Arginine and nitric oxide synthase: regulatory mechanisms and cardiovascular aspects

Erectile dysfunction and cardiovascular risk factors in a Mediterranean diet cohort

BACKGROUND

Erectile dysfunction affects more than 100 million men worldwide, with a wide variability in prevalence. An overall association of cardiovascular risk factors, lifestyle and diet in the context of ED in a Mediterranean population is lacking.

AIM

To assess ED prevalence and associated factors in a Mediterranean cohort of non-diabetic patients with cardiovascular risk factors.

METHODS

Observational, cross-sectional study of patients aged over 40 treated at cardiovascular risk units in Catalonia. Anthropometric data, risk factors, lifestyle and diet habits were recorded. ED was assessed using the International Index of Erectile Function.

RESULTS

Four hundred and forty patients included, 186 (42.3%) with ED (24.8% mild, 6.8% moderate and 10.7% severe). ED presence and severity were associated with age, obesity, waist circumference, hypertension, antihypertensive treatment and ischaemic disease. Patients with ED were more frequently smokers, sedentary and consumed more alcohol. In multivariate analysis, consumption of nuts (> twice a week) (OR 0.41 (95% CI 0.25 to 0.67) and vegetables (≥ once a day) (OR 0.47 (95% CI 0.28-0,77)), were inversely related to ED. Obesity (as BMI ≥ 30 kg/m(2) ) (OR 2.49 (95% CI 1.48-4.17)), ischaemic disease (OR 2.30 (95% CI 1.22 to 4.33), alcohol consumption (alcohol-units a day) (OR 1.14 (95% CI 1.04 to 1.26), and age (year) (OR = 1.07 (95% CI 1.04-1.10) were directly related to ED.

CONCLUSION

Erectile dysfunction is a common disorder in patients treated in lipid units in Catalonia for cardiovascular risk factors. This condition is associated with age, obesity, ischaemic disease and unhealthy lifestyle habits.

Arginine intake is associated with oxidative stress in a general population

OBJECTIVE

The aim of this study was to assess the association between protein and arginine from meat intake and oxidative stress in a general population.

METHODS

Data came from the Health Survey for Sao Paulo (ISA-Capital), a cross-sectional population-based study in Brazil (N = 549 adults). Food intake was estimated by a 24-h dietary recall. Oxidative stress was estimated by malondialdehyde (MDA) concentration in plasma. Analyses were performed using general linear regression models adjusted for some genetic, lifestyle, and biochemical confounders.

RESULTS

MDA levels were associated with meat intake (P for linear trend = 0.031), protein from meat (P for linear trend = 0.006), and arginine from meat (P for linear trend = 0.044) after adjustments for confounders: age, sex, body mass index, smoking, physical activity, intake of fruit and vegetables, energy and heterocyclic amines, C-reactive protein levels, and polymorphisms in GSTM1 (glutathione S-transferase Mu 1) and GSTT1 (glutathione S-transferase theta 1) genes. Results were not significant for total protein and protein from vegetable intake (P > 0.05).

CONCLUSIONS

High protein and arginine from meat intake were associated with oxidative stress independently of genetic, lifestyle, and biochemical confounders in a population-based study. Our results suggested a novel link between high protein/arginine intake and oxidative stress, which is a major cause of age-related diseases.

Augmented endothelial l-arginine transport ameliorates pressure-overload-induced cardiac hypertrophy

