L-arginine reduces heart rate and improves hemodynamics in severe congestive heart failure

Chlorella Supplementation Reduces Blood Lactate Concentration and Increases O2 Pulse during Submaximal and Maximal Cycling in Young Healthy Adults

Chlorella supplementation is reported to improve V˙O2max following extended supplementation periods (~3 weeks). However, there is little research on its impact over submaximal exercise intensities and following shorter supplementation regimens. This study aimed to investigate the efficacy of 6 g/day 2-day chlorella supplementation on exercise performance in healthy young adults. Twenty young healthy adults (Males = 16, Females = 4) (Age 22 ± 6 years, V˙O2max 42.7 ± 9.6 mL/(kg·min)) were recruited for this double-blinded, randomised cross-over study. Participants ingested 6 g/day of chlorella or a placebo for 2 days, with a one-week washout period between trials. Exercise testing consisted of a 20 min submaximal cycle at 40% of their work rate max (WRmax) (watts), followed by an incremental V˙O2max test. Lactate (mmol/L), heart rate (b/min), oxygen consumption (mL/(kg·min)), O2 pulse (mL/beat), respiratory exchange ratio (RER), and WRmax were compared across conditions. Following chlorella supplementation, blood lactate levels were significantly lower (p < 0.05) during submaximal exercise (3.05 ± 0.92 mmol/L vs. 2.67 ± 0.79 mmol/L) and following V˙O2max tests (12.79 ± 2.61 mmol/L vs. 11.56 ± 3.43 mmol/L). The O2 pulse was significantly higher (p < 0.05) following chlorella supplementation during submaximal (12.6 ± 3.5 mL/beat vs. 13.1 ± 3.5 mL/beat) and maximal exercise intensity (16.7 ± 4.6 mL/beat vs. 17.2 ± 4.5 mL/beat). No differences existed between conditions for oxygen consumption, RER, V˙O2max, or WRmax. A total of 2 days of 6 g/day chlorella supplementation appears to lower the blood lactate response and increase O2 pulse during both submaximal and maximal intensity exercise but did not lead to any improvements in V˙O2max.

Impact of oral L-arginine supplementation on blood pressure dynamics in children with severe sickle cell vaso-occlusive crisis

Sickle cell anaemia (SCA) patients generally have lower blood pressures compared to those with the AA haemoglobin genotype. However, during vaso-occlusive crises (SCA-VOC), blood pressures (BP) may elevate transiently to levels beyond the 95^th percentile. The risk of stroke or even death increases with increasing systolic BP in SCA. Therefore, interventions targeted at BP reduction may be essential during severe vaso-occlusive episodes. Reduction in BP was achieved with arginine therapy in a meta-analysis of randomized controlled trials (RCT) in non-sickle cell adults. The impact of oral arginine (given for pain control) on the BP of children with SCA-VOC has not been documented.

METHODS

A double-blind RCT of oral _L-arginine hydrochloride as adjuvant therapy for pain reduction was conducted in children with SCA-VOC, aged 5-17 years, over a 2-year period. The mean change in BP and the time to achieve BP <90^th percentile was added as part of the outcome variables. The anthropometry, pain scores and mercury sphygmomanometry were done following standard procedures. BP percentiles were generated using the Fourth Report guidelines. Differences in the time to normalization of BP in the treatment arms were tested with Kaplan-Meier analysis.

RESULTS

Sixty-six children (57.6% male) were randomized into _L-arginine (35 patients) or placebo (31 patients) arm. The prevalence of hypertension (BP ≥95^th percentile) at presentation tended to increase as the pain scores increased, from a prevalence of 50% in patients with a score of 7 to 65% in those with score of 10 (systolic hypertension) and from 44.4% in patients with pain score of 7 to 50% in patients with pain score of 10 (diastolic hypertension). Patients that received arginine recorded a 12.8±3.2 mmHg decline in mean systolic BP compared to the placebo group, where a mean difference of 7.6±1.5 mmHg was observed, P<0.001. Similarly, the mean diastolic BP reduced by 13% in the arginine group and 7.5% in the placebo group, P<0.001. Children who received arginine tended to achieve BP normalization much faster than the placebo group (P=0.112), and no serious adverse events were documented related to the hypertension or arginine administration.

