Schadewaldt P, Bodner-Leidecker A, Hammen H W, Wendel U
Deutsches Diabetes Forschungsinstitut, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany.
Pediatr Res. 2001 May;49(5):627-35. doi: 10.1203/00006450-200105000-00004.
Whole-body L-leucine oxidation was assessed in patients with maple syrup urine disease of different severity using oral L-[1-(13)C]leucine bolus tests (38 micromol/kg body weight). Residual whole-body L-leucine oxidation was estimated on the basis of the 3-h kinetics of (13)CO(2) exhalation and (13)C-isotopic enrichment in plasma 4-methyl-2-oxopentanoate using a noncompartmental mathematical approach. In four patients with classical maple syrup urine disease (two females and two males; mean age, 13 +/- 5 y; range, 7--17 y), L-leucine oxidation was too low to be measurable. In two females (aged 11 and 15 y) with a severe variant form of the disease, whole-body L-leucine oxidation was reduced to about 4% of control. In six milder variants (two females and four males; mean age +/- SD, 15 +/- 10 y; range, 6--34 y), the estimates for residual whole-body L-leucine oxidation ranged from 19 to 86% (59 +/- 24%) of control and were substantially higher than the residual branched-chain 2-oxo acid dehydrogenase complex activities in the patients' fibroblasts (10--25% of control). Possible mechanisms are considered that might contribute to a comparatively high residual in vivo L-leucine oxidation in (mild) variant maple syrup urine disease.
采用口服L-[1-(13)C]亮氨酸推注试验（38微摩尔/千克体重），评估了不同严重程度的枫糖尿症患者的全身L-亮氨酸氧化情况。基于呼出(13)CO₂的3小时动力学以及血浆4-甲基-2-氧代戊酸中(13)C-同位素富集情况，使用非房室数学方法估算了全身L-亮氨酸氧化的残余量。在4例典型枫糖尿症患者（2名女性和2名男性；平均年龄13±5岁；范围7-17岁）中，L-亮氨酸氧化过低无法测量。在2例患有严重变异型疾病的女性患者（年龄分别为11岁和15岁）中，全身L-亮氨酸氧化降至对照组的约4%。在6例症状较轻的变异型患者（2名女性和4名男性；平均年龄±标准差为15±10岁；范围6-34岁）中，全身L-亮氨酸氧化残余量的估计值为对照组的19%至86%（59±24%），且显著高于患者成纤维细胞中残余的支链2-氧代酸脱氢酶复合物活性（对照组的10%-25%）。文中考虑了可能导致（轻度）变异型枫糖尿症患者体内L-亮氨酸氧化残余量相对较高的机制。
