Advanced physiological roles of guanidinoacetic acid

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.

Association analysis of transcriptome and quasi-targeted metabolomics reveals the regulation mechanism underlying broiler muscle tissue development at different levels of dietary guanidinoacetic acid

The development and characteristics of muscle fibers in broilers are critical determinants that influence their growth performance, as well as serve as essential prerequisites for the production of high-quality chicken meat. Guanidinoacetic acid (GAA) is a crucial endogenous substance in animal creatine synthesis, and its utilization as a feed additive has been demonstrated the capabilities to enhance animal performance, optimize muscle yield, and augment carcass quality. The objective of this study was to investigate the regulation and molecular mechanism underlying muscle development in broilers at different levels of GAA via multiple omics analysis. The 90 Cobb broilers, aged 1 day, were randomly allocated into three treatments consisting of five replicates of six chickens each. The control group was provided with a basal diet, while the Normal GAA and High GAA groups received a basal diet supplemented with 1.2 g/kg and 3.6 g/kg of GAA, respectively. After a feeding period of 42 days, the pectoralis muscles were collected for histomorphological observation, transcriptome and metabolomic analysis. The results demonstrated that the addition of 1.2 g/kg GAA in the diet led to an augmentation in muscle fiber diameter and up-regulation of IGF1, IHH, ASB2, and ANKRD2 gene expression. However, a high dose of 3.6 g/kg GAA in the diet potentially reversed the beneficial effects on chicken breast development by excessively activating the TGF-β signaling pathway and reducing nucleotide metabolite content. These findings would provide a theoretical foundation for enhancing the performance and meat quality of broilers by incorporating GAA as a feed additive.

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.

Landscapes of gut bacterial and fecal metabolic signatures and their relationship in severe preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific disease leading to maternal and perinatal morbidity. Hypertension and inflammation are the main characteristics of preeclampsia. Many factors can lead to hypertension and inflammation, including gut microbiota which plays an important role in hypertension and inflammation in humans. However, alterations to the gut microbiome and fecal metabolome, and their relationships in severe preeclampsia are not well known. This study aims to identify biomarkers significantly associated with severe preeclampsia and provide a knowledge base for treatments regulating the gut microbiome.

METHODS

In this study, fecal samples were collected from individuals with severe preeclampsia and healthy controls for shotgun metagenomic sequencing to evaluate changes in gut microbiota composition. Quantitative polymerase chain reaction analysis was used to validate the reliability of our shotgun metagenomic sequencing results. Additionally, untargeted metabolomics analysis was performed to measure fecal metabolome concentrations.

RESULTS

We identified several Lactobacillaceae that were significantly enriched in the gut of healthy controls, including Limosilactobacillus fermentum, the key biomarker distinguishing severe preeclampsia from healthy controls. Limosilactobacillus fermentum was significantly associated with shifts in KEGG Orthology (KO) genes and KEGG pathways of the gut microbiome in severe preeclampsia, such as flagellar assembly. Untargeted fecal metabolome analysis found that severe preeclampsia had higher concentrations of Phenylpropanoate and Agmatine. Increased concentrations of Phenylpropanoate and Agmatine were associated with the abundance of Limosilactobacillus fermentum. Furthermore, all metabolites with higher abundances in healthy controls were enriched in the arginine and proline metabolism pathway.

CONCLUSION

Our research indicates that changes in metabolites, possibly due to the gut microbe Limosilactobacillus fermentum, can contribute to the development of severe preeclampsia. This study provides insights into the interaction between gut microbiome and fecal metabolites and offers a basis for improving severe preeclampsia by modulating the gut microbiome.

Effect of guanidinoacetic acid on performance, egg quality, yolk fatty acid composition, and nutrient digestibility of aged laying hens fed diets with varying substitution levels of corn with low-tannin sorghum

A study was conducted to evaluate the efficiency of guanidinoacetic acid (GAA) in diets containing varying levels of corn replacement with low-tannin sorghum (LTS) for laying hens in the later stage of production. In a 12-wk study, a total of 288 laying hens at 52 wk of age were divided into 6 treatment groups. Each treatment group had 8 replicates, each of which consisted of 6 hens. A 2 × 3 factorial design was used to investigate the impact of substituting corn with LTS at 3 levels (100% corn, 50% LTS, and 100% LTS) with 2 doses of GAA supplementation (0 and 0.6 g/kg). The results indicate that there were interaction effects (P < 0.05) between diet type and GAA supplementation on protein digestibility and AMEn, with the GAA supplement being more effective in the 100% LTS group. Replacing corn with LTS at both levels had no negative effects on performance and metabolic profile. In contrast, the 100% LTS diet increased monounsaturated fatty acids in the yolk (P < 0.05), but decreased the yolk color index, the ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids (SFA) in the yolk, ileal digestibility of energy, and AMEn when compared to the 100% corn diet (P < 0.05). Regardless of the diet, dietary supplementation with GAA resulted in increases (P < 0.05) in shell-breaking strength, the PUFA to SFA ratio in egg yolk, and concentrations of creatine and nitric oxide in serum. There was also a decrease (P < 0.05) in serum malondialdehyde concentration with GAA supplementation. In conclusion, the positive effects of GAA on protein digestibility and AMEn were found to be more pronounced when corn was completely replaced with LTS. However, the positive effects of GAA on egg-laying performance, eggshell quality, antioxidant status, and yolk fatty acid composition remained consistent regardless of the extent to which corn was substituted with LTS.

