N-氨甲酰谷氨酸(NCG)通过催化线粒体内氨甲酰磷酸合成酶-Ⅰ与二氢吡咯-5-羧酸合成酶使鸟氨酸转化为瓜氨酸,瓜氨酸在酶的催化作用下转化为内源性精氨酸[1-2]。在动物繁殖过程中,精氨酸及其代谢产物多胺和一氧化氮(NO)在胎盘形成、胚胎生长和胎儿发育中起着关键作用[3-4]。但由于精氨酸成本较高、在瘤胃降解中高需要包被、与碱性氨基酸产生拮抗作用,故未在反刍动物中得到广泛应用。NCG具有半衰期长、降解率低、降低瘤胃甲烷排放、添加量与价格双低、且不会与色氨酸、组氨酸和赖氨酸有拮抗作用等优点,可有效调控机体内精氨酸代谢并改善繁殖性能[5-9]。
1 NCG对反刍动物繁殖性能的影响 1.1 NCG对反刍动物子宫氨基酸的影响氨基酸是早期胚胎发育所需要的子宫液成分,可增强胎盘蛋白质合成并促进细胞增殖,调节胚胎发育和着床[10]。在正常妊娠中,大多数氨基酸浓度在母体和胎儿之间存在正相关关系,且妊娠期间,充足的氨基酸供应对胎儿和胎盘的发育非常重要。NCG作为精氨酸前体物质,主要通过调控精氨酸的代谢来对机体发挥作用。精氨酸是孕体(胚胎/胎儿和滋养层/胎盘)生长和发育的必需氨基酸[11]。Wu等[11]通过观察萨福克母羊发现精氨酸的运输与子宫内膜和受孕中阳离子氨基酸转运蛋白密切相关,氨基酸转运蛋白有助于把精氨酸运到子宫腔,从而对受孕产生积极影响。Gao等[12]还发现在妊娠第10~15天,母羊子宫中精氨酸浓度较之前增加10倍。Bairagl等[13]发现精氨酸可激活反刍动物雷帕霉素靶蛋白(mTOR)细胞信号通路,以增强胎盘中蛋白质合成和细胞增殖。吴宝升等[14]在妊娠早期细毛羊饲粮中添加0.3%和0.4%的NCG会显著提升羊水与胎儿血浆尿素循环中氨基酸(精氨酸、瓜氨酸、鸟氨酸和脯氨酸)浓度来保障胎儿早期健康发育。目前NCG对氨基酸的影响的研究大多集中在母体血液,而对子宫氨基酸浓度的变化及机制方面研究寥寥无几且很肤浅,尤其是反刍动物,因此需加深这方面的研究。
1.2 NCG对生殖系统血流量的影响NCG可通过促进内源精氨酸合成提升子宫与胎盘间血流量,从而促进胚胎发育和胎儿的生长。一氧化氮(NO)作为精氨酸代谢产物,是血管生成关键调节因子,可通过抑制环磷酸鸟苷的分解刺激血管平滑肌和毛细血管周细胞产生血管内皮生长因子(VEGF)来调节子宫血流量[13, 15-16],也可促进胎盘血管扩张和加快血液流动来促进胎儿与母体的联系[17]。胎盘血流量之所以对胎儿的存活、生长发育很重要,取决于子宫胎盘血管生成和血管发育。子宫胎盘血管生成、发育受血管生成因子及其受体调节,例如VEGF、胎盘生长因子(PlGF)、血管生成素(ANG)和内皮型一氧化氮酶(eNOS)[13]。VEGF促进血管通透性并参与毛细血管的形成;PLGF有助于胎盘血管生成;而ANG表达量与内皮细胞对血管因子诱导的血管生成的敏感性呈正比;eNOS可调控血管通透性调节血流量[13, 18-19]。蔡元等[20]在妊娠早期母羊饲粮中添加不同水平NCG,发现可通过显著提高一氧化氮合酶活性来提升NO含量,进而提升母体与胎儿间血流量促进胎盘发育。Gootwine等[21]也发现精氨酸可促进绵羊NO生成继而增加血管生成和血管舒张,进而增加子宫血流量。但目前NCG对反刍动物血流量及相关因子方面的研究寥寥无几,故还有很大的研究空间。
1.3 NCG对胎盘发育的影响精基酸可刺激胎盘生长促进营养物质从母体向胚胎或胎儿的转移,以促进胚胎的存活和生长发育。吴宝升等[22]发现饲粮中补充NCG可通过增加内源精氨酸的含量来激活磷脂酰肌醇-3-羟激酶/蛋白激酶/mTOR(PI3K/Akt/mTOR)信号或增加NO的代谢,促进蛋白质表达,进而促进胎盘形成、子宫发育及胎儿的生长。孙玲伟[23]通过对妊娠期营养限饲湖羊饲喂NCG,发现能够显著提高胎盘效率(胎儿体重除以胎盘的质量),影响胎盘相关因子VEGF含量、mTOR通路表达、胚胎脐静脉血中代谢物含量变化,以及提高胎儿体重,这和Zhang等[24]的试验结果一致。但吴宝升等[22]却发现添加NCG并未对妊娠早期细毛羊的胎盘重产生显著影响,这可能是由于NCG添加量较低导致,此外,Zhang等[24]通过对营养受限的母羊饲喂添加NCG和包被后的精氨酸的饲粮,发现妊娠期间母体营养受限时,胎盘类型会从A向D进行转换,影响母羊内分泌状况,增加胎盘血流量,促进母体对营养物质的吸收。鉴于胎盘的重要性,很有必要对NCG添加量及其对胎盘结构及功能进行更深层次的研究。
1.4 NCG对胎儿发育的影响妊娠期营养不足会降低母体、胎儿血浆和体液中多胺、精氨酸家族及相关支链氨基酸的含量,导致宫内发育迟缓(IUGR),从而会降低胎儿存活率,影响胚胎和胎儿发育[25-30]。绵羊妊娠期间母体营养不良会导致胎儿生长轨迹改变,胎儿下丘脑-垂体-肾上腺轴发育改变导致胎儿肾上腺加速成熟、胰腺发育改变,继而胰岛素信号和氨基酸代谢发生改变,引起胎儿早产率增加[31-32]。也有研究表明,母羊妊娠期间营养不良会减少子宫和脐带血流量继而会造成胎盘变小和胎儿体重减轻[33]。在妊娠至分娩第60天期间,每天3次注射精氨酸给营养不足的母羊,可使羔羊的出生体重增加21%,并在不影响母羊体重的情况下有效预防IUGR[30]。妊娠第60~147天,通过给母羊补喂精氨酸或NCG,可改善胎儿内分泌的代谢稳态、增加胎儿肝脏和背最长肌中氨基酸的可利用性以及影响生长轴基因的表达,进而降低胎儿IUGR发生几率[29]。这与Lassala等[34]、Herring等[25]试验结果一致。此外Zhang等[35]对IUGR绵羊补充NCG,发现可增加胎儿体重,有效缓解胎儿胸腺发育和免疫功能对IUGR的反应。且Zhang等[27]对IUGR羔羊进行研究发现,饲粮中添加精氨酸和NCG均能降低IUGR所带来的不良反应,但精氨酸和NCG之间没有显著差异。但反刍动物在营养受限过程中,NCG对胎盘发育和血管生成及相关因子的影响还需要进行深入的研究。
