Boirie Y, Gachon P, Beaufrère B
Laboratoire de Nutrition Humaine, Université Clermont Auvergne, Clermont-Ferrand, France.
Am J Clin Nutr. 1997 Feb;65(2):489-95. doi: 10.1093/ajcn/65.2.489.
Whole-body and splanchnic protein metabolism were determined in six young (mean age: 22.7 y) and six old (68.2 y) men before and during a standardized meal (41.8 kJ/kg) containing 15.6% protein, by using a combination of intravenous ([13C]leucine) and oral ([2H3]leucine) tracers. In the postabsorptive state, leucine flux and oxidation were similar in both groups when corrected for lean body mass (mean +/- SEM: 1.80 +/- 0.09 compared with 1.79 +/- 0.07 mumol.kg-1.min-1 and 0.55 +/- 0.02 compared with 0.49 +/- 0.04 mumol.kg-1.min-1 for young and old men, respectively, NS). The pattern of response to the meal was also similar in young and old men: increased flux and oxidation, decreased protein breakdown, and unchanged protein synthesis. Splanchnic extraction of dietary leucine was twice as high in elderly men (50 +/- 11% compared with 23 +/- 2%, P < 0.05), was inversely related to plasma leucine concentration (r = -0.771, P < 0.01), and was positively related to body mass index (r = 0.861, P < 0.001). In conclusion, in elderly men there is higher leucine extraction by the gut, liver, or both during feeding, which could lead to a lower peripheral availability of dietary leucine.
采用静脉注射（[¹³C]亮氨酸）和口服（[²H₃]亮氨酸）示踪剂相结合的方法，在6名年轻男性（平均年龄：22.7岁）和6名老年男性（68.2岁）摄入标准化餐（41.8 kJ/kg，含15.6%蛋白质）之前及期间，测定了全身和内脏蛋白质代谢情况。在吸收后状态下，校正去脂体重后，两组的亮氨酸通量和氧化情况相似（年轻男性平均±标准误：1.80±0.09与老年男性1.79±0.07 μmol·kg⁻¹·min⁻¹；年轻男性0.55±0.02与老年男性0.49±0.04 μmol·kg⁻¹·min⁻¹，无显著性差异）。年轻男性和老年男性对餐食的反应模式也相似：通量和氧化增加，蛋白质分解减少，蛋白质合成不变。老年男性对膳食亮氨酸的内脏提取率是年轻男性的两倍（50±11%与23±2%，P<0.05），与血浆亮氨酸浓度呈负相关（r=-0.771，P<0.01），与体重指数呈正相关（r=0.861，P<0.001）。总之，老年男性在进食期间肠道、肝脏或两者对亮氨酸的提取率较高，这可能导致膳食亮氨酸在外周的可利用性降低。