Biomarkers of fatigue in oncology: A systematic review

Cancer-related fatigue (CRF) is a distressing side effect of cancer and treatment, affecting both patients during active treatment and survivors, negatively impacting quality of life. While its exact cause remains uncertain, various mechanisms such as immune dysfunction, HPA-axis dysfunction, and treatment toxicity are proposed. Inflammatory biomarkers of CRF have been explored in previous research, but non-inflammatory markers have not been comprehensively studied. This systematic review analysed 33 studies to identify non-inflammatory peripheral blood biomarkers associated with CRF. Promising markers included Hb, blood coagulation factors, BDNF, tryptophan, GAA, mtDNA, platinum, CA125, and cystatin-C. Inconsistent findings were observed for other markers like VEGF, leptin, and stress hormones. Most studies focused on adults. Research in pediatrics is limited. This review showed partial evidence for the inflammaging hypothesis (neurotoxicity due to neuro-inflammation) laying at the basis of CRF. Further research, especially in pediatrics, is needed to confirm this hypothesis and guide future biomarker studies.

Inclusion of guanidinoacetic acid in a low metabolizable energy diet improves broilers growth performance by elevating energy utilization efficiency through modulation serum metabolite profile

This study was aimed to explore the elevating energy utilization efficiency mechanism for the potentially ameliorative effect of guanidinoacetic acid (GAA) addition on growth performance of broilers fed a low metabolizable energy (LME) diet. A total of 576 d old broilers were randomly allocated to one of the six treatments: a basal diet (normal ME, positive control, PC), or an LME diet (50 kcal/kg reduction in ME, negative control, NC) supplemented with 0.02%, 0.04%, 0.06%, and 0.08% GAA from 1 to 42 d of age, respectively. The GAA fortification in LME diet linearly or quadratically dropped (P < 0.05) the feed conversion ratio (FCR) from 22 to 42 and 1 to 42 d of age, abdominal fat rate on day 42, serum alanine aminotransferase (ALT) on day 21, and serum creatinine (CREAN) on days 21 and 42, elevated (P < 0.05) breast muscle rate and leg muscle rate on day 42, serum creatine kinase (CK) on days 21 and 42, as well as alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) on day 21. The dietary optimal GAA levels were 0.03%-0.08% based on the best-fitted quadratic models (P < 0.03) of the above parameters. Thus, the PC, LME, and 0.04% GAA-LME groups were selected for further analysis. Serum essential amino acids (EAA) tryptophan, histidine and arginine, non-essential amino acids (NEEA) serine, glutamine and aspartic acid were significantly decreased (P < 0.05), compared to PC diet by LME or 0.04% GAA-LME diet. 0.04% GAA-LME group reversed (P < 0.05) the reduction of arginine, 3-methyhistidine, and 1-methylhistidine by LME diet. Besides, six birds at 28 d of age from LME and 0.04% GAA-LME groups were selected for energy utilization observation in calorimetry chambers. The results demonstrated that 0.04% GAA-LME group significantly improved (P < 0.05) the ME intake (MEI) and net energy (NE) compared to the LME diet. Overall, these findings suggest that 0.04% GAA is the ideal dose of broilers fed the LME diet, which can significantly improve the growth performance and carcass characteristics by modulation of creatine metabolism through elevating serum CK activity and arginine concentration.

Epigenetic reprogramming-induced guanidinoacetic acid synthesis promotes pancreatic cancer metastasis and transcription-activating histone modifications

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) tends to undergo distant metastasis, especially liver metastasis, leading to a poor prognosis. Metabolic remodelling and epigenetic reprogramming are two important hallmarks of malignant tumours and participate in regulating PDAC tumorigenesis and metastasis. However, the interaction between these two processes during PDAC metastasis has not been fully elucidated.

METHODS

We performed metabolomics analysis to identify the critical metabolites associated with PDAC liver metastasis and focused on guanidinoacetic acid (GAA). Intracellular GAA content was significantly increased in liver metastatic PDAC cells compared to primary cancer cells in mouse xenograft tumour models. The effects of GAA supplementation and glycine amidinotransferase (GATM) knockdown on PDAC metastasis were assessed by analysing cell migration, filopodia formation, epithelial-mesenchymal transition (EMT), and in vivo metastasis in different cell and animal models. Next, ChIP‒qPCR, 3C‒qPCR, and CRISPRi/dCas9-KRAB experiments were used to validate the "epigenome-metabolome" mechanism. Finally, the results of in vitro approaches, including RNA-seq, CUT&RUN, RT‒qPCR, and western blot analyses, as well as luciferase reporter gene assay and transwell assay, revealed the GAA-c-Myc-HMGA axis and transcription-activating histone modifications reprogramming.

