Possible involvement of nitric oxide in the progression of diabetic retinopathy

TOWARDS A TREATMENT FOR DIABETIC RETINOPATHY: Intravitreal Toxicity and Preclinical Safety Evaluation of Inducible Nitric Oxide Synthase Inhibitors

BACKGROUND

The purpose of this study is to determine the maximum tolerated dose of a single intravitreal injection of aminoguanidine and 1400W, 2 inhibitors of inducible nitric oxide synthase, in rabbit eyes. Inhibition of inducible nitric oxide synthase has already been shown to be beneficial in various animal models of diabetic eye disease.

METHODS

Groups of 4 New Zealand white rabbits were injected with balanced salt solution in the right eye and a single dose of either aminoguanidine (5, 1, 0.25 mg) or 1400W (2 mg and 0.4 mg) in the left eye. Toxicity was assessed by slit-lamp and fundus examination, intraocular pressure and pachymetric measurements, and electrophysiologic and histologic analysis.

RESULTS

Eyes injected with high doses of aminoguanidine (5 mg) or 1400W (2 mg) demonstrated severe retinal vascular attenuation and infarction. Lower doses of intravitreal aminoguanidine (1 mg) and 1400W (0.4 mg) caused no significant toxic ocular effects in rabbit eyes.

CONCLUSION

If the difference in vitreal volume between rabbit eyes and human eyes is taken into account, aminoguanidine (2.7 mg) and 1400W (1 mg) would be reasonable intravitreal doses to test for safety and efficacy in early clinical trials.

Study of Lipid Peroxidation, Nitric Oxide End Product, and Trace Element Status in Type 2 Diabetes Mellitus with and without Complications

BACKGROUND

Oxidative stress has become a real entity in etiopathogenesis of Type 2 diabetes mellitus (DM). It may result from steady flux of free radicals and lipid peroxides in vivo. Malondialdehyde (MDA) is a stable end product of lipid peroxidation. Accumulative evidences suggest that hyperglycemia in Type 2 DM can produce major changes in nitric oxide (NO) production as well as in its action. Alteration in metabolism of trace elements is also observed in DM.

OBJECTIVE

To evaluate oxidative stress, status of NO, and trace elements zinc (Zn) and magnesium (Mg) in type 2 DM and to correlate these parameters with disease process.

MATERIALS AND METHODS

Ninety-two cases with diabetes were included in the study, out of which 51 were type 2 DM without any complication and 41 were type 2 DM with complications. Fifty-one nondiabetic healthy controls from hospital staff were selected for the study. Blood samples were collected after an overnight fast for estimation of fasting plasma glucose, postprandial glucose, glycated hemoglobin (HbA1c), lipid profile, trace element status, MDA, and NO.

RESULTS

Study revealed a rise in MDA levels in both uncomplicated and complicated cases with diabetes (2.47 ± 0.53, 3.98 ± 0.42 nmol/ml, respectively) as compared to controls (1.43 ± 0.23 nmol/ml), which was statistically significant (P < 0.05). The mean levels of NO, Zn, and Mg were significantly lower in both the diabetic groups than the control group (P < 0.05). MDA showed a significant positive correlation with plasma glucose, lipid profile parameters (except high-density lipoprotein cholesterol), and significant negative correlation with Zn (r = -0.44, P < 0.05) and Mg (r = -0.31, P < 0.05). NO levels were correlated significantly with plasma glucose, dyslipidemia, and HbA1c (P < 0.05). The effects of glycemic status on trace element concentrations were evident from a significant negative correlation between Zn and Mg with fasting plasma glucose and HbA1c.

CONCLUSION

Findings of the present study may establish the role of hyperglycemia, oxidative stress, impaired NO, and trace elements in pathogenesis and long-term vascular complications of type 2 DM.

The Role of Retinal Imaging and Portable Screening Devices in Tele-ophthalmology Applications for Diabetic Retinopathy Management

In the years since its introduction, retinal imaging has transformed our capability to visualize the posterior pole of the eye. Increasing practical advances in mobile technology, regular monitoring, and population screening for diabetic retinopathy management offer the opportunity for further development of cost-effective applications through remote assessment of the diabetic eye using portable retinal cameras, smart-phone-based devices and telemedicine networks. Numerous retinal imaging methods and mobile technologies in tele-ophthalmology applications have been reported for diabetic retinopathy screening and management. They provide several advantages of automation, sensitivity, specificity, portability, and miniaturization for the development of point-of-care diagnostics for eye complications in diabetes. The aim of this paper is to review the role of retinal imaging and mobile technologies in tele-ophthalmology applications for diabetic retinopathy screening and management. At large, although improvements in current technology and telemedicine services are still needed, telemedicine has demonstrated to be a worthy tool to support health caregivers in the effective management and prevention of diabetes and its complications.

