American Journal of Clinical Nutrition, Vol 28, 1122-1125, Copyright © 1975 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Comparison of the adaptive changes in disaccharidase, glycolytic enzyme and fructosediphosphatase activities after intravenous and oral glucose in normal men

HL Greene, FB Stifel, L Hagler and RH Herman

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.