Diabetic retinopathy is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients. Hypertens Res. 2009;32:299-305. [PMID: 19262488 DOI: 10.1038/hr.2009.8]

Role of Systemic Factors in Improving the Prognosis of Diabetic Retinal Disease and Predicting Response to Diabetic Retinopathy Treatment

Topic

To review clinical evidence on systemic factors that might be relevant to update diabetic retinal disease (DRD) staging systems, including prediction of DRD onset, progression, and response to treatment.

Clinical relevance

Systemic factors may improve new staging systems for DRD to better assess risk of disease worsening and predict response to therapy.

Methods

The Systemic Health Working Group of the Mary Tyler Moore Vision Initiative reviewed systemic factors individually and in multivariate models for prediction of DRD onset or progression (i.e., prognosis) or response to treatments (prediction).

Results

There was consistent evidence for associations of longer diabetes duration, higher glycosylated hemoglobin (HbA1c), and male sex with DRD onset and progression. There is strong trial evidence for the effect of reducing HbA1c and reducing DRD progression. There is strong evidence that higher blood pressure (BP) is a risk factor for DRD incidence and for progression. Pregnancy has been consistently reported to be associated with worsening of DRD but recent studies reflecting modern care standards are lacking. In studies examining multivariate prognostic models of DRD onset, HbA1c and diabetes duration were consistently retained as significant predictors of DRD onset. There was evidence of associations of BP and sex with DRD onset. In multivariate prognostic models examining DRD progression, retinal measures were consistently found to be a significant predictor of DRD with little evidence of any useful marginal increment in prognostic information with the inclusion of systemic risk factor data apart from retinal image data in multivariate models. For predicting the impact of treatment, although there are small studies that quantify prognostic information based on imaging data alone or systemic factors alone, there are currently no large studies that quantify marginal prognostic information within a multivariate model, including both imaging and systemic factors.

Conclusion

With standard imaging techniques and ways of processing images rapidly evolving, an international network of centers is needed to routinely capture systemic health factors simultaneously to retinal images so that gains in prediction increment may be precisely quantified to determine the usefulness of various health factors in the prognosis of DRD and prediction of response to treatment.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Sarcopenia in a type 2 diabetic state: Reviewing literature on the pathological consequences of oxidative stress and inflammation beyond the neutralizing effect of intracellular antioxidants

Sarcopenia remains one of the major pathological features of type 2 diabetes (T2D), especially in older individuals. This condition describes gradual loss of muscle mass, strength, and function that reduces the overall vitality and fitness, leading to increased hospitalizations and even fatalities to those affected. Preclinical evidence indicates that dysregulated mitochondrial dynamics, together with impaired activity of the NADPH oxidase system, are the major sources of oxidative stress that drive skeletal muscle damage in T2D. While patients with T2D also display relatively higher levels of circulating inflammatory markers in the serum, including high sensitivity-C-reactive protein, interleukin-6, and tumor necrosis factor-α that are independently linked with the deterioration of muscle function and sarcopenia in T2D. In fact, beyond reporting on the pathological consequences of both oxidative stress and inflammation, the current review highlights the importance of strengthening intracellular antioxidant systems to preserve muscle mass, strength, and function in individuals with T2D.

Association of mid-life cerebral small vessel disease with diabetic retinopathy in type 2 diabetes in an Indian population

PURPOSE

Prevalence of cerebral small vessel disease (SVD) in elderly patients with diabetic retinopathy (DR) is higher than in those without DR. We determined the prevalence and severity of SVD in middle-aged patients with DR and compared it with those without DR (NODR) in a subset of the Indian population. We feel this information is critical with evolving trends of an increasing incidence of stroke at younger ages.

METHOD

Institution-based analytical cross-sectional study with 88 middle-aged type 2 diabetes patients; 44 in each group with <10 years diabetes duration, <8% HbA1C value, and with no history of cardiovascular disease. The presence and severity of SVD were determined by magnetic resonance imaging (MRI).

