Biochemical and morphological changes during development of sugar cataract in Otsuka Long-Evans Tokushima fatty (OLETF) rat

Polyethylene microbeads are more critically toxic to the eyes and reproduction than the kidneys or growth in medaka, Oryzias latipes

Many studies using experimental and wild animals have reported negative effects of microplastic beads (MPs) ingestion. However, data regarding the lowest observed adverse effect levels (LOAELs) of MPs remain limited. Our aim was to evaluate the adverse effect levels of polyethylene MPs (10-63 μm diameter) with respect to growth, reproduction, and the eyes and kidneys of medaka (Oryzias latipes) under breeding conditions to contribute to future research involving LOAEL determinations. Fish were exposed to 0.009 mg-MPs (approximately 1000 particles)/L to 0.32 mg-MPs (approximately 40,000 particles)/L for 12 weeks. The eyes and kidneys were evaluated by histopathologic analysis. Although histologic analyses indicated an absence of MPs in the tissues, the eyes and kidneys as well as reproduction were adversely affected by increasing MP concentrations. The number of spawned eggs decreased, and changes were noted in the eyes of fish exposed to ≥0.032 mg-MPs/L under breeding conditions. The eyes exhibited thinning of the optic nerve fiber layer and dilatation of retinal capillaries compared with medaka not treated with MPs. Changes in the kidneys were observed in fish exposed to ≥0.065 mg-MPs/L. The mesangial matrix in the glomerulus of the kidneys was expanded compared with non-treated medaka, suggesting a deterioration in renal function. Analyses of an oxidative stress marker in the tissues indicated that lesion progression was associated with increased oxidative stress. Furthermore, a comparison of adverse effect levels suggested that MPs were more toxic to the eyes and reproduction than the kidneys or growth. Our data should prove useful for determining the LOAELs of polyethylene beads on vertebrates and enhance understanding of the mechanism underlying the biological toxicity of polyethylene MPs.

Controlled blood sugar improves the eye's accommodative ability in type-1 diabetes

PURPOSE

To evaluate the impact of blood sugar level on ocular measures, including refractive error (RE), amplitude of accommodation (AoA), and lag of accommodation (LoA), in pre-presbyopes with type-1 diabetes.

METHOD

The fasting blood sugar (FBS) and ocular measures of type-1 diabetes patients (age: 14-39 years; n = 30) on insulin treatment was recorded while they fasted on two separate visits, at baseline and 3 months later. The AoA and LoA was measured with the appropriate spectacle correction worn. The Welch's t-test was used for comparison of the baseline measures between the normal FBS ≤ 7 (n = 10) and higher FBS > 7 (n = 20) patients, and the paired t-test used to investigate for differences between the baseline and follow-up data in patients with changes in FBS.

RESULTS

On average, the spectacle correction for the normal FBS group was marginally more myopic (RE: -0.30 ± 0.67 D vs. +0.18 ± 1.00 D, p = 0.032), and they showed greater AoA (5.38 ± 1.08 D vs. 3.68 ± 1.43 D, p < 0.001) and lower LoA (1.00 ± 0.30 D vs. 1.30 ± 0.38 D, p = 0.004) compared with the higher FBS group at baseline. On the follow-up visit attended by 25 patients, the FBS of 15 patients was reduced by an average of 7.0 mmol/L, 8 patients had an average increase of 5.2 mmol/L, while 2 patients recorded no changes relative to the baseline. The patients whose FBS was reduced showed improvement in the mean AoA from 3.78 ± 1.58 D to 4.88 ± 1.61 D (p < 0.001) and a reduction in the mean LoA from 1.37 ± 0.40D to 0.87 ± 0.19D (p < 0.001), whereas those with deteriorated control of the FBS showed an opposite trend.

CONCLUSIONS

Controlling hyperglycemia improves ocular accommodation in type-1 diabetes.