RESULTS

A high level of intracellular GAA was associated with PDAC liver metastasis. GAA could promote the migration, EMT, and liver metastasis of pancreatic cancer cells in vitro and in vivo. Next, we explored the role of GATM-mediated de novo GAA synthesis in pancreatic cancer metastasis. High expression of GATM was positively correlated with advanced N stage in PDAC. Knockdown of GATM significantly reduced the intracellular level of GAA, suppressed EMT, and inhibited PDAC liver metastasis, and these effects were attenuated by GAA supplementation. Mechanistically, we identified the active enhancers looped to the Gatm gene locus that promoted GATM expression and PDAC liver metastasis. Furthermore, we found that GAA promoted cell migration and EMT by regulating c-Myc-mediated high mobility group AT-hook protein expression. Moreover, GAA increased the H3K4me3 modification level by upregulating histone methyltransferases, which induced the transcription of metastasis-related genes, including Myc.

CONCLUSIONS

These findings revealed the critical role of the epigenome-metabolome interaction in regulating PDAC liver metastasis and suggested potential therapeutic strategies targeting GAA metabolism and epigenetic regulatory mechanisms.

Effects of feeding guanidinoacetic acid on oxidative status and creatine metabolism in broilers subjected to chronic cyclic heat stress in the finisher phase

Dietary guanidinoacetic acid (GAA) has been shown to affect creatine (Cr) metabolic pathways resulting in increased cellular Cr and hitherto broiler performances. Yet, the impact of dietary GAA on improving markers of oxidative status remains equivocal. A model of chronic cyclic heat stress, known to inflict oxidative stress, was employed to test the hypothesis that GAA could modify bird's oxidative status. A total of 720-day-old male Ross 308 broilers were allocated to 3 treatments: 0, 0.6 or 1.2 g/kg GAA was added to corn-SBM diets and fed for 39 d, with 12 replicates (20 birds each) per treatment. The chronic cyclic heat stress model (34°C with 50-60% RH for 7 h daily) was applied in the finisher phase (d 25-39). Samples from 1 bird per pen were taken on d 26 (acute heat stress) and d 39 (chronic heat stress). GAA and Cr in plasma were linearly increased by feeding GAA on either sampling day, illustrating efficient absorption and methylation, respectively. Energy metabolism in breast and heart muscle was greatly supported as visible by increased Cr and phosphocreatine: ATP, thus providing higher capacity for rapid ATP generation in cells. Glycogen stores in breast muscle were linearly elevated by incremental GAA, on d 26 only. More Cr seems to be directed to heart muscle as opposed to skeletal muscle during chronic heat stress as tissue Cr was higher in heart but lower in breast muscle on d 39 as opposed to d 26. The lipid peroxidation marker malondialdehyde, and the antioxidant enzymes superoxide dismutase and glutathione peroxidase showed no alterations by dietary GAA in plasma. Opposite to that, superoxide dismutase activity in breast muscle was linearly lowered when feeding GAA (trend on d 26, effect on d 39). Significant correlations between the assessed parameters and GAA inclusion were identified on d 26 and d 39 using principal component analysis. To conclude, beneficial performance in heat-stressed broilers by GAA is associated with enhanced muscle energy metabolism which indirectly may also support tolerance against oxidative stress.

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 exhibited greater growth performance in younger (13–30 kg) than in older (30–50 kg) lambs under high-concentrate feedlotting pattern

Guanidine acetic acid (GAA) is increasingly considered as a nutritional growth promoter in monogastric animals. Whether or not such response would exist in rapid-growing lambs is unclear yet. The objective of this study was to investigate whether dietary supplementation with uncoated GAA (UGAA) and coated GAA (CGAA) could alter growth performance, nutrient digestion, serum metabolites, and antioxidant capacity in lambs. Seventy-two small-tailed Han lambs initially weighed 12 ± 1.6 kg were randomly allocated into six groups in a 2 × 3 factorial experimental design including two forage-type rations [Oaten hay (OH) vs. its combination with wheat silage (OHWS)] and three GAA treatment per ration: no GAA, 1 g UGAA, and 1 g CGAA per kg dry matter. The whole experiment was completed in two consecutive growing stages (stage 1, 13–30 kg; stage 2, 30–50 kg). Under high-concentrate feeding pattern (Stage 1, 25: 75; Stage 2, 20: 80), UGAA or CGAA supplementation in young lambs presented greater dry matter intake (DMI) in stage 1 and average daily gain (ADG) in the whole experimental period; lambs in OH group had higher ADG and DMI than that in OHWS group in stage 1 and whole experimental period, but this phenomenon was not observed in stage 2. Both UCGA and CGAA addition increased dietary DM, organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestion in both stages. In blood metabolism, UCGA and CGAA addition resulted in a greater total protein (TP) and insulin-like growth factor 1(IGF-1) levels, as well as antioxidant capacity; at the same time, UCGA and CGAA addition increased GAA metabolism-creatine kinase and decreased guanidinoacetate N-methyltransferase (GAMT) and L-Arginine glycine amidine transferase catalyzes (AGAT) activity. In a brief, the results obtained in the present study suggested that GAA (UGAA and CGAA; 1 g/kg DM) could be applied to improve growth performance in younger (13–30 kg) instead of older (30–50 kg) lambs in high-concentrate feedlotting practice.