CONCLUSIONS

High blood pressure (≥95^th percentile) is common amongst children with SCA-VOC and are mostly asymptomatic. Administration of oral arginine given for pain control achieves a reduction of the BP at a faster rate in children compared to placebo and it is safe.

Effect of l-arginine on cardiac reverse remodeling and quality of life in patients with heart failure

BACKGROUND & AIMS

Heart failure (HF), as a major cardiac disease, is associated with considerable mortality, morbidities and poor quality of life. The aim of this study was to investigate the effect of l-arginine supplementation on cardiac outcomes and quality of life in patients with ischemic HF.

METHODS

This double-blind randomized controlled clinical trial was conducted in 50 patients with ischemic HF. Patients were randomly assigned to receive either 3 gr/d l-arginine or placebo, for 10 weeks. Cardiac function (based on echocardiography and six-minute walk test), blood pressure, and quality of life (based on the Minnesota living with heart failure questionnaire) were assessed.

RESULTS

The results showed significant improvements in ejection fraction (-6.5 ± 8.7 vs. -0.7 ± 7.8%, P = 0.037), left ventricular function (P = 0.043), diastolic dysfunction (P = 0.01) and marginally improvement in changes of left ventricular dimension during diastole (LVDd) (4 ± 6 vs. 0.3 ± 6.9 mm, P = 0.065) in the l-arginine compared to the placebo group. At the end of the study, physical aspect (5.7 ± 3.3 vs. 1.2 ± 6.1, P = 0.002) and total score (10 ± 6.7 vs. 4.1 ± 9.4, P = 0.011) of quality of life improved significantly in the l-arginine compared with the placebo group. Additionally, pre-to post-values of diastolic blood pressure, mean arterial pressure, LVDd, LV ejection fraction, left ventricular function, diastolic dysfunction as well as physical and total scores of quality of life improved significantly within the intervention, but not the placebo, group (all P < 0.05).

CONCLUSION

This study showed that 3 gr/d l-arginine supplementation for 10 weeks could improve cardiac recovery and function, and quality of life in patients with HF. This study was registered at the Iranian Clinical Trial Registration Center (www.irct.ir) with IRCT20170202032367N4 code.

Plasma proteomic approach in patients with heart failure: insights into pathogenesis of disease progression and potential novel treatment targets

AIMS

To provide insights into pathogenesis of disease progression and potential novel treatment targets for patients with heart failure by investigation of the plasma proteome using network analysis.

METHODS AND RESULTS

The plasma proteome of 50 patients with heart failure who died or were rehospitalised were compared with 50 patients with heart failure, matched for age and sex, who did not have an event. Peptides were analysed on two-dimensional liquid chromatography coupled to tandem mass spectrometry (2D LC ESI-MS/MS) in high definition mode (HDMSE). We identified and quantified 3001 proteins, of which 51 were significantly up-regulated and 46 down-regulated with more than two-fold expression changes in those who experienced death or rehospitalisation. Gene ontology enrichment analysis and protein-protein interaction networks of significant differentially expressed proteins discovered the central role of metabolic processes in clinical outcomes of patients with heart failure. The findings revealed that a cluster of proteins related to glutathione metabolism, arginine and proline metabolism, and pyruvate metabolism in the pathogenesis of poor outcome in patients with heart failure who died or were rehospitalised.

CONCLUSIONS

Our findings show that in patients with heart failure who died or were rehospitalised, the glutathione, arginine and proline, and pyruvate pathways were activated. These pathways might be potential targets for therapies to improve poor outcomes in patients with heart failure.

Efficacy of preoperative amino acid supplements on postoperative physical function and complications in open heart surgery patients: A study protocol for a randomized controlled trial

BACKGROUND

Elderly patients undergoing cardiac surgery often show poor nutritional status, muscle wasting, and sarcopenia, which are reported to affect postoperative functional recovery and incidence of complications. Amino acids are essential in maintaining nutritional status, synthesizing muscle protein, and promoting beneficial energy balance of the heart muscle. β-Hydroxy β-methylbutyric acid (HMB) is a leucine metabolite known to increase muscle protein synthesis and inhibit protein catabolism; it has been used to more effectively support patients with muscle wasting due to wearing diseases. However, the efficacy of amino acid administration comprising HMB in patients undergoing open heart surgery remains unclear. This study aims to examine whether preoperative short-term aggressive amino acid administration helps support postoperative recovery of physical function and prevent complications.