NEW FINDINGS

What is the central question of this study? What is the potential role of endothelial NO production via overexpression of the l-arginine transporter, CAT1, as a mitigator of cardiac hypertrophy? What is the main finding and its importance? Augmentation of endothelium-specific l-arginine transport via CAT1 can attenuate pressure-overload-dependent cardiac hypertrophy and fibrosis. Our findings support the conclusion that interventions that improve endothelial l-arginine transport may provide therapeutic utility in the setting of myocardial hypertrophy. Such modifications may be introduced by exercise training or locally delivered gene therapy, but further experimental and clinical studies are required. Endothelial dysfunction has been postulated to play a central role in the development of cardiac hypertrophy, probably as a result of reduced NO bioavailability. We tested the hypothesis that increased endothelial NO production, mediated by increased l-arginine transport, could attenuate pressure-overload-induced cardiac hypertrophy. Echocardiography and blood pressure measurements were performed 15 weeks after transverse aortic constriction (TAC) in wild-type (WT) mice (n = 12) and in mice with endothelium-specific overexpression of the l-arginine transporter, CAT1 (CAT+; n = 12). Transverse aortic constriction induced greater increases in heart weight to body weight ratio in WT (by 47%) than CAT+ mice (by 25%) compared with the respective controls (P ≤ 0.05). Likewise, the increase in left ventricular wall thickness induced by TAC was significantly attenuated in CAT+ mice (P = 0.05). Cardiac collagen type I mRNA expression was greater in WT mice with TAC (by 22%; P = 0.03), but not in CAT+ mice with TAC, compared with the respective controls. Transverse aortic constriction also induced lesser increases in β-myosin heavy chain mRNA expression in CAT+ mice compared with WT (P ≤ 0.05). Left ventricular systolic pressure after TAC was 36 and 39% greater in WT and CAT+ mice, respectively, compared with the respective controls (P ≤ 0.001). Transverse aortic constriction had little effect on left ventricular end-diastolic pressure in both genotypes. Taken together, these data indicate that augmenting endothelial function by overexpression of l-arginine transport can attenuate pressure-overload-induced cardiac hypertrophy.

NO synthesis from arginine is favored by α-linolenic acid in mice fed a high-fat diet

Alterations in NO availability and signaling play a pivotal role at early stages of the metabolic syndrome (MetSynd). We hypothesized that dietary α-linolenic acid (ALA, 18:3 n-3) favors NO availability by modulating amino acid metabolism, with a specific impact on the arginine-NO pathway. Mice were fed a hyperlipidic diet (285 g lipid/kg, 51.1 % energy), rich in either saturated fatty acids (SFA, provided by palm oil, PALM group) or ALA (provided by linseed oil, LIN group). We measured whole-body NO synthesis and systemic arginine hydrolysis with a tracer-based method, plasma concentration of related metabolites, and hepatic mRNA level of related enzymes, and the study was completed by a transcriptomic analysis in the liver. As expected with this model, hyperlipidic diets resulted in increased adiposity and glycemia after 5 weeks. As compared to PALM mice, LIN mice had a higher plasma nitrite and nitrate concentration, a higher whole-body conversion of arginine into NO vs urea, and a similar plasma concentration of asymmetric dimethylarginine (ADMA), despite a higher expression of the liver dimethylargininase-1. In LIN mice, there was a higher expression of genes involved in PPARα signaling, but a little impact on gene expression related to amino acids and arginine metabolism. This effect cannot be directly ascribed to changes in arginase activity in the liver or ADMA metabolism, nor to direct regulation of the related target genes. In conclusion, dietary ALA favors NO synthesis, which could contribute to rescue NO availability when jeopardized by the nutritional conditions in relation with the initiation of the MetSynd.

N-methylnicotinamide protects against endothelial dysfunction and attenuates atherogenesis in apolipoprotein E-deficient mice

SCOPE

Epidemiological studies have demonstrated that N-methylnicotinamide (MNA) may exert antithrombotic and anti-inflammatory effects on the endothelium. However, the exact role of MNA in endothelial function remains uncertain.

METHODS AND RESULTS

Apolipoprotein E-deficient (apoE(-/-) ) mice fed with a high-fat, high-cholesterol diet (HCD) and human umbilical vein endothelial cells (HUVECs) were used to explore the role of MNA in endothelial function and its underlying mechanism. The endothelium-dependent vasorelaxation to acetylcholine in the aortas of low and high dose MNA-fed apoE(-/-) mice was improved by 24 and 36% (p < 0.05), respectively, compared with high-fat, HCD-fed control. MNA significantly increased nitric oxide/cyclic guanosinemonophosphate levels and decreased asymmetric dimethylarginine (ADMA) concentrations by induction of dimethylarginine dimethylaminohydrolase (DDAH)2 both in aorta and endothelial cells. Neither the activity nor the protein expression of DDAH1 was influenced upon MNA treatment. Then, DDAH2 depletion by RNA interference in HUVECs abolished the protective effect of MNA on endothelial function. Mechanically, this could be attributed to a direct modulation of the methylation level of DDAH2 gene promoter region by MNA.

CONCLUSIONS

The present study reveals a novel mechanism through which MNA improves endothelial dysfunction and attenuates atherogenesis via the modulation of ADMA-DDAH axis.

