Correlation between erythrocyte aldose reductase activity and the width of skeletal-muscle capillary basement membrane in insulin-dependent diabetes mellitus

Thickening of capillary basement membrane has been demonstrated in diabetic subjects, and it is considered to be the characteristic pathological lesion of diabetic microvascular disease. There are studies reporting the effects of inhibitors of aldose reductase, the first enzyme of the polyol pathway, on the thickening of the capillary basement membrane. These observations indicate a significant role of the polyol pathway in the development of microvascular disease. However, it is unknown whether or not there is any correlation between the thickness of the capillary basement membrane and the activity of aldose reductase in diabetic patients. To clarify this issue, we measured the width of skeletal-muscle basement membrane and erythrocyte aldose reductase activity in 27 insulin-dependent diabetic and 8 nondiabetic individuals. The results showed that both the aldose reductase activity and the width of capillary basement membrane were increased in diabetic patients as compared to nondiabetic individuals (6.89 ± 0.38 versus 5.15 ± 0.60 mL/mU erythrocytes, p < 0.05 and 2257 ± 166 versus 1136 ± 69 Å, p < 0.0001, respectively) (means ± SE), but marked variability was observed in both the enzyme activity and the basement membrane thickness among the diabetic patients. There was a significant correlation between the capillary basement membrane thickness and the activity of erythrocyte aldose reductase (r = 0.51, p < 0.01) in diabetic patients. Our data suggest that the polyol pathway plays an important role in thickening of capillary basement membrane in diabetic individuals, and the variability in aldose reductase activity seen among diabetic patients may result in the varying susceptibility to the development of diabetic microvascular disease.     

Improved diabetes control reduces skeletal muscle capillary basement membrane width in insulin-dependent diabetes mellitus

We studied the relationship between the control of blood glucose and the width of skeletal muscle capillary basement membrane in 54 insulin-dependent diabetic patients. After initial measurement of levels of glycosylated hemoglobin and the width of skeletal muscle capillary basement membrane, the patients were divided into two groups: an intensive treatment group of 30 patients who were treated with continuous subcutaneous insulin infusion and a control group of 24 patients who continued to receive conventional treatment, usually two daily injections of insulin. Both groups have been followed prospectively for periods of time up to 4 years. Within 1 year the intensive treatment group had a significant decrease in glycosylated hemoglobin levels as compared to baseline values reflecting improved control of blood glucose. This level of glycosylated hemoglobin was stable over the remainder of the follow-up period. This group also had a significant reduction in the width of skeletal muscle capillary basement membrane within 1 year and it persisted for the 4 years of observation. The control group of patients had no significant change in their level of glycosylated hemoglobin and the width of the skeletal muscle capillary basement membrane tended to increase with time. It this result in skeletal muscle capillaries applies to those of retinal and renal tissue, meticulous diabetic control for a prolonged period of time may be beneficial in preventing the progression of the microvascular complications of diabetes mellitus.     

Muscle capillary basement membrane in juvenile diabetes mellitus

Calculations of the minimum rather than the average basement membrane thickness of muscle capillaries established that widening of this structure was only rarely encountered in juvenile-onset diabetes of 1–6 yr duration. The basement membrane was usually, but not always, thickened, however, in childhood-onset diabetes present for 7 or more yr. The presence or absence of basement membrane thickening did not appear to be related to age at onset of diabetes, the degree of hyperglycemia in an oral glucose tolerance test, any residual ability to secrete insulin, the type, dosage or schedule of insulin therapy, history of ketoacidosis and shocking, blood pressure, or the state of the kidneys. However, each of the patients with an increase in the width of the basement membrane of muscle capillaries did have microaneurysms. Our data are consonant with the hypothesis that thickening of the basement membrane generally appears toward the end of the first decade following the diagnosis. Since duration and age tend to be related, such thickening was more common in the older persons with juvenile-onset diabetes. Also, in such patients serum creatinine tended to be higher and proteinuria was more frequent, two variables known to be influenced by duration of diabetes and increased chronologic age.     

