Guanidinoacetic acid as a performance-enhancing agent

The Difference in Serum Metabolomic Profiles between the Good and Poor Outcome Groups at 3 Months in the Early and Late Phases of Aneurysmal Subarachnoid Hemorrhage

We aimed to investigate the characteristics of serum metabolomics in aneurysmal subarachnoid hemorrhage patients (aSAH) with different 3-month outcomes (good = modified Rankin score: 0-3 vs. poor = mRS 4-6). We collected serum samples from 46 aSAH patients at 24 (D1) and 168 (D7) hours after injury for analysis by liquid chromatography-mass spectrometry. Ninety-six different metabolites were identified. Groups were compared using multivariate (orthogonal partial least squares discriminant analysis), univariate, and receiving operator characteristic (ROC) methods. We observed a marked decrease in serum homocysteine levels at the late phase (D7) compared to the early phase (D1). At both D1 and D7, mannose and sorbose levels were notably higher, alongside elevated levels of kynurenine (D1) and increased 2-hydroxybutyrate, methyl-galactoside, creatine, xanthosine, p-hydroxyphenylacetate, N-acetylalanine, and N-acetylmethionine (all D7) in the poor outcome group. Conversely, levels of guanidinoacetate (D7) and several amino acids (both D1 and D7) were significantly lower in patients with poor outcomes. Our results indicate significant changes in energy metabolism, shifting towards ketosis and alternative energy sources, both in the early and late phases, even with adequate enteral nutrition, particularly in patients with poor outcomes. The early activation of the kynurenine pathway may also play a role in this process.

Dietary Methionine Enhances Portal Appearance of Guanidinoacetate and Synthesis of Creatine in Yucatan Miniature Piglets

BACKGROUND

Creatine plays a significant role in energy metabolism and positively impacts anaerobic energy capacity, muscle mass, and physical performance. Endogenous creatine synthesis requires guanidinoacetic acid (GAA) and methionine. GAA can be an alternative to creatine supplements and has been tested as a beneficial feed additive in the animal industry. When pigs are fed GAA with excess methionine, creatine is synthesized without feedback regulation. In contrast, when dietary methionine is limited, creatine synthesis is limited, yet, GAA does not accumulate in plasma, urine, or liver.

OBJECTIVE

We hypothesized that portal GAA appearance requires adequate dietary methionine.

METHODS

Yucatan miniature piglets (17-21 d old; n = 20) were given a 4 h duodenal infusion of complete elemental diets with supplemental GAA plus 1 of 4 methionine concentrations representing either 20%, 80%, 140%, or 200% of the dietary methionine requirement. Arterial and portal blood metabolites were measured along with blood flow to determine mass balance across the gut. [3H-methyl] methionine was infused to measure the methionine incorporation rate into creatine.

RESULTS

GAA balance across the gut was highest in the 200% methionine group, indicating excess dietary methionine enhanced GAA absorption. Creatine synthesis in the liver and jejunum was higher with higher concentrations of methionine, emphasizing that the transmethylation of GAA to creatine depends on sufficient dietary methionine. Hepatic GAA concentration was higher in the 20% methionine group, suggesting low dietary methionine limited GAA conversion to creatine, which led to GAA accumulation in the liver.

CONCLUSIONS

GAA absorption and conversion to creatine require a sufficient amount of methionine, and the supplementation strategies should accommodate this interaction.

Guanidinoacetic acid ameliorates hepatic steatosis and inflammation and promotes white adipose tissue browning in middle-aged mice with high-fat-diet-induced obesity

Guanidinoacetic acid (GAA) is a naturally occurring amino acid derivative that plays a critical role in energy metabolism. In recent years, a growing body of evidence has emerged supporting the importance of GAA in metabolic dysfunction. Hence, we aimed to investigate the effects of GAA on hepatic and adipose tissue metabolism, as well as systemic inflammatory responses in obese middle-aged mice models and attempted to explore the underlying mechanism. We found that dietary supplementation of GAA inhibited inguinal white adipose tissue (iWAT) hypertrophy in high-fat diet (HFD)-fed mice. In addition, GAA supplementation observably decreased the levels of some systemic inflammatory factors, including IL-4, TNF-α, IL-1β, and IL-6. Intriguingly, GAA supplementation ameliorated hepatic steatosis and lipid deposition in HFD-fed mice, which was revealed by decreased levels of TG, TC, LDL-C, PPARγ, SREBP-1c, FASN, ACC, FABP1, and APOB and increased levels of HDL-C in the liver. Moreover, GAA supplementation increased the expression of browning markers and mitochondrial-related genes in the iWAT. Further investigation showed that dietary GAA promoted the browning of the iWAT via activating the AMPK/Sirt1 signaling pathway and might be associated with futile creatine cycling in obese mice. These results indicate that GAA has the potential to be used as an effective ingredient in dietary interventions and thus may play an important role in ameliorating and preventing HFD-induced obesity and related metabolic diseases.

Investigation of metabolite alterations in the kidneys of methionine-choline-deficient mouse by mass spectrometry imaging

Methionine and choline both are essential nutrients which are needed for methyl group metabolism. A methionine-choline-deficient (MCD) diet leads to pathological changes in the kidney. The mechanism of the MCD diet is complex, and fundamental research is still required to provide a better understanding of the driving forces behind it. We evaluated the regional effects of the MCD diet on the metabolites of mouse kidney tissue using desorption electrospray ionization mass spectrometry imaging technology. A total of 20, 17, and 13 metabolites were significantly changed in the cortex, outer medulla, and inner medulla, respectively, of the mouse kidney tissue after the administration of the MCD diet. Among the discriminating metabolites, only three metabolites (guanidoacetic acid, serine, and nicotinamide riboside) were significantly increased, and all the other metabolites showed a significant decrease. The results showed that there were significant region-specific changes in the serine metabolism, carnitine metabolism, choline metabolism, and arginine metabolism. This study presents unique regional metabolic data, providing a more comprehensive understanding of the molecular characteristics of the MCD diet in the kidney.

