Effects of asymmetric dimethylarginine on renal arteries in portal hypertension and cirrhosis

AIM To evaluate the effects of asymmetric dimethylarginine(ADMA) in renal arteries from portal hypertensive and cirrhotic rats.METHODS Rat renal arteries from Sham(n = 15), pre-hepatic portal hypertension(PPVL; n = 15) and bile duct ligation and excision-induced cirrhosis(BDL; n = 15) were precontracted with norepinephrine, and additional contractions were induced with ADMA(10-6-10-3 mol/L), an endogenous inhibitor of nitric oxide(NO) synthase. Concentration-response curves to acetylcholine(1 × 10-9~(-3) × 10~(-6) mol/L) were determined in precontractedrenal artery segments with norepinephrine in the absence and in the presence of ADMA. Kidneys were collected to determine the protein expression and activity of dimethylarginine dimethylaminohydrolase(DDAH), an enzyme that catabolizes ADMA. RESULTS In renal arteries precontracted with norepinephrine, ADMA caused endothelium-dependent contractions. The pD 2 values to ADMA were similar in the Sham and PPVL groups(4.20 ± 0.08 and 4.11 ± 0.09, P 0.05, respectively), but were lower than those of the BDL group(4.79 ± 0.16, P 0.05). Acetylcholine-induced endothelium-dependent relaxation that did not differ, in terms of p D2 and maximal relaxation, among the 3 groups studied. Treatment with ADMA(3 × 10~(-4) mol/L) inhibited acetylcholine-induced relaxation in the 3 groups, but the inhibition was higher(P 0.05) in the BDL group compared with that for the Sham and PPVL groups. The m RNA and protein expression of DDAH-1 were similar in kidneys from the three groups. Conversely, DDAH-2 expression was increased(P 0.05) in PPVL and further enhanced(P 0.05) in the BDL group. However, renal DDAH activity was significantly decreased in the BDL group. CONCLUSION Cirrhosis increased the inhibitory effect of ADMA on basal- and induced-release of NO in renal arteries, and decreased DDAH activity in the kidney.     

Antidiabetic drug metformin is effective on the metabolism of asymmetric dimethylarginine in experimental liver injury

AimsWe aimed to investigate the pharmacological efficiency of metformin on asymmetric dimethylarginine (ADMA) metabolism in inflammation caused by the lipopolysaccharide (LPS)/d-galactosamine (d-GalN) treatment.MethodsAdult Sprague-Dawley rats were injected LPS/d-GalN intraperitoneally. One half of the animals was injected metformin (250 mg kg⁻¹ body mass for one week) prior to LPS/d-GalN treatment. Six hours after the LPS/d-GalN injection, livers were removed, and used for the measurements of dimethylarginine dimethylaminohydrolase (DDAH) and myeloperoxidase (MPO) activities, glutathione (GSH), ADMA and arginine levels. Liver tissues were examined histopathologically. The Kruskal–Wallis (posthoc Mann–Whitney U) test was used for the statistics.LPS/d-GalN injections caused liver injury as evidenced by the activities of aminotransferases and arginase. GSH level and DDAH activity were decreased in the liver. Metformin pretreatment alleviated the activity of serum enzymes, and attenuated histopathological lesions caused by LPS/d-GalN injections. LPS/d-GalN-induced inflammation, as confirmed by the increased MPO activity, created an asymmetrical distribution of arginine and ADMA between the tissue and plasma. Metformin decreased tissue ADMA level while it restored the DDAH activity and GSH.ConclusionOur findings showed that metformin administration for one week has a potency to protect liver through regulating ADMA metabolism in LPS/d-GalN-induced injury.     

非对称性二甲基精氨酸与糖尿病脑血管病变

一氧化氮(nitric oxide,NO)是已知最重要的内源性血管舒张因子.内皮型一氧化氮合酶(nitric oxide and enzyme,NOS)的竞争性抑制剂非对称性二甲基精氨酸(asymmetric dimethylarginine,ADMA)可抑制NO的合成,使NO/NOS通路发生障碍,NO合成减少.近年来的研究表明,ADMA与糖尿病脑血管病变的发生和发展有关,为进一步明确该病的发生机制提供了新的见解.     