The effect of an aldose reductase inhibitor on cardiovascular performance in patients with diabetes mellitus

Because some aldose reductase inhibitor studies have demonstrated clinical improvement in scored neurological signs and symptoms of diabetic neuropathy, a prospective study of the effect on cardiovascular performance of sorbinil 250 mg/day for 12 months was conducted on patients with diabetic autonomic neuropathy who were free of atherosclerotic coronary artery disease and/or cardiomyopathy. After 1 year of treatment, the study group (n = 14) demonstrated significant improvement in both the resting cardiac output (P = 0.02), and the maximal cardiac output (P = 0.03). This observation suggests that the use of an aldose reductase inhibitor may be useful in treating suboptimal cardiovascular performance in patients with diabetic cardiac autonomic neuropathy.     

Muscle magnesium and capillary basement membrane thickness in diabetes mellitus

To evaluate a possible relationship between Mg deficiency and the development of microvascular disease in diabetes mellitus, quadriceps muscle biopsies for estimating Mg content and capillary basement membrane thickness, were studied in 16 patients with type I diabetes. The diabetic individuals had a slightly but significantly reduced muscle Mg content as compared with 13 healthy controls. There was a significant, positive correlation between capillary basement membrane width and age in the diabetic group, but no relationship between membrane thickness and muscle or serum concentration of Mg. However, diabetic patients with retinopathy (n = 6) showed a nonsignificant inverse correlation between basement membrane thickness and Mg parameters. The opposite tendency was found in patients without retinal lesions.     

The effect of the aldose reductase inhibitor, ponalrestat, on the progression of diabetic retinopathy.

The objective of this study was to evaluate the effects of ponalrestat, an aldose reductase inhibitor, on the progression of diabetic retinopathy. In this study, 62 patients with diabetes mellitus underwent a double-masked placebo-controlled clinical trial comparing the effect of ponalrestat 600 mg per day with a placebo on the progression of diabetic retinopathy. Both groups were comparable in terms of age, gender distribution, diabetes duration, metabolic control, and presence and severity of diabetic retinopathy. Seven-field stereo fundus photographs were performed at 0 (baseline), 12, and 18 months; 49 patients completed the study (26 in the ponalrestat group and 23 in the placebo group). In both treatment groups, a significant progression of diabetic retinopathy as evaluated by the Early Treatment Diabetic Retinopathy Study classification was observed (Wilcoxon Rank-Sum Test, p less than 0.05). No difference was observed in the progression of retinopathy between the two treatment groups (p = 0.96). The number of microaneurysms increased in the two study groups (from 5.6 +/- 1.2 to 10.5 +/- 1.3 in the placebo group and from 10.3 +/- 1.4 to 12.7 +/- 1.4 in the ponalrestat group); however, the increase was statistically significant only in the placebo group (p less than 0.05). When the increase in the number of microaneurysms was evaluated by change of category of microaneurysm count, no significant difference was observed. We conclude that ponalrestat at a dose of 600 mg per day has no clinically significant effect on the progression of diabetic retinopathy.     

Effect of the aldose reductase inhibitor, ponalrestat, on diabetic neuropathy

The effect of treatment with the aldose reductase inhibitor, Ponalrestat*, was studied in 30 diabetic patients with established peripheral and autonomic neuropathy. After a 4-week placebo run-in phase, patients were randomised to 16 weeks active or placebo treatment in a double-blind, parallel-group trial. Changes in neuropathy were assessed using vibration perception thresholds, heart rate responses to deep breathing, pulse and blood pressure changes on standing and the patients' subjective scoring of peripheral and autonomic neuropathic symptoms. In addition, circulating neuropeptides and the responses of circulating gut peptides to an oral glucose tolerance test were studied. There was a significant improvement in the mean vibration perception threshold over the four sites studied in the ponalrestat treated group. There were no significant changes in the other indices of neuropathy, including heart rate variability, blood pressure responses to standing or symptom scores, though there were trends towards improvement. There were no significant changes in the levels of the circulating neuropeptides or in the responses of the circulating gut peptides to oral glucose tolerance test. No clinically important side-effects attributable to ponalrestat were observed. We conclude that ponalrestat improves some of the parameters of diabetic neuropathy and is likely to be of value in the treatment of this condition.     

