Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada.
Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada.
J Nutr. 2024 May;154(5):1571-1581. doi: 10.1016/j.tjnut.2024.03.017. Epub 2024 Mar 26.
Creatine plays a significant role in energy metabolism and positively impacts anaerobic energy capacity, muscle mass, and physical performance. Endogenous creatine synthesis requires guanidinoacetic acid (GAA) and methionine. GAA can be an alternative to creatine supplements and has been tested as a beneficial feed additive in the animal industry. When pigs are fed GAA with excess methionine, creatine is synthesized without feedback regulation. In contrast, when dietary methionine is limited, creatine synthesis is limited, yet, GAA does not accumulate in plasma, urine, or liver.
We hypothesized that portal GAA appearance requires adequate dietary methionine.
Yucatan miniature piglets (17-21 d old; n = 20) were given a 4 h duodenal infusion of complete elemental diets with supplemental GAA plus 1 of 4 methionine concentrations representing either 20%, 80%, 140%, or 200% of the dietary methionine requirement. Arterial and portal blood metabolites were measured along with blood flow to determine mass balance across the gut. [H-methyl] methionine was infused to measure the methionine incorporation rate into creatine.
GAA balance across the gut was highest in the 200% methionine group, indicating excess dietary methionine enhanced GAA absorption. Creatine synthesis in the liver and jejunum was higher with higher concentrations of methionine, emphasizing that the transmethylation of GAA to creatine depends on sufficient dietary methionine. Hepatic GAA concentration was higher in the 20% methionine group, suggesting low dietary methionine limited GAA conversion to creatine, which led to GAA accumulation in the liver.
GAA absorption and conversion to creatine require a sufficient amount of methionine, and the supplementation strategies should accommodate this interaction.
肌酸在能量代谢中起着重要作用，对无氧能量能力、肌肉质量和身体表现有积极影响。内源性肌酸合成需要胍基乙酸（GAA）和蛋氨酸。GAA 可以作为肌酸补充剂的替代品，已在动物产业中作为有益的饲料添加剂进行了测试。当猪在富含蛋氨酸的情况下摄入 GAA 时，肌酸在没有反馈调节的情况下合成。相比之下，当饮食中的蛋氨酸受到限制时，肌酸的合成会受到限制，但 GAA 不会在血浆、尿液或肝脏中积累。
我们假设门静脉 GAA 的出现需要足够的膳食蛋氨酸。
17-21 天大的尤卡坦微型猪（n = 20）接受了 4 小时十二指肠输注全要素饮食，补充 GAA 加 4 种蛋氨酸浓度中的 1 种，分别代表饮食蛋氨酸需求的 20%、80%、140%或 200%。测量动脉和门静脉血液代谢物以及肠道的血流量以确定物质平衡。[H-甲基]蛋氨酸被输注以测量蛋氨酸掺入肌酸的速率。
在蛋氨酸 200%组中，GAA 经肠道平衡最高，表明过量的膳食蛋氨酸增强了 GAA 的吸收。随着蛋氨酸浓度的升高，肝脏和空肠中的肌酸合成也更高，这强调了 GAA 向肌酸的转甲基化取决于充足的膳食蛋氨酸。在蛋氨酸 20%组中，肝脏中的 GAA 浓度更高，这表明低膳食蛋氨酸限制了 GAA 转化为肌酸，导致 GAA 在肝脏中积累。
GAA 的吸收和转化为肌酸需要足够的蛋氨酸，补充策略应适应这种相互作用。
