Implications of L-Arginine supplementation on cardiovascular system: new prospects of benefits and side effects

Author’s names: José Henrique Silvah^1,4,5, Carolina Ferreira Nicoletti^1,2,3, Cristiane Maria Mártires de Lima^1,5, Bruna Caruso Mazzolani³, Fabiana Infante Smaira³, Gizela Pedroso Junqueira¹, Márcia Varella Morandi Junqueira-Franco^1,5, Julio Sergio Marchini¹

The affiliation(s) of the author(s), i.e. institution, (department), city, (state), country:

¹Division of Medical Nutrition, Department of Internal Medicine, Ribeirão Preto Medical School, University of São Paulo. Ribeirão Preto, SP, Brazil.

²Department of Health Sciences, Ribeirão Preto Medical School, University of São Paulo. Ribeirão Preto, SP, Brazil.

³Applied Physiology and Nutrition Research Group, School of Physical Education and Sport; Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, SP, BR, University of Sao Paulo, SP, Brazil.

⁴IGSSA – Institute for Glutamate Sciences in South America.

⁵ATN – Alimentar Terapia Nutricional – Coordination and Assistance in Nutritional Therapy, Brazil.

Corresponding author: Jose Henrique Silvah. Division of Medical Nutrition, Department of Internal Medicine, Ribeirão Preto Medical School, University of São Paulo. Ribeirão Preto, SP, Brazil. Avenida Bandeirantes, 3900. Zip code: 14048-900. Ribeirão Preto, SP – Brazil. Phone/FAX: +55 16 36022596. email: jhdasilvah@gmail.com

ORCID of the author(s)

José Henrique Silvah:0000-0001-5882-6815; Carolina Ferreira Nicoletti:0000-0002-4610-5786; Cristiane Maria Mártires de Lima:0000-0002-5072-9348;Bruna Caruso Mazzolani:0000-0002-4687-3128, Fabiana Infante Smaira:0000-0003-4218-4779; Gizela Pedroso Junqueira:0000-0003-4894-2550;Márcia Varella Morandi Junqueira-Franco: 0000-0002-7968-5799; Julio Sergio Marchini^: 0000-0001-9999-9149.

Abstract

L-Arginine supplementation can be used as a potential non-pharmacological therapy for cardiovascular system disorders. This review of randomized controlled studies published in the last 10-years was performed to examine the efficacy of L-Arginine’s role as a therapeutic agent, specifically for blood pressure, cardiovascular diseases and athletes’ performance. Clinically significant adverse events were not reported. The stronger evidence about arginine effects was provided by recent systematic reviews and meta-analyses, showing that arginine improves blood pressure and aerobic and anaerobic performance. Few trials were published after those reviews, with contradictory outcomes. There is an urge for future RCTs with isolated arginine supplementation, larger numbers of patients, designed for long-lasting evaluations.

1 – Introduction

L-Arginine is considered a semi-essential or conditionally essential amino acid (Castillo et al. 1993;(Castillo et al. 1994). In some circumstances, such as children growth, pregnancy and lactating, intestinal resection or dysfunction, burns, renal dysfunction and wound healing (Wu et al. 2009), the human body can not synthesize enough arginine to meet physiological demands, and supplementary ingestion of this amino acid must be provided through diet (Visek 1986).

In some metabolic and cardiovascular diseases (CVD), L-Arginine supplementation can be used as a potential non-pharmacological therapy [Rodrigues-Krause, 2019]. This is based on the premise that L-Arginine is the substrate for nitric oxide´s (NO) production through the nitric oxide synthase enzyme (NOS) [Bode-Böger, 2006]. NO is an endogenous messenger molecule involved in many physiological processes. In vascular endothelium, NO is related to muscle cell relaxation and regulation of blood pressure, angiogenesis, and atherosclerosis development [Bode-Böger, 2006; Zuchi, 2010]. NO also is used for cell signaling or oxidative bactericidal actions [Popovic, 2007] and in reduction of infection rates [Kalil, 2006] in the immune system. Previous studies reported that lower NO production may result in decreased blood levels of insulin, increased production of angiotensin II, hyperhomocysteinemia, increased asymmetric dimethylarginine (ADMA) synthesis, and low plasma concentration of L-Arginine [Newsholme, 2009]. Thus, the role of L-Arginine in NO production provides basis for its therapeutic use in cardiovascular disease [Bode-Böger, 2006].