Skeletal muscle mass, meat quality and antioxidant status in growing lambs supplemented with guanidinoacetic acid

Guanidinoacetic acid (GAA) exists naturally as a precursor of creatine, which possesses several biological functions. In the present study, the effects of dietary GAA supplementation on skeletal muscle mass and meat quality of lambs were investigated. The GAA supplementation increased final body weight, promoted muscle mass and changed the distribution of myofiber size. Meanwhile, elevated ultimate pH and water holding capacity (WHC) of resulting meat were observed in GAA fed lambs. Moreover, the total antioxidative capacity was elevated. Dietary GAA accelerated myofibril protein synthesis through regulation with IGF-1/Akt/mTOR signaling pathway and minimized protein breakdown via regulating abundances of myostatin and phosphorylated FoxO1. In vitro, GAA treatment inhibited sheep primary myoblasts proliferation, and enhanced its myogenic potential. Collectively, these results suggested that GAA might be a feed additive for use by the lamb meat industry as it has potential to improve growth performance, antioxidant status and WHC of resulting meat.

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.

Cataloguing guanidinoacetic acid content in various foods

Guanidinoacetic acid (GAA) is a natural amino acid derivative involved in several metabolic pathways across the human body, including creatine biosynthesis, arginine utilization, and neuromodulation. Apart from GAA synthesized internally from glycine and arginine, a total daily exposure to GAA also involves exogenous dietary sources. However, a majority of food databases provide no comprehensive data about the amount of GAA available from various foods. In this report, we summarize information for GAA levels in different food groups, as extracted from the available scientific literature. The content of GAA appears to vary across different foods, with meat-based products contain the highest relative amount of GAA (~50 mg per kg), followed by a dairy group (~0.3 mg per kg), and plant-based foods (~1 μg per kg), with the latter considered to be almost negligible. Although no data are currently available about its requirements in humans, cataloguing GAA amount in various foods could help in more accurate quantification of GAA provision via regular diet in the future.

Metabonomic identification of serum biomarkers related to heat stress tolerance of sheep

Heat stress is considered as a limiting factor for sheep production; it is necessary to screen for sheep breeds with heat tolerance. This study was to compare the serum metabolomes of Hu sheep and Dorper sheep and identify potential biomarkers related to heat stress. The results revealed that the respiratory rate, heart rate, and rectal temperature of Dorper sheep were significantly higher than those of Hu sheep. Compared to Dorper sheep, the serum activities of total antioxidant capacity and glutathione peroxidase in Hu sheep were significantly higher, while the concentration of malondialdehyde was lower. Metabolomics analysis identified 107 differential serum metabolites. The pathways enriched from the altered serum metabolites between the two breeds were mainly involved in protein metabolism, carbohydrate metabolism, and lipid metabolism. The levels of antioxidant- and energy-related metabolites were higher in the serum of Hu sheep than that of Dorper sheep; however, the levels of lipid catabolism- and inflammation-related were higher in the serum of Dorper sheep. The results indicate that Hu sheep had better heat stress resistance capability than Dorper sheep. Moreover, high levels of metabolites in the serum of Hu sheep are potential biomarkers for heat stress tolerance, including l-methionine, s-adenosylmethionine, and nicotinuric acid.

Effects of low eggshell temperatures during incubation, in ovo feeding of L-arginine, and post-hatch dietary guanidinoacetic acid on hatching traits, performance, and physiological responses of broilers reared at low ambient temperature

This study aimed to investigate the effect of eggshell temperature (ET) manipulations during incubation, in ovo feeding (IOF) of arginine, and post-hatch dietary supplementation with guanidinoacetic acid (GAA) on hatching traits and subsequent growth and physiological performance of hatched broiler chicks reared under subnormal temperature. In experiment 1, from d 8 of incubation onward, a total of 2,160 hatching eggs were randomly arranged in a 2 × 3 factorial design, in which the eggs were exposed to 2 ET (37.8°C or periodically low ET), and 3 IOF treatments (noninjected, diluent-injected, and 1% arginine solution-injected). In experiment 2, a total of 576 one-day-old male broiler chicks from 2 temperature conditions and 2 IOF treatment groups (noninjected and Arg-injected) were reared for 42 d with or without GAA supplementation in a 2 × 2 × 2 factorial design. Each treatment had 6 replicates with 12 birds each. A subnormal ambient temperature (17°C) was applied from 15 d onward to induce ascites. Results from experiment 1 showed a 2-way interaction between ET and IOF for embryonic mortality rate during 19 to 21 d of incubation and residual yolk weight at hatch (P < 0.05). A periodically low ET significantly increased yolk free body mass, first-grade chicks, and relative heart weight than an ET of 37.8°C. In the second experiment, overall average daily gain (ADG) was increased, but feed conversion ratio (FCR), ascites mortality, and serum thyroid hormones and corticosterone were reduced in the low ET group (P < 0.05). There were also IOF × GAA interactions for ADG and FCR (P < 0.05). IOF of arginine or dietary GAA increased serum nitric oxide concentration and jejunal villus height, but decreased ascites mortality (P < 0.05). In conclusion, a periodically low ET accompanied by IOF of arginine during incubation and posthatch dietary supplementation with GAA could be a useful strategy for improving the chick quality at hatch and subsequent improvements in post-hatch performance and ascites indices in cold-stressed broilers.

