Greene H L, Stifel F B, Hagler L, Herman R H
Am J Clin Nutr. 1975 Oct;28(10):1122-5. doi: 10.1093/ajcn/28.10.1122.
Seven subjects were fed a 3,000 kcal defined formula diet daily for 19 days. Except for one 5-day period, 50% of the total caloric intake was provided as either oral or intravenous glucose. The study was divided into four periods as follows: period I lasted 5 days and provided 50% of calories as glucose; period II lasted 5 days and provided no carbohydrate (70% fat and 30% protein); period III lasted 4 days and provided 50% of calories as intravenous glucose and 50% of calories as oral fat plus protein; period IV lasted 5 days and provided 50% of calories as oral glucose. Intestinal biopsy specimens were taken on days 3 and 5 of each period, except period III when biopsies were done only on day 4. No change in intestinal morphology occurred during the study. The carbohydrate-free diet caused the alpha-glucosidase (maltase and sucrase) activities to decrease significantly from that seen with the glucose diet. Sucrase decreased from 14.4 +/- 1.0 to 7.1 +/- 0.9 mumoles/min per g tissue and maltase decreased from 56.1 +/- 3.4 to 30.0 +/- 2.1 mumoles/min per g tissue. Glycolytic enzyme activities decreased during the carbohydrate-free period (pyruvate kinase decreased from 236 +/- 12 to 78 +/- 8, fructose 1-phosphate aldolase decreased from 147 +/- 6 to 53 +/- 4, fructose-1,6-diphosphate aldolase decreased from 151 +/- 8 to 55 +/- 3, and hexokinase decreased from 21 +/- 3 to 7 +/- 1 nmoles/min per mg protein, respectively). Intravenous glucose caused no change in disaccharidase activities. The enzyme activities during periods I and IV were identical and significantly higher than during period II with the exception of fructose-1,6-diphosphatase which increased during period II as compared with periods I and IV. These findings provide an explanation for the transient period of decreased tolerance to dietary sugars when patients are weaned from total parenteral feedings to enteral feedings.
七名受试者每天摄入3000千卡的特定配方饮食，持续19天。除了一个为期5天的阶段外，总热量摄入的50%通过口服或静脉注射葡萄糖提供。该研究分为四个阶段，具体如下：第一阶段持续5天，50%的热量由葡萄糖提供；第二阶段持续5天，不提供碳水化合物（70%脂肪和30%蛋白质）；第三阶段持续4天，50%的热量由静脉注射葡萄糖提供，50%的热量由口服脂肪加蛋白质提供；第四阶段持续5天，50%的热量由口服葡萄糖提供。在每个阶段的第3天和第5天采集肠道活检标本，第三阶段除外，该阶段仅在第4天进行活检。研究期间肠道形态未发生变化。无碳水化合物饮食导致α-葡萄糖苷酶（麦芽糖酶和蔗糖酶）活性与葡萄糖饮食相比显著降低。蔗糖酶从14.4±1.0降至7.1±0.9微摩尔/分钟每克组织，麦芽糖酶从56.1±3.4降至30.0±2.1微摩尔/分钟每克组织。在无碳水化合物阶段，糖酵解酶活性降低（丙酮酸激酶从236±12降至78±8，果糖-1-磷酸醛缩酶从147±6降至53±4，果糖-1,6-二磷酸醛缩酶从151±8降至55±3，己糖激酶从21±3降至7±1纳摩尔/分钟每毫克蛋白质）。静脉注射葡萄糖对双糖酶活性无影响。第一阶段和第四阶段的酶活性相同，且除果糖-1,6-二磷酸酶外，均显著高于第二阶段，果糖-1,6-二磷酸酶在第二阶段与第一阶段和第四阶段相比有所增加。这些发现为患者从全胃肠外营养过渡到肠内营养时对膳食糖耐受性降低的短暂时期提供了解释。
