Effects of green tea extract on insulin resistance and glucagon-like peptide 1 in patients with type 2 diabetes and lipid abnormalities: a randomized, double-blinded, and placebo-controlled trial

PLoS One. 2014 Mar 10;9(3):e91163. doi: 10.1371/journal.pone.0091163. eCollection 2014.


The aim of this study is to investigate the effect of green tea extract on patients with type 2 diabetes mellitus and lipid abnormalities on glycemic and lipid profiles, and hormone peptides by a double-blinded, randomized and placebo-controlled clinical trial. This trial enrolled 92 subjects with type 2 diabetes mellitus and lipid abnormalities randomized into 2 arms, each arm comprising 46 participants. Of the participants, 39 in therapeutic arm took 500 mg green tea extract, three times a day, while 38 in control arm took cellulose with the same dose and frequency to complete the 16-week study. Anthropometrics measurements, glycemic and lipid profiles, safety parameters, and obesity-related hormone peptides were analyzed at screening and after 16-week course. Within-group comparisons showed that green tea extract caused a significant decrease in triglyceride and homeostasis model assessment of insulin resistance index after 16 weeks. Green tea extract also increased significantly high density lipoprotein cholesterol. The HOMA-IR index decreased from 5.4±3.9 to 3.5±2.0 in therapeutic arm only. Adiponectin, apolipoprotein A1, and apolipoprotein B100 increased significantly in both arms, but only glucagon-like peptide 1 increased in the therapeutic arm. However, only decreasing trend in triglyceride was found in between-group comparison. Our study suggested that green tea extract significantly improved insulin resistance and increased glucagon-like peptide 1 only in within-group comparison. The potential effects of green tea extract on insulin resistance and glucagon-like peptide 1 warrant further investigation.

Trial registration: ClinicalTrials.gov NCT01360567.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Demography
  • Diabetes Mellitus, Type 2 / blood*
  • Diabetes Mellitus, Type 2 / drug therapy*
  • Double-Blind Method
  • Female
  • Glucagon-Like Peptide 1 / metabolism*
  • Humans
  • Insulin Resistance*
  • Lipids / blood*
  • Male
  • Middle Aged
  • Placebos
  • Plant Extracts / pharmacology
  • Plant Extracts / therapeutic use*


  • Lipids
  • Placebos
  • Plant Extracts
  • Glucagon-Like Peptide 1

Associated data

  • ClinicalTrials.gov/NCT01360567

Grant support

This study was supported financially by the National Science Council, Taiwan, under Grant No. 101-2320-B-010-075. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.