Hyperhomocysteinemia Induced by Guanidinoacetic Acid Is Effectively Suppressed by Choline and Betaine in Rats

Hyperhomocysteinemia: Metabolic Role and Animal Studies with a Focus on Cognitive Performance and Decline-A Review

Disturbances in the one-carbon metabolism are often indicated by altered levels of the endogenous amino acid homocysteine (HCys), which is additionally discussed to causally contribute to diverse pathologies. In the first part of the present review, we profoundly and critically discuss the metabolic role and pathomechanisms of HCys, as well as its potential impact on different human disorders. The use of adequate animal models can aid in unravelling the complex pathological processes underlying the role of hyperhomocysteinemia (HHCys). Therefore, in the second part, we systematically searched PubMed/Medline for animal studies regarding HHCys and focused on the potential impact on cognitive performance and decline. The majority of reviewed studies reported a significant effect of HHCys on the investigated behavioral outcomes. Despite of persistent controversial discussions about equivocal findings, especially in clinical studies, the present evaluation of preclinical evidence indicates a causal link between HHCys and cognition-related- especially dementia-like disorders, and points out the further urge for large-scale, well-designed clinical studies in order to elucidate the normalization of HCys levels as a potential preventative or therapeutic approach in human pathologies.

Effects of guanidinoacetic acid supplementation on nitrogen retention and methionine flux in cattle

Creatine stores high-energy phosphate bonds in muscle and is synthesized in the liver through methylation of guanidinoacetic acid (GAA). Supplementation of GAA may therefore increase methyl group requirements, and this may affect methyl group utilization. Our experiment evaluated the metabolic responses of growing cattle to postruminal supplementation of GAA, in a model where methionine (Met) was deficient, with and without Met supplementation. Seven ruminally cannulated Holstein steers (161 kg initial body weight [BW]) were limit-fed a soybean hull-based diet (2.7 kg/d dry matter) and received continuous abomasal infusions of an essential amino acid (AA) mixture devoid of Met to ensure that no AA besides Met limited animal performance. To provide energy without increasing the microbial protein supply, all steers received ruminal infusions of 200 g/d acetic acid, 200 g/d propionic acid, and 50 g/d butyric acid, as well as abomasal infusions of 300 g/d glucose. Treatments, provided abomasally, were arranged as a 2 × 3 factorial in a split-plot design, and included 0 or 6 g/d of l-Met and 0, 7.5, and 15 g/d of GAA. The experiment included six 10-d periods. Whole body Met flux was measured using continuous jugular infusion of 1-13C-l-Met and methyl-2H3-l-Met. Nitrogen retention was elevated by Met supplementation (P < 0.01). Supplementation with GAA tended to increase N retention when it was supplemented along with Met, but not when it was supplemented without Met. Supplementing GAA linearly increased plasma concentrations of GAA and creatine (P < 0.001), but treatments did not affect urinary excretion of GAA, creatine, or creatinine. Supplementation with Met decreased plasma homocysteine (P < 0.01). Supplementation of GAA tended (P = 0.10) to increase plasma homocysteine when no Met was supplemented, but not when 6 g/d Met was provided. Protein synthesis and protein degradation were both increased by GAA supplementation when no Met was supplemented, but decreased by GAA supplementation when 6 g/d Met were provided. Loss of Met through transsulfuration was increased by Met supplementation, whereas synthesis of Met from remethylation of homocysteine was decreased by Met supplementation. No differences in transmethylation, transsulfuration, or remethylation reactions were observed in response to GAA supplementation. The administration of GAA, when methyl groups are not limiting, has the potential to improve lean tissue deposition and cattle growth.

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.

Hyperhomocysteinemia Induced by Methionine Excess Is Effectively Suppressed by Betaine in Geese

The objective of our study was to investigate the effects of excess Methionine (Met) on the growth performance, serum homocysteine levels, apoptotic rates, and Bax and Bcl-2 protein levels in geese and to study the role of Bet (betaine) in relieving excess Met-induced hyperhomocysteinemia (HHcy). In this study, 150 healthy male 14-day-old Yangzhou geese of similar body weight were randomly distributed into three groups with five replicates per treatment and 10 geese per replicate: the control group (fed a control diet), the Met toxicity group (fed the control diet +1% Met), and the Bet detoxification group (fed the control diet +1% Met +0.2% Bet). At 28, 49, and 70 d of age, the geese in the Met toxicity group had significantly lower body weights than those in the control group (p < 0.05). The serum homocysteine levels in geese at 70 d of age in the detoxification group were significantly lower than those in the Met toxicity group (p < 0.05). Compared with the control, Met significantly increased cardiomyocyte apoptosis rates, while Bet reduced them. In conclusion, our results suggest that excess methionine reduces body weight induced by myocardial apoptosis, and Bet can be used to effectively lower plasma homocysteine levels.