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.

Multiplatform metabolomic analysis of the R6/2 mouse model of Huntington's disease

Huntington's disease (HD) is a progressive, neurodegenerative disease characterized by motor, cognitive, and psychiatric symptoms. To investigate the metabolic alterations that occur in HD, here we examined plasma and whole-brain metabolomic profiles of the R6/2 mouse model of HD. Plasma and brain metabolomic analyses were conducted using capillary electrophoresis-mass spectrometry (CE-MS). In addition, liquid chromatography-mass spectrometry (LC-MS) was also applied to plasma metabolomic analyses, to cover the broad range of metabolites with various physical and chemical properties. Various metabolic alterations were identified in R6/2 mice. We report for the first time the perturbation of histidine metabolism in the brain of R6/2 mice, which was signaled by decreases in neuroprotective dipeptides and histamine metabolites, indicative of neurodegeneration and an altered histaminergic system. Other differential metabolites were related to arginine metabolism and cysteine and methionine metabolism, suggesting upregulation of the urea cycle, perturbation of energy homeostasis, and an increase in oxidative stress. In addition, remarkable changes in specific lipid classes are indicative of dysregulation of lipid metabolism. These findings provide a deeper insight into the metabolic alterations that occur in HD and provide a foundation for the future development of HD therapeutics.

The physiological role of guanidinoacetic acid and its relationship with arginine in broiler chickens

The role of guanidinoacetic acid (GAA) and its relationship with arginine was reviewed in order to define a replacement ratio between GAA and arginine for broiler diet formulation, the ratio being of how much arginine could be spared, or replaced by GAA. Guanidionoacetic acid, the precursor of creatine, can be synthesized de novo from the amino acids arginine and glycine, whereby 1 mol of arginine creates 1 mol of GAA; that is a weight:weight (w:w) ratio of 1.49:1 (arginine:GAA). Guanidinoacetic acid exerts a growth effect through its primary physiological fate to form creatine, and additionally spares dietary arginine from GAA synthesis; so that it contributes to protein accretion and other functions. Creatine is critical in energy metabolism as a carrier and reservoir of phosphate for adenosine triphosphate (ATP) formation. Arginine deficiency causes reduced growth and can lead to disrupted levels of blood and muscle energy metabolites (phosphocreatine and creatine). Supplementing GAA into the diet restores these metabolites. At severe arginine deficiency, GAA addition cannot fully compensate the arginine deficit, as measured by growth performance. As arginine becomes nearer to sufficiency, the effect of GAA becomes more pronounced. When using growth rate or FCR as an indicator in broilers, a ratio in the range of 0.77 to 1.3:1 (w:w arginine:GAA) was seen, with one study noting a ratio of 2:1 when using FCR as an indicator. Higher ratios of up to 2.7:1 are achieved when using muscle creatine and phosphocreatine measurements. A recommendation of 1:1 (w:w) is proposed, which takes a conservative approach. Large scale studies with practical diets would be helpful to confirm that a ratio of 1:1 (w:w) or higher may be used in the field for broilers.

Breast muscle and plasma metabolomics profile of broiler chickens exposed to chronic heat stress conditions

Understanding the variations of muscle and plasma metabolites in response to high environmental temperature can provide important information on the molecular mechanisms related to body energy homeostasis in heat-stressed broiler chickens. In this study, we investigated the effect of chronic heat stress conditions on the breast muscle (Pectoralis major) and plasma metabolomics profile of broiler chickens by means of an innovative, high-throughput analytical approach such as the proton nuclear magnetic resonance (¹H NMR) spectrometry. A total of 300 Ross 308 male chicks were split into two experimental groups and raised in either thermoneutral conditions for the entire rearing cycle (0-41 days) (TNT group; six replicates of 25 birds/each) or exposed to chronic heat stress conditions (30 °C for 24 h/day) from 35 to 41 days (CHS group; six replicates of 25 birds/each). At processing (41 days), plasma and breast muscle samples were obtained from 12 birds/experimental group and then subjected to ¹H NMR analysis. The reduction of BW and feed intake as well as the increase in rectal temperature and heterophil: lymphocyte ratio confirmed that our experimental model was able to stimulate a thermal stress response without significantly affecting mortality. The ¹H NMR analysis revealed that a total of 26 and 19 molecules, mostly related to energy and protein metabolism as well as antioxidant response, showed significantly different concentrations respectively in the breast muscle and plasma in response to the thermal challenge. In conclusion, the results obtained in this study indicated that chronic heat stress significantly modulates the breast muscle and plasma metabolome in fast-growing broiler chickens, allowing to delineate potential metabolic changes that can have important implications in terms of body energy homeostasis, growth performance and product quality.

