Comparison of the Pattern of Postprandial Carbohydrate Metabolism After Ingestion of a Glucose Drink or a Mixed Meal*

Abstract

To determine whether the postprandial pattern of carbohydrate metabolism differs after ingestion of an identical amount of glucose as either a drink or as a part of a mixed meal, normal subjects were studied on two occasions. On both occasions, hepatic and extrahepatic glucose metabolism were assessed using the dual isotope and forearm catheterization techniques as well as indirect calorimetry. Plasma glucose, insulin, and C-peptide concentrations and rate of systemic entry of ingested glucose all were lower (P less than 0.05) during the first 15 min after the mixed meal than after the glucose drink. The integrated C-peptide response was greater (P less than 0.05) after the mixed meal, whereas the integrated suppression of glucagon was greater (P less than 0.05) after the glucose drink. Despite these differences in circulating hormone concentrations, after the first 15 min, the rates of systemic entry of ingested glucose, endogenous glucose release, incorporation of carbon dioxide into glucose, and glucose and lipid oxidation as well as nonoxidative glucose storage were virtually the same after the mixed meal and the glucose drink. We conclude that the pattern of postprandial carbohydrate metabolism after ingestion of a glucose meal is remarkably similar to that after ingestion of a more traditional mixed meal. These data suggest that insights regarding the pattern of postprandial carbohydrate metabolism derived from previous studies employing only a glucose drink are likely to pertain to those observed when healthy individuals ingest a meal that contains protein and fat.

Pathogenesis of Pre-Diabetes

“…A primed (12 mg/kg) continuous (0.12 mg ⅐ kg Ϫ1 ⅐ min Ϫ1 ) infusion of [6,6-2 H 2 ]glucose (MassTrace, Woburn, MA) started at 0700. At time 0, i.e., 1000, subjects ingested a standard mixed meal within 15 min, which consisted of three scrambled eggs, 55 g Canadian bacon (or 47 g steak), and Jell-O containing 75 g glucose that was enriched (to ϳ4%) with [1-13 C]glucose, as previously described (18,26). An intravenous infusion of [6-3 H]glucose was started at the same time and infused in a pattern that minimized the change in the ratio of plasma tracer (i.e., [6-3 H]glucose) to plasma meal tracee (i.e., [1-13 C]glucose).…”

Direct assessment of liver glycogen storage by 13C nuclear magnetic resonance spectroscopy and regulation of glucose homeostasis after a mixed meal in normal subjects.

“…used in study A except that 50 Ci [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]glucose was added to allow determination of 14 C specific activity of urinary acetaminophen glucuronide and hence quantitation of the percent contribution of the direct and indirect pathways of glycogen synthesis (17). Urine samples were collected every 2 h for measurement of 14 C-acetaminophen-glucuronide specific activity, and frequent blood samples were taken for measurement of glucose, [ 14 C]glucose, and plasma insulin.…”

“…Considerable caution has to be exercised in extrapolating from such data as the time course of changes after eating is not reproduced and as available evidence suggests that the relative disposition of glucose in muscle and liver differs considerably after administration by the two routes (4)(5)(6). A few studies have followed the fate of a pure glucose load (7)(8)(9)(10), but the metabolic response to a glucose load differs from that after a mixed meal (11)(12)(13).…”

Prediction of Postprandial Glycemic Exposure

“…We have previously shown that although addition of protein and fat to a mixed meal results in a slight delay in meal appearance in comparison to ingestion to the same amount of glucose alone, the overall glycemic profile is virtually identical, with 2-h glucose concentrations in both instances being close to preprandial levels (39). Similarly, because ingestion of complex carbohydrates blunts the postprandial rate of rise of glucose, the concentrations at 2 h are closer to preprandial level than they are to the postprandial peak.…”