The Extract of Aster Koraiensis Prevents Retinal Pericyte Apoptosis in Diabetic Rats and Its Active Compound, Chlorogenic Acid Inhibits AGE Formation and AGE/RAGE Interaction

Retinal capillary cell loss is a hallmark of early diabetic retinal changes. Advanced glycation end products (AGEs) are believed to contribute to retinal microvascular cell loss in diabetic retinopathy. In this study, the protective effects of Aster koraiensis extract (AKE) against damage to retinal vascular cells were investigated in streptozotocin (STZ)-induced diabetic rats. To examine this issue further, AGE accumulation, nuclear factor-kappaB (NF-κB) and inducible nitric oxide synthase (iNOS) were investigated using retinal trypsin digests from streptozotocin-induced diabetic rats. In the diabetic rats, TUNEL (Terminal deoxynucleotidyl transferase mediated dUTP Nick End Labeling)-positive retinal microvascular cells were markedly increased. Immunohistochemical studies revealed that AGEs were accumulated within the retinal microvascular cells, and this accumulation paralleled the activation of NF-κB and the expression of iNOS in the diabetic rats. However, AKE prevented retinal microvascular cell apoptosis through the inhibition of AGE accumulation and NF-κB activation. Moreover, to determine the active compounds of AKE, two major compounds, chlorogenic acid and 3,5-di-O-caffeoylquinic acid, were tested in an in vitro assay. Among these compounds, chlorogenic acid significantly reduced AGE formation as well as AGE/RAGE (receptor for AGEs) binding activity. These results suggest that AKE, particularly chlorogenic acid, is useful in inhibiting AGE accumulation in retinal vessels and exerts a preventive effect against the injuries of diabetic retinal vascular cells.

Comparison of Aqueous Humor Nitric Oxide Levels After Different Corneal Collagen Cross-Linking Methods

PURPOSE

Nitric oxide production can cause either apoptotic or necrotic cell death through oxidative stress. We aimed to investigate the nitrite oxide metabolites (NO_x) and nitrite levels in the aqueous humor of rabbit eyes after different methods of corneal collagen cross-linking (CXL).

MATERIALS AND METHODS

Twenty-four eyes of 12 adult New Zealand rabbits were used. They were assigned into four groups, each including six eyes. Group 1 (control) consisted of eyes with no treatment. Group 2 received UV-A power setting at 3 mW/cm² for 30 minutes of continuous exposure and named as standard CXL group. Group 3 received UV-A power setting at 30 mW/cm² for 3 minutes of continuous exposure and named as accelerated CXL (A-CXL) group. Group 4 received UV-A power setting at 30 mW/cm² for 6 minutes of pulsed exposure (1 sec on, 1 sec off) and named as pulse-light accelerated CXL (PLA-CXL). Aqueous humors were aspirated from anterior chamber with a 27G needle after 1 hour UV-A exposure. NO_x and nitrite levels were measured Results: The nitrite levels in aqueous humor were significantly increased in Group 2 and Group 3 when compared with Group 1 (p = 0.000, p = 0.036, respectively). When treatment modalities were compared with each other, high nitrite level in Group 2 was statistically significant when compared with Group 4 (p = 0.019). NO_x levels were higher in Group 2 when compared with Group 1 (p = 0.006).

CONCLUSIONS

Numerous studies investigated the physiological and pathophysiological roles of NO. NO is considered one of the most important molecule for ocular health. According to NO_x level in aqueous humor, it seems that PLA-CXL is the safest method due to the similar results with control group.

Association between a 27-bp variable number of tandem repeat polymorphism in intron 4 of the eNOS gene and risk for diabetic retinopathy Type 2 diabetes mellitus: a meta-analysis

PURPOSE

Imbalance in the production of endothelial nitric oxide synthase (eNOS), which plays an essential role in retinal vascular function, can lead to the development of diabetic retinopathy (DR). To thoroughly address this issue, we performed an updated meta-analysis to evaluate the association between the eNOS 27VNTR (4b/4a) polymorphism and DR in type 2 diabetes mellitus (T2DM).

