Red Blood Cell Sorbitol Research Articles

Inhibition of Aldose Reductase and Red Blood Cell Sorbitol Accumulation by Extract of Capparis spinosa

Background: Activation of polyol pathway, due to increased aldose reductase (ALR2) activity, is one of the several mechanisms that have been involved in the development of secondary complications of diabetes. Therefore, ALR2 inhibition has been recognized as a potential therapeutic goal in the prevention and treatment of various secondary complications of diabetes, such as cataract. Objectives: In this study, we aimed to evaluate the inhibitory effects of hydro alcoholic Capparis spinosa extract (CSE) on ALR2 and sorbitol accumulation in red blood cells (RBCs). Materials and Methods: The hydroalcoholic extract of Capparis spinosa (C. spinosa) was prepared and its inhibitory effects were evaluated by using the partial purified bovine lens ALR2 and its specificity was checked by comparing with its inhibitory effect on aldehyde reductase (ALR1), the other member of aldo-keto reductases family. Because RBC sorbitol accumulation is strongly correlated with the blood glucose level, the effect of CSE on sorbitol accumulation in human RBCs, preincubated with high serum glucose concentration, was determined. Results: The CSE inhibited ALR2 activity, with an IC 50 of 0.54 mg/mL and it was seven and a half times greater than that of ALR1 inhibition, indicating the specificity of CSE for ALR2, rather than ALR1. Also, CSE, at a concentration of 0.54 mg/mL, could reduce sorbitol accumulation in erythrocytes, by 46.8%. Conclusions: These results demonstrated that CSE, mainly through inhibition of ALR2, could prevent or delay the diabetic complications, like cataract formation, as a result of sorbitol accumulation.

A Clinical and Neuropathological Study of Chinese Patients with Diabetic Peripheral Neuropathy

ObjectiveTo examine whether the neuropathological and metabolic changes of peripheral nerves are correlated to clinical features in diabetes mellitus type 2 patients with peripheral neuropathy.Methods147 type 2 diabetic patients with signs/symptoms of diabetic peripheralneuropathy (DPN) aged 53.4±12.3 years and 134 healthy volunteers aged 55.5±11.7 years were investigated for fasting plasma glucose (FPG), hemoglobin A1C (HbA1c), and red blood cell sorbitol (RBC sorbitol) in addition to nerve conduction velocity (NCV). Among the 147 diabetic patients, 10 patients underwent superficial peroneal nerve biopsy for light and electron microscopy.ResultsIn the experimental group, the levels of HbA1c and RBC sorbitol showed significant increase compared with the controlled group, whereas motor nerve conduction velocity (MNCV) and sensory nerve conduction velocity (SNCV) both showed decline and SNCV decreased at a greater extent. Morphologically, there were various degrees of nerve fiber loss, associated with axon degeneration and capillary luminal narrowing in 10 patients undergone nerve biopsy.ConclusionThe metabolic change of sorbitol, the consequently observed changes in NCV and histopathology of peripheral nerves are positively correlated with the duration of diabetes and overall level of blood glucose.

Black and Green Teas Equally Inhibit Diabetic Cataracts in a Streptozotocin-Induced Rat Model of Diabetes

Green and black teas were given at 1.25% in the drinking water to streptozotocin-induced diabetic rats for 3 months. Normal and diabetic control groups were also studied. As expected, diabetic animals had significantly increased glucose in lens and plasma. Lens and red blood cell sorbitol were significantly increased as a result of the aldose reductase pathway activation. Plasma and lens lipid thiobarbituric acid-reactive substances and protein glycation were also significantly elevated. Both teas significantly inhibited diabetic cataracts and caused significant reductions in the biochemical pathway implicated in the development of the pathology. After corrections for glucose, it was found that the teas retard the development of diabetic cataracts by a hypoglycemic effect that in turn inhibits the biochemical indicators of pathology. There were significant correlations between glucose, cataract score, and these indicators. Green tea but not black tea caused a significant decline in triglycerides in the diabetic animals. Tea may be a simple, inexpensive means of preventing or retarding human diabetes and the ensuing complications. Tea also should be investigated as an adjunct therapy for diabetes treatment.