RESULT

Prevalence of SVD was 59.1% among study participants; 70.5% in DR and 47.7% in NODR (p = .03). Significantly increased SVD score (p = .008), high SVD score (p = .030), and white matter hyperintensity (WMH) load (p = .017) were observed in DR compared to NODR. There was no difference in the load of lacune and microbleed. SVD score did not differ according to the severity of DR (p = .395). The location-wise study of MRI revealed a significantly higher SVD load at the centrum semiovale in DR than in NODR (p = .014). We observed a 2.6 times greater chance of SVD (Odds ratio: 2.6, 95% CI 1.1-6.3) and a 9.6 times greater chance of high SVD score (Odds ratio: 9.6, 95% CI 1.1-80.0) in DR compared to NODR.

CONCLUSION

Significantly higher burden of SVD in DR was observed, particularly affecting the centrum semiovale suggesting an association of mid-life SVD with DR in this population.

Association of Generalized and Abdominal Obesity with Diabetic Retinopathy in Chinese Type 2 Diabetic Patients

AIMS

Obesity has been proposed to promote the progression of diabetic retinopathy (DR), but previous studies have not shown consistent results. We aimed to explore the association between generalized and abdominal obesity and DR risk, and to assess the joint effect of these two different types of obesity on DR development.

METHODS

A nested case-control study within a large prospective study on type 2 diabetes was conducted in communities in Huai'an City, Jiangsu Province, China. Cases were individuals who had diagnoses of DR during the 6-year follow-up. A total number of 1544 DR cases and 1:1 matched controls were included. Binomial and multinomial logistic regression models were used to investigate the effects of obesity on DR occurrence and DR severity.

RESULTS

Compared with individuals in the first tertile of the baseline waist-to-hip ratio (WHR), subjects in the third tertile at baseline had significantly higher risk of DR (OR 1.44, 95% CI 1.17-1.78) during the follow-up period. Conversely, body mass index (BMI) (continuous) had an adjusted OR of 0.97 (95% CI 0.95-0.99) of developing DR. Individuals with low BMI and high WHR levels were identified as a high-risk population with a higher likelihood of developing DR (OR 1.65, 95% CI 1.17-2.33) than those in the lowest BMI category and simultaneously in the first WHR tertile.

CONCLUSIONS

Type 2 diabetic individuals with low BMI levels and high WHR levels had a significantly increased risk of developing DR which indicated that isolated abdominal obesity might be involved in the pathogenesis of DR.

Diabetic retinopathy risk in patients with unhealthy lifestyle: A Mendelian randomization study

PURPOSE

This study aimed to investigate the causal association between unhealthy lifestyle factors and diabetic retinopathy (DR) risk and to determine better interventions targeting these modifiable unhealthy factors.

DESIGN

Two-sample Mendelian randomization (MR) analysis was performed in this study. The inverse variance-weighted method was used as the primary method.

METHOD

Our study included 687 single-nucleotide polymorphisms associated with unhealthy lifestyle factors as instrumental variables. Aggregated data on individual-level genetic information were obtained from the corresponding studies and consortia. A total of 292,622,3 cases and 739,241,18 variants from four large consortia (MRC Integrative Epidemiology Unit [MRC-IEU], Genetic Investigation of Anthropometric Traits [GIANT], GWAS & Sequencing Consortium of Alcohol and Nicotine Use [GSCAN], and Neale Lab) were included.