Effect of guanidinoacetic acid on the growth performance, myofiber, and adenine nucleotide of meat-type rabbits

OBJECTIVE

This study aimed to investigate the effect of dietary guanidinoacetic acid (GAA) on the growth performance, slaughter traits, myofiber, and adenine nucleotide of meat-type rabbits.

METHODS

Experimental treatments consisted of control (CON) and GAA addition at 0.04% (T1), 0.08% (T2), and 0.12% (T3) of diet. A total of 240 weaned rabbits (meat-type male Chinese black rabbits) were randomly distributed into four groups with six replicates of ten rabbits each.

RESULTS

Results showed that the three doses of GAA increased (p<0.05) final body weight, carcass weight, the density and area of quadriceps femoris fiber; and T3 showed significant effects (p<0.05) on weight gain, feed/gain, and dressing percentage, and the traits of longissimus fiber, compared to CON. Dietary GAA increased (p<0.05) the meat color a* and b* in longissimus and quadriceps; and T3 showed the lowest (p<0.05) shear force of longissimus. Furthermore, GAA increased (p<0.05) the contents of adenosine triphosphate and total adenine nucleotide in longissimus and quadriceps. In longissimus adenosine triphosphate, total adenine nucleotide, and adenylate energy charges, T3 treatment was most effective (p<0.05); while T2 and T3 treatment was more effective (p<0.05) than T1 in quadriceps. Additionally, linear or quadratic responses (p<0.05) to the increased doses of GAA were found on body weight gain, meat color, total adenine nucleotide, and adenylate energy charges.

CONCLUSION

It is concluded that GAA can be used in the rabbit diet to improve growth and carcass traits, and these are related to the high levels of muscle adenine nucleotide.

Guanidine Acetic Acid Alters Tissue Bound Amino Acid Profiles and Oxidative Status in Finishing Pigs

This study aims to investigate the effects of guanidine acetic acid (GAA) on carcass traits, plasma biochemical parameters, tissue antioxidant capacity, and tissue-bound amino acid contents in finishing pigs. Seventy-two 140-day-old (body weight 86.59 ± 1.16 kg) crossbred pigs (Duroc × Landrace × Large White) were randomly assigned into four treatments with six replicate pens and three pigs per pen, which were fed the basal diets supplemented with 0, 0.05%, 0.10%, or 0.15% GAA, respectively. The plasma glucose concentration decreased, and creatine kinase activity and levels of GAA and creatine increased with the dietary GAA concentration. GAA linearly improved creatine content in the longissimus thoracis muscle (LM) and heart. The activities of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase increased linearly in tissue or/and plasma, while the contents of malondialdehyde and protein carbonyl decreased linearly. GAA improved the contents of multiple-bound amino acids (such as proline or isoleucine) in the myocardium and LM. In conclusion, GAA enhanced the plasma biochemical parameters, oxidative status, and bound amino acid profiles of the heart and LM in finishing pigs.

Serum metabolomics reveals the effects of accompanying treatment on fatigue in patients with multiple myeloma

PURPOSE

The renewal and iteration of chemotherapy drugs have resulted in more frequent long-term remissions for patients with multiple myeloma (MM). MM has transformed into a chronic illness for many patients, but the cancer-related fatigue (CRF) of many MM convalescent patients experience is frequently overlooked. We investigated whether the accompanying treatment of family members would affect MM patients' CRF and explore their serum metabolomics, so as to provide clinicians with new ideas for identifying and treating CRF of MM patients.

METHODS

This was a single-center study, and a total of 30 MM patients were included in the study. Patients were divided into two groups based on whether they have close family members accompanying them through the whole hospitalization treatment. These patients received regular chemotherapy by hematology specialists, and long-term follow-up was done by general practitioners. Patients' CRF assessment for several factors used the Chinese version of the Brief Fatigue Inventory (BFI-C). Face-to-face questionnaires were administered at a time jointly determined by the patient and the investigator. All questionnaires were conducted by a general practitioner. The LC-MS-based metabolomics analysis determined whether the patients' serum metabolites were related to their fatigue severity. A correlation analysis investigated the relationship between serum metabolites and clinical laboratory indicators.

RESULTS

The fatigue severity of MM patients whose family members participated in the treatment process (group A) was significantly lower than patients whose family members did not participate in the treatment process (group B). There was a statistically significant difference (fatigue severity composite score: t =  - 2.729, p = 0.011; fatigue interference composite score: t =  - 3.595, p = 0.001). There were no differences between the two groups of patients' gender, age, regarding clinical staging, tumor burden, blood routine, biochemical, or coagulation indexes. There were 11 metabolites, including guanidine acetic acid (GAA), 1-(Methylthio)-1-hexanethiol, isoeucyl-asparagine, L-agaritine, tryptophyl-tyrosine, and betaine, which significantly distinguished the two groups of MM patients. GAA had the strongest correlation with patient fatigue, and the difference was statistically significant (fatigue severity composite score: r = 0.505, p = 0.0044; fatigue interference composite score: r = 0.576, p = 0.0009). The results showed that GAA negatively correlated with albumin (r =  - 0.4151, p = 0.0226) and GGT (r =  - 0.3766, p = 0.0402). Meanwhile, GAA positively correlated with PT (r = 0.385, p = 0.0473), and the difference was statistically significant.