The first description of complete invertebrate arginine metabolism pathways implies dose-dependent pathogen regulation in Apostichopus japonicus

In this study, three typical members representative of different arginine metabolic pathways were firstly identified from Apostichopus japonicus, including nitric oxide synthase (NOS), arginase, and agmatinase. Spatial expression analysis revealed that the AjNOS transcript presented negative expression patterns relative to those of Ajarginase or Ajagmatinase in most detected tissues. Furthermore, Vibrio splendidus-challenged coelomocytes and intestine, and LPS-exposed primary coelomocytes could significantly induce AjNOS expression, followed by obviously inhibited Arginase and AjAgmatinase transcripts at the most detected time points. Silencing the three members with two specific siRNAs in vivo and in vitro collectively indicated that AjNOS not only compete with Ajarginase but also with Ajagmatinase in arginine metabolism. Interestingly, Ajarginase and Ajagmatinase displayed cooperative expression profiles in arginine utilization. More importantly, live pathogens of V. splendidus and Vibrio parahaemolyticus co-incubated with primary cells also induced NO production and suppressed arginase activity in a time-dependent at an appropriate multiplicity of infection (MOI) of 10, without non-pathogen Escherichia coli. When increasing the pathogen dose (MOI = 100), arginase activity was significantly elevated, and NO production was depressed, with a larger magnitude in V. splendidus co-incubation. The present study expands our understanding of the connection between arginine's metabolic and immune responses in non-model invertebrates.

Novel strategies and underlying protective mechanisms of modulation of vagal activity in cardiovascular diseases

Cardiovascular disease remains a major cause of disability and death worldwide. Autonomic imbalance, characterized by suppressed vagal (parasympathetic) activity and increased sympathetic activity, correlates with various pathological conditions, including heart failure, arrhythmia, ischaemia/reperfusion injury and hypertension. Conventionally, pharmacological interventions, such as β-blocker treatment, have primarily targeted suppressing sympathetic over-activation, while vagal modulation has always been neglected. Emerging evidence has documented the improvement of cardiac and vascular function mediated by the vagal nerve. Many investigators have tried to explore the effective ways to enhance vagal tone and normalize the autonomic nervous system. In this review, we attempt to give an overview of these therapeutic strategies, including direct vagal activation (electrical vagal stimulation, ACh administration and ACh receptor activation), pharmacological modulation (adenosine, cholinesterase inhibitors, statins) and exercise training. This overview provides valuable information for combination therapy, contributing to establishment of a comprehensive system on vagal modulation from the aspects of clinical application and lifestyle improvement. In addition, the mechanisms contributing to the benefits of enhancing vagal tone are diverse and have not yet been fully defined. We endeavour to outline the recent findings that advance our knowledge regarding the many favourable effects exerted by vagal activation: anti-inflammatory pathways, modulation of NOS and NO signalling, regulation of redox state, improvement of mitochondrial biogenesis and function, and potential calcium regulation. This review may help to develop novel therapeutic strategies targeting enhancing vagal activity for the treatment of cardiovascular diseases.

Arginine behaviour after arginine or citrulline administration in older subjects

Arginine (ARG) and its precursor citrulline (CIT) are popular dietary supplements, especially for the elderly. However, age-related reductions in lean body mass and alterations in organ functions could change their bioavailability. Pharmacokinetics and tolerance to amino acid (AA) loads are poorly documented in elderly subjects. The objective here was to characterise the plasma kinetics of CIT and ARG in a single-dosing study design. Eight fasting elderly men underwent two separate isomolar oral loading tests (10 g of CIT or 9·94 g of ARG). Blood was withdrawn over an 8-h period to measure plasma AA concentrations. Only CIT, ornithine and ARG plasma concentrations were changed. Volume of distribution was not dependent on AA administered. Conversely, parameters related to ARG kinetics were strongly dependent on AA administered: after ARG load, elimination was higher (ARG>CIT; P=0·041) and admission period+time at peak concentration was lower (ARG<CIT; P=0·033), and the combination of both phenomena results in a marked increase in ARG availability when CIT was administered (ARG<CIT; P=0·033) compared with ARG administration itself. In conclusion, a single CIT administration in the elderly is safe and well tolerated, and CIT proves to be a better in vivo ARG precursor than ARG itself in healthy elderly subjects.

