Biochemistry Division, National Institute of Nutrition, Hyderabad, India.
Shiley Eye Institute, University of California San Diego, La Jolla, CA, USA.
Arch Biochem Biophys. 2020 Jan 15;679:108207. doi: 10.1016/j.abb.2019.108207. Epub 2019 Nov 21.
Obesity is a global health problem associated with several diseases including ocular complications. Earlier we reported progressive retinal degeneration because of obesity in a spontaneous obese rat (WNIN/Ob) model. In the current study, we examined the molecular mechanisms leading to retinal degeneration in WNIN/Ob rat.
Sorbitol was estimated by the fluorometric method in the retina of WNIN/Ob rats at different age (3-, 6- and 12- months), along with their respective lean rats. Immunoblotting was performed in the retina to assess the status of the insulin signaling pathway, ER stress and cellular stress (p38MAPK and ERK1/2). Human SK-N-SH cells were treated with 0.5 and 1.0 M sorbitol for 30 min to study insulin signaling, ER stress, and cellular stress. TUNEL assay was done to measure apoptosis. The retinal function in the rats was determined by electroretinogram.
A gradual but significantly higher intracellular sorbitol accumulation was observed in the retina of obese rats from 3- to 12-months. The cellular osmotic stress has activated the insulin signaling mechanism without activating AKT and also triggered ER stress. Both the stresses activated the ERK and p38MAPK signaling causing apoptosis in the retina leading to retinal degeneration. Retinal dysfunction was confirmed by altered scotopic and photopic electroretinogram responses. These in vivo results were mimicked in SK-N-SH cells when exposed to sorbitol in vitro.
These results suggest cellular stress due to sorbitol accumulation impairing the ER function, thereby leading to progressive retinal degeneration under obese conditions.
肥胖是一个全球性的健康问题，与多种疾病有关，包括眼部并发症。我们之前报道过一种自发性肥胖大鼠（WNIN/Ob）模型中由于肥胖导致的进行性视网膜变性。在本研究中，我们研究了导致 WNIN/Ob 大鼠视网膜变性的分子机制。
在不同年龄（3、6 和 12 个月）的 WNIN/Ob 大鼠和相应的瘦大鼠的视网膜中，通过荧光法估计山梨醇的含量。在视网膜中进行免疫印迹，以评估胰岛素信号通路、内质网应激和细胞应激（p38MAPK 和 ERK1/2）的状态。用人 SK-N-SH 细胞用 0.5 和 1.0 M 山梨醇处理 30 分钟，以研究胰岛素信号、内质网应激和细胞应激。用 TUNEL 测定法测量细胞凋亡。通过视网膜电图测定大鼠的视网膜功能。
从 3 个月到 12 个月，肥胖大鼠视网膜中逐渐但显著升高的细胞内山梨醇积累。细胞渗透应激激活了胰岛素信号机制，而没有激活 AKT，也触发了内质网应激。两种应激都激活了 ERK 和 p38MAPK 信号，导致视网膜细胞凋亡，从而导致视网膜变性。视网膜功能障碍通过改变暗适应和明适应视网膜电图反应得到证实。这些体内结果在 SK-N-SH 细胞中被山梨醇体外暴露所模拟。
这些结果表明，由于山梨醇积累导致的细胞应激，破坏了内质网的功能，从而导致肥胖条件下进行性视网膜变性。
