LEUCINE TRNOVR RATS W/ NEPHROTIC SYNDROME SUGGEST BODY PROTEIN CONSERVATION

测量了八名患有以下疾病的患者的全身亮氨酸通量 肾病综合征和五名正常受试者的启动常数 静脉输注L-[l-13C]亮氨酸。 13C 的血浆富集 通过气相色谱/质量测定亮氨酸和 13CKIC 通过同位素比质谱法测定呼出的 13CO2。 亮氨酸通量的所有参数，包括亮氨酸的速率 氧化，蛋白质降解释放亮氨酸，并且减少 亮氨酸掺入蛋白质的程度减少 肾病患者。 的值（平均值（SD，umol/kg/hr）） 肾病患者和对照组的参数不同 来自蛋白质降解的亮氨酸，99(6 和 117(12) (p=0.007)； 亮氨酸氧化率 15(7 和 22(3, (p=0.04)) 亮氨酸氧化率 掺入全身蛋白质，8484 10 和 95 6，（p=0.04），以及 净亮氨酸平衡，这是比率之间的差异 蛋白质合成和降解为-15 7 和-22 3，(p=0 .04)。 钍 负值是由于进行了测量 禁食 12 小时后。 蛋白质周转率，根据亮氨酸计算 肾病组和对照组的通量分别为 3.9 ± 0.4 和 4.7 ± 0.3 g/kg/天 对照组（p=0.007）。 氮平衡，仅在 肾病患者的平均正平衡为 0.5 克/天。 对于 在研究前几天，患者摄入了受控饮食，包括 0.84 g 蛋白质/kg/天和 33.3(9 Kcal/kg/天。因此，在这个水平 蛋白质/能量摄入，肾病患者维持氮平衡 也许是因为代谢适应导致了下降 蛋白质降解和氨基酸氧化速率的调节。

Whole body leucine flux was measured in eight patients with nephrotic syndrome and in five normal subjects by primed-constant intravenous infusion of L-[l-13C]leucine. Plasma enrichment of 13C leucine and 13CKIC were measured by gas chromatography/mass spectrometry and exhaled 13CO2 by isotope ratio mass spectrometry. All parameters of leucine flux, including the rates of leucine oxidation, leucine release from protein degradation and, to a lesser extent, leucine incorporation into protein, were reduced in the nephrotic patients. The values (means (SD, umol/kg/hr) of the different parameters in the nephrotic patients and the controls were Leucine derived from protein degradation, 99(6 and 117(12 (p=0.007); leucine oxidation rate 15(7 and 22(3, (p=0.04) the rate of leucine incorporationinto whole body protein, 8484+10 and 95+6, (p=0.04), and net leucine balance which is the difference between the rates of protein synthesis and degradation was -15+7 and -22+3, (p=0 .04). Th e negative values are due to the fact that measurements were made after a 12 hr fast. Protein turnover rate, calculated from leucine flux, were 3.9+0.4 and 4.7+0.3 g/kg/day in the nephrotic and the control grops (p=0.007). Nitrogen balance, measured only in the nephrotic patients, showed a mean positive balance of 0.5 g/day. For days prior to study the patients ingested a controlled diet consisting of 0.84 g protein/kg/d and 33.3(9 Kcal/kg/day. Thus, at this level of protein/energy intake, nephrotic patients maintained nitrogen balance perhaps because of a metabolic adaptation that resulted in a down regulation of protein degradation and amino acid oxidation rates.