Targeting to normalize NO levels and other metabolites produced from L-Arginine [Rodrigues-Krause, 2019], many animal and clinical studies of L-Arginine supplementation have been developed [Maxwell, 2001; Preli, 2002]. However, the L-Arginine therapeutic paradigm continues to be controversial. Methodological aspects like sample size, type of supplementation and other variations in study populations and interventions could limit the interpretability of L-Arginine supplementation therapeutic efficiency on CVD and related risk factors [Rodrigues-Krause, 2019]. Furthermore, considering the L-Arginine vasodilatory role and that there is some evidence supporting a positive effect of supplements with this function on athletic performance [Pahlavani, 2017; Mor, 2018], studies investigating L-Arginine supplementation in athletes have been conducted. However, there is not clear information regarding it.

Given these considerations, the aim of this review was to summarize evidence from latest randomized controlled trials (RCTs) on the efficacy of L-Arginine’s role as potential supplement for cardiovascular system, specifically blood pressure and CVD, and for athletes’ performance as well as its mechanisms of action with a focus on the role of L-Arginine via NO pathway.

1. Methods

1.1.Search Strategy and Study Selection

A literature search of all RCTs published between January 2010 and August 2020 was performed using the following electronic databases: MEDLINE/PubMed (National Library of Medicine), the Web of Science citation indexing service originally produced by the Institute for Scientific Information and Virtual Health Library (VHL – BVS). The key terms included in the search were: “arginine supplementation” or “L-Arginine supplementation” and “blood pressure”; “hypertension”; “systemic arterial hypertension”; “longevity”; “elderly”; “aging”; “training”; “sport”; “athlete”; “stroke”; “heart attack”; “peripheral vascular disease” or “coronary heart disease”. The literature search was limited to articles published in English language. A literature search was made to find the latest published systematic review on L-Arginine supplementation. A systematic review of L-Arginine supplementation was found by analyzing the change in blood pressure published in 2011. For this reason, it was excluded from studies before 2010 to reduce heterogeneity. All searched articles were downloaded into Rayyan QCRI Plataform (Ouzzani, 2016) to remove duplicated articles and shorten the review process.

Criteria for inclusion of studies in the review were as follows: studies conducted in humans; isolated L-Arginine supplementation, clinical trial, review, or meta-analysis, all with outcomes related to the cardiovascular system. Studies with L-Arginine supplementation combined with other compounds and studies that only the abstract was available were excluded.

1.2.Data Extraction

Four investigators performed independent searches. Any disagreements were resolved by discussion or fourth-party mediation. The following data were extracted and compiled in Excel spreadsheet: first author, year of publication, study design, sample size, sex and mean age of participants, patient´s characteristics (disease features), type (oral or intravenous) and dose of supplementation, time of intervention, clinical outcomes and adverse effects.

1.3.Outcome measures

The literature was examined regarding the effects of L-Arginine supplementation on cardiovascular parameters as outcome variables.

2. Results

Results are described in specific subtopics. Figure 1 shows the PRISMA flowchart of all searched studies and those included in this review. From 1,263 potentially relevant records identified through our structured searches, 926 records were screened (after removing duplicates) and 30 full-text manuscripts were assessed for eligibility. Of them, 13 manuscripts were excluded because they were performed in animal models; with L-Arginine supplementation combined with another compound or, analyzed endogenous arginine. Finally, 4 articles were included in blood pressure topic; 10 articles were included in exercise topic and 4 articles were included in cardiovascular disease topic.

3.1 L-Arginine supplementation and blood pressure

Only four studies met inclusion criteria and were included in this review topic. These studies included one meta-analysis, one randomized controlled trials and two randomized, double-blinded, crossover studies. Details of data extraction from studies are presented in Table 1.

The meta-analysis investigated the effect of oral L-Arginine supplementation on blood pressure, with no participant characteristics restriction (e.g. both normotensive and hypertensive, healthy or with other diseases), and supported this hypothesis. A mild blood pressure (BP)-lowering effect was observed in both systolic (-5.39 mm Hg – 95% CI −8.54 to −2.25) and diastolic (- 2.66 mm Hg – 95% CI −3.77 to −1.54) BP. Also, it appears to be a trend toward greater BP reductions among hypertensive participants than normotensive ones (Dong et al, 2011).

Four studies published after the meta-analysis [Jablecka et al, 2012; Reule et al, 2017; Nascimento et al. 2017; Beckman et al., 2018] filled inclusion criteria to be discussed in this review topic. One of them evaluated thirty-five mild arterial hypertension patients and nineteen healthy adults randomized in groups to receive 2 g or 4 g oral L-Arginine or placebo, thrice a day for 4 weeks. Increased asymmetric dimethylarginine (ADMA), L-citrulline, L-Arginine level and total antioxidant status was observed in all patients supplemented. Those findings lead to two mechanisms by which L-Arginine could be involved in vascular homeostasis and consequently BP reduction: 1) reduction of oxidative stress by stimulating NO biosynthesis and, 2) restoring biodiversity of NO [Jablecka et al, 2012]. However, BP was not monitored or measured after supplementation time, which limits correlations analysis to clearer inferences.

