Experimental validation of measurements of glucose turnover in nonsteady state.

1978 ◽  
Vol 234 (1) ◽  
pp. E84 ◽  
Author(s):  
J Radziuk ◽  
K H Norwich ◽  
M Vranic
Keyword(s):  
Dispersion Model ◽  
Glucose Production ◽  
Compartment Model ◽  
Sole Source ◽  
Volume Of Distribution ◽  
Endogenous Glucose Production ◽  
The Body ◽  
Glucose Turnover ◽  
Turnover Rates ◽  
Nonsteady State

The aim of the present experiments is to validate, in conscious dogs, the tracer infusion methods of measuring nonsteady turnover rates. This was done in nine experiments performed in four normal dogs by infusing isotopically labeled glucose (2-3H, 6-3H, 1-14C) and monitoring the concentrations of both the labeled and unlabeled substances. The validation is based on the observation that a high exogenous infusion of glucose will suppress endogenous glucose production and become the sole source of glucose in the body. By infusing glucose at a high, time-varying rate, calculating its rate of appearance, (Ra) and comparing it to the infused rate, the method can be verified. The calculations were based on: a) a single-compartment model with a modified volume of distribution; b) a two-compartment model; and c) a generalized dispersion model. The absolute values of the areas of the deviations of the calculated from the infused curves were found to be, respectively, 9.5, 8.4, and 7.8 percent of the total area under the infused curve. It was concluded that the tracer infusion method can reliably measure Ra of glucose when it is changing rapidly, and the system is out of steady state.

Use of a novel triple-tracer approach to assess postprandial glucose metabolism

2003 ◽  
Vol 284 (1) ◽  
pp. E55-E69 ◽  
Author(s):  
Rita Basu ◽  
Barbara Di Camillo ◽  
Gianna Toffolo ◽  
Ananda Basu ◽  
Pankaj Shah ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Glucose Production ◽  
Compartment Model ◽  
Postprandial Glucose ◽  
Endogenous Glucose Production ◽  
Two Compartment Model ◽  
Nonsteady State ◽  
Model Independent ◽  
Endogenous Glucose ◽  
Dual Tracer

Numerous studies have used the dual-tracer method to assess postprandial glucose metabolism. The present experiments were undertaken to determine whether the marked tracer nonsteady state that occurs with the dual-tracer approach after food ingestion introduces error when it is used to simultaneously measure both meal glucose appearance (Ra meal) and endogenous glucose production (EGP). To do so, a novel triple-tracer approach was designed: 12 subjects ingested a mixed meal containing [1-13C]glucose while [6-3H]glucose and [6,6-2H2]glucose were infused intravenously in patterns that minimized the change in the plasma ratios of [6-3H]glucose to [1-13C]glucose and of [6,6-2H2]glucose to endogenous glucose, respectively. Ra meal and EGP measured with this approach were essentially model independent, since non-steady-state error was minimized by the protocol. Initial splanchnic glucose extraction (ISE) was 12.9% ± 3.4%, and suppression of EGP (EGPS) was 40.3% ± 4.1%. In contrast, when calculated with the dual-tracer one-compartment model, ISE was higher ( P < 0.05) and EGPS was lower ( P < 0.005) than observed with the triple-tracer approach. These errors could only be prevented by using time-varying volumes different for Ra meal and EGP. Analysis of the dual-tracer data with a two-compartment model reduced but did not totally avoid the problems associated with marked postprandial changes in the tracer-to-tracee ratios. We conclude that results from previous studies that have used the dual-tracer one-compartment model to measure postprandial carbohydrate metabolism need to be reevaluated and that the triple-tracer technique may provide a useful approach for doing so.

