Dietary Arginine and Citrulline Supplements for Cardiovascular Health and Athletic Performance: A Narrative Review

Nutritional Status and Ergogenic Aids in Performance During Exercise and Sports

The interaction between nutritional status, ergogenic aids, and athletic performance has long been a central focus in sports science [...].

L-Arginine and Nitric Oxide in Vascular Regulation-Experimental Findings in the Context of Blood Donation

This narrative review provides an analysis of the role of nitric oxide (NO) and its precursors, particularly L-arginine, in vascular regulation and health, with an emphasis on findings from our experimental research in animal models. NO serves as a critical mediator of vascular function, contributing to vasodilation, the regulation of blood flow, and the prevention of thrombosis. As a primary precursor of NO, L-arginine is essential for maintaining endothelial integrity, modulating mitochondrial function, and reducing oxidative damage. This review synthesises the data and contextualises these findings within the physiological challenges faced by blood donors, such as repeated blood donation and associated oxidative stress. It examines the effects of L-arginine supplementation on mitochondrial respiration, lipid peroxidation, and microsomal oxidation in different conditions, including differences in age, gender, and dietary interventions. The mechanisms by which L-arginine enhances NO production, improves vascular elasticity, and alleviates endothelial dysfunction caused by reduced NO bioavailability are also investigated. By integrating experimental findings with insights from the existing literature, this review provides a perspective on the potential of L-arginine supplementation to address the specific physiological needs of blood donors. It highlights the importance of personalised nutritional approaches in enhancing donor recovery and vascular resilience. In addition, this review assesses the wider implications of L-arginine supplementation in mitigating oxidative stress and preserving vascular function. The interplay between NO bioavailability, dietary factors, and physiological adaptation in blood donors is highlighted, along with the identification of current knowledge gaps and recommendations for future research. By presenting both original experimental evidence and a critical synthesis of the literature, this article highlights the therapeutic potential of NO precursors, particularly L-arginine, in promoting vascular health in the context of blood donation.

Nanoparticles for Biomedical Use Derived from Natural Biomolecules: Tannic Acid and Arginine

Background/Objectives: Tannic acid (TA) is a well-known natural phenolic acid composed of ten gallic acids linked to each other with ester bonding possessing excellent antioxidant properties in addition to antimicrobial and anticancer characteristics. Arginine (ARG) is a positively charged amino acid at physiological pH because of nitrogen-rich side chain. Method: Here, poly(tannic acid-co-arginine) (p(TA-co-ARG)) particles at three mole ratios, TA:ARG = 1:1, 1:2, and 1:3, were prepared via a Mannich condensation reaction between TA and ARG by utilizing formaldehyde as a linking agent. Results: The p(TA-co-ARG) particles in 300-1000 nm size range with smooth surfaces visualized via SEM analysis were attained. Abundant numbers of functional groups, -OH, -NH2, and -COOH stemming from TA and ARG constituent confirmed by FT-IR analysis. The isoelectric point (IEP) of the particles increased from pH 4.98 to pH 7.30 by increasing the ARG ratios in p(TA-co-ARG) particles. The antioxidant capacity of p(TA-co-ARG) particles via gallic acid (GA) and rosmarinic acid (RA) equivalents tests revealed that particles possess concentration-dependent antioxidant potency and increased by TA content. The α-glucosidase inhibition of p(TA-co-ARG) particles (2 mg/mL) 1:1 and 1:2 mole ratios revealed significant enzyme inhibition ability, e.g., 91.3 ± 3.1% and 77.6 ± 12.0%. Interestingly, p(TA-co-ARG) (1:3 ratio) possessed significant antibacterial effectiveness against Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC 6538) bacteria. Furthermore, all p(TA-co-ARG) particles at 1000 mg/mL concentration showed >80% toxicity on L929 fibroblast cells and increased as ARG content of p(TA-co-ARG) particles is increased. Conclusions: p(TA-co-ARG) showed significant potential as natural biomaterials for biomedical use.

The potential role of amino acids in myopia: inspiration from metabolomics

BACKGROUND

Due to the high prevalence of myopia, there is a growing need for the identification of myopia intervention mechanisms and targets. Metabolomics has been gradually used to investigate changes in myopia tissue metabolites over the last few years, but the potential physiological and pathological roles of amino acids and their downstream metabolites discovered by metabolomics in myopia are not fully understood.

