Proteomics of Vitreous Humor Reveals PPARA, RXR, and LXR Are Possible Upstream Regulators of Proliferative Diabetic Retinopathy

The Combination of PPARα Agonist GW7647 and Imeglimin Has Potent Effects on High-Glucose-Induced Cellular Biological Responses in Human Retinal Pigment Epithelium Cells

BACKGROUND

Hyperglycemic changes in the cellular biological properties of retinal pigment epithelium cells are involved in the pathophysiology of diabetic retinopathy (DR). To assess the effects of the new anti-diabetic agent imeglimin (Ime) on DR, the pharmacological effects of Ime and those of metformin (Met) in combination with the PPARα agonist GW7646 (GW) on adult retinal pigment epithelium (ARPE19) cells cultured in high-glucose conditions were compared.

METHODS

Cell viability, levels of reactive oxygen species (ROS), monolayer barrier function measured by transepit very much helial electrical resistance (TEER), and metabolic functions determined by an extracellular flux analyzer were evaluated.

RESULTS

While glucose concentrations did not alter cell viability regardless of the presence of Met or Ime, levels of ROS were significantly increased by the high-glucose conditions, and increased levels of ROS were significantly alleviated by the combination of Ime and GW but not by Met alone. Similarly, TEER values were increased by high-glucose conditions, but the effects of high-glucose conditions were dramatically enhanced by the combination of Ime and GW. Furthermore, a metabolic assay showed that an energetic shift was induced by the combination of Ime and GW, whereas energy status became quiescent with Met or Ime alone.

CONCLUSIONS

The collective results suggest that Ime in combination with GW has synergetic effects on high-glucose-induced cellular biological changes in ARPE19 cells.

Aqueous humor proteomics analyzed by bioinformatics and machine learning in PDR cases versus controls

BACKGROUND

To comprehend the complexities of pathophysiological mechanisms and molecular events that contribute to proliferative diabetic retinopathy (PDR) and evaluate the diagnostic value of aqueous humor (AH) in monitoring the onset of PDR.

METHODS

A cohort containing 16 PDR and 10 cataract patients and another validation cohort containing 8 PDR and 4 cataract patients were studied. AH was collected and subjected to proteomics analyses. Bioinformatics analysis and a machine learning-based pipeline called inference of biomolecular combinations with minimal bias were used to explore the functional relevance, hub proteins, and biomarkers.

RESULTS

Deep profiling of AH proteomes revealed several insights. First, the combination of SIAE, SEMA7A, GNS, and IGKV3D-15 and the combination of ATP6AP1, SPARCL1, and SERPINA7 could serve as surrogate protein biomarkers for monitoring PDR progression. Second, ALB, FN1, ACTB, SERPINA1, C3, and VTN acted as hub proteins in the profiling of AH proteomes. SERPINA1 was the protein with the highest correlation coefficient not only for BCVA but also for the duration of diabetes. Third, "Complement and coagulation cascades" was an important pathway for PDR development.

CONCLUSIONS

AH proteomics provides stable and accurate biomarkers for early warning and diagnosis of PDR. This study provides a deep understanding of the molecular mechanisms of PDR and a rich resource for optimizing PDR management.

Differences in aqueous humor protein profiles in patients with proliferative diabetic retinopathy before and after aflibercept treatment

PURPOSE

To investigate the changes in aqueous humor (AH) protein profiles before and after intravitreal aflibercept (IVA) treatment in patients with proliferative diabetic retinopathy (PDR).

METHODS

5 PDR patients provided 10 samples of AH before and after IVA treatment (pre-group vs. post-group). Proteins were identified using liquid chromatography-tandem mass spectrometry. Then, bioinformatics was employed to investigate the functional significance of differentially expressed proteins (DEPs) and hub proteins.

RESULTS

A total of 16 DEPs were identified, consisting of 8 downregulated proteins and 8 upregulated proteins. Bioinformatics analysis indicated that the most significantly enriched biological process was "blood coagulation, intrinsic pathway." The most significantly enriched signaling pathway was "complement and coagulation cascades." HBB, HPX, VEGFA, and CA1 were identified as hub proteins for IVA treatment.

CONCLUSIONS

Together with the downregulation of the intravitreal vascular endothelial growth factor level, IVA may also change the AH protein composition in PDR patients, with DEPs involved in the blood coagulation, intrinsic pathway, complement, and coagulation cascades. IVA treatment may protect against PDR by regulating HBB, HPX, VEGFA, and CA1 expression.