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)

Blindness in diabetics is largely due to retinopathy and/or cataract. Hyperglycaemia and the duration of diabetes are major risk factors for the development of cataract and retinopathy. This review details some of the reactions of glucose that are relevant to the development of complications, and follows the elucidation of monosaccharide autoxidation and its relevance to the aldose reductase reaction and its determination. Inhibitors of this 'aldose reductase' reaction are shown to have a number of effects which may be of importance to their action in vivo. The pharmacological implications of chemotherapy for diabetics with complications are briefly discussed.
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PMID:Aldose reductase inhibitors and cataract. 190

To assess the significance of glycation, nonenzymatic browning, and oxidation of lens crystallins in cataract formation in elderly diabetic patients, we measured three distinct products of glycation, browning, and oxidation reactions in cataractous lens crystallins from 29 diabetic patients (mean +/- SD age 72.8 +/- 8.8 yr) and 24 nondiabetic patients (age 73.5 +/- 8.3 yr). Compounds measured included 1) fructoselysine (FL), the first stable product of glycation; 2) pentosidine, a fluorescent, carbohydrate-derived protein cross-link between lysine and arginine residues formed during nonenzymatic browning; and 3) N epsilon-(carboxymethyl)lysine (CML), a product of autoxidation of sugar adducts to protein. In diabetic compared with nondiabetic patients, there were significant increases (P less than 0.001) in HbA1 (10.2 +/- 3.1 vs. 7.1 +/- 0.7%), FL (7.6 +/- 5.4 vs. 1.7 +/- 1.2 mmol/mol lysine), and pentosidine (6.3 +/- 2.8 vs. 3.8 +/- 1.9 mumol/mol lysine). The disproportionate elevation of FL compared with HbA1 suggests a breakdown in the lens barrier to glucose in diabetes, whereas the increase in pentosidine is indicative of accelerated nonenzymatic browning of diabetic lens crystallins. CML levels were similar in the two groups (7.1 +/- 2.4 vs. 6.8 +/- 3.0 mmol/mol lysine), providing no evidence for increased oxidative stress in the diabetic cataract. Thus, although the modification of lens crystallins by autoxidation reactions was not increased in diabetes, the increase in glycation and nonenzymatic browning suggests that these processes may acclerate the development of cataracts in diabetic patients.
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PMID:Role of glycation in modification of lens crystallins in diabetic and nondiabetic senile cataracts. 190 46

Glucocorticoid-induced cataract formation appears to proceed via oxidation or peroxidation steps possibly caused by multiple activities of glucocorticoid in the living system. Attempts were made to modify GC-induced metabolic changes and prevent cataract formation using intermediates of the citric acid cycle. The compounds were applied to the embryos at 3, 10 and 20 hr after the administration of hydrocortisone succinate sodium (HC:0.25 mumol/egg) to 15-day-old eggs. At 48 hr after HC treatment the lenses were classified and analyzed. Almost all lenses were classified as stage IV-V (greater than 94%). However, the application of sodium isocitrate (IC:15 mumol/egg) which was the most potent among several intermediates tested showed a significant preventive effect against cataract formation. The administration of IC prevented the decline of GSH, the elevations of LPO and reduced the marked elevation of glucose in the lens caused by HC. The IC treatment also diminished the elevation of LPO in blood and liver. The above effects by IC on HC-induced events may be due to the action of IC in preventing the early decline of hepatic GSH caused by HC. Possibly IC was utilized as an intermediate of the citric acid cycle and a substrate for isocitrate dehydrogenase in cytosol to modify GC-induced metabolic changes.
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PMID:Preventive effect of isocitrate on glucocorticoid-induced cataract formation of developing chick embryo. 191 99

