Diabetic retinopathy: challenges and future directions

Lp-PLA2 activity is associated with increased risk of diabetic retinopathy: a longitudinal disease progression study

AIMS/HYPOTHESIS

The aim of the study was to examine the association between lipoprotein-associated phospholipase A2 (Lp-PLA2) activity levels and incident diabetic retinopathy and change in retinopathy grade.

METHODS

This was a cohort study of diabetic participants with serum collected at baseline and routinely collected diabetic retinal screening data. Participants with type 2 diabetes from the GoDARTS (Genetics of Diabetes Audit and Research in Tayside Scotland) cohort were used. This cohort is composed of individuals of white Scottish ancestry from the Tayside region of Scotland. Survival analysis accounting for informative censoring by modelling death as a competing risk was performed for the development of incident diabetic retinopathy from a disease-free state in a 3 year follow-up period (n = 1364) by stratified Lp-PLA2 activity levels (in quartiles). The same analysis was performed for transitions to more severe grades.

RESULTS

The hazard of developing incident diabetic retinopathy was 2.08 times higher (95% CI 1.64, 2.63) for the highest quartile of Lp-PLA2 activity compared with the lowest. Higher Lp-PLA2 activity levels were associated with a significantly increased risk for transitions to all grades. The hazards of developing observable (or more severe) and referable (or more severe) retinopathy were 2.82 (95% CI 1.71, 4.65) and 1.87 (95% CI 1.26, 2.77) times higher for the highest quartile of Lp-PLA2 activity compared with the lowest, respectively.

CONCLUSIONS/INTERPRETATION

Higher Lp-PLA2 levels are associated with increased risk of death and the development of incident diabetic retinopathy, as well as transitions to more severe grades of diabetic retinopathy. These associations are independent of calculated LDL-cholesterol and other traditional risk factors. Further, this biomarker study shows that the association is temporally sensitive to the proximity of the event to measurement of Lp-PLA2.

VEGF -634G>C polymorphism and diabetic retinopathy risk: a meta-analysis

BACKGROUND

Vascular endothelial growth factor (VEGF), a multifunctional cytokine that promotes angiogenesis and is a potent mediator of microvascular permeability, which is critical for the development of diabetic retinopathy (DR). It has demonstrated that VEGF -634G>C (rs2010963) polymorphism alters the transcriptional activity of the gene. However, studies on the association between VEGF -634G>C polymorphism and DR in type 2 diabetes have reported conflicting results. Thus, the aim of the present study was to investigate whether VEGF -634G>C polymorphism is associated with the risk of DR in type 2 diabetes.

METHODS

A systematic search of electronic databases (PubMed, Embase and Web of Science) and reference lists of relevant articles was carried out until September 15, 2012. The pooled odds ratios (ORs) and their corresponding 95% confidence interval (CI) were calculated by a fixed effect model.

RESULTS

A total of 1525 DR cases and 1422 diabetic without retinopathy (DWR) controls in 9 independent studies were included in the meta-analysis. A significant relationship between VEGF -634G>C polymorphism and DR was found in an allelic genetic model (OR: 1.13, 95% CI: 1.01 to 1.25, P=0.03) and a recessive genetic model (OR: 1.26, 95% CI: 1.02 to 1.55, P=0.03).

CONCLUSION

Our research confirmed the association between the VEGF -634G>C polymorphism and DR in subjects with type 2 diabetes. Well-designed studies with larger sample size and more ethnic groups are required to further validate the results.

Association analysis of -429T/C and -374T/A polymorphisms of receptor of advanced glycation end products (RAGE) gene in Malaysian with type 2 diabetic retinopathy