Estradiol,acting through estrogen receptor alpha,restores dimethylarginine dimethylaminohydrolase activity and nitric oxide production in oxLDL-treated human arterial endothelial cells

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. ADMA accumulation, mainly due to a decreased dimethylarginine dimethylaminohydrolase (DDAH) activity, has been related to the development of cardiovascular diseases. We investigate whether estradiol prevents the changes induced by oxidized low density lipoprotein (oxLDL) on the DDAH/ADMA/NO pathway in human umbilical artery endothelial cells (HUAEC). HUAEC were exposed to estradiol, native LDL (nLDL), oxLDL and their combinations for 24 h. In some experiments, cells were also exposed to the unspecific estrogen receptor (ER) antagonist ICI 182780, the specific ERα antagonist MPP or specific agonists for ERα, ERβ and GPER. ADMA concentration was measured by HPLC and concentration of NO by amperometry. Protein expression and DDAH activity were measured by immunoblotting and an enzymatic method, respectively. oxLDL, but not nLDL, increased ADMA concentration with a concomitant decrease on DDAH activity. oxLDL reduced eNOS protein and NO production. Estradiol alone had no effects on DDAH/ADMA/NO pathway, but increased the attenuated endothelial NO production induced by oxLDL by reduction in ADMA and preventing loss of eNOS protein levels. ICI 182780 and MPP completely abolished these effects of estradiol on oxLDL-exposed cells. ERα agonist, but not ERβ and GPER agonists, mirrored estradiol effects on NO production. In conclusion, estradiol restores (1) DDAH activity, and therefore ADMA levels, and (2) NO production impaired by oxLDL in HUAEC acting through ERα.     

Changes in Serum Asymmetric Dimethylarginine and Endothelial Markers Levels With Varying Periods of Hemodialysis

Asymmetric dimethylarginine (ADMA) as a uremia toxin is accumulated in end‐stage renal disease (ESRD) patients. Elevated ADMA level has been shown to be predictive of cardiovascular diseases (CVDs) and all‐cause mortality in ESRD. Therefore, we investigated the effect of prolonged hemodialysis (HD) treatment on the levels of serum ADMA, arginine, nitric oxide (NO), soluble intercellular adhesion molecule‐1 (sICAM‐1) and soluble vascular cell adhesion molecule‐1 (sVCAM‐1). Seventy‐five patients (M/F = 40/35) with chronic renal failure (CRF) and who were on HD were divided into five groups with differing treatment periods of HD; from 6 to 24 months to 97–120 months. Fifteen apparently healthy subjects acted as controls. The serum levels of ADMA, sICAM‐1 and sVCAM‐1 were increased in all patient groups compared to the control group. No significant difference was observed when the patient groups were compared in terms of HD treatment periods. Nitric oxide levels were lower in the three groups who were treated for periods of 49–72, 73–96, 97–120 months compared to the control group. The L‐arginine to ADMA ratio was decreased in all patient groups compared to controls. Consequently, our investigations have shown that in HD continued for more than 4 years NO levels began to decrease significantly and the levels of serum ADMA, sICAM‐1 and sVCAM‐1 levels increased although this increase was not affected by the period in which hemodialysis treatment was applied.     

非对称性二甲基精氨酸与血管内皮功能

非对称性二甲基精氨酸是内源性一氧化氮合酶抑制剂,研究表明,非对称性二甲基精氨酸与血管内皮功能失调密切相关,血浆中非对称性二甲基精氨酸水平的升高是内皮功能失调的新的危险因子。     

糖尿病患者血浆一氧化氮水平与血流动力学变化关系的研究

目的研究ＮＯ在ＤＭ患者血管并发症中的作用。方法高效液相色谱测定７４例ＤＭ病人和３０例正常人血浆ＮＯ水平，同时测定甲襞微循环血流及经颅多普勒血流。结果糖尿病组血浆ＮＯ水平明显低于对照组（Ｐ＜００１），随着血管并发症的增多，血浆ＮＯ的水平也随之降低；甲襞微循环总积分ＤＭＭ组较对照组增高（Ｐ＜００１），血流速度明显减慢（Ｐ＜００１），颅底动脉血流速度明显高于对照组（Ｐ＜００１）；ＤＭ病人血浆ＮＯ与微循环血流速度呈直线正相关，ＮＯ与颅底动脉血流速度呈负相关。结论ＮＯ可影响ＤＭ病人的血液动力学变化，其水平的高低在一定程度上反映了ＤＭ及血管损伤的程度。     