Validation of a tracer technique to determine nonsteady-state ketone body turnover rates in man

1981 ◽  
Vol 240 (3) ◽  
pp. E253-E262 ◽  
Author(s):  
U. Keller ◽  
G. E. Sonnenberg ◽  
W. Stauffacher
Keyword(s):  
Ketone Body ◽  
Specific Activity ◽  
Ketone Bodies ◽  
Compartment Model ◽  
Volume Of Distribution ◽  
Turnover Rates ◽  
Production Rates ◽  
Nonsteady State ◽  
Body Production ◽  
Beta Hydroxybutyrate

The features of a single-compartment model of total ketone bodies were evaluated using primed constant infusions of [3-14C]acetoacetate (AcAc) and of D-[3-14C]beta-hydroxybutyrate (beta OHB) in 12 postabsorptive subjects. The volume of distribution (VD) of AcAc was 0.18 +/- 0.01 liter/kg (n = 9), and that of beta OHB was similar, 0.18 +/- 0.02 liter/kg (n = 3). The production rate of total ketone bodies was calculated using the combined specific activity of AcAc and of beta OHB. The mean basal total ketone body production rates were similar using either [14C]AcAc (6.5 mumol . kg-1 . min-1) or [14C]beta OHB (6.8 mumol . kg-1 . min-1). To determine the pool fraction that was rapidly mixed during nonsteady state of ketone body inflow, unlabeled AcAc was infused with stepwise increasing and decreasing rates between 5 and 25 mumol . kg-1 . m-1 to mimic nonsteady-state ketone body production rates. The "functional" pool fraction P was determined as the pool fraction that provided the best match between tracer-determined rates of ketone production and rates of AcAc infusion. P of total ketone bodies was almost equal to 1 using either [14C]AcAc (1.05 +/- 0.16) or [14C]beta OHB (1.00 +/- 0.06), suggesting rapid mixing of ketone bodies throughout the entire pool. The described pool model may be used to determine total ketone body kinetics during acute perturbations of the steady state.

scholarly journals Absorption and metabolism of glucose by the mesenteric-drained viscera of sheep fed on dried-grass or ground, maize-based diets

1985 ◽  
Vol 54 (2) ◽  
pp. 449-458 ◽  
Author(s):  
A. N. Janes ◽  
T. E. C. Weekes ◽  
D. G. Armstrong
Keyword(s):  
Small Intestine ◽  
Turnover Rate ◽  
Glucose Utilization ◽  
Venous Blood ◽  
Glucose Production ◽  
Glucose Absorption ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Glucose Turnover ◽  
Total Glucose

1. Sheep fitted with re-entrant canulas in the proximal duodenum and terminal ileum were used to determine the amount of α-glucoside entering, and apparently disappearing from, the small intestine when either dried-grass or ground maize-based diets were fed. The fate of any α-glucoside entering the small intestine was studied by comparing the net disappearance of such a-glucoside from the small intestine with the absorption of glucose into the mesenteric venous blood.2. Glucose absorption from the small intestine was measured in sheep equipped with catheters in the mesenteric vein and carotid artery. A continuous infusion of [6-3H]glucose was used to determine glucose utilization by the mesenteric-drained viscera and the whole-body glucose turnover rate (GTR).3. The amounts of α-glucoside entering the small intestine when the dried-grass and maize-based diets were given were 13.9 (SE 1.5) and 95.4 (SE 16.2) g/24 h respectively; apparent digestibilities of such α-glucoside in the small intestine were 60 and 90% respectively.4. The net absorption of glucose into the mesenteric venous blood was —2.03 (SE 1.20) and 19.28 (SE 0.75) mmol/h for the dried-grass and maize-based diets respectively. Similarly, total glucose absorption amounted to 1.52 (SE 1.35) and 23.33 (SE 1.86) mmol/h (equivalent to 7 and 101 g/24 h respectively). These values represented 83 and 11 1% of the a-glucoside apparently disappearing from the small intestine, determined using the re-entrant cannulated sheep.5. Total glucose absorption represented 8 and 61% of the whole-body GTR for the dried-grass and maize-based diets respectively. Endogenous glucose production was significantly lower when the sheep were fed on the maize-based diet compared with the dried-grass diet.6. The mesenteric-drained viscera metabolized a small amount of glucose, equivalent to 234 and 17% of the total glucose absorbed for the dried-grass and maize-based diets respectively.7. It is concluded that a large proportion of the starch entering the small intestine of sheep given a maize-based diet is digested and absorbed as glucose, and thus contributes to the whole-body GTR.

scholarly journals Postprandial glucose fluxes and insulin sensitivity during exercise: A study in healthy individuals

