Summary: Optimal intake of B-type procyanidins, a class of polyphenols found in apples, cocoa, and red wine, is related to metabolic and hemodynamic responses.
Font: Shibaura Institute of Technology
Type B procyanidins, made from catechin oligomers, are a class of polyphenols found abundantly in foods such as cocoa, apples, grape seeds, and red wine.
Several studies have established the benefits of these micronutrients in reducing the risk of cardiovascular disease and stroke. Type B procyanidins are also successful in controlling hypertension, dyslipidemia, and glucose intolerance.
Studies attest to the physiological benefits of its intake on the central nervous system (CNS), specifically an improvement in cognitive functions.
These physiological changes follow a pattern of hormesis, a phenomenon in which the maximum benefits of a substance are achieved at medium doses and become progressively less at lower and higher doses.
The dose-response relationship of most bioactive compounds follows a monotonic pattern, with a larger dose showing a larger response. However, in some rare cases, a U-shaped dose-response curve is observed.
This U-shaped curve stands for hormesis, an adaptive response, in which a low dose of a generally harmful compound induces resistance in the body to its higher doses. This means that exposure to low levels of a noxious trigger can induce the activation of stress-resistant pathways, leading to increased repair and regeneration capacity.
In the case of type B procyanidins, several in vitro studies support its hormetic effects, but these results have not been proven live.
To address this knowledge gap, researchers at the Shibaura Institute of Technology (SIT), Japan, led by Professor Naomi Osakabe from the Department of Bioscience and Engineering, reviewed data from intervention trials supporting hormetic responses to ingestion of type B procyanidin.
The team, made up of Taiki Fushimi and Yasuyuki Fujii from the Graduate School of Engineering and Science (SIT), also conducted in alive experiments to understand possible connections between B-type procyanidin hormetic responses and CNS neurotransmitter receptor activation.
His article became available online on June 15, 2022 and was published in volume 9 of Nutrition Frontiers on September 7, 2022.
The researchers noted that a single oral administration of an optimal dose of cocoa flavanol temporarily increased blood pressure and heart rate in rats. But hemodynamics did not change when the dose was increased or decreased. Administration of B-type procyanidin monomer and various oligomers produced similar results.
According to Professor Osakabe, “These results are consistent with those of intervention studies after a single intake of foods rich in procyanidin type B, and support the U-shaped dose-response theory, or hormesis, of polyphenols.” “.
To see if the sympathetic nervous system (SNS) is involved in the hemodynamic changes induced by B-type procyanidins, the team administered adrenaline blockers to test rats.
This successfully decreased the temporary increase in heart rate induced by the optimal dose of cocoa flavanol. A different type of blocker, the a1 blocker, inhibited the transient increase in blood pressure.
This suggested that the SNS, which controls the action of adrenaline blockers, is responsible for the hemodynamic and metabolic changes induced by a single oral dose of type B procyanidin.
Next, the researchers determined why optimal doses, and not high doses, are responsible for thermogenic and metabolic responses. They co-administered a high dose of cocoa flavanol and yohimbine (an α2-blocker) and noted a temporary but clear increase in blood pressure in the test animals. Similar observations were made with the use of B-type procyanidin oligomer and yohimbine.
Professor Osakabe conjectures: “Since α2 blockers are associated with downregulation of the SNS, the reduced metabolic and thermogenic outputs at a high dose of B-type procyanidins observed in our study may have induced α2 autoreceptor activation. Therefore, the deactivation of the SNS can be induced by a high dose of B-type procyanidins”.
Previous studies have demonstrated a role for the gut-brain axis in the control of stress-related hormetic responses. Activation of the hypothalamic-pituitary-adrenal (HPA) axis by optimal stress has a strong influence on memory, cognition, and stress tolerance.
This article highlights how HPA activation occurs after a single dose of type B procyanidin, suggesting that stimulation with an oral dose of type B procyanidin could be a stressor for mammals and lead to activation of the SNS.
Hormesis and its triggering biochemical pathways provide protection against various pathological and aging processes, improving our overall health and making us resistant to future stress.
Although the exact relationship between B-type procyanidins and the CNS needs more research, the health benefits of foods rich in B-type procyanidins remain undisputed.
Financing information
This study was supported by JSPS KAKENHI (Grant Number: 19H04036).
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About this research news on diet and neuroscience
Author: wang yu
Font: Shibaura Institute of Technology
Contact: Wang Yu – Shibaura Institute of Technology
Image: The image is in the public domain.
original research: Open access.
“The hormetic response to procyanidin type B ingestion involves stress-related neuromodulation via the gut-brain axis: preclinical and clinical observations.” by Taiki Fushimi et al. Frontiers in Nutrition
Summary
The hormetic response to procyanidin type B ingestion involves stress-related neuromodulation via the gut-brain axis: preclinical and clinical observations.
B-type procyanidins, a series of catechin oligomers, are among the most ingested polyphenols in the human diet.
The results of meta-analyses have suggested that intake of type B procyanidins reduces the risk of cardiovascular disease.
Another recent focus has been on the effects of B-type procyanidins on central nervous system (CNS) function.
Although long-term ingestion of type B procyanidin is associated with health benefits, a single oral intake has been reported to cause physiological disturbances in circulation, metabolism, and the CNS.
Extensive analyzes of previous reports indicate a mid-range dose optima for hemodynamic effects of B-type procyanidins, with no responses at lower or higher doses, suggesting hormesis.
In fact, polyphenols, including B-type procyanidins, elicit hormetic responses in vitro, but clinical and animal studies are limited. However, hormesis of hemodynamic and metabolic responses to B-type procyanidins was recently confirmed in animal studies, and our work has linked these effects to the CNS.
Here, we evaluate the hormetic response elicited by B-type procyanidins, recontextualizing the results of intervention trials. In addition, we discuss the possibility that this hormetic response to B-type procyanidins arises through CNS neurotransmitter receptors.
We have checked the direction of future research for B-type procyanidins in this review.