AIM OF REVIEW

Aim to explore the possible relationship between amino acid metabolism and the occurrence and development of myopia, we collected a total of 21 experimental studies related to myopia metabolomics. Perform pathway analysis using MetaboAnalyst online software. We have identified over 20 amino acids that may be associated with the development of myopia. Among them, 19 types of amino acids are common amino acids. We discussed their possible mechanisms affecting myopia and proposed future prospects for treating myopia.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Our analysis results show that metabolomics research on myopia involves many important amino acids. We have collected literature and found that research on amino acid metabolism in myopia mainly focuses on downstream small molecule substances. Amino acids and their downstream metabolites affect the development of myopia by participating in important biochemical processes such as oxidative stress, glucose metabolism, and lipid metabolism. Enzymes, receptors, and cytokines that regulate amino acid metabolism may become potential targets for myopia treatment.

Exercise-Induced Central Fatigue: Biomarkers, and Non-Medicinal Interventions

Fatigue, commonly experienced in daily life, is a feeling of extreme tiredness, shortage or lack of energy, exhaustion, and difficulty in performing voluntary tasks. Central fatigue, defined as a progressive failure to voluntarily activate the muscle, is typically linked to moderate- or light-intensity exercise. However, in some instances, high-intensity exercise can also trigger the onset of central fatigue. Exercise-induced central fatigue often precedes the decline in physical performance in well-trained athletes. This leads to a reduction in nerve impulses, decreased neuronal excitability, and an imbalance in brain homeostasis, all of which can adversely impact an athlete's performance and the longevity of their sports career. Therefore, implementing strategies to delay the onset of exercise-induced central fatigue is vital for enhancing athletic performance and safeguarding athletes from the debilitating effects of fatigue. In this review, we discuss the structural basis, measurement methods, and biomarkers of exercise-induced central fatigue. Furthermore, we propose non-pharmacological interventions to mitigate its effects, which can potentially foster improvements in athletes' performances in a healthful and sustainable manner.

Crushing Muscles: A Case Study on Rhabdomyolysis, Renal Failure, and Compartment Syndrome Triggered by Pre-Workout Supplement Abuse

The use of steroids and protein-based dietary supplements for muscle enhancement is prevalent in contemporary society. While these products promise increased muscle mass and strength, they carry significant risks, including severe medical complications. The consumption of these supplements has been linked to adverse symptoms, including dehydration, gastrointestinal distress, dizziness, and alterations in heart rate and blood pressure, primarily due to ingredients like creatine, arginine, and caffeine. Following the proper dosage, ensuring adequate hydration, and consulting a healthcare provider to verify if the supplement's components could affect any pre-existing conditions is recommended. Indiscriminate use of these products, including taurine, can lead to serious side effects. We present a 36-year-old patient with severe rhabdomyolysis, life-threatening acid-base imbalance, renal and liver injury, and peripheral neuropathy associated with the use of performance-enhanced unregulated supplements and exercise. This case highlights the importance of recognizing and managing complications related to exercise-aid supplements, emphasizing early identification and management. Increasing social awareness and research on those products is highly needed to avoid supplement-associated complications and potential long-term disabilities.

Recommendations and guidelines of integrative medicine for COVID-19 care: The APEC project outcome

This article - Recommendations and Guidelines of Integrative Medicine (IM) for COVID-19 Care - was one of the outcomes from an Asia-Pacific Economic Cooperation (APEC) Project (Integrative Medicine (IM) and COVID -19 Care) during the time between May 2022 and March 2023. With the efforts from care providers, researchers, health policy makers and healthcare administrative leaders among APEC economies, the purpose of this file was to provide comprehensive IM systems for COVID-19 care as recommendations and suggestive guidelines including care methods, tools, procedures, symptom conditions and targets selections, and points need to be considered during care applications. All cited COVID-19 care practices have confirmed their efficacy and usefulness either used alone or combined with conventional medicine. This article provides current useful medical information on IM for COVID-19 care which could benefit APEC economies and world health communities on their healthcare system.

Gut microbiota and its metabolic products in acute respiratory distress syndrome

The prevalence rate of acute respiratory distress syndrome (ARDS) is estimated at approximately 10% in critically ill patients worldwide, with the mortality rate ranging from 17% to 39%. Currently, ARDS mortality is usually higher in patients with COVID-19, giving another challenge for ARDS treatment. However, the treatment efficacy for ARDS is far from satisfactory. The relationship between the gut microbiota and ARDS has been substantiated by relevant scientific studies. ARDS not only changes the distribution of gut microbiota, but also influences intestinal mucosal barrier through the alteration of gut microbiota. The modulation of gut microbiota can impact the onset and progression of ARDS by triggering dysfunctions in inflammatory response and immune cells, oxidative stress, cell apoptosis, autophagy, pyroptosis, and ferroptosis mechanisms. Meanwhile, ARDS may also influence the distribution of metabolic products of gut microbiota. In this review, we focus on the impact of ARDS on gut microbiota and how the alteration of gut microbiota further influences the immune function, cellular functions and related signaling pathways during ARDS. The roles of gut microbiota-derived metabolites in the development and occurrence of ARDS are also discussed.

