Abstract
PURPOSE: The purpose of this study was to investigate the correlation between insulin and Fetuin-B (FETUB) and the influence of FETUB on insulin signaling pathway in diabetic retinopathy (DR). METHODS: Enzyme-linked immunosorbent assay (ELISA) was used to analyze FETUB and insulin levels in the serum and aqueous fluid of patients with DR and healthy controls. Quantitative PCR (q-PCR), Western blotting, and ELISA were used to examine FETUB expression in ARPE-19, BV2, and Müller cells under insulin stimulation. Co-immunoprecipitation was used to investigate the interaction of FETUB with insulin receptor-β (IRβ). Insulin resistance (IR)-BV2 and IR-Müller cells were treated with FETUB recombinant protein or FETUB short hairpin RNA (shRNA) to explore the influence of FETUB on insulin signaling pathway in DR. LY294002 (a PI3K pathway inhibitor) was used to determine whether FETUB affects glucose metabolism via the PI3K/Akt pathway. RESULTS: In aqueous fluid, FETUB concentrations were positively correlated with insulin levels. FETUB expression increased in Müller and BV2 cells under insulin regulation, and FETUB interacted with IRβ in retinal cells and mice retina. The interaction between IRβ and FETUB increased in BV2 and Müller cells under high-glucose than in controls. Insulin signaling pathway activation was suppressed in FETUB recombinant protein-treated BV2 and Müller cells but increased in FETUB shRNA-transfected cells. FETUB shRNA could not reverse LY294002-mediated inhibition of glucose transporter-4 expression. CONCLUSIONS: Retinal cells are the source of insulin-regulated FETUB. The FETUB interacts with IRβ and affects insulin signaling pathway in BV2 and Müller cells. FETUB may aggravate IR in BV2 and Müller cells via the PI3K/Akt pathway.