Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retrospective studies on cataract development in patients with rheumatoid arthritis or osteoarthritis revealed a retardant effect of aspirin on diabetic and non-diabetic cataracts. The effect of aspirin is dose-dependent. The correlation coefficient between years delay for various cataracts subcategories versus aspirin taken (in tablets per day X years of intake) was 0.69. The ocular pharmacokinetics of 14C acetylsalicylic acid or salicylate were determined after intravenous or intraperitoneal administration to rabbits. 14C acetylsalicylic acid penetrates rapidly into rabbit lens and aqueous humor after intravenous administration. After intraperitoneal administration, salicylate levels in rabbit plasma, similar to those of humans receiving four to six aspirin tablets (325 mg each), result in accumulation of salicylate by lens (mean +/- SD) of 405 +/- 72 mumoles/g and 620 +/- 30 mumoles/g at two and four hours, respectively. At those dosages, salicylate is cleared in 24 hours from rabbit plasma and intraocular fluids, but retained by lens. Penetration of salicylate into rabbit lens and rat lens is dose-dependent. The retardant aspirin effect in diabetic cataracts is linked to inhibition of tissue aldose reductase and lens protein glycosylation. Deceleration of galactose cataract formation in rats occurs after daily salicylate intraperitoneal injections of 100 mg/kg a day.
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PMID:Distribution of salicylate in lens and intraocular fluids and its effect on cataract formation. 685 71

Loss of transparency in the human lens can be documented by a variety of methods including: (a) slit lamp photography with or without corrections for depth of focus; (b) retroillumination photography alone or coupled to densitometry; (c) high resolution targets projected into the eye and visualized by an ophthalmoscope; (d) drawings and/or measurements of lens opacities; (e) visual acuity determinations after visualization of the macular area and complete eye examination. The advantages and practical uses of each method were reviewed with reference to its value in determining the progression of cataracts in humans. Diabetes accelerates cataract development as determined from graphic plots of cataracts classified after surgical extraction vs the patient's age. Using similar methods high aspirin dosages administered through many years were found to decelerate cataract progression. Drugs for preventing development of diabetic cataracts in animals include inhibitors of aldose reductase or glycosylation such as sulindac (Clinoril), sorbinil or aspirin.
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PMID:Methods for evaluation of medical therapy of senile and diabetic cataracts. 696 92

The prevalence of cataracts is significantly lower in patients with rheumatoid arthritis receiving aspirin (mean of 2,700 mgs daily for an average of 10.4 years) as compared to the matched population not receiving aspirin. Similarly, fewer cataracts were found among a population with diabetes and rheumatoid arthritis receiving aspirin (mean of 2,340 mgs daily for an average of 8.8 years) as compared to the matched population on no aspirin. The effects of aspirin on cataract formation may result from 1) lowering of plasma tryptophan levels and increased excretion of tryptophan metabolites, 2) inhibition of aldose reductase and sorbitol formation in the diabetic lens, 3) inhibition of tryptophan or kynurenine binding to lens protein.
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PMID:Aspirin effect on cataract formation in patients with rheumatoid arthritis alone or combined with diabetes. 726 27

The etiology of diabetic cataract is usually explained by the following process; the conversion of glucose and galactose to polyol by aldose reductase, then the accumulation of polyol in lens, and the opacity of lens. Another explanation is that the hyperoxidation of lens membrane due to an increase of active oxygen and lipid peroxide in lens induces diabetic cataract. The experimental animals used in the present study were rats with galactose cataract and streptozotocin cataract. We measured the levels of antioxidants (glutathione, ascorbic acid) and lipid peroxide (malonodialdehyde) in lens, aqueous humor and vitreous body. Furthermore we studied the effects of aldose reductase inhibitor (TAT) on these levels. In streptozotocin diabetes rats, the increased malonodialdehyde levels in lens, aqueous humor and serum were suppressed by TAT administration. In galactose and streptozotocin diabetes rats, the decreased levels of glutathione and ascorbic acid were suppressed by TAT administration.
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PMID:[Biochemical changes in lens, aqueous humor and vitreous body and effects of aldose reductase inhibitor (TAT) on rats with experimental diabetes]. 755 22

Diabetes mellitus has an effect on many organ systems including the eye, kidney and peripheral nerve. Many of these complications develop in animal models of diabetes, which has allowed some of the mechanisms of damage in target organs to be studied. Aldose reductase, an intracellular enzyme, converts glucose to sorbitol, and it is the intracellular accumulation of sorbitol which is thought to result in irreversible damage. In the diabetic eye the increased sorbitol accumulation in both the lens and the retina has been implicated in the pathogenesis of cataract and retinopathy, the major ocular complications of diabetes. In those experimental models which demonstrate characteristic diabetic complications, pharmacological inhibition of the enzyme aldose reductase has resulted in prevention of target organ damage. This paper summarises the experimental evidence upon which the clinical trials of aldose reductase inhibitors in diabetic patients have been initiated and the results of published drug trials in these patients.
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PMID:Does aldose reductase have a role in the development of the ocular complications of diabetes? 760 42