CONCLUSION

The study is the first to report that family presence throughout the whole hospitalization may alleviate CRF in MM patients. Moreover, the study evaluated serum metabolites linked to CRF in MM patients and found that CRF has a significant positive correlation with GAA. GAA may be a more sensitive biomarker than liver enzymes, PT, and serum albumin in predicting patient fatigue. While our sample may not represent all MM patients, it proposes a new entry point to help clinicians better identify and treat CRF in MM patients.

Guanidine acetic acid supplementation altered plasma and tissue free amino acid profiles in finishing pigs

Background

As a nutritive feed additive, guanidine acetic acid (GAA) participates in the metabolism of energy and proteins. This study aimed to investigate the effects of GAA on growth performance, organ index, plasma and tissue free amino acid profiles, and related metabolites in finishing pigs. A total of 72 crossbred pigs (body weight 86.59 ± 1.16 kg) were randomly assigned to 1 of 4 dietary treatments (GAA0, GAA500, GAA1000, and GAA1500). They were fed the basal diets supplemented with 0, 500, 1000, or 1500 mg/kg GAA for 42 days, respectively. The growth performance and organ weight were evaluated, and the contents of crude protein, free amino acids, and metabolites in plasma and tissues were determined. Spearman correlation between plasma and tissue free amino acids and related metabolites was also analyzed.

Results

Growth performance in pigs was not altered by GAA (P > 0.05). The absolute and relative weight of kidneys increased (quadratic, P < 0.05). As dietary GAA concentration was increased, the contents of plasma glycine, serine, leucine, ornithine, and ratio of ornithine/arginine decreased (linear or quadratic, P < 0.05), but the contents of plasma isoleucine and taurine and the ratios of alanine/branched-chain amino acids and proline/ornithine increased quadratically (P < 0.05). The hepatic γ-amino-n-butyric acid content increased linearly and quadratically (P < 0.001), while the carnosine content decreased (quadratic, P = 0.004). The contents of renal arginine, proline, cystine, glutamate, and total amino acids (TAA) decreased quadratically (P < 0.05), but the contents of glycine (quadratic, P = 0.015) and γ-amino-n-butyric acid (linear, P = 0.008) increased. The pancreatic tryptophan content (quadratic, P = 0.024) increased, while the contents of pancreatic proline (linear, P = 0.005) and hydroxyproline (quadratic, P = 0.032) decreased in response to GAA supplementation. The contents of cardiac essential amino acids (EAA), nonessential amino acids (NEAA), and TAA in GAA1000 were higher than those in GAA1500 (P < 0.05). Supplementing with GAA linearly increased the contents of methionine, threonine, valine, isoleucine, leucine, phenylalanine, tryptophan, lysine, histidine, arginine, serine, alanine, glutamine, asparagine, tyrosine, proline, taurine, cystathionine, α-aminoadipic acid, β-aminoisobutyric acid, EAA, NEAA, and TAA in the spleen (P < 0.05). A strong Spearman correlation existed between plasma and tissue free amino acids and related metabolites.

Conclusion

GAA supplementation did not altered pig growth performance, but it altered plasma and tissue free amino acid profiles and the contents of related metabolites in pigs in a tissue-dependent manner.

Biosynthesis of a New Fusaoctaxin Virulence Factor in Fusarium graminearum Relies on a Distinct Path To Form a Guanidinoacetyl Starter Unit Priming Nonribosomal Octapeptidyl Assembly

Fusarium graminearum is a pathogenic fungus causing huge economic losses worldwide via crop infection leading to yield reduction and grain contamination. The process through which the fungal invasion occurs remains poorly understood. We recently characterized fusaoctaxin A in F. graminearum, where this octapeptide virulence factor results from an assembly line encoded in fg3_54, a gene cluster proved to be involved in fungal pathogenicity and host adaptation. Focusing on genes in this cluster that are related to fungal invasiveness but not to the biosynthesis of fusaoctaxin A, we here report the identification and characterization of fusaoctaxin B, a new octapeptide virulence factor with comparable activity in wheat infection. Fusaoctaxin B differs from fusaoctaxin A at the N-terminus by possessing a guanidinoacetic acid (GAA) unit, formation of which depends on the combined activities of the protein products of fgm1-3. Fgm1 is a cytochrome P450 protein that oxygenates l-Arg to 4(R)-hydroxyl-l-Arg in a regio- and stereoselective manner. Then, C_β-C_γ bond cleavage proceeds in the presence of Fgm3, a pyridoxal-5'-phosphate-dependent lyase, giving guanidinoacetaldehyde and l-Ala. Rather than being directly oxidized to GAA, the guanidine-containing aldehyde undergoes spontaneous cyclization and subsequent enzymatic dehydrogenation to provide glycociamidine, which is linearized by Fgm2, a metallo-dependent amidohydrolase. The GAA path in F. graminearum is distinct from that previously known to involve l-Arg:l-Gly aminidotransferase activity. To provide this nonproteinogenic starter unit that primes nonribosomal octapeptidyl assembly, F. graminearum employs new chemistry to process l-Arg through inert C-H bond activation, selective C-C bond cleavage, cyclization-based alcohol dehydrogenation, and amidohydrolysis-associated linearization.

