Transketolase Activity but not Thiamine Membrane Transport Change in Response to Hyperglycaemia and Kidney Dysfunction
Transketolase Activity but not Thiamine Membrane Transport Change in Response to Hyperglycaemia and Kidney Dysfunction
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DOI：
10.1055/s-0043-115009
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发表时间：
2018-04-01
影响因子：
1.8
通讯作者：
Kankova, Katerina
中科院分区：
文献类型：
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作者：
Chalasova, Katarina;Pacal, Lukas;Kankova, Katerina
目的磷酸戊糖途径（PPP）及其关键酶转酮醇酶（TKT）可能是高脂血症的保护机制。糖尿病肾病（DKD）是1型和2型糖尿病的常见并发症，与显著的发病率和死亡率相关，是慢性肾病（CKD）的最常见原因。我们推测，PPP在糖尿病中的保护作用，以及最终在伴随的DKD中更严重的保护作用，可能受到活性TKT辅因子二磷酸硫胺素（TDP）有限的细胞内可用性的影响。方法使用与糖尿病相关的人类细胞系，在体外研究高血糖对关键PPP位点基因表达和蛋白水平的影响（HUVEC和HRGEC）和（连同TKT活性的测量，肾功能相当的糖尿病受试者与非糖尿病受试者的体内血浆硫胺素和红细胞TDP浓度结果高脂血症组RFC-1、THTR 1、THTR 2和TKT蛋白表达水平明显低于正常对照组（P <0. 05）。对CKD伴糖尿病和不伴糖尿病患者以及对照组的血液样本进行分析，未发现硫胺素转运蛋白的基因表达和蛋白水平存在任何差异，而红细胞中的TKT活性和TDP逐渐增加，其中糖尿病和非糖尿病病因的CKD 3 -4患者的肾功能下降最高。结论体外实验和人体实验均显示，高脂血症诱导的细胞内硫胺素转运体表达降低或无变化，而伴或不伴糖尿病的CKD患者TKT活性与细胞内TDP水平平行升高。因此，缺乏硫胺素跨膜转运的适应性增加允许TKT活性的进一步增加可能有助于糖尿病和CKD中PPP功能受损以及糖毒性损伤的发展。
Aim Pentose phosphate pathway (PPP) with key enzyme transketolase (TKT), represents a potentially 'protective' mechanism in hyperglycaemia. Diabetic kidney disease (DKD), a common complication of both type 1 and type 2 diabetes associated with significant morbidity and mortality, represents the most common cause of chronic kidney disease (CKD). We hypothesized that protective PPP action in diabetes and eventually even more severely in concomitant DKD might be compromised by limited intracellular availability of an active TKT cofactor thiamine diphosphate (TDP).Methods Effect of hyperglycaemia on gene expression and protein levels of key PPP loci was studied in vitro using human cell lines relevant to diabetes (HUVEC and HRGEC) and (together with measurement of TKT activity, plasma thiamine and erythrocyte TDP concentration) in vivo in diabetic vs. non-diabetic subjects with comparable renal function (n = 83 in total).Results Hyperglycaemia significantly decreased protein levels of RFC-1, THTR1, THTR2 and TKT (P < 0.05) in vitro. Analysis of blood samples from CKD patients with and without diabetes and from controls did not reveal any difference in gene expression and protein levels of thiamine transporters while TKT activity and TDP in erythrocytes gradually increased with decreasing kidney function being highest in patients with CKD3-4 of both diabetic and non-diabetic aetiology. Hyperglycaemia and uremic serum mimicking CKD in diabetes did not affect TKT activity in vitro (P < 0.05).Conclusion Both in vitro and human experiments showed decrease or unchanged expression, respectively, of thiamine transporters induced by hyperglycaemia while TKT activity in parallel with intracellular TDP was increased in CKD patients with or without diabetes. Therefore, lack of adaptive increase of thiamine transmembrane transport allowing further increase of TKT activity might contribute to compromised PPP function in diabetes and CKD and to the development of glycotoxic injury.