Finishing a week’s worth of 2022 taurine research with two reviews of taurine’s brain effects:
“We provide a overview of brain taurine homeostasis, and review mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. Alterations to taurine homeostasis can impact a number of biological processes such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders.
Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given cytoprotective actions of taurine, such accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration.
Taurine release is mainly mediated by volume-regulated anion channels (VRAC) that are activated by hypo-osmotic conditions and electrical activity. They can be stimulated via glutamate metabotropic (mGluR) and ionotropic receptors (mainly NMDA and AMPA), adenosine A1 receptors (A1R), and metabotropic ATP receptors (P2Y).
Taurine mediates its neuromodulatory effects by binding to GABAA, GABAB, and glycine receptors. While taurine binding to GABAA and GABAB is weaker than to GABA, taurine is a rather potent ligand of the glycine receptor. Reuptake of taurine occurs via taurine transporter TauT.
Cytoprotective actions of taurine contribute to brain health improvements in subjects with obesity and diabetes through various mechanisms that improve neuronal function, such as:
- Modulating inhibitory neurotransmission, which promotes an excitatory–inhibitory balance;
- Stimulating antioxidant systems; and
- Stabilizing mitochondria energy production and Ca2+ homeostasis.”
https://www.mdpi.com/2072-6643/14/6/1292/htm “Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes”
A second review focused on taurine’s secondary bile acids produced by gut microbiota:
“Most neurodegenerative disorders are diseases of protein homeostasis, with misfolded aggregates accumulating. The neurodegenerative process is mediated by numerous metabolic pathways, most of which lead to apoptosis. Hydrophilic bile acids, particularly tauroursodeoxycholic acid (TUDCA), have shown important anti-apoptotic and neuroprotective activities, with numerous experimental and clinical evidence suggesting their possible therapeutic use as disease-modifiers in neurodegenerative diseases.
Biliary acids may influence each of the following three mechanisms through which interactions within the brain-gut-microbiota axis take place: neurological, immunological, and neuroendocrine. These microbial metabolites can act as direct neurotransmitters or neuromodulators, serving as key modulators of the brain-gut interactions.
The gut microbial community, through their capacity to produce bile acid metabolites distinct from the liver, can be thought of as an endocrine organ with potential to alter host physiology, perhaps to their own favour. Hydrophilic bile acids, currently regarded as important hormones, exert modulatory effects on gut microbiota composition to produce secondary bile acids which seem to bind a number of receptors with a higher affinity than primary biliary acids, expressed on many different cells.
TUDCA regulates expression of genes involved in cell cycle regulation and apoptotic pathways, promoting neuronal survival. TUDCA:
- Improves protein folding capacity through its chaperoning activity, in turn reducing protein aggregation and deposition;
- Reduces reactive oxygen species production, leading to protection against mitochondrial dysfunction;
- Ameliorates endoplasmic reticulum stress; and
- Inhibits expression of pro-inflammatory cytokines, exerting an anti-neuroinflammatory effect.
Although Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and cerebral ischemia have different disease progressions, they share similar pathways which can be targeted by TUDCA. This makes this bile acid a potentially strong therapeutic option to be tested in human diseases. Clinical evidence collected so far has reported comprehensive data on ALS only.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9166453/ “Tauroursodeoxycholic acid: a potential therapeutic tool in neurodegenerative diseases”