Ocular lesions in leptin receptor-deficient medaka (Oryzias latipes)

Ocular lesions in leptin receptor-deficient medaka were examined histopathologically at 10, 28, and 37 weeks post hatching. Leptin receptor-deficient medaka at 28 and 37 weeks old showed hyperglycemia and hypoinsulinemia. Histopathologically, vacuolation, swelling, fragmentation, and liquefaction of the lens fibers and dilatation of the retinal central veins, retinal capillaries, iridal veins and capillaries, and choroidal veins were observed in leptin receptor-deficient medaka at 28 and 37 weeks old. Thinning of the total retina, pigment epithelial layer, layer of rods and cones, outer granular layer, outer plexiform layer, inner granular layer, and inner plexiform layer was observed in leptin receptor-deficient medaka at 28 and 37 weeks compared with in control medaka. These histopathological characteristics in leptin receptor-deficient medaka are similar to characteristics in ocular lesions of rodent models for type II diabetes mellitus, making leptin receptor-deficient medaka a useful model of diabetic cataract and retinopathy.

The role of Prdx6 in the protection of cells of the crystalline lens from oxidative stress induced by UV exposure

PURPOSE

The immediate aim of this study was to investigate alterations in peroxiredoxin (Prdx) 6 at posttranslational levels, and the levels of protein oxidation, lipid peroxidation, and reactive oxygen species (ROS) in lens epithelial cells (LECs) after exposure to severe oxidative stress, such as ultraviolet-B (UV-B). Our ultimate aim was to provide new information on antioxidant defenses in the lens and their regulation, thereby broadening existing knowledge of the role of Prdx6 in lens physiology and pathophysiology.

METHODS

The expression of the hyperoxidized form of Prdx6 and oxidation of protein were analyzed by western blotting and the OxyBlot assay in human LECs (hLECs). ROS levels were quantified using DCFH-DA dye, and cell viability was quantified by the MTS and TUNEL assays. To evaluate the protective effect of Prdx6, we cultured lenses with or without the TAT transduction domain (TAT-HA-Prdx6) and observed (and photographed) the cultures at specified time-points after the exposure to UV-B for the development of opacity.

RESULTS

Prdx6 in hLECs was hyperoxidized after exposure to high amounts of UV-B. UV-B treatment of hLECs increased the levels of cell death, protein oxidation, and ROS. hLECs exposed to UV-B showed higher levels of ROS, which could be reduced by the application of extrinsic TAT-HA-Prdx6, attenuating UV-B-induced lens opacity and apoptotic cell death.

CONCLUSION

Excessive oxidative stress induces the hyperoxidation of Prdx6 and may reduce the ability of Prdx6 to protect LECs against ROS or stresses. Because extrinsic Prdx6 could attenuate UV-B-induced abuse, this molecule may have a potential in preventing cataractogenesis.

Diabetic complications in obese type 2 diabetic rat models

We overviewed the pathophysiological features of diabetes and its complications in obese type 2 diabetic rat models: Otsuka Long-Evans Tokushima fatty (OLETF) rat, Wistar fatty rat, Zucker diabetic fatty (ZDF) rat and Spontaneously diabetic Torii (SDT) fatty rat. Pancreatic changes with progression of diabetes were classified into early changes, such as islet hypertrophy and degranulation of β cells, and degenerative changes, such as islet atrophy and fibrosis of islet with infiltration of inflammatory cells. Renal lesions in tubuli and glomeruli were observed, and nodular lesions in glomeruli were notable changes in OLETF and SDT fatty rats. Among retinal changes, folding and thickening were interesting findings in SDT fatty rats. A decrease of motor nerve conduction velocity with progression of diabetes was presented in obese diabetic rats. Other diabetic complications, osteoporosis and sexual dysfunction, were also observed. Observation of bone metabolic abnormalities, including decrease of osteogenesis and bone mineral density, and sexual dysfunction, including hypotestosteronemia and erectile dysfunction, in obese type 2 diabetic rats have been reported.

