Evaluation of Neonatal Streptozotocin Induced Diabetic Rat Model for the Development of Cataract

Type 2 diabetes (T2D) generally follows prediabetes (PD) conditions such as impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). Although studies reported an association of IGT or IFG with cataract, the experimental basis for PD associated cataract is not known. Hence, we evaluated neonatal streptozotocin (nSTZ) induced rat model to study PD associated cataractogenesis by injecting STZ to two-day old rats. While majority (70%) of nSTZ injected pups developed IGT (nSTZ-PD) by two months but not cataract even after seven months, remaining (30%) nSTZ rats developed hyperglycemia (nSTZ-D) by two months and mature cataract by seven months. Lens biochemical analysis indicated increased oxidative stress as indicated by increased SOD activity, lipid peroxidation, and protein carbonyl levels in nSTZ-D cataractous lens. There was also increased polyol pathway as assessed by aldose reductase activity and sorbitol levels. Though nSTZ-PD animals have not shown any signs of lenticular opacity, insolubilization of proteins along with enhanced polyol pathway was observed in the lens. Further there was increased oxidative stress in lens of IGT animals. These results suggest that oxidative stress along with increased polyol pathway might play a role in IGT-associated lens abnormalities. In conclusion, nSTZ-PD rat model could aid to investigate IGT-associated lens abnormalities

The Isolation and Characterization of β-Glucogallin as a Novel Aldose Reductase Inhibitor from Emblica officinalis

Diabetes mellitus is recognized as a leading cause of new cases of blindness. The prevalence of diabetic eye disease is expected to continue to increase worldwide as a result of the dramatic increase in the number of people with diabetes. At present, there is no medical treatment to delay or prevent the onset and progression of cataract or retinopathy, the most common causes of vision loss in diabetics. The plant Emblica officinalis (gooseberry) has been used for thousands of years as a traditional Indian Ayurvedic preparation for the treatment of diabetes in humans. Extracts from this plant have been shown to be efficacious against the progression of cataract in a diabetic rat model. Aldose reductase (ALR2) is implicated in the development of secondary complications of diabetes including cataract and, therefore, has been a major drug target for the development of therapies to treat diabetic disease. Herein, we present the bioassay-guided isolation and structure elucidation of 1-O-galloyl-β-D-glucose (β-glucogallin), a major component from the fruit of the gooseberry that displays selective as well as relatively potent inhibition (IC50 = 17 µM) of AKR1B1 in vitro. Molecular modeling demonstrates that this inhibitor is able to favorably bind in the active site. Further, we show that β-glucogallin effectively inhibits sorbitol accumulation by 73% at 30 µM under hyperglycemic conditions in an ex-vivo organ culture model of lenses excised from transgenic mice overexpressing human ALR2 in the lens. This study supports the continued development of natural products such as β-glucogallin as therapeutic leads in the development of novel therapies to treat diabetic complications such as cataract

Aldo-keto reductases in the eye

Aldose reductase (AKR1B1) is an NADPH-dependent aldo-keto reductase best known as the rate-limiting enzyme of the polyol pathway. Accelerated glucose metabolism through this pathway has been implicated in diabetic cataract and retinopathy. Some human tissues contain AKR1B1 as well as AKR1B10, a closely related member of the aldo-keto reductase gene superfamily. This opens the possibility that AKR1B10 may also contribute to diabetic complications. The goal of the current study was to characterize the expression profiles of AKR1B1 and AKR1B10 in the human eye. Using quantitative reverse transcriptase-PCR and immunohistochemical staining, we observed expression of both AKR genes in cornea, iris, ciliary body, lens, and retina. Expression of AKR1B1 was the highest in lens and retina, whereas AKR1B10 was the highest in cornea. Lenses from transgenic mice designed for overexpression of AKR1B10 were not significantly different from nontransgenic controls, although a significant number developed a focal defect in the anterior lens epithelium following 6 months of experimentally induced diabetes. However, lenses from AKR1B10 mice remained largely transparent following longterm diabetes. These results indicate that AKR1B1 and AKR1B10 may have different functional properties in the lens and suggest that AKR1B10 does not contribute to the pathogenesis of diabetic cataract in humans

Status of B-Vitamins and Homocysteine in Diabetic Retinopathy: Association with Vitamin-B12 Deficiency and Hyperhomocysteinemia