We evaluated the occurrence or progression of nuclear sclerosis of the crystalline lens in 100 eyes after vitrectomy for removal of idiopathic epiretinal membranes causing macular pucker. The follow-up period ranged from six to 99 months (average, 29 months). Visually significant nuclear sclerosis was present preoperatively in three of the operated on eyes and four of the fellow eyes. The rate of occurrence or progression of visually significant nuclear sclerosis was far greater in the operated on eyes (P less than .0001). Of 100 patients, 80 operated on eyes and 24 fellow eyes had visually significant nuclear sclerosis or had undergone previous cataract extraction at the conclusion of the study. Different concentrations of glucose in the intraocular irrigating solution did not affect occurrence of later nuclear sclerosis. Patients older than 50 years of age had a far greater incidence of later nuclear sclerosis than patients younger than 50 years of age (P = .0003). Nuclear sclerosis may be caused by altered lens metabolism after removal of part of the vitreous gel, since nuclear sclerosis also occurs in other conditions associated with vitreous liquefaction.
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PMID:Nuclear sclerotic cataract after vitrectomy for idiopathic epiretinal membranes causing macular pucker. 201 45

Cataract is the major cause of blindness worldwide. Non-enzymic modification of lens proteins leading to a disruption of their short range order is an important route to cataract formation. A reaction between lens proteins and a compound found in the lens indicates a potential role for that compound in cataract formation. The reactions of glucose and fructose with lens protein in vitro were investigated. Fructose bound to lens protein at pH 6.9 in a time-dependent fashion over a period of 20 days. The reactions of both glucose and fructose with lens proteins and bovine serum albumin led to the formation of coloured and fluorescent compounds. The formation of such compounds was greater with fructose than with glucose. The kinetics of the reactions of lens proteins and bovine serum albumin with fructose as measured by the formation of the above compounds were not identical. This point must be appreciated when attempting to extrapolate from results obtained with bovine serum albumin as to the reactions of lens proteins. The incubation of lens proteins with fructose led to an enhancement of protein aggregation. The implications of the reactions between lens proteins and fructose for the formation of cataract in diabetics are discussed. Ibuprofen intake is associated with protection against cataract. At relatively high concentrations (10-20 mM) ibuprofen decreased the binding of fructose to lens protein: this decrease was statistically significant at selected times (Student's t-test, P less than 0.05). The formation of fluorescent compounds in the presence of fructose was also decreased by ibuprofen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Non-enzymic modification of lens proteins by glucose and fructose: effects of ibuprofen. 201 2

413 NIDDM Sudanese patients were studied. The patients' ages at the onset of diabetes ranged from 20-72 years, with the majority of patients (44%) developing diabetes at the age between 40-50 years. Female to male ratio was 1.9:1. 46.2% of patients were obese and a family history of first degree relatives was obtained in 63% of patients. Complications of diabetes in this study were as follows: Neuropathy (31.5%), retinopathy (17.4%), cataract (16%), nephropathy (9.2%), coronary heart disease (5.1%), cerebrovascular disease (4.4%) and peripheral vascular disease (3.4%). Microangiopathic complications of diabetes were significantly related to the duration of diabetes and the degree of hyperglycaemia (P less than 0.001 using chi 2 test). Macroangiopathic complications were significantly related to aging and hyperglycaemia. Patients with good metabolic control (blood glucose less than 160 mg%) had less prevalence of complications than uncontrolled patients. We conclude that NIDDM is a common type of diabetes in our diabetic clinic. It is a disease with severe complications and morbidity and needs more attention regarding metabolic control, since good control reduces the prevalence of diabetic complications.
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PMID:Features of non-insulin-dependent diabetes mellitus (NIDDM) in the Sudan. 201 36