RESULT

In the MR analysis, a higher body mass index (BMI) (odds ratio [OR], 95% confidence interval [CI] = 1.42, 1.30-1.54; P < 0.001] and cigarettes per day (OR, 95% CI = 1.16, 1.05-1.28; P = 0.003) were genetically predicted to be causally associated with an increased risk of DR, while patients with higher hip circumference (HC) had a lower risk of DR (OR, 95% CI = 0.85, 0.76-0.95; P = 0.004). In the analysis of subtypes of DR, the results of BMI and HC were similar to those of DR, whereas cigarettes per day were only related to proliferative DR (PDR) (OR, 95% CI = 1.18, 1.04-1.33; P = 0.009). In the MR-PRESSO analysis, a higher waist-to-hip ratio (WHR) was a risk factor for DR and PDR (OR, 95% CI = 1.24, 1.02-1.50, P = 0.041; OR, 95% CI = 1.32, 1.01-1.73, P = 0.049) after removing the outliers. Furthermore, no pleiotropy was observed in these exposures.

CONCLUSION

Our findings suggest that higher BMI, WHR, and smoking are likely to be causal factors in the development of DR, whereas genetically higher HC is associated with a lower risk of DR, providing insights into a better understanding of the etiology and prevention of DR.

Use of Anthropometric Measures of Obesity to Predict Diabetic Retinopathy in Patients with Type 2 Diabetes in China

PURPOSE

Obesity is an established risk factor for type 2 diabetes (T2D). Diabetic retinopathy (DR) is a major microvascular complication of T2D. In this cross-sectional study, we investigated the association between various anthropometric indices of obesity and DR.

PATIENTS AND METHODS

A representative sample of 1952 patients with T2D participated in this cross-sectional study conducted in Shanghai, China. Anthropometric measures of obesity including weight, height, waist circumference, hip circumference, body mass index (BMI), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were evaluated. The association between WHtR, WHR, and BMI and the presence of DR was examined with logistic regression models.

RESULTS

The prevalence of DR was higher in T2D patients with high WHtR compared to those with normal WHtR (p<0.05). A higher BMI was associated with elevated risk of DR (model 1, p=0.034; model 2, p=0.036). WHR was unrelated to the occurrence of DR (p>0.05).

CONCLUSION

WHtR and BMI but not WHR are risk factors for DR in obese patients with T2D. Patients with high WHtR and BMI should be closely monitored to prevent the development of DR.

Associations between Triglyceride-Glucose Index and Micro- and Macro-angiopathies in Type 2 Diabetes Mellitus

The aim of this study was to investigate the associations between the triglyceride-glucose (TyG) index, a marker of insulin resistance, and microangiopathies and macroangiopathies in patients with type 2 diabetes mellitus (DM). Our study enrolled 1990 type 2 diabetic patients from local hospitals in Taiwan during the period of 2002–2004. Multivariate logistic regression analysis was used to identify the factors related to microangiopathies, macroangiopathiess and TyG index. The patients were stratified by TyG index quartile (Q1–Q4). Adjusted odds ratios (aORs) of albuminuria for Q3 versus Q1 and Q4 versus Q1 were 1.424 (95% confidence interval [CI], 1.062–1.910, p = 0.018) and 1.948 (95% CI, 1.437–2.642, p < 0.001), respectively. The aOR of cerebrovascular disease (CVA) was 2.264 for Q4 versus Q1 (95% CI, 1.243–4.122, p = 0.008), but there were no significant associations with diabetic retinopathy (DR), coronary artery disease (CAD) or peripheral artery occlusive disease (PAOD). Significant stepwise increases were found in CVA (p = 0.0013) and albuminuria ≥30 mg/g (p < 0.001) corresponding to TyG index quartiles, but not DR (p = 0.573), CAD (p = 0.880) or PAOD (p = 0.223). There was a significant association between a high TyG index and a high risk of microalbuminuria and CVA in the study cohort. Further studies to investigate the use of medications in patients with DM to prevent micro- and macro-angiopathies are thus warranted.

