Upper limit for intestinal absorption of a dilute glucose solution in men at rest

Abstract

We studied gastric and intestinal function by gastric intubation/intestinal perfusion in six healthy male volunteers to evaluate optimal use of a 6% glucose-electrolyte (GES) solution. Gastric volume, residual volume, emptying rate, and secretion were measured for an initial 763 +/- 19 ml gastric load of GES and at the beginning and end of four additional gastric loads (2.2 ml.kg-1; approximately 180 ml) given at 10-min intervals. The relatively high gastric (713 +/- 58 ml) and residual (507 +/- 26 ml) volumes maintained a high gastric emptying rate (19.5 +/- 1.4 ml.min-1). Composition of the GES emptied into the duodenum was also measured in this first experiment. In a second experiment, this modified solution was infused (triple lumen tube) into the duodenum at a rate equal to gastric emptying rate, or at 38 or 77% greater rates. Absorption of water (11.3-12.9 ml.h-1.cm-1) and glucose 4.3-5.6 mmol.h-1.cm-1) were similar at all perfusion rates during the second experiment. We conclude that duodenojejunal segmental absorption rates of water and glucose produced by a rapid, sustained gastric emptying rate cannot be increased by delivering a greater load of glucose and water by intestinal perfusion.

Physical Activity/Exercise and Type 2 Diabetes

“…As a consequence, limitations to the oxidation of ingested glucose may shift at different work intensities: low muscle demand limits glucose oxidation at light work rates, whereas absorption from the gastrointestinal tract limits it at high work rates (61). In humans, the maximum absorption rate of carbohydrate in the gut during exercise is about 1 g/min (62).…”

Plasma glucose kinetics during prolonged exercise in trained humans when fed carbohydrate

“…The appearance of ingested glucose increased throughout exercise, implying no splanchnic limitation to ingested glucose bioavailability. Our feeding regimen produced an average glucose intake of 1.3 g/min during exercise, approximately the same as the estimated upper limit for gastrointestinal glucose absorption, albeit under resting conditions (6). It is possible that ingestion of a larger amount of carbohydrate could result in a splanchnic limitation to ingested glucose appearance, as we have observed with a 10% glucose solution (18).…”

“…Venous blood samples were obtained at rest, at 30-min intervals during the first 2 h of exercise, and then at 15-min intervals until fatigue for later measurement of plasma glucose, [6,6 2 H]glucose enrichment, and [3-3 H]glucose specific activity. Additional blood was obtained at rest, at 60-min intervals, and at fatigue for measurement of plasma lactate, free fatty acids (FFA), insulin, and glucagon.…”

Water and Solute Absorption From Carbohydrate-Electrolyte Solutions in the Human Proximal Small Intestine: A Review and Statistical Analysis

“…It is important to note that various infusion rates were used in the intestinal perfusion studies that we reviewed, but whether different infusion rates affect water absorption is still debatable (Duchman et al, 1997;Modigliani & Bernier, 1971;Sladen & Dawson, 1969). Comparing two separate studies (Hunt, Elliott, & Farthing, 1989;Leiper & Maughan, 1992) perfusing two almost identical solutions (solution A: glucose 65 mmol/L, sodium 68 mmol/L, and osmolality 235 mOsm vs. solution B: glucose 69 mmol/L, sodium 66 mmol/L, and osmolality 234 mOsm) in the human jejunum at 10 or 15 ml/min suggests that water absorption was similar (0.16 vs. 0.12 ml · cm -1 · min -1…”