One-year treatment with the aldose reductase inhibitor, ponalrestat, in diabetic neuropathy.

A double blind placebo controlled trial was performed to evaluate the effects of the aldose reductase inhibitor, ponalrestat, on symptomatic diabetic neuropathy. After a 4-week placebo run-in phase, 60 patients were 2:1 randomized to receive either 600 mg ponalrestat or placebo once daily over 12 months. Forty-six patients, 30 of whom were treated with ponalrestat and 16 with placebo, completed the study. Motor and sensory nerve conduction, thermal and vibration sensation thresholds, heart rate variation at rest, E/I ratio, pupillary dilation velocity and pupillary reflex latency were determined at baseline and after 6 and 12 months. Neuropathic symptom scores were assessed every 3 months. Among the fifteen nerve function parameters studied, only trends in favour of ponalrestat were noted for heart rate variation and E/I ratio after 6 months (P = 0.06), but no significant differences between the groups could be demonstrated during the study. No adverse reactions were observed. It is concluded that one-year treatment with ponalrestat has no beneficial effects on symptoms or electrophysiological parameters in diabetic neuropathy.     

The effect of aldose reductase inhibitors on glomerular prostaglandin production and urinary albumin excretion in experimental diabetes mellitus

Summary The effect of two structurally unrelated aldose reductase inhibitors, sorbinil and ponalrestat, on glomerular prostaglandin production and urinary albumin excretion was investigated in rats with diabetes induced by streptozotocin. It was found that both aldose reductase inhibitors, when administered from the time of induction of the diabetes, significantly decreased the raised urinary albumin excretion in the diabetic rats, although it remained elevated compared with non-diabetic rats. Glomerular prostaglandin E and 6-ketoprostaglandin F₁ production was significantly increased in glomeruli obtained from the diabetic rats. Inhibition of aldose reductase caused a reduction in the raised glomerular prostaglandin production, although this remained above that observed in the non-diabetic rats. Subsequent experiments were performed to determine whether the effects of the aldose reductase inhibitors could be explained by effects on glomerular filtration rate. It was found that ponalrestat, at a dose which markedly reduced urinary albumin excretion, did not significantly affect glomerular filtration rate in non-diabetic rats, rats with untreated streptozotocin-induced diabetes and rats with diabetes partially treated with low dose insulin. Glomerular sorbitol concentrations were significantly elevated in untreated diabetic rats as early as two weeks after the induction of diabetes. It is concluded that the administration of aldose reductase inhibitors from the time of induction of diabetes significantly reduces glomerular prostaglandin production and urinary albumin excretion. The latter effect is not due to an effect on glomerular filtration rate. Increased polyol pathway activity may account in part for the increased glomerular prostaglandin production and urinary albumin excretion in early experimental diabetes.     