Antioxidative potential of antidiabetic agents: A possible protective mechanism against vascular complications in diabetic patients

Many vascular complications are related to exposure of tissues to elevated levels of glucose, a condition that promotes oxidative stress. The primary goal of antidiabetic medication is for normalization of blood glucose. However, antidiabetic medications may have antioxidant effects that go beyond their hypoglycemic influences. Therefore, antidiabetic drugs may be doubly beneficial in preventing diabetic complications. Vascular dysfunction due to uncontrolled diabetes is a serious complication of the disease and one which has a severe impact on quality of life. Readjustment of the oxidative balance in subjects with diabetes, and the positive effects thereof is a topic of intense interest at present. In the current review, we highlight the antioxidant effects of antidiabetic medications which may prevent or delay the onset of vascular dysfunction.

The Relationship between Carotid Intima-Media Thickness and Ocular Circulation in Type-2 Diabetes

Purpose

To compare clinical findings, including ocular blood flow and intima-media thickness (IMT) of the carotid artery, in mild nonproliferative diabetic retinopathy (NPDR) and no diabetic retinopathy (NDR) patients, and to determine risk factors contributing to mild NPDR.

Methods

In 129 subjects (129 eyes) with type-2 diabetes patients and mild NPDR or NDR, standard statistical techniques were used to determine associations between clinical findings, including diabetes duration, blood levels of creatinine and hemoglobin A1c (HbA1c), central macular thickness (CMT; measured with optical coherence tomography), mean blur rate (MBR; measured with laser speckle flowgraphy), and ultrasound-measured carotid IMT.

Results

Diabetes duration, IMT, and CMT were significantly higher in the mild NPDR patients than the NDR patients (P=0.004, P=0.004, and P=0.003, respectively), while conversely, MBR in the overall optic nerve head (MBR-A) was lower in the mild NPDR patients. Furthermore, a logistic regression analysis showed that diabetes duration (OR, 1.11; P=0.006), diastolic blood pressure (OR, 0.93; P=0.025), heart rate (OR, 1.07; P=0.004), IMT (OR, 8.65; P=0.005), and CMT (OR, 1.03; P=0.007) were independent contributing factors to mild NPDR. Spearman's rank correlation test also showed that IMT was negatively correlated with MBR-A (P=0.011).

Conclusions

Increased IMT showed a close association with ocular ischemia in patients with type-2 diabetes and contributed to the presence of mild NPDR. These findings suggest that IMT may be an early biomarker of mild NPDR.

Obesity, metabolic syndrome and diabetic retinopathy: Beyond hyperglycemia

Diabetic retinopathy (DR) is the most feared ocular manifestation of diabetes. DR is characterized by progressive retinal damage that may eventually result in blindness. Clinically, this blindness is caused by progressive damage to the retinal microvasculature, which leads to ischemia, retinal swelling, and neovascularization. Retinopathy is associated with both type 1 and type 2 diabetes, with DR being the leading cause of new onset blindness in United States adults. Despite this strong association with diabetes, it must be noted that the development of retinopathy lesions is multifactorial and may occur in individuals without an established history of diabetes. Metabolic syndrome is a multifactorial condition of central obesity, hypertriglyceridemia, dyslipidemia, hypertension, fasting hyperglycemia, and insulin resistance. Although several studies examined the individual components observed in the metabolic syndrome in relation to the development of DR, there is conflicting data as to the association of the metabolic syndrome with the development of retinopathy lesions in non-diabetic subjects. This review will summarize the current literature on the evidence of the metabolic syndrome on retinopathy in subjects with and without an established history of diabetes. This review will also discuss some of the mechanisms through which metabolic syndrome can contribute to the development of retinopathy.

The Relationship between Cardiovascular Autonomic Dysfunction and Ocular Abnormality in Chinese T2DM

OBJECTIVE

This study aims to explore the relationship between autonomic nerve dysfunction-assessed by cardiovascular autonomic neuropathy risk score (CAN-RS)-and ocular abnormality in Chinese type 2 diabetes mellitus (T2DM).

