Correlation of blood-glucose control with oxidative metabolites in plasma and vitreous body of diabetic patients

Current concepts of pharmacotherapy of diabetic macular edema

Introduction: Diabetic macular edema (DME) is a sight threatening disease and a major cause for blindness for people in working age. The pathogenesis is multifactorial and complex. The pharmacotherapy of DME addresses both the inhibition of vascular endothelial growth factor (VEGF) by the intravitreal injection of VEGF inhibitors and inflammatory processes by the intravitreal application of steroids. Several trials have been published reporting on the efficacy and safety of these treatments.Areas covered: This review discusses original research articles including basic science and clinical studies as well as review articles focusing on the role of inflammation and VEGF expression in DME. It discusses newly published clinical trials on intravitreal pharmacotherapy for DME. The literature was searched using Medline/PubMed and was selected given its relevance for the topic to be discussed.Expert opinion: Our knowledge regarding the pathophysiology of diabetic macular edema has significantly increased. Some of these insights have been successfully transferred into current treatment strategies already including VEGF suppression or anti-inflammatory treatments using steroids. The identification of additional pathophysiological aspects and their relevance as potential treatment targets will be a future challenge in the treatment of DME. A better knowledge on the complex pathophysiology will also help to establish combination strategies.

Serum Lycopene Levels in Patients with Diabetic Retinopathy

Purpose.

Accumulating evidence indicates that oxidative stress may play an important role in the pathogenesis of type 2 diabetes and its complications. Lycopene, a very potent antioxidant of carotenoids, has received considerable scientific interest in recent years for its potential role in the prevention of oxidative stress-related chronic diseases. This study was undertaken to investigate whether the serum levels of lycopene are altered between type 2 diabetic patients with and without diabetic retinopathy.

Methods.

A total of 71 patients with type 2 diabetes were analyzed and compared with 23 nondiabetic healthy controls. Serum lycopene concentrations were assayed using high-performance liquid chromatography.

Results.

Lycopene level was found to be significantly lower in diabetic patients than in controls (p=0.021). In the diabetic group, subjects with proliferative diabetic retinopathy had significantly lower lycopene levels than subjects without diabetic retinopathy or with nonproliferative diabetic retinopathy. In the analysis of correlations, hemoglobin A1c were negatively correlated with lycopene (r=–0.345, p=0.007) after multivariate adjustment. A stepwise linear multiple regression model revealed that age and hemoglobin A1c were significant determinants of lycopene.

Conclusions.

Our findings show that measuring serum lycopene is a novel convenient method for evaluating oxidative damage. Diabetic patients, especially those with advanced diabetic retinopathy, had significantly lower serum lycopene levels; this suggests that lycopene may be helpful for the diagnosis, severity, and therapeutic evaluation of diabetic retinopathy.

A 5-year follow-up of antioxidant supplementation in type 2 diabetic retinopathy

PURPOSE

This study was designed to evaluate the effect of antioxidant supplementation on diabetic retinopathy (DR) over a 5-year follow-up period. To our knowledge, this is the first such clinical trial performed.

METHODS

We recruited 105 type 2 diabetic patients with nonproliferative DR. A complete ophthalmic checkup and a plasma determination of oxidative (malonyldialdehyde [MDA]) and antioxidant parameters (total antioxidant status [TAS]) were obtained as the baseline. One part of the cohort was randomly assigned to oral antioxidant supplementation at nutritional doses. The same examinations were performed with 97 diabetic patients who completed the 5-year follow-up period. The best-corrected visual acuity, DR score, MDA, and TAS values were compared at the beginning and the end of the follow-up.

RESULTS

Best-corrected visual acuity did not change during the follow-up, irrespective of supplementation. However, the retinopathy stage showed a retardation of progression in the subgroup with supplementation, but worsened in the subgroup with no antioxidant supplementation. Furthermore, the antioxidant supplementation group maintained its antioxidant plasma status levels, which was related to decreased oxidative plasma activity.

CONCLUSIONS

Oral antioxidant supplementation could be a useful adjunctive long-term therapy in the treatment of nonproliferative DR.

Urinary 8-hydroxydeoxyguanosine levels in diabetic retinopathy patients

PURPOSE

Involvement of oxidative stress in the pathogenesis of diabetic microvascular complications has been proposed. Recently, 8-hydroxy-2'-deoxyguanosine (8-OHdG) has been reported to serve as a new sensitive biomarker of the oxidative DNA damage in vivo. This study was undertaken to investigate whether the urinary levels of 8-OHdG are altered in patients with type 2 diabetes. The authors also attempted to analyze the relationship between 8-OHdG levels and other clinical parameters of patients with diabetes, especially the relationship between oxidative DNA damage and the severity of the retinal lesions in patients with diabetic retinopathy.

METHODS

The authors studied 60 patients with type 2 diabetes and compared them with 35 nondiabetic control subjects. Urinary 8-OHdG concentrations were assayed using competitive enzymelinked immunosorbent assay.

