Stimulation of Glucose Utilization by Fructose in Isolated Rat Hepatocytes

Fillat, Cristina; Gómèz-Foix, Anna M.; Guinovart, J.J.

doi:10.1006/abbi.1993.1078

Cited by 20 publications

(19 citation statements)

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“…It has been reported that the presence of lower concentrations of fructose increases glucose utilization in hepatocytes, and that higher concentrations of fructose do not affect glucose utilization or rather exert a negative effect on it (CLARK et al, 1979;van SCHAFTINGEN and VANDERCAMMEN, 1989;FILLAT et al, 1993;AGlus and PEAK, 1993). We therefore examined the effect of various concentrations of fructose on GK distribution.…”

Section: Effect Of Fructose Concentration On Gk Distributionmentioning

confidence: 99%

Shuttling of Glucokinase between the Nucleus and the Cytoplasm in Primary Cultures of Rat Hepatocytes: Possible Involvement in the Regulation of the Glucose Metabolism.

Toyoda

Ito

Souma

et al. 1997

Archives of Histology and Cytology

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Section: Effect Of Fructose Concentration On Gk Distributionmentioning

confidence: 99%

Shuttling of Glucokinase between the Nucleus and the Cytoplasm in Primary Cultures of Rat Hepatocytes: Possible Involvement in the Regulation of the Glucose Metabolism.

Toyoda

Ito

Souma

et al. 1997

Archives of Histology and Cytology

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“…When given to intact animals (65) or isolated hepatocytes (37), low fructose loads were shown to increase the intracellular content of fructose-2,6-diphosphate, a potent activator of phosphofructokinase (66). This effect might be secondary to increased G6P content, as fructose-induced activation of glycolysis was not observed in rat hepatocytes incubated in the presence of mannoheptulose, which inhibited glucokinase (37). Pyruvate kinase in the perfused liver has been reported to be activated by only very high fructose loads (1-5 mmol/l) (67).…”

mentioning

confidence: 99%

Inclusion of Low Amounts of Fructose With an Intraduodenal Glucose Load Markedly Reduces Postprandial Hyperglycemia and Hyperinsulinemia in the Conscious Dog

et al. 2002

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Intraportal infusion of small amounts of fructose markedly augmented net hepatic glucose uptake (NHGU) during hyperglycemic hyperinsulinemia in conscious dogs. In this study, we examined whether the inclusion of catalytic amounts of fructose with a glucose load reduces postprandial hyperglycemia and the pancreatic ␤-cell response to a glucose load in conscious 42-hfasted dogs. Each study consisted of an equilibration (؊140 to ؊40 min), control (؊40 to 0 min), and test period (0 -240 min). During the latter period, glucose (44.4 mol ⅐ kg ؊1 ⅐ min ؊1 ) was continuously given intraduodenally with (2.22 mol ⅐ kg ؊1 ⅐ min ؊1 ) or without fructose. The glucose appearance rate in portal vein blood was not significantly different with or without the inclusion of fructose (41.3 ؎ 2.7 vs. 37.3 ؎ 8.3 mol ⅐ kg ؊1 ⅐ min ؊1 , respectively). In response to glucose infusion without the inclusion of fructose, the net hepatic glucose balance switched from output to uptake (from 10 ؎ 2 to 11 ؎ 4 mol ⅐ kg ؊1 ⅐ min ؊1 ) by 30 min and averaged 17 ؎ 6 mol ⅐ kg ؊1 ⅐ min ؊1 . The fractional extraction of glucose by the liver during the infusion period was 7 ؎ 2%. Net glycogen deposition was 2.44 mmol glucose equivalent/kg body wt; 49% of deposited glycogen was synthesized via the direct pathway. Net hepatic lactate production was 1.4 mmol/kg body wt. Arterial blood glucose rose from 4.1 ؎ 0.2 to 7.3 ؎ 0.4 mmol/l, and arterial plasma insulin rose from 42 ؎ 6 to 258 ؎ 66 pmol/l at 30 min, after which they decreased to 7.0 ؎ 0.5 mmol/l and 198 ؎ 66 pmol/l, respectively. Arterial plasma glucagon decreased from 54 ؎ 7 to 32 ؎ 3 ng/l. In response to intraduodenal glucose infusion in the presence of fructose, net hepatic glucose balance switched from 9 ؎ 1 mol ⅐ kg G lucose uptake by the liver contributes in a major way to the disposal of alimentary glucose (1). In healthy humans, 20 -30% of absorbed glucose is taken up by the liver, and hepatic glycogen synthesis accounts for the disposal of about 70% of that amount. Liver glycogen is synthesized by both direct (glucose 3 glucose-6-phosphate [G6P] 3 glucose-1-phosphate 3 uridine 5Ј-diphosphate [UDP] glucose 3 glycogen) and indirect (three carbon unit 3 phosphoenolpyruvate 3 G6P 3 glucose-1-phosphate 3 UDP glucose 3 glycogen) pathways (2). After oral glucose ingestion in the healthy human, 50 -77% of the liver glycogen synthesized is derived via the direct pathway (3-6). The response of the conscious dog is similar to that of humans, with 25-40% of a gastrointestinal glucose load being taken up by the liver and 50 -62% of accumulated hepatic glycogen being synthesized via the direct pathway (7-9).Individuals with diabetes exhibit excessive postprandial hyperglycemia, with a defect in meal-or glucose-induced suppression of endogenous glucose production (10 -15). Only a few studies have examined the effect of type 2 diabetes on splanchnic glucose uptake, and the results from these data are not concordant. Several studies (12,13,15,16) have demonstrated that the greater net splanchnic glucose rel...