Diabetic retinopathy (DR) is a common cause of blindness. Although many studies have indicated an association between homocysteine and DR, the results so far have been equivocal. Amongst the many determinants of homocysteine, B-vitamin status was shown to be a major confounding factor, yet very little is known about its relationship to DR. In the present study, we, therefore, investigated the status of B-vitamins and homocysteine in DR. A cross-sectional case–control study was conducted with 100 normal control (CN) subjects and 300 subjects with type-2 diabetes (T2D). Of the 300 subjects with T2D, 200 had retinopathy (DR) and 100 did not (DNR). After a complete ophthalmic examination including fundus fluorescein angiography, the clinical profile and the blood levels of all B-vitamins and homocysteine were analyzed. While mean plasma homocysteine levels were found to be higher in T2D patients compared with CN subjects, homocysteine levels were particularly high in the DR group. There were no group differences in the blood levels of vitamins B1 and B2. Although the plasma vitamin-B6 and folic acid levels were significantly lower in the DNR and DR groups compared with the CN group, there were no significant differences between the diabetes groups. Interestingly, plasma vitamin-B12 levels were found to be significantly lower in the diabetes groups compared with the CN group; further, the levels were significantly lower in the DR group compared with the DNR group. Higher homocysteine levels were significantly associated with lower vitamin-B12 and folic acid but not with other B-vitamins. Additionally, hyperhomocysteinemia and vitamin-B12 deficiency did not seem to be related to subjects' age, body mass index, or duration of diabetes. These results thus suggest a possible association between vitamin-B12 deficiency and hyperhomocysteinemia in DR. Further, the data indicate that vitamin-B12 deficiency could be an independent risk factor for DR

Response of Small Heat Shock Proteins in Diabetic Rat Retina

PURPOSE. Small heat shock proteins (sHsps) have a critical role under stress conditions to maintain cellular homeostasis by their involvement in protein-folding and cytoprotection. The hyperglycemia in diabetes may impose cellular stress on the retina. Therefore, we investigated the expression of sHsps, phosphoregulation of aB-crystallin (aBC), and their localization in the diabetic rat retina. METHODS. Diabetes was induced in rats and maintained on hyperglycemia for a period of 12 weeks. The expression of sHsps, HSFs, and phosphorylated sHsps was analyzed by quantitative (q) RT-PCR and immunoblotting. The solubility of sHsps was analyzed by detergent solubility assay. Cellular localization of sHsps and phosphorylated aBCs was examined by immunohistochemistry. RESULTS. Of 10 sHsps, five sHsps were detected in the rat retina. Among those, increased expression for aA-crystallin (aAC), aBC, and Hsp22, and decreased expression for Hsp20 were seen in the diabetic retina, whereas Hsp27 mRNA levels were increased, while protein levels were decreased. While the expression of HSFs was either unaltered or decreased, expression of hypoxia inducible factor-1a (HIF-1a) was increased in the diabetic retina. The phosphorylation of aBC at Ser45 and Ser19 was increased in the retina of diabetic rats. However, phosphorylation of aBC at Ser59 was decreased in the soluble fraction with a concomitant increase in the insoluble fraction. Moreover, diabetes activated the p38MAPK signaling cascade by increasing the p-p38 MAPK in the retina. Further, diabetes induced the aggregation of Hsp27, aAC, aBC, and pS59-aBC in the retina. A strong immunoreactivity of Hsp27, aAC, aBC, and phosphorylated aBC was localized in different retinal layers of diabetic rats. CONCLUSIONS. The results indicate an upregulation of aAC, aBC, and Hsp22, but their solubility was compromised in the diabetic retina. There was increased phosphorylation at Ser59, Ser45, and Ser19 of aBC under diabetic conditions. Localization of sHsps and their phosphorylated forms was dispersed to many layers of the retina in diabetes. These results suggest that sHsps may be protecting the retinal neurons in chronic diabetes

Garlic ameliorates long-term pre-diabetes induced retinal abnormalities in high fructose fed rat model

452-460Retinopathy is one of the micro vascular complications of diabetes and can also be observed in pre-diabetic state. However, there are only limited studies available on the pathophysiology of retinopathy in pre-diabetic state and its preventive strategies. In this study, we investigated the retinal functional, structural and molecular alterations using high fructose (HF) induced pre-diabetic rat model and also the protective role of garlic. Feeding of HF to Wistar NIN (WNIN) rats had developed insulin resistance (IR) and impaired glucose tolerance (IGT) by three months, while retinal functional abnormalities by ten months as evidenced by decrease of Electroretinogram (ERG) scotopic, photopic b-wave amplitudes, oscillatory potentials (OPs) when compared to controls. Supplementation of garlic (3%) to HF+G group rats had marginally protected these changes. Elevated expression of glial fibrillary acidic protein (GFAP), vascular endothelial growth factor (VEGF), aldose reductase (AR) and decreased rhodopsin (Rho) in HF group rats as evidenced by immunehistochemistry, immunoblot methods, which were further supported by gene expression studies, indicate the initiation of retinal abnormalities. Increased immune-fluorescence signal of carboxymethyl lysine (CML-KLH) and 4-hydroxynanoenol (4-HNE) in retina of HF group rats indicate the association of glycation and oxidative stress, respectively. Early intervention of garlic to HF+G group rats attenuated retinal functional, structural, and molecular abnormalities