2013 ◽  
Vol 305 (4) ◽  
pp. E557-E566 ◽  
Author(s):  
Michele Schiavon ◽  
Ling Hinshaw ◽  
Ashwini Mallad ◽  
Chiara Dalla Man ◽  
Giovanni Sparacino ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Healthy Subjects ◽  
Acute Exercise ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Fat Free Mass ◽  
Glucose Turnover ◽  
Sensitivity Index ◽  
Moderate Exercise ◽  
Insulin Sensitivity Index

Quantifying the effect size of acute exercise on insulin sensitivity (SIexercise) and simultaneous measurement of glucose disappearance (Rd), endogenous glucose production (EGP), and meal glucose appearance in the postprandial state has not been developed in humans. To do so, we studied 12 healthy subjects [5 men, age 37.1 ± 3.1 yr, body mass index 24.1 ± 1.1 kg/m2, fat-free mass (FFM) 50.9 ± 3.9 kg] during moderate exercise at 50% V̇o2max for 75 min, 120–195 min after a triple-tracer mixed meal consumed at time 0. Tracer infusion rates were adjusted to achieve constant tracer-to-tracee ratio and minimize non-steady-state errors. Glucose turnover was estimated by accounting for the nonstationary kinetics introduced by exercise. Insulin sensitivity index was calculated in each subject both in the absence [time ( t) = 0–120 min, SIrest] and presence ( t = 0–360 min, SIexercise) of physical activity. EGP at t = 0 min (13.4 ± 1.1 μM·kg FFM−1·min−1) fell at t = 120 min (2.4 ± 0.4 μM·kg FFM−1·min−1) and then rapidly rose almost eightfold at t = 180 min (18.2 ± 2.6 μM·kg FFM−1·min−1) before gradually falling at t = 360 min (10.6 ± 0.9 μM·kg FFM−1·min−1). Rd rapidly peaked at t = 120 min at the start of exercise (89.5 ± 11.6 μM·kg FFM−1·min−1) and then gradually declined at t = 195 min (26.4 ± 3.3 μM·kg FFM−1·min−1) before returning to baseline at t = 360 min. SIexercise was significantly higher than SIrest (21.6 ± 3.7 vs. 12.5 ± 2.0 10−4 dl·kg−1·min−1 per μU/ml, P < 0.0005). Glucose turnover was estimated for the first time during exercise with the triple-tracer technique. Our results, applying state-of-the-art techniques, show that moderate exercise almost doubles postprandial insulin sensitivity index in healthy subjects.

Quantitative aspects of glucose metabolism in pregnant and nonpregnant sheep

1963 ◽  
Vol 204 (1) ◽  
pp. 147-152 ◽  
Author(s):  
E. N. Bergman
Keyword(s):  
Glucose Oxidation ◽  
Glucose Utilization ◽  
The Body ◽  
Glucose Turnover ◽  
Turnover Rates ◽  
Pregnant Sheep ◽  
The Mean ◽  
Total Glucose ◽  
Mean Glucose ◽  
Pool Sizes

Labeled glucose was infused into four groups of ewes: nonpregnant fed; nonpregnant fasted; twin-pregnant fed; and twin-pregnant hypoglycemic and ketonemic. Mean glucose pool sizes were 157 and 127 mg/kg in nonpregnant and pregnant ewes, respectively, with decreased values in both fasting and hypoglycemia. Nonpregnant animals had glucose turnover rates averaging 4.0 g/hr (0.22 g/hr·kg3/4) when fed and only 2.7 g/hr (0.15 g/hr·kg3/4) after fasting. These values were only 60–80% of that of pregnant sheep, implying that glucose utilization due to twin-pregnancy was 20–40% of the total. The mean glucose space was about 27% of the body weight, indicating predominantly extracellular distribution of glucose even in hypoglycemia. In all animals about 8–10% of the exhaled CO2 was found to be derived from glucose oxidation and about one-third of the total glucose turnover was used for CO2 production. Comparisons of these data to values obtained from other mammals indicated further that there is a lower rate of glucose oxidation and metabolism in ruminants.