METHODS

A search was conducted of PubMed and Chinese language (WanFang) databases through 3 March 2013. Data were retrieved in a systematic manner and analyzed using Stata Statistical Software. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations.

RESULTS

Based on the search criteria for DR susceptibility related to the 27VNTR (4b/4a) polymorphism of the eNOS gene, 16 case-control studies (15 articles), comprising 3227 T2DM patients with DR and 3437 T2DM patients without DR, were retrieved. Although no significant associations were uncovered in either the overall analysis or DR subtype groups, a decreased association was detected between the African- (allelic contrast: OR = 0.75, 95% CI = 0.65-0.88) or population-based (PB) studies (dominant genetic model: OR = 0.91, 95% CI = 0.83-0.98) and the eNOS 27VNTR (4b/4a) polymorphism. Stratification according to average duration of DM revealed that T2DM patients with histories of >10 years had an elevated susceptibility to DR compared with those with histories of shorter durations (homozygote comparison: OR = 1.67, 95% CI = 1.09-2.58).

CONCLUSIONS

The present meta-analysis suggests that the eNOS 27VNTR (4b/4a) polymorphism potentially decreases the risk of developing DR in T2DM African individuals. The higher degree of susceptibility in patients with longer (>10 years) durations of DM is indicative of the involvement of a gene-environment interaction in determining the risk for DR. Further studies, based on larger sample sizes and additional gene-environment interactions, should be conducted to elucidate the role of eNOS gene polymorphisms, especially 27VNTR (4b/4a), in the risk for DR.

Effects of Phyllanthus emblica extract on endothelial dysfunction and biomarkers of oxidative stress in patients with type 2 diabetes mellitus: a randomized, double-blind, controlled study

BACKGROUND

It has been reported that hyperglycemia can induce endothelial dysfunction via increased oxidative stress and that it plays a central role in the development of atherosclerosis and coronary heart disease. Phyllanthus emblica (Emblica officinalis, amla) is known for its antioxidant and antihyperlipidemic activity. The present study compared the effects of an aqueous extract of P. emblica (highly standardized by high-performance liquid chromatography to contain low molecular weight hydrolyzable tannins, ie, emblicanin A, emblicanin B, pedunculagin, and punigluconin) versus those of atorvastatin and placebo on endothelial dysfunction and biomarkers of oxidative stress in patients with type 2 diabetes.

METHODS

Eligible patients were randomized to receive either P. emblica 250 mg twice daily, P. emblica 500 mg twice daily, atorvastatin 10 mg in the evening and matching placebo in the morning, or placebo twice daily for 12 weeks. The primary efficacy parameter was the change in endothelial function identified on salbutamol challenge at baseline and after 12 weeks of treatment. Secondary efficacy parameters were changes in biomarkers of oxidative stress (malondialdehyde, nitric oxide, and glutathione), high sensitivity C-reactive protein levels, the lipid profile, and glycosylated hemoglobin (HbA1c) levels. Laboratory safety parameters were measured at baseline and after 12 weeks of treatment.

RESULTS

Eighty patients completed the study. Treatment with P. emblica 250 mg, P. emblica 500 mg, or atorvastatin 10 mg produced significant reductions in the reflection index (-2.25%±1.37% to -9.13%±2.56% versus -2.11%±0.98% to -10.04%±0.92% versus -2.68%±1.13% to -11.03%±3.93%, respectively), suggesting improvement in endothelial function after 12 weeks of treatment compared with baseline. There was a significant improvement in biomarkers of oxidative stress and systemic inflammation compared with baseline and placebo. Further, the treatments significantly improved the lipid profile and HbA1c levels compared with baseline and placebo. All treatments were well tolerated.

CONCLUSION

Both atorvastatin and P. emblica significantly improved endothelial function and reduced biomarkers of oxidative stress and systemic inflammation in patients with type 2 diabetes mellitus, without any significant changes in laboratory safety parameters.

