長期給予甲基乙二醛誘導 C57BL/6 小鼠視網膜損傷
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2023
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甲基乙二醛 (methylglyoxal, MGO)屬活性雙羰基化合物 (reactive dicarbonyl species, RCS)，為高度糖化終產物 (advanced glycation end products, AGEs)之前驅物，在體外可從日常飲食中獲得；在體內可經由糖解作用產生或透過視覺循環之副產物經代謝後生成。糖尿病患者長期處於高血糖狀態，其血液之MGO濃度顯著高於健康常人。已知MGO會促進AGEs生成，並活化AGE-RAGE signaling pathway，造成生物體氧化壓力與發炎反應，因此被認為可能是造成糖尿病視網膜病變的致病因子之一。據於此，本研究目的在於探討小鼠長期暴露於含MGO的飲食環境中，對於其視網膜是否會造成損傷效應。實驗選用七週齡C57BL/6雄性小鼠 (n = 24)，隨機分成健康控制組 (control group)、MGO組 (飲水中含1% MGO)，以及MGO + ALT-711組 (1 mg/kg body weight)，進行為期四十週的實驗。以hematoxylin and eosin (H&E) staining評估視網膜之組織病理變化；以免疫螢光染色 (immunofluorescence staining, IF)分析視網膜感光細胞、神經細胞活化、氧化壓力、發炎反應與AGE/RAGE等相關指標物的表現。結果顯示，長期給予MGO會降低小鼠視網膜組織外核層 (outer nuclear layer, ONL)、感光細胞內外段 (inner segment/outer segment, IS/OS)與內核層 (inner nuclear layer, INL)之厚度，並降低感光細胞之細胞核數，同時伴隨著視紫質 (rhodopsin)表現降低與膠質纖維酸性蛋白 (glial fibrillary acidic protein, GFAP)表現上升的現象。氧化壓力指標8-hydroxy-2-deoxyguanosine (8-OHdG)、促發炎細胞激素介白素1β (interleukin-1β, IL-1β )與腫瘤壞死因子 (tumor necrosis factor-α, TNF-α)於視網膜組織之表現，與控制組比較亦可見顯著上升的現象 (p < 0.05)；同時MGO主要代謝酵素乙二醛酶1 (glyoxalase-1, Glo-1)相較於控制組具有顯著降低的現象 (p< 0.05)。相反地，介入AGE抑制劑ALT-711後可減輕上述之負面效應。值得注意的是，MGO組之小鼠可見其視網膜組織有明顯Nδ -(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine (MG-H1)累積與RAGE活化的現象。綜合上述， MGO可能經由促進AGEs生成與RAGE表現，造成視網膜組織之氧化壓力及發炎反應，進而導致感光細胞損傷與Müller神經細胞活化。本研究結果指出MGO對於視網膜健康之可能負面效應，並提出MGO在糖尿病視網膜病變過程中的可能損傷機制，建議日常膳食中應避免攝取含高MGO之食物。
Methylglyoxal (MGO) is a reactive dicarbonyl species (RCS) and a precursor of advanced glycation end products (AGEs). MGO can be formed from glycolysis or via the metabolism of visual cycle byproducts. Additionally, MGO can be obtained through the consumption of food. Patients with diabetes have chronic hyperglycemia, and their blood MGO levels are significantly higher than those of healthy individuals. It is well known that MGO can stimulate the production of AGEs and activate the AGE-RAGE signaling pathway, resulting in oxidative stress and inflammatory responses. MGO is therefore regarded as one of the pathogenic factors in diabetic retinopathy. This study aims to investigate whether long-term exposure to MGO causes retinal damage in mice. Twenty-four male C57BL/6 mice were randomly assigned into three groups: the control group (control), the MGO group (1% MGO in drinking water), and the MGO + ALT-711 group (1 mg/kg b.w.). Hematoxylin and eosin staining was used to analyze the histopathological changes of retinal tissue; immunofluorescence staining was used to analyze the expressions of relevant indicators such as photoreceptors, Müller cell activation, oxidative stress, inflammation, and AGEs accumulation. The results showed that administration of MGO for 40 weeks decreased the thickness of the outer nuclear layer (ONL), inner segment/outer segment (IS/OS), and inner nuclear layer (INL) of retinal tissue in mice, while reducing the number of photoreceptor cell nuclei and the expression levels of rhodopsin, and increasing the expression levels of glial fibrillary acidic protein (GFAP). The expressions of 8-hydroxy-2-deoxyguanosine (8-OHdG), IL-1β, and TNF-α increased significantly in the MGO group when compared to the control group (p< 0.05). On the contrary, the expression levels of glyoxalase-1 in the MGO group were significantly lower than in the control group (p < 0.05). The intervention of ALT-711, an AGE