Neurodegeneration in Diabetic Retinopathy: Current Concepts and Therapeutic Implications

Efficacy and Safety of Qiming Granule for Nerve Injury Associated with Non-proliferative Diabetic Retinopathy: A Multicenter, Randomized, Non-inferiority, Active-Controlled Clinical Trial

OBJECTIVE

To evaluate the efficacy and safety of Qiming Granule as an early treatment for patients with nerve injury associated with non-proliferative diabetic retinopathy (NPDR).

METHODS

This was a multicenter, randomized, non-inferiority, active-controlled clinical trial. Patients with NPDR complicated with nerve injury, regardless of whether they presented with fundus abnormalities, were randomly assigned in a 1:1 ratio via a randomized number table to orally receive either 4.5 g of Qiming Granule or 0.5 g of calcium dobesilate (CaD), both 3 times daily for 24 weeks. The primary endpoints were changes in retinal nerve fiber layer (RNFL) thickness and foveal avascular zone (FAZ) area from baseline to week 24. The secondary endpoints included changes in RNFL thickness and FAZ area from baseline to week 12, and visual function questionnaire (NEI-VFQ-25) and health survey questionnaire (SF-36 scale), CM syndrome element scale score and the rates of abnormal full-field electroretinogram (ERG), abnormal dilated fundus, and abnormal visual acuity at treatment of weeks 12 and 24. Adverse drug reactions (ADRs) were detected.

RESULTS

A total of 82 patients were enrolled in the study. Changes in RNFL thickness from baseline to week 24 in the Qiming Granule and CaD groups were -1.53 ± 9.88 µm and -4.61 ± 9.23 µm, respectively (a difference of 3.08 µm [97.5% CI: -2.11 to 8.25]). Changes in FAZ area from baseline to week 24 were -0.08 ± 0.39 mm2 and 0.01 ± 0.05 mm2, respectively (a difference of -0.09 mm2 [97.5% CI: -0.26 to 0.08]). Non-inferiority was achieved for both primary endpoints. There were no significant differences between the two groups in secondary endpoints, including changes in RNFL thickness and FAZ area from baseline to week 12, rates of abnormal ERG, dilated fundus, and visual acuity results at weeks 12 and 24, as well as NEI-VFQ-25, SF-36 scale, and CM syndrome element scale scores at week 24. ADRs were detected in 4 (9.76%) and 1 (2.44%) patients in the Qiming Granule and CaD groups, respectively. No serious ADRs occurred.

CONCLUSION

Qiming Granule demonstrates non-inferiority in terms of efficacy and safety as an early treatment for nerve injury associated with NPDR. (Registration No. ISRCTN39825773).

Vessel Density around Foveal Avascular Zone as a Potential Imaging Biomarker for Detecting Preclinical Diabetic Retinopathy: An Optical Coherence Tomography Angiography Study

Purpose: The purpose of this study was to investigate the changes of optical coherence tomography angiography (OCTA) parameters in diabetic retinopathy (DR) using an updated software with 3D projection artifact removal. Methods: In this cross-sectional observational study, 192 eyes of 111 patients with diabetes mellitus (DM) and 55 eyes of 34 age-matched healthy subjects were included. Diabetic patients were divided into three subgroups: without DR, with mild non-proliferative DR, and with moderate-to-severe non-proliferative DR. All eyes underwent dilated fundoscopy along with 3x3mm and 6x6mm OCTA image acquisition. Vessel density (VD), retinal thickness and foveal avascular zone (FAZ) parameters were analyzed. Correlation analyses between OCTA parameters and DR severity were also performed. Results: There was a statistically significant difference in all OCTA parameters among groups, except for superficial foveal VD in 6x6mm scan and whole image retinal thickness in both 3x3mm and 6x6mm scans, while 3x3mm scan parameters were found to be diagnostically superior to the corresponding ones of 6x6mm scan. As the DR stage progressed, the mean VD values decreased. FD-300, which is the VD of a 300-μm width annulus surrounding FAZ, demonstrated the strongest inverse correlation with DR severity (r = -0.590/r_s = -0.562, p < .001) and showed the highest area under the ROC curve (AUROC = 0.833 ± 0.030, p < .001) in scan 3 × 3. Conclusion: OCTA shows progressive decrease of VD parameters with increasing DR severity. Foveal VD, FAZ area, and perimeter are not very useful indexes due to the high interindividual variability of FAZ size. OCTA and specifically FD-300 may serve as a promising DR screening tool for detecting preclinical microvascular alterations.

Metabolic profile of visual cortex in diabetic rats measured with in vivo proton MRS

The purpose of the present study was to characterize the metabolic profile of the visual cortex in streptozotocin-induced Type 1 diabetic rats by means of in vivo proton MRS. Several metabolite concentration ratios in the visual cortex were calculated. In addition, postmortem histologic analyses for retinal ganglion cell (RGC) loss, optic nerve injury and visual cortex alterations were monitored. The results showed that diabetes induced several changes in visual cortex metabolites, such as reduced N-acetylaspartate, glutamate, γ-aminobutyric acid, taurine and choline-containing compound levels. Nevertheless, myo-inositol levels increased significantly as compared with controls. Remarkable RGC loss and optic nerve degeneration were observed by morphological analysis. Moreover, the results showed significant neuronal loss and glial activation in the visual cortex. These findings indicated that, besides vascular abnormalities, neuronal loss and degeneration in the visual pathway were induced due to disrupted glucose homeostasis in diabetes. Metabolic or functional abnormalities were induced in cerebral neurons of the visual cortex by diabetes.