Conflicting results have been reported in different populations on the association between two particular RAGE gene polymorphisms (-429T/C and -374T/A) and retinopathy in diabetic patients. Therefore this study was designed to assess the association between both gene polymorphisms with retinopathy in Malaysian diabetic patients. A total of 342 type 2 diabetic patients [171 without retinopathy (DNR) and 171 with retinopathy (DR)] and 235 healthy controls were included in this study. Genomic DNA was obtained from blood samples and the screening for the gene polymorphisms was done using polymerase chain reaction-restriction fragment length polymorphism approach. Overall, the genotype distribution for both polymorphisms was not statistically different (p>0.05) among the control, DNR and DR groups. The -429C minor allele frequency of DR group (12.0%) was not significantly different (p>0.05) when compared to DNR group (16.1%) and healthy controls (11.3%). The -374A allele frequency also did not differ significantly between the control and DNR (p>0.05), control and DR (p>0.05) as well as DNR and DR groups (p>0.05). This is the first study report on RAGE gene polymorphism in Malaysian DR patients. In conclusion, -429T/C and -374T/A polymorphisms in the promoter region of RAGE gene were not associated with Malaysian type 2 DR patients.

Risk factors for diabetic retinopathy in a rural Chinese population with type 2 diabetes: the Handan Eye Study

PURPOSE

To describe risk factors associated with diabetic retinopathy (DR) in a population-based sample of rural Chinese with type 2 diabetes.

METHODS

The Handan Eye Study is a population-based cross-sectional study surveyed 6830 Chinese people aged 30+ years from 13 randomly selected villages in 2006-2007. All participants underwent a standardized interview and extensive examinations including ophthalmologic and systemic conditions. Diabetic retinopathy was graded from fundus photographs according to the modified Early Treatment Diabetic Retinopathy Study classification system. Logistic regression models were used to assess risk factors associated with DR.

RESULTS

Of 7577 eligible persons, 6830 (90.4%) participated, of which 5597 (81.9%) had fasting plasma glucose (FPG) data. There were 387 (6.9%) participants with diabetes, and 368 (95.1%) had gradable fundus photographs. The age-standardized prevalence of DR was 43.1%. In multivariable-adjusted logistic regression models for all diabetic participants, independent risk factors for DR were longer duration of diabetes (odds ratio [OR] 3.07, 95% confidence interval [CI] 1.94, 4.85, per 5 years of duration), higher FPG levels (OR 1.17; 95% CI: 1.08, 1.27, per mmol/l increase) and higher systolic blood pressure (OR 1.22; 95% CI: 1.08, 1.37, per 10 mmHg increase). For newly diagnosed diabetes, the only significant factor of DR was higher FPG levels (OR 1.17; 95% CI: 1.05, 1.29, per mmol/l increase).

CONCLUSIONS

In rural Chinese persons with diabetes, longer diabetes duration, hyperglycaemia and elevated blood pressure are risk factors for DR. These findings underscore the importance of controlling classic risk factors for DR in developing countries, where diabetes prevalence is increasing.

Age related maculopathy and diabetes

PURPOSE

To compare the prevalence of age-related maculopathy (ARM) in a sample of diabetic patients with the general population.

METHODS

Binocular indirect ophthalmoscopy, biomicroscopy, and fluorescein angiography. Retrospective prevalence study; descriptive-observational case-control type. Two different groups were analyzed from a sample of 1000 consecutive files of diabetic patients: 1) 65 to 74 years old (n = 263) and 2) 75 years and older (n = 199). Prevalence was compared to that of the general population in a control group and the following epidemiologic studies: Beaver Dam Eye Study, Framingham Eye Study, Blue Mountains Study, and Rotterdam Eye Study.

RESULTS

In diabetic patients aged 75 or older, prevalence of ARM was as follows: early lesions 2.51% (5/199), late lesions (ARMD) 2.51% (5/199). In comparison, the risk in patients 75 or older is as follows: control group (ARMD): OR 4.79, 95% CI 1.778-12.033, p (Fisher) 0.0005; Beaver Dam Eye Study (ARMD): OR 2.93, 95% CI 1.152-7.450, p (Fisher): 0; Blue Mountains Eye Study (ARMD): OR 3.06, 95% CI 1.208-7.754, p (Fisher): 0; Framingham Eye Study (ARM): OR 6.73, 95% CI 3.041-14.880, p (Fisher): 0; Rotterdam Eye Study: p (Fisher) 0.133.

