Circulating biomarkers of diabetic retinopathy: a systematic review and meta-analysis

Serological inflammatory factors as biomarkers for anatomic response in diabetic macular edema treated with anti-VEGF

PURPOSE

To study the relationship between systemic pro-inflammatory factors and macular structural response to intravitreal bevacizumab for diabetic macular edema (DME).

METHODS

Prospective study including 30 cases with DME, treated with bevacizumab and a minimum follow-up of 6 months. All cases underwent baseline laboratory testing for cardiovascular risk (high sensitivity C-reactive protein (hsCRP), homocystein), dyslipidemia, renal dysfunction and glucose control. Serum levels of VEGF, soluble ICAM-1, MCP-1 and TNF-α were assessed by enzyme-linked immunosorbent assay kits. Significant associations between systemic factors and quantitative and qualitative spectral-domain optical coherence macular features were analyzed.

RESULTS

A mean of 4.82 ± 0.56 intravitreal injections was performed, resulting in significant improvement of central foveal thickness (CFT) (p < 0.001). A significant association with third month CFT decrease <10% was found for hsCRP (3.33 ± 2.01 vs 1.39 ± 1.15 mg/l, p = 0.007) and ICAM1 (975.54 ± 265.49 vs 727.07 ± 336.09 pg/ml, p = 0.012). ROC curve analysis indicated hsCRP and ICAM1 as significant biomarkers for 3rd month reduced anatomic response (area under the curve (AUC) = 0.807, p = 0.009 for hsCRP; AUC = 0.788, p = 0.014 for ICAM1). ROC curve analysis revealed hsCRP as a significant biomarker for 6th month CFT decrease <10% (AUC = 0.903, p < 0.001, cutoff value = 1.81 mg/l). A significant association with 6th month CFT decrease ≥25% was found for serum MCP1 (244.69 ± 49.34 pg/ml vs 319.24 ± 94.88 pg/ml, p = 0.017) and serum VEGF (90.84 ± 37.33 vs 58.28 ± 25.19 pg/ml, p = 0.027). The combined model of serum VEGF and LDL-cholesterol was found to be predictive of 6th month hard exudate severity (p = 0.001, r2 = 0.463).

CONCLUSIONS

Increased levels of hsCRP and ICAM1 were found to be significant biomarkers for early reduced anatomic response to anti-VEGF treatment. Cases with higher serum levels of such factors had increased CFT values, despite treatment, suggesting inner blood-retinal barrier breakdown that is not adequately responsive to anti-VEGF monotherapy.

Circulating markers of inflammation and endothelial function, and their relationship to diabetic retinopathy

AIM

To examine the relationships of serum markers of inflammation and endothelial function to diabetic retinopathy.

METHODS

We recruited 224 patients with diabetes (85 with Type 1 and 139 with Type 2 diabetes) aged 18-70 years. Serum markers of inflammation (high-sensitivity C-reactive protein) and endothelial function (soluble intercell adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, endothelin-1 and total nitrite) were assessed using nephelometry, immunoassays and spectroscopy. Diabetic retinopathy was graded from two-field fundus photographs according to the Airlie House Classification system and was categorized into no diabetic retinopathy, mild non-proliferative diabetic retinopathy, moderate non-proliferative diabetic retinopathy and vision-threatening diabetic retinopathy, the latter comprising severe non-proliferative diabetic retinopathy, proliferative diabetic retinopathy or clinically significant macular oedema. Multinomial logistic regression was used to assess the associations between serum markers and diabetic retinopathy.

RESULTS

In the study, 64% of patients (144/224) had diabetic retinopathy and 25% (57/244) had vision-threatening diabetic retinopathy. After controlling for age, gender, diabetes duration, HbA1c , systolic blood pressure, total and HDL cholesterol, smoking, the use of insulin or oral hypoglycaemic agents, nephropathy and cardiovascular disease, a positive association was found between increasing high-sensitivity C-reactive protein levels and the presence of vision-threatening diabetic retinopathy (odds ratio 1.26; 95% CI 1.05-1.51, per sd increase in high-sensitivity C-reactive protein). After stratifying by BMI ( ≥ 30 and < 30 kg/m(2) ), this association was found to be more pronounced in people with a BMI ≥ 30 kg/m(2) (odds ratio 2.9; P for interaction = 0.019). No associations were found between serum markers of endothelial activation and diabetic retinopathy.

CONCLUSIONS

Higher C-reactive protein levels, but not markers of endothelial function, may be related to more severe diabetic retinopathy. This finding suggests that inflammatory processes are involved in severe diabetic retinopathy, particularly in patients with a BMI ≥ 30 kg/m(2) .

Vitreous biomarkers in diabetic retinopathy: a systematic review and meta-analysis

The aim of this study was to perform a systematic meta-analysis of biomarkers investigated with diabetic retinopathy (DR) in the vitreous, and to explore the molecular pathway interactions of these markers found to be consistently associated with DR. Relevant databases [PubMed and ISI web of science] were searched for all published articles investigating molecular biomarkers of the vitreous associated with DR. Based on set exclusion/inclusion criteria available data from studies with human vitreous samples were extracted and used for our meta-analysis. The interactions of significant biomarkers in DR were investigated via STRING and KEGG pathway analysis. Our meta-analysis of DR identifies eleven biomarkers as potential therapeutic candidates alternate to current anti-VEGF therapy. Four of these are deemed viable therapeutic targets for PDR; ET receptors (ET A and ET B), anti-PDGF-BB, blocking TGF-β using cell therapy and PEDF. The identification of supplementary or synergistic therapeutic candidates to anti VEGF in the treatment of DR may aid in the development of future treatment trials.