Six-Week Oral Guanidinoacetic Acid Administration Improves Muscular Performance in Healthy Volunteers

Safety of Dietary Guanidinoacetic Acid: A Villain of a Good Guy?

Guanidinoacetic acid (GAA) is a natural amino acid derivative that is well-recognized for its central role in the biosynthesis of creatine, an essential compound involved in cellular energy metabolism. GAA (also known as glycocyamine or betacyamine) has been investigated as an energy-boosting dietary supplement in humans for more than 70 years. GAA is suggested to effectively increase low levels of tissue creatine and improve clinical features of cardiometabolic and neurological diseases, with GAA often outcompeting traditional bioenergetics agents in maintaining ATP status during stress. This perhaps happens due to a favorable delivery of GAA through specific membrane transporters (such as SLC6A6 and SLC6A13), previously dismissed as un-targetable carriers by other therapeutics, including creatine. The promising effects of dietary GAA might be countered by side-effects and possible toxicity. Animal studies reported neurotoxic and pro-oxidant effects of GAA accumulation, with exogenous GAA also appearing to increase methylation demand and circulating homocysteine, implying a possible metabolic burden of GAA intervention. This mini-review summarizes GAA toxicity evidence in human nutrition and outlines functional GAA safety through benefit-risk assessment and multi-criteria decision analysis.

The Effects of Creatine and Related Compounds on Cardiovascular System: From Basic to Applied Studies

Beneficial effects of creatine were firstly shown in sport, where itself has been recognized as an ergogenic substance, increasing exercise endurancе, muscle strength and lean body mass. Creatine supplementation is very interesting, due to the fact that creatine supplementation have been reported to be beneficial for wide spectrum of diseases and conditions referring neuro-degenerative, rheumatic diseases, myopathies, cancer, type 2 diabetes. Creatine is a principle component of the creatine kinase/phosphagen system. In cardiomyocytes, it plays an important role in the buffering and transport of chemical energy to ensure that supply meets the dynamic demands of the heart. Studies in mice proved that elevated creatine protects the heart from ischemia-reperfusion injury. A natural precursor of creatine, guanidinoacetic acid (GAA), plays an important role as an energy carrier/mediator in the cell. GAA is formed in the first step of creatine synthesis. Supplementation with GAA might be of great significance in some circumstances where biosynthesis of GAA is limited like deficient diet, kidney failure, renal insufficiency, exercise-related GAA depletion. Betaine is a neutral compound in the form of zwitterion. Betaine supplementation is associated with improved cognition, neuroprotection, cardioprotection and exercise physiology. Betaine insufficiency represents increased risk for secondary heart failure and acute myocardial infarction. This mini-review outlines the evidence in support of creatine and creatine related compounds (GAA and betaine) elevation and examines the pharmacological approaches that are currently available. Since data from the available studies, regarding cardioprotection are inconsistent, this review might help clarifying the benefits of creatine, GAA and betaine supplementation on cardiovascular system.

Guanidinoacetic Acid Regulates Myogenic Differentiation and Muscle Growth Through miR-133a-3p and miR-1a-3p Co-mediated Akt/mTOR/S6K Signaling Pathway