Performance, Carcass Yield, Muscle Amino Acid Profile, and Levels of Brain Neurotransmitters in Aged Laying Hens Fed Diets Supplemented with Guanidinoacetic Acid

Guanidinoacetic acid (GA) is a natural precursor of creatine in the body and is usually used to improve the feed conversion and cellular energy metabolism of broiler chickens. The objective was to elucidate the effect of dietary supplementation of GA on carcass yield, muscle amino acid profile, and concentrations of brain neurotransmitters in laying hens. In total, 128 72-week-old ISA Brown laying hens were assigned to four equal groups (32 birds, eight replicates per group). The control group (T₁) was fed a basal diet with no supplements, while the other experimental groups were fed a basal diet supplemented with 0.5 (T₂), 1.0 (T₃), and 1.5 (T₄) g GA kg^-1 diet. The T₃ and T₄ groups showed higher hen-day egg production and carcass yield compared to the control group (p = 0.016 and 0.039, respectively). The serum creatine level increased linearly with the increased level of dietary GA (p = 0.007). Among the essential amino acids of breast muscle, a GA-supplemented diet linearly increased the levels of leucine, isoleucine, phenylalanine, methionine, and threonine in the breast (p = 0.003, 0.047, 0.001, 0.001, and 0.015, respectively) and thigh (p = 0.026, 0.001, 0.020, 0.009, and 0.028, respectively) muscles. GA supplementation linearly reduced the level of brain serotonin compared to the control group (p = 0.010). Furthermore, supplementation of GA in the diet of laying hens linearly increased the level of brain dopamine (p = 0.011), but reduced the level of brain Gamma-aminobutyric acid (p = 0.027). Meanwhile, the concentration of brain nitric oxide did not differ between the experimental groups (p = 0.080). In conclusion, the dietary supplementation of GA may improve the carcass yield and levels of essential amino acids in the breast muscles, as well as the brain neurotransmitters in aged laying hens.

Regulative Mechanism of Guanidinoacetic Acid on Skeletal Muscle Development and Its Application Prospects in Animal Husbandry: A Review

Guanidinoacetic acid is the direct precursor of creatine and its phosphorylated derivative phosphocreatine in the body. It is a safe nutritional supplement that can be used to promote muscle growth and development. Improving the growth performance of livestock and poultry and meat quality is the eternal goal of the animal husbandry, and it is also the common demand of today's society and consumers. A large number of experimental studies have shown that guanidinoacetic acid could improve the growth performance of animals, promote muscle development and improve the health of animals. However, the mechanism of how it affects muscle development needs to be further elucidated. This article discusses the physical and chemical properties of guanidinoacetic acid and its synthesis pathway, explores its mechanism of how it promotes muscle development and growth, and also classifies and summarizes the impact of its application in animal husbandry, providing a scientific basis for this application. In addition, this article also proposes future directions for the development of this substance.

Effects of guanidinoacetic acid and complex antioxidant supplementation on growth performance, meat quality, and antioxidant function of broiler chickens

BACKGROUND

This study was conducted to evaluate the effects of adding guanidinoacetic acid (GAA), or complex antioxidant (CA), or their combination, in diets on the growth performance, carcass traits, meat quality, and antioxidant capacity of broilers. A total of 192 25-day-old broilers were assigned to a 2 × 2 factorial design including two dietary supplements at two different levels, in which the main effects were the addition of GAA (0 or 600 mg kg^-1 ) and CA (0 or 150 mg kg^-1 ). This trial lasted for 18 days.

RESULTS

Compared with the control group, the GAA group, CA group, and GAA + CA group, decreased feed conversion ratio by 7.02%, 6.58%, and 11.40%, respectively. Guanidinoacetic supplementation increased eviscerated yield, pH_24h (P < 0.05). Complex antioxidant supplementation increased the a* values (P < 0.05). The combination of GAA and CA did not affect the carcass traits and meat quality. Guanidinoacetic acid alone and CA alone and combined with GAA and CA decreased the reactive oxygen species (ROS) level and malonaldehyde (MDA) content (P < 0.05), and the GAA + CA group had the lowest ROS level and MDA content of broilers.

CONCLUSION

Dietary supplementation of GAA, CA or their combination had beneficial effects on growth performance and breast antioxidant capacity, and the combination of GAA and CA could exert a synergistic effect in improving antioxidant capacity. © 2020 Society of Chemical Industry.

Guanidino-Acetic Acid: A Scarce Substance in Biomass That Can Regulate Postmortem Meat Glycolysis of Broilers Subjected to Pre-slaughter Transportation