METHOD

This is a cross-sectional study. A total of 335 subjects with T2DM were enrolled. The state of visual acuity, the lens, the vitreous, and the fundus were tested by professional ophthalmic instruments. The electrochemical skin conductance (ESC) of the hands and feet was measured by SUDOSCAN, from which a cardiovascular autonomic neuropathy risk score (CAN-RS) was calculated. Receiver operating characteristic (ROC) curves were drawn to evaluate the feasibility and accuracy of CAN-RS in diabetic oculopathy screening.

RESULTS

Abnormalities of the lens, vitreous, and fundus accounted for 7.8%, 5.1%, and 9.9%, respectively, in this study. The means of hands and feet ESC were higher than 60 μS, and CAN-RS was 33.1 ± 14.8%. In logistic regression analysis, CAN-RS was positively associated with lens (OR = 1.055, P < 0.001) and vitreous (OR = 1.044, P < 0.01) abnormality. The area under ROC to detect lens and vitreous abnormality was 0.713 and 0.725, respectively.

CONCLUSION

CAN-RS, a cardiac autonomic nerve dysfunction index calculated by SUDOSCAN, may be a promising index for lens and vitreous abnormality screening in T2DM patients. Further studies are needed to confirm the conclusion.

Serum fetuin-A levels are independently correlated with vascular endothelial growth factor and C-reactive protein concentrations in type 2 diabetic patients with diabetic retinopathy

BACKGROUND

The higher expression of vascular endothelial growth factor (VEGF) and C-reactive protein (CRP) is associated with the development of diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM). Fetuin-A is shown to have proangiogenic and proinflammatory effects.

METHODS

This study included 245 T2DM patients consisting of 95 cases with non-diabetic retinopathy (NDR), 78 cases with non-proliferative diabetic retinopathy (NPDR) and 72 cases with proliferative diabetic retinopathy (PDR), in addition to 65 healthy controls. Serum fetuin-A, VEGF and CRP concentrations and related parameters were measured.

RESULTS

Significant positive correlations were found between fetuin-A and VEGF and CRP, and between VEGF and CRP in T2DM patients (all p<0.001). After adjustment for confounders, fetuin-A was correlated independently with VEGF and CRP in NPDR and PDR patients, but not in NDR subjects. In addition, fetuin-A was correlated independently with HOMA-IR (all 4 groups), HbA1c (NDR, NPDR and PDR groups) and duration of diabetes (PDR group). When compared with NDR and control subjects, NPDR and PDR patients had higher HOMA-IR.

CONCLUSIONS

Serum fetuin-A concentrations are independently correlated with VEGF and CRP concentrations in T2DM patients with DR, but not in NDR subjects.

Prevalence and risk factors of retinopathy in patients with or without metabolic syndrome: a population-based study in Shenyang

OBJECTIVE

To investigate the relationship between metabolic syndrome (MS) and the prevalence of retinopathy.

DESIGN

A cross-sectional study was carried out from August 2013 to September 2014 in Fengyutan Sub-District.

PRIMARY AND SECONDARY OUTCOME MEASURES

A total of 1163 eligible participants attended. All the participants were subjected to stereo fundus photography to detect retinopathy. The discrepancy of prevalence of retinopathy in different participants was described.

RESULTS

The prevalence of retinopathy was 9.64% in patients with MS and 3.91% in patients without MS. A higher prevalence of retinopathy with proliferative diabetic retinopathy was found in patients with MS. In multiple logistic regression analysis, independent risk factors for any retinopathy in patients with MS were longer diabetes duration (OR 1.07; 95% CI 1.04 to 1.10, per year increase), higher systolic blood pressure (SBP) (OR 1.16; 95% CI 1.09 to 1.29, per 10 mm Hg increase), higher diastolic blood pressure (DBP) (OR 1.24; 95% CI 1.12 to 1.35, per 10 mm Hg increase), higher fasting plasma glucose (OR 1.07; 95% CI 1.02 to 1.11, per 10 mg/dL increase), higher 2 h postprandial plasma glucose (OR 1.17; 95% CI 1.12 to 1.21, per 10 mg/dL increase), and higher haemoglobin A1c (HbA1c) (OR 1.23; 95% CI 1.13 to 1.34, per % increase). Similar independent risk factors, except for DBP, were found for any retinopathy in patients without MS.

