Ferraris R P, Vinnakota R R
Department of Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 07103-2714, USA.
J Nutr. 1995 Aug;125(8):2172-82. doi: 10.1093/jn/125.8.2172.
Slow adaptive responses are typical of aged animals. The pace of intestinal adaptation is relatively rapid in young mice but is not known in aged mice. In this study, we determined the time course of adaptation of intestinal nutrient uptake to abrupt and substantial changes in levels of dietary nutrients in young and aged mice. Mice (24-mo-old and 6- to 7-mo-old, controls) were fed a no carbohydrate, high protein diet for 7 d and then were switched to a high carbohydrate, low protein diet for 0, 1, 2, 3 and 5 d. Body weights, feeding rates, intestinal weights and lengths were all independent of diet. Within 1 d after the switch in diet, glucose and fructose uptakes increased in young and aged mice. In both age groups, alanine and aspartate uptakes decreased significantly, whereas proline, leucine and lysine uptakes were independent of diet. In both age groups, total intestinal absorptive capacity for glucose and fructose increased overnight by about 70 and 200%, respectively. Previous studies linked time course of adaptation to rates of enterocyte proliferation. Rates of enterocyte turnover and migration along the crypt/villus axis of proximal, middle and distal small intestine were independent of age. Thus, the time course of intestinal adaptation in aged mice remains largely unchanged from that in young mice, probably because rates of enterocyte proliferation seem independent of age.
缓慢的适应性反应是老年动物的典型特征。肠道适应的速度在年轻小鼠中相对较快，但老年小鼠的情况尚不清楚。在本研究中，我们确定了年轻和老年小鼠肠道营养物质摄取对饮食营养水平突然大幅变化的适应时间进程。将小鼠（24月龄和6至7月龄作为对照）喂食无碳水化合物、高蛋白饮食7天，然后分别在0、1、2、3和5天切换至高碳水化合物、低蛋白饮食。体重、摄食率、肠道重量和长度均与饮食无关。饮食切换后1天内，年轻和老年小鼠的葡萄糖和果糖摄取量均增加。在两个年龄组中，丙氨酸和天冬氨酸摄取量显著下降，而脯氨酸、亮氨酸和赖氨酸摄取量与饮食无关。在两个年龄组中，肠道对葡萄糖和果糖的总吸收能力一夜之间分别增加了约70%和200%。先前的研究将适应的时间进程与肠上皮细胞增殖率联系起来。肠上皮细胞在近端、中端和远端小肠隐窝/绒毛轴上的更新和迁移速率与年龄无关。因此，老年小鼠肠道适应的时间进程与年轻小鼠相比基本保持不变，这可能是因为肠上皮细胞增殖率似乎与年龄无关。