Estimation of nitric oxide as an inflammatory marker in periodontitis

Nitric oxide (NO) is not only important in host defense and homeostasis but it is also regarded as harmful and has been implicated in the pathogenesis of a wide variety of inflammatory and autoimmune diseases. The presence of NO in periodontal disease may reflect the participation of an additional mediator of bone resorption responsible for disease progression. The aim of this study was to assess the level of NO in serum in chronic periodontitis, and correlate these levels with the severity of periodontal disease. Sixty subjects participated in the study and were divided into two groups. NO levels were assayed by measuring the accumulation of stable oxidative metabolite, nitrite with Griess reaction. Results showed subjects with periodontitis had significantly high nitrite in serum than healthy subjects. NO production is increased in periodontal disease, this will enable us to understand its role in disease progression and selective inhibition of NO may be of therapeutic utility in limiting the progression of periodontitis.

Serum nitric oxide status in patients with type 2 diabetes mellitus in Sikkim

BACKGROUND

Serum nitric oxide (NO) has emerged as a fundamental signal associated with the endothelial dysfunction in type 2 diabetes.

AIMS

To compare serum nitric oxide level among type 2 diabetic patients along with other biochemical parameters and to compare it with that of normal population in Sikkim.

SETTINGS AND DESIGN

This prospective study was carried out in the Biochemistry Department in a tertiary care teaching hospital in Sikkim on 50 type 2 diabetics compared to 100 non-diabetics.

MATERIALS AND METHODS

The un-hemolyzed blood sample was collected for estimation of biochemical parameters. Griess reaction was used for indirect assay of stable decomposition products in serum(serum nitrite and nitrate levels) as an index of NO generation. The comparison of different parameters between cases and control was done by using Student's t-test.

RESULTS

There was significant difference when age- and sex-matched cases and controls were compared in regard to waist circumference and body mass index. The values of fasting and postprandial serum glucose, and lipid profile between study group and control group differed significantly. The mean serum level of NO in the study and control group was 43.83 ± 11.3 μmoles/L and 58.85 ± 12.8 μmoles/L respectively, and this difference was statistically significant.

CONCLUSION

To sum up, serum NO was observed significantly low in diabetic participants as compared to control, along with difference in other biochemical parameters.

KIOM-79 Prevents Lens Epithelial Cell Apoptosis and Lens Opacification in Zucker Diabetic Fatty Rats

Damage of lens epithelial cells (LECs) has been implicated in cataract formation. The aim of this study was to investigate the protective effect of KIOM-79, a combination of four plant extracts, on LECs. We examined the levels of advanced glycation end products (AGEs), nuclear factor-kappaB (NF-κB) activation and inducible nitric oxide synthase (iNOS) expression in LECs during cataract development using the Zucker diabetic fatty (ZDF) rat, an animal model of type 2 diabetes. KIOM-79 was orally administered by gavage to ZDF rats once a day for 13 weeks. Apoptosis was detected by TUNEL assay, and NF-κB activation and iNOS expression were studied by southwestern histochemistry and immunohistochemistry, respectively. In diabetic cataractous lenses, TUNEL-positive LECs were markedly increased 20-fold, and AGEs were highly accumulated (2.7-fold) in LECs. In addition, both NF-κB activation, and iNOS expression were significantly enhanced 3- to 5-fold, respectively, compared to levels found in normal ZL rats. However, the administration of KIOM-79 delayed the development of diabetic cataracts and prevented LEC apoptosis (70%) through the inhibition of AGEs, NF-κB-activation and iNOS expression. These observations suggest that KIOM-79 is useful in inhibiting diabetic cataractogenesis and acts through an antiapoptotic mechanism to protect LECs from injury.

Cytotoxic role of methylglyoxal in rat retinal pericytes: Involvement of a nuclear factor-kappaB and inducible nitric oxide synthase pathway