1.5 NCG对种公畜精液品质的影响多胺(腐胺、精胺和亚精胺)是细胞生长和分化的重要生物分子,作为精氨酸代谢物的鸟氨酸可通过被鸟氨酸脱羧酶转化为腐胺,腐胺随后参与精胺和亚精胺的合成[36]。在雄性动物中NCG可通过内源性生成精氨酸促进多胺合成,继而提升雄性动物精液相关指标,提高对雄性动物的利用,增加养殖场的经济效益。Ozer等[37]发现精氨酸可显著提高精浆精氨酸酶活性,促进多胺合成,增加精子浓度和提升精子活力,继而提高公羊繁殖力。汪建国等[38]也表明,NCG的添加可以使新疆褐牛种公牛的采精量、精子活力与浓度均得到不同程度的提升,精子畸形率较对照组均呈下降趋势,且随着NCG添加量的升高,褐牛各方面性能呈依赖型升高。目前来说,NCG作为新型饲料添加剂在单胃动物上研究较多,在反刍动物尤其是反刍动物种公畜方面的研究寥寥无几,且对其适用范围及其最优剂量都有待深入研究。
2 小结自从2014年NCG被列入新型饲料添加剂名单后,国内外对其进行了研究,但大多针对的是单胃动物,NCG对反刍动物繁殖方面的研究还比较少,这方面还有更大的进步空间,由于NCG是以氨基酸为主要有效成分的天然饲料添加剂,降解率低且具有价格和添加量双低的优点,NCG在养殖场的应用很有意义。近几年也有人将NCG与微量元素结合在一起进行研究[39-40],因此NCG对反刍动物的生长、繁殖性能以及代谢机制都有待深入研究。
[1] |
AH MEW N, MCCARTER R, DAIKHIN Y, et al. Augmenting ureagenesis in patients with partial carbamyl phosphate synthetase 1 deficiency with N-carbamyl-L-glutamate[J]. The Journal of Pediatrics, 2014, 165(2): 401-403. DOI:10.1016/j.jpeds.2014.04.012 |
[2] |
CHACHER B, ZHU W, YE J A, et al. Effect of dietary N-carbamoylglutamate on milk production and nitrogen utilization in high-yielding dairy cows[J]. Journal of Dairy Science, 2014, 97(4): 2338-2345. DOI:10.3168/jds.2013-7330 |
[3] |
WU G Y, KNABE D A, KIM S W. Arginine nutrition in neonatal pigs[J]. The Journal of Nutrition, 2004, 134(10): 2783S-2790S. DOI:10.1093/jn/134.10.2783S |
[4] |
BÉRARD J, BEE G. Effects of dietary l-arginine supplementation to gilts during early gestation on foetal survival, growth and myofiber formation[J]. Animal, 2010, 4(10): 1680-1687. DOI:10.1017/S1751731110000881 |
[5] |
CAI S, ZHU J L, ZENG X Z, et al. Maternal N-carbamylglutamate supply during early pregnancy enhanced pregnancy outcomes in sows through modulations of targeted genes and metabolism pathways[J]. Journal of Agricultural and Food Chemistry, 2018, 66(23): 5845-5852. DOI:10.1021/acs.jafc.8b01637 |
[6] |
任利圆. 日粮中添加N-氨甲酰谷氨酸对泌乳牛生产性能、瘤胃发酵及血液生化指标的影响[D]. 保定: 河北农业大学, 2019. REN L Y. Effects of dietary NCG supplementation of on production performance, rumen fermentation and blood biochemical parameters of lactating cows[D]. Master's Thesis. Baoding: Agricultural University of Hebei, 2019. (in Chinese) |