Phytochemical analysis and biological evaluation of Ferulago setifolia K. Koch

BACKGROUND

Ferulago setifolia K. Koch (Apiaceae) has been the subject of this study, aiming to comprehensively determine its phenolic fingerprint and evaluate its various biological activities. The liquid chromatography-tandem mass spectrometry analysis of the 70% methanol extract of F. setifolia (FS) revealed the presence of 23 phytochemicals, among which chlorogenic acid, quinic acid, kaempferol-3-O-glucoside, and quercetin-3-O-glucoside were identified as the major phenolics in the extract.

RESULTS

The biological screening included examinations of antioxidant, antibacterial, antiproliferative, and cytotoxic activities. The FS extract displayed moderate 2,2-diphenyl-1-picrylhydrazyl radical scavenging and ferric-reducing capacity, indicating moderate antioxidant activity. Furthermore, FS exhibited significant antiproliferative effects on cancer cells while showing low cytotoxicity on normal cells. The antibacterial activity findings revealed that FS demonstrated potent activity against Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, and Escherichia coli.

CONCLUSION

The findings of this study suggest that the methanolic extract of FS holds promise as a potential source of biologically active compounds. It can be utilized for the development of pharmaceutical formulations, thanks to its significant antiproliferative and antibacterial activities. Additionally, FS can serve as a valuable source of chlorogenic acid for industrial applications. © 2023 Society of Chemical Industry.

The Effectiveness of L-arginine in Clinical Conditions Associated with Hypoxia

The review summarises the data of the last 50 years on the effectiveness of the amino acid L-arginine in therapeutic practice in conditions accompanied by different-origin hypoxia. The aim of this review was to analyse the literature and our research data on the role of nitric oxide in the modulation of individual physiological reactivity to hypoxia. The review considers the possibility of eliminating methodological conflicts in the case of L-arginine, which can be solved by taking into account individual physiological reactivity (or the hypoxia resistance factor). Considerable attention is paid to genetic and epigenetic mechanisms of adaptation to hypoxia and conditions of adaptation in different models. The article presents data on the clinical effectiveness of L-arginine in cardiovascular system diseases (hypertension, atherosclerosis, coronary heart disease, etc.) and stress disorders associated with these diseases. The review presents a generalised analysis of techniques, data on L-arginine use by athletes, and the ambiguous role of NO in the physiology and pathology of hypoxic states shown via nitric oxide synthesis. Data on the protective effects of adaptation in the formation of individual high reactivity in sportsmen are demonstrated. The review demonstrates a favourable effect of supplementation with L-arginine and its application depending on mitochondrial oxidative phosphorylation processes and biochemical indices in groups of individuals with low and high capacity of adaptation to hypoxia. In individuals with high initial anti-hypoxic reserves, these favourable effects are achieved by the blockade of NO-dependent biosynthesis pathways. Therefore, the methodological tasks of physiological experiments and the therapeutic consequences of treatment should include a component depending on the basic level of physiological reactivity.

Short-Term L-Citrulline Supplementation Does Not Affect Inspiratory Muscle Oxygenation and Respiratory Performance in Older Adults

In sports nutrition, nitric oxide (NO^•) precursors such as L-citrulline are widely used to enhance NO^• bioavailability, which is considered an ergogenic aid. Our study aimed to examine the effect of short-term L-citrulline supplementation on respiratory muscles' performance, fatigue, and oxygenation in older adults. Fourteen healthy older males took 6 g of L-citrulline or a placebo for seven days in a double-blind crossover design. Pulmonary function via spirometry (i.e., forced expired volume in 1 s (FEV₁), forced vital capacity (FVC), and their ratio)), fractional exhaled nitric oxide (NO^•), maximal inspiratory pressure (MIP), rate of perceived exertion, and sternocleidomastoid muscle oxygenation (i.e., oxyhemoglobin (Δ[O₂Hb]) and de-oxyhemoglobin (Δ[HHb]), total hemoglobin concentration (Δ[tHb]), and tissue saturation index (TSI%)) were evaluated at baseline, after seven days of L-citrulline supplementation, and after incremental resistive breathing to task failure of the respiratory muscles. The exhaled NO^• value was only significantly increased after the supplementation (26% p < 0.001) in the L-citrulline condition. Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation. In the present study, although short-term L-citrulline supplementation increased exhaled NO^•, no ergogenic aids were found on the examined parameters at rest and after resistive breathing to task failure in older adults.