CONCLUSIONS

1) A lower prevalence of ARM was found in the sample of diabetic patients aged 75 or older than in the general population (with the exception of the Rotterdam study). 2) Prevalence of ARM was even lower in diabetic patients presenting diabetic retinopathy, whether or not they had been treated with photocoagulation. 3) In diabetic patients, the exudative form was more frequent than the atrophic form, in an inverse ratio to that of the general population.

Accuracy of primary care clinicians in screening for diabetic retinopathy using single-image retinal photography

PURPOSE

Diabetic patients with limited access to ophthalmologists have low screening rates for diabetic retinopathy. We evaluated a diabetic retinopathy screening program in a community health center using single images taken with a nonmydriatic retinal camera and primary care clinicians trained to read retinal images.

METHODS

This study was conducted from 2001 to 2004 in a multisite community health center staffed by family physicians, advanced practice nurses, and physician's assistants. The clinic serves a primarily low-income, Hispanic population. Clinic clinicians were trained to read the retinal photographs. All images were overread by an ophthalmologist. Patients were referred to eye care specialists for severe diabetic retinopathy, unknown or other abnormality, or inadequate photographs. We analyzed agreement between the clinicians and the ophthalmologist in recognizing diabetic retinopathy and in determining which patients needed referral. We also analyzed overall screening rates based on clinic access to the camera.

RESULTS

One thousand forty diabetic patients were screened for diabetic retinopathy at the health center. One hundred thirteen (10.9%) were found to have diabetic retinopathy, 46 severe enough to warrant referral to an ophthalmologist. The clinicians failed to refer 35 (10.2%) of the 344 patients the ophthalmologist believed needed referral. Most cases of missed referral were due to failure to recognize an inadequate photograph or for abnormalities other than diabetic retinopathy. Screening rates were better in the clinic with a permanent camera.

CONCLUSIONS

Primary care clinicians trained to read single images from a retinal camera have acceptable accuracy in screening for diabetic retinopathy. Further training may be necessary to recognize other common abnormalities.

Biologic risk factors associated with diabetic retinopathy: the Los Angeles Latino Eye Study

OBJECTIVE

To identify biologic risk factors associated with having diabetic retinopathy (DR) in Latinos with type 2 diabetes mellitus (T2DM).

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Six thousand three hundred fifty-seven Latinos ages > or =40 years from 6 census tracts in Los Angeles, California.

METHODS

An in-home interview was administered to all participants in the Los Angeles Latino Eye Study (LALES). All participants diagnosed with T2DM underwent a complete ophthalmologic examination including stereoscopic fundus photography (7 standard Early Treatment Diabetic Retinopathy Study fields). Photographs were graded in a masked manner using a modified Airlie House grading system to assess presence and severity of DR. Univariate and stepwise logistic regression analyses were used to identify independent risk factors.

MAIN OUTCOME MEASURES

Biologic risk factors associated with any DR and proliferative DR (PDR).

RESULTS

Of the 7789 eligible individuals in LALES, 6357 (82%) had a clinical examination. One thousand two hundred sixty-three participants had definite diabetes and 1187 Latinos had T2DM. Of those with T2DM, 46% (544) had DR. Stepwise logistic regression analyses revealed that compared with females, males had a 50% higher risk of having any DR (OR = 1.50; P = 0.006). Factors independently associated with a greater risk of having any DR were longer duration of known diabetes (per year, OR = 1.08, P<0.0001), higher glycosylated hemoglobin levels (per 1%, OR = 1.22, P<0.0001); higher systolic blood pressure (per 20 mmHg, OR = 1.26, P = 0.002); and insulin treatment (OR = 1.60, P = 0.01). Factors independently associated with PDR included longer duration of known diabetes (per year, OR = 1.06, P<0.0001); being on insulin treatment (OR = 3.2, P<0.0001); and a higher systolic blood pressure (per 20 mmHg, OR = 1.44, P = 0.01). The relationship of these variables to the risk of having DR or PDR is not a constant linear function in all cases and varies depending on the variable.

CONCLUSIONS

Our study showed that the high risk of DR in adult Latinos is independently associated with both nonmodifiable and modifiable risk factors. These findings suggest that controlling hyperglycemia and hypertension in this ethnic group may reduce the high risk of having DR associated with T2DM.