Methylglyoxal (MGO), a cytotoxic metabolite, is produced from glycolysis. Elevated levels of MGO are observed in a number of diabetic complications, including retinopathy, nephropathy and cardiomyopathy. Loss of retinal pericyte, a hallmark of early diabetic retinal changes, leads to the development of formation of microaneurysms, retinal hemorrhages and neovasculization. Herein, we evaluated the cytotoxic role of MGO in retinal pericytes and further investigated the signaling pathway leading to cell death. Rat primary retinal pericytes were exposed to 400muM MGO for 6h. Retinal vessels were prepared from intravitreally MGO-injected rat eyes. We demonstrated apoptosis, nuclear factor-kappaB (NF-kappaB) activation and inducible nitric oxide synthase (iNOS) induction in cultured pericytes treated with MGO and MGO-injected retinal vessels. In MGO-treated pericytes, TUNEL-positive nuclei were markedly increased, and NF-kappaB was translocalized into the nuclei of pericytes, which paralleled the expression of iNOS. The treatment of pyrrolidine dithiocarbamate (an NF-kappaB inhibitor) or l-N6-(1-iminoethyl)-lysine (an iNOS inhibitor) prevented apoptosis of MGO-treated pericytes. In addition, in intravitreally MGO-injected rat eyes, TUNEL and caspase-3-positive pericytes were significantly increased, and activated NF-kappaB and iNOS were highly expressed. These results suggest that the increased expression of NF-kappaB and iNOS caused by MGO is involved in rat retinal pericyte apoptosis.

Sequence variation in DDAH1 and DDAH2 genes is strongly and additively associated with serum ADMA concentrations in individuals with type 2 diabetes

Background

Asymmetric dimethylarginine (ADMA), present in human serum, is an endogenous inhibitor of nitric oxide synthase and contributes to vascular disease. Dimethylarginine dimethylaminohydrolase (DDAH) is an ADMA degrading enzyme that has two isoforms: DDAHI and DDAHII. We sought to determine whether serum ADMA levels in type 2 diabetes are influenced by common polymorphisms in the DDAH1 and DDAH2 genes.

Methodology/Principal Findings

Relevant clinical parameters were measured and peripheral whole blood obtained for serum and genetic analysis on 343 participants with type 2 diabetes. Serum ADMA concentrations were determined by mass spectroscopy. Twenty six tag SNPs in the DDAH1 and 10 in the DDAH2 gene were genotyped in all subjects and tested for association with serum ADMA levels. Several SNPs and haplotypes in the DDAH genes were strongly associated with ADMA levels. Most significantly in the DDAH1 gene, rs669173 (p = 2.96×10⁻⁷), rs7521189 (p = 6.40×10⁻⁷), rs2474123 (p = 0.00082) and rs13373844 (p = 0.00027), and in the DDAH2 gene, rs3131383 (p = 0.0029) and the TGCCCAGGAG haplotype (p = 0.0012) were significantly associated with ADMA levels. Sub-analysis by diabetic retinopathy (DR) status revealed these variants were associated with ADMA levels predominantly in participants without DR. Combined analysis of the most strongly associated SNPs in DDAH1 (rs669173) and DDAH2 (rs3131383) revealed an additive effect (p = 1.37×10⁻⁸) on ADMA levels.

Conclusions/Significance

Genetic variation in the DDAH1 and 2 genes is significantly associated with serum ADMA levels. Further studies are required to determine the pathophysiological significance of elevated serum ADMA in type 2 diabetes and to better understand how DDAH gene variation influences ADMA levels.

Lens epithelial cell apoptosis initiates diabetic cataractogenesis in the Zucker diabetic fatty rat

BACKGROUND

It has been suggested that damage of lens epithelial cell (LEC) may play an important role in cataract formation. Nitric oxide is involved in cataract development. Here, we investigated the relationship between LEC damage and iNOS expression in the Zucker diabetic fatty (ZDF) rat.

METHODS

At 21 weeks of age, the eyes were enucleated and the lens opacity was then examined. Apoptosis were detected by TUNEL assay, and the expression of iNOS and NF-kappaB activation were studied by immunohistochemistry and southwestern histochemistry respectively.

RESULTS

In 21-week-old male ZDF rats, cataract was developed, TUNEL-positive LECs were markedly increased, and the expression levels of iNOS mRNA and protein were significantly upregulated. The expression pattern of iNOS was closely correlated with apoptotic change of LECs. In addition, advanced glycation end products (AGEs) were accumulated in cytoplasm of LECs. Activated NF-kappaB was mainly detected in nucleus of LECs.

CONCLUSIONS

The higher expressions of AGEs, NF-kappaB and iNOS in LECs of diabetic rats suggest that these factors are involved in apoptosis of LEC alterations related to diabetic cataract.

A systematic meta-analysis of genetic association studies for diabetic retinopathy

OBJECTIVE

Diabetic retinopathy is a sight-threatening microvascular complication of diabetes with a complex multifactorial pathogenesis. A systematic meta-analysis was undertaken to collectively assess genetic studies and determine which previously investigated polymorphisms are associated with diabetic retinopathy.