The different substances in biomass can regulate the metabolism and reproduction of broilers. Guanidino-acetic acid (GAA) is a natural feed additive that showed a potential application in dietary for broilers, while its amount is scarce in biomass. The objective of the present study was to investigate the effects of dietary supplemented with GAA on muscle glycolysis of broilers subjected to pre-slaughter transportation. A total of 160 Qiandongnan Xiaoxiang chickens were randomly assigned into three treatments, including a basal control diet without GAA supplementation (80 birds) or supplemented with 600 mg/kg (40 birds) or 1,200 mg/kg (40 birds) GAA for 14 days. At the end of the experiment, the control group was equally divided into two groups, thus resulting in four groups. All birds in the four groups aforementioned were separately treated according to the following protocols: (1) no transport of birds of the control group fed with the basal diet; (2) a 3-h transport of birds of the control group fed with the basal diet; (3) a 3-h transport of birds fed with diets supplemented with 600 mg/kg GAA; and (4) a 3-h transport of birds fed with diets supplemented with 1,200 mg/kg GAA. The results demonstrated that 3-h pre-slaughter transport stress increased corticosterone contents and lowered glucose contents in plasma (P < 0.05), decreased pH_{24 h} (P < 0.05), and resulted in inferior meat quality evidenced by elevating the drip loss, cooking loss, and L^∗ value (P < 0.05). Meanwhile, 3-h pre-slaughter transport stress decreased the contents of Cr and ATP in muscle (P < 0.05) and elevated the ratio of AMP:ATP and the glycolytic potential of muscle (P < 0.05). Moreover, 3-h pre-slaughter transport resulted in a significant elevation of mRNA expressions of LKB1 and AMPKα2 (P < 0.05), as well as the increase in protein abundances of LKB1 phosphorylation and AMPKα phosphorylation (P < 0.05). However, 1,200 mg/kg GAA supplementation alleviated negative parameters in plasma, improved meat quality, and ameliorated postmortem glycolysis and energy metabolism through regulating the creatine-phosphocreatine cycle and key factors of AMPK signaling. In conclusion, dietary supplementation with 1,200 mg/kg GAA contributed to improving meat quality via ameliorating muscle energy expenditure and delaying anaerobic glycolysis of broilers subjected to the 3-h pre-slaughter transport.

Reconstitution of the Ornithine Cycle with Arginine:Glycine Amidinotransferase to Engineer Escherichia coli into an Efficient Whole-Cell Catalyst of Guanidinoacetate

Guanidino compounds can be synthesized by transamidination reactions using arginine as a guanidine group donor. The efficiency of guanidino biosynthesis is often affected by the supply of arginine and the inhibition of the coproduct ornithine. To alleviate this shortcoming, we designed a reconstituted ornithine cycle in Escherichia coli to engineer an efficient whole-cell catalyst for guanidinoacetate (GAA) production by introducing a heterogeneous arginine:glycine amidinotransferase (AGAT). To alleviate the inhibition of ornithine, a citrulline synthetic module was constructed and optimized by introducing a glutamine self-sufficient system. Then, to improve the pathway from citrulline to arginine, an aspartate self-sufficient system was introduced into the arginine synthetic module. By combining these modules (GAA, citrulline, and arginine synthetic modules), a reconstituted ornithine cycle was developed, which significantly improved the biocatalyst efficiency (3.9-fold increase). In the system, arginine was regenerated efficiently through the reconstituted ornithine cycle, which converted arginine from a substrate to a cofactor for the transamidination reaction, thereby relieving the ornithine inhibition. Moreover, the amidino group of GAA in this system was mainly supplied by carbon and nitrogen assimilation. After the engineering process, 8.61 g/L GAA (73.56 mM) with a productivity of 0.39 g/L/h was achieved in a 22 h bioconversion. To the best of our knowledge, this is the first time that GAA has been produced in E. coli. This reconstructed ornithine cycle could be used as a transamidination platform for amidino group supply and has potential applications in the biosynthesis of other guanidino compounds.

The Potential of Guanidino Acetic Acid to Reduce the Occurrence and Severity of Broiler Muscle Myopathies

Guanidinoacetic acid (GAA) is the biochemical precursor of creatine, which, in its phosphorylated form, is an essential high-energy carrier in the muscle. Although creatine has limited stability in feed processing, GAA is well established as a source of creatine in the animal feed industry. Published data demonstrate beneficial effects of GAA supplementation on muscle creatine, energy compounds, and antioxidant status, leading to improvements in broiler body weight gain, feed conversion ratio, and breast meat yield. Although increases in weight gain and meat yield are often associated with wooden breast (WB) and other myopathies, recent reports have suggested the potential of GAA supplementation to reduce the occurrence and severity of WB while improving breast meat yield. This disorder increases the hardness of the Pectoralis major muscle and has emerged as a current challenge to the broiler industry worldwide by impacting meat quality. Genetic selection, fast-growth rates, and environmental stressors have been identified to be the main factors related to this myopathy, but the actual cause of this disorder is still unknown. Creatine supplementation has been used as a nutritional prescription in the treatment of several muscular myopathies in humans and other animals. Because GAA is a common feed additive in poultry production, the potential of GAA supplementation to reduce broiler myopathies has been investigated in experimental and commercial scenarios. In addition, a few studies have evaluated the potential of creatine in plasma and blood enzymes related to creatine to be used as potential markers for WB. The evidence indicates that GAA could potentially minimize the incidence of WB. More data are warranted to understand the factors affecting the potential efficacy of GAA to reduce the occurrence and severity of myopathies.

Nutritional modulation of fertility in male poultry

The increased consumption of protein derived from poultry demands greater poultry production, but increased poultry production (meat and eggs) is dependent on the fertility of the parent flocks. Clearly, the fertility of poultry flocks is associated with the fertility of both males and females, but the low numbers of males used for natural or artificial insemination mean that their role is more important. Thus, enhancing the semen volume, sperm concentration, viability, forward motility, and polyunsaturated fatty acids in sperm, as well as protecting against oxidative damage, could help to optimize the sperm membrane functionality, mitochondrial activity, and sperm-egg penetration, and thus fertility. Therefore, this review summarizes the nutritional factors that could improve the fertility of poultry males as well as their associated mechanisms to allow poultry producers to overcome low-fertility problems, especially in aging poultry males, thereby obtaining beneficial impacts on the poultry production industry.