This paper reviews the changes which occur in the human lens in diabetes. They include refractive changes and cataract and age-related increases in thickness, curvatures, light scattering, autofluorescence and yellowing. The incidence of cataract is greatly increased over the age of 50 years, slightly more so in women, compared with non-diabetics. Experimental models of sugar cataract provide some evidence for the mechanism of the uncommon, but morphologically distinct, juvenile form of human diabetic cataract, where an osmotic mechanism due to sugar alcohol accumulation has been thoroughly studied in diabetic or galactose-fed rats. The discrepancy between the ready accumulation of sugar alcohol in the lens in model systems and the very slow kinetics of aldose reductase (AR) has not been satisfactorily explained and suggests that the mechanism of polyol formation is not yet fully understood in mammalian systems. The activity of AR in the human lens lies mainly in the epithelium and there appears to be a marginal expectation that sufficient sorbitol accumulates in cortical lens fibres to explain the lens swelling and cataract on an osmotic basis. This is even more so in the cataracts of adult diabetics, which resemble those of age-related non-diabetic cataracts in appearance. The very low levels of sorbitol in adult diabetic lenses make an osmotic mechanism for the increased risk of cataract even less likely. Other mechanisms, including glycation and oxidative stress, are discussed. The occurrence of cataract is a predictor for increased mortality in the diabetic.
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PMID:The lens in diabetes. 760 46

Monoterpene glucosides, perillosides A and C, obtained from the leaves of Perilla frutescens, were found to be inhibitors of aldose reductase (EC 1.1.1.21) which is considered to be a key enzyme in diabetic complications such as cataract. The apparent type of inhibition of rat lens aldose reductase by perillosides A and C was competitive with respect to glyceraldehyde and their K(i) values were 1.4 x 10(-4) and 2.3 x 10(-4) M, respectively. The type of inhibition by their tetraacetates was non-competitive with respect to the same substrate, although their inhibitory effects were increased by about one order of magnitude compared with those of the perilllosides and the K(i) values were 2.5 x 10(-5) and 7.1 x 10(-5) M, respectively. We also prepared related monoterpene glucosides and their tetraacetates and determined their inhibitory activities towards aldose reductase in order to elucidate the relationship between structure and inhibitory activity.
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PMID:Inhibitory effects of perillosides A and C, and related monoterpene glucosides on aldose reductase and their structure-activity relationships. 764 10

To confirm the effect of a new aldose reductase inhibitor (ARI), rat lenses were cultured with xylose. ARI prevented opacities and reduced lens hydration caused by xylose. Next, cataract was produced by feeding a diet containing 50% galactose. ARI was tested for amelioration of cataract. On day 19 after feeding of galactose, nuclear cataracts were visible in 75% of the animals receiving only galactose, while nuclear cataracts were not observed in animals treated with ARI. In galactose cataract, lens hydration and calcium were significantly increased. Calpain in soluble and insoluble fractions was decreased. Alpha- and beta-crystallins were proteolyzed. These changes were inhibited by administration of ARI. These results suggested that proteolysis by calpain is an underlying mechanism in formation of sugar cataract in rat lens.
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PMID:Proteolysis by calpain is an underlying mechanism for formation of sugar cataract in rat lens. 772 Apr 3

Research into the biological basis of lens transparency has demonstrated the implication of lens sugar stress in the diabetic cataract whereas senile cataract is the result of natural degeneration which is enhanced by various external factors such as cosmic and ionizing rays, or oxidative processes. Drugs have been developed which are aimed at being effective on lens pathological physiology and metabolism, concurrently. Such molecules: aldose reductase inhibitors (ARIs: sorbinil, AD-5467, CT-112 and imirestat), acetyl salicylic acid (ASA), salicylate (SA) and sodium monomethyl trisilanol orthohydroxybenzoate (SMB, a prodrug for salicylate) have undergone pharmacodynamic, pharmacokinetic and/or clinical studies which are presented here. ARIs have shown efficacy in slowing down and preventing the progression of experimental sugar cataracts; sorbinil can partially reverse the very early morphological signs of sugar cataract. Sorbinil and imirestat have also demonstrated anti-oxidant properties. ARIs administration (per os or by topical instillation) generally results in lens levels compatible with concentrations that are efficient on biochemical mechanisms of cataract formation. However, at the present time, clinical evaluations are in progress and as yet, there is no confirmation of their efficacy in man. ASA and SA can prevent various mechanisms of lens protein denaturation; they inhibit AR and prevent, in vitro, the formation of some pigments found in the aged cataractous lens. Extrapolation of the ASA ocular pharmacokinetics results in animal to man, suggest that ASA administration per os could result in efficacious levels in the lens. This is also sustained by the observation of a reduced frequency of cataracts in ASA treated diabetic rheumatoid arthritis patients. SMB pharmacokinetic studies have shown small but persistent levels of the active principle in the lens. They suggest that the capsule slows down SA diffusion into the lens and that, on the contrary, lens epithelium facilitates its penetration. Preliminary results of pharmacodynamic studies are given.
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PMID:Drugs designed to maintain the transparence of the ocular lens. 785 38

Optically active and racemic 2-substituted 6-fluoro-2,3-dihydrospiro[4H-1- benzopyran-4,4'-imidazolidine]-2',5'-diones were synthesized stereoselectively from (+)-, (-)-, and (+/-)-6-fluoro-3, 4-dihydro-4-oxo-2H-1-benzopyran-2-carboxylic acid [(+)-1, (-)-1, and (+/-)-1], respectively, for evaluation as new aldose reductase inhibitors. Among these compounds, the 2S,4S compounds were found to be more potent inhibitors of aldose reductase in vitro and in vivo than the corresponding 2R,4R enantiomers. The chloromethyl compound [(+)-5] showed highly potent activities in inhibiting cataract formation in the lenses and polyol accumulation in the sciatic nerve of rats.
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PMID:Synthesis and aldose reductase inhibitory activity of 2-substituted 6-fluoro-2,3-dihydrospiro[4H-1-benzopyran-4,4'-imidazolidine]-2',5'-dio nes. 792 71


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