Osmotic stress induced oxidative damage: possible mechanism of cataract formation in diabetes

Chronic hyperglycemia causes increased level of reactive oxygen species which is thought to be involved in the pathogenesis of diabetes associated complications including cataract. In diabetic cataractous lens, over production of free radicals and decreased capacity of antioxidant defense system are the major contributors to oxidative damage by polyol pathway and advanced glycation end products. The current study focused on analysis of factors associated with osmotic imbalance and oxidative stress in aging and diabetic human cataractous lenses. We examined activities of polyol pathway enzymes, G6PD and glutathione system in lenses from subjects suffering from cataract due to aging and diabetes. We observed elevated activities of aldose reductase and sorbitol dehydrogenase while G6PD and glutathione system enzyme activities were found to be lower in cataractous subjects suffering from diabetes. The findings from the current study support the premise that osmotic imbalance, AGEs formation and oxidative stress contribute synergistically to the development of lens opacity in hyperglycemia.

Canine cataracts, diabetes mellitus and spontaneous lens capsule rupture: a retrospective study of 18 dogs

OBJECTIVE

To describe the clinical presentation and surgical outcome of diabetic canine patients with cataracts and preoperative spontaneous lens capsule rupture.

ANIMALS STUDIED

A total of 20 dogs and 40 eyes were included in the retrospective evaluation. The patients' ages ranged from 5 to 14 years (mean 8.5 years).

RESULTS

All dogs had clinical diabetes mellitus, with the duration since diagnosis ranging from 30 to 240 days (mean 123 days). Cataracts were bilateral and noted to have been present for 14-112 days (mean 39 days). Of the 40 eyes affected with cataracts, 30 had a spontaneous rupture of the lens capsule prior to surgery. The capsular rupture was diagnosed on clinical examination in 28/30 eyes and was noted intraoperatively in 2/30. The location of the capsular rupture was equatorial in 29/30 and posterior in 1/30 eyes. Surgery was performed in 38/40 eyes, with one case lost to follow-up without surgical intervention. Prior to surgery, routine diagnostic ophthalmic examination, ocular ultrasound, electroretinography, and systemic evaluation were performed in all dogs. Surgical procedures included phacoemulsification in 28/40 eyes, with IOL placement performed in 20/28 eyes. Intrascleral prosthesis placement or enucleation was performed in 8/40 and 2/40 eyes, respectively, due to a significantly reduced ERG or secondary glaucoma.

CONCLUSIONS

The duration of clinical follow-up (19/20 dogs) ranged from 1 to 36 months (mean 12.9 months). All eyes that had cataract surgery with or without IOL placement were sighted at the time of the last follow-up examination. Spontaneous lens capsule rupture associated with diabetes mellitus, cataract and rapid lens intumescence occurs in the dog. Early surgical intervention, prior to secondary complications of glaucoma and loss of retinal function, is associated with a favorable outcome.

Partial reversal by rutin and quercetin of impaired cardiac function in streptozotocin-induced diabetic rats

The present investigation was carried out to evaluate the effects of the cyclodextrin complexes quercetin and rutin on left ventricle dysfunction in streptozotocin-induced diabetic rats. Diabetes was induced by streptozotocin (45 mg/kg body mass, i.v.) in Sprague–Dawley rats. Echocardiography and biochemical and histological studies were carried out under normal control, diabetic untreated, normal and diabetic vehicle (β-cyclodextrin, p.o.), quercetin- (100 and 300 mg/kg, p.o.), and rutin- (100 and 300 mg/kg, p.o.) treated normal and diabetic animals at varying time intervals (1 and 12 weeks). The increase in the serum triglycerides and cholesterol levels was attenuated in the cyclo dextrin complexes of rutin-treated animals significantly more than in the quercetin-treated and diabetic vehicle-treated animals. Left ventricular diastolic dysfunction was observed in diabetic vehicle-treated animals after 12 weeks of the study as determined by a significant decrease in E-wave (45.91%), an increase in the A-wave (75.55%), and a decrease in the E/A ratio (70.14%). However, the percent decrease (after 12 weeks) in the E-wave, increase in the A-wave, and decrease in the E/A ratio were less in the cyclodextrin complexes of rutin-treated animals (100 and 300 mg/kg), which had the following values: E-wave, 12.22% and 13.80%; A-wave, 25.90% and 10.40%; and E/A ratio, 31.01% and 20.52%. In the quercetin-treated animals (100 and 300 mg/kg), which had the following values: E-wave, 40.44% and 36.44%; A-wave, 52.98% and 29.28%; and E/A ratio, 61.70% and 51.11%. Histopathological studies revealed that the degree of myocardial necrosis was less in rutin-treated animals compared with quercetin and diabetic vehicle-treated animals: rutin < quercetin < β-cyclodextrin. Myocardial fructose levels were significantly increased in the diabetic vehicle-treated animals after 12 weeks of the study, suggesting an increment in the myocardial polyol pathway activity. However, myocardial fructose levels were significantly decreased in the rutin- and quercetin-treated animals compared with the vehicle-treated animals, possibly owing to their aldose reductase inhibitory activity. Quercetin and rutin treatment did not influence the echocardiographical and histo logical parameters in normal animals. Results from the present investigation demonstrated that rutin has a cardioprotective activity, and we conclude that the observed cardioprotection with rutin may be due to its aldose reductase inhibitory activity, as the enhanced aldose reductase pathway is implicated in the development of left ventricle dysfunction by several studies.Key words: aldose reductase inhibitors, bioflavonoids, diabetic cardiomyopathy, myocardial fructose, polyol pathway.