Regulation of glucose turnover at the onset of exercise in the dog

1992 ◽  
Vol 72 (6) ◽  
pp. 2487-2494 ◽  
Author(s):  
P. D. Miles ◽  
D. T. Finegood ◽  
H. L. Lickley ◽  
M. Vranic
Keyword(s):  
Early Period ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Molar Ratio ◽  
Glucose Turnover ◽  
Abrupt Increase ◽  
Glucoregulatory Hormones ◽  
Exercise Period ◽  
Important Regulator

The early responses of endogenous glucose production (Ra), glucose utilization (Rd), and glucoregulatory hormones to moderate treadmill exercise (12% incline, 100 m/min, 60 min) were examined in dogs. Rd increased rapidly and progressively from the start of exercise. The change in Ra, as estimated with a variable-volume model of glucose kinetics, was biphasic, with an abrupt increase by 8.5 +/- 2.3 mumol.min-1.kg-1, followed by a delayed further increase that matched Rd 11–22 min after the onset of exercise. The plasma glucagon-to-insulin molar ratio fell slightly at the onset of exercise and then increased gradually. The glucagon-to-insulin ratio was correlated with Ra over the entire exercise period (r = 0.63, P less than 0.0001), but not during the early part of exercise, when Ra increased rapidly. The catecholamine- (epinephrine plus norepinephrine) to-insulin molar ratio was correlated with Ra during the early period (r = 0.52, P less than 0.01) and over the entire period of exercise (r = 0.66, P less than 0.0001). Our results confirm previous demonstrations that the glucagon-to-insulin molar ratio is an important regulator of Ra during exercise. We hypothesize that the catecholamine-to-insulin molar ratio is important during the early period of exercise and possibly during late exercise as an additional regulatory factor to the glucagon-to-insulin molar ratio.

Role of glucagon in countering hypoglycemia induced by insulin infusion in dogs

1991 ◽  
Vol 261 (6) ◽  
pp. E773-E781 ◽  
Author(s):  
R. L. Dobbins ◽  
C. C. Connolly ◽  
D. W. Neal ◽  
L. J. Palladino ◽  
A. F. Parlow ◽  
...  
Keyword(s):  
Insulin Infusion ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Glucose Turnover ◽  
Major Contributor ◽  
Normal Response ◽  
Counterregulatory Hormones ◽  
Exogenous Glucose ◽  
Experimental Protocols

The aim of the present study was to characterize the role of glucagon in countering the prolonged hypoglycemia resulting from insulin infusion and to determine whether its effect is manifest through glycogenolysis and/or gluconeogenesis. Two groups of 18-h fasted somatostatin-treated dogs were given intraportal insulin at 5 mU.kg-1.min-1. In one group (SimGGN; n = 6), glucagon was infused intraportally so as to mimic the normal response to hypoglycemia. In a second group (BasGGN; n = 6), glucagon was infused at a basal rate. Glucose turnover and gluconeogenesis were assessed by combining tracer and hepatic balance techniques. Exogenous glucose was infused as needed to maintain equivalent hypoglycemia at approximately 45 mg/dl in the two groups. Although glucagon concentrations were significantly different, the levels of other counterregulatory hormones were equivalent in both experimental protocols. Endogenous glucose production (EGP) in SimGGN doubled from 2.4 +/- 0.2 to 5.4 +/- 0.8 mg.kg-1.min-1 by 1 h before dropping to 4.5 +/- 0.2 mg.kg-1.min-1 in the 3rd h of insulin infusion. EGP in BasGGN was initially 2.5 +/- 0.1 mg.kg-1.min-1, unchanged by 1 h, and increased to 3.9 +/- 0.2 mg.kg-1.min-1 by the 3rd h of insulin infusion. In the 1st h of insulin infusion, the rise in gluconeogenesis in both groups was equal and represented only a small part of total EGP. By the 3rd h, gluconeogenesis was the major contributor to total EGP, and gluconeogenic efficiency increased significantly more in SimGGN than BasGGN (261 vs. 140%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Metabolism of glucose in hyper- and hypo-thyroid rats in vivo. Relation of catecholamine actions to thyroid activity in controlling glucose turnover

1979 ◽  
Vol 182 (2) ◽  
pp. 585-592 ◽  
Author(s):  
F Okajima ◽  
M Ui
Keyword(s):  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Rate Coefficients ◽  
Glucose Turnover ◽  
Turnover Rates ◽  
Beta Adrenergic ◽  
Thyroid State ◽  
Adrenergic Antagonist ◽  
6 Hydroxydopamine

