What are the properties of Stevia?
Analyzing the chemical composition of the plant we find the presence of:
- - Glucosides (sweeteners): stevioside (a-3), rebaudioside (AF), dulcoside (AB)
- - Terpenes (excitatory on the CNS): stevioside, rebaudioside, iso steviolo
- - Flavonoids, vitamins A and C
The real studies have been carried out in the last decade; after excluding any possible toxicity, the following properties have been ascertained: antihypertensive, tonic on the heart (thanks to the analogous glucosides to the digital ones), antidiabetogena and central sweetener:
- - stevioside acts as a typical systemic vasodilator, resulting in hypotension, natriuresis and diuresis with increased VFG, thus resulting in hypotensive
- - stevioside acts directly on the beta cell, determining secretion of insulin, thus resulting antihyperglycemic, ie hypoglycemic; this at the molecular level has been demonstrated by highlighting how the molecule activates acetylCoA carboxylase and the expression of the ACC gene, both involved in a qualitatively and quantitatively better secretion of insulin by the beta cell thanks to the K + -ATP dependent channels normally supported by receptors for sulphonylureas
- - stevioside and rebaudioside also have central effects, being diterpenes: they have a sweetening power up to 300 times greater than sugar, a function which can be attributed precisely to the neurotransmitter essence of the molecules themselves; this involves a reduction in the feeling of hunger with beneficial effects especially for patients with a tendency to diabetes and obesity; thanks to this property the 2004 Internationale Symposium of the University of Loanio has affirmed its use as sweeteners, having already been used as supplements since 1995 in the USA
- - isosteviol, predominantly having a diterpenic action, has also been shown to modify the expression of key genes in the regulation of insulin (GLUT2, Ins1, Ins2, ...) resulting in an upregulation of the expression of beta-cell genes and subsequent improvement of glucose sensitivity and lipid profile
What emerges is a picture in which diterpenic glucosides perform multiple functions: first they stimulate insulin sensitivity with direct action on the beta cell thanks to gene upregulation, with consequent increase in the amount of insulin; this determines a reorganization of the glycemic metabolism at the peripheral level.But above all, the action affects the VTA. The increase in insulin and the glycemic rebalance reduce insulin resistance and rehabilitate reward functions, with a relative increase in dopamine.
The action of stevia on the mechanism of reward mesencephalic is mainly achieved thanks to its diterpenes stevioside, rebaudioside and isosteviolo, which are then revealed nootropic molecules. Diterpenes are molecules intrinsically capable of acting directly on the dopaminergic system: they are made up of four units of isoprene with a total C20H32 formula, and their action consists of an increase in adenylyl cyclase activity with final dopaminergic stimulation.
The analogy can be traced back to the molecular action of steviosides: as well as binding the receptor for sulphonylureas, associated on the plasma membrane of the pancreatic beta cell to the channels for the K + ATP dependent with consequent closure of the K channel and depolarization of Ca ++ input and insulin secretion (although it has been shown that insulin secretion is also directly induced ), as diterpenic glycosides inhibit (in a similar way to digital on the myocyte) Na + / K + / ATPase with relative increase in Na + intracellular and electrochemical balance such as to determine an increase in dopamine.
The increased dopamine is therefore the basis for a recovery of reward mechanisms based in the mesencephalic VTA.
This article is translated and taken from the Dr. Dora Dragoni's article "Stevia e Reward Pathway" on www.neuroscienze.net
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