It is known that individuals with chronic diseases are characterized by low grade inflammation and increased pro-inflammatory cytokine levels that can aggravate the disease [Rajend, 2018]. Considering this, another hypothetical L-Arginine mechanism that could be involved in blood pressure regulation in hypertensive individuals is by modulation of pro and anti-inflammatory cytokines [Efron, 1998]. When analyzed in combination with acute resistance exercise, short-term L-Arginine supplementation attenuates elevation of interleukin 6 level and maintains interleukin 10 level, which leads to a potential anti-inflammatory L-Arginine supplementation response not completely understood yet (Nascimento et al. 2017). Local and systemic inflammation has been associated with hypertension [Dartora, 2015] by immune function modulation, therefore its control may prevent and/or relieve disease development and complications [Nascimento et al. 2017]. Besides its interesting and relevant findings, study limitations (e.g. small sample size, no measurements after 4 to 6 hours of exercise session) bring up the need of long-term studies to elucidate L-Arginine mechanisms in anti-inflammatory responses.

Contradicting the hypothesis that L-Arginine supplementation can improve vascular function, Beckman et al. (2018) observed that L-Arginine supplementation can impair endothelial function and executive function in elderly. The 19 individuals assessed had diabetes and/or controlled hypertension and baseline impairment of executive function. They were supplemented for 4 days with doses between 14g and 21g/day, with a 4-week washout period between conditions. L-Arginine supplementation reduced vascular reactivity in digital microarterioles, as well as reduced executive function when compared to placebo. In addition, L-Arginine was associated with increased blood pressure from day 1 to 4 (88 ± 9 mmHg – 92 ± 11 mmHg) (p = 0,01) and there was no difference in placebo administration from day 1 to day 4 (91 ± 9 mmHg – 90 ± 11 mmHg) (p = 0,7). Furthermore, there was a decrease in flow-mediated vasodilation (FMD) (p = 0,02) [Beckman et al., 2018].

3.2 L-Arginine supplementation in physical exercise

Ten papers met inclusion criteria, including one meta-analysis, two crossover studies, one cross-sectional and six randomized trials (see Table 2).

A most recent meta-analysis investigated the effect of acute and chronic supplementation of L-Arginine in athletes’ performance (studies with participants with previous injury or health problems were excluded from this review). It was observed that depending on dosage and time, arginine supplementation can improve athletes’ performance. Acute supplementation of 0.15g/kg ingested sharply between 60 to 90 minutes before exercise would improve aerobic and anaerobic performance, while in chronic supplementation 1.5 to 2g/day of arginine for 4 to 7 weeks or 10 to 12g/day for 8 weeks was needed for better outcomes [Viribayet, 2020].

The chronic or acute arginine supplementation could have different mechanisms and responses on athletes’ performance [Viribayet, 2020]. Acute effects of arginine supplementation supposedly promote vasodilation due to enhanced NO synthesis in active muscle during exercise and may increase delivery and uptake of fuel substrates in skeletal muscle [Zembron-Lacny, 2020]. From that, Sajad et.al. 2018 investigated the effects of L-Arginine supplementation on responses of red blood cell (RBC) properties to high intensity interval exercise (HIIE). Ten overweight healthy men were submitted to two conditions (L-Arginine + HIIE and Placebo + HIIE) in two different sessions with a week between them. L-Arginine group consumed 0.075g/kg of body weight and placebo group consumed Maltodextrin. Blood samples were taken before and 90 minutes after taking L-Arginine/placebo, and immediately after the exercise. The study concluded that HIIE and oral supplementation of L-Arginine did not induce any change in RBC deformability, but due to the differences in HIIE protocols (i.e., intensity, duration and work to rest ratio) as well as differences in methods and dosages of L-Arginine administration (oral vs parenteral and acute vs chronic), further studies are needed.

Moreover, arginine stimulates glucagon secretion, what can change plasma concentrations of some amino acids at rest and during physical exercise [Colombani, 1999] and can improve muscle performance and recovery by increasing nutrient and oxygen delivery to active muscles, improving clearance of waste products, and increasing protein synthesis rate [Colombani, 1999]. Yavuz et al., 2012 conducted a crossover study with 10 elite wrestlers’ male volunteers to investigate plasma amino acid profile during incremental exercise when receiving arginine supplementation (1.5g/10 kg body weight) or placebo. Changes in plasma amino acid profile, except for valine, were observed in the group supplemented. In contrast, another study evaluated the effects of L-Arginine supplementation on muscle recovery after a single session of high-intensity resistance exercise found no difference in lactate and creatine kinase between groups, showing no interference of arginine supplementation in these blood markers [Walkiria, 2018].