CONCLUSIONS

The presence of MS components, hyperglycaemia (fasting glucose and HbA1c) and hypertension (SBP and DBP), are significantly associated with the prevalence of retinopathy.

Is there any correlation between vitamin D insufficiency and diabetic retinopathy?

AIM

To determine a relation between vitamin D level, which is an inhibitor of angiogenesis, and diabetic retinopathy and its risk factors.

METHODS

In a clinic-based cross sectional study two hundred and thirty-five type 2 diabetic patients older than 20y were selected. Patients were classified according to ophthalmologic examination as following: no diabetic retinopathy (NDR) (n=153), non-proliferative diabetic retinopathy (NPDR) (n=64) and proliferative diabetic retinopathy (PDR) (n=18). Study subjects were tested for fasting blood glucose, glycated hemoglobin A1C (HbA1C), lipid profile, microalbuminuria, HsCRP, IGF1, insulin (in patients without history of insulin taking) and 25 hydroxy vitamin D [25 (OH) D] levels. Vitamin D insufficiency was defined according to 25 (OH) D level less than 30 ng/mL. The relationship between diabetic retinopathy and serum 25 (OH) D insufficiency was evaluated.

RESULTS

The prevalence of diabetic retinopathy was 34.8% in our patients. Long duration of diabetes, hypertension, poor glycemic control, diabetic nephropathy, hyperinsulinemia and insulin resistance were risk factors for diabetic retinopathy but 25 (OH) D level was not significant different between NDR, NPDR and PDR groups. Correlation between 25 (OH) D level and other known risk factors of diabetic retinopathy was not significant.

CONCLUSION

This study did not find any association between diabetic retinopathy and its severity and vitamin D insufficiency. Vitamin D insufficiency is not related to risk factors of diabetic retinopathy.

Insulin sensitivity and complications in type 1 diabetes: New insights

Despite improvements in glucose, lipids and blood pressure control, vascular complications remain the most important cause of morbidity and mortality in patients with type 1 diabetes. For that reason, there is a need to identify additional risk factors to utilize in clinical practice or translate to novel therapies to prevent vascular complications. Reduced insulin sensitivity is an increasingly recognized component of type 1 diabetes that has been linked with the development and progression of both micro- and macrovascular complications. Adolescents and adults with type 1 diabetes have reduced insulin sensitivity, even when compared to their non-diabetic counterparts of similar adiposity, serum triglycerides, high-density lipoprotein cholesterol, level of habitual physical activity, and in adolescents, pubertal stage. Reduced insulin sensitivity is thought to contribute both to the initiation and progression of macro- and microvascular complications in type 1 diabetes. There are currently clinical trials underway examining the benefits of improving insulin sensitivity with regards to vascular complications in type 1 diabetes. Reduced insulin sensitivity is an increasingly recognized component of type 1 diabetes, is implicated in the pathogenesis of vascular complications and is potentially an important therapeutic target to prevent vascular complications. In this review, we will focus on the pathophysiologic contribution of insulin sensitivity to vascular complications and summarize related ongoing clinical trials.

Diabetic retinopathy and endothelial dysfunction in patients with type 2 diabetes mellitus

BACKGROUND

We investigated the relationship between endothelial dysfunction and diabetic retinopathy (DR) in patients with type 2 diabetes.

METHODS

We used a cross-sectional design to examine 167 patients with type 2 diabetes mellitus. All patients underwent biochemical and ophthalmological examination. We assessed endothelial dysfunction by a flow-mediated vasodilation method of the brachial artery. Changes in vasodilation (flow-mediated vasodilatation, %FMD) were expressed as percent change over baseline values.