METHODS

This is a single-center prospective randomized controlled trial (UMIN000030490). Patients aged ≥65 years who will be hospitalized for medical examination before cardiac surgery will be recruited. The participants will be randomly assigned to the experimental or control group. The experimental group will be administered with an amino acid supplement with HMB 1200mg, l-glutamine 7000mg, and l-arginine 7000mg once or twice per day depending on the degree of renal dysfunction, for 14-28 days preoperatively. The control group will not receive any nutritional intervention. The main outcome will be a change in the 6-min walking test distance pre- and postoperatively as a sign of functional recovery. Secondary outcomes such as the incidence of complications; physical, nutritional, and psychological states; mortality; and length of hospital stay will also be evaluated.

CONCLUSION

This clinical study will determine the effects of preoperative short-term oral amino acid supplementation with HMB, l-glutamine, and l-arginine on postoperative physical function in elderly patients undergoing cardiac surgery.

Oral nitrate and citrulline decrease blood pressure and increase vascular conductance in young adults: a potential therapy for heart failure

Purpose

Both inorganic nitrate and citrulline are known to alter the arginine–nitric oxide–nitrate system to increase the bioavailability of nitric oxide with potential benefits in the treatment of heart failure. However, their effects on cardiac electrical activity, vascular compliance and peripheral conductance are less well understood. This study examined the effect of nitrate and citrulline on cardiac electrical activity and blood flow.

Methods

Young adult subjects (n = 12) were recruited to investigate the effects of acute oral nitrate consumption (8 mg/kg) and chronic citrulline consumption (3 g/day) on cardiac electrical activity measured by ECG recording and blood pressure. Blood flow and vascular compliance were measured by IR-plethysmography at the thumb and the hallux.

Results

Nitrate (p < 0.05) and citrulline (p < 0.01) consumption both decreased diastolic blood pressure but had no effect on either pulse pressure or rate-pressure product (NS for both). Citrulline also decreased systolic pressure (p < 0.01). Nitrate and citrulline both decreased vascular compliance (p < 0.05 for both) prior to isometric grip exercise, but this was increased for nitrate following exercise (NS). Citrulline decreased R–R interval 9 % (p < 0.05) at rest and increased heart rate (p < 0.05) in addition to significantly decreasing pulse transit duration (6 %; p < 0.05). QRS duration was also decreased by 5 % for citrulline (p < 0.05) with the reduction in R–R interval.

Conclusion

Both nitrate and citrulline supplementation decreased vascular tone at rest but citrulline also altered sympathovagal balance to increase sympathetic tone. We suggest that both oral nitrate and citrulline may be suitable adjuvants for patients with heart failure to improve peripheral tissue oxygenation.

[Pharmaconutrition: pharmacological approach to nutrition therapy]

Reviewing the literature of nutrition therapy one can conclude that during the last decade the pharmacological action of several nutrients has been demonstrated. However, research activity is still at the beginning and it could be verified in a restricted number of nutrients only that in which conditions (illnesses), dose and duration we can expect therapeutic effect in addition to nutrition. The examples of glutamine, arginine, taurine, leucine, ω-3 fatty acids, however, support the possibility that complex reactions and treatment results observed in certain patients are not purely due to nutritional support but the consequence of additional pharmacological action as well. Evaluation of results of therapeutic intervention is especially difficult because in the everyday practice physicians try to use several therapeutic modalities that can be beneficial for the patient. Therefore, retrospective separation of beneficial components of the therapeutic agents is almost impossible. Only well designed, randomized and multicentric studies can verify specific therapeutic action of certain ingredients ie. nutrients.

