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  • 1
    ISSN: 1432-0428
    Keywords: Glucose infusion ; in vivo insulin secretion ; in vitro insulin secretion ; beta-cell sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the importance of the level and the duration of glucose stimulation on the in vivo and in vitro insulin response to glucose in normal rats previously submitted to hyperglycaemia. Rats were made hyperglycaemic by a 48-h glucose infusion. Glucose-induced insulin secretion was investigated in vivo by a 20-min hyperglycaemic clamp and in vitro by the isolated perfused pancreas technique, 3 h after the end of the in vivo glucose infusion. In glucose-infused rats, as compared to controls, in vivo incremental plasma insulin values above baseline integrated over the 20-min hyperglycaemic clamp (ΔI) were five times higher during 8 mmol/l glucose clamp, only two times higher in 11 mmol/l glucose clamp and no different in 16.5 mmol/l. Compared to the controls, in vitro incremental plasma insulin concentration above baseline integrated over a 20-min period (ΔI) in glucose-infused rats was 16 times higher in response to 2.8 mmol/l glucose, two times higher in response to 5.5 mmol/l, similar in response to 8.3 mmol/l and significantly lower in response to 16.5 mmol/l. In conclusion, our data suggest that a 48-h hyperglycaemic period results in an increased response of the pancreatic beta cell to low glucose. The response is immediately maximal and can not be increased with higher glucose concentrations. This situation could explain the apparent minimal effect of high concentrations on in vitro insulin secretion in previously hyperglycaemic rats and may provide insights into the sequence of events leading to the impairment of beta-cell function in Type 2 (non-insulin-dependent) diabetes mellitus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Perfused intestine-pancreas ; glucose utilisation lactate production ; insulin release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin release, glucose utilisation and lactate production were investigated using an in vitro perfused rat intestine-pancreas preparation after intraluminal or arterial glucose administration. In the absence of intraluminal glucose administration, both glucose utilisation and lactate production seem to be dependent on the arterial glucose concentration. Despite the different proportions in the portal values of glucose and lactate found at the various arterial glucose concentrations, the percentage of the total carbon atoms from infused glucose recovered in the portal vein remained constant. A significant (p〈0.01) increase in insulin secretion was observed when the arterial glucose concentration was increased from 5.5 to 16.7 mmol/l. After intraluminal administration of glucose (4 g/kg body weight) both as a bolus or as an infusion, the lactate produced and the insulin released by the preparation were not significantly increased with respect to values measured in the absence of intraluminal glucose load. After intraluminal administration of glucose (1 g/kg body weight) as a bolus, the net translocation of glucose from the lumen to the vascular circuit was apparently reduced when the glucose concentration was increased in the perfusate from 2.75 to 11.0 mmol/l; this reduction could be dependent on an increase in the metabolism of absorbed glucose. In conclusion, the functional unit intestine-pancreas seems to play an important role in glucose homeostasis by elaborating the adequate mixture of glucose and lactate that must reach the liver under the various metabolic conditions.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-5233
    Keywords: Acarbose (BAY-5421) ; Glucose metabolism ; Perfusion ; Small intestine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of acarbose on the intestinal metabolism of glucose was investigated using an in vitro perfused preparation of the isolated rat small intestinepancreas. In preparations perfused without intraluminal sucrose administration, the total glucose recovered in the portal effluent and the portal values of lactate, pyruvate and alanine did not depend on whether or not acarbose [1.5 mg/kg body weight (b.w.)] was present in the intestinal lumen. The intestinal glucose and lactate contents were very low at the end of the experiment, and identical with or without acarbose. Insulin and glucagon concentrations remained constant during the whole perfusion period. After intraluminal administration of sucrose a clear increase in portal glucose concentration was observed, which was severely reduced by acarbose administration; no changes in portal levels of lactate, pyruvate, alanine, insulin and glucagon were observed. The intestinal content of sucrose at the end of the study was significantly higher in the presence of acarbose (1.5 mg/kg b.w.), while the glucose concentration was low both with and without acarbose (0.20±0.08 vs 0.29±0.09 mmol/l respectively). These results suggest that acarbose does not influence the metabolic utilization of the glucose being translocated from the lumen.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-5233
    Keywords: Gliclazide ; Intestine-pancreas preparation ; Diabetic rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of insulin (40 μU/ml) and gliclazide (200 μg/ml) on intestinal glucose metabolism was investigated by using an in vitro perfuse intestine-pancreas preparation isolated from normal or streptozotocin-diabetic rats. Glucose, lactate and alanine were measured enzymatically in the portal effluent. The glucose retained by the perfused preparation was reduced (P〈0.05) in diabetic versus control rats. The portal lactate levels were not modified, but alanine portal levels were increased (P〈0.05) in diabetic versus control rats. In the diabetic rats, the level of glucose retained by the preparations was increased (P〈0.05) by the presence of insulin, and insulin plus gliclazide in the perfusate. In the presence of insulin and/or gliclazide, the portal lactate levels were not modified, but the alanine levels were reduced (P〈0.05) to normal values. In preparations from non-diabetic rats, the level of glucose retained was increased (P〈0.05) by gliclazide and insulin plus gliclazide, without modification of the portal lactate and alanine levels. In conclusion, the results show that both insulin and gliclazide increased glucose utilization by perfused intestine-pancreas preparations isolated from diabetic rats. The effect was enhanced when both substances were present simultaneously in the perfusion medium.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-5233
    Keywords: Glucose metabolism ; Intestinal glycolytic activity ; Diabetic rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intestine has a high glycolytic activity, but its metabolic role could be altered in diabetes mellitus. The aim of the present work was to investigate in vivo the glucose retained and the lactate produced by the intestine of normal and diabetic rats and in vitro the effect of different arterial glucose concentrations on glucose utilization and lactate, alanine, and pyruvate production in normal and diabetic rats when the glucose is supplied to the intestine exclusively via the vascular route. In vivo, the normal and diabetic rats retained similar percentages of the arterially supplied glucose (14.7±3.2 and 12.6±2.4, respectively). In vitro, when the preparations were perfused under hyperglycemic conditions, the glucose consumed, as a fraction of the quantity infused, was significantly lower (P〈0.05) in the diabetic (247.0±22.8 μmol/mmol infused glucose) than in normal (315.0±16.3 μmol/mmol infused glucose) rats. The lactate produced was significantly higher in diabetic than in normal rats whether the preparations were perfused under isoglycemic (P〈0.01; 1916.4±124.0 vs 1284±67.7 μmol/mmol consumed glucose) or hyperglycemic (P〈0.05; 1356.4±199.7 vs 898.0±87.3 μmol/mmol consumed glucose) conditions. There was significantly (P〈0.05) greater alanine release from the diabetic (123.7±21.8 μmol/mmol consumed glucose) than from the normal (40.7±10.3 μmol/mmol consumed glucose) rat preparations perfused under isoglycemic conditions.
    Type of Medium: Electronic Resource
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