Pterostilbene, an Active Constituent of Blueberries, Stimulates Nitric Oxide Production via Activation of Endothelial Nitric Oxide Synthase in Human Umbilical Vein Endothelial Cells

Endothelial dysfunction, a key process in development of cardiovascular diseases, is largely due to reduced nitric oxide (NO) derived from endothelial NO synthase (eNOS). Resveratrol has been reported to stimulate NO production via estrogen receptor α (ERα) activation in endothelial cells. Here, we investigated whether two natural methylated analogs of resveratrol, pterostilbene (Pts) and trans-3,5,4'-trimethoxystilbene (TMS), similarly to resveratrol, could influence endothelial NO release in human umbilical vein endothelial cells (HUVECs). In HUVECs exposed to Pts or TMS, NO production and phosphorylation of eNOS, protein kinase B (Akt), and ERα were measured by using a fluorimetric NO assay kit and Western blot analysis, respectively. Dimethylated Pts, but not trimethylated TMS, stimulated dose-dependent NO production via eNOS phosphorylation. Pts also stimulated dose-dependent phosphorylation of Akt, but not of ERα. NO production and eNOS phosphorylation in response to Pts were significantly abolished by the phosphoinositide 3-kinase (PI3K)/Akt inhibitor LY294002, but not by the ERα antagonist ICI182780. Our results suggest that Pts, but not TMS, is capable of inducing eNOS phosphorylation and the subsequent NO release, presumably, by activating PI3K/Akt pathway. The potential efficacy of Pts, an active constituent of blueberries, may aid in the prevention of cardiovascular diseases characterized by endothelial dysfunction.

Is the serum l-arginine level during early pregnancy a predictor of pregnancy-induced hypertension?

The objective of this study was to determine the concentration of serum l-arginine in healthy pregnant women and infant cord blood and to compare them with those in patients with pregnancy-induced hypertension (PIH). The serum concentration of l-arginine in normal pregnant women at early gestation (n = 186) was determined and analyzed based on maternal factors such as the age, pre-pregnancy body mass index (BMI), smoking and alcohol habits before pregnancy. Similarly, the concentration of cord blood of the newborns (n = 142) was also analyzed. These values were compared with those in the PIH group (n = 21). The potential risk factors for PIH were also estimated. The serum concentration of l-arginine at early gestation in normal pregnant women (88.65 ± 19.96 µM) was not affected by the maternal age and BMI before pregnancy. A lower l-arginine concentration at early gestation (<70 µM) significantly elevated PIH risk [adjusted odds ratio (OR) = 4.26, 95% CI 1.29-14.50]. In addition, either women with large body mass before pregnancy (BMI>25 kg/m(2)) or primipara women also showed a significant association with PIH risk [adjusted OR = 10.55 (2.95-40.68); 5.25 (1.72-19.15), respectively]. In conclusion, a lower l-arginine concentration at early gestation, overweight before pregnancy (BMI>25 kg/m(2)) and primipara could predict to the development of PIH.

Anthracyclines/trastuzumab: new aspects of cardiotoxicity and molecular mechanisms

Anticancer drugs continue to cause significant reductions in left ventricular ejection fraction resulting in congestive heart failure. The best-known cardiotoxic agents are anthracyclines (ANTHs) such as doxorubicin (DOX). For several decades cardiotoxicity was almost exclusively associated with ANTHs, for which cumulative dose-related cardiac damage was the use-limiting step. Human epidermal growth factor (EGF) receptor 2 (HER2; ErbB2) has been identified as an important target for breast cancer. Trastuzumab (TRZ), a humanized anti-HER2 monoclonal antibody, is currently recommended as first-line treatment for patients with metastatic HER2(+) tumors. The use of TRZ may be limited by the development of drug intolerance, such as cardiac dysfunction. Cardiotoxicity has been attributed to free-iron-based, radical-induced oxidative stress. Many approaches have been promoted to minimize these serious side effects, but they are still clinically problematic. A new approach to personalized medicine for cancer that involves molecular screening for clinically relevant genomic alterations and genotype-targeted treatments is emerging.