A sensitive assay of red blood cell sorbitol level by high performance liquid chromatography: potential for diagnostic evaluation of diabetes

Background The level of sorbitol within erythrocyte or other tissue is increased during diabetic complications such as neuropathy, retinopathy, and nephropathy and is thus considered as an indicator for the diagnosis and monitoring the diabetic status. A highly sensitive method of estimation of RBC sorbitol may be very useful in determining the state of diabetes. In this study a high performance liquid chromatography method was developed to analyze RBC sorbitol level. Method Benzoylation was used for the precolumn derivatization of RBC polyol prior to analyze by HPLC using C-18 reversed phase column and UV detector. Results The sensitivity was 5 ng/ml using standard sorbitol. The linearity was highly satisfactory up to 2.5 μg/ml which was adequate to measure RBC sorbitol in both diabetic and normal subjects. The values were significantly higher for the diabetic patient compared to normal. Within-run assay CVs were <10% and <14% for between-run. Conclusion This method could be useful in estimating RBC sorbitol content for the clinical evaluation of diabetic patients.

Prevention of retinal capillary basement membrane thickening in diabetic dogs by a non-steroidal anti-inflammatory drug.

To investigate the effect of treatment with the non-steroidal anti-inflammatory drug Sulindac on the early vascular pathology of diabetic retinopathy in the dog, and it's effect on recognised biochemical indices of hyperglycaemia-related pathophysiology. Experimental diabetes (streptozotocin/alloxan) was induced in 22 male beagle dogs and 12 of the animals were assigned at random to receive oral Sulindac (10 mg/kg daily). Age- and sex-matched control animals were maintained as non-diabetic controls. After 4 years, several morphological parameters were quantified in the retinal microvasculature of each animal group using an established stereological method. Also, the following diabetes-associated biochemical parameters were analysed: accumulation of advanced glycation end products (AGEs), red blood cell polyol levels and antioxidant status. Diabetes increased red blood cell sorbitol levels when compared to non-diabetic controls (p< or =0.05), however, there was no difference in sorbitol levels between the untreated and the treated diabetic animals. No significant differences were found in red blood cell myoinositol levels between the three groups of animals. Pentosidine and other AGEs were increased two- to three-fold in the diabetic animals (p< or =0.001) although treatment with Sulindac did not affect their accumulation in diabetic skin collagen or alter diabetes-induced rises in plasma malondialdehyde. Retinal capillary basement membrane volume was significantly increased in the untreated diabetic dogs compared to non-diabetic controls or Sulindac-treated diabetic animals (p< or =0.0001). This study has confirmed the beneficial effect of a non-steroidal anti-inflammatory drug on the early vascular pathology of diabetic retinopathy. However the treatment benefit was not dependent on inhibition of polyol pathway activity, advanced glycation, or oxidative stress.

Clinical study of Jinmaitong composita ("Equation missing")on diabetic peripheral neuropathy)on diabetic peripheral neuropathy

Objective: To verify the effect of Jinmaitong composita (JMTC) on red blood cell aldose reductase activity (RBC-AR), red blood cell sorbitol (RBC-S) and nerve conductive velocity in diabetic peripheral neuropathy (DN) patients. Methods: Sixty-six patients with DN were randomly divided into two groups, 33 patients in the treated group treated with JMTC and 33 patients in the control group treated with Jingui Shenqi capsule (JGSQ). RBC-AR, RBC-S and nerve transmission speed were observed before and after three months treatment.Results: Level of RBC-AR, RBC-S apparently decreased and nerve conductive velocity increased (P <0.05,P<0.01) after JMTC treatment.Conclusion: JMTC can improve the nerve conductive velocity significantly with a lowering of RBC-AR and RBC-S and has a good result in treating diabetic peripheral neuropathy.

