Biological action of nitric oxide donor compounds on platelets from patients with sickle cell disease

Several lines of evidence point to the potential role of nitric oxide (NO) in the pathophysiology, as well as in the therapy, of sickle cell disease (SCD). In this study, we compared the effects of NO on platelets from normal individuals and from patients with SCD. Three NO donors were used to deliver NO to platelets: sodium 2-(N, N-diethylamino)-diazenolate-2-oxide (DEANO), S-nitrosocysteine (CysNO) and sodium trioxdintrate (OXINO or Angeli's salt). ADP-induced platelet aggregation, CD62P expression, PAC-1 binding and calcium elevation were evaluated in paired studies of normal and SCD subjects. DEANO significantly reduced aggregation in SCD platelets compared with normal platelets. DEANO similarly reduced the extent of CD62P expression in SCD platelets. All NO donors reduced PAC-1 binding, but there were no significant differences between platelets from normal or SCD subjects. Calcium elevation, as induced by ADP, was not altered by the presence of NO donors. However, when platelets were stimulated with thrombin, there was an increased initial response of SCD platelets compared with normal platelets. Taken together, these data suggest that the mode of NO delivery to platelets may produce various physiological responses and the optimization of NO delivery may contribute to reducing platelet aggregation in sickle cell disease.     

早期糖尿病大鼠肾脏诱生型一氧化氮合酶基因表达

目的观察４周糖尿病大鼠肾脏血流动力学变化和肾脏皮、髓质诱生型一氧化氮合酶（ｉＮＯＳ）基因表达情况。方法应用整体廓清试验和半定量逆转录聚合酶链反应（ＲＴＰＣＲ）。结果糖尿病大鼠肾血浆流量（ＲＰＦ４．５４±０．２４ｍｌ／ｍｉｎ／１００ｇｗｔ）、肾小球滤过率（ＧＦＲ１．１５±０．０４ｍｌ／ｍｉｎ／１００ｇｗｔ）显著高于正常（ＲＰＦ３．４４±０．５０，ＧＦＲ０．９４±０．０３）；肾脏皮、髓质ｉＮＯＳｍＲＮＡ水平（经ＧＡＰＤＨ校正）亦明显升高（皮质１．４９±０．０１比正常１．００±０．００８；髓质３．９０±０．０８比正常１．００±０．０９）。结论一氧化氮（ＮＯ）增加可能是糖尿病早期肾脏高灌注、高滤过的重要原因。高水平ＮＯ即可直接扩张肾血管，导致ＲＰＦ、ＧＦＲ升高；又可能通过升高肾间质压，抑制管球反馈参与肾小球高灌注、高滤过的形成     

Gene transfer of endothelial nitric oxide synthase alters endothelium-dependent relaxations in aortas from diabetic rabbits

Aims/hypothesis. Cardiovascular disease is the leading cause of death in diabetes mellitus. Abnormal endothelium-dependent relaxation is observed both in humans and in animal models of diabetes mellitus and decreased bioavailability of nitric oxide (NO) is thought to be involved in this defect. Therefore, the aim of this study was to test whether adenovirus-mediated gene transfer of endothelial nitric oxide synthase (eNOS) alters vascular reactivity of diabetic vessels.¶Methods. Vascular reactivity was first assessed in thoracic aortas and carotid arteries from nine alloxan-induced diabetic (plasma glucose, 26.5 ± 1.2 mmol/l; HbA_{1 c}, 6.4 ± 0.3 %) and nine control rabbits (plasma glucose, 11.1 ± 1.3 mmol/l; HbA_{1 c}, 2.1 ± 0.1 %). Vascular reactivity was next examined in thoracic aortas of diabetic animals after ex vivo transduction with replication-deficient adenovirus encoding gene for eNOS (AdeNOS) or β-galactosidase (Adβ gal).¶Results. After 10 weeks of hyperglycaemia, endothelium-dependent relaxation to acetylcholine was impaired in diabetic aorta, but was normal in carotid arteries from diabetic rabbits. In contrast, responses of both vessels to calcium ionophore and nitric oxide donor were normal. Histochemical staining for β-galactosidase and immunohistochemistry for eNOS showed transgene expression in the endothelium and adventitia in Adβ gal and AdeNOS transduced vessels, respectively. During submaximum contractions with phenylephrine, relaxations to low concentrations of acetylcholine (3 × 10^–8 to 10^–7 mol/l) were augmented in AdeNOS transduced diabetic vessels.¶Conclusion/interpretation. These findings suggest that adenovirus-mediated gene transfer of eNOS to diabetic aorta alters vascular reactivity. [Diabetologia (2000) 43: 340–347]     

