Hemodynamic and Lactate Response to Exhaustive Exercise with L-Arginine Supplementation

Introduction: To further understand the effects of L-arginine on both its ability to enhance lactate clearance and increase overall blood flow before, during, and after exhaustive anaerobic exercise. Methods: Twelve healthy male subjects between the ages of 18-25 first completed an initial visit where baseline data was recorded. Subjects completed three additional visits, in which they ingested either a placebo, two-gram or four-gram dose of L-arginine. Blood flow (BF) and lactate were recorded before ingestion of the treatment, 5 and 15-minutes post-ingestion prior to performing a push-up test to volitional fatigue. Immediately following the push-up test, BF and lactate were assessed and again 15-minutes post exercise. Results: Blood lactate did not differ across condition (p=0.569). Lactate clearance was not influenced by L-arginine when analyzing the Area Under Curve. Blood flow increased with ingestion of the four-gram dose while at rest (the 15-minute mark). Blood flow was also enhanced in the four-gram dose immediately after exercise at the 25-minute mark. Conclusions: The data suggests that a four-gram dose of L-arginine plays a more significant role in blood flow than the clearance of lactate after exercise compared to a two-gram dose or placebo.

Dietary Arginine Supplementation Improves Intestinal Mitochondrial Functions in Low-Birth-Weight Piglets but Not in Normal-Birth-Weight Piglets

Our previous studies revealed that L-arginine supplementation had beneficial effects on intestinal barrier functions of low-birth-weight (LBW) piglets, which were associated with the enhanced antioxidant capacity. Moreover, mitochondrial functions are closely related to the redox state. This study was to explore potential mechanisms of L-arginine-induced beneficial effects against intestinal dysfunction by regulating mitochondrial function of LBW piglets. Twenty 4-day-old normal birth weight (NBW) piglets (BW: 2.08 ± 0.09 kg) and 20 LBW siblings (BW: 1.16 ± 0.07 kg) were artificially fed either a basal diet or a basal diet supplemented with 1.0% L-arginine for 21 d, respectively. Growth performance, intestinal morphology, redox status, mitochondrial morphology, and mitochondrial functions were examined. Data were subjected to two-way analysis of variance. LBW piglets presented lower (p < 0.05) ADG, shorter (p < 0.05) intestinal villus height, lower (p < 0.05) jejunal adenosine triphosphate (ATP) content and higher (p < 0.05) concentrations of Ca2+ and 8-OH-dG in jejunal mitochondria, compared with NBW piglets. Supplementation with 1.0% L-arginine significantly increased (p < 0.05) ADG, the activities of CAT, SOD, and GPx, intestinal villus height and mRNA abundances of ZO-1 (2-fold) in the jejunum of LBW piglets, but not in NBW piglets. Furthermore, the concentrations of ATP and the transcription of COX IV, COX V genes were up-regulated (p < 0.05) and the concentration of Ca2+ and 8-OH-dG were decreased (p < 0.05) in arginine-treated LBW piglets. The results suggest that mitochondrial morphology is affected, and mitochondrial functions are impaired in the jejunum of LBW piglets. While supplementation with 1.0% L-arginine relieved intestinal dysfunction through enhancing antioxidant capacity and improving mitochondrial functions via repairing mitochondrial morphology, normalizing mitochondrial calcium, and increasing ATP concentration in the jejunum of LBW piglets. However, supplementation with L-arginine has no significant beneficial effects on intestinal health in NBW piglets.

L-Arginine Supplementation for Nulliparous Sows during the Last Third of Gestation

