|Molar mass||130.19 g·mol−1|
|Melting point||102 °C (216 °F; 375 K)|
|Boiling point||281 °C (538 °F; 554 K)|
|Flash point||95.8 °C (204.4 °F; 368.9 K)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Agmatine, also known as (4-aminobutyl)guanidine, is an aminoguanidine that was discovered in 1910 by Albrecht Kossel. It is a common natural compound synthesized by decarboxylation of the amino acid arginine, hence also known as decarboxylated arginine.
Agmatine has been shown to exert modulatory action at multiple molecular targets, notably: neurotransmitter systems, key ion channels, nitric oxide (NO) synthesis and polyamine metabolism, thus providing bases for further research into potential applications.
The term "agmatin" (German) was coined in 1910 by Albrecht Kossel who first identified the substance in herring sperm. Most probably the term stems from A- (for amino-) + g- (from guanidine) + -ma- (from ptomaine) + -in (German)/-ine (English) suffix with insertion of -t- apparently for euphony. Within a year following its discovery agmatine has been found to increase blood flow in rabbits, but the physiological relevance of these findings was questioned given the high concentrations (high µM range) required. In the 1920s, researchers in the diabetes clinic of Oskar Minkowski have shown that agmatine can exert mild hypoglycemic effects. The scarcity of research on agmatine during the better part of the 20th century (until the early 1990s) is outstanding. Only in 1994, the discovery of endogenous agmatine synthesis in mammals has revived research in the field.
Agmatine biosynthesis by arginine decarboxylation is well-positioned to compete with the principal arginine-dependent pathways, namely: nitrogen metabolism (urea cycle), and polyamine and nitric oxide (NO) synthesis (see illustration 'Agmatine Metabolic Pathways'). Agmatine degradation occurs mainly by hydrolysis, catalyzed by agmatinase into urea and putrescine, the diamine precursor of polyamine biosynthesis. An alternative pathway, mainly in peripheral tissues, is by diamine oxidase-catalyzed oxidation into agmatine-aldehyde, which is in turn converted by aldehyde dehydrogenase into guanidinobutyrate and secreted by the kidneys.
Mechanisms of action
Agmatine was found to exert modulatory actions directly and/or indirectly at multiple key molecular targets underlying cellular control mechanisms of cardinal importance in health and disease. It is considered capable of exerting its modulatory actions simultaneously at multiple targets. The following outline indicates the categories of control mechanisms and identifies their molecular targets:
- Neurotransmitter receptors and receptor ionophores. Nicotinic, imidazoline I1 and I2, α2- adrenergic, glutamate NMDAr, and serotonin 5-HT2A and 5HT-3 receptors.
- Ion channels. Including: ATP-sensitive K+ channels, voltage-gated Ca2+ channels, and acid-sensing ion channels (ASICs).
- Membrane transporters. Agmatine specific-selective uptake sites, organic cation transporters (mostly OCT2 subtype), extraneuronal monoamine transporters (ENT), polyamine transporters, and mitochondrial agmatine specific-selective transport system.
- Nitric oxide (NO) synthesis modulation. Differential inhibition by agmatine of all isoforms of NO synthase (NOS) is reported.
- Polyamine metabolism. Agmatine is a precursor for polyamine synthesis, competitive inhibitor of polyamine transport, inducer of spermidine/spermine acetyltransferase (SSAT), and inducer of antizyme.
- Protein ADP-ribosylation. Inhibition of protein arginine ADP-ribosylation.
- Matrix metalloproteases (MMPs). Indirect down-regulation of the enzymes MMP 2 and 9.
- Advanced glycation end product (AGE) formation. Direct blockade of AGEs formation.
- NADPH oxidase. Activation of the enzyme leading to H2O2 production.
Agmatine sulfate injection can increase food intake with carbohydrate preference in satiated, but not in hungry rats and this effect may be mediated by neuropeptide. However, supplementation in rat drinking water results in reductions in water intake and body weight gain. Also force feeding with agmatine leads to a reduction in body weight gain during rat development.
Agmatine is present in small amounts in plant-, animal-, and fish-derived foodstuff and Gut microbial production is an added source for agmatine. Oral agmatine is absorbed from the gastrointestinal tract and readily distributed throughout the body. Rapid elimination of ingested (un-metabolized) agmatine by the kidneys has indicated a blood half life of about 2 hours.
Agmatine sulfate supplements have been marketed for several years now to the bodybuilding channel, touting muscle-building qualities, although using completely unsubstantiated claims.
A number of potential medical uses for agmatine have been suggested.
Agmatine produces mild reductions in heart rate and blood pressure, apparently by activating both central and peripheral control systems via modulation of several of its molecular targets including: imidazoline receptors subtypes, norepinephrine release and NO production.
Agmatine hypoglycemic effects are the result of simultaneous modulation of several molecular mechanisms involved in blood glucose regulation.
Agmatine has been shown to enhance glomerular filtration rate (GFR) and to exert nephroprotective effects.
Agmatine has been discussed as a putative neurotransmitter/neuromodulator. It is synthesized in the brain, stored in synaptic vesicles, accumulated by uptake, released by membrane depolarization, and inactivated by agmatinase. Agmatine binds to α2-adrenergic receptor and imidazoline receptor binding sites, and blocks NMDA receptors and other cation ligand-gated channels. Short only of identifying specific ("own") post-synaptic receptors, agmatine in fact, fulfills Henry Dale's criteria for a neurotransmitter and is hence, considered a neuromodulator and co-transmitter. But identification of agmatinergic neuronal systems, if exist, still awaits future research.
Systemic agmatine can potentiate opioid analgesia and prevent tolerance to chronic morphine in laboratory rodents. Since then, cumulative evidence amply shows that agmatine inhibits opioid dependence and relapse in several animal species.
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