Homocysteine and Hyperhomocysteinaemia

Homocysteine (Hcy) is a thiol group containing the amino acid, which naturally occurs in all humans. Hcy is degraded in the body through two metabolic pathways, while a minor part is excreted through kidneys. The chemical reactions that are necessary for degradation of Hcy require the presence of folic acid, vitamins B6 and B12. Consequently, the level of the total Hcy in the serum is influenced by the presence or absence of these vitamins. An elevated level of the Hcy, hyperhomocysteinemia (HHcy) and homocystinuria is connected with occlusive artery disease, especially in the brain, the heart, and the kidney, in addition to venous thrombosis, chronic renal failure, megaloblastic anemia, osteoporosis, depression, Alzheimer's disease, pregnancy problems, and others. Elevated Hcy levels are connected with various pathologies both in adult and child population. Causes of HHcy include genetic mutations and enzyme deficiencies in 5, 10-methylenetetrahydrofolate reductase (MTHFR) methionine synthase (MS), and cystathionine β-synthase (CβS). HHcy can be caused by deficiencies in the folate, vitamin B12 and to a lesser extent, deficiency in B6 vitamin what influences methionine metabolism. Additionally, HHcy can be caused by the rich diet and renal impairment. This review presents literature data from recent research related to Hcy metabolism and the etiology of the Hcy blood level disorder. In addition, we also described various pathological mechanisms induced by hereditary disturbances or nutritional influences and their association with HHcy induced pathology in adults and children and treatment of these metabolic disorders.

Guanidinoacetic acid with creatine compared with creatine alone for tissue creatine content, hyperhomocysteinemia, and exercise performance: A randomized, double-blind superiority trial

PURPOSE

Co-administration of creatine and guanidinoacetic acid (GAA) has been recently put forward as an advanced dietary strategy to optimize tissue bioenergetics. We hypothesized that creatine-GAA mixture would result in a more powerful rise in brain and skeletal muscle creatine, as compared to creatine supplementation alone.

METHODS

A randomized, double-blinded, crossover superiority trial has been performed at the University of Novi Sad from December 2016 to November 2017. A total of 14 healthy young men were randomized to receive GAA-creatine mixture (1 grams of GAA and 3 grams of creatine per day) or equimolar creatine (4 grams per day) by oral administration for 4 weeks.

RESULTS

Creatine-GAA mixture was superior to creatine alone to increase mean creatine levels in skeletal muscle (16.9 ± 20.2 vs. 2.0 ± 6.0%; P = 0.02) and grey matter (5.8 ± 5.3% vs. 1.5 ± 3.2%; P = 0.02), also for bench press performance (6.0% vs. 5.1%; P < 0.01). Compared with creatine administration alone, combined GAA and creatine resulted in less weight gain (1.6 ± 0.2 kg vs. 0.7 ± 0.2 kg; P < 0.01). No inter-group differences were observed in terms of cardiorespiratory endurance, serum biomarkers, or adverse events.

CONCLUSIONS

Creatine-GAA mixture appeared to be superior to creatine alone for up-swinging tissue creatine content and upper body strength, and tended toward a lower risk of weight gain in healthy active men. The formulation might be considered as a novel energy-boosting alternative to creatine alone in weight-sensitive setups.

TRIAL REGISTRATION

ClinicalTrials.govNCT03350282.

Choline and betaine ameliorate liver lipid accumulation induced by vitamin B6 deficiency in rats

We investigated the efficacy of supplementing the diet with choline or betaine in ameliorating lipid accumulation induced by vitamin B₆ (B₆) deficiency in rat liver. Male Wistar rats were fed a control, B₆-deficient, choline-supplemented (2, 4, or 6 g choline bitartrate/kg diet) B₆-deficient diet or betaine-supplemented (1, 2, or 4 g betaine anhydrous/kg diet) B₆-deficient diet for 35 d; all diets contained 9 g L-methionine (Met)/kg diet. Choline or betaine supplementation attenuated liver lipid deposition and restored plasma lipid profiles to control levels. These treatments restored the disruptions in Met metabolism and the phosphatidylcholine (PC)/phosphatidylethanolamine (PE) ratio induced by B₆ deficiency in liver microsomes. These results suggest that choline and betaine ameliorated liver lipid accumulation induced by B₆ deficiency via recovery of Met metabolism and very low-density lipoprotein secretion by restoring the supply of PC derived from PE.