RESULTS

The mean±standard deviation of patient age was 54.1±8.6 years. The %FMD was significantly lower in patients with DR than without DR. The prevalence of retinopathy decreased across increasing tertiles of %FMD. After adjusting for patients' age, sex, diabetes duration, use of insulin, use of antihypertensive, antiplatelet, and lipid lowering medications, systolic blood pressure, fasting plasma glucose, 2-hour plasma glucose, glycated hemoglobin, and urinary albumin excretion, participants with a reduced %FMD were more likely to have DR (odds ratio, 11.819; 95% confidence interval, 2.201 to 63.461; P=0.004, comparing the lowest and highest tertiles of %FMD).

CONCLUSION

Endothelial dysfunction was associated with DR, which was most apparent when the endothelial dysfunction was severe. Our study provides insights into the possible mechanism of the influence of endothelial dysfunction on the development of DR.

Intake of Gnetum africanum and Dacryodes edulis, imbalance of oxidant/antioxidant status and prevalence of diabetic retinopathy in central Africans

OBJECTIVE

To estimate the prevalence of DR and to correlate cardiometabolic, sociodemographic, and oxidant/antioxidant imbalance data to the prevalence of DR.

DESIGN

This case-control study included type 2 DM (T2 DM) patients with DR (n = 66), T2 DM patients without DR (N = 84), and healthy controls (n = 45) without DR, in Kinshasa town. Diet, albuminemia, serum vitamins, and 8-isoprostane were examined.

RESULTS

No intake of safou (OR = 2.7 95% CI 1.2-5.8; P = 0.014), low serum albumin <4.5 g/dL (OR-2.9 95% CI 1.4-5.9; P = 0.003), no intake of fumbwa (OR = 2.8 95% CI 1.2-6.5; P = 0.014), high 8-isoprostane (OR = 14.3 95% CI 4.5-46; P<0.0001), DM duration ≥ 5 years (OR = 3.8 95% CI 1.6-9.1; P = 0.003), and low serum vitamin C (OR = 4.5 95% CI 1.3-15.5; P = 0.016) were identified as the significant independent determinants of DR.

CONCLUSION

The important role of oxidant/antioxidant status imbalance and diet is demonstrated in DR.

Microangiopathy and visual deficits characterize the retinopathy of a spontaneously hypertensive rat model with type 2 diabetes and metabolic syndrome

Retinopathy has been increasing in prevalence as a consequence of type 2 diabetes and a cluster of coexisting risk factors characterized as the metabolic syndrome. However, the combined effects of these conditions on the retina are poorly understood. Therefore, we focused on the spontaneously hypertensive corpulent rat (SHR/N-cp), a model with type 2 diabetes, obesity and features of the metabolic syndrome to characterize retinal changes at a structural and functional level. SHR/N-cp males at 4 and 8 months of age were used in this study. Metabolic parameters and blood pressure were measured by standard methods. Morphology was investigated by histological techniques supplemented by nicotinamide adenine dinucleotide phosphate-diaphorase staining of whole mounts and fluorescein angiography to analyze the retinal vasculature. The in vivo function of the retina was examined by electroretinography (ERG). Obese SHR/N-cp rats were hypertensive and showed significant increases in body weight, serum levels of glucose, triglycerides, total cholesterol and urinary glucose excretion compared with lean controls (P < 0.01 for each). Histology indicated an overall intact integrity of the retina and aspects of microangiopathy in obese SHR/N-cp rats. ERG revealed intact processing of light signals but significantly decreased amplitudes of b-waves for all (P < 0.01) and of a-waves for some examined light intensities (P < 0.05). Oscillatory potentials were significantly protracted (P < 0.01), whereas amplitudes were not reduced. Microangiopathy and electroretinographic deficits combine to produce an early non-proliferative retinopathy phenotype in the obese SHR/N-cp rats. Thus, this model represents a valuable experimental tool to obtain further insights into the mechanisms of retinopathy in the context of obesity, type 2 diabetes and metabolic syndrome.