Exploring blood alterations in chronic kidney disease and haemodialysis using metabolomics

Chronic kidney disease (CKD) is characterized by retention of uremic solutes. Compared to patients with non-dialysis dependent CKD, those requiring haemodialysis (HD) have increased morbidity and mortality. We wished to characterise metabolic patterns in CKD compared to HD patients using metabolomics. Prevalent non-HD CKD KDIGO stage 3b-4 and stage 5 HD outpatients were screened at a single tertiary hospital. Various liquid chromatography approaches hyphenated with mass spectrometry were used to identify 278 metabolites. Unsupervised and supervised data analyses were conducted to characterize metabolic patterns. 69 patients were included in the CKD group and 35 in the HD group. Unsupervised data analysis showed clear clustering of CKD, pre-dialysis (preHD) and post-dialysis (postHD) patients. Supervised data analysis revealed qualitative as well as quantitative differences in individual metabolites profiles between CKD, preHD and postHD states. An original metabolomics framework could discriminate between CKD stages and highlight HD effect based on 278 identified metabolites. Significant differences in metabolic patterns between CKD and HD patients were found overall as well as for specific metabolites. Those findings could explain clinical discrepancies between patients requiring HD and those with earlier stage of CKD.

Effect of post-ruminal guanidinoacetic acid supplementation on creatine synthesis and plasma homocysteine concentrations in cattle

Creatine stores high-energy phosphate bonds in muscle, which is critical for muscle activity. In animals, creatine is synthesized in the liver from guanidinoacetic acid (GAA) with methylation by S-adenosylmethionine. Because methyl groups are used for the conversion of GAA to creatine, methyl group deficiency may occur as a result of GAA supplementation. With this study, the metabolic responses of cattle to post-ruminal supplementation of GAA were evaluated with and without methionine (Met) supplementation as a source of methyl groups. Six ruminally cannulated Holstein heifers (520 kg) were used in a split-plot design with treatments arranged as a 2 × 5 factorial. The main plot treatments were 0 or 12 g/d of l-Met arranged in a completely randomized design; three heifers received each main plot treatment throughout the entire experiment. Subplot treatments were 0, 10, 20, 30, and 40 g/d of GAA, with GAA treatments provided in sequence from lowest to highest over five 6-d periods. Treatments were infused continuously to the abomasum. Heifers were limit-fed twice daily a diet consisting of (dry matter basis) 5.3 kg/d rolled corn, 3.6 kg/d alfalfa hay, and 50 g/d trace-mineralized salt. Plasma Met increased (P < 0.01) when Met was supplemented, but it was not affected by supplemental GAA. Supplementing GAA linearly increased plasma arginine (% of total amino acids) and plasma concentrations of GAA and creatinine (P < 0.001). Plasma creatine was increased at all levels of GAA except when 40 g/d of GAA was supplemented with no Met (GAA-quadratic × Met, P = 0.07). Plasma homocysteine was not affected by GAA supplementation when heifers received 12 g/d Met, but it was increased when 30 or 40 g/d of GAA was supplemented without Met (GAA-linear × Met, P = 0.003); increases were modest and did not suggest a dangerous hyperhomocysteinemia. Urinary concentrations of GAA and creatine were increased by all levels of GAA when 12 g/d Met was supplemented; increasing GAA supplementation up to 30 g/d without Met increased urinary GAA and creatine concentrations, but 40 g/d GAA did not affect urine concentrations of GAA and creatine when no Met was supplemented. Overall, post-ruminal GAA supplementation increased creatine supply to cattle. A methyl group deficiency, demonstrated by modest increases in plasma homocysteine, became apparent when 30 or 40 g/d of GAA was supplemented, but it was ameliorated by 12 g/d Met.

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.

Dietary guanidinoacetic acid supplementation improved carcass characteristics, meat quality and muscle fibre traits in growing-finishing gilts

This study was designed to evaluate the effects of guanidinoacetic acid (GAA) on growth performance, carcass characteristics, meat and muscle fibre traits of growing-finishing gilts. 300 female PIC pigs were randomly divided (30.10 ± 2.94 kg) into 2 treatments with 6 replicates of 25 each for a 100-day trial. Two dietary treatments were comprised of a control diet and a control diet fortified with 450 mg/kg GAA. Growth performance was evaluated for each phase. Carcass characteristics and meat quality were determined at last phase. Gilts had free access to feed and water during the experiment. The result indicated that GAA did not affect growth performance (p > 0.05). GAA not only increased longissimus dorsi (LM) muscle weight but also decreased its shear force, b*value and drip loss (p < 0.05). Mandibular fat index was decreased by GAA (p < 0.05). GAA upregulated myosin heavy chain (MyHC) I mRNA expression with lower myofibre cross-sectional area and fibre diameter in LM muscle (p < .05). In conclusion, GAA can improve carcass characteristics and meat quality by changing muscle fibre characteristics and reducing mandibular fat index in finishing gilts.