Reduced nerve blood flow in diabetic rats: relationship to nitric oxide production and inhibition of aldose reductase

This study examined links between impaired nitric oxide production in the sciatic endoneurium, nerve blood flow, and polyol pathway flux, to test the hypothesis that reduced nerve blood flow might be compromised by competition for NADPH between aldose reductase and nitric oxide synthase. Sciatic nerves of streptozotocin-diabetic rats showed reduced laser Doppler flux (by 51 % or 63 %; both p<0.05)—indicative of reduced nerve blood flow—and reduced motor nerve conduction velocity (17 % in two experiments; p<0.05). Acute interruption of nitric oxide production in the sciatic nerves of control rats, via endoneurial injection of Nω-nitro-D -arginine methyl ester ( L -NAME), caused a local reduction (of 64 %; p<0.001) in nerve Doppler flux. This was reversed by either L -arginine or sodium nitroprusside. The response to L -NAME was greatly reduced in diabetic rats (only 22 % reduction; p<0.01), though both L -arginine and SNP caused marked increases in flux. Chronic inhibition of aldose reductase in diabetic rats (with either sorbinil or imirestat at a range of doses) had little effect on resting sciatic nerve Doppler flux, though both inhibitors normalized conduction velocity. Both aldose reductase inhibitors reduced sorbitol pathway intermediates in a dose-related manner. These findings do not support the proposition that aldose reductase inhibitors normalise conduction velocity by mechanisms dependent upon either normalization of endoneurial nitric oxide or nerve blood flow. Instead, a mechanism based upon more direct effects on axon or Schwann cell function is favoured. © 1998 John Wiley & Sons, Ltd.     

一氧化氮和内皮素与早期糖尿病大鼠肾小球高滤过的关系

目的　探讨一氧化氮（ Ｎ Ｏ） 和内皮素（ Ｅ Ｔ） 在早期糖尿病大鼠肾小球高滤过中的作用。方法采用链脲佐菌素（ Ｓ Ｔ Ｚ） 诱导的大鼠糖尿病模型，将糖尿病形成７ ～１４ 天定为早期，观察早期肾脏病变和血浆、组织匀浆中的硝酸盐（ Ｎ Ｏ３ ） 及内皮素水平变化。结果　糖尿病形成早期，肾重／ 体重增加（ Ｐ＜ ０ ．０５） ；且出现大量蛋白尿（ Ｐ＜ ０ ．００１） ；肌酐清除率（ Ｃ Ｃｒ） 明显增高（ Ｐ＜ ０ ．００１） ；血浆及组织匀浆中 Ｎ Ｏ３ 明显增高（ Ｐ＜ ０ ．００５） ，均与 Ｃ Ｃｒ 呈正相关关系；血浆及组织匀浆中 Ｅ Ｔ 水平明显下降（ Ｐ＜ ０ ．００１） 。结论　提示糖尿病早期已有肾脏病变； Ｃ Ｃｒ 升高间接表明肾小球滤过率（ Ｇ Ｆ Ｒ） 升高，研究结果认为 Ｎ Ｏ 是影响糖尿病早期肾小球高滤过的重要介质，而 Ｎ Ｏ 与 Ｅ Ｔ 又可能构成一对具有拮抗效应的血管活性物质，在早期糖尿病鼠肾小球高滤过中起重要的调控作用。     

