Bitter taste receptors protect against Alzheimer's, schizophrenia, and Parkinson's, but need zinc and bitter tasting peptides from dietary protein.
Brain bitter receptors need zippy zinc and pungent peptides. My health tongue twister for the day.
This was an excerpt in a long post that deserves a highlight:
“Correspondingly, it has been demonstrated that GPCRs [the group of bitter taste receptors are a type of G protein-coupled receptors (GPCRs), a larger category] are involved in neurotransmitter function and in the regulation of neuronal and hormone signaling. Furthermore, impairment of this signaling by these TAS2Rs [a specific type of bitter taste receptors] potentially contributes to CNS-related disorders, including Alzheimer’s disease, schizophrenia, and Parkinson’s [38, 39]. In rats, taste-transducing molecules are predominantly located in neurons, and TAS2R expression has been detected in multiple regions of the rat brains, including the brain stem, cerebellum, cortex, and nucleus accumbens [9, 40]. To date, natural ligands for TAS2Rs in the brain have not been reported, although bitter tasting di- and tri-peptides from food have been shown to access the brain via a peptide transporter . ” (Seo, et al, 2017)
This is important: “natural ligands for TAS2Rs in the brain have not been reported” but bitter tasting protein fragments from food (peptides) are carried into the brain on a peptide transporter.  What is likely meant is that no endogenous chemical that we make has been observed at the taste receptors within the brain - however - special transport molecules are made in order to carry bitter tasting protein fragments into the brain, similar to protein transport carriers for essential trace minerals. Suggesting protein is an essential nutrient as a brain signaling chemical in the diet, not just for muscle building. Of course it is, in the form of glycine and glutamine free amino acids, but peptides are a little bigger than a single amino acid. Di- or tri- peptides have two or three amino acids. Longer peptides are more like a bracelet of beads instead of a necklace - with the beads being different amino acids joined together in a chain. Then the protein chains fold. Some of the beads are electrically active and some are smaller and form a folding point (glycine).
And a simple fact - lack of zinc leads to an inability to transcribe bitter taste receptors (and odor receptors and other proteins) and the elderly on average need about twice as much zinc or even more, than the current recommended guideline. See this older post (transcendingsquare.com import) for more information - zinc also is needed for epigenetic regulation which helps prevent some disease conditions or cancerous changes in protein transcription.
In order for bitter taste receptors to function within the body, we also need to eat bitter tasting phytonutrients in our diet. The average diet is low in bitter tasting chemicals because they are removed during food processing in order to increase consumer acceptance. Example: Dark cocoa powder has the most phytonutrient content of chocolate products, dark chocolate next, milk chocolate less, and chocolate syrup has the least.
Take home points - to help prevent Alzheimer’s dementia and other neurologic degenerative conditions, eat adequate protein, bitter tasting phytonutrients like dark cocoa products, oregano and pomegranate peel, and zinc.
Other things help too, but then the list gets too long.
Disclaimer: This information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.
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