The effect of tetrahydrobiopterin (BH4) on diabetic nephropathy

四氢生物蝶呤（BH4）对糖尿病肾病的作用

基本信息

批准号：
13670827
负责人：
SHINTAKU Haruo
金额：
$ 1.22万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Nitric oxide synthase (NOS) requires tetrahydrobiopterin (BH4) as a coenzyme. Recent works showed that NOS activity is regulated in a BH4-dependent manner. Nitric oxide (NO) synthesis and metabolism are impaired in blood vessels of diabetic subjects. The concentration of BH4 is low in diabetic rats, probably contributing to endothelial dysfunction. If diabetic kidneys had such deficiency, it might cause nephropathy. The object of this research was to clarify anti-nephropathic effects of BH4 in diabetes meritus.We studied in streptozotocin (STZ) induced diabetic rats as a model of type 1 diabetes. Spargue-Dawley rats were divided by three groups, Control, STZ, STZ+BH4. BH4 was administered orally at 20mg/kg BW daily. STZ group had albuminuria at 9-week, and developed diabetic nephropathy until 14-week. But STZ+BH4 group did not develop during experiment. The renal expression of eNOS was decreased in STZ group, and this decrease was restored in STZ+BH4 group.We set out to find if the BH4 … More level in kidneys is low and, if so, whether it is involved in proteinuria. We used Otsuka Long-Evans Tokushima Fatty (OLETF) rats, with a model of type 2 diabetes, and used Long-Evans Tokushima Otsuka (LETO) rats as healthy controls. OLETF rats were put into groups with or without daily oral doses of BH4 (10 mg/kg) during the study. We obtained plasma, red blood cells, and kidneys from 62-week-old rats and measured BH4, total biopterin, and GTP cyclohydrolase I activity, the key enzyme of de novo BH4 synthesis. We measured urinary protein excretion in the rats at 13, 37, or 61 weeks of age as a marker of nephropathy and stained their kidneys with anti-eNOS antibodies with an immunofluorescent method. Plasma and renal levels of BH4 and biopterin were lower in diabetic rats than in controls. GTP cyclohydrolase activity of red blood cells and renal tissue from diabetic rats was less than that of controls. The BH4/biopterin ratio was smaller in the diabetic rats, suggesting that dihydropteridine reductase, which recycles BH4 from inactive BH2, has low activity in diabetes. Urinary protein was greater in diabetic rats at 13 weeks than in controls ; the difference increased with age. BH4 suppressed proteinuria in diabetic rats at 37 and 61 weeks without affecting body weight, plasma glucose, or blood pressure. Diabetic kidneys had less fluorescence from anti-eNOS antibodies than control kidneys, unless BH4 was given. In this model of diabetes, little BH4 was synthesized, apparently because of GTP cyclohydrolase and dihydropteridine reductase activities were low. Deficiencies of BH4 and of the eNOS-NO system may contribute to the progression of diabetic nephropathy. These results suggest that BH4 seems to have anti-nephropathic effects and may preYent progress of diabetic nephropathy. Less

一氧化氮合酶（NOS）需要四氢无菌蛋白酶（BH4）作为辅酶。最近的作品表明，NOS活性以BH4依赖性方式调节。一氧化氮（NO）合成和代谢在糖尿病受试者的血管中受损。 BH4的浓度低糖尿病大鼠，可能导致内皮功能障碍。如果糖尿病性肾脏缺乏症状，可能会导致肾病。这项研究的目的是阐明BH4在糖尿病的疾病中。我们在链霉菌素（STZ）诱导的糖尿病大鼠中研究是1型糖尿病的模型。 Spargue-Dawley大鼠由三组，Control，STZ，STZ+BH4划分。 BH4每天以20mg/kg BW口服。 STZ组为9周的蛋白尿，并患上糖尿病性肾病直到14周。但是STZ+BH4组在实验过程中没有发展。 STZ组的肾脏表达降低，并且在STZ+BH4组中恢复了这种下降。我们着手发现BH4是否……肾脏中的更多水平很低，如果是的，是否参与蛋白尿。我们使用了2型糖尿病的大鼠大鼠Otsuka Longevans Tokushima Fatty（OLETF）大鼠，并使用了Longevans Tokushima Otsuka（Leto）大鼠作为健康的对照。在研究期间，将OLETF大鼠分组为有或没有每天口服剂量的BH4（10 mg/kg）。我们从62周大的大鼠中获得了血浆，红细胞和肾脏，并测量了BH4，总生物蛋白和GTP环氢酶I活性，这是NOVO BH4合成的关键酶。我们在13、37或61周龄的大鼠中测量了肾病的标记，并用抗ENOS抗体染色肾脏，并用免疫荧光方法染色。糖尿病大鼠的BH4和生物蛋白的血浆和肾脏水平低于对照组。糖尿病大鼠的红细胞和肾脏组织的GTP环氢酶活性小于对照。在糖尿病大鼠中，BH4/Biopterin的比率较小，这表明从无效BH2中回收BH4的二氢二肽酶在糖尿病中的活性较低。 13周的糖尿病大鼠的尿蛋白比对照组大。差异随着年龄的增长而增加。 BH4在37和61周时抑制糖尿病大鼠的蛋白尿，而不会影响体重，血浆葡萄糖或血压。除非给予BH4，否则抗ENOS抗体的糖尿病肾脏的荧光较少。在这种糖尿病模型中，小BH4被合成，显然是由于GTP环氢化氢酶和二氢吡啶还原活性较低。 BH4和ENOS-NO系统的缺陷可能有助于糖尿病性肾病的发展。这些结果表明，BH4似乎具有抗氯性作用，并且可能会导致糖尿病性肾病的进展。