1. In euthyroid rats, treatment with reserpine of 6-hydroxydopamine, which deprived neuronal terminals of catecholamines, resulted in increases in rates and rate coefficients for blood glucose turnover in the starved states as determined by decay of [U-14C,6-3H]-glucose. Conversely, the injection of adrenaline or noradrenaline into starved euthyroid rats caused a marked decrease in rate coeeficients for glucose turnover. There was no change in the percentage glucose recycling under these conditions. 2. Adrenaline and noradrenaline caused more pronounced hyperglycaemia in hyperthyroid than in euthyroid rats owing to the greater activation of hepatic glucose production. 3. The increase in glucose turnover characteristics of hyperthyroidism was observed even after treatment with an alpha- or beta-adrenergic antagonist, showing the insignificant role of the balance between alpha- and beta-adrenergic receptors in the thyroid-dependent metabolic changes. 4. Rate coefficients for glucose turnover were not affected by reserpine treatment or catecholamine injections when rats had been rendered hyperthyroid. 5. Thus catecholamines are direct determinants of glucose-turnover rates in the starved state, and depend to some extent on the prevailing thyroid state.

Estimation of glucose production during exercise with a one-compartment variable-volume model

1992 ◽  
Vol 72 (6) ◽  
pp. 2501-2509 ◽  
Author(s):  
D. T. Finegood ◽  
P. D. Miles ◽  
H. L. Lickley ◽  
M. Vranic
Keyword(s):  
Specific Activity ◽  
Glucose Production ◽  
Compartment Model ◽  
Accurate Estimate ◽  
Endogenous Glucose Production ◽  
Single Step ◽  
Regression Method ◽  
Variable Volume ◽  
Volume Model ◽  
Fixed Volume

A variable-volume one-compartment model of glucose kinetics and step increases in the rate of tracer infusion were examined for estimation of endogenous glucose production (Ra) during moderate exercise in dogs. A primed infusion of D-[3–3H]glucose was left constant or increased 1.5-, 2-, 3-, 4-, or 5-fold at the onset of a 60-min period of exercise. Application of a regression method, in which Ra and the effective distribution volume were estimated over time, revealed dynamic changes in Ra that were not evident during the constant tracer infusion with a fixed-volume model. Application of the fixed-volume model to studies performed with a two- or three-fold step increase in tracer resulted in the lowest sum-of-squares difference from the regression method. Our results demonstrate that application of a variable-volume model can be achieved during exercise by enrichment of the plasma specific activity through step increases in the rate of tracer infusion and application of a regression method. Alternately, estimates of Ra with a fixed-volume model can be improved by enrichment of the plasma specific activity through a single step increase in the rate of tracer infusion. Our results suggest that when endogenous Ra is changing rapidly, such as at the onset of exercise, these methods will provide a more accurate estimate of Ra than the standard fixed-volume model and constant tracer infusion.

Glucose metabolism in pregnant sheep when placental growth is restricted

1989 ◽  
Vol 257 (2) ◽  
pp. R350-R357 ◽  
Author(s):  
J. A. Owens ◽  
J. Falconer ◽  
J. S. Robinson
Keyword(s):  
Glucose Metabolism ◽  
Glucose Utilization ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Gravid Uterus ◽  
Glucose Turnover ◽  
Fetal Sheep ◽  
Arterial Blood ◽  
Pregnant Sheep ◽  
Endogenous Glucose

The effect of restricting placental growth on glucose metabolism in pregnant sheep in late gestation was determined by primed constant infusions of D-[U-14C]- and D-[2-3H]glucose and antipyrine into fetuses of six control sheep and six sheep from which endometrial caruncles had been removed before pregnancy (caruncle sheep). In the latter, placental and fetal weights were reduced, as was the concentration of glucose in fetal arterial blood. Fetal glucose turnover in caruncle sheep was only 52-59% of that in controls, largely because of lower umbilical loss of glucose back to the placenta (38-39% of control) and lower fetal glucose utilization (61-74% of control). However, fetal glucose utilization on a weight-specific basis was similar in control and caruncle sheep. Significant endogenous glucose production occurred in control and caruncle fetal sheep. Maternal glucose production and partition of glucose between the gravid uterus and other maternal tissues were similar in control and caruncle sheep. In conclusion, when placental and fetal growth are restricted, fetal glucose utilization is maintained by reduced loss of glucose back to the placenta and mother and by maintaining endogenous glucose production.

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