Crystallin glycation seems to play an important role in the development of diabetic cataract. In order to understand the role of glycation in cataractogenesis, levels of glycation of different crystallins were determined by in vitro glycation of rat lens soluble fraction with 50 mM glucose or glucose-6-phosphate (G6P) for up to 5 days and in streptozotocin-diabetic rats during various stages of cataract development. All samples were reduced with [3H]NaBH4 and the tritium incorporation was taken as a measure of glycation. Proteins were routinely separated by molecular sieve HPLC. In vitro studies with glucose showed that gamma-crystallin was readily glycated and reached a plateau by 3 days, while alpha- and beta-crystallins were glycated slowly initially up to 3 days followed by a steep increase as seen on the fifth day. Incubation with 50 mM G6P resulted in an approximately two fold increase in glycation compared to glucose of all crystallins. In the diabetic animals also gamma-crystallin glycation increased approximately twofold within 15 days after the onset of diabetes and an additional threefold within the next 45 days followed by a slight decrease during the following 90-120 days. Increase in glycation, on the contrary, was very slow up to 30 days for alpha-crystallin and up to 60 days for beta-crystallin, followed by a steep increase during the remainder of the experimental period. The high molecular weight (HMW) aggregates had higher levels of glycation than other proteins; the insoluble HMW aggregates contained higher levels of glycation than the soluble HMW aggregates.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential glycation of rat alpha-, beta- and gamma-crystallins. 203 22

Anterior segment necrosis is an acute or chronic process occasioned by embarrassment of the blood supply of the anterior segment of the eye. In the acute form this vascular obstruction leads to severe corneal oedema, necrosis of anterior uvea, hypotony and cataract formation. Depression of aqueous humour formation accounts for severe reduction of glucose levels in corneal stroma and aqueous humour lasting for two days after cautery of the long posterior ciliary arteries (LPCA) in rabbits. Lactate levels are initially significantly elevated but return to normal after one week. Stromal hydration was elevated for one week but then returned to normal. Corneal epithelial glycogen was diminished at one and two days after surgery but then returned to normal. Although unproven, oxygen deprivation probably plays a major role in endothelial ischaemia and therefore corneal oedema. It is concluded that the abnormalities seen in anterior segment necrosis stem from changes in aqueous metabolic components resulting from severely reduced aqueous turnover. Hyperbaric oxygen and intracameral metabolite substitution are unproven treatments but merit further experimental study.
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PMID:The intraocular changes of anterior segment necrosis. 207 Aug 80

Transplantation of isolated islets is a promising approach in the treatment of diabetes. We have examined the long-term effects on the late complications of islet transplantation in an experimental diabetes model in the rat. Diabetes was induced by streptozotocin (70 mg/kg i.v.) and the rats were treated with either insulin (daily injection of 40 U) or transplantation of 1,000 freshly isolated, hand-picked, islets into the left renal subcapsular space. Both islet transplantation and insulin treatment completely normalized the increased levels of blood glucose, urine volume and water intake that were observed in the diabetic rats. The decreased growth rate of the diabetic rats was almost normalized by both treatment protocols. As for late complications, after 3 months, all untreated diabetic rats had cataract. They also had swelling and vacuolation of renal tubular cells, and, consistent with this, very high levels of urinary beta 2-microglobulin excretion. Both islet transplantation and insulin treatment completely prevented these late complications. Thus, islet transplantation to the renal subcapsular space is in this experimental model as good as insulin treatment in treating the clinical signs of diabetes and in preventing diabetic complications in the eye and kidney.
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PMID:Islet transplantation to the renal subcapsular space improves late complications in streptozotocin-diabetic rats. 207 89

Galactitol and sorbitol concentrations in plasma were determined in patients (with or without cataract) in whom homo- or heterozygosity for galactokinase, galactose-1-phosphate uridyltransferase, systemic or peripheral UDP-galactose epimerase and sorbitol dehydrogenase deficiency was confirmed. For the above disorders it can be concluded that elevation of plasma polyols is not always related to the presence or absence of cataract. In all cases with cataract, however, the plasma galactitol or sorbitol levels were elevated. In another group of patients with unexplained congenital or infantile cataracts, but without apparent enzyme defects, mild to moderately elevated concentrations of plasma galactitol or sorbitol were found in about 45%. In 8% of this group the cataract and the elevated plasma galactitol concentration could possibly have been related to partial maternal enzyme deficiency. In all the other cases the elevated plasma polyol concentration remains unexplained but could indicate a further cause of cataract formation due to a hitherto unknown galactose or glucose metabolic aberration.
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PMID:Plasma polyol levels in patients with cataract. 212 18


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