Long‐term effect of early antibiotic exposure on amino acid profiles and gene expression of transporters and receptors in the small intestinal mucosa of growing pigs with different dietary protein levels

Abstract

BACKGROUND: This study evaluated the effects of early antibiotic exposure (EAE) on subsequent amino acid (AA) profiles and small intestinal AA transporter and receptor expression level in pigs with different dietary crude protein (CP) levels. Eighteen litters of piglets were fed creep feed diets, either with or without antibiotics while with sow on day 7. The pigs were weaned at day 23 and fed the same diets until day 42, when random pigs within each group were offered a normal-or low-CP diet, thereby creating four groups. On day 120, the pigs were euthanized, and jejunal and ileal mucosa and digesta were collected for gene-expression and AA-concentration analysis. RESULTS: With the normal-CP diet, EAE increased (P < 0.05) the concentrations of six essential amino acids (EAA) and three non-essential amino acids (NEAA) in serum, four EAAs and four NEAAs in jejunal mucosa, one EAA and two NEAAs in ileal mucosa, five EAAs and three NEAAs in jejunal digesta, and three EAAs and two NEAAs in ileal digesta. Early antibiotic exposure upregulated (P < 0.05) CAT1, ASCT2, ATB 0,+ , CaSR, T1R1, and T1R3 expression in the jejunum, downregulated PepT1 expression with a normal-CP diet. It upregulated (P < 0.05) the expressions of CAT1, ATB 0,+ , ATP1A1, and T1R3 in the ileum with a normal-CP diet.CONCLUSION: These results suggest that EAE has long-term effects on AA profiles, mainly in the jejunum and serum, by increasing AA transporter expression in the intestine, and that these effects may be influenced by dietary CP levels.

Dietary supplementation with citrus extract alters the plasma parameters, circulating amino acid profiles and gene expression of small intestinal nutrient transporters in Chinese yellow‐feathered broilers

“…Blood is the major AA circulating pool and plasma free AAs are the metabolic intermediates for protein nitrogenous anabolism and catabolism 16 . A variety of factors can affect the plasma AA concentrations, including AA transport and metabolism, intracellular protein synthesis and degradation in tissues, 33,45 and intestinal microbial population and activity 46–48 . The transport of dietary AAs and peptides that are released from the intestine into the bloodstream is mediated by specific transporter systems 18 .…”

“…The reaction mixtures and real‐time quantitative PCR conditions for the amplification of all genes were set according to our previous study 24 . To normalize the mRNA expression levels of each target gene, the housekeeping gene β‐actin was used as the internal reference control, and the expression levels were calculated according to the formula 2 −(ΔΔCt) , 33,34 where ΔΔCt = (Ct target − Ct β ‐actin )treatment − (Ct target − Ct β ‐actin )control.…”

Gut microbiome and gastrointestinal nutrition in animals

“…2.1 营养素和非营养物质在消化道内转化、吸收与排出 肠道内营养素，包括蛋白质、碳水化合物和脂肪等，经口腔和胃内消化酶作用，分解成 小分子物质(如葡萄糖、氨基酸和脂肪酸)，这些物质进一步由肠上皮细胞转运体或者营养 素载体进行转运，进而被吸收。未被小肠消化吸收的蛋白质和碳水化合物进入大肠，在大肠 微生物的作用下生成生物胺、短链脂肪酸和氨氮等代谢产物，生物胺和短链脂肪酸参与调节 肠黏膜免疫和代谢，氨氮主要被排出体外 [15] 。除了主要的营养素代谢，一些非营养物质， 如 黄酮类物质 [16] 和胆碱 [17] 等物质，在肠道内代谢转化成小分子物质，被机体吸收。有的植物 成分主要由肠道微生物转化成活性更强的物质，如大豆异黄酮被肠道微生物转化成雌马酚， 对机体起调节作用 [18,19] 。 2.2 消化道营养调节微生物-宿主互作 肠道微生物和宿主具有广泛的互作。消化道营养能够影响微生物组成和功能，改变微生 物的代谢，进而影响宿主功能。多糖类物质被肠道微生物代谢产生短链脂肪酸，包括乙酸、 丙酸和丁酸，是微生物-宿主互作的重要枢纽，可以作为肠上皮的能量来源，或者作为信号 分子作用于靶器官，调节宿主的免疫稳态和能量代谢 [20] 。氨基酸可被肠道微生物产生多种 生物活性物质，例如色胺 [21] 和亚精胺 [22] ，与肠上皮互作，分别调节结肠蠕动和肠道屏障功 能，调节肠道功能。 2.3 消化道营养调节肠道发育 肠道发育是营养素吸收和机体生长的前提，包括肠道形态结构、消化能力、微生物定植 和免疫系统建立等多个方面的发育和成熟 [23] 。消化道营养为肠道发育提供基本保障。近年 来，肠道干细胞在肠道发育中的作用得到广泛关注。日粮中营养素水平，如脂肪和碳水化合 物，能够通过哺乳动物雷帕霉素靶蛋白或 AMP 活化蛋白激酶信号途径，调节肠道干细胞的 再生和分化 [24] 。肠道微生物代谢营养素产生的乳酸，能够调节肠道干细胞发育 [25] 。 2.4 消化道营养调节机体整体代谢与健康 消化道内的营养水平，能够影响机体营养素的分配和利用，调节机体生长和发育。肠道 营养水平和平衡，能通过肠壁吸收功能、肠肝循环、肠脑轴，影响机体整体代谢。例如，低 蛋白营养下调猪空肠上皮氨基酸转运体 CAT1 和 ASCT2 的基因表达，减少血清中精氨酸、 亮氨酸和天冬氨酸的浓度 [26] 。消化道内营养底物的水平，尤其是碳氮底物比例，还通过调 节次级胆酸 [27] 和芳香族氨基酸代谢 [28] ，分别参与肠肝轴、肠脑轴互作，进而影响机体整体 代谢和健康。…”