Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
Unit of Endocrinology, Diabetes and Metabolism, S. Giovanni Calibita Fatebenefratelli Hospital, Rome, Italy.
Endocrine. 2019 Sep;65(3):542-549. doi: 10.1007/s12020-019-02017-5. Epub 2019 Jul 20.
In the earliest stages of diabetic retinopathy (DR), a dysfunction of Müller cells, characterized by high levels of glial fibrillary acidic protein (GFAP), and aquaporins (AQP), has been observed. Although chronic hyperglycemia causes the activation of Müller cells, the effect of glycemic fluctuations is yet unknown. The aim of the study was to analyze the impact of glucose variability on rat retinal Müller cells (rMC-1) adapted to either normal (5 mM) or high (25 mM) glucose levels.
rMC-1 were cultured in a medium containing either 5 mM (N cells) or 25 mM of glucose (H cells) and then incubated for 96 h in a medium containing (a) low glucose (either 1-3 or 5 mM), (b) basal glucose (either 5 or 25 mM), (c) high glucose (either 25 or 45 mM), (d) basal and high glucose alternated every 24 h; (e) low- and high glucose alternated every 24 h; (f) basal glucose with episodes of low glucose for 30 min twice a day. Müller cells activation was evaluated by measuring the levels of GFAP, AQP4, and phospho-active extracellular signal-regulated kinase (pERK).
Under both basal and high glucose concentrations rMC-1 were viable, but their response to glucose excursions was different. In N cells kept under normal (5 mM) glucose, a significant glial activation was measured not only in response to constant high glucose but also to alternating low/high glucose. In H cells, adapted to 25 mM glucose, a significant response was observed only after exposition to a lower (5 mM) glucose concentration.
Our results highlight Müller cells activation in response to glucose variability and a different susceptibility depending on the basal glucose conditions.
在糖尿病视网膜病变（DR）的早期阶段，已经观察到 Müller 细胞功能障碍，其特征是神经胶质纤维酸性蛋白（GFAP）和水通道蛋白（AQP）水平升高。虽然慢性高血糖会导致 Müller 细胞激活，但血糖波动的影响尚不清楚。本研究旨在分析葡萄糖变异性对适应正常（5mM）或高（25mM）葡萄糖水平的大鼠视网膜 Müller 细胞（rMC-1）的影响。
rMC-1 在含有 5mM（N 细胞）或 25mM 葡萄糖的培养基中培养，然后在含有（a）低葡萄糖（1-3 或 5mM）、（b）基础葡萄糖（5 或 25mM）、（c）高葡萄糖（25 或 45mM）、（d）基础和高葡萄糖每 24 小时交替、（e）低和高葡萄糖每 24 小时交替、（f）基础葡萄糖每天两次低葡萄糖 30 分钟的培养基中孵育 96 小时。通过测量 GFAP、AQP4 和磷酸化细胞外信号调节激酶（pERK）的水平来评估 Müller 细胞的激活。
在基础和高葡萄糖浓度下，rMC-1 均存活，但它们对葡萄糖波动的反应不同。在保持在正常（5mM）葡萄糖下的 N 细胞中，不仅在持续高葡萄糖下，而且在交替低/高葡萄糖下，均测量到明显的神经胶质激活。在适应 25mM 葡萄糖的 H 细胞中，仅在暴露于较低（5mM）葡萄糖浓度后才观察到明显的反应。
我们的结果强调了 Müller 细胞对葡萄糖变异性的激活以及对基础葡萄糖条件的不同敏感性。
