What Is Glycine? Other Names: Acide Aminoacétique, Athenon, Glycocoll

What is Glycine?

This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Glycine is a simple, non-essential amino acid that plays a crucial role in various physiological processes. Despite being classified as non-essential, meaning the body can synthesize it, glycine has been found to have significant protective and functional roles in different biological contexts. Other names include: Acide Aminoacétique, Acide Amino-Acétique, Aminoacetic Acid, Athenon, Free Base Glycine, G Salt, Glicina, Glycine de Base Libre, Glycocoll, Glycosthene, Iconyl, L-Glycine, Monazol.

Protective Effects in Ischemia-Reperfusion Injury

Glycine has demonstrated cytoprotective properties, particularly in the context of ischemia-reperfusion injury. In a study involving canine skeletal muscle, glycine was shown to preserve muscle function, reduce edema, and decrease muscle necrosis following ischemia and reperfusion. The study revealed that glycine-treated muscles had significantly lower weight gain (57% vs. 100%), higher maximal contractile force (712.5 g vs. 511 g), and reduced muscle necrosis (30% vs. 63%) compared to the control group treated with normal saline. Additionally, glycine helped maintain higher levels of ATP and phosphocreatine, essential for energy storage and muscle function1.

Role in Diabetic Cataract Prevention

Glycine also exhibits protective effects in the context of diabetic complications. In a study on streptozotocin-induced diabetic rats, glycine supplementation was found to inhibit aldose reductase activity, an enzyme implicated in the development of diabetic cataracts. Glycine-treated rats showed increased body weight gain, reduced blood glucose levels, and higher plasma insulin levels compared to diabetic control rats. Furthermore, glycine increased glutathione content and decreased mRNA and protein levels of aldose reductase, suggesting its potential in preventing diabetic cataracts2.

Conditional Indispensability in Pregnancy

While glycine is generally considered a dispensable amino acid, recent research suggests it becomes conditionally indispensable during the late stages of human pregnancy. A study examining glycine requirements in pregnant women found that lower glycine intakes in late gestation were associated with higher rates of phenylalanine oxidation and higher plasma 5-oxoproline levels, indicating reduced protein synthesis and glycine availability. The study concluded that glycine should be considered conditionally indispensable during late gestation, especially when protein intake is at the estimated average requirement3.

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Uses of Glycine

Medical Uses

Ischemia-Reperfusion Injury Protection

Glycine has been shown to preserve muscle function, decrease edema, and reduce muscle necrosis in skeletal muscle undergoing ischemia-reperfusion injury1. It also prevents apoptosis in mesenteric ischemia/reperfusion injury by downregulating pro-apoptotic signals8.

Intestinal Health

Glycine alleviates intestinal injury in weaned piglets by maintaining energy status, enhancing protein synthesis, and reducing inflammation through the regulation of AMPK, mTOR, TLR4, and NOD signaling pathways2.

Diabetic Cataract Prevention

Glycine inhibits aldose reductase activity, which is implicated in the development of diabetic cataracts, thereby reducing blood glucose levels and increasing plasma insulin in diabetic rats3.

Hyperuricemia Management

Combined with tryptophan, glycine reduces serum uric acid levels and increases urinary uric acid excretion, which can help manage conditions like gout4.

Cancer Prevention

Glycine has been found to prevent the development of liver tumors caused by the peroxisome proliferator WY-14,643, suggesting its potential as a chemopreventive agent7.

Nutritional Uses

Muscle Growth and Protein Synthesis

Glycine enhances muscle protein mass and growth in piglets by maintaining Akt-mTOR-FOXO1 signaling and suppressing inflammatory pathways6. It also increases tissue concentrations of creatine and the expression of creatine-synthetic enzymes, which is crucial for muscle development5.

Growth Performance in Livestock

Supplementing glycine in the diet of intrauterine growth-restricted (IUGR) pigs improves their growth performance, feed efficiency, and meat quality by increasing glycine concentrations in various tissues10.

Nutritional Support in Chronic Conditions

Glycine supplementation has been shown to increase fat-free mass in chronic hemodialysis patients, indicating its potential benefits in managing malnutrition in such conditions9.

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Adverse Effects of Glycine

Neurological Symptoms

Increased Risk of Neurological Symptoms: During transurethral resection of the prostate, absorption of glycine 1.5% was associated with a significantly higher risk of neurological symptoms such as nausea compared to mannitol 3%3.

Biochemical and Metabolic Changes

Biochemical Disturbances: In male albino rats, glycine combined with other food additives (fast green or sodium nitrate) led to various biochemical disturbances, including decreased body weight, total protein, albumin, and testosterone levels. Additionally, liver enzymes and kidney function tests showed increased levels, indicating potential liver and kidney stress1.

No Significant Changes in Healthy Rats: Chronic glycine supplementation in healthy Wistar rats did not significantly alter insulin, glucose, or triglyceride levels, nor did it cause any notable changes in liver or kidney histology5.

Central Nervous System Effects

No Significant CNS Effects in Stroke Patients: In patients with acute ischemic stroke, glycine treatment was generally safe, with only slight sedation observed in a small percentage of patients. No other significant central nervous system adverse effects were reported6.