Guanidinoacetic acid versus creatine for improved brain and muscle creatine levels: a superiority pilot trial in healthy men

In this randomized, double-blind, crossover trial, we evaluated whether 4-week supplementation with guanidinoacetic acid (GAA) is superior to creatine in facilitating creatine levels in healthy men (n = 5). GAA (3.0 g/day) resulted in a more powerful rise (up to 16.2%) in tissue creatine levels in vastus medialis muscle, middle-cerebellar peduncle, and paracentral grey matter, as compared with creatine (P < 0.05). These results indicate that GAA as a preferred alternative to creatine for improved bioenergetics in energy-demanding tissues.

First evidence of accumulation in cyanobacteria of guanidinoacetate, a precursor of the toxin cylindrospermopsin

Guanidinoacetate (GAA) is one of the most extensively studied toxic guanidine compounds. Changes in GAA can affect the nervous system and induce hyperhomocysteinemia, representing a risk factor for cardiovascular diseases. In cyanobacteria, GAA is thought to be an intermediate in the synthesis of the toxin cylindrospermopsin (CYN), one of the most common known cyanotoxins that affects multiple organs and functions in animals and plants. In spite of the evidence supporting GAA toxicity and its role in CYN synthesis, no data have been reported on the accumulation of GAA in any cyanobacterium. We have analyzed and compared the content of GAA in cultures of diverse cyanobacteria types, both cylindrospermopsin producing (CYN(+)) and not producing (CYN(-)). The results obtained show that GAA accumulates in the majority of the strains tested, although the highest content was found in one of the CYN(+) strain, Aphanizomenon ovalisporum UAM-MAO. In this strain, both GAA and CYN can be located within and out the cells. In conclusion, GAA appears to be a general cyanobacterial metabolite that due to its proven toxic should be considered when studying and managing cyanobacteria toxicity.

Suppression effects of betaine-enriched spinach on hyperhomocysteinemia induced by guanidinoacetic acid and choline deficiency in rats

Betaine is an important natural component of rich food sources, especially spinach. Rats were fed diets with betaine or spinach powder at the same level of betaine for 10 days to investigate the dose-dependent effects of spinach powder supplementation on hyperhomocysteinemia induced by guanidinoacetic acid (GAA) addition and choline deprivation. The GAA-induced hyperhomocysteinemia in rats fed 25% casein diet (25C) was significantly suppressed by supplementation with betaine or spinach, and it was completely suppressed by taking 11.0% spinach supplementation. The choline deprivation-induced enhancement of plasma homocysteine concentration in rats fed 25% soybean protein diet (25S) was markedly suppressed by 3.82% spinach. Supplementation with betaine or spinach partially prevented the effects of GAA on hepatic concentrations of methionine metabolites. The decrease in activity of betaine-homocysteine S-methyltransferase (BHMT) and cystathionine β-synthase (CBS) in GAA-induced hyperhomocysteinemia was recovered by supplementation with betaine or spinach. Supplementation with betaine or spinach did not affect BHMT activity, whereas it partially restored CBS activity in choline-deprived 25S. The results indicated that betaine or spinach could completely suppress the hyperhomocysteinemia induced by choline deficiency resulting from stimulating the homocysteine removal by both remethylation and cystathionine formation.

Increased methylation demand exacerbates ethanol-induced liver injury

We previously reported that chronic ethanol intake lowers hepatocellular S-adenosylmethionine to S-adenosylhomocysteine ratio and significantly impairs many liver methylation reactions. One such reaction, catalyzed by guanidinoacetate methyltransferase (GAMT), is a major consumer of methyl groups and utilizes as much as 40% of the SAM-derived groups to convert guanidinoacetate (GAA) to creatine. The exposure to methyl-group consuming compounds has substantially increased over the past decade that puts additional stresses on the cellular methylation potential. The purpose of our study was to investigate whether increased ingestion of a methyl-group consumer (GAA) either alone or combined with ethanol intake, plays a role in the pathogenesis of liver injury. Adult male Wistar rats were pair-fed the Lieber DeCarli control or ethanol diet in the presence or absence of GAA for 2weeks. At the end of the feeding regimen, biochemical and histological analyses were conducted. We observed that 2 weeks of GAA- or ethanol-alone treatment increases hepatic triglyceride accumulation by 4.5 and 7-fold, respectively as compared with the pair-fed controls. However, supplementing GAA in the ethanol diet produced panlobular macro- and micro-vesicular steatosis, a marked decrease in the methylation potential and a 28-fold increased triglyceride accumulation. These GAA-supplemented ethanol diet-fed rats displayed inflammatory changes and significantly increased liver toxicity compared to the other groups. In conclusion, increased methylation demand superimposed on chronic ethanol consumption causes more pronounced liver injury. Thus, alcoholic patients should be cautioned for increased dietary intake of methyl-group consuming compounds even for a short period of time.

