Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
University of California at Irvine, Orange, CA.
Am J Kidney Dis. 2015 May;65(5):659-73. doi: 10.1053/j.ajkd.2014.09.029. Epub 2015 Feb 12.
Ketoacid (KA) analogues of essential amino acids (EAAs) provide several potential advantages for people with advanced chronic kidney disease (CKD). Because KAs lack the amino group bound to the α carbon of an amino acid, they can be converted to their respective amino acids without providing additional nitrogen. It has been well established that a diet with 0.3 to 0.4 g of protein per kilogram per day that is supplemented with KAs and EAAs reduces the generation of potentially toxic metabolic products, as well as the burden of potassium, phosphorus, and possibly sodium, while still providing calcium. These KA/EAA-supplemented very-low-protein diets (VLPDs) can maintain good nutrition, but the appropriate dose of the KA/EAA supplement has not been established. Thus, a KA/EAA dose-response study for good nutrition clearly is needed. Similarly, the composition of the KA/EAA supplement needs to be reexamined; for example, some KA/EAA preparations contain neither the EAA phenylalanine nor its analogue. Indications concerning when to inaugurate a KA/EAA-supplemented VLPD therapy also are unclear. Evidence strongly suggests that these diets can delay the need for maintenance dialysis therapy, but whether they slow the loss of glomerular filtration rate in patients with CKD is less clear, particularly in this era of more vigorous blood pressure control and use of angiotensin/aldosterone blockade. Some clinicians prescribe KA/EAA supplements for patients with CKD or treated with maintenance dialysis, but with diets that have much higher protein levels than the VLPDs in which these supplements have been studied. More research is needed to examine the effectiveness of KA/EAA supplements with higher protein intakes.
支链氨基酸（BCAA）类似物为患有晚期慢性肾脏病（CKD）的患者提供了几个潜在的优势。由于 KA 缺乏与氨基酸α 碳结合的氨基，因此它们可以在不提供额外氮的情况下转化为各自的氨基酸。已经证实，每天每公斤 0.3 到 0.4 克的蛋白质饮食，补充 KA 和 EAA，可以减少潜在有毒代谢产物的产生，以及钾、磷和可能的钠的负担，同时仍提供钙。这些 KA/EAA 补充的极低蛋白饮食（VLPD）可以保持良好的营养，但 KA/EAA 补充的适当剂量尚未确定。因此，显然需要进行 KA/EAA 剂量反应研究以实现良好的营养。同样，KA/EAA 补充剂的成分也需要重新检查；例如，一些 KA/EAA 制剂既不含有必需氨基酸苯丙氨酸，也没有其类似物。何时开始使用 KA/EAA 补充的 VLPD 治疗的指示也不清楚。有证据强烈表明，这些饮食可以延迟维持性透析治疗的需要，但它们是否能减缓 CKD 患者肾小球滤过率的下降尚不清楚，特别是在当前更积极的血压控制和使用血管紧张素/醛固酮阻断剂的时代。一些临床医生为 CKD 患者或接受维持性透析治疗的患者开处方使用 KA/EAA 补充剂，但这些补充剂的饮食中蛋白质水平远高于研究中使用的 VLPD。需要进行更多的研究来检查高蛋白摄入时 KA/EAA 补充剂的有效性。