[7] |
CHACHER B. N-甲酰谷氨酸作为精氨酸增强剂的评定及其对高产奶牛瘤胃发酵、泌乳性能和氮利用的影响[D]. 博士学位论文. 杭州: 浙江大学, 2013: 1-114. CHACHER B. Evaluation of N-carbamoylglutamate as argininineenhancer and its effect on rumen fermentation, lactation performance and nitrogen utilization in high yielding lactating dairy cows[D]. Ph. D. Thesis. Hangzhou: Zhejiang University, 2013: 1-114. (in Chinese) |
[8] |
CHACHER B, LIU H Y, WANG D M, et al. Potential role of N-carbamoyl glutamate in biosynthesis of arginine and its significance in production of ruminant animals[J]. Journal of Animal Science and Biotechnology, 2013, 4(1): 16. DOI:10.1186/2049-1891-4-16 |
[9] |
MA Y F, ZHOU S, LIN X, et al. Effect of dietary N-carbamylglutamate on development of ovarian follicles via enhanced angiogenesis in the chicken[J]. Poultry Science, 2020, 99(1): 578-589. DOI:10.3382/ps/pez545 |
[10] |
ZENG X F, HUANG Z M, MAO X B, et al. N-carbamylglutamate enhances pregnancy outcome in rats through activation of the PI3K/PKB/mTOR signaling pathway[J]. PLoS One, 2012, 7(7): e41192. DOI:10.1371/journal.pone.0041192 |
[11] |
WU G, BAZER F W, BURGHARDT R C, et al. Impacts of amino acid nutrition on pregnancy outcome in pigs: mechanisms and implications for swine production[J]. Journal of Animal Science, 2010, 88(Suppl.13): E195-E204. |
[12] |
GAO H J, WU G Y, SPENCER T E, et al. Select nutrients in the ovine uterine lumen.Ⅰ.Amino acids, glucose, and ions in uterine lumenal flushings of cyclic and pregnant ewes[J]. Biology of Reproduction, 2009, 80(1): 86-93. DOI:10.1095/biolreprod.108.071597 |
[13] |
BAIRAGI S, QUINN K E, CRANE A R, et al. Maternal environment and placental vascularization in small ruminants[J]. Theriogenology, 2016, 86(1): 288-305. |
[14] |
吴宝升, 张崇志, 孙海洲, 等. 日粮中添加NCG对妊娠前期鄂尔多斯细毛羊血液、尿囊液和羊水中氨基酸浓度的影响[J]. 家畜生态学报, 2021, 42(1): 37-45. WU B S, ZHANG C Z, SUN H Z, et al. Effects of dietary NCG on amino acid concentrations in blood, allantoic fluid and amniotic fluid of Erdos fine wool sheep in early pregnancy[J]. Acta Zoologica Sinica, 2021, 42(1): 37-45 (in Chinese). DOI:10.3969/j.issn.1673-1182.2021.01.007 |
[15] |