RESULTS

The patients with type 2 diabetes had significantly higher concentrations of 8-OHdG in their urine than the control subjects (19.6+/-6.7 vs 11.9+/-4.9 ng/mgCr; p<0.05). The authors could not find any correlation between urinary 8-OHdG levels and age, duration of diabetes, or serum lipids. However, HbA1c values were significantly correlated with 8-OHdG values. Among the patients with diabetes, those with proliferative retinopathy had significantly higher 8-OHdG levels than those with nonproliferative retinopathy or without retinopathy.

CONCLUSIONS

The authors' findings show that measuring urinary 8-OHdG is a novel convenient method for evaluating oxidative DNA damage in patients with diabetes, and it is also suggested that 8-OHdG could be a sensitive biomarker and may be helpful for the early diagnosis and treatment of patients with diabetic retinopathy.

Comparisons between the beneficial effects of different sulphonylurea treatments on ischemia-induced retinal neovascularization

The aim of this study was to assess the potential beneficial effects of gliclazide and other sulphonylureas on ischemia-induced retinal neovascularization. To produce an animal model of oxygen-induced ischemic retinopathy, 7-day-old (P7) mice were exposed to a 75% oxygen environment for 5 days. On their return to ambient air at P12, these mice were then treated with gliclazide, glibenclamide, glimepiride, or N-acetylcysteine. Gliclazide, but not glibenclamide or glimepiride, markedly suppresses retinal neovascularization. N-Acetylcysteine, however, only moderately suppresses retinal neovascularization. The number of neovascular nuclei in the retinal cross sections decreased by 29% in the gliclazide-treated mice (P<0.05 vs control). The induction of VEGF mRNA expression at P13 is significantly suppressed in the gliclazide group, relative to the control group (-44%, P<0.05). The VEGF protein expression levels at P15 were also suppressed in the gliclazide group (-43%, P<0.01). The 8-isoprostane production levels at P15 were suppressed in both the gliclazide group (-20%, P<0.05) and the N-acetylcysteine-treated group (-31%, P<0.01). Gliclazide inhibits ischemia-induced retinal neovascularization, and this is likely to be mediated in part through the downregulation of VEGF and the suppression of oxidative stress.

[Accumulation of lipid particles in Bruch's membrane of LDL receptor knockout mice as a model of age-related macular degeneration]

BACKGROUND

Atherosclerosis is a suspected risk factor for the development of neovascular age-related macular degeneration (AMD).

METHODS

We used a well-established murine knockout model with low-density lipoprotein (LDL) receptor deficiency for atherosclerotic vascular pathogenesis to evaluate changes in Bruch's membrane due to high cholesterol levels. Blood cholesterol levels were modified by the diet fed (standard rodent diet or high-fat diet western type). Animals were sacrificed and plasma cholesterol levels were determined. Eyes were examined by transmission electron microscopy (TEM).

RESULTS

Plasma total cholesterol levels were highest in LDL receptor-deficient mice after high-fat diet and elevated in LDL receptor-deficient mice after standard diet compared to control mice with and without special high-fat diet. While Bruch's membranes of control animals did not exhibit any visible changes by TEM even after a high-fat diet, membrane-bound translucent particles were seen in all membranes in knockout mice. The amount of these particles was substantially increased and membranes were thickened in knockout animals following high-fat diet with additional deposits of non-membrane-bound particles.

CONCLUSION

LDL receptor-deficient mice exhibited a degeneration of Bruch's membrane with accumulation of lipid particles, which is further increased after fat intake due to elevated blood lipid levels. In our opinion, this animal model is suitable for investigating more aspects in the pathogenesis of neovascular AMD.

Urinary 8-OHdG: a marker of oxidative stress to DNA and a risk factor for cancer, atherosclerosis and diabetics

Reactive oxygen species (ROS) produced either endogenously or exogenously can attack lipid, protein and nucleic acid simultaneously in the living cells. In nuclear and mitochondrial DNA, 8-hydroxydeoxyguanosine (8-OHdG), an oxidized nucleoside of DNA, is the most frequently detected and studied DNA lesion. Upon DNA repair, 8-OHdG is excreted in the urine. Numerous evidences have indicated that urinary 8-OHdG not only is a biomarker of generalized, cellular oxidative stress but might also be a risk factor for cancer, atherosclerosis and diabetes. For example, elevated level of urinary 8-OHdG has been detected in patients with various cancers. In human atherosclerotic plaques, there were increased amounts of oxidatively modified DNA and 8-OHdG. Elevated urinary 8-OHdG and leukocyte DNA were also detected in diabetic patients with hyperglycemia, and the level of urinary 8-OHdG in diabetes correlated with the severity of diabetic nephropathy and retinopathy. We have discussed various methods for determining 8-OHdG in the tissue and urine, including HPLC with and without extraction, and ELISA. Using the ELISA we developed, we found that the normal range of urinary 8-OHdG for females was 43.9 +/- 42.1 ng/mg creatinine and 29.6 +/- 24.5 ng/mg creatinine for males, respectively. We found that the normal value between females and males is significantly different (p < 0.001).