Antioxidative diet supplementation reverses high-fat diet-induced increases of cardiovascular risk factors in mice

Obesity is a worldwide epidemic that is characterized not only by excessive fat deposition but also by systemic microinflammation, high oxidative stress, and increased cardiovascular risk factors. While diets enriched in natural antioxidants showed beneficial effects on oxidative stress, blood pressure, and serum lipid composition, diet supplementation with synthetic antioxidants showed contradictive results. Thus, we tested in C57Bl/6 mice whether a daily dosage of an antioxidative mixture consisting of vitamin C, vitamin E, L-arginine, eicosapentaenoic acid, and docosahexaenoic acid (corabion) would affect cardiovascular risk factors associated with obesity. Obese mice showed increased serum triglyceride and glucose levels and hypertension after eight weeks of being fed a high-fat diet (HFD). Importantly, corabion ameliorated all of these symptoms significantly. Oxidative stress and early signs of systemic microinflammation already developed after two weeks of high-fat diet and were significantly reduced by daily doses of corabion. Of note, the beneficial effects of corabion could not be observed when applying its single antioxidative components suggesting that a combination of various nutrients is required to counteract HFD-induced cardiovascular risk factors. Thus, daily consumption of corabion may be beneficial for the management of obesity-related cardiovascular complications.

Plasma asymmetric and symmetric dimethylarginine in a rat model of endothelial dysfunction induced by acute hyperhomocysteinemia

Hyperhomocysteinemia induces vascular endothelial dysfunction, an early hallmark of atherogenesis. While higher levels of circulating asymmetric dimethylarginine (ADMA) and symmetric dimethyl arginine (SDMA), endogenous inhibitors of nitric oxide synthesis, have been associated with increased cardiovascular risk, the role that ADMA and SDMA play in the initiation of hyperhomocysteinemia-induced endothelial dysfunction remains still controversial. In the present study, we studied the changes of circulating ADMA and SDMA in a rat model of acutely hyperhomocysteinemia-induced endothelial dysfunction. In healthy rats, endothelium-related vascular reactivity (measured as acetylcholine-induced transient decrease in mean arterial blood pressure), plasma ADMA and SDMA, total plasma homocysteine (tHcy), cysteine and glutathione were measured before and 2, 4 and 6 h after methionine loading or vehicle. mRNA expression of hepatic dimethylarginine dimethylaminohydrolase-1 (DDAH1), a key protein responsible for ADMA metabolism, was measured 6 h after the methionine loading or the vehicle. Expectedly, methionine load induced a sustained increase in tHcy (up to 54.9 ± 1.9 µM) and a 30 % decrease in vascular reactivity compared to the baseline values. Plasma ADMA and SDMA decreased transiently after the methionine load. Hepatic mRNA expression of DDAH1, cathepsin D, and ubiquitin were significantly lower 6 h after the methionine load than after the vehicle. The absence of an elevation of circulating ADMA and SDMA in this model suggests that endothelial dysfunction induced by acute hyperhomocysteinemia cannot be explained by an up-regulation of protein arginine methyltransferases or a down-regulation of DDAH1. In experimental endothelial dysfunction induced by acute hyperhomocysteinemia, down-regulation of the proteasome is likely to dampen the release of ADMA and SDMA in the circulation.

Nitric oxide bioavailability affects cardiovascular regulation dependent on cardiac nerve status

The sympathetic nervous system and nitric oxide (NO) contribute to regulation of vascular tone, blood flow regulation and cardiac function. Intrinsic cardiac neurons are tonically influenced by locally released NO and exogenous NO donors; however, the role of intact central neural connections remains controversial. We investigated the effects of S-nitroso-N-acetylpenicillamine (SNAP) administered into an intracoronary artery near the ventral interventricular ganglionated plexus (VIVGP) to evaluate distribution of myocardial blood flow (MBF) and ventricular function in normal and acute cardiac decentralized dogs. MBF was measured with microspheres during infusion of SNAP (100μM, IC) after systemic administration of 7-nitroindazole (nNOS blocker) followed by N(ω)-nitro-L-arginine methyl ester (LN; non-selective NOS blocker). Cardiac dynamics were not significantly affected by cardiac decentralization; several of these parameters (aortic systolic and diastolic pressures) were significantly increased after systemic administration of LN. Overall SNAP administered to the VIVGP increased blood flow in the anterior LV wall (vs. posterior LV wall) without affecting other cardiodynamic factors. In cardiac decentralized dogs subepicardial blood flow to the anterior LV wall during LN+SNAP was diminished resulting in a significantly higher inner:outer blood flow ratio (index of blood flow uniformity across the LV wall). LV function was not affected by acute cardiac decentralization; however, LV ejection fraction decreased markedly after LN (reduced NO bioavailability). These results validate earlier claims that reduced NO bioavailability imposes an upper limit on myocardial blood flow regulation and its transmural distribution. These effects are exacerbated after disconnection of intrinsic cardiac neurons from intact central neuron connections.