In addition, it appears that L-Arginine influences anal and body temperature. This hypothesis is raised since older populations have a decreased vasodilatory response, due to the reduced concentration of endogenous L-Arginine and consequently less bioavailability of NO [Holowatz, 2006]. Still in this reasoning, the L-Arginine NO pathway is dependent on nitric oxide synthesis and therefore, when the individual is subjected to stress (for example, physical exercise) it is likely that L-Arginine may offer a thermoregulatory benefit induced by increased blood flow in healthy individuals. However, this heat effect does not seem to happen with an acute supplementation of 10g of L-Arginine in healthy male participants [Tylor et. al. 2015].

It is known that chronic supplementation can improve maximal oxygen uptake (VO2max) of subjects with impaired endothelial function [Doutreleau, 2005], but the effect on athletes’ performance is very contradictory. Sunderland et. al. (2011) observed the effect of 28-day supplementation of arginine in endurance-trained male cyclists on VO2max and ventilatory thresholds but no difference between groups was found. For the author this was because the analyzed population was healthy and active and the dose of arginine was very small (12 g/day), assuming that in unhealthy and sedentary populations the finding would be different.

Resistance training and supplementation of arginine have been shown to stimulate the release of growth hormone (GH), which helps to promote cellular growth and regulate the mobilization of fuels in the body, contributing to increased muscle mass and hypertrophy [Forbes, 2014]. However, in a study with forty amateur male bodybuilders, increased GH release was found only in the group of resistance training while oral L-Arginine chronic supplementation alone and combined with resistance training demonstrate no effect in GH / IGF-1 axis [Saeed Shirali et. al. 2016].

It is known that older persons have decreased vasodilation and bioavailability of NO due to age [Donato et al., 2018; Bode-Boger, 2003], causing a reduction in blood flow and supplying oxygen to the contracting muscles, and consequently the exercise capacity [Taddei, 2000]. Aguiar et al. (2016) aimed to assess muscle performance and peripheral vasodilation in 20 elderly women with a mean age of 71.6 years. The double-blind controlled study supplemented one dose of arginine (8 g) per week in a single day for three weeks, with an interval of one week between supplemented days. For the assessment of femoral artery vasodilation, doppler ultrasound was performed and for the assessment of muscle performance, isokinetic, isometric, and functional strength tests were performed. Doppler ultrasound was performed three times on a single day (in the first week): 1) before supplementation 2) before the assessment of isokinetic strength (after 80 minutes of supplementation) and 3) after the assessment of isokinetic strength. In the second and third weeks, the isometric and functional strength were evaluated, respectively.

From the findings of this study, the blood flow rates of the femoral artery were similar between the groups at baseline (p > 0.05) and there was no significant change after L-Arginine supplementation (p > 0.05). Similar results were observed with the area of the femoral artery. Regarding the assessment of muscle performance after supplementation, no difference was found between the groups (p > 0.05). Finally, the authors concluded that L-Arginine supplementation did not show an improvement in endothelial function and muscle performance in elderly women [Aguiar et al., 2016].

Still observing the effect of arginine supplementation in aging, Gilane et al. (2018) evaluated L-Arginine supplementation with doses of 1000 mg/day for 8 weeks in elderly men. The objective of the study was to evaluate multivariate longitudinal models in Sirtuin 6 (SIRT6), Fasting Blood Sugar (FBS) and Body Mass Index (BMI). The total sample was divided into 4 groups, each with 8 subjects, being: exercise + supplement (ES), exercise + placebo (EP), group only supplement (S), control group (C). The study showed that group ES reduced BMI and FBS and increased SIRT6 protein level, whereas group S did not show any significant improvement in BMI and FBS and there was a reduction of SIRT6 (p < 0.001). However, the authors concluded that physical activity associated with arginine supplementation can have benefits such as improved metabolism and body composition. Lower levels of SIRT6 have been associated with complications during aging, such as cardiovascular diseases, cancers and neurodegenerative diseases [Khan et al., 2018].

To evaluate this effect with acute arginine supplementation, Cancarine et al. (2018) used the same protocol as Aguiar et al. (2016) to assess the area of the femoral artery and heart rate variability in pre-hypertensive or hypertensive elderly women using Doppler ultrasound. No statistical difference was observed between placebo and the supplemented group (8 g of L-Arginine). The authors also monitored blood pressure every 10 minutes after assessing isokinetic strength for 60 minutes. From the results of diastolic pressure, it was not possible to observe statistical differences. However, as for systolic, reduced values were identified 90 minutes after L-Arginine supplementation and at 40, 50, and 60 minutes after exercise when compared to placebo. Finally, it was expected that there would be an increase in the femoral artery since arginine is related to NO synthesis and consequently to vasodilation, which did not occur.