From broiler breeder hen feed to the egg and embryo: The molecular effects of guanidinoacetate supplementation on creatine transport and synthesis

Supplementation of broiler breeder hens with beneficial additives bears great potential for affecting nutrient deposition into the fertile egg. Guanidinoacetate (GAA) is the endogenous precursor of creatine that is used as a feed additive for improving cellular energy metabolism in animal nutrition. In the present study, we have investigated whether GAA supplementation in broiler breeder feed affects creatine deposition into the hatching egg and molecular mechanisms of creatine transport and synthesis within hens and their progeny. For this, broiler breeder hens of 47 wk of age were supplemented with 0.15% GAA for 15 wk, and samples from their tissues, hatching eggs and progeny were compared with those of control, nonsupplemented hens. A significant increase in creatine content was found within the yolk and albumen of hatching eggs obtained from the GAA group, compared with the control group. The GAA group exhibited a significant increased creatine transporter gene expression compared with the control group in their small intestines and oviduct. In GAA group progeny, a significant decrease in creatine transporter expression at embryonic day 19 and day of hatch was found, compared with control group progeny. At the day of hatch, creatine synthesis genes (arginine glycine amidinotransferase and guanidinoacetate N-methyltransferase) exhibited significant decrease in expression in the GAA group progeny compared with control group progeny. These results indicate that GAA supplementation in broiler breeder feed increases its absorbance and deposition into hatching eggs, subsequently affecting GAA and creatine absorbance and synthesis within broiler progeny.

Human gut microbiota as a source of guanidinoacetic acid

Guanidinoacetic acid (GAA) is a natural amino acid derivative that acts as a precursor of creatine while being synthesized and utilized in a two-step reaction that takes place in the human kidney and liver. In this paper, we have proposed that guanidinoacetase, an enzyme present in healthy gut microbiota, might contribute to gross GAA turnover by hydrolyzing GAA to glycine and urea or vice versa. Additional studies are thus needed to assess a net gain of this microbiota-driven GAA pathway that may account for energy metabolism homeostasis in general.

Guanidinoacetic acid deficiency: a new entity in clinical medicine?

Guanidinoacetic acid (GAA, also known as glycocyamine or betacyamine) is a naturally-occurring derivative of glycine and a direct metabolic precursor of creatine, a key player in high-phosphate cellular bioenergetics. GAA is found in human serum and urine, with circulating GAA likely reflects an equilibrium between its endogenous production and utilization/excretion. GAA deficiency (as indicated by low serum GAA) has been reported in various conditions yet this intriguing clinical entity appears to be poorly characterized as yet, either as a primary deficit or a sequel of secondary disease. This minireview article summarizes the inherited and acquired disorders with apparent GAA deficiency and discusses a possible relevance of GAA shortfall in clinical medicine.

Age-Related Changes in Serum Guanidinoacetic Acid in Women

Guanidinoacetic acid (GAA) is a fundamental intermediate in cellular bioenergetics, with circulating levels of GAA often reflects disturbances in its conversion due to many intrinsic and extrinsic factors, including gender or age. Here, we evaluated serum GAA in 172 healthy women aged 18 to 65 years, with age found to significantly predict serum GAA concentrations (r=0.29; P=0.03). This perhaps nominates serum GAA as a novel gender-specific proxy of impaired bioenergetics with aging.

Effects of guanidinoacetic acid on growth performance, creatine metabolism and plasma amino acid profile in broilers

The objective of this study was to assess the effects of guanidinoacetic acid (GAA) on growth performance, creatine deposition and blood amino acid (AA) profile on broiler chickens. In Exp. 1, a total of 540 one-day-old Arbor Acres male broilers (average initial body weight, 45.23 ± 0.35 g) were divided randomly into five treatments with six replicates of 18 chicks each. Broilers were fed corn-soybean meal-basal diets supplemented with 0, 600, 800, 1,000 or 1,200 mg/kg GAA for 42 days respectively. Results showed that dietary GAA inclusion increased average daily gain (ADG) and improved gain-to-feed ratio (G:F) from 1 to 42 days (p < 0.01). However, average daily feed intake was unaffected by dietary supplementation of GAA. As GAA inclusion increased, the contents of creatine in plasma and kidney were increased (linear, p < 0.01), while the contents of GAA and creatine in liver were decreased (linear, p < 0.01). Similarly, GAA supplementation was inversely related to concentrations of most essential AA in plasma. In Exp. 2, a total of 432 one-day-old Arbor Acres male broilers (average initial body weight, 39.78 ± 0.58 g) were divided randomly into four treatments with six replicates of 18 chicks each. Birds were fed a corn-soybean meal-basal diet supplemented with 0, 200, 400 or 600 mg/kg GAA for 42 days respectively. Dietary inclusion of 600 mg/kg GAA significantly increased ADG and G:F of broilers (p < 0.05). In conclusion, dietary supplementation of 600-1,200 mg/kg GAA can effectively improve the growth performance in broiler chickens by affecting creatine metabolism and utilization efficiency of essential AA, and 600 mg/kg GAA is the minimum dose for improving performance.