Evidence for iNOS-dependent peroxynitrite production in diabetic platelets

Aims/hypothesis. The aim of the present study was twofold. Firstly, to determine whether diabetic platelets produce more peroxynitrite than normal platelets and secondly to correlate the peroxynitrite production with the intraplatelet induction of the inducible isoform of nitric oxide-synthase. Methods. Intraplatelet peroxynitrite production was monitored with dichlorofluorescin acetate with a combination of confocal microscopy and steady-state fluorescence. The platelets were probed for the induction of the inducible-nitric oxide-synthase by western immunoblotting. Results. In the presence of extracellular l-arginine (100 μmol/l), platelets from subjects with Type I (insulin-dependent) diabetes displayed about 5 times higher fluorescence than those from control subjects. To determine whether inducible-nitric oxide-synthase was the source of peroxynitrite, dichlorofluorescein production was quantified as a function of l-arginine as well as nitric oxide-synthase inhibitors, in platelets from control subjects, subjects with Type I diabetes and subjects with Type II (non-insulin-dependent) diabetes mellitus. Platelets from subjects with Type I yielded about sevenfold and those from Type II about threefold larger amounts of l-arginine/nitric oxide-synthase-dependent dichlorofluorescein fluorescence than those from control subjects. The platelets were then immunologically probed for inducible-nitric oxide-synthase, which has previously been implicated in peroxynitrite production and detected in megakaryocytes of subjects with coronary heart disease. Western immunoblots of intraplatelet proteins indicated that the inducible-nitric oxide-synthase was absent in control subjects. Platelets from both Type I and Type II diabetic subjects, however, contained inducible-nitric oxide-synthase. Conclusion/interpretation. Inducible-nitric oxide-synthase-derived peroxynitrite is a source of platelet damage in diabetes. [Diabetologia (1999) 42: 539–544] Received: 15 July 1998 and in revised form: 23 November 1998     

Endothelial nitric oxide synthase dysfunction in diabetic mice: importance of tetrahydrobiopterin in eNOS dimerisation

Aims/hypothesis Impaired nitric oxide (NO) bioactivity and increased superoxide (SO) production are characteristics of vascular endothelial dysfunction in diabetes. The underlying mechanisms remain unknown. In this regard, we investigated the role of tetrahydrobiopterin (BH4) bioavailability in regulating endothelial nitric oxide synthase (eNOS) activity, dimerisation and SO production in streptozotocin-induced diabetic mice.Methods Mouse aortas were used for assays of the following: (1) aortic function by isometric tension; (2) NO by electronic paramagnetic resonance; (3) SO by lucigenin-enhanced chemiluminescence and dihydroethidine fluorescence; (4) total biopterin and BH4 by high-performance liquid chromatography; and (5) eNOS protein expression and dimerisation by immunoblotting.Results In diabetic mouse aortas, relaxations to acetylcholine and NO levels were significantly decreased, but SO production was increased, in association with reductions in total biopterins and BH4. Although total eNOS levels were increased in diabetes, the protein mainly existed in monomeric form. Conversely, specifically augmented BH4 in diabetic endothelium preserved eNOS dimerisation, but the expression remained unchanged.Conclusions/interpretation Our results demonstrate that BH4 plays an important role in regulating eNOS activity and its functional protein structure, suggesting that increasing endothelial BH4 and/or protecting it from oxidation may be a rational therapeutic strategy to restore eNOS function in diabetes.     