Guanidinoacetic acid (GAA), an amino acid derivative that is endogenous to animal tissues including muscle and nerve, has been reported to enhance muscular performance. MicroRNA (miRNA) is a post-transcriptional regulator that plays a key role in nutrient-mediated myogenesis. However, the effects of GAA on myogenic differentiation and skeletal muscle growth, and the potential regulatory mechanisms of miRNA in these processes have not been elucidated. In this study, we investigated the effects of GAA on proliferation, differentiation, and growth in C2C12 cells and mice. The results showed that GAA markedly inhibited the proliferation of myoblasts, along with the down-regulation of cyclin D1 (CCND1) and cyclin dependent kinase 4 (CDK4) mRNA expression, and the upregulation of cyclin dependent kinase inhibitor 1A (P21) mRNA expression. We also demonstrated that GAA treatment stimulated myogenic differentiation 1 (MyoD) and myogenin (MyoG) mRNA expression, resulting in an increase in the myotube fusion rate. Meanwhile, GAA supplementation promoted myotube growth through increase in total myosin heavy chain (MyHC) protein level, myotubes thickness and gastrocnemius muscle cross-sectional area. Furthermore, small RNA sequencing revealed that a total of eight miRNAs, including miR-133a-3p and miR-1a-3p cluster, showed differential expression after GAA supplementation. To further study the function of miR-133a-3p and miR-1a-3p in GAA-induced skeletal muscle growth, we transfected miR-133a-3p and miR-1a-3p mimics into myotube, which also induced muscle growth. Through bioinformatics and a dual-luciferase reporter system, the target genes of miR-133a-3p and miR-1a-3p were determined. These two miRNAs were shown to modulate the Akt/mTOR/S6K signaling pathway by restraining target gene expression. Taken together, these findings suggest that GAA supplementation can promote myoblast differentiation and skeletal muscle growth through miR-133a-3p- and miR-1a-3p-induced activation of the AKT/mTOR/S6K signaling pathway.

Dietary guanidinoacetic acid does not accumulate in the brain of healthy men

We conducted a secondary analysis of a previously completed trial to determine the effects of 8-week guanidinoacetic acid (GAA) loading on brain GAA levels in five healthy men. Brain magnetic resonance spectroscopy (1H-MRS) was taken at baseline and post-administration, with spectra additionally analyzed for brain GAA and glutamate concentrations using TARQUIN 4.3.10 software. Brain GAA levels remained essentially unchanged at follow-up (an increase of 7.7% from baseline levels; 95% confidence interval, - 24.1% to 39.5%; P = 0.88) when averaged across 12 white and grey matter voxel locations. No significant changes were found for brain glutamate levels during the study (P = 0.64). Supplemental GAA appears to be safe intervention concerning brain GAA deposition, at least with GAA dosages used.

Supplementation with Guanidinoacetic Acid in Women with Chronic Fatigue Syndrome

A variety of dietary interventions has been used in the management of chronic fatigue syndrome (CFS), yet no therapeutic modality has demonstrated conclusive positive results in terms of effectiveness. The main aim of this study was to evaluate the effects of orally administered guanidinoacetic acid (GAA) on multidimensional fatigue inventory (MFI), musculoskeletal soreness, health-related quality of life, exercise performance, screening laboratory studies, and the occurrence of adverse events in women with CFS. Twenty-one women (age 39.3 ± 8.8 years, weight 62.8 ± 8.5 kg, height 169.5 ± 5.8 cm) who fulfilled the 1994 Centers for Disease Control and Prevention criteria for CFS were randomized in a double-blind, cross-over design, from 1 September 2014 through 31 May 2015, to receive either GAA (2.4 grams per day) or placebo (cellulose) by oral administration for three months, with a two-month wash-out period. No effects of intervention were found for the primary efficacy outcome (MFI score for general fatigue), and musculoskeletal pain at rest and during activity. After three months of intervention, participants receiving GAA significantly increased muscular creatine levels compared with the placebo group (36.3% vs. 2.4%; p < 0.01). Furthermore, changes from baseline in muscular strength and aerobic power were significantly greater in the GAA group compared with placebo (p < 0.05). Results from this study indicated that supplemental GAA can positively affect creatine metabolism and work capacity in women with CFS, yet GAA had no effect on main clinical outcomes, such as general fatigue and musculoskeletal soreness.

Guanidinoacetic acid as a performance-enhancing agent

Guanidinoacetic acid (GAA; also known as glycocyamine or guanidinoacetate) is the natural precursor of creatine, and under investigation as a novel dietary agent. It was first identified as a natural compound in humans ~80 years ago. In the 1950s, GAA's use as a therapeutic agent was explored, showing that supplemental GAA improved patient-reported outcomes and work capacity in clinical populations. Recently, a few studies have examined the safety and efficacy of GAA and suggest potential ergogenic benefits for physically active men and women. The purpose of this review is to examine possible applications of GAA supplementation for exercise performance enhancement, safety, and legislation issues.