Creatine Monohydrate and Guanidinoacetic Acid Supplementation Affects the Growth Performance, Meat Quality, and Creatine Metabolism of Finishing Pigs

This study aimed to investigate the effects of creatine monohydrate (CMH) and guanidinoacetic acid (GAA) supplementation on the growth performance, meat quality, and creatine metabolism of finishing pigs. The pigs were randomly allocated to three treatment groups: the control group, CMH group, and GAA group. In comparison to the control group, CMH treatment increased average daily feed intake and GAA treatment increased average daily feed intake and average daily gain of pigs. In addition, CMH and GAA treatment increased pH_45 min, myofibrillar protein solubility, and calpain 1 mRNA expression level and decreased the drip loss and shear force value in longissimus dorsi or semitendinosus muscle. Moreover, CMH and GAA supplementation increased the concentrations of creatine and phosphocreatine and the mRNA expressions of guanidinoacetate N-methyltransferase and creatine transporter in longissimus dorsi muscle, semitendinosus muscle, liver, or kidneys and decreased the mRNA expressions of arginine:glycine amidinotransferase in kidneys. In conclusion, CMH and GAA supplementation could improve the growth performance and meat quality and alter creatine metabolism of finishing pigs.

A role for nutritional intervention in addressing the aging neuromuscular junction

The purpose of this review is to discuss the structural and physiological changes that underlie age-related neuromuscular dysfunction and to summarize current evidence on the potential role of nutritional interventions on neuromuscular dysfunction-associated pathways. Age-related neuromuscular deficits are known to coincide with distinct changes in the central and peripheral nervous system, in the neuromuscular system, and systemically. Although many features contribute to the age-related decline in neuromuscular function, a comprehensive understanding of their integration and temporal relationship is needed. Nonetheless, many nutrients and ingredients show promise in modulating neuromuscular output by counteracting the age-related changes that coincide with neuromuscular dysfunction. In particular, dietary supplements, such as vitamin D, omega-3 fatty acids, β-hydroxy-β-methylbutyrate, creatine, and dietary phospholipids, demonstrate potential in ameliorating age-related neuromuscular dysfunction. However, current evidence seldom directly assesses neuromuscular outcomes and is not always in the context of aging. Additional clinical research studies are needed to confirm the benefits of dietary supplements on neuromuscular function, as well as to define the appropriate population, dosage, and duration for intervention.

Benefits and drawbacks of guanidinoacetic acid as a possible treatment to replenish cerebral creatine in AGAT deficiency

Arginine-glycine amidinotransferase (AGAT) deficiency is a rare inherited metabolic disorder that severely affects brain bioenergetics. Characterized by mental retardation, language impairment, and behavioral disorders, AGAT deficiency is a treatable condition, where long-term creatine supplementation usually restores brain creatine levels and improves its clinical features. In some cases of AGAT deficiency, creatine treatment might be somewhat limited due to possible shortcomings in performance and transport of creatine to the brain. Guanidinoacetic acid (GAA), a direct metabolic precursor of creatine, has recently been suggested as a possible alternative to creatine to tackle brain creatine levels in experimental medicine. AGAT patients might benefit from oral GAA due to upgraded bioavailability and convenient utilization of the compound, while possible drawbacks (e.g. brain methylation issues, neurotoxicity, and hyperhomocysteinemia) should be accounted as well.

Estimation of Chicken Intake by Adults Using Metabolomics-Derived Markers

BACKGROUND

Improved assessment of meat intake with the use of metabolomics-derived markers can provide objective data and could be helpful in clarifying proposed associations between meat intake and health.

OBJECTIVE

The objective of this study was to identify novel markers of chicken intake using a metabolomics approach and use markers to determine intake in an independent cohort.

METHODS

Ten participants [age: 62 y; body mass index (in kg/m2): 28.25] in the NutriTech food intake study consumed increasing amounts of chicken, from 88 to 290 g/d, in a 3-wk span. Urine and blood samples were analyzed by nuclear magnetic resonance and mass spectrometry, respectively. A multivariate data analysis was performed to identify markers associated with chicken intake. A calibration curve was built based on dose-response association using NutriTech data. A Bland-Altman analysis evaluated the agreement between reported and calculated chicken intake in a National Adult Nutrition Survey cohort.

RESULTS

Multivariate data analysis of postprandial and fasting urine samples collected in participants in the NutriTech study revealed good discrimination between high (290 g/d) and low (88 g/d) chicken intakes. Urinary metabolite profiles showed differences in metabolite levels between low and high chicken intakes. Examining metabolite profiles revealed that guanidoacetate increased from 1.47 to 3.66 mmol/L following increasing chicken intakes from 88 to 290 g/d (P < 0.01). Using a calibration curve developed from the NutriTech study, chicken intake was calculated through the use of data from the National Adult Nutrition Survey, in which consumers of chicken had a higher guanidoacetate excretion (0.70 mmol/L) than did nonconsumers (0.47 mmol/L; P < 0.01). A Bland-Altman analysis revealed good agreement between reported and calculated intakes, with a bias of -30.2 g/d. Plasma metabolite analysis demonstrated that 3-methylhistidine was a more suitable indicator of chicken intake than 1-methylhistidine.

CONCLUSIONS

Guanidoacetate was successfully identified and confirmed as a marker of chicken intake, and its measurement in fasting urine samples could be used to determine chicken intake in a free-living population. This trial was registered at clinicaltrials.gov as NCT01684917.

