Comparison of the adaptive changes in disaccharidase, glycolytic enzyme and fructosediphosphatase activities after intravenous and oral glucose in normal men.
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.
D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000446:Aldehyde-Lyases / Q000378:metabolism*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004186:Disaccharidases / Q000378:metabolism*; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism; D005636:Fructosephosphates; D005696:Galactosidases / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D005959:Glucosidases / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D007275:Injections, Intravenous; D007583:Jejunum / Q000201:enzymology*; D008297:Male; D010288:Parenteral Nutrition; D010770:Phosphotransferases / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism
D004040:Dietary Carbohydrates; D005636:Fructosephosphates; D010770:Phosphotransferases; D006593:Hexokinase; D011770:Pyruvate Kinase; D006597:Fructose-Bisphosphatase; D004186:Disaccharidases; D005696:Galactosidases; D005959:Glucosidases; D013393:Sucrase; D000446:Aldehyde-Lyases; D005634:Fructose-Bisphosphate Aldolase; D005947:Glucose