Reassessment of a suggested pharmacological approach to heart failure: L-arginine is only a marginal NO donor in pigs

OBJECTIVES

L-Arginine has been tested in various cardiovascular diseases, mainly to improve endothelial function through NO production. However, as the results have been partly unpredictable, we assessed the hemodynamic, energetic and metabolic effects of L-arginine to clarify any potential benefits in postischemic left ventricular (LV) dysfunction.

METHODS

LV dysfunction was induced by repetitive brief coronary occlusions in 12 anesthetized, open chest pigs. L-Arginine was subsequently infused (bolus 400 mg·kg and continuously for 1 hour, 250 mg·kg·h). Hemodynamic parameters, metabolites of L-arginine and myocardial energetics were assessed sequentially.

RESULTS

L-Arginine infusions caused a substantial rise in plasma L-arginine (3474 ± 358 μmole·L) accompanied by a 2-fold increase in plasma L-citrulline. No significant alterations in vascular resistance or LV contractility were observed from L-arginine. Mean arterial pressure dropped from 78 ± 11 to 72 ± 10 mm Hg (P = 0.019) and 70 ± 8 mm Hg (P = 0.003) after bolus and infusions, respectively. Myocardial oxygen consumption was unaltered, and myocardial creatine content was not increased after 90 minutes of L-arginine infusion.

CONCLUSION

L-Arginine infusion did not influence the energetic cost of myocardial contractility, and only minor hemodynamic changes were observed despite a demonstrable turnover of L-arginine. These findings question the use of L-arginine to promote therapeutic NO formation in the acute setting.

Pathogenetic role of eNOS uncoupling in cardiopulmonary disorders

The homodimeric flavohemeprotein endothelial nitric oxide synthase (eNOS) oxidizes l-arginine to l-citrulline and nitric oxide (NO), which acutely vasodilates blood vessels and inhibits platelet aggregation. Chronically, eNOS has a major role in the regulation of blood pressure and prevention of atherosclerosis by decreasing leukocyte adhesion and smooth muscle proliferation. However, a disturbed vascular redox balance results in eNOS damage and uncoupling of oxygen activation from l-arginine conversion. Uncoupled eNOS monomerizes and generates reactive oxygen species (ROS) rather than NO. Indeed, eNOS uncoupling has been suggested as one of the main pathomechanisms in a broad range of cardiovascular and pulmonary disorders such as atherosclerosis, ventricular remodeling, and pulmonary hypertension. Therefore, modulating uncoupled eNOS, in particular eNOS-dependent ROS generation, is an attractive therapeutic approach to preventing and/or treating cardiopulmonary disorders, including protective effects during cardiothoracic surgery. This review provides a comprehensive overview of the pathogenetic role of uncoupled eNOS in both cardiovascular and pulmonary disorders. In addition, the related therapeutic possibilities such as supplementation with the eNOS substrate l-arginine, volatile NO, and direct NO donors as well as eNOS modulators such as the eNOS cofactor tetrahydrobiopterin and folic acid are discussed in detail.

Acute effects of a single dose of phosphodiesterase type 5 inhibitor (sildenafil) on systemic arterial blood pressure during exercise and 24-hour ambulatory blood pressure monitoring in heart transplant recipients

BACKGROUND

Arterial systemic hypertension (SH) can be associated with a decrease in endothelium-dependent nitric oxide (NO). Sildenafil increases cyclic guanosine monophosphate (cGMP), a mediator of NO. However, little is known about the effects of PDE5 inhibition on 24-hour ambulatory pressure (ABP) and exercise blood pressure, noreprinephrine (Nor), and exercise capacity, especially after orthotopic heart transplantation (OHT).

METHODS

We studied 22 OHT patients who on the 1st day underwent a cardiopulmonary (CP) self-controlled treadmill 6' walk test (6') and, then, an ECG monitored CP treadmill maximal exercise test (Ex) within 60 and 90 minutes after oral Sildenafil (Sil; 50 mg) or placebo (Pl) given at random, and ABP. We determined at basal position (b), in the last minute of the 6' and at the peak Ex, the HR (bpm), Systolic blood pressure (SBP), and diastolic blood pressure (DBP), (mm Hg), VO2 (mL/kg/min), Slope VE/VCO2, exercise time (ET, min), distance (D; miles), and Nor (pg/mL). Also, after CP tests, 24-h SBP and DBP, the measurements were repeated on the 2nd day when the cross-over was done.