Liver plays a central role in asymmetric dimethylargininemediated organ injury

Asymmetric-dimethylarginine(ADMA) competes with L-arginine for each of the three isoforms of nitric oxide synthase:endothelial;neuronal;inducible.ADMA is synthesized by protein methyltransferases followed by proteolytic degradation.ADMA is metabolized to citrulline and dimethylamine,by dimethylarginine dimethylaminohydrolase(DDAH) and enters cells through cationic amino-acid transporters extensively expressed in the liver.The liver plays a crucial role in ADMA metabolism by DDAH-1 and,as has been recently demonstrated,it is also responsible for ADMA biliary excretion.A correlation has been demonstrated between plasma ADMA levels and the degree of hepatic dysfunction in patients suffering from liver diseases with varying aetiologies:plasma ADMA levels are increased in patients with liver cirrhosis,alcoholic hepatitis and acute liver failure.The mechanism by which liver dysfunction results in raised ADMA concentrations is probably due to impaired activity of DDAH due to severe inflammation,oxidative stress,and direct damage to DDAH.High plasma ADMA levels are also relevant as they are associated with the onset of multiorgan failure(MOF).Increased plasma concentration of ADMA was identified as an independent risk factor for MOF in critically-ill patients causing enhanced Intensive Care Unit mortality:a significant reduction in nitric oxide synthesis,leading to malperfusion in various organs,eventually culminating in multi organs dysfunction.     

一氧化氮在2型糖尿病发病机制中的作用

在病理条件下,一氧化氮通过影响胰岛素信号系统转导途径中的重要的信号分子而导致外周组织胰岛素抵抗的形成,并通过介导脂质、细胞因子及高糖所致的胰岛β细胞功能障碍,而在 2型糖尿病的发病中发挥了重要作用。     

老年2型糖尿病患者外向生长内皮细胞功能的变化

目的 探讨老年2型糖尿病患者外向生长内皮细胞(outgrowth endothelial cells,OEC)数量及功能的变化. 方法选取老年糖尿病患者(糖尿病组)30例及健康对照者(对照组)30例,受检者分别抽取外周血 20 ml,密度梯度离心法分离单个核细胞后于体外培养,并通过流式细胞仪测定CD14、CD34、CD45、CD105、CD133、血管内皮生长因子受体2(KDR)、血管性血友病因子(vWF)的表达情况;激光共聚焦鉴定OEC吞噬乙酰化低密度脂蛋白(ac-LDL)及结合荆豆凝集素(UEA-1)的能力;计数培养16 d形成的OEC集落数,取P1代细胞,分别采用噻唑兰(MTT)法、黏附能力测定实验和硝酸还原酶法测定两组OEC的增殖能力、黏附功能以及一氧化氮(NO)、一氧化氮合酶(NOS)的含量. 结果糖尿病组和对照组的OEC流式鉴定结果均为CD14和CD45阴性,CD133、CD34、CD105、KDR、vWF阳性,两组培养的OEC均町以吞噬ac-LDL并结合UEA-1;糖尿病组OEC集落数显著小于对照组[(2.20±1.13)CFU对(3.63±1.29)CFU,T=4.565,P<0.01];糖尿病组细胞增殖力[(0.307±0.031)A],较对照组[(0.484±0.070)A]减弱(t=11.519,P<0.01);糖尿病组细胞黏附功能[(37.74±8.37)个/HP],较对照组[(51.66±11.39)个/HP]减弱(t=5.513,P<0.01);糖尿病组合成NO[(273.40±49.85)μmol/L]和NOS能力((38.05±8.68)U/m1],均较对照组((362.23±49.88)μmol/L和(51.61±10.29)U/ml]显著降低(t=6.894,5.535,均P< 0.01). 结论老年糖尿病患者外向生长内皮细胞数量和功能均下降.     

