Nutrient extraction by cold-exposed mice: a test of digestive safety margins.
Nutrient extraction by cold-exposed mice: a test of digestive safety margins.
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DOI：
10.1152/ajpgi.1991.261.4.g608
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发表时间：
1991-10
期刊：
影响因子：
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通讯作者：
E. Toloza;Mandy M. Lam;Jared M. Diamond
中科院分区：
文献类型：
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作者：
E. Toloza;Mandy M. Lam;Jared M. Diamond
我们检查了“安全裕度”的大小（如果有的话），即小肠每日吸收营养物质的能力超过了这些营养物质的日常摄入量。人们普遍认为这种安全裕度（也称为储备能力）非常大。作为一项测试，我们突然将小鼠从 22 至 6 摄氏度的环境温度转移，并测量了接下来 28 天的食物摄入量、表观消化效率、肠道形态测量以及肠道刷状缘对 D-葡萄糖和 L-脯氨酸的摄取能力。食物摄入量在前 12 小时内跃升 68%，并在 2 天内上升至新的稳定水平，是之前摄入量的 2.5 倍。然而，即使在最初的 12 小时内，表观消化效率也保持不变，肠道转运时间也保持不变，这意味着至少存在一定的安全裕度。然而，小肠、大肠、肝脏、肾脏和脾脏的质量在 4 天内增加了 16-20%。每毫克肠道对葡萄糖和脯氨酸的摄取量增加了约 5%，因此肠道对这些溶质的总摄取能力增加了 24-26%。动物的肠道适应通过这些增加的摄取能力来表达，这意味着食物摄入新平台值的安全裕度将会非常狭窄。计算的总吸收能力与测量的膳食摄入量的比较表明，22℃下小鼠的安全裕度约为220-300%，肠道适应前6℃下小鼠的安全裕度仅为27-50%，但肠道适应后6℃下小鼠的安全裕度为60-88%。
We examined the size of the "safety margin," if any, by which the small intestine's daily capacities to absorb nutrients exceed prevailing daily intakes of those nutrients. This safety margin, also known as reserve capacity, is widely assumed to be enormously large. As a test, we suddenly transferred mice from an ambient temperature of 22 to 6 degrees C and measured food intake, apparent digestive efficiency, intestinal morphometrics, and intestinal brush-border uptake capacities for D-glucose and L-proline over the next 28 days. Food intake jumped 68% within the first 12 h and rose in 2 days to a new plateau level 2.5 times the previous intake. Nevertheless, apparent digestive efficiency remained unchanged, even within the first 12 h, and intestinal transit times also remained unchanged, implying the existence of at least some safety margin. Masses of the small and large intestine, liver, kidneys, and spleen nevertheless increased within 4 days by 16-20%. Glucose and proline uptakes per milligram intestine increased by approximately 5%, so that the intestine's summed uptake capacities for these solutes increased by 24-26%. The animal's intestinal adaptation expressed in these increased uptake capacities implies that safety margins at the new plateau value of food intake would otherwise have been dangerously narrow. Comparison of calculated summed uptake capacities with measured dietary intakes suggests that safety margins are approximately 220-300% in mice at 22 degrees C, only 27-50% in mice at 6 degrees C before intestinal adaptation, but 60-88% in mice at 6 degrees C after intestinal adaptation.