title: Green Tea Extract and Catechol-O-Methyltransferase Genotype Modify Fasting Serum Insulin and Plasma Adiponectin Concentrations in a Randomized Controlled Trial of Overweight and Obese Postmenopausal Women.
abstract: BACKGROUND
  Green tea consumption has been associated with favorable changes in body weight and obesity-related hormones, although it is not known whether these changes result from green tea polyphenols or caffeine.
  
  
  OBJECTIVE
  We examined the impact of decaffeinated green tea extract (GTE) containing 843 mg of (-)-epigallocatechin-3-gallate on anthropometric variables, obesity-associated hormones, and glucose homeostasis.
  
  
  METHODS
  The Minnesota Green Tea Trial was a 12-mo randomized, double-blind, placebo-controlled clinical trial of 937 healthy postmenopausal women assigned to either decaffeinated GTE (1315 mg total catechins/d) or a placebo, stratified by catechol-O-methyltransferase (COMT) genotype. This study was conducted in a subset of 237 overweight and obese participants [body mass index (BMI) ≥25 kg/m(2)].
  
  
  RESULTS
  No changes in energy intake, body weight, BMI, or waist circumference (WC) were observed over 12 mo in women taking GTE (n = 117) or placebo (n = 120). No differences were seen in circulating leptin, ghrelin, adiponectin, or glucose concentrations at month 12. Participants randomly assigned to GTE with baseline insulin ≥10 μIU/mL (n = 23) had a decrease in fasting serum insulin from baseline to month 12 (-1.43 ± 0.59 μIU/mL), whereas those randomly assigned to placebo with baseline insulin ≥10 μIU/mL (n = 19) had an increase in insulin over 12 mo (0.55 ± 0.64 μIU/mL, P < 0.01). Participants with the homozygous high-activity (G/G) form of COMT had significantly lower adiponectin (5.97 ± 0.50 compared with 7.58 ± 0.53 μg/mL, P = 0.03) and greater insulin concentrations (7.63 ± 0.53 compared with 6.18 ± 0.36 μIU/mL, P = 0.02) at month 12 compared with those with the low-activity (A/A) genotype, regardless of treatment group.
  
  
  CONCLUSIONS
  Decaffeinated GTE was not associated with reductions in body weight, BMI, or WC and did not alter energy intake or mean hormone concentrations in healthy postmenopausal women over 12 mo. GTE decreased fasting insulin concentrations in those with elevated baseline fasting concentrations. The high-activity form of the COMT enzyme may be associated with elevations in insulin and a reduction in adiponectin concentrations over time. This trial was registered at http://www.clinicaltrials.gov as NCT00917735.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN;
authors.forename: Allison M
authors.initials: AM
authors.lastname: Dostal
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN;
authors.forename: Hamed
authors.initials: H
authors.lastname: Samavat
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN;
authors.forename: Luis
authors.initials: L
authors.lastname: Espejo
authors.affiliation: Department of Nutrition and Dietetics, University of North Florida, Jacksonville, FL; and.
authors.forename: Andrea Y
authors.initials: AY
authors.lastname: Arikawa
authors.affiliation: Department of Nutrition, Exercise, and Health Sciences, Central Washington University, Ellensburg, WA.
authors.forename: Nicole R
authors.initials: NR
authors.lastname: Stendell-Hollis
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN; mkurzer@umn.edu.
authors.forename: Mindy S
authors.initials: MS
authors.lastname: Kurzer
mesh_terms: D052242:Adiponectin / Q000097:blood*; D000284:Administration, Oral; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001835:Body Weight; D002110:Caffeine / Q000008:administration & dosage / Q000032:analysis; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives; D002394:Catechol O-Methyltransferase / Q000235:genetics*; D004311:Double-Blind Method; D002149:Energy Intake; D005215:Fasting; D005260:Female; D005838:Genotype; D054439:Ghrelin / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood*; D020738:Leptin / Q000097:blood; D008875:Middle Aged; D009043:Motor Activity; D015596:Nutrition Assessment; D009765:Obesity / Q000097:blood*; D050177:Overweight / Q000097:blood*; D010936:Plant Extracts / Q000008:administration & dosage; D059808:Polyphenols / Q000008:administration & dosage; D017698:Postmenopause; D013662:Tea / Q000737:chemistry*; D055105:Waist Circumference
chemical_list: D052242:Adiponectin; D001786:Blood Glucose; D054439:Ghrelin; D007328:Insulin; D020738:Leptin; D010936:Plant Extracts; D059808:Polyphenols; D013662:Tea; D002110:Caffeine; D002392:Catechin; C045651:epigallocatechin gallate; D002394:Catechol O-Methyltransferase
keywords: adiponectin; green tea extract; insulin; obesity; postmenopausal women