Hu Shengdi, Long David W, Bazer Fuller W, Burghardt Robert C, Johnson Gregory A, Wu Guoyao
Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA.
Animals (Basel). 2025 Jun 23;15(13):1855. doi: 10.3390/ani15131855.
Glycine has the greatest rate of deposition in whole-body proteins among all amino acids in neonates, but its provision from sow's milk meets only 20% of the requirement of suckling piglets. The results of our recent studies indicate that piglets with intrauterine growth restriction (IUGR) have a reduced ability to synthesize glycine. The present study determined the role of glycine in the growth of sow-reared IUGR piglets. In Experiment 1, 56 newborn piglets (postnatal day 0) with a low birth weight (<1.10 kg) were selected from 14 litters, providing 4 IUGR piglets/litter that were allotted randomly into one of four treatment groups (14 piglets/group). Piglets received oral administration of either 0, 0.1, 0.2 or 0.4 g glycine/kg body weight (BW) twice daily (i.e., 0, 0.2, 0.4 or 0.8 g glycine/kg BW/day) between 0 and 14 days of age. L-Alanine was used as the isonitrogenous control. The BWs of all piglets were recorded each week during the experiment. Two weeks after the initiation of glycine supplementation, blood and tissue samples were collected for biochemical analyses. In Experiment 2, rates of muscle protein synthesis in tissues were determined on day 14 using the H-phenylalanine flooding dose technique. Compared with piglets in the control group, oral administration of 0.2, 0.4 and 0.8 g glycine/kg BW/day did not affect their milk intake ( > 0.05) but increased ( < 0.05) concentrations of glycine in plasma by 1.52-, 1.94-, and 2.34-fold, respectively, and body weight by 20%, 37%, and 34%, respectively. The dose of 0.4 g glycine/kg BW/day was the most cost-effective. Consistent with its growth-promoting effect, glycine supplementation stimulated ( < 0.05) the phosphorylation of mechanistic target of rapamycin (MTOR), eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and ribosomal protein S6 kinase beta-1 (p70) as well as protein synthesis in skeletal muscle, compared with the control group. Collectively, oral administration of glycine activated the MTOR signaling pathway in skeletal muscle and enhanced the growth performance of IUGR piglets. These results indicate that endogenous synthesis of glycine is inadequate to meet the needs of IUGR piglets during the suckling period and that oral supplementation with glycine to these compromized neonates can improve their growth performance.
在新生儿的所有氨基酸中，甘氨酸在全身蛋白质中的沉积率最高，但母乳中提供的甘氨酸仅满足哺乳仔猪需求的20%。我们最近的研究结果表明，宫内生长受限（IUGR）仔猪合成甘氨酸的能力降低。本研究确定了甘氨酸在母猪饲养的IUGR仔猪生长中的作用。在实验1中，从14窝仔猪中选出56头出生体重低（<1.10 kg）的新生仔猪（出生后第0天），每窝提供4头IUGR仔猪，随机分配到四个处理组之一（每组14头仔猪）。在0至14日龄期间，仔猪每天口服两次0、0.1、0.2或0.4 g甘氨酸/千克体重（BW）（即0、0.2、0.4或0.8 g甘氨酸/千克BW/天）。L-丙氨酸用作等氮对照。在实验期间每周记录所有仔猪的体重。在开始补充甘氨酸两周后，采集血液和组织样本进行生化分析。在实验2中，在第14天使用H-苯丙氨酸冲击剂量技术测定组织中肌肉蛋白质合成率。与对照组仔猪相比，每天口服0.2、0.4和0.8 g甘氨酸/千克BW对它们的采食量没有影响（P>0.05），但血浆中甘氨酸浓度分别增加了1.52倍、1.94倍和2.34倍（P<0.05），体重分别增加了20%、37%和34%。0.4 g甘氨酸/千克BW/天的剂量最具成本效益。与其促生长作用一致，与对照组相比，补充甘氨酸刺激了雷帕霉素机制靶点（MTOR）、真核起始因子4E结合蛋白1（4E-BP1）和核糖体蛋白S6激酶β-1（p70）的磷酸化以及骨骼肌中的蛋白质合成（P<0.05）。总体而言，口服甘氨酸激活了骨骼肌中的MTOR信号通路，提高了IUGR仔猪的生长性能。这些结果表明，甘氨酸的内源性合成不足以满足IUGR仔猪哺乳期的需求，对这些受损新生儿口服补充甘氨酸可以改善其生长性能。
