Restoration of Myo-Inositol Uptake by Aldose Reductase Inhibitor in Human Skin Fibroblasts Cultured in High-Glucose Medium

Okuda, Yukichi; Bannai, Chieko; Nagahama, Michiko; Isaka, Masanori; Yamashita, K.

doi:10.1055/s-2007-1003607

Cited by 5 publications

(1 citation statement)

References 5 publications

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“…For example, Okuda ef al. (35) showed that chronic exposure to extremely high concentrations of glucose, i.e. subculturing fibroblasts in media with 28 and 55 mM glucose, albeit in the presence of myoinositol in excess of 150 gM, resulted in reduced uptake of 50 pM myo-inositol that was partially polyol pathway dependent.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Glucose and Galactose Toxicity on Myo-inositol Transport and Metabolism in Human Skin Fibroblasts in Culture

et al. 1994

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ABSTRACT. Myo-inositol transport and metabolism were studied in cultured human skin fibroblasts exposed to potentially toxic levels of glucose or galactose. Although variable among I I different cell lines, the myo-inositol level in confluent cells, ranging from 10-50 nmol/mg protein, was constant with passage. A high-affinity transport system for myo-inositol had an apparent Kt of 55 pM and V, of 16 pmol/min/mg protein. No obvious relationship existed between cellular levels and transport capacity. Dependency on sodium was complex. When medium sodium was lowered to 23 mM, myo-inositol uptake ceased after about 1 h. However, the initial rate of myo-inositol uptake only showed a sodium dependence at low myo-inositol concentrations. Both phloretin and phloridzin inhibited myo-inositol uptake. Phloridzin had a Ki of 60 pM. and phloretin was either a noncompetitive or uncompetitive inhibitor. Glucose and galactose were only weak competitive inhibitors, with a K1 of 30 mM and 65 mM, respectively. After 24 h of incubation with myo-[2-3Hjinositol, only 10% of the total cell label was incorporated into phospholipid. Compared with control media with 5 mM glucose, the incubation of confluent cells in media with 20 mM glucose had little effect on intracellular glucose and sorbitol, whereas cells incubated in control media supplemented with 5 mM galactose showed a large increase in galactose and polyol levels. In media with more than 200 WM of myo-inositol, neither treatment had an effect on myo-inositol levels after 24 h. The uptake and incorporation of 11 pM myo-[2-3Hjinositol and incorporation into phospholipid were studied after cells had been previously exposed for 24 to 48 h to media supplemented with 15 mM glucose or galactose. Compared with controls, fibroblasts with a 24-h exposure to 20 m M glucose showed a 10% decrease in myo-inositol uptake. When the exposure was extended to 48 h, preconditioning with galactose as well as glucose elicited the same 10% reduction in uptake. Phosphoinositide labeling in fibroblasts exposed to 20 mM glucose was reduced in parallel. These cells offer a unique opportunity for the study of sugar toxicity in human tissue: they can be exposed to high levels of glucose without significant glucose or polyol accumulation~or can be made to accumulate polyol by exposure to moderate levels of galactose. The expression of a hexose-induced reduction in myo-inositol transport required 24 to 48 h of exposure of the fibroblasts to elevated concentrations of glucose or galactose and may not be related to a competitive inhibitory

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Section: Discussionmentioning

confidence: 99%

The Effect of Glucose and Galactose Toxicity on Myo-inositol Transport and Metabolism in Human Skin Fibroblasts in Culture

et al. 1994

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Reduced Na+/K+ ATPase transport activity, resting membrane potential, and bradykinin-stimulated phosphatidylinositol synthesis by polyol accumulation in cultured neuroblastoma cells

et al. 1994

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In these studies we examined the effect of polyol accumulation on neural cell myo-inositol metabolism and properties. Neuroblastoma cells were cultured for two weeks in media containing 30 mM glucose, fructose, galactose or mannose with or without 0.4 mM sorbinil or 250 microM myo-inositol. Chronic exposure of neuroblastoma cells to media containing 30 mM glucose, galactose, or mannose caused a decrease in myo- inositol content and myo-[2-3H]inositol accumulation and incorporation into phosphoinositides compared to cells cultured in unsupplemented medium or medium containing 30 mM fructose as an osmotic control. These monosaccharides each caused an increase in intracellular polyol levels with galactitol > sorbitol = mannitol accumulation. Chronic exposure of neuroblastoma cells to media containing 30 mM glucose, galactose, or mannose caused a significant decrease in Na+/K+ ATPase transport activity, resting membrane potential, and bradykinin-stimulated 32P incorporation into phosphatidylinositol compared to cells cultured in medium containing 30 mM fructose. In contrast, basal incorporation of 32P into phosphatidylinositol or basal and bradykinin-stimulated 32P incorporation into phosphatidylinositol 4,5-bisphosphate were not effected. Each of these cellular functions as well as myo-inositol metabolism and content and polyol levels remained near control values when 0.4 mM sorbinil, an aldose reductase inhibitor, was added to the glucose, galactose, or mannose supplemented media. myo-Inositol metabolism and content and bradykinin-stimulated phosphatidylinositol synthesis were also maintained when media containing 30 mM glucose, galactose, or mannose was supplemented with 250 microM myo-inositol. The results suggest that polyol accumulation induces defects in neural cell myo-inositol metabolism and certain cell functions which could, if they occurred in vivo, contribute to the pathological defects observed in diabetic neuropathy.

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Restoration of nitric oxide production by aldose reductase inhibitor in human endothelial cells cultured in high-glucose medium

et al. 1996

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Restoration of Myo-Inositol Uptake by Aldose Reductase Inhibitor in Human Skin Fibroblasts Cultured in High-Glucose Medium

Abstract: Incubation condition Buffer B (135 mM NaCI) Buffer C (135 mM LiCI) Buffer B + Ouabain (5 mM) Buffer B + Insulin (10-6 M) 10 218±15 47 ± 11 * 109 ±20*

Cited by 5 publications

References 5 publications

The Effect of Glucose and Galactose Toxicity on Myo-inositol Transport and Metabolism in Human Skin Fibroblasts in Culture

The Effect of Glucose and Galactose Toxicity on Myo-inositol Transport and Metabolism in Human Skin Fibroblasts in Culture

Reduced Na+/K+ ATPase transport activity, resting membrane potential, and bradykinin-stimulated phosphatidylinositol synthesis by polyol accumulation in cultured neuroblastoma cells

Restoration of nitric oxide production by aldose reductase inhibitor in human endothelial cells cultured in high-glucose medium

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