inhibitor, could alleviate these adverse effects. Notably, the mice in the MGO group showed accumulation of Nδ -(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine (MG-H1) and activation of receptor for advanced glycation end products (RAGE) in the retina. In conclusion, this study indicates that long-term administration ofMGO causes retinal damage in mice, with the possible mechanism involving AGE/RAGE-induced oxidative stress and inflammation. Our study sheds lights on the potential impact of MGO on the progression of diabetic retinopathy and suggests avoiding foods high in MGO to preserve retinal health.
Methylglyoxal (MGO) is a reactive dicarbonyl species (RCS) and a precursor of advanced glycation end products (AGEs). MGO can be formed from glycolysis or via the metabolism of visual cycle byproducts. Additionally, MGO can be obtained through the consumption of food. Patients with diabetes have chronic hyperglycemia, and their blood MGO levels are significantly higher than those of healthy individuals. It is well known that MGO can stimulate the production of AGEs and activate the AGE-RAGE signaling pathway, resulting in oxidative stress and inflammatory responses. MGO is therefore regarded as one of the pathogenic factors in diabetic retinopathy. This study aims to investigate whether long-term exposure to MGO causes retinal damage in mice. Twenty-four male C57BL/6 mice were randomly assigned into three groups: the control group (control), the MGO group (1% MGO in drinking water), and the MGO + ALT-711 group (1 mg/kg b.w.). Hematoxylin and eosin staining was used to analyze the histopathological changes of retinal tissue; immunofluorescence staining was used to analyze the expressions of relevant indicators such as photoreceptors, Müller cell activation, oxidative stress, inflammation, and AGEs accumulation. The results showed that administration of MGO for 40 weeks decreased the thickness of the outer nuclear layer (ONL), inner segment/outer segment (IS/OS), and inner nuclear layer (INL) of retinal tissue in mice, while reducing the number of photoreceptor cell nuclei and the expression levels of rhodopsin, and increasing the expression levels of glial fibrillary acidic protein (GFAP). The expressions of 8-hydroxy-2-deoxyguanosine (8-OHdG), IL-1β, and TNF-α increased significantly in the MGO group when compared to the control group (p< 0.05). On the contrary, the expression levels of glyoxalase-1 in the MGO group were significantly lower than in the control group (p < 0.05). The intervention of ALT-711, an AGE inhibitor, could alleviate these adverse effects. Notably, the mice in the MGO group showed accumulation of Nδ -(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine (MG-H1) and activation of receptor for advanced glycation end products (RAGE) in the retina. In conclusion, this study indicates that long-term administration ofMGO causes retinal damage in mice, with the possible mechanism involving AGE/RAGE-induced oxidative stress and inflammation. Our study sheds lights on the potential impact of MGO on the progression of diabetic retinopathy and suggests avoiding foods high in MGO to preserve retinal health.
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甲基乙二醛, 視網膜, 高度糖化終產物, 高度糖化終產物受器, 氧化壓力, 發炎反應, methylglyoxal, retina, advanced glycation end products, receptor for advanced glycation end products, oxidative stress, inflammation