Does mitochondrial genome mutation in subjects with maternally inherited diabetes and deafness decrease severity of diabetic retinopathy?

Two types of retinopathy, diabetic and pigmentary, may be seen in subjects with maternal inheritance diabetes and deafness. The potential for interactions between the two retinopathies has not been explored. The mitochondrial mutation may affect development of diabetic retinopathy in subjects with MIDD by altering normal pathways of glucose metabolism. We identified five unrelated MIDD kindreds with 61 living maternal line family members. Twenty-three of the family members, 12 with diabetes mellitus and 11 without volunteered to be studied. Subjects were graded for severity of diabetic retinopathy and presence or absence of pigmentary retinopathy after slit lamp biomicroscopy, retinal photography of seven standard fields and fluorescein angiography. Blood was taken, in the fasted state, from MIDD subjects (duration of diabetes 17.0 ± 6.9 yr) and non-diabetic subjects with the mutation, for assay of sorbitol and glucose and values compared with diabetic and non-diabetic control subjects without the mutation. Diabetic retinopathy was absent in 9/12 subjects (75 %), with 3 having mild non-proliferative retinopathy. No one had cataract. Red blood cell sorbitol levels, adjusted for ambient blood glucose, were significantly lower in MIDD subjects compared with diabetic subjects (1.16 ± 0.5 cf. 2.03 ± 1.1, × 10−3 g mmol−1, p = 0.04). Pigmentary retinopathy was present in 15 of 23 subjects, of whom 13 had some abnormality of glucose tolerance. Abnormal glucose tolerance was strongly associated with the development of pigmentary retinopathy (odds ratio 19.5, p = 0.008). In conclusion, there appears to be a decreased prevalence of diabetic retinopathy and cataract in MIDD, which we propose is due to reduced glucose metabolism by the polyol pathway. Abnormal glucose tolerance increases the clinical expression of pigmentary retinopathy in subjects with a mitochondrial genome mutation. A greater understanding of the metabolic effects of mitochondrial DNA mutations has the potential to give insight into the mechanisms of diabetic retinopathy and other complications of diabetes mellitus. © 1998 John Wiley & Sons, Ltd.

Does mitochondrial genome mutation in subjects with maternally inherited diabetes and deafness decrease severity of diabetic retinopathy?

Two types of retinopathy, diabetic and pigmentary, may be seen in subjects with maternal inheritance diabetes and deafness. The potential for interactions between the two retinopathies has not been explored. The mitochondrial mutation may affect development of diabetic retinopathy in subjects with MIDD by altering normal pathways of glucose metabolism. We identified five unrelated MIDD kindreds with 61 living maternal line family members. Twenty-three of the family members, 12 with diabetes mellitus and 11 without volunteered to be studied. Subjects were graded for severity of diabetic retinopathy and presence or absence of pigmentary retinopathy after slit lamp biomicroscopy, retinal photography of seven standard fields and fluorescein angiography. Blood was taken, in the fasted state, from MIDD subjects (duration of diabetes 17.0+/-6.9 yr) and non-diabetic subjects with the mutation, for assay of sorbitol and glucose and values compared with diabetic and non-diabetic control subjects without the mutation. Diabetic retinopathy was absent in 9/12 subjects (75%), with 3 having mild non-proliferative retinopathy. No one had cataract. Red blood cell sorbitol levels, adjusted for ambient blood glucose, were significantly lower in MIDD subjects compared with diabetic subjects (1.16+/-0.5 cf. 2.03+/-1.1, x 10(-3) g mmol(-1), p=0.04). Pigmentary retinopathy was present in 15 of 23 subjects, of whom 13 had some abnormality of glucose tolerance. Abnormal glucose tolerance was strongly associated with the development of pigmentary retinopathy (odds ratio 19.5, p=0.008). In conclusion, there appears to be a decreased prevalence of diabetic retinopathy and cataract in MIDD, which we propose is due to reduced glucose metabolism by the polyol pathway. Abnormal glucose tolerance increases the clinical expression of pigmentary retinopathy in subjects with a mitochondrial genome mutation. A greater understanding of the metabolic effects of mitochondrial DNA mutations has the potential to give insight into the mechanisms of diabetic retinopathy and other complications of diabetes mellitus.

