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Saori Inafuku, Kousuke Noda, Maho Amano, Miyuki Murata, Wataru Saito, Tetsu Ohashi, Atsuhiro Kanda, Shin-Ichiro Nishimura, Susumu Ishida; Alteration of N-glycan Profiles in Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4284.
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© ARVO (1962-2015); The Authors (2016-present)
Glycans are biopolymers bearing biological information. Since proteins acquire their properties through the binding of glycans on their structure, alteration of glycans is known to vary the function of proteins. So far, much attention has been paid to its relevance to the pathogenesis of diseases; for instance, it has been reported that sialylated glycans are increased in the sera of patients with cancers. Therefore, alteration of glycan profiles in ocular diseases such as diabetic retinopathy (DR) is of great interest. Recently, we established the technique to analyze the glycan profile in vitreous fluid and reported the profile of N-glycans in the vitreous obtained from patients with epiretinal membrane (ERM) and macular hole (MH). In this study, we investigate the profile of N-glycans in patients with proliferative diabetic retinopathy (PDR).
Plasma and vitreous samples were collected from 17 patients (10 females and 7 males) with PDR, and 17 patients (8 females and 9 males) with ERM and MH (non-DR). Profiles of N-glycans were analyzed by glycoblotting-based high throughput protocol. Human retinal microvascular endothelial cells (HRMECs) were cultivated with culture media containing either low glucose (5mM) or high glucose (25mM) and expression level of ST3GAL1 and ST3GAL4, both of which are sialyltransferases, were analyzed by real-time polymerase chain reaction (PCR) and ELISA.
Amount of N-glycans was significantly higher in the vitreous fluid of patients with PDR (495.5±37.4pmol/100μg protein) than those of patients with non-DR (142.7±30.8pmol/100μg protein, P<0.001). Composition analysis showed that N-glycans with sialic acids increased in the vitreous of PDR (328.4±25.8pmol/100μg protein) compared to those of non-DR (92.1±21.2pmol/100μg protein, P<0.0001), whereas there was no significant difference in plasma between PDR and non-DR. Expression levels of ST3GAL1 and ST3GAL4 were significantly upregulated 6h after high glucose stimulation (1.5-fold and 1.7-fold, respectively, P<0.05). In accord with this, high glucose stimulation increased the protein levels of ST3GAL1 (117.4±14.9pg/mg, P<0.01) and ST3GAL4 (6.1±0.9pg/mg, P<0.05) in HRMECs, compared with the cells cultured with low glucose culture media (ST3GAL1, 64.4±5.8pg/mg; ST3GAL4, 3.8±0.3pg/mg).
Our data for the first time provide the information on alteration of N-glycan profile in eyes with DR.
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