Abstract：
Our purpose was to determine how age affects metabolic flexibility and underlying glucose kinetics in healthy young and older adults. Therefore, glucose and lactate tracers along with pulmonary gas exchange data were used to determine glucose kinetics and respiratory exchange ratios [RER = carbon dioxide production (V̇co2)/oxygen consumption (V̇o2)] during a 2-h 75-g oral glucose tolerance test (OGTT). After an 12-h overnight fast, 28 participants, 15 young (21-35 yr; 7 men and 8 women) and 13 older (60-80 yr; 7 men and 6 women), received venous primed-continuous infusions of [6,6-2H]glucose and [3-13C]lactate with a [Formula: see text] bolus. After a 90-min metabolic stabilization and tracer equilibration period, volunteers underwent an OGTT. Arterialized glucose concentrations ([glucose]) started to rise 15 min post glucose consumption, peaked at 60 min, and remained elevated. As assessed by rates of appearance (Ra) and disposal (Rd) and metabolic clearance rate (MCR), glucose kinetics were suppressed in older compared to young individuals. As well, unlike in young individuals, fractional gluconeogenesis (fGNG) remained elevated in the older population after the oral glucose challenge. Finally, there were no differences in 12-h fasting baseline or peak RER values following an oral glucose challenge in older compared to young men and women, making RER an incomplete measure of metabolic flexibility in the volunteers we evaluated. Our study revealed that glucose kinetics are significantly altered in a healthy aged population after a glucose challenge. Furthermore, those physiological deficits are not detected from changes in RER during an OGTT.NEW & NOTEWORTHY To determine metabolic flexibility in response to an OGTT, we studied healthy young and older men and women to determine glucose kinetics and changes in RER. Compared to young subjects, glucose kinetics were suppressed in older healthy individuals during an OGTT. Surprisingly, the age-related changes in glucose flux were not reflected in RER measurements; thus, RER measurements do not give a complete view of metabolic flexibility in healthy individuals.
摘要：
我们的目的是确定年龄如何影响健康的年轻人和老年人的代谢灵活性和潜在的葡萄糖动力学。因此,葡萄糖和乳酸示踪剂，在2小时75克口服葡萄糖耐量试验(OGTT)期间,我们使用肺气体交换数据来确定葡萄糖动力学和呼吸交换比(RER=CO2/O2).经过12小时的夜间禁食，28人，15岁（21-35岁。；7名男性和8名女性）和13岁以上（60-80岁。；7名男性和6名女性）接受静脉灌注连续输注[6,6-2H]葡萄糖，和[3-13C]乳酸盐与H13CO3-丸剂。经过90分钟的代谢稳定和示踪剂平衡期，志愿者接受了OGTT。葡萄糖消耗后15分钟，动脉化葡萄糖浓度（[葡萄糖]）开始上升，在60分钟达到峰值，并保持高位。根据出现率(Ra)评估，与年轻人相比，老年人的处置（Rd）和代谢清除（MCR）葡萄糖动力学受到抑制。同样,与年轻人不同，口服葡萄糖激发后，老年人群的糖异生分数（fGNG）仍然升高。最后,与年轻男性和女性相比，老年人口服葡萄糖挑战后12小时空腹基线或RER峰值没有差异。使RER成为我们评估的志愿者代谢灵活性的不完整量度。我们的研究表明，在葡萄糖挑战后，健康老年人群的葡萄糖动力学发生了显着变化。Further,这些生理缺陷不能从OGTT期间RER的变化中检测到。
