Arevalo Jose A, Leija Robert G, Osmond Adam D, Curl Casey C, Duong Justin J, Huie Melvin J, Masharani Umesh, Brooks George A
Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, United States.
Department of Medicine, University of California, San Francisco, United States.
Am J Physiol Endocrinol Metab. 2024 Oct 1;327(4):E430-E440. doi: 10.1152/ajpendo.00183.2024. Epub 2024 Aug 7.
Lactate, a product of glycolysis, is formed under aerobic conditions. Extensive work has shown lactate flux in young and exercising humans; however, the effect of age is not known. We tested the hypothesis that postprandial lactate shuttling (PLS) would be diminished in older adults. We used [3-C]lactate and [6,6-H]glucose tracers, an oral glucose tolerance test (OGTT), and arterialized blood sampling to determine postprandial lactate rates of appearance (Ra), disappearance (Rd), and oxidation (Rox) in 15 young (28.1 ± 1.4 yr) and 13 older (70.6 ± 2.4 yr) healthy men and women. In young participants, fasting blood [lactate] (≈0.5 mM) rose after the glucose challenge, peaked at 15 min, dipped to a nadir at 30 min, and rose again peaking at 60 min (≈1.0 mM). Initial responses in lactate Ra of older participants were delayed and diminished until 90 min rising by 0.83 mg·kg·min. Lactate Rox was higher throughout the entire trial in young participants by a difference of ∼0.5 mg·kg·min. Initial peaks in lactate Ra and concentration in all volunteers demonstrated the presence of an enteric PLS following an OGTT. Notably, in the systemic, but not enteric, PLS phase, lactate Ra correlated highly with glucose Rd ( = 0.92). Correspondence of second peaks in lactate Ra and concentration and glucose Rd shows dependence of lactate Ra on glucose Rd. Although results show both enteric and systemic PLS phases in young and older study cohorts, metabolic responses were delayed and diminished in healthy older individuals. We used isotope tracers, an oral glucose tolerance test, and arterialized blood sampling to determine postprandial lactate flux rates in healthy young and older men and women. Lactate rates of appearance and oxidation and the lactate-pyruvate exchange were delayed and diminished in both enteric and systemic postprandial lactate shuttle phases in older participants.
乳酸是糖酵解的产物，在有氧条件下生成。大量研究表明了年轻人及运动人群中的乳酸通量；然而，年龄对此的影响尚不清楚。我们检验了这样一个假设：餐后乳酸穿梭（PLS）在老年人中会减少。我们使用[3-C]乳酸和[6,6-H]葡萄糖示踪剂、口服葡萄糖耐量试验（OGTT）以及动脉化采血，来测定15名年轻（28.1±1.4岁）和13名年长（70.6±2.4岁）健康男性和女性的餐后乳酸生成率（Ra）、消失率（Rd）和氧化率（Rox）。在年轻参与者中，葡萄糖激发后空腹血[乳酸]（约0.5 mM）升高，在15分钟时达到峰值，在30分钟时降至最低点，然后再次升高并在60分钟时达到峰值（约1.0 mM）。年长参与者乳酸Ra的初始反应延迟且减弱，直到90分钟时升高了0.83 mg·kg·min。在整个试验过程中，年轻参与者的乳酸Rox始终较高，差值约为0.5 mg·kg·min。所有志愿者乳酸Ra和浓度的初始峰值表明OGTT后存在肠内PLS。值得注意的是，在全身而非肠内PLS阶段，乳酸Ra与葡萄糖Rd高度相关（=0.92）。乳酸Ra和浓度的第二个峰值与葡萄糖Rd的对应关系表明乳酸Ra依赖于葡萄糖Rd。尽管结果显示年轻和年长研究队列中均存在肠内和全身PLS阶段，但健康年长个体的代谢反应延迟且减弱。我们使用同位素示踪剂、口服葡萄糖耐量试验和动脉化采血来测定健康年轻和年长男性和女性的餐后乳酸通量率。年长参与者在肠内和全身餐后乳酸穿梭阶段的乳酸生成率、氧化率以及乳酸-丙酮酸交换均延迟且减弱。