Dose-response effects of oral guanidinoacetic acid on serum creatine, homocysteine and B vitamins levels

PURPOSE

Guanidinoacetic acid (GAA) is an intermediate in the biosynthesis of creatine (Cr), yet its use in human nutrition is limited due to a lack of a clear understanding of its' dose-response effect. Thus, the purpose of this study was to investigate the effect of three different dosages of GAA (1.2, 2.4 and 4.8 g/day) administered for 6 weeks on serum and urinary variables related to GAA metabolism.

METHODS

Forty-eight healthy volunteers participated in the randomized, placebo-controlled, double-blind, repeated-measure study. At baseline, after 1, 2, 4 and 6 weeks, participants provided both fasting blood samples and 24-h urine.

RESULTS

GAA intervention significantly increased serum and urinary GAA, Cr and creatinine as compared to placebo (P < 0.05). Differences were found for serum GAA and Cr responses between the three GAA dosages, with high-dose GAA resulting in a greater increase (P < 0.05) in the plasma concentration of both variables as compared to other GAA dosages. In GAA groups, fasting plasma total homocysteine (T-Hcy) increased by 3.5 μmol/L on average at post-administration, yet no dose-response differences were found between trials. Serum B vitamins were not affected by either placebo or GAA intervention (P > 0.05).

CONCLUSION

Results indicate that low-to-high dosages of exogenous GAA can increase serum concentrations of Cr and T-Hcy while not depleting the B vitamins pool available for remethylation of homocysteine.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identification number NCT01133899.

Partitioning of [methyl-3H]methionine to methylated products and protein is altered during high methyl demand conditions in young Yucatan miniature pigs

Methionine is the main source of methyl groups that are partitioned to synthesize various methylated products including creatine, phosphatidylcholine (PC), and methylated DNA. Whether increased methylation of 1 product can divert methionine from protein synthesis or other methylation products was the aim of this experiment. We used an excess of guanidinoacetate (GAA) to synthesize creatine to create a higher demand for available methyl groups in normal-weight (NW) (n = 10) and intrauterine growth-restricted (IUGR) (n = 10) piglets. Anesthetized piglets (15-18 d old) were intraportally infused with either GAA or saline for 2 h. A bolus of l-[methyl-(3)H]methionine was intraportally infused at 1 h, and hepatic metabolites were analyzed for methyl-(3)H incorporation 1 h later. Overall, 50-75% of label was recovered in creatine and PC with negligible amounts in DNA. In both NW and IUGR piglets, excess GAA led to an ≈ 80-120% increase in methyl incorporation into creatine (P < 0.05) with a concomitant decrease by ≈ 75-85% in methyl incorporation into PC (P < 0.05) as well as a 40% decrease in methyl incorporation into protein (P < 0.05), suggesting methyl groups were limited for PC synthesis and that methionine was diverted from protein synthesis. Compared with NW piglets, IUGR piglets had lower methyl incorporation into PC (P < 0.05), but not DNA or protein, suggesting IUGR affects methyl metabolism and could potentially impact lipid metabolism. The partitioning of methionine is sensitive to methyl supply in neonates, which has implications in infant diet composition and growth.

Co-administration of methyl donors along with guanidinoacetic acid reduces the incidence of hyperhomocysteinaemia compared with guanidinoacetic acid administration alone