Effects of guanidinoacetic acid supplementation on growth performance, nutrient digestion, rumen fermentation and blood metabolites in Angus bulls

Guanidinoacetic acid (GAA) can improve the growth performance of bulls. This study investigated the influences of GAA addition on growth, nutrient digestion, ruminal fermentation and serum metabolites in bulls. Forty-eight Angus bulls were randomly allocated to experimental treatments, that is, control, low-GAA (LGAA), medium-GAA (MGAA) and high-GAA (HGAA), with GAA supplementation at 0, 0.3, 0.6 and 0.9 g/kg DM, respectively. Bulls were fed a basal diet containing 500 g/kg DM concentrate and 500 g/kg DM roughage. The experimental period was 104 days, with 14 days for adaptation and 90 days for data collection. Bulls in the MGAA and HGAA groups had higher DM intake and average daily gain than bulls in the LGAA and control groups. The feed conversion ratio was lowest in MGAA and highest in the control. Bulls receiving 0.9 g/kg DM GAA addition had higher digestibility of DM, organic matter, NDF and ADF than bulls in other groups. The digestibility of CP was higher for HGAA than for LGAA and control. The ruminal pH was lower for MGAA, and the total volatile fatty acid concentration was greater for MGAA and HGAA than for the control. The acetate proportion and acetate-to-propionate ratio were lower for MGAA than for LGAA and control. The propionate proportion was higher for MGAA than for control. Bulls receiving GAA addition showed decreased ruminal ammonia N. Bulls in MGAA and HGAA had higher cellobiase, pectinase and protease activities and Butyrivibrio fibrisolvens, Prevotella ruminicola and Ruminobacter amylophilus populations than bulls in LGAA and control. However, the total protozoan population was lower for MGAA and HGAA than for LGAA and control. The total bacterial and Ruminococcus flavefaciens populations increased with GAA addition. The blood level of creatine was higher for HGAA, and the activity of l-arginine glycine amidine transferase was lower for MGAA and HGAA, than for control. The blood activity of guanidine acetate N-methyltransferase and the level of folate decreased in the GAA addition groups. The results indicated that dietary addition of 0.6 or 0.9 g/kg DM GAA improved growth performance, nutrient digestion and ruminal fermentation in bulls.

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.

NMR assignment of the in vivo daphnia magna metabolome

Daphnia (freshwater fleas) are among the most widely used organisms in regulatory aquatic toxicology/ecology, while their recent listing as an NIH model organism is stimulating research for understanding human diseases and processes.

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.

Dietary Guanidinoacetic acid modulates testicular histology and expression of c-Kit and STRA8 genes in roosters

Decline in semen quality is considered as a major contributing factor in age-related subfertility of broiler breeder flocks. This study was aimed to investigate the effect of dietary supplementation of Guanidinoacetic acid (GAA), as an alternative energy source along with antioxidant potential, on testicular histology and relative gene expression of some spermatogonial markers (c-Kit and STRA8) in aged roosters. Sixteen 24-week-old male broiler breeders were randomly allocated into four groups and fed a basal diet supplemented with increasing levels of GAA including 0 (GAA-0), 600 (GAA-600), 1200 (GAA-1200) or 1800 (GAA-1800) mg/kg diet/day for 26 successive weeks. At the end of the experiment, all the birds were killed and two ipsilateral testicle samples were taken to either quantify relative gene expression or do histology. Except for seminiferous tubules' diameter, testicular weight, and the number of blood vessels, dietary supplementation of GGA improved the epithelium thickness of seminiferous tubules, the number of spermatogonia and Leydig cells and the relative gene expression of c-Kit and STRA8 (P < 0.01). Increasing levels of GAA cubically affected (P < 0.01) the diameter of seminiferous tubules and their epithelium thickness as well as the number of spermatogonia. However, number of Leydig cells and relative expression of c-Kit were linearly, and relative expression of STRA8 was quadratically (P < 0.01) enhanced in response to graded levels of GAA supplementation. Taking all parameters into account, daily supplementation of 1300-1450 mg of GAA/kg diet was estimated as an optimum dosage maximizing the evaluated traits.

Guanidinoacetic acid supplementation in broiler chickens fed on corn-soybean diets affects performance in the finisher period and energy metabolites in breast muscle independent of diet nutrient density

(1) Guanidinoacetic acid (GAA) is the single immediate endogenous precursor of creatine (Cr). It was hypothesised that dietary GAA would have different effects on performance and energy metabolites in breast muscle depending on the nutrient density (ND) of corn-soybean-based diets. (2) A total of 540 one-day-old male Ross 308 broilers were allocated to 9 dietary treatments with 6 replicates (10 birds each) in a 3 × 3 factorial arrangement with three levels of ND (low, 2800; medium, 2950 and high, 3100 kcal metabolizable energy (ME)/kg; and with the other nutrients being constant relative to ME) and supplemented with three levels of GAA (0, 0.6 and 1.2 g/kg) in a 42-d feeding trial. (3) In the starter and grower periods, increasing levels of ND improved body weight (BW), average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR), with the exception of ADFI in the starter period. GAA supplementation did not affect performance characteristics. All performance indicators responded markedly to increasing ND in the finisher period, whereas the highest GAA level reduced ADFI compared to the unsupplemented control (156 vs. 162 g/d) and concomitantly FCR (1.81 vs. 1.93). No interactive effects were noted for any performance trait. The high ND diet resulted in more breast meat yield on d42, associated with higher fat content and darker colour compared to the other ND levels. The GAA supplementation did not affect carcass and breast traits. At the end of the experiment, Cr was elevated when feeding GAA at 1.2 g/kg (5455 vs. 4338 mg/kg fresh muscle). (4) To conclude, ND had a substantial effect on performance and carcass traits, whereas any effect of GAA was limited to FCR in the finisher period and independent of diet ND level.

