g-Aminobutyric Acid (Plasma)

γ-aminobutyric acid is also known as Gamma Amino-Butyric Acid (GABA).

- γ-aminobutyric acid affects control of cortisol.

- γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter that acts in the nervous system and the immune system. Inhibitory neurotransmitters block or prevent the chemical message from being passed along any farther. 

- GABA is known for producing a calming effect. It’s thought to play a major role in controlling nerve cell hyperactivity associated with anxiety, stress and fear.

- Dysregulation of γ-aminobutyric acid has been associated with cognition, oxidative stress, glucose tolerance, and mood disorders.

- GABA levels were diminished in currently depressed patients in a meta-analysis (n=373). Plasma GABA levels have varied in psychiatric disorders.

- Urine GABA was significantly increased in metabolic syndrome patients compared to controls.

- GABA blood levels were significantly lower in osteoporotic patients.

- Foods containing γ-aminobutyric acid include tea leaves, mulberry leaves, tomato, lactic acid bacteria, yeasts and molds, fermented milk and soy products, sourdough, sprouts of brown rice, barley and beans, and kimchi, or dietary supplements.

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Gamma-aminobutyric acid (GABA) is an amino acid that functions as an inhibitory neurotransmitter. It serves one-third of brain neurons and is involved in depression and mania.

Although there are some dietary supplement and food sources for GABA (cruciferous vegetables, spinach, tomatoes, beans, and rice), the primary source may be endogenous prodution. Nervous tissue, the gut microbiome, the liver, pancreas, and endothelial cells are important sources for production.

Endogenous GABA is produced by the decarboxylation of the excitatory neurotransmitter glutamic acid. It can also be produced from the diamine putrescine using diamine oxidase (DAO). Also, the gut microbiome is capable of synthesizing various hormones and neurotransmitters. For example, Lactobacillus and Bifidobacterium species can produce GABA.

In general, plasma GABA may reflect brain GABA activity, however urine GABA levels are felt not to correlate with CNS levels.

References:

- Petty F. Plasma concentrations of gamma-aminobutyric acid (GABA) and mood disorders: a blood test for manic depressive disease? Clin Chem. 1994;40(2):296-302.

- Briguglio M, Dell’Osso B, Panzica G, et al. Dietary Neurotransmitters: A Narrative Review on Current Knowledge. Nutrients. 2018;10(5):591.

- Brandes RP. A Buttery Taste to Vascular Biology: Endothelial Cells Generate and Release γ-Aminobutyric Acid. Circ Res. 2016;119(5):577-579.

- Lee H, Doud EH, Wu R, et al. Mechanism of inactivation of γ-aminobutyric acid aminotransferase by (1S,3S)-3-amino4-difluoromethylene-1-cyclopentanoic acid (CPP-115). J Am Chem Soc. 2015;137(7):2628-2640.

- Hardt J, Larsson LI, Hougaard DM. Immunocytochemical evidence suggesting that diamine oxidase catalyzes biosynthesis of gamma-aminobutyric acid in antropyloric gastrin cells. J Histochem Cytochem. 2000;48(6):839-846.

- Nicholson-Guthrie CS, Guthrie GD, Sutton GP, Baenziger JC. Urine GABA levels in ovarian cancer patients: elevated GABA in malignancy. Cancer Let. 2001;162(1):27-30.

- Galland L. The gut microbiome and the brain. J Med Food. 2014;17(12):1261-1272.

- Dhossche D, Applegate H, Abraham A, et al. Elevated plasma gamma-aminobutyric acid (GABA) levels in autistic youngsters: stimulus for a GABA hypothesis of autism. Med Science Mon. 2002;8(8):Pr1-6.

- Griffiths JA, Mazmanian SK. Emerging evidence linking the gut microbiome to neurologic disorders. Genome Med. 2018;10(1):98.