RESULTS

Sil significantly reduced blood pressure in the basal position and during exercise. It also promoted a significant reduction in SBP and DBP during 24 hours, daytime and nighttime. Sil did not change exercise capacity.

CONCLUSION

The NO-cGMP pathway seems to play a role in blood pressure control in OHT. In addition to antihypertensive therapy, PDE5 inhibition may have potential beneficial effects on hypertensive OHT.

Chronic But Not Acute Oral L-Arginine Supplementation Delays the Ventilatory Threshold During Exercise in Heart Failure Patients

The purpose of this study was to determine, in heart failure patients (HF), whether acute or chronic L-arginine supplementation (LAS) might delay the ventilatory threshold (VT) and whether chronic LAS might reduce exercise-induced plasma lactate increase. HF patients undertook 4 cardiopulmonary bicycle exercises tests. The first 3 were maximal without (EX1), after acute (EX2), or chronic (EX3) oral LAS (6 gm twice a day for 6 weeks). The 4th test (EX4), performed after chronic LAS, was similar to the first in order to investigate the effect of chronic LAS on circulating lactate levels. Results showed that acute LAS failed to improve both submaximal and maximal exercise capacities. Similarly, maximal exercise capacity remained unmodified after chronic LAS. Nevertheless, chronic LAS delayed significantly the patients' ventilatory threshold. Thus exercise duration prior to VT increased (mean ± SEM) from 6.04 ± 0.9 to 7.7 ± 1.03 min (p = 0.04), resulting in a significant increase in oxygen uptake (1.05 ± 0.08 to 1.24 ± 0.12 L•min−1; p = 0.03), CO2 release (0.94 ± 0.10 to 1.2 ± 0.12 L•min−1; p = 0.018), minute ventilation (29.31 ± 2.8 to 34.5 ± 2.7 L; p = 0.009), and workload (60.7 ± 9.8 to 78.5 ± 10.2 watts; p = 0.034). Furthermore, chronic LAS significantly reduced the exercise-induced increase in postexercise plasma lactate concentration (−21 ± 7%). In conclusion, unlike acute supplementation, chronic LAS significantly delays the ventilatory threshold, and chronic LAS reduces circulating plasma lactate in HF patients. These data suggest that chronic LAS might improve the ability of HF patients to perform their daily-life activities. Key words: maximal exercise, heart device, vasodilator

A cardiovascular-respiratory control system model including state delay with application to congestive heart failure in humans

This paper considers a model of the human cardiovascular-respiratory control system with one and two transport delays in the state equations describing the respiratory system. The effectiveness of the control of the ventilation rate is influenced by such transport delays because blood gases must be transported a physical distance from the lungs to the sensory sites where these gases are measured. The short term cardiovascular control system does not involve such transport delays although delays do arise in other contexts such as the baroreflex loop (see [46]) for example. This baroreflex delay is not considered here. The interaction between heart rate, blood pressure, cardiac output, and blood vessel resistance is quite complex and given the limited knowledge available of this interaction, we will model the cardiovascular control mechanism via an optimal control derived from control theory. This control will be stabilizing and is a reasonable approach based on mathematical considerations as well as being further motivated by the observation that many physiologists cite optimization as a potential influence in the evolution of biological systems (see, e.g., Kenner [29] or Swan [62]). In this paper we adapt a model, previously considered (Timischl [63] and Timischl et al. [64]), to include the effects of one and two transport delays. We will first implement an optimal control for the combined cardiovascular-respiratory model with one state space delay. We will then consider the effects of a second delay in the state space by modeling the respiratory control via an empirical formula with delay while the the complex relationships in the cardiovascular control will still be modeled by optimal control. This second transport delay associated with the sensory system of the respiratory control plays an important role in respiratory stability. As an application of this model we will consider congestive heart failure where this transport delay is larger than normal and the transition from the quiet awake state to stage 4 (NREM) sleep. The model can be used to study the interaction between cardiovascular and respiratory function in various situations as well as to consider the influence of optimal function in physiological control system performance.

