LEUCINE TRNOVR RATS W/ NEPHROTIC SYNDROME SUGGEST BODY PROTEIN CONSERVATION

在8例患有糖尿病的患者中测量了全身亮氨酸通量。 肾病综合征和五名正常人的启动常数 静脉输注L-[1 - 13 C]亮氨酸。 血浆13 C富集 亮氨酸和13 CKIC通过气相色谱/质谱法测定 通过同位素比质谱法测定呼出的13 CO2。 亮氨酸通量的所有参数，包括亮氨酸的速率 氧化，亮氨酸从蛋白质降解释放，并以较小的 亮氨酸掺入到蛋白质中的程度， 肾病患者 测量的值（平均值（SD，umol/kg/hr）） 肾病患者和对照组的不同参数是 蛋白质降解产生的亮氨酸，99（6）和117（12）（p=0.007）; 亮氨酸氧化率分别为15（7）和22（3）（p=0.04） 转化为全身蛋白，8484 ± 10和95 ± 6，（p=0.04），和 净亮氨酸平衡，即 蛋白质合成和降解分别为-15+7和-22+3（p= 0.04）。 日 e负值是由于进行了测量 在禁食12小时后。 蛋白质周转率，根据亮氨酸计算 在肾病患者和非肾病患者中，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，显示平均正平衡为0.5 g/天。 为 在研究前30天，患者摄入控制饮食， 0.84 g蛋白质/kg/d和33.3（9 Kcal/kg/d. 因此，在这个层面上， 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 调节蛋白质降解和氨基酸氧化速率。

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.