Effects of guanidinoacetic acid on growth performance, creatine and energy metabolism, and carcass characteristics in growing-finishing pigs

The aim of this study was to investigate the effects of dietary supplementation with guanidinoacetic acid (GAA) on the growth performance, creatine and energy metabolism, and carcass characteristics in growing-finishing pigs. In Exp. 1, Duroc × Landrace × Yorkshire pigs (n = 180, 33.61 ± 3.91 kg average BW) were blocked by weight and sex, and allotted to 5 treatments with 6 replicates (3 gilts and 3 barrows per replicate pen). Diets were corn-soybean meal-basal diets supplemented with 0, 300, 600, 900, and 1,200 mg/kg of GAA and fed to the pigs for 98 d. From days 1 to 98, G:F increased (linear, P < 0.05) with increasing addition of dietary GAA. Using a broken-line model, the optimum level of dietary GAA was 300 mg/kg during the overall experimental period (days 1 to 98) to maximize G:F. Hot carcass weight, carcass length, and lean percentage showed a tendency to increase (quadratic, 0.05 < P < 0.10) with increasing addition of dietary GAA. On day 98, serum GAA and liver creatine tended to increase (linear, P = 0.10, 0.07) as dietary GAA increased. In addition, serum ATP on day 98 increased linearly (linear, P < 0.01), and muscle ATP and adenosine monophosphate increased quadratically (quadratic, P = 0.05) with incremental GAA supplementation. In Exp. 2, Duroc × Landrace × Yorkshire pigs (n = 180, 53.19 ± 5.63 kg average BW) were blocked by weight and sex, and allotted to 5 treatments with 6 replicates (3 gilts and 3 barrows per replicate pen). Diets were corn-soybean meal-basal diets supplemented with 0, 150, 300, 600, and 1,200 mg/kg of GAA for 35 d. As dietary GAA increased, final BW, ADG, and G:F increased quadratically (quadratic, P < 0.01), and 300 mg/kg of GAA maximized ADG and final BW (P < 0.05).The results indicate that dietary GAA could increase the creatine and ATP load in the tissues of pigs and accordingly improve growth performance. Dietary supplementation with 300 mg/kg of GAA was suitable to maximize the growth performance of growing-finishing pigs.

Lactation-related metabolic mechanism investigated based on mammary gland metabolomics and 4 biofluids' metabolomics relationships in dairy cows

Background

Lactation is extremely important for dairy cows; however, the understanding of the underlying metabolic mechanisms is very limited. This study was conducted to investigate the inherent metabolic patterns during lactation using the overall biofluid metabolomics and the metabolic differences from non-lactation periods, as determined using partial tissue-metabolomics. We analyzed the metabolomic profiles of four biofluids (rumen fluid, serum, milk and urine) and their relationships in six mid-lactation Holstein cows and compared their mammary gland (MG) metabolomic profiles with those of six non-lactating cows by using gas chromatography-time of flight/mass spectrometry.

Results

In total, 33 metabolites were shared among the four biofluids, and 274 metabolites were identified in the MG tissues. The sub-clusters of the hierarchical clustering analysis revealed that the rumen fluid and serum metabolomics profiles were grouped together and highly correlated but were separate from those for milk. Urine had the most different profile compared to the other three biofluids. Creatine was identified as the most different metabolite among the four biofluids (VIP = 1.537). Five metabolic pathways, including gluconeogenesis, pyruvate metabolism, the tricarboxylic acid cycle (TCA cycle), glycerolipid metabolism, and aspartate metabolism, showed the most functional enrichment among the four biofluids (false discovery rate < 0.05, fold enrichment >2). Clear discriminations were observed in the MG metabolomics profiles between the lactating and non-lactating cows, with 54 metabolites having a significantly higher abundance (P < 0.05, VIP > 1) in the lactation group. Lactobionic acid, citric acid, orotic acid and oxamide were extracted by the S-plot as potential biomarkers of the metabolic difference between lactation and non-lactation. The TCA cycle, glyoxylate and dicarboxylate metabolism, glutamate metabolism and glycine metabolism were determined to be pathways that were significantly impacted (P < 0.01, impact value >0.1) in the lactation group. Among them, the TCA cycle was the most up-regulated pathway (P < 0.0001), with 7 of the 10 related metabolites increased in the MG tissues of the lactating cows.

Conclusions

The overall biofluid and MG tissue metabolic mechanisms in the lactating cows were interpreted in this study. Our findings are the first to provide an integrated insight and a better understanding of the metabolic mechanism of lactation, which is beneficial for developing regulated strategies to improve the metabolic status of lactating dairy cows.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4314-1) contains supplementary material, which is available to authorized users.

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.

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.

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.