The significance of CYP1A2 genotype on caffeine metabolism and exercise performance : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Human Nutrition at Massey University, Manawatu, New Zealand
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Date
2015
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Massey University
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Abstract
Objective: The objective of this study was to investigate whether a single
nucleotide polymorphism (C to A transversion at position -163 downstream of
the first transcribed nucleotide) in the enzyme that metabolizes caffeine
(CYP1A2), would explain the variability seen in caffeine related responses in
endurance exercise performance. In a double blind crossover trial, well
trained male endurance athletes (n=11, mean VO2 max 69±4 mL.kg-1.min-1)
ingested either caffeine (5 mg.kg-1) or a placebo 60 minutes prior to
performing a lab based experimental protocol involving a two hour steady
state cycle (70% VO2 max) followed by a 30 minute time trial to measure
performance. The rate of caffeine metabolism over seven hours (inclusive of
exercise period) was also determined by the HPLC analysis of plasma
caffeine and its major metabolites, paraxanthine, theophylline and
theobromine. Caffeine metabolism at rest over a similar seven hour period
was also determined in the same manner.
Results: Caffeine improved endurance performance by 7.1% (p=0.037)
compared to a placebo. Caffeine also significantly elevated heart rate during
the time trial (p=0.003); and RPE (p=0.010) and VO2 (p=0.047) during steady
state exercise. There was no correlation between caffeine or paraxanthine
concentrations at the start of the time trial and subsequent performance and
the rate of caffeine metabolism was not significantly different between resting
or exercising trials. Furthermore there was no significant interaction between
caffeine treatment and CYP1A2 genotype on performance or any other
variables measured. However there was a trend for carriers of the C allele
showing faster metabolism than those homozygous A/A (p=0.097).
Conclusions: Caffeine is ergogenic during endurance exercise, however
individual responses were variable. In this study this variability could not be
explained by CYP1A2 genotype. However the small sample size in this
study especially when subjects were divided into genotype groups, makes
drawing conclusions difficult.
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Keywords
Caffeine, Physiological effect, Metabolism, Endurance sports, Physiological aspects, Male athletes, Physiology, Research Subject Categories::INTERDISCIPLINARY RESEARCH AREAS::Domestic science and nutrition