The influence of arginine supplementation on IGF-1: A systematic review and meta-analysis.

BACKGROUND: Insulin-like growth factor-1 (IGF-1) secretion is thought to be induced by a semi-essential amino acid called arginine (Arg). Existing research on the effect of Arg on IGF-1 levels has provided conflicting results. This systematic review and meta-analysis investigated the efficacy of acute and chronic Arg supplementation on IGF-1 levels. METHODS: PubMed, Web of Science, and Scopus were systematically searched until November 2022. The meta-analysis was performed using random- and fixed-effects models. Sensitivity and subgroup analyses were also carried out. Publication bias was assessed using Begg's test. RESULTS: Nine studies were included in this meta-analysis. Chronic Arg supplementation did not significantly change IGF-1 levels (SMD = 0.13 ng/ml; %95 CI: -0.21, 0.46; p = 0.457). Furthermore, the IGF-1 level was not significantly affected by acute Arg supplementation (SMD = 0.10 ng/mL; CI: -0.42, 0.62; p = 0.713). The meta-analysis results did not change following subgroup analyses based on the duration, dosage, age, placebo, and study population. CONCLUSION: In conclusion, there was no significant effect of Arg supplementation on IGF-1 concentration. The meta-analyses revealed no acute or chronic Arg supplementation impact on IGF-1 levels.

The effect of Tribulus terrestris supplementation on inflammation, oxidative stress, and performance of recreational runners: study protocol for a randomized placebo-controlled trial.

BACKGROUND: High intensity and endurance exercises lead to exercise-induced oxidative stress (EIOS), exercise-induced muscle damage (EIMD), and inflammation, which are the influencing factors on muscle soreness, localized swelling, and sports performance decrease. Therefore, the purpose of this study is to determine the effectiveness of Tribulus terrestris (TT) as an herbal supplement with antioxidant and anti-inflammatory properties on the nutritional, oxidative, inflammatory, and anti-inflammatory status, as well as the sports performance of recreational runners. METHODS/DESIGN: This study is a double-blind, randomized, placebo-controlled trial, which will be conducted among recreational runners of Tabriz stadiums, Iran. Thirty-four recreational runners will be selected, and participants will be assigned randomly to two groups: to receive 500 mg TT supplement or placebo capsules twice daily for 2 weeks. Both groups will do high-intensity interval training (HIIT) workouts during the study. Baseline and post-intervention body composition, muscle pain, and aerobic and anaerobic performance will be assessed. In addition, assessment of malondialdehyde (MDA), total antioxidant capacity (TAC), total oxidant status (TOS), superoxide dismutase (SOD), glutathione peroxidase (GPx), uric acid (UA), 8-iso-prostaglandin F2α (8-iso-PGF2α), protein carbonyl (PC), catalase (CAT), glutathione (GSH), nitric oxide (NO), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), creatine kinase (CK), myoglobin (MYO), lactate dehydrogenase (LDH), insulin-like growth factor-1 (IGF-1) irisin, cortisol, and brain-derived neurotrophic factor (BDNF) will be done during three blood samplings. Changes in oxidative stress, anti/inflammatory biomarkers, and sports performance will be assessed as primary outcomes. DISCUSSION: This study will be the first to assess the potential effects of TT on recreational runners. Our results will contribute to the growing body of knowledge regarding TT supplementation on the nutritional, oxidative, inflammatory, and anti-inflammatory status and sports performance in recreational runners. TRIAL REGISTRATION: Iranian Registry of Clinical Trials ( www.irct.ir ) (ID: IRCT20150205020965N8 ). Registration date: 13 February 2021.

The effects of N-acetylcysteine on recovery biomarkers: A systematic review and meta-analysis of controlled trials.

N-acetylcysteine (NAC) is one of the antioxidant supplements which is thought to improve recovery. Existing studies regarding NAC and recovery presented conflicting results. This systematic review and meta-analysis evaluated the existing trials and determined the efficacy of acute and chronic NAC administration on recovery biomarkers. PubMed, Web of Science, and Scopus were searched up to July 2021. The random effects or fixed effects model was applied in the meta-analysis. Sensitivity and subgroup analyses were performed. In case of the presence of publication bias, standard methods were applied. The meta-analysis comprised 37 papers (1,388 participants). All included studies were in English language. Acute NAC administration indicated no significant effects on lactate, pH, VO2 , and CPK-MB ([SMD = -0.06 mmol/L; 95% CI: -0.40, 0.28; p = .714], [SMD = 0.17; 95% CI: -0.28, 0.62; p = .454], [SMD = -0.11 L/min; 95% CI: -0.63, 0.41; p = .686], and [SMD = -0.19 units/L; 95% CI: -0.62, 0.24; p = .395]). Additionally, no evidence of significant influence of chronic NAC administration on lactate, pH, VO2 , and CK was revealed ([SMD = 0.01 mmol/L; 95% CI: -0.25, 0.27; p = .950], [SMD = -0.51; 95% CI: -1.73, 0.70; p = .424], [SMD = -0.18 L/min; 95% CI: -0.56, 0.20; p = .361], and [SMD = -0.04 units/L; 95% CI: -0.36, 0.29; p = .821]). No considerable effect of NAC on recovery was found. PRACTICAL APPLICATIONS: Previous studies on the influence of NAC administration on recovery biomarkers have presented conflicting results. This systematic review and meta-analysis offers a broad range of detailed information on the influence of chronic and acute NAC supplementation outcomes regarding recovery biomarkers. Overall, the results support that NAC supplementation may not be effective in improving recovery biomarkers. However, subgroup analyses based on NAC dosage indicated the meaningful effect of NAC on CK-MB at the dosage of ≥100 mg/kg.