VILLANUEVA-GARCÍA D, MOTA-ROJAS D, HERNÁNDEZ-GONZÁLEZ R, et al. A systematic review of experimental and clinical studies of sildenafil citrate for intrauterine growth restriction and pre-term labour[J]. Journal of Obstetrics and Gynaecology, 2007, 27(3): 255-259. DOI:10.1080/01443610701194978 |
[16] |
AHMED A, PERKINS J. Angiogenesis and intrauterine growth restriction[J]. Best Practice & Research Clinical Obstetrics & Gynaecology, 2000, 14(6): 981-998. |
[17] |
钟锐, 李荫柱, 刘博, 等. 妊娠中后期饲粮添加氮氨甲酰谷氨酸对新生子代滩羊生长发育、脂肪沉积相关基因表达以及母羊血清生化指标的影响[J]. 动物营养学报, 2021, 33(4): 2355-2364. ZHONG R, LI Y Z, LIU B, et al. Effects of dietary N-carbamyl glutamate in middle and late gestation period on growth and development, expression of fat deposition related genes of newborn offspring Tan sheep and serum biochemical parameters of ewes[J]. Chinese Journal of Animal Nutrition, 2021, 33(4): 2355-2364 (in Chinese). DOI:10.3969/j.issn.1006-267x.2021.04.053 |
[18] |
REYNOLDS L P, BOROWICZ P P, VONNAHME K A, et al. Placental angiogenesis in sheep models of compromised pregnancy[J]. The Journal of Physiology, 2005, 565(1): 43-58. DOI:10.1113/jphysiol.2004.081745 |
[19] |
REYNOLDS L P, BOROWICZ P P, VONNAHME K A, et al. Animal models of placental angiogenesis[J]. Placenta, 2005, 26(10): 689-708. DOI:10.1016/j.placenta.2004.11.010 |
[20] |
蔡元, 田见晖, 王栋, 等. 妊娠早期饲粮添加不同水平N-氨甲酰谷氨酸改善母羊产羔性能的研究[J]. 畜牧兽医学报, 2021, 52(1): 126-134. CAI Y, TIAN J H, WANG D, et al. Effects of dietary N-carbamylglutamate supplementation on improving lambing performance of ewes during early pregnancy[J]. Acta Veterinaria et Zootechnica Sinica, 2021, 52(1): 126-134 (in Chinese). |
[21] |
GOOTWINE E, ROSOV A, ALON T, et al. Effect of supplementation of unprotected or protected arginine to prolific ewes on maternal amino acids profile, lamb survival at birth, and pre- and post-weaning lamb growth[J]. Journal of Animal Science, 2020, 98(11): skaa284. DOI:10.1093/jas/skaa284 |
[22] |
吴宝升, 张崇志, 桑丹, 等. 日粮中添加NCG对妊娠前期鄂尔多斯细毛羊子宫内膜层及胎儿发育的影响[J]. 家畜生态学报, 2020, 41(7): 52-58. WU B S, ZHANG C Z, SANG D, et al. Effects of different NCG levels of diet on maternal endometrium and fetal development during pre-pregnancy of Ordos fine wool sheep[J]. Acta Ecologae Animalis Domastici, 2020, 41(7): 52-58 (in Chinese). DOI:10.3969/j.issn.1673-1182.2020.07.010 |
[23] |