3.3 L-Arginine supplementation and cardiovascular diseases

Only four studies (three RCTs and one review) were available in full version and were included in this review topic (Table 3).

The latest review about arginine, NO and a cardiovascular aspect was published in 2013. The authors reported that low NO´s levels and arginine deficiency were related to endothelial inflammation and immune disorders, which is directly involved with risk of CVD. They also observed that the exogenous administration of L-Arginine, despite restoring NO´s bioavailability, did not improve endothelial function in already established cardiovascular disease patients (Lorin, 2013).

Kashyap et al., 2017 were the first group to evidence that catheter directed L-Arginine therapy improved endothelial function in diseased lower extremity human arteries. These effects are secondary to increase NO bioactivity. It is important to say that the study didn’t observe adverse events related to the study protocol, including the absence of allergic reactions or hemodynamic instability. Also, considering that endothelial dysfunction is a common process in patients with atherosclerosis, the authors suggest the possible L-Arginine application in biological therapies to enhance endothelial function in atherosclerosis and chronic ischemia. However, we point out that this study was not blinded and did not use a placebo.

A study with peripheral arterial occlusive disease (PAOD) and coronary artery disease patients reported that, despite prevented loss of NO activity by saving nitrite (in PAOD patients), arginine supplementation of 10 g/day for 3 or 6 months did not alter the synthesis or bioavailability of NO. However, the authors highlight that the ideal arginine dose needs to be established and further studies are needed to investigate dose-response relationships.

After evaluating patients with atherosclerotic peripheral arterial disease of lower extremities at Fontaine’s stage II and newly diagnosed type 2 diabetes, Jablecka et al., 2012 observed lower NO concentrations in these patients (1.28 ± 0.64 µmol/l) when compared to the healthy controls (2.07 ± 0.70 µmol/l; p < 0.05). Moreover, 2-month of L-Arginine supplementation was capable to increase patients’ NO level (1.28 ± 0.64 to 2.93 ± 0.42 µmol/l; p < 0.05) and also total antioxidant status (TAS) (1.19 ± 0.38 to 1.60 ± 0.51 mmol/l; p < 0.05).

3. Discussion

Including only clinical trials and meta-analysis, this review aimed to summarize the effect of isolated arginine supplementation on the human cardiovascular system by verifying potential benefits on blood pressure (and hypertensive patients), health athletes and patients with pre-established CVDs. Research strategy led to last decade systematic reviews of the topic and studies published after (i.e. not included in the reviews).

With these new studies we could observe that oral L-Arginine supplementation has a potential benefit of BP-lowering on adults although its effects were not seen in elderly people. Individuals with hypertension exhibit endothelial dysfunction, which leads to a decreased bioavailability of NO and a high risk for CVDs. L-Arginine is the substrate for NO synthase and responsible to produce the endothelium-derived relaxing factor NO, which takes to the hypothesis that L-Arginine may have BP-lowering effect, for being involved in a wide variety of cardiovascular system regulatory mechanisms, but mainly improving endothelial function [Rainer et al, 2005]. In summary, blood pressure review topic suggests that oral arginine supplementation has potential for promoting BP-lowering effect by: 1) improving endothelial function through NO-mediated biological effects [Jablecka et al, 2012] and, 2) a trend toward positive effects on immune function through anti-inflammatory responses [Nascimento et al. 2017] in adults. However, it was not observed in an elderly sample [Beckman et al. 2018], where L-Arginine therapy impaired digital microvascular endothelial function and was associated with increased blood pressure as well as a reduction in peripheral artery endothelial function. Given the inherent low number of published studies evaluating arginine supplementation effects on blood pressure among hypertensive populations in the last decade, findings discussed in this review topic should be reevaluated in future meta-analysis.

The use of nutritional supplements that aim to maximize athletic performance is quite common. The arginine has been linked to synthesis and bioavailability of NO which in turn leads to increased blood flow and improved muscle contraction, gas exchange, oxygen kinetics, and mitochondrial biogenesis [Stamler, 2001].Moreover, arginine contributes to increased muscle mass and hypertrophy stimulating the release of growth hormone (GH) [Forbes, 2014]. A previous meta-analysis showed that Arg supplementation could have positive effects on anaerobic and aerobic performance related physical test outcomes. For acute protocols, the effective dose of Arg supplementation [0.15 g/kg (≈10–11 g)] should be ingested between 60–90 min before exercise to improve both aerobic and anaerobic disciplines. The suggested Chronic Arg supplementation in aerobic exercises should be of 1.5–2 g/day for 4–7. Higher doses (10–12 g/day for 8 weeks) were indicated for anaerobic performance[Viribayet, 2020]. Some RCTs included in our review showed a trend toward no effect of arginine supplementation in improving physical exercise parameters, but it depends on the type of exercise, population as well as dosage and management of arginine supplementation. Finally, the meta-analysis did not include any of the RCTs considered eligible in our review, probably due to differences in the search method and objectives (the BVS was not searched in the meta-analysis).