Relationship between glutathione and sorbitol concentrations in erythrocytes from diabetic patients

Red blood cell (RBC) concentrations of sorbitol and reduced glutathione (GSH) were evaluated in 29 type II diabetic subjects and eight normal controls. In erythrocytes from diabetic subjects, sorbitol levels were higher (18.7 ± 1.33 v 11.2 ± 0.7 nmol/g hemoglobin [Hb], P < .001) and GSH levels were lower (5.48 ± 0.19 v 8.33 ± 0.24 μmol/g Hb, P < .01) than in nondiabetics. RBC sorbitol levels were positively correlated with fasting blood glucose ( r = .57, P < .001) but not with HbA 1c ( r = .16, P = NS). RBC GSH levels showed a negative correlation with fasting blood glucose ( r = −.35, P < .05) and with HbA 1c ( r = −.34, P < .05) and a significant negative correlation with RBC sorbitol levels ( r = −.62, P < .001). Stepwise regression analysis highlighted the fact that the hyperglycemia-dependent increase in RBC sorbitol was significantly influenced by GSH concentrations (partial F = 14.6, P < .001). These data suggest the hypothesis that the hyperglycemia-induced enhanced activity of the polyol pathway leads to GSH depletion and, in turn, GSH depletion, reducing the glycolytic flux to pyruvate, enhances the rate of glucose metabolism through the polyol pathway. The overall effect is a progressive worsening of metabolic pseudohypoxia and depletion of GSH, resulting in lower defense against oxidative stress.

Tolrestat pharmacokinetic and pharmacodynamic effects on red blood cell sorbitol levels in normal volunteers and in patients with insulin-dependent diabetes*

To examine the effect of diabetes mellitus on the pharmacokinetics of tolrestat and to investigate its effect on red blood cell sorbitol levels according to a new pharmacodynamic model for this class of drugs. Single and multiple doses of tolrestat (200 mg/twice a day) were administered to 12 patients with insulin-dependent (type I) diabetes and 12 healthy volunteers in an open parallel trial. Tolrestat disposition was characterized by first-order absorption and biexponential disposition: In normal subjects the terminal disposition half-life (t1/2) was 13 +/- 3 hours (mean +/- SD) and the apparent oral clearance (CL/F) was 48 +/- 9 ml/hr/kg, similar to the values in patients with type I diabetes mellitus (t1/2 = 14 +/- 4 hours; CL/F = 55 +/- 10 ml/hr/kg). Red blood cell sorbitol concentrations, which declined because of tolrestat's inhibition of aldose reductase, were characterized by an indirect-response model including a 50% inhibition constant (IC50) for production of sorbitol by aldose reductase. The removal of sorbitol (kout) was slower in patients with diabetes. The plasma IC50 averaged 2.0 +/- 1.3 micrograms/ml in normal subjects and 2.5 +/- 1.9 micrograms/ml in patients with diabetes. IC50 values expressed in free (unbound) concentrations (fu = 0.64%), which ranged from 12 to 16 ng/ml, were similar to the in vitro IC50 for inhibition of sorbitol accumulation in human red blood cells. Tolrestat pharmacokinetics were similar in normal subjects and in patients with diabetes; however, the patients with diabetes had higher baseline sorbitol levels (11 versus 5 nmol/ml for normal subjects) and slower sorbitol efflux rates. The proposed biochemically realistic, dynamic model characterized well the red blood cell sorbitol response patterns after administration of single and multiple doses of tolrestat.

Aldose reductase inhibition restores endothelial cell function in diabetic rabbit aorta.