Influence of L-arginine and vitamin C on the autonomic nervous system in chronic heart failure secondary to ischemic cardiomyopathy

In this study, we used spectral analysis to assess changes in respiratory recording variability during infusion of L-arginine and vitamin C, individually or together, in patients with chronic heart failure. We found that healthy subjects have a substantial ability to modulate sympathetic-mediated peripheral vascular resistance through endothelial synthesis of nitric oxide. Patients with chronic heart failure lose this ability.

Protective role of endothelial nitric oxide synthase

Nitric oxide is a versatile molecule, with its actions ranging from haemodynamic regulation to anti-proliferative effects on vascular smooth muscle cells. Nitric oxide is produced by the nitric oxide synthases, endothelial NOS (eNOS), neural NOS (nNOS), and inducible NOS (iNOS). Constitutively expressed eNOS produces low concentrations of NO, which is necessary for a good endothelial function and integrity. Endothelial derived NO is often seen as a protective agent in a variety of diseases. This review will focus on the potential protective role of eNOS. We will discuss recent data derived from studies in eNOS knockout mice and other experimental models. Furthermore, the role of eNOS in human diseases is described and possible therapeutic intervention strategies will be discussed.

Sildenafil in erectile dysfunction: a critical review

Sildenafil citrate (Viagra) is a potent orally active cGMP-specific phosphodiesterase type 5 (PDE5) inhibitor that is effective as a peripheral conditioner in the treatment of male erectile dysfunction (ED) of organic, psychogenic or mixed aetiology. Sildenafil is the first effective oral agent in the management of ED that has had a revolutionary impact on management of ED. The present review has been subdivided into five major sections. Based on the most recent peer-reviewed publications, the first section is aimed at critically evaluating PDE5 selectivity as well as the pharmacokinetics and pharmacodynamics of the drug, mainly to assess the best doses for each group of patients (i.e. adult and elderly men). Effectiveness in a broad spectrum ED population is the subject of the second section of the review, principally reporting post-marketing company-independent results. Safety and tolerability are the key concerns of the third section, with a broad consideration of the most commonly reported adverse events. Special attention has been paid to the cardiovascular safety of the drug, chiefly outlining the positive and potentially protective cardiac effects of sildenafil. Moreover, the impact of sildenafil in special patient populations is considered, namely in men complaining of diabetes mellitus, depression, neurological disorders, renal failure and those who have undergone a radical prostatectomy. Sildenafil and the ageing male has been especially underlined. Finally, the review covers a few new potential applications of sildenafil in ED patients with regard to high-dose treatment and combination therapy. The review ends with several considerations regarding the direct and/or indirect impact of sildenafil over quality of life and quality of partnership.

Sildenafil effects on exercise, neurohormonal activation, and erectile dysfunction in congestive heart failure: a double-blind, placebo-controlled, randomized study followed by a prospective treatment for erectile dysfunction

BACKGROUND

Erectile dysfunction (ED) is common in patients with congestive heart failure (CHF). ED reduces quality of life, and it may affect compliance, thereby impairing the success of CHF treatment.

METHODS AND RESULTS

In the first phase (fixed-dose double-blind, randomized, placebo-controlled, two-way crossover study), we studied in 23 men with CHF the effects of 50 mg sildenafil on exercise and neurohormonal activation. Patients underwent a treadmill 6-minute cardiopulmonary walking (6'WT) test followed by a maximal cardiopulmonary exercise test (ET). In the second phase, patients received sildenafil, taken as required for ED. Sildenafil reduced the heart rate (HR) (bpm) before the 6'WT (from 75+/-15 to 71+/-14, P=0.02) and ET (from 75+/-15 to 71+/-15, P=0.02); the systolic blood pressure (mm Hg) before the 6'WT (from 116+/-18 to 108+/-18, P=0.004) and ET (from 116+/-15 to 108+/-17, P=0.001); the diastolic blood pressure before the 6'WT (from 69+/-9 to 63+/-11, P=0.01) and ET (from 70+/-8 to 65+/-10, P=0.004); and the Ve/VCO2 slope during the 6'WT (from 32+/-7 to 31+/-6, P=0.04) and ET (from 33+/-8 to 31+/-5, P=0.03). Sildenafil attenuated the HR increment during the 6'WT (P=0.003) and ET (P=0.000). Sildenafil increased the peak *O2 from 16.6+/-3.4 to 17.7+/-3.4 mL/kg per min (P=0.025) and the exercise time from 12.3+/-3.4 to 13.7+/-3.2 minutes (P=0.003). Sildenafil improved most scores of International Index of Erectile Function.