醛糖还原酶基因5’端(AC)n多态性对2型糖尿病患者红细胞醛糖还原酶活性的影响

目的　探讨醛糖还原酶 (AR)基因 5’端 (AC) n 的多态性对 2型糖尿病 (DM )红细胞AR活性的影响。方法　 16 3例 2型DM分为无微血管病变 (NDC)组 (6 6例 )和微血管病变 (DMAP)组(97例 ) ,正常对照 (CON)组 42例 ;另按AR基因 5’端 (AC) n 的等位基因类型分为DM携带Z 2等位基因 (DZ 2 )组 (5 4例 )、DM携带Z - 2等位基因 (DZ - 2 )组 (35例 )、DM同时携带Z 2和Z - 2等位基因 (Z 2 /Z - 2 )组 (18例 )、DM不携带Z 2和Z - 2等位基因 (X/X)组 (5 6例 )、对照者携带Z 2等位基因 (NZ 2 )组 (2 1例 )和对照者携带Z - 2等位基因 (NZ - 2 )组 (7例 )。用改良Sriratava法测定AR活性并比较其在各组间的差异。结果　DMAP组、NDC组和CON组间的AR活性 (ARA)差异有显著性 ,DMAP组最高 ,NDC组次之 ,CON组最低 (P <0 .0 0 1)。DM组携带Z - 2和Z 2等位基因各亚组中 ,DZ - 2组ARA最高 ,Z - 2 /Z 2和X/X组居中 ,DZ 2组最低 ,差异有显著性统计学意义(P <0 .0 0 1)。DZ - 2和NZ - 2组的ARA分别高于DZ 2和NZ 2组 ,DZ - 2和DZ 2组的ARA分别高于NZ - 2和NZ 2组 (P均 <0 .0 0 1)。结论　AR的激活对DMAP的发生和发展起重要作用。Z - 2等位基因可能是AR的激活因子 ,Z 2等位基因则为其抑制因子。     

Glomerular basement membrane thickening in streptozotocin diabetic rats despite treatment with an aldose reductase inhibitor

This study concerns the possible prevention of glomerular basement membrane thickening in experimental diabetes by an aldose reductase inhibitor (ARI), Statil^®. ARI added to the chow was given to streptozotocin diabetic rats over a period of 6 months. Reference groups were control rats and diabetic rats on the same chow without ARI. The diabetic rats were given insulin two or three times a week, and blood glucose was measured monthly before insulin injections. There was a marked difference in the occurrence of cataracts between the two diabetic groups. ARI treated rats tended to have lower blood glucose than the diabetic reference group, but the difference was not significant. At the termination of the experiment, the left kidney was perfusion fixed, weighed, and prepared for light and electron microscopy. Systematic random sampling from the entire kidney was performed to obtain light microscopic visual fields and ultrathin sections from two glomeruli. Mean glomerular volume was estimated by light microscopy, and glomerular basement membrane thickness, by electron microscopy. Basement membrane thickness was significantly increased in untreated diabetic rats (174 nm, SD = 4.5 nm) as compared to that of controls (Mean: 154 nm, SD = 11.0 nm), and was even more so in ARI treated rats (187 nm, SD = 18.7 nm,) although the ARI treated rats showed less renal and glomerular hypertrophy than did untreated diabetic rats. In conclusion, the ARI treatment over an experimental period of 6 months attenuated diabetic renal and glomerular hypertrophy, but had no effect at all on diabetic glomerular basement membrane thickening.     

Sulfonylurea-induced decrease of muscle capillary basement membrane thickness in diabetes

Three muscle biopsies were performed in 53 overt type 2 diabetics over a period of approximately 2 years. At baseline, 21 (40%) had an increased capillary basement membrane width in muscle. Thirty-five patients received glipizide and 18 received placebo. In the patients receiving placebo, the mean of the muscle capillary basement membrane width increased from 158.7 +/- 11.5 nm (SEM) to 170.9 +/- 14.7 nm (P = NS), but in those receiving glipizide the value decreased from 192.9 +/- 13.2 nm to 161.0 +/- 10.2 nm (P = 0.02). Plasma glucose and glycosylated hemoglobin A1 decreased significantly (P less than 0.001) after 2 years in patients receiving glipizide. In 15, mean glycosylated hemoglobin A1 reached a normal range, and mean basement membrane width decreased to a level close to that found in subjects without diabetes (P = NS). These findings are consistent with the hypothesis that effective response to oral medication can decrease the basement membrane thickening, suggesting that diabetic microangiopathy is not necessarily progressive.     