Growth Performance and Right Ventricular Hypertrophy Responses of Broiler Chickens to Guanidinoacetic Acid Supplementation under Hypobaric Hypoxia

Guanidinoacetic acid (GAA) has been shown to spare arginine (ARG) requirements in chickens. ARG plays a critical role in enhancing growth and preventing right ventricular hypertrophy (RVH) in broiler chickens subjected to hypobaric hypoxia. However, ARG is not available as a feed grade supplement in the market. Therefore, we evaluated the effects of commercially available GAA supplement as an alternative on growth performance and RVH in broilers raised at high altitude (2100 m). Five graded levels of GAA ranging from 0 (control) to 2 g/kg were provided in isoenergetic and isonitrogenous diets to broilers (Ross 308) from day 1 to 42, post-hatch. Results indicated that responses to GAA were nonlinear and attained plateau values within the studied range of GAA supply. While weight gain and feed intake were unaffected by GAA supply, feed conversion ratio was improved by GAA supplementation up to 1.5 g/kg. Similar trends were observed for the proportions in the liver and heart, as well as hematocrit. GAA supplementation at 1 and 1.5 g/kg resulted in reduced abdominal fat deposition as well as a decline in right-tototal ventricular weight ratio (RV:TV, an index of RVH). A significant (P<0.05) increase in serum nitric oxide concentration was observed at 1 and 1.5 g/kg GAA supplementation. However, GAA supply led to lower serum malondialdehyde and uric acid levels than in the control. In conclusion, GAA supplementation up to 1.5 g/kg had the potential to improve growth performance and RVH response. Meanwhile, GAA supply beyond 1.5 g/kg could deteriorate these responses.

International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine

Creatine is one of the most popular nutritional ergogenic aids for athletes. Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. In addition to athletic and exercise improvement, research has shown that creatine supplementation may enhance post-exercise recovery, injury prevention, thermoregulation, rehabilitation, and concussion and/or spinal cord neuroprotection. Additionally, a number of clinical applications of creatine supplementation have been studied involving neurodegenerative diseases (e.g., muscular dystrophy, Parkinson's, Huntington's disease), diabetes, osteoarthritis, fibromyalgia, aging, brain and heart ischemia, adolescent depression, and pregnancy. These studies provide a large body of evidence that creatine can not only improve exercise performance, but can play a role in preventing and/or reducing the severity of injury, enhancing rehabilitation from injuries, and helping athletes tolerate heavy training loads. Additionally, researchers have identified a number of potentially beneficial clinical uses of creatine supplementation. These studies show that short and long-term supplementation (up to 30 g/day for 5 years) is safe and well-tolerated in healthy individuals and in a number of patient populations ranging from infants to the elderly. Moreover, significant health benefits may be provided by ensuring habitual low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan. The purpose of this review is to provide an update to the current literature regarding the role and safety of creatine supplementation in exercise, sport, and medicine and to update the position stand of International Society of Sports Nutrition (ISSN).

The chemistry and biology of guanidine natural products

The chemistry and biology of natural guanidines isolated from microbial culture media, from marine invertebrates, as well as from terrestrial plants and animals, are reviewed.

Potential harmful effects of dietary supplements in sports medicine

PURPOSE OF REVIEW

The purpose of this article is to collect the most recent data regarding the safety of well-known or emerging dietary supplements used by athletes.

RECENT FINDINGS

From January 2014 to April 2016, about 30 articles have been published in the field. New data show that 90% of sports supplements contain trace of estrogenic endocrine disruptors, with 25% of them having a higher estrogenic activity than acceptable. About 50% of the supplements are contaminated by melamine, a source of nonprotein nitrogen. Additional data accumulate toward the safety of nitrate ingestion. In the last 2 years, the safety of emerging supplements such as higenamine, potentially interesting to lose weight, creatine nitrate and guanidinoacetic acid has been evaluated but still needs further investigation.

SUMMARY

The consumption of over-the-counter supplements is very popular in athletes. Although most supplements may be considered as safe when taking at the recommended doses, athletes should be aware of the potential risks linked to the consumption of supplements. In addition to the risks linked to overdosage and cross-effects when combining different supplements at the same time, inadvertent or deliberate contamination with stimulants, estrogenic compounds, diuretics or anabolic agents may occur.

Dietary guanidinoacetic acid increases brain creatine levels in healthy men

OBJECTIVE

Guanidinoacetic acid (GAA) is an experimental dietary additive that might act as a creatine source in tissues with high-energy requirements. In this case study, we evaluated brain levels of creatine in white matter, gray matter, cerebellum, and thalamus during 8 wk oral GAA administration in five healthy men and monitored the prevalence and severity of side effects of the intervention.

METHODS

Volunteers were supplemented daily with 36 mg/kg body weight (BW) of GAA for the first 4 wk of the intervention; afterward GAA dosage was titrated ≤60 mg/kg BW of GAA daily. At baseline, 4, and 8 wk, the participants underwent brain magnetic resonance spectroscopy, clinical chemistry studies, and open-ended questionnaire for side-effect prevalence and severity.

RESULTS

Brain creatine levels increased in similar fashion in cerebellum, and white and gray matter after GAA supplementation, with an initial increase of 10.7% reported after 4 wk, and additional upsurge (7.7%) from the weeks 4 to 8 follow-up (P < 0.05). Thalamus creatine levels decreased after 4 wk for 6.5% (P = 0.02), and increased nonsignificantly after 8 wk for 8% (P = 0.09). GAA induced an increase in N-acetylaspartate levels at 8-wk follow-up in all brain areas evaluated (P < 0.05). No participants reported any neurologic adverse event (e.g., seizures, tingling, convulsions) during the intervention.

CONCLUSIONS

Supplemental GAA led to a region-dependent increase of the creatine pool in the human brain. This might be relevant for restoring cellular bioenergetics in disorders characterized by low brain creatine and functional enzymatic machinery for creatine synthesis, including neurodegenerative diseases, brain tumors, or cerebrovascular disease.