eNOS基因5''''-侧翼区T-786→C突变与2型糖尿病患者内皮依赖性血管舒张功能的关系

目的 探讨2型糖尿病(T2DM)患者内皮一氧化氮合酶(eNOS)基因5'-侧翼区T-786→C突变与T2DM患者内皮依赖性血管舒张功能(EDD)关系.方法 选择无血管并发症的男性T2DM患者162例.采用PCR/ASO探针杂交技术检测eNOS基因5'-侧翼区T-786→C突变.采用高分辨超声检测肱动脉血流介导的EDD.结果 T/C或C/C组EDD为3.73%±0.50%,明显低于T/T组(4.15%±0.49%)(P＜0.01).多元逐步分析结果显示,在所有T2DM患者中,EDD与C等位基因呈负相关(P=0.001).在吸烟者中,T/C或C/C组EDD明显低于T/T组(P＜0.05),在非吸烟者中则不然.多元逐步分析结果显示,在吸烟者中,C等位基因是EDD下降的独立危险因子(P＜0.01),在非吸烟者中则不然.结论 eNOS基因5'-侧翼区T-786→C突变是T2DM患者内皮功能异常的遗传危险因子,尤其是吸烟的T2DM患者.     

雷米普利对2型糖尿病患者一氧化氮和C反应蛋白的影响

目的　探讨 2型糖尿病患者血清一氧化氮 (NO)和C反应蛋白 (CRP)的变化及雷米普利对其影响。方法　 160例 2型糖尿病患者随机分为常规治疗组和雷米普利组 ,雷米普利组在常规治疗基础上加雷米普利治疗。用化学法和免疫比浊法测定治疗前及治疗 1、2、3、6月后血清NO和CRP ,以 75名正常人为对照。结果　糖尿病患者血清NO浓度显著低于正常人。而CRP浓度显著高于正常人。雷米普利组治疗 2月后NO浓度从 ( 9.2 4± 3 .43 ) μmol/L显著上升到 ( 10 .76± 3 .0 7) μmol/L ,3月后CRP从 ( 3 .3 6± 1.82 )mg/L显著下降到 ( 2 .72± 1.63 )mg/L ;常规治疗组 6个月观察期内NO和CRP无明显变化。结论　 2型糖尿病患者存在着血管内皮功能受损和动脉壁的慢性炎症反应 ,雷米普利减轻了这种内皮功能受损和慢性炎症反应。     

小檗碱对糖尿病大鼠外周神经功能及神经病理性痛的影响

目的探讨小檗碱(Berberine,Ber)对糖尿病(DM)大鼠外周神经功能和神经病理性痛的影响及其作用机制。方法以链脲佐菌素(STZ)腹腔注射诱导形成DM模型,随机分成对照组、模型组和Ber组,其中Ber组给予187.5 mg/kg的Ber灌胃。用机械刺激法、热板法,分别测缩足反应阈值(MWT)、热痛阈值(HPT);电刺激诱导动作电位法测定坐骨神经传导速度(NCV);光镜观察脊髓组织形态学改变;用硝酸还原法、化学比色法测定一氧化氮(NO)、一氧化氮合酶(NOS)含量或活性。结果 DM大鼠MWT、HPT均明显降低(P<0.01),坐骨神经NCV明显减慢(P<0.05),脊髓背角萎缩,神经元变性坏死,核仁消失,尼氏小体消失,Ber组则明显恢复;DM大鼠血清、坐骨神经NO、NOS均明显减少(P<0.01),Ber组则明显升高(P<0.05)。结论 Ber能减轻DM大鼠神经病理性疼痛症状,维持外周神经的结构和功能,这种作用与其增加NOS活性,促进NO的合成和释放,抑制NO的灭活有关。     

