Sapir D G, Walser M
Metabolism. 1977 Mar;26(3):301-8. doi: 10.1016/0026-0495(77)90077-4.
The alpha-ketoanalogues of the branched-chain amino acids were administered to fasting subjects to determine whether or not they promoted nitrogen sparing. Two fasting studies were carried out in each subject. During the first week of one of the two fasts 4.7 g of a mixture of the alpha-ketoanalogues of valine, leucine, and isoleucine were infused daily. No infusions were administered during the other fast, which served as a control. Urinary urea and calculated total urinary nitrogen were significantly lower during both the week of infusions and the ensuing week of fasting after the infusions were discontinued. Immediately after ketoacid infusions, plasma branched-chain amino acids, including allosioleucine, rose, while alanine and several other amino acids (but not glutamine) fell. There were no differences between the two fasts with respect to ketone bodies, free fatty acids, glucose, insulin, or glucagon concentrations. We conclude that branched-chain ketoacids spare nitrogen early in fasting and that this effect persists after they are metabolized.
将支链氨基酸的α-酮类似物给予禁食受试者，以确定它们是否促进氮的节约。对每个受试者进行了两项禁食研究。在两项禁食中的一项的第一周，每天输注4.7克缬氨酸、亮氨酸和异亮氨酸的α-酮类似物混合物。另一项禁食期间不进行输注，作为对照。在输注周以及输注停止后的禁食周，尿尿素和计算得出的总尿氮均显著降低。酮酸输注后，包括别异亮氨酸在内的血浆支链氨基酸立即升高，而丙氨酸和其他几种氨基酸（但不包括谷氨酰胺）下降。在酮体、游离脂肪酸、葡萄糖、胰岛素或胰高血糖素浓度方面，两项禁食之间没有差异。我们得出结论，支链酮酸在禁食早期节约氮，并且这种作用在它们被代谢后仍然持续。