RESEARCH DESIGN AND METHODS

All studies investigating the association of genetic variants with the development of diabetic retinopathy were identified in PubMed and ISI Web of Knowledge. Crude odds ratios (ORs) and 95% CIs were calculated for single nucleotide polymorphisms and microsatellite markers previously investigated in at least two published studies.

RESULTS

Twenty genes and 34 variants have previously been studied in multiple cohorts. The aldose reductase (AKR1B1) gene was found to have the largest number of polymorphisms significantly associated with diabetic retinopathy. The z-2 microsatellite was found to confer risk (OR 2.33 [95% CI 1.49-3.64], P = 2 x 10(-4)) in type 1 and type 2 diabetes and z+2 to confer protection (0.58 [0.36-0.93], P = 0.02) against diabetic retinopathy in type 2 diabetes regardless of ethnicity. The T allele of the AKR1B1 promoter rs759853 variant is also significantly protective against diabetic retinopathy in type 1 diabetes (0.5 [0.35-0.71], P = 1.00 x 10(-4)), regardless of ethnicity. These associations were also found in the white population alone (P < 0.05). Polymorphisms in NOS3, VEGF, ITGA2, and ICAM1 are also associated with diabetic retinopathy after meta-analysis.

CONCLUSIONS

Variations within the AKR1B1 gene are highly significantly associated with diabetic retinopathy development irrespective of ethnicity. Identification of genetic risk factors in diabetic retinopathy will assist in further understanding of this complex and debilitating diabetes complication.

Pathogenesis and classification of proliferative diabetic vitreoretinopathy

PURPOSE

To review the current knowledge regarding the pathogenesis of proliferative diabetic vitreoretinopathy (PDVR) and to present recommendations for its clinical staging.

DESIGN

Focused literature review and authors' clinical experience.

RESULTS

Although several biochemical mediators may be responsible for the pathogenesis of PDVR, no common biochemical pathway exists. Of those mediators, vascular endothelial growth factor is the one most studied so far. However, since in proliferative diabetic retinopathy (PDR) the thickened posterior vitreous cortex is one of the main factors in the development of proliferations, a consequent shrinkage of the posterior vitreous cortex leads to hemorrhages and tractive retinal detachments. Therefore, PDR should be called PDVR. In consequence, the authors present a new morphological classification of PDVR.

CONCLUSIONS

There is no consensus about the biochemical pathway responsible for the progression of PDVR. Although several classifications are described in the literature, the classification suggested here is important in the judgment of, the communication about and the therapy of diabetic retinopathy. Furthermore, it is the only reliable classification for predicting the surgical outcome in diabetics.

Capillary electrophoretic assay for nitrate levels in the vitreous of proliferative diabetic retinopathy

The determination of nitric oxide (NO) in human vitreous samples is complicated by the relatively short half-life of the analyte and the viscous, high salt and protein biological matrix. In this work, we developed a fast (<5min) and useful CE method to determine the stable metabolite, nitrate, from vitreous samples. This proposed method has been successfully applied to determine the nitrate levels from the vitreous humor of patients undergoing vitrectomy for a variety of conditions. A statistically significant increase (P=0.000001) of the mean level of nitrate was observed in vitreous humor of patients with proliferative diabetic retinopathy (41.17+/-4.09microM, n=27) versus controls (15.22+/-0.86microM, n=35). The elevated levels of nitrate in the vitreous of patients known to have diabetic retinopathy suggests that NO is involved with the pathology of this disease.

Proinflammatory and antimicrobial nitric oxide in gingival fluid of diabetic patients with periodontal disease

Abnormal nitric oxide (NO) synthesis has been implicated in the pathogenesis of both periodontal disease and diabetes mellitus. In diabetic patients, increased inducible NO synthase in inflamed gingiva correlated with NO in gingival crevicular fluid. Although increased NO reflected more-severe inflammation, it was associated with reductions in CFU of Prevotella intermedia, a major periodontopathogen, highlighting dual roles for NO.