CONCLUSIONS

Sildenafil was tolerated and effective for ED treatment in CHF, and improved the exercise capacity. The reduction of HR during exercise with sildenafil could theoretically decrease the myocardial oxygen consumption during sexual activity.

L-arginine in cardiovascular disease: dream or reality?

L-arginine is the substrate for endothelial nitric oxide synthase (eNOS), and the precursor for the synthesis of nitric oxide (NO). This amino acid exerts a number of actions in the cardiovascular system, mainly through the production of NO. However, it also has a number of NO-independent properties, such as the ability to regulate blood and intracellular pH and the effect on the depolarization of endothelial cell membranes. It also has antihypertensive and antioxidant properties, it influences blood viscosity and the coagulation/fibrinolysis system, and it affects the metabolism of glucose, lipids and proteins. L-arginine influences a number of atherosclerosis risk factors such as hypercholesterolemia, hypertension and smoking, improving endothelial function in these patients. However, it does not affect endothelial function in patients with diabetes mellitus. The role of L-arginine in coronary artery disease is still controversial, but it seems that oral or parenteral administration of this amino acid restores endothelial function in the brachial artery and improves coronary microcirculation. The role of L-arginine in heart failure is currently under investigation, and the first results are rather hopeful. In conclusion, L-arginine seems to provide a hopeful prospect for the treatment of cardiovascular diseases. However, more data derived from large-scale prospective studies evaluating the effects of long-term treatment with L-arginine are needed.

L-arginine in the management of cardiovascular diseases

OBJECTIVE

To examine the role of L-arginine in the management of cardiovascular diseases.

DATA SOURCES

A MEDLINE search (1966-April 2000) of review articles, using the search terms arginine, nitric oxide, and cardiovascular diseases, was conducted. After reviewing these articles, primary studies using the search terms arginine, hypercholesterolemia, hypertension, diabetes, smoking, ischemic heart disease, and heart failure were reviewed.

STUDY SELECTION

English-language human studies were selected and evaluated based on quality of review.

DATA SYNTHESIS

Small-scale studies have demonstrated that intravenous L-arginine augments endothelial function by enhancing vasodilation and reducing monocyte adhesion. Oral supplementation demonstrated similar effects as well as improvement of exercise ability in patients with cardiovascular diseases.

CONCLUSIONS

L-arginine improves the management of multiple cardiovascular diseases. However, most published human studies are small. Before therapy can be routinely recommended, larger, well-designed studies are required to confirm its effect.

Arginine nutrition and cardiovascular function

L-Arginine (Arg) is the substrate for the synthesis of nitric oxide (NO), the endothelium-derived relaxing factor essential for regulating vascular tone and hemodynamics. NO stimulates angiogenesis, but inhibits endothelin-1 release, leukocyte adhesion, platelet aggregation, superoxide generation, the expression of vascular cell adhesion molecules and monocyte chemotactic peptides, and smooth muscle cell proliferation. Arg exerts its vascular actions also through NO-independent effects, including membrane depolarization, syntheses of creatine, proline and polyamines, secretion of insulin, growth hormone, glucagon and prolactin, plasmin generation and fibrinogenolysis, superoxide scavenging and inhibition of leukocyte adhesion to nonendothelial matrix. Compelling evidence shows that enteral or parenteral administration of Arg reverses endothelial dysfunction associated with major cardiovascular risk factors (hypercholesterolemia, smoking, hypertension, diabetes, obesity/insulin resistance and aging) and ameliorates many common cardiovascular disorders (coronary and peripheral arterial disease, ischemia/reperfusion injury, and heart failure). Dietary Arg supplementation may represent a potentially novel nutritional strategy for preventing and treating cardiovascular disease.