No CNS or Hemodynamic Effects in Stroke Patients: GV150526, a glycine site antagonist, showed no significant central nervous system or hemodynamic adverse effects in stroke patients, though minor liver function abnormalities were noted at higher doses8.

Inflammatory and Metabolic Effects

Reduction in Inflammatory Mediators: In rats with obstructive jaundice, glycine reduced levels of inflammatory mediators such as TNF-alpha, ET-1, and NO in plasma and liver tissue, which may help alleviate pathological lesions7.

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How has Glycine Improved Patient Outcomes?

Periodontitis

Clinical and Inflammatory Outcomes: Glycine powder air-polishing (GPAP) as an adjunct to full-mouth scaling and root planing (SRP) showed similar clinical, inflammatory, and microbiological outcomes compared to SRP alone. Both treatments reduced C-reactive protein, IL-6, and TNF-α levels in serum1.

Ischemic Stroke

Neuroprotection: Glycine treatment (1.0-2.0 g/day) within 6 hours of acute ischemic stroke onset showed a tendency to decrease 30-day mortality and improve clinical outcomes on various stroke scales. It also normalized autoantibody titres to NMDA-binding proteins, reduced excitatory amino acids, and increased GABA concentrations in cerebrospinal fluid2.

Cystic Fibrosis

Inflammatory and Spirometric Status: Oral glycine (0.5 g/kg/day) improved symptom scores, stabilized or increased spirometric variables, and improved pulse oximetry in cystic fibrosis patients. It also tended to reduce TNF-α in serum and IL-6 and G-CSF in sputum3.

Psychosis Risk Syndrome

Symptom Reduction: Glycine treatment in patients with psychosis risk syndrome showed large effect sizes in reducing positive and total symptoms, and medium-to-large effect sizes for negative symptoms. It also suggested potential cognitive improvements4.

Liver Transplantation

Hepatoprotection: Glycine has been shown to prevent Kupffer cell activation and reperfusion injury post-liver transplantation. Ongoing trials aim to confirm its efficacy in reducing liver injury markers and improving graft and patient survival5.

Adjustment Disorders

Emotional Disturbances: Glycine significantly improved clinical global impression scores in patients with adjustment disorders, showing superiority over placebo in emotional disturbance parameters6.

Schizophrenia

Cognitive Impairment: Glycine transporter inhibitor BI 425809 improved cognitive function in schizophrenia patients, with the 10 mg and 25 mg doses showing the most significant benefits. Glycine also improved mismatch negativity (MMN) and negative symptoms in schizophrenia patients7 9.

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Glycine Mechanisms of Action

Neurotransmitter Function

Glycine acts as an inhibitory neurotransmitter in the central nervous system, particularly in the spinal cord. It binds to glycine receptors (GLY-A) and also serves as a co-agonist at NMDA (N-Methyl-D-Aspartate) receptors, which are involved in excitatory neurotransmission. This dual role helps modulate neurotransmission and maintain a balance between excitation and inhibition in the nervous system4 6 10.

Cytoprotective Effects

Glycine has been shown to have protective effects in various models of ischemia-reperfusion (I/R) injury. It helps preserve tissue function, reduce necrosis, and maintain energy stores by modulating apoptotic signals. Specifically, glycine downregulates pro-apoptotic molecules like bax and caspase-3, while upregulating anti-apoptotic molecules like bcl-2. This helps prevent cell death and tissue damage during I/R injury1 5.

Anti-inflammatory and Antioxidant Properties

Glycine can modulate inflammatory responses and oxidative stress. It has been shown to inhibit the activity of aldose reductase, an enzyme involved in the polyol pathway, which is implicated in diabetic complications like cataracts. Glycine also reduces oxidative stress markers and improves antioxidant levels, such as glutathione (GSH)2 7.

Metabolic Regulation

Glycine influences metabolic pathways by regulating enzymes involved in lipid metabolism. It decreases the activity of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL), which are crucial for lipid storage and mobilization. This helps in reducing adipocyte hypertrophy and improving metabolic profiles in conditions like metabolic syndrome8.

Enhancement of NMDA Receptor Function

Glycine enhances NMDA receptor function by inhibiting its reuptake through glycine transporter type 1 (GlyT1). This mechanism has been explored for its potential in treating neuropsychiatric disorders like schizophrenia and major depressive disorder. Inhibition of glycine reuptake increases glycine levels in the cerebrospinal fluid, thereby enhancing NMDA receptor activity3 9.

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Common Complaints Associated with Glycine Use

Neurological Symptoms

Increased Risk of Neurological Symptoms: During transurethral resection of the prostate, absorption of glycine 1.5% was associated with a significantly higher risk of neurological symptoms, such as nausea, compared to mannitol 3%. The risk was 4.8 times higher for those who absorbed glycine1.

Palatability Issues

Taste and Nausea: In a study on the use of glycine as an adjunctive treatment for Obsessive-Compulsive Disorder (OCD), regimen non-adherence was primarily due to complaints about the taste and nausea. These issues led to a high dropout rate, indicating that palatability is a significant concern for patients taking glycine2.

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Disclaimer

The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.

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