Analysis of glucose metabolism in diabetic rat retinas
Analysis of glucose metabolism in diabetic rat retinas
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DOI：
10.1152/ajpendo.00323.2005
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发表时间：
2006-06-01
影响因子：
5.1
通讯作者：
LaNoue, Kathryn F.
中科院分区：
文献类型：
--
作者：
Ola, M. Shamsul;Berkich, Deborah A.;LaNoue, Kathryn F.
本研究旨在了解高血糖和糖尿病视网膜病变之间的因果关系。大量研究表明，高血糖导致糖尿病视网膜氧化应激，但产生氧化应激的机制尚未得到解决。线粒体电子传递链上的电子压力增加、胞质NADH生成增加和细胞NADPH减少都被认为是活性氧和一氧化二氮的可能来源。在本研究中，将对照组和糖尿病大鼠的离体视网膜暴露于正常血糖和高血糖条件下。采用微波辐射淬灭技术研究糖尿病大鼠视网膜在体内，葡萄糖，葡萄糖衍生的代谢产物，和NADH氧化/还原状态的测定。研究离体视网膜，糖酵解通量，乳酸生产，和三羧酸循环通量进行了评估。酶法测定的葡萄糖6-磷酸和果糖6-磷酸仅轻微升高高血糖症和/或糖尿病，但多元醇显着增加。细胞溶质NADH-NAD比不升高高血糖症，也没有糖尿病在体内或体外。三羧酸循环通量没有增加糖尿病状态，也没有高血糖症。另一方面，观察到糖酵解通量的小幅增加与高血糖症，但糖酵解通量总是低于糖尿病与对照组动物。观察到的甘油醛-3-磷酸脱氢酶活性的降低可能是糖尿病大鼠视网膜糖酵解通量缓慢的部分原因。因此，可以得出结论，葡萄糖代谢，下游的己糖激酶，不升高高血糖症或糖尿病。葡萄糖上游的代谢产物，如山梨醇途径（降低NADPH）和多元醇合成增加。
This study was conceived in an effort to understand cause and effect relationships between hyperglycemia and diabetic retinopathy. Numerous studies show that hyperglycemia leads to oxidative stress in the diabetic retinas, but the mechanisms that generate oxidative stress have not been resolved. Increased electron pressure on the mitochondrial electron transfer chain, increased generation of cytosolic NADH, and decreases in cellular NADPH have all been cited as possible sources of reactive oxygen species and nitrous oxide. In the present study, excised retinas from control and diabetic rats were exposed to euglycemic and hyperglycemic conditions. Using a microwave irradiation quenching technique to study retinas of diabetic rats in vivo, glucose, glucose-derived metabolites, and NADH oxidation/reduction status were measured. Studying excised retinas in vitro, glycolytic flux, lactate production, and tricarboxylic acid cycle flux were evaluated. Enzymatically assayed glucose 6-phosphate and fructose 6-phosphate were only slightly elevated by hyperglycemia and/or diabetes, but polyols were increased dramatically. Cytosolic NADH-to-NAD ratios were not elevated by hyperglycemia nor by diabetes in vivo or in vitro. Tricarboxylic acid cycle flux was not increased by the diabetic state nor by hyperglycemia. On the other hand, small increases in glycolytic flux were observed with hyperglycemia, but glycolytic flux was always lower in diabetic compared with control animals. An observed decrease in activity of glyceraldehyde-3-phosphate dehydrogenase may be partially responsible for slow glycolytic flux for retinas of diabetic rats. Therefore, it is concluded that glucose metabolism, downstream of hexokinase, is not elevated by hyperglycemia or diabetes. Metabolites upstream of glucose such as the sorbitol pathway (which decreases NADPH) and polyol synthesis are increased.