Considering people with established CVDs, exogenous arginine administration is capable of improving NO level and its bioactivity however, its direct effects on endothelial function and cardiovascular system was still controversial, showing only a trend toward positive effect on peripheral arterial disease. Thus, considering the low level of evidence generated in this topic due to low number of published studies, clinical trials need to continue to really elucidate the effects of L-Arginine supplementation on CVDs.

The benefits of L-Arginine supplementation are mainly related to its ability to increase NO level and improve endothelial function through NO-mediated biological effects. Some previously reports revealed that decreases in NO production is a possible cause of hypertension and cardiac hypertrophy [Arnal et al, 1993; Numaguchi, 1995], showing that NO levels are an essential factor involved in the development of atherosclerosis and other cardiovascular disorders. There are many factors associated with reduced biological activity of NO, such as: decreased L-Arginine uptake, decreased NOS cofactors levels (e.g. Ca2+, calmodulin, tetrahydrobiopterin), inhibition of electron flow (e.g. nicotinamide-adeninedinucleotide phosphate (NADPH), flavins), inhibition of NOS expression [Dobutovic, 2011; Desjardins, 2006] and increased ROS concentrations (e.g. superoxide anion) [Naseem, 2005]. Reduced bioavailability of NO is related to the development of various vascular disorders [Napoli, 2009; Zago, 2006], including vasoconstriction, platelet aggregation, thrombus formation, leukocyte adhesion and vascular smooth muscle cell proliferation and migration [Dobutovic, 2011; Desjardins, 2006].

It is important to note that cardiovascular disease during aging can bring some physiological consequences, including impairment of the endothelial function [Bode-Böger et al., 2003]. Some studies have investigated the effect of L-Arginine in improving endothelial dysfunction, as well as muscle performance in elderly [Aguiar et al., 2015; Cosanatto et al., 2019]. It is worth mentioning that studies with L-Arginine supplementation in elderly are scarce in the literature, considering the publications of the last decade. Of the few papers found, it was suggested that L-Arginine supplementation does not alter blood flow, even after physical activity in elderly people. Regarding blood pressure, the results were conflicting, since Beckman et al. (2018) found an association between L-Arginine and an increase in blood pressure, whereas Aguiar et al. (2016) found no significant differences. Moreover, Cancarine et al., (2019) found a decrease in systolic after the supplementation of L-Arginine associated with physical activity. Thus, further studies on the effects of L-Arginine supplementation in elderly population should be carried out, considering a larger sample size, both sexes, healthy and unhealthy, long-lasting tests, since the benefits and harms of L-Arginine supplementation are still inconclusive.

Until now there are few data in the literature which indicate direct adverse and toxic effects of L-Arginine supplementation. Only two studies reported gastrointestinal symptoms such as nausea and diarrhea [Dong et al., 2011; Tyler et. al. 2015]. A previous review evidenced that, in adults,an oral administration of L-Arginine until 20 g/day may be considered a safe dose. Also, the authors showed that L-Arginine supplementation can lead to beneficial effects and be used safely in pregnant women, preterm infants, and individuals with cystic fibrosis and chronic disease such as obesity, insulin resistance, and diabetes [McNeal et al., 2016].

4. Conclusion

Regulation of NO bioavailability after L-Arginine supplementation could lead to new strategies for the treatment of cardiovascular disorders since its effects on NO levels can have both beneficial and detrimental effects. Clinically significant adverse events were not reported. The stronger evidence about arginine effects was provided by recent systematic reviews and meta-analyses, showing that arginine improves blood pressure and aerobic and anaerobic performance. Few trials were published after those reviews, with contradictory outcomes. There is an urge for future RCTs with isolated arginine supplementation, larger numbers of patients, designed for long-lasting evaluations.

References

●Castillo, L.; Chapman, T. E.; Sanchez, M.; Yu, Y. M.; Burke, J. F.; Ajami, A. M.; Vogt, J.; Young, V. R. Plasma arginine and citrulline kinetics in adults given adequate and arginine-free diets. Proc. Natl. Acad. Sci. U.S.A., 1993, 90(16), 7749-7753.

