supply with leucine increased the levels of glucose and insulin in IUGR piglets significantly at 7d,14d and 21 d after the start of the experiment(P<0.05).(3)Compared with normal piglets,serum cholesterol levels at 7d and serum creatinine at 21d in IUGR piglets were significantly decreased(P<0.05),but the serum triglyceride level was significantly increased at 7 days(P<0.05).Dietary supply with leucine can be significantly increased serum triglycerides level in Od and serum creatinine level in 21d of IUGR piglets(P<0.05).(4)Compared with normal piglets,the expression of IRS-1,IRS-2,PIK3CG and PRKAG in liver of IUGR piglets was significantly higher than that in normal piglets(P<0.05),but the expression of PRKCZ in liver was significantly decreased(P<0.05).Dietary supply with leucine can be significantly increased IRS-2,PIK3CG and PRKAG expression in liver of IUGR piglets(P<0.05).(5)The expression of GYS-1,GLUT-2 and GLUT-4 in liver of IUGR piglets was significantly lower than that of normal piglets(P<0.05).Dietary supplementation of leucine increased the expression of GCK,GYS-1,G6PD and GLUT-2 in the liver of IUGR piglets(P<0.05).The expression of GSK-3A was was significantly down-regulated in the liver of IUGR piglets(P<0.05).It can be concluded as follows:(1)Leucine can improve the weight gain,improve the amino acid metabolism of,promote the protein utilization of IUGR piglets,stimulate the secretion of hormones and ameliorate immune function of IUGR piglets.(2)Leucine can increase the concentration of RNA in the tissue of skeletal muscle,the total RNA concentration in liver and the RNA/DNA in liver and skeletal muscle tissue,and promote tissue protein synthesis of IUGR piglets.(3)Supplemented with leucine stimulated the phosphorylation of mTOR and S6K1 in skeletal muscle of IUGR piglets,reduced the degradation of skeletal muscle protein and regulated the protein metabolism of IUGR piglets through mTOR signaling pathway.(4)Leucine improve the liver lipid metabolism and glucose metabolism in IUGR piglets.Leucine supplementation also stimulates insulin signaling and improves metabolism in IUGR piglets. |
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