A possible relationship between increased aldose reductase activity and abnormal endothelium-dependent relaxation was examined in aorta from alloxan-induced diabetic rabbits. Isolated aorta of diabetic rabbits, contracted submaximally with phenylephrine, showed significantly decreased endothelium-dependent relaxations induced by acetylcholine or adenosine diphosphate compared to those from normal rabbits. Basal and acetylcholine-stimulated levels of cyclic GMP and the relaxations in response to an endothelium-independent vasodilator, sodium nitroprusside, were not significantly different between diabetic and normal rabbits, indicating that nitric oxide release and action on the vascular smooth muscle were unchanged. The release of thromboxane A2 from diabetic vessels was increased, as previously demonstrated. Treatment with an aldose reductase inhibitor, zopolrestat, normalized the elevated red blood cell sorbitol levels in diabetic rabbits. Zopolrestat also restored the abnormal acetylcholine- and adenosine diphosphate-induced relaxations of the aorta. The aldose reductase inhibitor had no effect on the levels of cyclic GMP or on the increased release of thromboxane A2 in diabetic aorta. These findings suggest that increased activity of the aldose reductase pathway in hyperglycemia is responsible for the abnormal endothelium-dependent relaxation in diabetic blood vessels. Significant alterations in endothelial production of neither nitric oxide nor vasoconstrictor prostanoids could be directly implicated in the improvement caused by the drug, suggesting another mechanism of action.

Reduction of Red Blood Cell Sorbitol by Ascorbic Acid in Diabetic Patients

Reduction of Red Blood Cell Sorbitol by Ascorbic Acid in Diabetic Patients

Effect of a New Aldose Reductase Inhibitor, Ponalrestat, on Reduction of Red Blood Cell Sorbitol Level in Diabetics

Effect of a New Aldose Reductase Inhibitor, Ponalrestat, on Reduction of Red Blood Cell Sorbitol Level in Diabetics

Red Blood Cell Sorbitol Lowering Effects and Tolerance of Single Doses of AL 1576 (HOE 843) in Diabetic Patients

The safety and biochemical effects of AL 1576 (HOE 483), a recently developed aldose reductase inhibitor, were evaluated. In a double-blind, placebo-controlled, clinical trial, AL 1576 (HOE 483) was administered to diabetic patients for the first time. Four single, orally administered dose levels were tested, (2, 5, 10, and 20 mg). No clinically important adverse effects were seen in any of the patients. AL 1576 (HOE 483) suppressed red blood cell (RBC) sorbitol concentrations in a dose-related fashion. Also found were statistically significant inverse correlations between the plasma drug concentration and both RBC sorbitol concentrations as well as RBC sorbitol/serum glucose ratios. In single doses up to 20 mg, AL 1576 (HOE 483) is well tolerated and decreases RBC sorbitol, a biochemical marker of pharmacologic activity, in diabetic patients.

Screening for red blood cell sorbitol dehydrogenase deficiency in patients with diabetes or cataracts.

Quantitative screening for red blood cell sorbitol dehydrogenase (RBC-SORD) deficiency in 111 patients with juvenile onset diabetes, 92 patients with adult onset diabetes, 42 patients with idiopathic cataracts and 192 professional blood donors was performed. A wide variability in RBC-SORD activity in controls and patients was observed. No significant differences in SORD activity either between patients with diabetes and patients with idiopathic cataracts or between diabetics with and without cataracts were observed. Whether or not there were carriers for either amorphous or hypomorphous alleles of the SORD locus in the population studied could not be defined in terms of enzymatic activity levels.