Asymmetric dimethylarginine as a mediator of vascular dysfunction in cirrhosis

Cirrhosis is associated with marked abnormalities in the circulatory function that involve a reduction in systemic vascular resistance. An important cause of this vasodilatation is the increased production or activity of nitric oxide (NO) in the splanchnic circulation. During portal hypertension and cirrhosis an increased endothelial NO synthase (eNOS) activity is demonstrated in splanchnic vessels. In contrast, the activity of eNOS in the cirrhotic liver is decreased, which suggests a different regulation of eNOS in the liver and in the splanchnic vessels. Asymmetric dimethylarginine (ADMA) is an endogenous NO inhibitor and higher plasma levels of ADMA are related to increased cardiovascular risk in both the general population and among patients with cirrhosis. It has been demonstrated that the liver is a key player in the metabolism of ADMA. This observation was further supported by investigations in human patients, showing a close correlation between ADMA plasma levels and the degree of hepatic dysfunction. ADMA is degraded to citrulline and dimethylamine by dimethylarginine dimethylaminohydrolases (DDAHs). DDAHs are expressed as type 1 and 2 isoforms and are widely distributed in various organs and tissues, including the liver. In this review, we discuss experimental and clinical data that document the effects of dimethylarginines on vascular function in cirrhosis. Our increasing understanding of the routes of synthesis and metabolism of methylarginines is beginning to provide insights into novel mechanisms of liver disease and allowing us to identify potential therapeutic opportunities.     

空腹高血糖对2型糖尿病患者精氨酸刺激试验的影响

目的探讨2型糖尿病(T2DM)血糖水平与胰岛素释放的关系,以了解葡萄糖毒性对胰岛β细胞分泌功能的影响。方法观察146例T2DM患者精氨酸刺激后真胰岛素(TI)、胰岛素原(PI)水平的变化。以胰岛素抵抗(IR)指数作为估测IR的简易参数,并比较T2DM患者在不同FPG状态下,胰岛素分泌减退的检出率的差异。结果(1)T2DM主要表现为IR伴胰岛素分泌不足。(2)比较不同FPG水平T2DM人群中精氨酸刺激后胰岛素分泌减退的检出率:当FPG≥11mmol/L时其检出率明显增加,提示高浓度葡萄糖抑制胰岛素分泌功能的阈值可能在11mmol/L左右。结论葡萄糖毒性作用干扰对β细胞分泌功能的判断,因此,在临床上将T2DM患者的FPG控制在11mmol/L以下进行精氨酸刺激试验,能较为确切地反映其真正的胰岛β细胞功能。     

2型糖尿病合并高血压患者血清NO、NOS水平的研究

目的　通过对 2型糖尿病 (2 - DM)合并高血压 (EH)患者血清一氧化氮 (NO)、一氧化氮合酶 (NOS)的测定 ,探讨其在 2 - DM合并 EH发生发展中的意义。方法　设正常对照组、单纯 2 - DM组和 2 - DM合并 EH组 ,分别测定血糖、胰岛素、血脂、NO及 NOS。结果　 2 - DM合并 EH组空腹胰岛素 (FINS)、舒张压 (DBP)和收缩压 (SBP)等均显著高于单纯 2 - DM组和正常对照组 ;胰岛素敏感指数 (ISI)和 NO均显著低于其他两组。相关分析显示 NO与 FINS和血压呈明显负相关 ,与 ISI呈显著正相关。结论　血清中 NO含量与胰岛素抵抗和血压密切相关 ,2 - DM患者血清 NO水平的降低可能参与了 2 - DM患者合并 EH的发病。     

The role of asymmetric dimethylarginine and arginine in the failing heart and its vasculature

Nitric oxide (NO) is formed from arginine by the enzyme nitric oxide synthase (NOS). Asymmetric dimethylarginine (ADMA) can inhibit NO production by competing with arginine for NOS binding. Therefore, the net amount of NO might be indicated by the arginine/ADMA ratio. In turn, arginine can be metabolized by the enzyme arginase, and ADMA by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). While ADMA has been implicated as a cardiovascular risk factor, arginine supplementation has been indicated as a treatment in cardiac diseases. This review discusses the roles of ADMA and arginine in the failing heart and its vasculature. Furthermore, it proposes nutritional therapies to improve NO availability.