Different Plasma Levels of Vascular Endothelial Growth Factor and Nitric Oxide between Patients with Choroidal and Retinal Neovascularization

Because the blood flow is much more intense in the choroid than in the retina, it is interesting to explore whether choroidal neovascularization (CNV) is more influenced by plasma angiogenic factors than retinal neovascularization. The aim of this study was to investigate plasma profiles of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in patients with CNV due to age-related macular degeneration (AMD) and in those with retinal neovascularization due to proliferative diabetic retinopathy (PDR). Seventy-seven subjects with AMD, 22 with PDR, and 42 nondiabetic, non-AMD controls were enrolled in this comparative case series. AMD subjects were classified into three groups: dry type (dry AMD, n = 17), wet type with active CNV (CNV/AMD, n = 42), and disciform scar due to advanced wet AMD (scar/AMD, n = 18). Plasma VEGF and NO levels of each subject were measured with enzyme-linked immunosorbent assay and chemiluminescence, respectively. Plasma VEGF level in CNV/AMD (median 256.0 pg/ml, interquartile range 146.4-375.3 pg/ml) was significantly higher than in PDR (124.8 pg/ml, 75.7-215.3 pg/ml; p = 0.004) and controls (120.3 pg/ml, 82.8-168.2 pg/ml, p =0.001). CNV/AMD also had the highest VEGF level among the AMD subgroups. Plasma NO level was significantly elevated in PDR (137.4 microM, 63.7-240.1 microM) when compared with CNV/AMD (71.8 microM, 42.4-113.3 microM; p = 0.004) and controls (62.6 microM, 39.0-114.9 microM; p = 0.002). There was no significant difference in NO levels among the AMD subgroups. No significant correlation between VEGF and NO levels was noted. These findings indicate that both circulating VEGF and NO may play different roles in the pathogenesis of retinal neovascularization and CNV.

The T-786C and C774T endothelial nitric oxide synthase gene polymorphisms independently affect the onset pattern of severe diabetic retinopathy

Genetic factors could be implicated in the pathogenesis of severe diabetic retinopathy (DR). Recently, we reported a strong association between the eNOS4b/a endothelial nitric oxide synthase (eNOS) polymorphism and severe DR. To examine whether T-786C and C774T eNOS polymorphisms are involved in severe DR, 254 Caucasians with longstanding C-peptide-negative type 1 diabetes, 128 patients with absent/mild DR (control group), and 126 patients with preproliferative/proliferative DR (study group) were genotyped. The distribution of T-786C and C774T eNOS polymorphisms was in Hardy-Weinberg equilibrium and did not differ between the study and control groups. However, in case patients (n=126), T-786C and C774T polymorphisms influenced the onset pattern of severe DR (P=0.0169 and P=0.0257, respectively). The C-786C genotype was associated with early-onset severe DR (duration of diabetes: 15.2+/-5.9 vs. 19.4+/-6.3 years, P=0.0105), and the homozygous T774T genotype was associated with late-onset severe DR (24.3+/-7.0 vs. 18.4+/-6.2 years, P=0.0067). In the case of patients with high glycosylated hemoglobin levels (HbA1c >8%, n=88), the association between the T-786C polymorphism and early-onset severe DR was stronger (P=0.0068). Case patients carrying the C-786C genotype had higher HbA1c values (9.61+/-1.89%) than those carrying the T-786T genotype (8.93+/-1.47%, P=0.0173). Multivariate analysis showed that T-786C polymorphism was the best independent factor for onset pattern of severe DR (P<0.001). These findings, supported by previous associations between eNOS4b/a polymorphism and DR, suggest that T-786C and C774T eNOS polymorphisms affect the onset pattern of severe DR.

Génétique des complications du diabète : rétinopathie

Multiple clinical and physiopathological studies as well as genetic analysis, suggest that diabetic retinopathy (DR) is a consequent of interactions between environmental factors, especially hyperglycaemia, and several genetic factors. The genes of aldose reductase (AR), inducible nitric oxide synthase (NOS2A), endothelial nitric oxide synthase (NOS3), vascular endothelial growth factor (VEGF), pigmented epithelium-derived factor (PEDF), protein kinase C-beta (PKC-beta) and receptor for advanced glycation end products (RAGE) implicated in the pathogenesis of DR. The only genetic marker associated with risk of DR in several studies is a microsatellite (A-C)n at 5'end of AR. The synergistic combination of conventional approaches (e.g. candidate gene association studies) with new emerging technologies (e.g. biochips) will be a key factor in the elucidation of the genetic aspects of DR.