糖尿病大鼠一氧化氮与骨代谢变化的研究

目的　研究糖尿病 (DM )大鼠血清一氧化氮 (NO)与早期骨代谢改变的关系。方法2 0只SD大鼠分为 2组 ,一组以链脲佐菌素诱导建立糖尿病 (STZ DM )大鼠模型 ,另一为正常对照组 ,测定 2组大鼠的空腹血糖 (FBG)、HbA1c、血清胰岛素、全身、股骨和腰椎骨密度 (BMD)、骨代谢相关指标〔血清钙、骨钙素、降钙素、甲状旁腺素 (PTH)、维生素D3 及尿吡啶酚 /肌酐比〕和血清NO水平。结果　STZ DM大鼠与正常对照组相比 ,血清NO水平显著升高〔(5 1.3± 11.9vs 38.1± 12 .0 )μmol/L ,P <0 .0 1〕 ;全身、股骨和腰椎的BMD显著降低〔(0 .15± 0 .0 7vs 0 .2 1± 0 .0 2 ) g/cm2 ,P<0 .0 1;(0 .16± 0 .0 2vs 0 .19± 0 .0 3) g/cm2 ,P <0 .0 5 ;(0 .12± 0 .0 4vs 0 .18± 0 .0 6 ) g/cm2 ,P <0 .0 5〕 ;血清钙浓度显著升高〔(135 .9± 11.3vs 117.2± 6 .5 )mg/L ,P <0 .0 0 1〕 ,骨钙素水平显著升高〔(0 .0 7± 0 .0 4vs 0 .0 5± 0 .0 1) μg/L ,P <0 .0 5〕 ,维生素D3 水平显著降低〔(7.6± 1.9vs 11.6± 4 .1)μg/L ,P <0 .0 5〕 ,尿吡啶酚 /肌酐显著降低〔(4.8± 0 .8vs 75 .8± 6 0 .7)nmol/mmolCr,P <0 .0 1〕 ;而降钙素和PTH水平改变无统计学意义。相关性分析显示 ,血清NO与尿吡啶酚排泄呈负相关 (r= - 0 .74 ,     

内皮型一氧化氮合酶在早期糖尿病大鼠肾组织中表达的定量研究

目的探讨早期糖尿病大鼠肾组织内N0含量变化与一氧化氮合酶（eNOS）表达之间的关系。方法健康雄性SD大鼠60只随机分成糖尿病模型（DM）组和正常对照（NC）组,每组30只。检测两组大鼠的生化指标,检测肾皮质内NO的含量用亚硝酸还原酶法,肾皮质eNOS的含量用Western blot法。结果与同期NC组比较,（1）第1、2、4周DM组大鼠血糖显著升高（P〈0．01）;（2）DM组肾组织内NO含量在第1周时下降（3．52±0．45VS4．23±0．38）,P〈0．01;第2、4周时显著升高（P〈0．01）,第4周时升高最为明显（9．82±0．54VS4．02±0．32）,P〈0．01;（3）Western blot分析显示eNOS含量在第1周时下降,第2～4周时逐渐升高。结论早期糖尿病大鼠肾组织内NO含量逐渐升高,eNOS逐渐增多,提示在糖尿病早期肾组织内N0含量升高主要由eNOS增加引起。     

Nitric oxide production in PCD: possible evidence for differential nitric oxide synthase function

Primary cilliary dyskinesia (PCD) is characterized by decreased levels of fractional exhaled nitric oxide (FeNO), thought to reflect low activity of airway inducible nitric oxide synthase (iNOS) levels. Alveolar NO (Calv) concentration and bronchial NO (JNO) flux can be calculated from FeNO measured at multiple exhalation flow rates. We hypothesised that whereas bronchial NO would be reduced in PCD due to reduced iNOS function, alveolar NO would reflect endothelial NOS (eNOS) function and be normal. We recorded the medical history; measured FeNO at multiple flow rates (50, 100, 200, 260 ml/sec); and performed spirometry in 24 children (aged 8-16 years). FeNO50 of the PCD children was significantly lower than normal mean (+/-SD) 8.1 +/- 1.3 ppb versus 12.5 +/- 1.6 ppb, P = 0.033. The mean +/- SD values of PCD (n = 24) and normal (n = 20) subjects were respectively: JNO: 383.5 +/- 307.9 versus 650.1 +/- 489 pl/s, P = 0.033, Calv: 1.60 +/- 0.78 versus 1.60 +/- 0.75 ppb, P = NS. We show that Calv is normal in PCD, demonstrating that there is no generalized disorder of NO handling in this condition. This differs from a previous report. Furthermore, we speculate that these data may provide supportive evidence that variable flow NO measurements can assess the relative activity of iNOS and eNOS.     

