Ney D, Bay C, Saudubray J M, Kelts D G, Kulovich S, Sweetman L, Nyhan W L
J Inherit Metab Dis. 1985;8(3):132-42. doi: 10.1007/BF01819298.
A 3-month-old girl and a 13-month-old boy with vitamin B12-unresponsive methylmalonic acidaemia were studied to determine responses to varying levels of protein intake of growth, nitrogen balance and organic acid metabolism. A linear increase in the excretion of methylmalonic acid was observed in both patients above a critical level of protein intake. The inflection point was judged to reflect a ceiling above which amino acid intake exceeded requirements and catabolism was initiated. Below this point in each infant there was a plateau of minimal excretion of methylmalonic acid. Within this plateau level a reasonable rate of growth and metabolic stability were achieved at intakes between 0.70 and 0.75 and between 0.75 and 1.17 g protein kg-1, respectively, indicating that there is a range of protein tolerance and the importance of an individual approach to the provision of protein in patients with methylmalonic acidaemia. In the 3-month-old infant, nitrogen equilibrium was achieved at protein intakes above 0.6 g kg-1 and modest nitrogen retention was attained at a protein intake of 0.75 g kg-1, a level at which the excretion of methylmalonic acid was minimal and weight gain satisfactory. A protein intake of 1.25 g kg-1 was required to achieve a level of nitrogen retention often considered optimal for normal growth; however, this infant demonstrated an elevated excretion of methylmalonic acid and was close to clinical illness at this level of protein intake. The 13-month-old infant demonstrated a normal level of nitrogen retention, minimal excretion of methylmalonic acid, and a satisfactory rate of growth at protein intakes of 1.0-1.17 g kg-1. The values should prove useful guidelines for the management of infants requiring minimal intakes of protein. In studies carried out at 18-20 months of age, supplementation of the basic diet containing 0.75 g kg protein-1 with a mixture of amino acids not containing the precursors of methylmalonic acid was associated with increase of retention of nitrogen and increased concentrations of some essential amino acids in plasma, but effects on growth and the excretion of methylmalonic acid were not significant.
对一名3个月大的女孩和一名13个月大的患有维生素B12无反应性甲基丙二酸血症的男孩进行了研究，以确定不同蛋白质摄入量对生长、氮平衡和有机酸代谢的影响。在两名患者中，当蛋白质摄入量超过临界水平时，观察到甲基丙二酸排泄呈线性增加。拐点被判定反映了一个上限，超过该上限氨基酸摄入量超过需求并启动分解代谢。在每个婴儿的这个点以下，甲基丙二酸排泄处于最低水平的平稳期。在这个平稳期内，分别摄入0.70至0.75克/千克和0.75至1.17克/千克蛋白质时，实现了合理的生长速度和代谢稳定性，这表明存在一定的蛋白质耐受性范围，以及针对甲基丙二酸血症患者提供蛋白质采取个体化方法的重要性。在3个月大的婴儿中，蛋白质摄入量高于0.6克/千克时实现了氮平衡，蛋白质摄入量为0.75克/千克时实现了适度的氮潴留，此时甲基丙二酸排泄最低且体重增加令人满意。要达到通常认为对正常生长最佳的氮潴留水平，需要摄入1.25克/千克的蛋白质；然而，该婴儿在这个蛋白质摄入量水平时甲基丙二酸排泄升高，且接近临床疾病状态。13个月大的婴儿在蛋白质摄入量为1.0至1.17克/千克时，表现出正常的氮潴留水平、最低的甲基丙二酸排泄和令人满意的生长速度。这些数值应为需要最低蛋白质摄入量的婴儿的管理提供有用的指导。在18至20个月大时进行的研究中，在含有0.75克/千克蛋白质的基础饮食中添加不含甲基丙二酸前体的氨基酸混合物，与氮潴留增加和血浆中一些必需氨基酸浓度升高有关，但对生长和甲基丙二酸排泄的影响不显著。
