Proteomic study of aqueous humour in diabetic patients with cataracts by TMT combined with HPLC-MS/MS

The

A list of differential proteins in the human aqueous humour of diabetic patients was established. Proteins with high interaction scores as per protein interaction analysis, such as GC and TTR, were further verified and could potentially be used as early diagnostic markers for diabetic eye complications in clinical practice.

Patients were divided into the diabetic experimental group and the non-diabetic control group. Aqueous humour specimens were obtained via cataract surgery. Sample proteins were treated with a TMT reagent, separated using a cation chromatography column, and analysed using a C18 desalting column. Proteins were identified using HPLC-MS/MS. The differential proteins were identified using both a p value of < 0.05 and a fold change of > 1.2. GO classification enrichment analysis, KEGG pathway enrichment analysis, protein interaction network analysis, and ingenuity pathway analysis were all carried out. The expression level of four differential proteins were verified by Western blot, and GC and TTR expressions were further examined using an expanded sample pool.

The postprandial glucose levels between the experimental group (9.40 ± 1.35 mmol/L) and the control group (6.56 ± 0.81 mmol/L) were significantly different, with a p value of 1.16E-06. It is important to note, however, that the baseline levels of the parameters showed no statistical differences. In total, 397 aqueous humour proteins were identified; of these, 137 showed significant differences, with 63 upregulated ones and 74 down-regulated ones. The differential proteins play important roles in numerous biological processes and pathways, such as complement and coagulation cascades (p = 1.71E-09). Some of these differential proteins are associated with diabetic retinal degeneration and other diabetic complications. Differential proteins, such as HP, GC, and TTR, have high node degree in the protein interaction network. Western blot results further confirmed that GC were down-regulated while TTR was up-regulated in aqueous humour under diabetic condition.