Guanidinoacetic acid (GAA) is the natural biosynthetic precursor of creatine, in a metabolic reaction that requires only a methyl group transfer. The use of GAA as a food additive for restoring creatine load in human tissues is rather unexplored and data on efficacy and safety are limited. In particular, an increase in serum homocysteine after GAA administration can be regarded as critical and should be prevented. The present study evaluated the effects of orally administered GAA with and without methyl group donors on serum and urine creatine concentrations, and the occurrence of adverse events during an intervention in healthy human subjects. A total of twenty male and female volunteers were randomised in a double-blind design to receive either GAA (2.4 g/d) or GAA with methyl donors (2.4 g/d of GAA and 1.6 g/d of betaine HCl, 5 μg/d of vitamin B12, 10 mg/d of vitamin B6 and 600 μg/d of folic acid) by oral administration for 8 weeks. Serum and urine creatine increased significantly from before to after administration in both groups (P< 0.001). The proportion of participants who reported minor adverse events was 33.3 % in the GAA group, and 10.0 % in the GAA with methyl donors group (P= 0.30). Hyperhomocysteinaemia was found in 55.6 % of participants supplemented with GAA, while no participant experienced hyperhomocysteinaemia in the group supplemented with GAA and methyl donors (P= 0.01). In summary, both interventions strongly influenced creatine metabolism, resulting in a significant increase in fasting serum creatine. The concomitant supplementation of methyl donors along with GAA largely precluded the elevation of serum homocysteine caused by GAA administration alone.

Creatine metabolism and safety profiles after six-week oral guanidinoacetic acid administration in healthy humans

OBJECTIVES

Guanidinoacetic acid (GAA) is a natural precursor of creatine, yet the potential use of GAA as a nutritional additive for restoring creatine availability in humans has been limited by unclear efficacy and safety after exogenous GAA administration. The present study evaluated the effects of orally administered GAA on serum and urinary GAA, creatine and creatinine concentration, and on the occurrence of adverse events in healthy humans.

METHODS AND RESULTS

Twenty-four healthy volunteers were randomized in a double-blind design to receive either GAA (2.4 grams daily) or placebo (PLA) by oral administration for 6 weeks.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, identification number NCT01133899. Serum creatine and creatinine increased significantly from before to after administration in GAA-supplemented participants (P < 0.05). The proportion of participants who reported minor side effects was 58.3% in the GAA group and 45.5% in the placebo group (P = 0.68). A few participants experienced serum creatine levels above 70 µmol/L.

CONCLUSION

Exogenous GAA is metabolized to creatine, resulting in a significant increase of fasting serum creatine after intervention. GAA had an acceptable side-effects profile with a low incidence of biochemical abnormalities.

Novel aldose reductase inhibitors: a patent survey (2006--present)

INTRODUCTION

Initially studied for its central role in the pathogenesis of chronic diabetic complications, aldose reductase (ALR2) gains more attention over the years as its implication in inflammatory diseases is being established, along with the therapeutic potential of its inhibitors.

AREAS COVERED

Reviewing the patents that were published since 2006, it is getting clear that the search for new chemical entities has subsided, giving rise to natural products and plant extracts with ALR2 inhibitory activity. Other aspects that were prominent were the search for proper forms of known inhibitors, in a way to improve their impaired physicochemical profile, as well as potential combination therapies with other compounds of pharmaceutical interest. On the spotlight were patents enhancing the therapeutic usage of aldose reductase inhibitors (ARIs) to various pathological conditions including cancer and inflammation-mediated diseases such as sepsis, asthma, and cancer.

EXPERT OPINION

Although new chemical entities are scarcely registered and patented after many years of inconclusive clinical trials, the involvement of ALR2 to inflammatory pathologies might renew the interest in the field of ARIs.

Methionine and serine synergistically suppress hyperhomocysteinemia induced by choline deficiency, but not by guanidinoacetic acid, in rats fed a low casein diet

The effects of dietary supplementation with 0.5% methionine, 2.5% serine, or both on hyperhomocysteinemia induced by deprivation of dietary choline or by dietary addition of 0.5% guanidinoacetic acid (GAA) were investigated in rats fed a 10% casein diet. Hyperhomocysteinemia induced by choline deprivation was not suppressed by methionine alone and was only partially suppressed by serine alone, whereas it was completely suppressed by a combination of methionine and serine, suggesting a synergistic effect of methionine and serine. Fatty liver was also completely prevented by the combination of methionine and serine. Compared with methionine alone, the combination of methionine and serine decreased hepatic S-adenosylhomocysteine and homocysteine concentrations and increased hepatic betaine and serine concentrations and betaine-homocysteine S-methyltransferase activity. GAA-induced hyperhomocysteinemia was partially suppressed by methionine alone, but no interacting effect of methionine and serine was detected. In contrast, GAA-induced fatty liver was completely prevented by the combination of methionine and serine. These results indicate that a combination of methionine and serine is effective in suppressing both hyperhomocysteinemia and fatty liver induced by choline deprivation, and that methionine alone is effective in suppressing GAA-induced hyperhomocysteinemia partially.