●Castillo, L.; Ajami, A.; Branch, S.; Chapman, T. E.; Yu, Y. M.; Burke, J. F.; Young, V. R. Plasma arginine kinetics in adult man: response to an arginine-free diet. Metabolism, 1994, 43(1), 114-122.

●Wu, G.; Bazer, F. W.; Davis, T. A.; Kim, S. W.; Li, P.; Marc Rhoads, J.; Carey Satterfield, M.; Smith, S. B.; Spencer, T. E.; Yin, Y. Arginine metabolism and nutrition in growth, health and disease. Amino Acids, 2009, 37(1), 153-168.

●Visek, W. J. Arginine needs, physiological state and usual diets. A reevaluation. J. Nutr., 1986, 116(1), 36-46.

●Zuchi C, Ambrosio G, Lüscher TF, Landmesser U. Nutraceuticals in cardiovascular prevention: lessons from studies on endothelial function. Cardiovasc Ther. 2010;28(4):187-201.

●Popovic PJ, Zeh III HJ, Ochoa JB. Arginine and immunity. J Nutr. 2007;137(6 Suppl 2):1681S-1686S.

●Kalil AC, Danner RL. L-Arginine supplementation in sepsis: beneficial or harmful? Curr Opin Crit Care. 2006;12(4):303- 308

●Newsholme, P.; Homem De Bittencourt, P.I.; C, O.H.; De Vito, G.; Murphy, C.; Krause, M.S. Exercise and possible molecular mechanisms of protection from vascular disease and diabetes: the central role of ROS and nitric oxide. Clin. Sci. (Lond.) 2009, 118, 341–349.

●Ouzzani M; Hammady H; Fedorowicz Z; Elmagarmid A. Rayyan — a web and mobile app for systematic reviews. Systematic Reviews (2016) 5:210, DOI: 10.1186/s13643-016-0384-4

●Rainer et al, Arginine Improves Vascular Function by Overcoming the Deleterious Effects of ADMA, a Novel Cardiovascular Risk Factor. 2005.

●Efron DT, Barbul A. Modulation of inflammation and immunity by arginine supplements. Curr Opin Clin Nutr Metab Care 1998;1:531e8.

●Rajendran P, Chen YF, Chen YF, et al. The multifaceted link between inflammation and human diseases. J Cell Physiol. 2018;233(9):6458-6471. doi:10.1002/jcp.26479

●Dartora DR, de Moraes OA, Cruz PL, Sangaleti C, Irigoyen MC, Consolim- Colombo F. Autonomic nervous system, hypertension and inflammation. Ver Hipertens 2015;18:11e9.

●Aitor Viribayet al. Effects of Arginine Supplementation on Athletic Performance Based on Energy Metabolism: A Systematic Review and Meta-Analysis. Nutrients 2020, 12, 1300

●Stamler, J. S., & Meissner, G. (2001). Physiology of Nitric Oxide in Skeletal Muscle. Physiological Reviews, 81(1), 209–237.

● Forbes, S. C., Harber, V., & Bell, G. J. (2014). Oral L-Arginine before Resistance Exercise Blunts Growth Hormone in Strength Trained Males. International Journal of Sport Nutrition and Exercise Metabolism, 24(2), 236–244.

●Colombani PC, Bitzi R, Frey-Rindova P, Frey W, Arnold M, et al. (1999) Chronic arginine aspartate supplementation in runners reduces total plasma amino acid level at rest and during a marathon run. Eur J Nutr. 38 (6):263-70.

●Yavuz, H.U., Turnagol, H., and Demirel, A.H. 2014. Pre-exercise arginine supplementation increases time to exhaustion in elite male wrestlers. Biol. Sport, 31(3): 187–191.

●Doutreleau, S, Mettauer, B, Piquard, F, Schaefer, A, Lonsdorfer, E, Richard, R, and Geny, B. Chronic but not acute oral L-Arginine supplementation delays the ventilatory threshold during exercise in heart failure patients. Can J Appl Physiol 30: 419–432, 2005

● Chistensen, K. et al. Ageing populations: the challenges ahead. The Lancet, v. 374, n. 9696, p. 1196-1208, 2009.

● Martínez-Rodrígues, A. et al. Effect of Supplements on Endurance Exercise in the Older Population: Systematic Review. International Journal of Environmental Research and Public Health, v. 17, n. 14, p. 5224, 2020.

●Aguiar, A.F. et al. L-Arginine supplementation does not enhance blood flow and muscle performance in healthy and physically active older women. European journal of nutrition, v. 55, n. 6, p. 2053-2062, 2016.

●Beckman, J.A.; Hurwitz, S.; Fisher, N.D.L. Arginine impairs endothelial and executive function in older subjects with cardiovascular risk. Journal of the American Society of Hypertension, v. 12, n. 10, p. 723-731, 2018.