We evaluated the effects of L-arginine supplementation during the last third of gestation on molecular mechanisms related to skeletal muscle development of piglets and litter traits at birth. Twenty-three nulliparous sows averaging 205.37 ± 11.50 kg of body weight were randomly assigned to the following experimental treatments: control (CON), where pregnant sows were fed diets to meet their nutritional requirements; arginine (ARG), where sows where fed CON + 1.0% L-arginine. Skeletal muscle from piglets born from sows from ARG group had greater mRNA expression of MYOD (p = 0.043) and MYOG (p ≤ 0.01), and tended to present greater mRNA expression (p = 0.06) of IGF-2 gene compared to those born from CON sows. However, there were no differences (p > 0.05) in the histomorphometric variables of fetuses’ skeletal muscle. The total weight of born piglets, total weight of born alive piglets, piglet weight at birth, coefficient of variation of birth weight, and the incidence of intrauterine growth restriction (IUGR) piglets did not differ between groups. No stillborn piglets (p < 0.01) were verified in the ARG sows compared to CON group. The blood levels of estradiol (p = 0.035) and urea (p = 0.03) were higher in ARG sows compared to those from the CON group. In summary, our data show that arginine supplementation of nulliparous sows at late gestation enhance mRNA expression of key myogenic regulatory factors, which likely contribute to improve animal growth rates in later stages of development.

Effectiveness of acute L-arginine supplementation on physical performance in strength training: a systematic review and meta-analysis

Background: The oral administration of L-arginine has been related to improved physical performance due to a likely reduction in muscle fatigue, resulting from the vasodilator effect of nitric oxide on skeletal muscle. However, there is no precise and quantitative analysis of the information in the literature. The main objective of this study was to assess the effectiveness of L-arginine supplementation on physical performance in strength training with a systematic review and meta-analysis. We hypothesized that L-arginine supplementation would improve performance capacity and the effects involved in strength training. Methods: The study period was from 2010 to 2020. The inclusion process established articles with well-designed human experiments that included only L-arginine supplementation (without any additional compounds) testing the effects of L-arginine supplementation on sports performance related to strength training; identical experimental conditions in placebo or control group; and publications in the last ten years (until December 31, 2020). Three studies were included that compared L-arginine supplementation with placebo in anaerobic performance tests. Test analysis supplementation with other supplements was removed and there was no gender, age, and ethnicity level. Results: There was no significant heterogeneity (p>0.05) in the analysis of the three selected articles and the effects of L-arginine supplementation in muscular endurance; performance had a mean of 0.26 (95% CI = -0.129; 0.649; p = 0.190), peak torque with a mean of -0.002 (95% CI = -0.531; 0.527; p = 0. 99) of the third series of exercises and, furthermore, when comparing the integrated effect (resistance rate with the peak torque) there was no difference with a mean of 0.168 (95% CI = -0.145; 0.481; p = 0.292). Conclusions: Acute L-arginine supplementation provides no ergogenic effect on strength training performance.

The Functional DNA Methylation Signatures Relevant to Altered Immune Response of Neonatal T Cells with l-Arginine Supplementation

l-Arginine is an important nutrient in the infant diet that significantly regulates the maturation of the immune system in neonates, including the maturation of CD4+ T cells. The biological activities of CD4+ T cells differ substantially between neonates and adults, and these differences may be governed by epigenetic processes. Investigating these differences and the causative processes may help understand neonatal and developmental immunity. In this study, we compared the functional DNA methylation profiles in CD4+ T cells of neonates and adults, focusing on the role of l-arginine supplementation. Umbilical cord blood and adult CD4+ T cells were cultured with/without l-arginine treatment. By comparing DNA methylation in samples without l-arginine treatment, we found that CD4+ T cells of neonatal cord blood generally showed higher DNA methylation than those of adults (average CpG methylation percentage 0.6305 for neonate and 0.6254 for adult, t-test p-value < 0.0001), suggesting gene silencing in neonates. By examining DNA methylation patterns of CpG dinucleotides induced by l-arginine treatment, we found that more CpG dinucleotides were hypomethylated and more genes appeared to be activated in neonatal T-cells as compared with adult. Genes activated by l-arginine stimulation of cord blood samples were more enriched regarding immune-related pathways. CpG dinucleotides at IL-13 promoter regions were hypomethylated after l-arginine stimulation. Hypomethylated CpG dinucleotides corresponded to higher IL-13 gene expression and cytokine production. Thus, DNA methylation partially accounts for the mechanism underlying differential immune function in neonates. Modulatory effects of l-arginine on DNA methylation are gene-specific. Nutritional intervention is a potential strategy to modulate immune function of neonates.