孙玲伟. RP-Arg和NCG对妊娠期营养限饲湖羊胎儿和胎盘发育的影响[D]. 博士学位论文. 南京: 南京农业大学, 2017. SUN L W. Effects of RP-Arg and NCG supplementation on fetal and placental development in underfed Hu sheep during pregnancy[D]. Ph. D. Thesis. Nanjing: Nanjing Agricultural University, 2017. (in Chinese) |
[24] |
ZHANG H, SUN L W, WANG Z Y, et al. N-carbamylglutamate and L-arginine improved maternal and placental development in underfed ewes[J]. Reproduction, 2016, 151(6): 623-635. DOI:10.1530/REP-16-0067 |
[25] |
HERRING C M, BAZER F W, JOHNSON G A, et al. Impacts of maternal dietary protein intake on fetal survival, growth, and development[J]. Experimental Biology and Medicine, 2018, 243(6): 525-533. DOI:10.1177/1535370218758275 |
[26] |
ZHANG H, SUN L W, WANG Z Y, et al. Dietary N-carbamylglutamate and rumen-protected L-arginine supplementation ameliorate fetal growth restriction in undernourished ewes[J]. Journal of Animal Science, 2016, 94(5): 2072-2085. DOI:10.2527/jas.2015-9587 |
[27] |
ZHANG H, FAN Y T, ELSABAGH M, et al. Dietary supplementation of L-arginine and N-carbamylglutamate attenuated the hepatic inflammatory response and apoptosis in suckling lambs with intrauterine growth retardation[J]. Mediators of Inflammation, 2020, 2020: 2453537. |
[28] |
SUN L, ZHANG H, FAN Y, et al. Metabolomic profiling in umbilical venous plasma reveals effects of dietary rumen-protected arginine or N-carbamylglutamate supplementation in nutrient-restricted Hu sheep during pregnancy[J]. Reproduction in Domestic Animals, 2017, 52(3): 376-388. DOI:10.1111/rda.12919 |
[29] |
SUN L W, ZHANG H, WANG Z Y, et al. Dietary rumen-protected arginine and N-carbamylglutamate supplementation enhances fetal growth in underfed ewes[J]. Reproduction, Fertility, and Development, 2018, 30(8): 1116-1127. DOI:10.1071/RD17164 |
[30] |
LASSALA A, BAZER F W, CUDD T A, et al. Parenteral administration of L-arginine prevents fetal growth restriction in undernourished ewes[J]. The Journal of Nutrition, 2010, 140(7): 1242-1248. DOI:10.3945/jn.110.125658 |
[31] |
KUMARASAMY V, MITCHELL M D, BLOOMFIELD F H, et al. Effects of periconceptional undernutrition on the initiation of parturition in sheep[J]. American Journal of Physiology.Regulatory, Integrative and Comparative Physiology, 2005, 288(1): R67-R72. DOI:10.1152/ajpregu.00357.2004 |
[32] |