●Casonatto, J. et al. L-Arginine supplementation improves post-exercise hypotension in elderly women. Revista Brasileira de Medicina do Esporte, v. 25, n. 4, p. 333-337, 2019.

●Maxwell AJ, Ho HV, Le CQ, Lin PS, Bernstein D, Cooke JP (2001) L-Arginine enhances aerobic exercise capacity in association with augmented nitric oxide production. J Appl Physiol 90:933–938

●Preli, R. B., Klein, K. P., & Herrington, D. M. (2002). Vascular effects of dietary L-Arginine supplementation. Atherosclerosis, 162(1), 1–15. doi:10.1016/s0021-9150(01)00717-1

●Khan, R.I.; Nirzhir, S.S.R.; Akter, R. A review of the recent advances made with SIRT6 and its implications on aging related processes, major human diseases, and possible therapeutic targets. Biomolecules, v. 8, n. 3, p. 44, 2018.

●Gilani, N.; Haghshenas, R.; Esmaeili, M. Application of multivariate longitudinal models in SIRT6, FBS, and BMI analysis of the elderly. The Aging Male, v. 22, n. 4, p. 260-265, 2018.

●Arnal, J. F.; el Amrani, A. I.; Chatellier, G.; Menard, J.; Michel, J.B. Cardiac weight in hypertension induced by nitric oxide synthase blockade. Hypertension, 1993, 22(3), 380-387.

●Numaguchi, K.; Egashira, K.; Takemoto, M.; Kadokami, T.;Shimokawa, H.; Sueishi, K.; Takeshita, A. Chronic inhibition of nitric oxide synthesis causes coronary microvascular remodeling in rats. Hypertension, 1995, 26(6 Pt 1), 957-962

●Napoli, C.; Ignarro, L. J. Nitric oxide and pathogenic mechanisms involved in the development of vascular diseases. Arch. Pharm. Res., 2009, 32(8), 1103-1108.

●Zago, A. S.; Zanesco, A. Nitric oxide, cardiovascular disease and physical exercise. Arq. Bras. Cardiol., 2006, 87(6), e264-270

●Dobutovic, B.; Smiljanic, K.; Soskic, S.; Düngen, H.-D.; Isenovic, E. R. Nitric Oxide and its Role in Cardiovascular Diseases. The Open Nitric Oxide J., 2011, 3, 65-71

●Desjardins, F.; Balligand, J. L. Nitric oxide-dependent endothelial function and cardiovascular disease. Acta Clin. Belg., 2006, 61(6), 326-334.

●Naseem, K. M. The role of nitric oxide in cardiovascular diseases. Mol. Aspects Med., 2005, 26(1-2), 33-65.

●Donato, A. J.; Machin, D. R.; Lesniewski, L. A. Mechanisms of dysfunction in the aging vasculature and role in age-related disease. Circulation research, v. 123, n. 7, p. 825-848, 2018.

●PahlavaniN et al. The effect of l-arginine supplementation on body composition and performance in male athletes: a double-blinded randomized clinical trial. Eur J Clin Nutr. 2017 Apr;71(4):544-548.

●Mor, A., Atan, T., Agaoglu, S.A. and Ayyildiz, M. 2018. Effect of arginine supplementation on footballers’ anaerobic performance and recovery. Progress in Nutrition. 20, 1 (Mar. 2018), 104-112.

●Zembron-Lacny A, et al. Intermittent Hypoxic Exposure with High Dose of Arginine Impact on Circulating Mediators of Tissue Regeneration. Nutrients. 2020 Jul; 12(7): 1933.

●Holowatz LA, Thompson CS, Kenney WL (2006) l-Arginine supplementation or arginase inhibition augments reflex cutaneous vasodilatation in aged human skin. J Physiol 574:573–581

●Bode-Böger SM, Muke J, Surdacki A, Brabant G, Böger RH, Frölich JC (2003) Oral l-arginine improves endothelial function in healthy individuals older than 70 years. Vasc Med 8:77–81

●Taddei S, Galetta F, Virdis A, Ghiadoni L, Salvetti G, Franzoni F (2000) Physical activity prevents age-related impairment in nitric oxide availability in elderly athletes. Circulation 101:2896–2901

Declarations of Conflicts of Interest: None.

Declaration of Sources of Funding: None

Figure Legend

Figure 1. PRISMA flowchart

Table 1. Data extraction from studies of Arginine and Blood Pressure topic.

Table 2. Data extraction from studies of Arginine and physical exercise topic.

Table 3. Data extraction from studies of Arginine and Cardiovascular Disease topic.