Preparation and characterization of polyclonal antibodies against ARL-1 protein

AIM: To prepare and characterize polyclonal antibodies against aldose reductase-like (ARL-1) protein.

METHODS: ARL-1 gene was inserted into the E. coli expression vector pGEX-4T-1(His)6C and vector pQE-30. Recombinant ARL-1 proteins named ARL-(His)₆ and ARL-GST were expressed. They were purified by affinity chromatography. Sera from domestic rabbits immunized with ARL-(His)₆ were purified by CNBr-activated sepharose 4B coupled ARL-GST. Polyclonal antibodies were detected by Western blotting.

RESULTS: Recombinant proteins of ARL-(His)₆ with molecular weight of 35.7 KD and ARL-GST with molecular weight of 60.8 KD were highly expressed. The expression levels of ARL-GST and ARL-(His)₆ were 15.1% and 27.7% among total bacteria proteins, respectively. They were soluble, predominantly in supernatant. After purification by non-denatured way, SDS-PAGE showed one band. In the course of polyclonal antibodies purification, only one elution peak could be seen. Western blotting showed positive signals in the two purified proteins and the bacteria transformed with pGEX-4T-1(His)₆ C-ARL and pQE-30-ARL individually.

CONCLUSION: Polyclonal antibodies are purified and highly specific against ARL-1 protein. ARL-GST and ARL-(His)₆ are highly expressed and purified.

Aldose reductase activity and glucose-related opacities in incubated lenses from dogs and cats

OBJECTIVE

To determine responses of canine and feline lenses to incubation in a medium with a high glucose concentration.

SAMPLE POPULATION

Lenses from 35 dogs and 26 cats.

PROCEDURE

Glucose concentrations were measured in paired lenses from 25 dogs and 17 cats after incubation for 14 days in high-glucose (30 mmol of glucose/L) or control (6 mmol of glucose/L) medium. Aldose reductase activity was measured spectrophotometrically in the incubated lenses and in freshly frozen lenses from 10 dogs and 9 cats. Two lenses of each group were studied histologically.

RESULTS

Canine and feline lenses in high-glucose medium developed glucose-specific opacities of variable localization and extent. Canine lenses developed equatorial vacuoles, but severity of the lesions was not associated with the age of the dog. Lenses from young cats (< or = 4 years old) developed extensive posterior cortical opacities, whereas those from older cats (> 4 years old) did not. Glucose concentrations were similar in all lenses incubated in high-glucose medium; however aldose reductase activity was significantly lower in lenses from older cats, compared with lenses from young cats and from dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

High aldose reductase activity and glucose-related opacities suggest a central role for this enzyme in the pathogenesis of diabetic cataracts in dogs and cats. Because onset of diabetes mellitus usually occurs in cats > 7 years of age, low activity of aldose reductase in lenses of older cats may explain why diabetic cataracts are rare in this species despite hyperglycemia.