BLOOMFIELD F H, OLIVER M H, HAWKINS P, et al. Periconceptional undernutrition in sheep accelerates maturation of the fetal hypothalamic-pituitary-adrenal axis in late gestation[J]. Endocrinology, 2004, 145(9): 4278-4285. DOI:10.1210/en.2004-0424 |
[33] |
REYNOLDS L P, BOROWICZ P P, CATON J S, et al. Uteroplacental vascular development and placental function: an update[J]. The International Journal of Developmental Biology, 2010, 54(2/3): 355-366. |
[34] |
LASSALA A, BAZER F W, CUDD T A, et al. Intravenous administration of L-citrulline to pregnant ewes is more effective than L-arginine for increasing arginine availability in the fetus[J]. The Journal of Nutrition, 2009, 139(4): 660-665. DOI:10.3945/jn.108.102020 |
[35] |
ZHANG H, ZHAO F F, NIE H T, et al. Dietary N-carbamylglutamate and rumen-protected L-arginine supplementation during intrauterine growth restriction in undernourished ewes improve fetal thymus development and immune function[J]. Reproduction, Fertility, and Development, 2018, 30(11): 1522-1531. DOI:10.1071/RD18047 |
[36] |
LENIS Y Y, ELMETWALLY M A, MALDONADO-ESTRADA J G, et al. Physiological importance of polyamines[J]. Zygote, 2017, 25(3): 244-255. DOI:10.1017/S0967199417000120 |
[37] |
OZER KAYA S, KANDEMIR F M, GUR S, et al. Evaluation of the role of L-arginine on spermatological parameters, seminal plasma nitric oxide levels and arginase enzyme activities in rams[J]. Andrologia, 2020, 52(1): e13439. |
[38] |
汪建国, 杨开伦, 谭世新. 补喂N-氨甲酰谷氨酸(NCG)对种公牛精浆激素水平及精液品质的影响[J]. 当代畜禽养殖业, 2019(3): 8-9. WANG J G, YANG K L, TAN S X. Effects of N-carbamoyl glutamate (NCG) supplementation on seminal plasma hormone level and semen quality of bulls[J]. Modern Livestock and Poultry Breeding Industry, 2019(3): 8-9 (in Chinese). |
[39] |
万轲. N-氨甲酰甘氨酸锌及N-氨甲酰谷氨酸铜的合成及表征[D]. 硕士学位论文. 广州: 广东工业大学, 2016. WAN K. Synthesis and characterization of N-carbamyl glycine zinc and N-carbamyl glutamate copper[D]. Master's Thesis. Guangzhou: Guangdong University of Technology, 2016. (in Chinese) |
[40] |
唐圣芸. 饲料中N-氨基甲酰-L-谷氨酸的检测与其几种金属化合物的合成[D]. 硕士学位论文. 南昌: 南昌大学, 2014. TANG S Y. The detection of N-carbamyl-L-glutamic acid in feed and synthesis of its several metal compounds[D]. Master's Thesis. Nanchang: Nanchang University, 2014. (in Chinese) |