Reduction of variability of exhaled nitric oxide in healthy volunteers

Exhaled nitric oxide (eNO) is elevated in patients with asthma in contrast to healthy subjects, although the variability is high. In this study, we tried to reduce the variability of eNO in healthy subjects.We measured eNO using ERS guidelines with a fixed exhalation flow of 250 ml/s in 117 (72 women, 45 men) non-smoking healthy subjects and correlated this to antropometric data and standard lung function measurements. Using a model previously defined by Hyde et al., we selected parameters that were likely to have a high correlation with eNO. ENO was log-normally distributed. The normal values for eNO are significantly (P < 0.001) different for men and women: in women mean ln eNO levels (SD) were 1.49 (0.34), in men 1.74 (0.41) (back-transformed value 4.43 resp. 5.73 ppb). Using multiple regression analysis, only In D(m,CO), InTLC and In sG(aw) showed a significant positive correlation with In eNO in men, although only 20% of the variability of eNO could be explained. In women no correlation was observed and only 5% ofthe variability was explained. The high variability of eNO could only partly be explained in men, which makes the use of reference equations not very helpful.     

同型半胱氨酸对大鼠主动脉内皮细胞分泌一氧化氮、血管紧张素Ⅱ、内皮素的影响

探讨同型半胱氨酸(HCY)对大鼠主动脉内皮细胞(EC)分泌一氧化氮(NO)、血管紧张素Ⅱ(Ang Ⅱ)和内皮素(ET)的影响.取体重150—200g健康雄性Wistar大鼠的胸主动脉,以组织贴块法进行EC培养,传代至第5代用于实验,各实验组及对照组均为6孔细胞,实验组加入不同浓度的HCY,对照组不加HCY,分别在2、4、6、8、12、24h观察细胞形态并取细胞培养液测定NO含量.一氧化氮合成酶(NOS)活性、AngⅡ和ET含量.HCY可引起EC形态发生变化HCY刺激EC分泌NO、Ang Ⅱ和ET呈时间和剂量依赖性.提示:HCY使EC分泌NO、Ang Ⅱ、ET平衡失调可能是导致动脉粥样硬化的重要原因之一.     

Exhaled nitric oxide concentrations: online versus offline values in healthy children

Exhaled nitric oxide (FE(NO)) is a noninvasive and practical method to assess airway inflammation. We conducted this investigation to determine the most appropriate flow rate to measure FE(NO) and to obtain reference values for FE(NO) in children. FE(NO) was measured in 112 healthy 6-18 year olds (60 males) at 4 expiratory flow rates (46, 31, 23, and 15 mL/sec) using a chemiluminescent nitric oxide analyzer. Offline and online analyses were done to determine FE(NO) intraclass correlation coefficients, the relationship between FE(NO) and expiratory flow rates, and the effects of age and gender on these measurements. The major findings were: 1) intraclass correlation coefficients for FE(NO) and flow rates ranged from 0.92-0.99 for offline values, and 0.99 for all online values; 2) variation at an expiratory flow rate of 46 mL/sec (SD, 9.39) was considerably less than at other flows, especially at 15 mL/sec (SD, 26.55); 3) FE(NO) increased as flow rates decreased for both offline and online values; 4) there were no significant differences and good agreement between offline bag and online FE(NO) values at 31 and 46 mL/sec expiratory flows; and 5) using multiple regression, significant predictors of FE(NO) were flow, body surface area, age, and FEF(25-75). We have provided FE(NO) values in healthy children and propose that the ideal expiratory flow rate for FE(NO) measurements in children using the single breath technique is between 30-50 mL/sec.     