Effect of curcumin on galactose-induced cataractogenesis in rats

Purpose: Curcumin, the active principle of turmeric, has been shown to have both antioxidant and hypoglycemic activity in vitro and in vivo. The purpose of this study was to investigate the effect of curcumin on the onset and maturation of galactose induced cataract. Methods: Sprague-Dawley rats (21 days old) were divided into 5 groups. The control group (A) received an AIN-93 diet, the galactose group (B) received 30% galactose in the diet, the test groups (C and D) received the B group diet plus 0.002% and 0.01% curcumin respectively, and group (E) received the control diet plus 0.01% curcumin, all for a period of 4 weeks. Cataract progression due to galactose feeding was monitored by slit lamp microscope and classified into 4 stages. At the end of the experiment biochemical parameters such as lipid peroxidation, aldose reductase (AR), sorbitol dehydrogenase (SDH), reduced glutathione, protein content, and protein carbonyls were measured in the lens. Advanced glycated end products (AGE) and protein oxidation were measured by AGE and tryptophon fluorescence respectively. Crystallin profile was analyzed by size exclusion chromatography (HPLC). Results: Slit lamp microscope observations indicated that curcumin at 0.002% (group C) delayed the onset and maturation of cataract. In contrast even though there was a slight delay in the onset of cataract at the 0.01% level (group D), maturation of cataract was faster when compared to group B. Biochemical analysis showed that curcumin at the 0.002% level appeared to exert antioxidant and antiglycating effects, as it inhibited lipid peroxidation, AGE-fluorescence, and protein aggregation. Though the reasons for faster onset and maturation of cataract in group D rats was not clear, the data suggested that under hyperglycemic conditions higher levels of curcumin (0.01%) in the diet may increase oxidative stress, AGE formation, and protein aggregation. However, feeding of curcumin to normal rats up to a 0.01% level did not result in any changes in lens morphology or biochemical parameters. Conclusions: These results suggest that curcumin is effective against galactose-induced cataract only at very low amounts (0.002%) in the diet. On the other hand at and above a 0.01% level curcumin seems to not be beneficial under hyperglycemic conditions, at least with the model of galactose-cataract

A Preliminary Study on Prevalence of Non-Communicable Diseases and their Association with Physical activity among the Urban Geriatric Population

Background: India is experiencing a rapid health transition with a rising burden of Non-Communicable Diseases (NCDs) and inappropriate lifestyle is the most remarkable risk factor associated to NCDs. Aims & Objectives: To assess the prevalence of NCDs and their association with physical activity among urban elderly. Material and methods: A community based cross-sectional study was conducted among 112 geriatric population (≥60 years) in cities of Hyderabad and Secunderabad. The data on medical history, lifestyle, diet and physical activity was obtained using a pre-tested questionnaire. Anthropometric measurements such as weight, height and waist circumference were measured. Intravenous blood samples were collected to estimate the biochemical parameters. Result:  About 64.3 % of elderly have been practicing physical activity i.e. predominantly walking, while 35.7% were sedentary. The prevalence of hypertension (87.5%), diabetes (65.3%), central obesity (77.8%) and metabolic syndrome (59.7%) was higher among walkers as compared to non-walkers and the prevalence of metabolic syndrome was significantly (p<0.005) high among the elderly suffering from Cardio Vascular Diseases (CVDs). Conclusion: In general, the prevalence of non-communicable diseases was high among urban geriatric population. Therefore, primordial and primary preventive measures should be adopted during adolescence and early adulthood for the prevention and control of NCDs

Efficacy of biodegradable curcumin nanoparticles in delaying cataract in diabetic rat model

Curcumin, the active principle present in the yellow spice turmeric, has been shown to exhibit various pharmacological actions such as antioxidant, anti-inflammatory, antimicrobial, and anti-carcinogenic activities. Previously we have reported that dietary curcumin delays diabetes-induced cataract in rats. However, low peroral bioavailability is a major limiting factor for the success of clinical utilization of curcumin. In this study, we have administered curcumin encapsulated nanoparticles in streptozotocin (STZ) induced diabetic cataract model. Oral administration of 2 mg/day nanocurcumin was significantly more effective than curcumin in delaying diabetic cataracts in rats. The significant delay in progression of diabetic cataract by nanocurcumin is attributed to its ability to intervene the biochemical pathways of disease progression such as protein insolubilization, polyol pathway, protein glycation, crystallin distribution and oxidative stress. The enhanced performance of nanocurcumin can be attributed probably to its improved oral bioavailability. Together, the results of the present study demonstrate the potential of nanocurcumin in managing diabetic cataract