Ambivalent role of gallated catechins in glucose tolerance in humans: a novel insight into non-absorbable gallated catechin-derived inhibitors of glucose absorption.

Abstract

Prolonged postprandial hyperglycemia is a detrimental factor for type 2 diabetes and obesity. The benefit of green tea extract (GTE) consumption still requires confirmation. We report the effects of circulating green tea catechins on blood glucose and insulin levels. Oral glucose loading 1 h after GTE ingestion in humans led to higher blood glucose and insulin levels than in control subjects. Gallated catechins were required for these effects, although within the intestinal lumen they have been known to decrease glucose and cholesterol absorption. Treatment with epigallocatechin-3-gallate hindered 2-deoxyglucose uptake into liver, fat, pancreatic beta-cell, and skeletal muscle cell lines. The glucose intolerance was ameliorated by gallated catechin-deficient GTE or GTE mixed with polyethylene glycol, which was used as an inhibitor of intestinal absorption of gallated catechins. These findings may suggest that the gallated catechin when it is in the circulation elevates blood glucose level by blocking normal glucose uptake into the tissues, resulting in secondary hyperinsulinemia, whereas it decreases glucose entry into the circulation when they are inside the intestinal lumen. These findings encourage the development of non-absorbable derivatives of gallated catechins for preventative treatment of type 2 diabetes and obesity, which would specifically induce only the positive luminal effect.

• Authors: J H Park, J Y Jin, W K Baek, S H Park, H Y Sung, Y K Kim, J Lee, D K Song
• Journal: Journal of physiology and pharmacology : an official journal of the Polish Physiological Society (J Physiol Pharmacol) Vol. 60 Issue 4 Pg. 101-9 (Dec 2009) ISSN: 1899-1505 [Electronic] Poland
• PMID: 20065503 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Kir6.2 channel
• Plant Extracts
• Potassium Channels, Inwardly Rectifying
• Tea
• Catechin
• epicatechin gallate
• epigallocatechin gallate
• gallocatechol
• Glucose

Topics

• 3T3-L1 Cells
• Adult
• Animals
• Catechin (administration & dosage, analogs & derivatives, analysis, pharmacology)
• Cell Line
• Drug Administration Routes
• Glucose (metabolism)
• Glucose Intolerance (physiopathology)
• Hep G2 Cells
• Humans
• Intestinal Absorption (drug effects)
• Male
• Mice
• Mice, Knockout
• Plant Extracts (administration & dosage, chemistry, pharmacology)
• Potassium Channels, Inwardly Rectifying (deficiency)
• Rats
• Rats, Sprague-Dawley
• Tea (chemistry)
• Young Adult