Leptin in embryos from control and diabetic rats during organogenesis: a modulator of nitric oxide production and lipid homeostasis

BACKGROUND: Leptin is involved in many metabolic and reproductive events and its levels are altered by the diabetic pathology. In this study, leptin concentrations and leptin effects on both nitric oxide (NO) and lipid concentrations were investigated in embryos from control and diabetic rats. METHODS: Diabetes was induced by neonatal streptozotocin administration (90 mg/kg). Embryos from control and diabetic rats were obtained on days 10.5 and 13.5 of gestation, corresponding to early organogenesis and post-placentation periods respectively. Leptin was analysed by enzyme immunoanalysis and immunohistochemistry. Nitrates and nitrites were assessed as an index of NO production. Lipid concentrations were analysed by thin layer chromatography. RESULTS: Leptin concentrations were decreased in embryos obtained from diabetic rats on days 10.5 and 13.5 of gestation when compared to controls. NO concentrations, elevated in diabetic embryopathy, were diminished in the presence of leptin in the embryos obtained from control and diabetic animals both during early organogenesis and after placentation. Leptin additions reduced phospholipid, cholesterol and cholesteryl ester concentrations in embryos obtained from diabetic rats during early organogenesis, although no leptin effects on lipid concentrations were observed in control embryos at this developmental stage. In embryos obtained on day 13.5 of gestation leptin additions reduced cholesteryl ester concentrations in controls, and diminished cholesteryl ester, triglycerides and phospholipids in embryos from diabetic rats. CONCLUSIONS: We demonstrated that leptin plays a role in the regulation of NO concentrations and lipid homeostasis during embryo organogenesis and that the diabetic environment causes a reduction of leptin concentrations in rat embryos.     

Arginine therapy: a novel strategy to induce nitric oxide production in sickle cell disease

To determine the effects of L-arginine (L-Arg) supplementation on nitric oxide metabolite (NOx) production, oral L-Arg was given to normal controls, sickle cell disease (SCD) patients at steady state and SCD patients hospitalized with a vaso-occlusive crisis (VOC). L-Arg (0.1 g/kg) increased NOx formation by 18.8 +/- 68% in normal controls, whereas steady-state SCD patients demonstrated a paradoxical decrease in NOx of -16.7 +/- 4% (P = 0.004). In contrast, patients with VOC demonstrated a dramatic increase in NOx production by +77.7 +/- 103%, a response that was dose dependent. L-Arg appears to be the rate-limiting step in NOx production during VOC. Oral arginine may therefore benefit SCD patients by inducing an increase in NO production during VOC.     

Expression of nitric oxide synthases and effects of L-arginine and L-NMMA on nitric oxide production and fluid transport in collagenous colitis

