This study tested the hypothesis that dietary supplementation with glycine (Gly) enhances the synthesis and availability of creatine (Cr) in tissues of pigs with intrauterine growth restriction (IUGR). At weaning (21 d of age), IUGR pigs and litter mates with normal birth weights (NBW) were assigned randomly to 1 of the 2 groups, namely, supplementation with 1% Gly or 1.19% l-alanine (isonitrogenous control) to a corn- and soybean meal-based diet. Blood, kidneys, liver, pancreas, jejunum, longissimus lumborum muscle (LLM), and gastrocnemius muscle (GM) were obtained from the pigs within 1 wk after the feeding trial ended at 188 d of age to determine concentrations of guanidinoacetate (GAA), Cr, creatinine, and phosphocreatine (CrP). The organs were also analyzed for activities and mRNA levels for Cr-synthetic enzymes: l-arginine:glycine amidinotransferase (AGAT; forming GAA from Gly and l-arginine) and guanidinoacetate n-methyltransferase (GAMT; converting GAA and l-methionine into Cr). AGAT activity was present in the kidneys, liver, and pancreas, whereas GAMT activity was found in all the organs analyzed. AGAT and GAMT were most active per gram of tissue in the kidneys and pancreas, respectively. Based on tissue mass, the kidneys had the greatest (P < 0.001) AGAT activity per whole organ, followed by the liver, while skeletal muscle had the greatest (P < 0.001) GAMT activity per whole organ, followed by the liver. Thus, the kidneys played a dominant role in forming GAA, whereas skeletal muscle and liver were the major sites for converting GAA into Cr. Dietary supplementation with 1% Gly enhanced AGAT activity in the kidneys and pancreas but reduced GAMT activity in the pancreas and small intestine, therefore directing GAA to the liver and skeletal muscle for Cr production. IUGR selectively reduced the concentration of Cr in LLM among all the organs studied. Except for the GM that had greater mRNA levels for GAMT in IUGR than in NBW pigs, neither Gly nor IUGR affected mRNA levels for the selected genes in the tissues examined. Collectively, these novel results indicate that dietary Gly intake upregulates the Cr-synthetic pathway in swine.

中文翻译：

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日粮甘氨酸补充剂可提高宫内生长受限猪组织中肌酸的可利用性


本研究检验了这样一个假设，即日粮中添加甘氨酸 （Gly） 可增强宫内生长受限 （IUGR） 猪组织中肌酸 （Cr） 的合成和可用性。断奶时（21 日龄），将 IUGR 猪和正常出生体重 （NBW） 的窝仔猪随机分配到 2 组中的 1 组，即在玉米和豆粕基础日粮中补充 1% Gly 或 1.19% l-丙氨酸（同氮对照）。在 188 d 龄饲喂试验结束后 1 wk 内获得猪血液、肾脏、肝脏、胰腺、空肠、腰最长肌 （LLM） 和腓肠肌 （GM），测定胍基乙酸 （GAA） 、Cr 、肌酐和磷酸肌酸 （CrP） 的浓度。还分析了器官中 Cr-合成酶的活性和 mRNA 水平：l-精氨酸：甘氨酸脒基转移酶 （AGAT;从 Gly 和 l-精氨酸形成 GAA）和胍基乙酸 n-甲基转移酶 （GAMT;将 GAA 和 l-蛋氨酸转化为 Cr）。AGAT 活性存在于肾脏、肝脏和胰腺中，而 GAMT 活性存在于所有分析的器官中。肾脏和胰腺中每克组织的 AGAT 和 GAMT 分别最活跃。从组织质量来看，肾脏每器官的 AGAT 活性最高 （P < 0.001），其次是肝脏，而骨骼肌每器官的 GAMT 活性最高 （P < 0.001），其次是肝脏。因此，肾脏在形成 GAA 中起主导作用，而骨骼肌和肝脏是将 GAA 转化为 Cr 的主要部位。 膳食中添加 1% Gly 增强了肾脏和胰腺中的 AGAT 活性，但降低了胰腺和小肠中的 GAMT 活性，因此将 GAA 引导到肝脏和骨骼肌以产生 Cr。IUGR 选择性降低所有研究器官中 LLM。除了 IUGR 中 GAMT 的 mRNA 水平高于 NBW 猪的 GM 外，Gly 和 IUGR 均不影响所检查组织中所选基因的 mRNA 水平。总的来说，这些新结果表明，日粮 Gly 摄入量上调了猪的 Cr 合成途径。