No abstract

Retinal neurodegeneration develops early in the course of diabetic retinopathy (DR), and our previous research showed that succinate accumulation results in retinal ganglion cells (RGCs) dysfunction in the retinas of rats with DR. Succinate can enhance lysine succinylation, but the succinylation of DR is not well understood. In this study, we investigated the role of the succinylome in DR and identified the key factor in this process. TMT labeling and LC–MS/MS analysis were combined to quantify the differentially succinylated proteins between vitreous humor (VH) samples from DR and non-DR patients. A total of 74 sites in 35 proteins were differentially succinylated between DR and non-DR vitreous humor samples, among which succinylation of the K108 site of optineurin (OPTN K108su) in the defense response was enriched by GO analysis based on the biological process category. Then, using a streptozotocin (STZ)-induced diabetic rat model, R28 cells and primary rat RGCs (rRGCs), we demonstrated that OPTN underwent lysine succinylation in the retinas of rats with DR and that OPTN K108su mediated autophagic flux blockade under high-glucose (HG) conditions. Sirt5 can desuccinylate OPTN K108su, thus protecting RGCs function from high glucose-induced RGCs autophagic flux blockade in the diabetic retina. Overall, desuccinylation of OPTN is an essential adaptive mechanism for ameliorating autophagic flux blockade in RGCs under DR conditions, and targeting the Sirt5-desuccK108-OPTN axis may thus open an avenue for therapeutic intervention in RCGs dysfunction.

AIM: To perform a quantitative analysis of the peripapillary vessel density (VD) and retinal nerve fiber layer (RNFL) thickness changes in patients with early stage of diabetic retinopathy (DR). METHODS: In this case-control study, swept-source optical coherence tomography angiography (SS-OCTA) imaging was used to examine diabetic and age-matched healthy subjects. The optic disc HD 6×6 mm2 blood flow imaging scan mode was selected. Automatic software was used to measure the peripapillary VD, capillary vessel density (CVD), and RNLF in an optic nerve head (ONH) filed based on the Garway-Heath map. In addition, the correlation between peripapillary VD, CVD, and RNFL was further investigated. RESULTS: The cohort consisted of 32 healthy individuals and 72 patients with diabetes (34 eyes with no DR and 38 eyes with mild-moderate NPDR). Peripapillary VD decreased in the mild-moderate NPDR group compared to the control group in most regions (P<0.05). Peripapillary CVD and RNFL thickness were significantly lower in the mild-moderate NPDR group in the superior temporal (ST) quadrants (P=0.018, P=0.030). In the correlation analysis of each region, the RNFL thickness in the NS region was positively correlated with the peripapillary VD and CVD (r=0.233, P=0.05; r=0.288, P=0.015). In the TI region, the RNFL thickness was positively correlated with the peripapillary CVD (r=0.237, P=0.047). CONCLUSION: The measurement based on the ONH topographic map may be helpful in detecting functional and structural impairments in DR. The peripapillary VD, CVD and RNFL decrease in early DR, and the RNFL thickness altered in association with the CVD or/and VD in some regions.