BACKGROUND AND AIMS: Luminal nitric oxide (NO) is greatly increased in the colon of patients with collagenous and ulcerative colitis. To define the source and consequence of enhanced NO production we have studied expression of NO synthase (NOS) isoforms and nitrotyrosine in mucosal biopsies from these patients. In addition, effects on colonic fluid transfer caused by manipulating the substrate of NOS were studied in patients with collagenous colitis. PATIENTS: Eight patients with collagenous colitis, nine with active ulcerative colitis, and 10 with uninflamed bowel were included. METHODS: Expression of NOS isoforms was quantified by western blotting. Inducible NOS (iNOS) and nitrotyrosine were localised by immunohistochemistry. Modulation of NOS activity by topical N(G)-monomethyl-L-arginine (L-NMMA) or L-arginine was assessed during perfusion of whole colon. Plasma and perfusate nitrite/nitrate (NOx) was measured by Griess' reaction. RESULTS: Both in collagenous and ulcerative colitis, expression of iNOS was 10(2)-10(3) higher (p<0.001) than in uninflamed bowel and localised primarily to the epithelium. Endothelial NOS was evenly expressed in all groups while neuronal NOS was undetectable. Nitrotyrosine was markedly expressed in active ulcerative colitis but rarely detected in collagenous colitis and never in uninflamed bowel. In collagenous colitis, the output of NOx was markedly increased compared with uninflamed bowel (283 (58) v <37 nmol/min; p<0.01) and fluid was net secreted. L-NMMA reduced the output of NOx by 13-66% (95% confidence intervals) and secretion of fluid by 25-109% whereas L-arginine increased the output of NOx by 3-39% and secretion of fluid by 15-93%. CONCLUSIONS: In collagenous colitis, as opposed to ulcerative colitis, upregulation of iNOS occurs in the absence of nitrotyrosine formation and mucosal damage. Excess generation of NO may be the primary cause of diarrhoea in this condition.     

Effects of nitric oxide donor S-nitrosoglutathione on apoptosis of apheresis platelets

Objectives: The aim of this study is to investigate the effects of a Nitric oxide (NO) donor, S-nitrosoglutathione (GSNO), on apoptosis and the improvement of preservation quality in apheresis platelets.

Methods: A GSNO solution - to make the final GSNO concentration of 100?uM was added into fresh apheresis platelets, and the parameters associated with platelet morphology, metabolism, and apoptosis were dynamically monitored for seven days.

Results: The results showed that the NO level was remarkably higher during the whole storage stageafter GSNO injection. The number of depolarized platelets and platelets with phosphatidylserine valgus were significantly reduced in the GSNO group compared to that of the control group at some time point. The expression of Bcl-xL mRNA on day 5 of storage in the experimental group was significantly higher than that of the control group, but the expression of Bcl-xL protein was not significantly higher than that in the control group. In addition, Bak and Bax mRNA expression levels in the experimental group were significantly lower than those in the control group, but Bak and Bax protein expression levels were not statistically different. Meanwhile, caspase-3 activity was significantly inhibited.

Discussion and conclusion: These data suggest that the addition of a certain dose of GSNO as a NO donor during platelet storage could inhibit platelet apoptosis and reduce platelet storage lesion (PSL) to a certain extent.     

Tetrahydrobiopterin improves endothelium-dependent vasodilation by increasing nitric oxide activity in patients with Type II diabetes mellitus

Aims/hypothesis. Tetrahydrobiopterin is an essential cofactor of nitric oxide synthase, and its deficiency decreases nitric oxide bioactivity. Our aim was to find whether supplementation of tetrahydrobiopterin could improve endothelial dysfunction in diabetic patients.¶Methods. Forearm blood flow responses to the endothelium-dependent vasodilator acetylcholine (0.75– 3.0 μg · 100 ml^–1· min^–1) and to the endothelium-independent vasodilator sodium nitroprusside (0.1–1.0 μg · 100 ml^–1· min^–1) before and during concomitant intra-arterial infusion of tetrahydrobiopterin (500 μg/min) were measured by venous occlusion plethysmography in 12 control subjects and 23 patients with Type II (non-insulin-dependent) diabetes mellitus.¶Results. In control subjects, tetrahydrobiopterin had no effect on the dose-response curves to acetylcholine and sodium nitroprusside. In contrast, in diabetic patients, the attenuated endothelium-dependent vasodilation to acetylcholine was considerably improved by concomitant treatment with tetrahydrobiopterin, whereas the endothelium-independent vasodilation was not affected. This beneficial effect of tetrahydrobiopterin in diabetic patients could be completely blocked by N ^G-monomethyl-l-arginine.¶Conclusion/interpretation. These findings suggest the possibility that endothelial dysfunction in Type II diabetes might be related to decreased availability of tetrahydrobiopterin. [Diabetologia (2000) 43: 1435–1438]