The preventive effect of aldose reductase inhibition on diabetic optic neuropathy in the BB/W-rat

Summary A polyol-pathway-related mechanism has been invoked in the pathogenesis of murine and human diabetic peripheral neuropathy in which progressive axonal atrophy and axo-glial dysjunction constitute the cardinal structural abnormalities. We have previously reported similar neuroanatomical changes in the optic nerve of 6-month diabetic BB/W-rats. In the present study we demonstrate progression of axonal atrophy and axo-glial dysjunction in the optic nerve in 12-month diabetic BB/W-rats. These structural lesions showed highly significant correlations with the associated prolongation of the latencies of the visual evoked potentials, suggesting that axo-glial dysjunction and axonal atrophy are major determinants for impaired optic nerve function. As in peripheral nerve, the polyol-pathway is present in the optic nerve and is activated by hyperglycaemia and galactosaemia. In this study we further examined the treatment effect of the aldose reductase inhibitor ponalrestat, given from 3 weeks of diabetes and continued throughout the study protocol. This regimen resulted in complete prevention of axo-glial dysjunction, and had a significant ameliorating effect on visual evoked potential latencies, but had no effect on optic nerve axonal atrophy. This latter finding differs from the effect of aldose reductase inhibition on diabetic peripheral nerve and suggests that axonal atrophy of central nerve tracts in diabetes may be the consequence of other metabolic abnormalities or alternatively the present regimen was insufficient to protect central axons from the effects of an increased activity of the polyol pathway.     

The effect of aldose reductase inhibition on erythrocyte polyols and galactitol accumulation in diabetic patients

Erythrocyte sorbitol level has previously been used as a measure of the efficacy of aldose reductase inhibitors, but its value is limited by fluctuations related to variations in blood glucose concentration. The aim of the study was to compare sorbitol content with the ability to accumulate galactitol during ex vivo incubation with galactose, of erythrocytes taken from diabetic patients following administration of a single 600 mg dose of the aldose reductase inhibitor, ponalrestat. Twelve patients were studied in a placebo-controlled crossover trial. Blood glucose levels were not statistically different during the placebo and ponalrestat treatment periods except at 1 h after the dose was taken (10.6 +/- 6.7 vs 7.7 +/- 4.6 mmol l-1 (+/- SD), p less than 0.05). Ponalrestat reduced erythrocyte sorbitol concentrations compared with placebo at 3, 5 and 7 h (0.82 +/- 0.36, 0.69 +/- 0.23, and 0.83 +/- 0.35 mg l-1 vs 1.79 +/- 0.67, 1.68 +/- 0.65, and 1.57 +/- 0.59 mg l-1 respectively, p less than 0.005) and 24 h post-dose (1.57 + 0.45 vs 2.01 + 0.73 mg l-1, p less than 0.05). Ponalrestat also reduced erythrocyte galactitol accumulation at 3, 5 and 24 h post-dose from 5.53 +/- 2.41, 5.43 +/- 1.89, and 5.42 +/- 1.96 mg l-1 2-h-1 to 1.47 +/- 0.30, 1.76 +/- 0.41, and 4.12 +/- 0.72 mg l-1 2-h-1 respectively, p less than 0.01. Galactitol accumulation rate appeared to be a less variable parameter than erythrocyte sorbitol and was not influenced by fluctuations in blood glucose.(ABSTRACT TRUNCATED AT 250 WORDS)     

A 12-month randomized controlled study of the aldose reductase inhibitor ponalrestat in patients with chronic symptomatic diabetic neuropathy.

