Polyol Metabolism in Monkey‐Kidney Epithelial‐Cell Cultures

Abstract

Cultures1. An investigation of polyol synthesis by monolayer cultures of monkey kidney epithelium cells was undertaken as a consequence of the observation that these cells accumulated high concentrations of acyclic hexitols (200-600 pmol/g protein) when incubated in media containing elevated glucose [590 mg-% (w/v)] concentrations.2. It was established that the acyclic hexitol which accumulated when monkey kidney epithelial cell cultures were incubated in high glucose medium was sorbitol. The involvement of the polyol pathway of metabolism in this phenomenon was implicated from radioactivity incorporation experiments using [U-'4C]glucose substrate (the specific radioactivity of the sorbitol product was 92 % of the specific radioactivity of the added glucose) and from studies involving the use of the aldose reductase inhibitor 3,3'-tetramethylene glutaric acid, which caused marked inhibition of polyol synthesis.3. The intracellular glucose concentration was found to be an important factor regulating the steady state concentrations of the pathway intermediates sorbitol and fructose in monkey kidney epithelial cell cultures. Changes in the oxygen tension in the incubation medium or the presence of the hormones vasopressin, insulin or epinephrine were shown not to affect the concentrations of sorbitol or fructose in monkey kidney epithelial cell cultures incubated in media containing a high glucose concentration.4. Cultures of HeLa Cells, goldfish testes fibroblasts, or ascites tumor cells did not exhibit the same capacity as monkey kidney epithelial cell cultures for sorbitol synthesis. To our knowledge, the present findings constitute the first reported example of polyol pathway activity in cells in monolayer culture.The identification of the enzyme aldose reductase in a large number of mammalian tissues [1,2] has indicated that the polyol pathway of metabolism [3] may be widely distributed in the tissues of mammalian organism. In the seminal vesicle, the polyol pathway probably operates as a mechanism of fructose synthesis from glucose [3]; in other tissues the physiological function of the pathway has yet to be resolved. Attention has been drawn to abnormal operation of the polyol pathway from the reports that high concentrations of sorbitol (approx. 10-100 mmol/kg wet wt) accumulate in lens [4], peripheral nerve [5] and renal papilla [6] in diabetes and that high concentrations of dulcitol accumulate in lens, peripheral nerve, brain, heart and skeletal muscle in the galactosaemic state [7].Enzymes. Alditol : NADP oxidoreductase or aldose reductase (EC 1.1.1.21) ; L-gulonate : NADP oxidoreductase or glucuronate reductase (EC 1.1 .I. 19).A major factor which regulates the metabolism of either glucose or galactose to their respective hexitols via the polyol pathway in these tissues is probably the relatively high Michaelis constant of aldose reductase for the corresponding hexose, viz. approx. 70 and 20 mM respectively for glucose and galactose for the lens enzyme [8]. The rate of intracellular transport of the s...

Aldose Reductase Inhibitors from the Fruiting Bodies of Ganoderma applanatum

“…The inhibitory potencies and IC 50 values on the RLAR enzyme were estimated. As shown in Tables 1 and 2, the IC 50 values of the MeOH and the water extracts were determined to be 1.7 and 8.7 mg/ml, respectively, while that of TMG, a known AR inhibitor, 6) was 0.5 mg/ml. To evaluate the AR inhibitory compounds from G. applanatum, activity-guided fractionation was carried out and their effects on RLAR were tested.…”

Control of glucokinase translocation in rat hepatocytes by sorbitol and the cytosolic redox state

“…The inhibitory effect of 3,3'-tetramethyleneglutaric acid, an inhibitor of aldose reductase [19,20], on glucose-induced, but not fructose-or sorbitol-induced, glucokinase translocation suggests that the glucose effect may be mediated via conversion into sorbitol. However, whether this inhibitor might have other nonspecific effects cannot be excluded from the present study.…”

“…Sorbitol accumulation in liver has been demonstrated in diabetic rats [18]. To investigate the possible role of conversion of glucose into sorbitol, the effects of 3,3'-tetramethyleneglutaric acid, an inhibitor of aldose reductase [19,20], were examined. 3,3'-Tetramethyleneglutaric acid (5 mM) inhibited the stimulation of glucokinase release caused by 10-20 mM glucose, but had no effect on stimulation by 1 mM fructose or 1 mM sorbitol ( (Figure 1) therefore support the hypothesis that the binding protein of glucokinase may be involved in fructose-induced translocation.…”

Up‐regulation of aldolase A and methylglyoxal production in adipocytes

“…Glucose (25 mM) treatment activated the aldolase reductase pathway and elevated sorbitol and fructose levels in VSMCs and ECs (Berrone et al ., ; Liu et al ., ), but not in 3T3‐L1 adipocytes (Figure ). In addition, insulin did not affect the conversion of fructose from glucose in 3T3‐L1 adipocytes (Figure ), which is consistent with the previous observations in erythrocytes, retina and kidney epithelial cells (Hutton et al ., ; Hotta et al ., ). More importantly, insulin, glucose (25 mM), or their combination suppressed aldolase B expression in adipocytes (Figure ).…”