Applicability of red blood cell sorbitol measurements to monitor the clinical activity of sorbinil

Increased flux of glucose through the polyol pathway with resultant accumulation of tissue sorbitol is implicated in the pathogenesis of the chronic complications of diabetes. Sorbinil is a potent inhibitor of aldose reductase (the first enzyme in the polyol pathway) and has been shown to normalize sorbitol levels in relevant tissues (eg, nerve, kidney, lens) of experimentally-induced diabetic animals. The purpose of this study was to identify a relatively noninvasive method of monitoring the intrinsic (or biochemical) efficacy of sorbinil in diabetic man. Specifically, the objective was to identify a readily accessible tissue that would be reflective of polyol pathway activity and the activity of sorbinil in clinically relevant but less accessible tissues. Based on several previous studies, 1–3 which demonstrated that sorbitol accumulation in human red blood cells (RBCs) was a function of ambient glucose concentrations, either in vitro or in vivo, our investigations were conducted to determine if (1) RBC sorbitol accumulation would correlate with sorbitol accumulation in lens and nerve tissue of diabetic rats; (2) the effect of sorbinil in reducing sorbitol levels in lens and nerve tissue of diabetic rats would be reflected by changes in RBC sorbitol; and (3) sorbinil would reduce RBC sorbitol in diabetic man. 4

Effect of tolrestat on red blood cell sorbitol levels in patients with diabetes

The effect of the aldose reductase inhibitor, tolrestat, on red blood cell (RBC) sorbitol levels was studied in 23 patients with diabetes after oral dosing with tolrestat, 25 or 100 mg b.i.d. The mean (+/- SE) RBC sorbitol levels (measured 12 hours after the preceding dose) after 3, 7, and 13 days of dosing decreased after both dose levels. After 25 mg tolrestat the RBC sorbitol levels fell from 25.1 +/- 4.0 to 20.0 +/- 5.7 nmol/gm hemoglobin (21%) and after 100 mg tolrestat the level fell from 26.7 +/- 3.7 to 11.4 +/- 1.7 nmol/gm hemoglobin (57%; P less than 0.001). This latter RBC sorbitol concentration is similar to levels in individuals without diabetes. At both dosage levels the maximum decrease in RBC sorbitol levels occurred after only 3 days of dosing. Tolrestat had no effect on plasma glucose or hemoglobin A1 concentrations. The overall mean plasma unbound drug concentration measured 12 hours after 100 mg tolrestat (11.7 +/- 3.0 ng/ml; 3.3 X 10(-8) mol/L) was similar to the median inhibitory level (3 X 10(-8) mol/L) of tolrestat for sorbitol accumulation in human RBCs incubated in a high-glucose medium. Our results demonstrate the systemic bioavailability of tolrestat and its aldose reductase inhibitory activity in erythrocytes of patients with diabetes.

Red blood cell sorbitol (RBC-SOR) in non-diabetic patients treated with TPN : [formula omitted], E. Rillaerts, J. Vertommen, M. Vandewoude (Laboratory of Endocrinology and Nutrition, University of Antwerp (UIA), Belgium)

Red blood cell sorbitol (RBC-SOR) in non-diabetic patients treated with TPN : [formula omitted], E. Rillaerts, J. Vertommen, M. Vandewoude (Laboratory of Endocrinology and Nutrition, University of Antwerp (UIA), Belgium)

Sorbitol dehydrogenase deficiency in several pig tissues: potential implications for studies of experimental diabetes

Screening for red blood cell sorbitol dehydrogenase deficiency in 12 different mammalian species was performed. A wide inter-species variability in red cell sorbitol dehydrogenase with a virtually complete deficiency in pigs was observed. Aldose reductase and sorbitol dehydrogenase activities in 12 different pig tissues also were measured. Aldose reductase activity was present in all the tissues studied, whereas organ specificity for sorbitol dehydrogenase was observed. Sorbitol dehydrogenase activity was not detectable in lenses, among other tissues, making the pig a potential model for studies in experimental diabetes, particularly for the investigation of sorbitol dehydrogenase deficiency as a risk factor in the development of cataracts.

Red blood cell sorbitol as an indicator of polyol pathway activity. Inhibition by sorbinil in insulin-dependent diabetic subjects

Red blood cell sorbitol as an indicator of polyol pathway activity. Inhibition by sorbinil in insulin-dependent diabetic subjects