The effects of the aldose reductase inhibitor ponalrestat (600 mg day-1) on sensory, electrophysiological, and autonomic function were examined in 50 patients with chronic symptomatic, distal symmetrical diabetic neuropathy in a 52-week randomized, double-blind, parallel-group, placebo-controlled, single-centre study. In an endeavour to identify patients with a degree of neuropathy potentially amenable to pharmacological intervention, a minimum conduction velocity of 30 m s-1 was set for the peroneal motor nerve. At 52 weeks, no significant differences were observed between the ponalrestat and placebo groups in motor (ulnar, median, and peroneal) or sensory (ulnar and radial) nerve conduction velocities, vibration perception thresholds, adjectival symptom scores or tests of autonomic function (mean electrocardiographic R-R interval variability on deep breathing and orthostatic blood pressure response). Ponalrestat was clinically well tolerated and had no significant effect on glycaemic control. The lack of beneficial effects of ponalrestat may in part reflect the advanced stage of the neuropathic process in patients with established symptomatic disease, and the poor reproducibility of current neurophysiological techniques. Firmer knowledge of clinico-pathological correlates allied to improved non-invasive neurophysiological measurement techniques should facilitate the selection of patients for future therapeutic trials in diabetic neuropathy.     

Myo-inositol and sorbitol metabolism in relation to peripheral nerve function in experimental diabetes in the rat: The effect of aldose reductase inhibition

A possible relationship between increased sorbitol concentration and decreased myo-inositol concentration in peripheral nerves of diabetic rats has been examined. To this end, sorbinil, an aldose reductase inhibitor, was used either to prevent or reverse elevation of nerve sorbitol concentration in diabetic rats. Sorbinil treatment at 20 mg . kg-1 . day-1 prevented elevation of nerve sorbitol levels in early diabetes and reduced sorbitol concentration from 2.38 to 0.51 mumol/g in rats diabetic for 10 weeks. This treatment reduced the increase in nerve fructose concentration and prevented the reduced myo-inositol concentration found in diabetic rat nerve (control 3.63, diabetic 2.40, diabetic/sorbinil, 3.56 mumol/g). Sorbinil treatment did not prevent a significant slowing of motor-nerve conduction velocity at 10 weeks although treatment reduced the extent of slowing. Sorbinil treatment at 25 mg . kg-1 . day-1 reduced elevated sorbitol and fructose concentrations in diabetic in diabetic rat nerve and normalised myo-inositol concentration. Myo-Inositol treatment at 650 mg . kg-1 . day-1 did not affect the elevated concentrations of sorbitol, fructose or glucose in peripheral nerves of diabetic rats, but it did restore reduced myo-inositol concentration. Both sorbinil and myo-inositol treatment partially reversed the slowing of motor-nerve conduction velocity in diabetic rats. These results are discussed in relation to the involvement of sorbitol and myo-inositol metabolism in the aetiology of diabetic neuropathy.     

Relationship between nailfold capillary microscopy and salivary capillary basement membrane width in Raynaud's disease and progressive systemic sclerosis

To assess the relationship between a nailfold scleroderma pattern and histopathological data, we compared the results of nailfold capillaroscopy with capillary basement membrane width of labial salivary glands in 25 patients with either a Raynaud's disease (RD: 12 patients) or a progressive systemic sclerosis (PSS: 13 patients). The sensitivity of a capillaroscopic scleroderma pattern for capillary basement membrane thickness is of 75%. These results confirm the usefulness of in vivo capillary examination for the early diagnosis of PSS.     

Prevention of glomerular basement membrane thickening by aminoguanidine in experimental diabetes mellitus

The etiology of diabetic glomerulopathy appears to be related, at least in part, to the degree of hyperglycemia, the resultant nonenzymatic glycosylation of proteins, and the eventual formation of advanced glycosylation end products in long-lived structural proteins. To investigate the relationship between the glomerular basement membrane (GBM) changes of diabetic nephropathy and the formation of advanced glycosylation end products, we studied control rats, diabetic rats, and control and diabetic rats who received aminoguanidine, a compound that pharmacologically inhibits formation of advanced glycosylation end products. After 9 months, rat weight was smaller and kidney weight larger in both diabetic groups compared with both control groups. GBM width was increased in the diabetic group compared with the control group. Aminoguanidine administration to diabetic rats ameliorated this increase in GBM. Thus, aminoguanidine administration from the onset of experimental diabetes prevented the widening of the GBM that is typical of diabetes.