Abstract
IntroductionGreen tea(GT) is able to increase energy expenditure(EE) and fat oxidation(FATox) via inhibition of catechol-O-methyl transferase(COMT) by catechins. However, this does not always appear unanimously because of large inter-individual variability. This may be explained by different alleles of the functional COMT Val108/158Met polymorphism that are associated with COMT enzyme activity; high-activity enzyme, COMTH(Val/Val genotype), and low-activity COMTL(Met/Met genotype).MethodsFourteen Caucasian subjects (BMI: 22.2±2.3 kg/m2, age: 21.4±2.2 years) of whom 7 with the COMTH-genotype and 7 with the COMTL-genotype were included in a randomized, cross-over study in which EE and substrate oxidation were measured with a ventilated-hood system after decaffeinated GT and placebo(PL) consumption.ResultsAt baseline, EE, RQ, FATox and carbohydrate oxidation(CHOox) did not differ between groups. Significant interactions were observed between COMT genotypes and treatment for RQ, FATox and CHOox (p<0.05). After GT vs. PL, EE(GT: 62.2 vs. PL: 35.4 kJ.3.5 hrs; p<0.01), RQ(GT: 0.80 vs. PL: 0.83; p<0.01), FATox(GT: 18.3 vs. PL: 15.3 g/d; p<0.001) and CHOox(GT: 18.5 vs. PL: 24.3 g/d; p<0.001) were significantly different for subjects carrying the COMTH genotype, but not for subjects carrying the COMTL genotype (EE, GT: 60.3 vs. PL: 51.7 kJ.3.5 hrs; NS), (RQ, GT: 0.81 vs. PL: 0.81; NS), (FATox, GT: 17.3 vs. PL: 17.0 g/d; NS), (CHOox, GT: 22.1 vs. PL: 21.4 g/d; NS).ConclusionSubjects carrying the COMTH genotype increased energy expenditure and fat-oxidation upon ingestion of green tea catechins vs, placebo, whereas COMTL genotype carriers reacted similarly to GT and PL ingestion. The differences in responses were due to the different responses on PL ingestion, but similar responses to GT ingestion, pointing to different mechanisms. The different alleles of the functional COMT Val108/158Met polymorphism appear to play a role in the inter-individual variability for EE and FATox after GT treatment.Trial RegistrationNederlands Trial register NTR1918
Highlights
Green tea(GT) is able to increase energy expenditure(EE) and fat oxidation(FATox) via inhibition of catechol-Omethyl transferase(COMT) by catechins
The single nucleotide polymorphism of the COMT genotype was in Hardy Weinberg equilibrium (Table 3)
Significant interactions were observed between COMT genotypes and treatment for RQ, Fat oxidation (FATox) and CHOox (p,0.05) (Table 5)
Summary
Green tea(GT) is able to increase energy expenditure(EE) and fat oxidation(FATox) via inhibition of catechol-Omethyl transferase(COMT) by catechins. This does not always appear unanimously because of large interindividual variability. Stimulation of EE by green tea (GT), rich in catechins and caffeine has attracted interest, especially because GT does not contain any energy itself, yet stimulates EE. Caffeine has been shown to stimulate thermogenesis and fat oxidation in humans [6,7,8]. The methylation of catechins by catechol-O-methyltransferase (COMT) and the inhibition of phosphodiesterase by caffeine appear to be the principal mechanisms behind the stimulating properties of GT. The importance of GT catechins in stimulating EE was shown by Dulloo et al [9] who observed that the thermogenic effect of GT extract containing caffeine and catechins, is greater than that of an equivalent amount of caffeine
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