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“…A negative value for NHB represents net uptake. (20,49). Therefore, the production of fructose 1-phosphate from fructose and activation of GK by fructose 1-phosphate do not depend on an increase in plasma insulin levels.…”

Section: Discussionmentioning

confidence: 93%

“…In addition, it is known that pyruvate kinase and phosphofructokinase are key regulatory sites in glycolysis. Low-fructose loads when given to intact animals (41) or isolated hepatocytes (20) increased the intracellular content of fructose 2,6-bisphosphate, a potent activator of phosphofructokinase (25). This effect might be secondary to increased glucose 6-phosphate content because fructose-induced activation of glycolysis was not observed in rat hepatocytes incubated in the presence of mannoheptulase which inhibited glucokinase (20).…”

Section: Discussionmentioning

confidence: 99%

“…Low-fructose loads when given to intact animals (41) or isolated hepatocytes (20) increased the intracellular content of fructose 2,6-bisphosphate, a potent activator of phosphofructokinase (25). This effect might be secondary to increased glucose 6-phosphate content because fructose-induced activation of glycolysis was not observed in rat hepatocytes incubated in the presence of mannoheptulase which inhibited glucokinase (20). In perfused liver, pyruvate kinase has been reported to be activated only by very high fructose loads (1-5 mmol/l) (16).…”

Section: Discussionmentioning

confidence: 99%

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Inclusion of low amounts of fructose with an intraportal glucose load increases net hepatic glucose uptake in the presence of relative insulin deficiency in dog

Shiota¹,

Galassetti²,

Igawa³

et al. 2005

American Journal of Physiology-Endocrinology and Metabolism

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-The effect of small amounts of fructose on net hepatic glucose uptake (NHGU) during hyperglycemia was examined in the presence of insulinopenia in conscious 42-h fasted dogs. During the study, somatostatin (0.8 g ⅐ kg Ϫ1 ⅐ min Ϫ1 ) was given along with basal insulin (1.8 pmol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) and glucagon (0.5 ng ⅐ kg Ϫ1 ⅐ min Ϫ1 ). After a control period, glucose (36.1 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) was continuously given intraportally for 4 h with (2.2 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) or without fructose. In the fructose group, the sinusoidal blood fructose level (nmol/ml) rose from Ͻ16 to 176 Ϯ 11. The infusion of glucose alone (the control group) elevated arterial blood glucose (mol/ml) from 4.3 Ϯ 0.3 to 11.2 Ϯ 0.6 during the first 2 h after which it remained at 11.6 Ϯ 0.8. In the presence of fructose, glucose infusion elevated arterial blood glucose (mol/ml) from 4.3 Ϯ 0.2 to 7.4 Ϯ 0.6 during the first 1 h after which it decreased to 6.1 Ϯ 0.4 by 180 min. With glucose infusion, net hepatic glucose balance (mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) switched from output (8.9 Ϯ 1.7 and 13.3 Ϯ 2.8) to uptake (12.2 Ϯ 4.4 and 29.4 Ϯ 6.7) in the control and fructose groups, respectively. Average NHGU (mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) and fractional glucose extraction (%) during last 3 h of the test period were higher in the fructose group (30.6 Ϯ 3.3 and 14.5 Ϯ 1.4) than in the control group (15.0 Ϯ 4.4 and 5.9 Ϯ 1.8). Glucose 6-phosphate and glycogen content (mol glucose/g) in the liver and glucose incorporation into hepatic glycogen (mol glucose/g) were higher in the fructose (218 Ϯ 2, 283 Ϯ 25, and 109 Ϯ 26, respectively) than in the control group (80 Ϯ 8, 220 Ϯ 31, and 41 Ϯ 5, respectively). In conclusion, small amounts of fructose can markedly reduce hyperglycemia during intraportal glucose infusion by increasing NHGU even when insulin secretion is compromised. diabetes mellitus; hyperglycemia; hyperinsulinemia INDIVIDUALS WITH TYPE 2 DIABETES MELLITUS exhibit excessive postprandial hyperglycemia with a defect in meal-or glucoseinduced suppression of endogenous glucose production (18,21,28,34). Several studies (21,28,34) have demonstrated that the greater net splanchnic glucose release in diabetic compared with nondiabetic subjects after glucose injection was due to excessive endogenous glucose production rather than lower initial splanchnic extraction of the ingested glucose. However, the insulin and glucose concentrations differed in the diabetic and nondiabetic subjects in all of those studies, precluding direct comparison of the efficiency of splanchnic glucose uptake. DeFronzo et al. (15) (15), found decreased splanchnic glucose uptake in diabetic subjects. It is known, however, that in the presence of euglycemia and hyperinsulinemia, there is minimal splanchnic glucose uptake (14,15,23,42). Thus the size of the signal in the above studies was very small. Hyperglycemia combined with hyperinsulinemia, on the other hand, substantially increases glucose uptake by the liver (14,23,42). Recently, Basu et al. (5) carried out a hyperglycemic and hyperins...

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Stimulation of Glucose Utilization by Fructose in Isolated Rat Hepatocytes

Cited by 20 publications

References 0 publications

Shuttling of Glucokinase between the Nucleus and the Cytoplasm in Primary Cultures of Rat Hepatocytes: Possible Involvement in the Regulation of the Glucose Metabolism.

Shuttling of Glucokinase between the Nucleus and the Cytoplasm in Primary Cultures of Rat Hepatocytes: Possible Involvement in the Regulation of the Glucose Metabolism.

Inclusion of Low Amounts of Fructose With an Intraduodenal Glucose Load Markedly Reduces Postprandial Hyperglycemia and Hyperinsulinemia in the Conscious Dog

Inclusion of low amounts of fructose with an intraportal glucose load increases net hepatic glucose uptake in the presence of relative insulin deficiency in dog

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