L-Arginine Supplementation in Type II Diabetic Rats Preserves Renal Function and Improves Insulin Sensitivity by Altering the Nitric Oxide Pathway

Rat studies demonstrated that type II diabetes mellitus (T2DM) decreases both the production and bioavailability of nitric oxide (NO). L-arginine (LA) provides the precursor for the production of NO. We hypothesized that LA dietary supplementation will preserve NO production via endothelial nitric oxide synthase (eNOS) causing renal microvascular vasodilation and increased glomerular blood flow and thus increasing glomerular filtration rate (GFR). This would impede the formation of reactive oxygen species which contributes to cell damage and death. LA supplementation preserved GFR in the treated diabetic rats compared to untreated diabetic rats. We provide evidence that this effect may be due to increased levels of eNOS and urinary cyclic guanosine monophosphate, which leads to renal microvascular vasodilation. Plasma nitrotyrosine was decreased in the LA treated rats; however, plasma nitrite levels remained unaffected as expected. Marked improvements in glucose tolerance were also observed in the LA treated diabetic rats. These results demonstrate that LA supplementation preserves NO activity and may delay the onset of insulin resistance and renal dysfunction during hyperglycemic stress. These results suggest the importance of the NO pathway in consequent renal dysfunction and in the development of insulin resistance in diabetic rats.

Intestinal microbiome and digoxin inactivation: meal plan for digoxin users?

There is an increasing interest in the role of intestinal microbiome in human diseases and therapeutic agents' bioavailability, activity and toxicity. Epidemiological data show that the bioavailability of digoxin, a widely used agent for heart disease, varies among individuals. The inactivation of digoxin was found when it was incubated with gut bacterium Eggerthella lenta in vitro decades ago. However, the underlying mechanisms of digoxin inactivation are still unclear. A recent study using animal models uncovered this mystery, which suggested that arginine supplements might be a potential intervention in increasing digoxin activity by inhibiting the expression of cardiac glycoside reductase gene operons that inactivated digoxin. This perspective summarizes the connections among the intestinal microbiome, the digoxin inactivation, the metabolism of arginine. We also discuss several issues yet to be addressed in the future, making better strategies in the application of dietary arginine supplements for digoxin users.

Methylglyoxal modulates endothelial nitric oxide synthase-associated functions in EA.hy926 endothelial cells

BACKGROUND

Increased levels of the sugar metabolite methylglyoxal (MG) in vivo were shown to participate in the pathophysiology of vascular complications in diabetes. Alterations of endothelial nitric oxide synthase (eNOS) activity by hypophosphorylation of the enzyme and enhanced monomerization are found in the diabetic milieu, and the regulation of this still remains undefined. Using various pharmacological approaches, we elucidate putative mechanisms by which MG modulates eNOS-associated functions of MG-stimulated superoxide O₂•⁻ production, phosphorylation status and eNOS uncoupling in EA.hy926 human endothelial cells.

METHODS

In cultured EA.hy926 endothelial cells, the effects of MG treatment, tetrahydrobiopterin (BH4; 100 μM) and sepiapterin (20 μM) supplementation, NOS inhibition by N(G)-nitro-L-arginine methyl ester (L-NAME; 50 μM), and inhibition of peroxynitrite (ONOO⁻) formation (300 μM Tempol plus 50 μM L-NAME) on eNOS dimer/monomer ratios, Ser-1177 eNOS phosphorylation and 3-nitrotyrosine (3NT) abundance were quantified using immunoblotting. O₂•⁻-dependent fluorescence was determined using a commercially available kit and tissue biopterin levels were measured by fluorometric HPLC analysis.

RESULTS

In EA.hy926 cells, MG treatment significantly enhanced O₂•⁻ generation and 3NT expression and reduced Ser-1177 eNOS phosphorylation, eNOS dimer/monomer ratio and cellular biopterin levels indicative of eNOS uncoupling. These effects were significantly mitigated by administration of BH4, sepiapterin and suppression of ONOO⁻ formation. L-NAME treatment significantly blunted eNOS-derived O₂•⁻ generation but did not modify eNOS phosphorylation or monomerization.

CONCLUSION

MG triggers eNOS uncoupling and hypophosphorylation in EA.hy926 endothelial cells associated with O₂•⁻ generation and biopterin depletion. The observed effects of the glycolysis metabolite MG presumably account, at least in part, for endothelial dysfunction in diabetes.