Green tea is a cortisol inhibitor, and it may well be a very effective one. Pharmacologists at University Medical School Schleswig-Holstein in Germany discovered this when they did an in-vitro study. Unfortunately it’s still too soon to say what the dosage should be.
The enzyme 11-beta-HSD-1 converts the inactive hormone cortisone into the stress hormone cortisol in the body. Another enzyme, 11-beta-HSD-2, converts cortisol back into cortisone.
If you reduce the action of 11-beta-HSD-1 in lab animals, they lose abdominal fat. Their cells become more insulin sensitive, their cholesterol level improves and their blood pressure goes down. 11-Beta-HSD-1 blockers might be interesting for medicines to treat type 2 diabetes for instance.
Green, black and white tea
In traditional Chinese medicine, tea is used to treat type 2 diabetes. So might tea be an 11-beta-HSD-1 inhibitor?
To try and answer this question the German researchers exposed liver cells to extracts of green, black and white tea, added cortisone to the liver cells and then measured how much cortisol was produced. All three types of tea inhibited the creation of cortisol considerably, but green tea worked best.
But green tea contains many, many substances. The researchers exposed liver cells to the most important substances found in green tea and then measured how well they inhibited the conversion of cortisone into cortisol.
Two substances, (-)-epigallocatechin gallate [EGCG] and (-)-gallocatechin [GC], turned out to be cortisol inhibitors.
The researchers used spatial models of 11-beta-HSD-1 to work out how EGCG deactivates the enzyme. The discovered that EGCG takes over the spot in the enzyme that is meant for cortisone. [Figure] As a result the conversion of cortisone into cortisol cannot take place.
“Our results decipher the mechanism by which catechins such as EGCG, or green tea in general, have been successfully consumed for thousand of years for general health benefits”, the researchers wrote. “These polyphenolic compounds may serve as model structures for the development of novel agents to treat the metabolic syndrome and related diseases.”
Green tea and one of its constituents, Epigallocatechine-3-gallate, are potent inhibitors of human 11?-hydroxysteroid dehydrogenase type 1.
The microsomal enzyme 11?-hydroxysteroid deydrogenase type 1 (11?-HSD1) catalyzes the interconversion of glucocorticoid receptor-inert cortisone to receptor- active cortisol, thereby acting as an intracellular switch for regulating the access of glucocorticoid hormones to the glucocorticoid receptor. There is strong evidence for an important aetiological role of 11?-HSD1 in various metabolic disorders including insulin resistance, diabetes type 2, hypertension, dyslipidemia and obesity. Hence, modulation of 11?-HSD1 activity with selective inhibitors is being pursued as a new therapeutic approach for the treatment of the metabolic syndrome. Since tea has been associated with health benefits for thousands of years, we sought to elucidate the active principle in tea with regard to diabetes type 2 prevention. Several teas and tea specific polyphenolic compounds were tested for their possible inhibition of cortisone reduction with human liver microsomes and purified human 11?-HSD1. Indeed we found that tea extracts inhibited 11?-HSD1 mediated cortisone reduction, where green tea exhibited the highest inhibitory potency with an IC50 value of 3.749 mg dried tea leaves per ml. Consequently, major polyphenolic compounds from green tea, in particular catechins were tested with the same systems. (-)-Epigallocatechin gallate (EGCG) revealed the highest inhibition of 11?-HSD1 activity (reduction: IC50?=?57.99 µM; oxidation: IC50?=?131.2 µM). Detailed kinetic studies indicate a direct competition mode of EGCG, with substrate and/or cofactor binding. Inhibition constants of EGCG on cortisone reduction were Ki?=?22.68 µM for microsomes and Ki?=?18.74 µM for purified 11?-HSD1. In silicio docking studies support the view that EGCG binds directly to the active site of 11?-HSD1 by forming a hydrogen bond with Lys187 of the catalytic triade. Our study is the first to provide evidence that the health benefits of green tea and its polyphenolic compounds may be attributed to an inhibition of the cortisol producing enzyme 11?-HSD1.
PMID: 24404164 PMCID: PMC3880318 DOI: 10.1371/journal.pone.0084468 [PubMed – indexed for MEDLINE]