The Influence Of Caffeine And A CYP1A2 Polymorphism On The Ventilatory Threshold - A Pilot Study

Abstract

Previous research suggests acute caffeine supplementation may alter substrate utilization and/or ventilatory responses that influence the ventilatory threshold (VT). Caffeine metabolism is influenced by a single nucleotide polymorphism at intron 1 of the cytochrome P450 (CYP1A2) gene, which may influence the ergogenic effects associated with caffeine use. PURPOSE: The purpose of this study was to examine the influence of caffeine on exercise responses at the VT, and determine the effect of the CYP1A2 polymorphism on those responses. METHODS: 17 healthy men (age 24.8 ± 2.7 yrs; weight 79.5 ± 9.2 kg) participated in this study. Subjects performed graded maximal exercise tests on a cycle ergometer after consuming either 6 mg/kg of caffeine or placebo. Subjects were categorized as possessing the C allele (C allele carriers) (n = 8) or being homozygous for the A allele (AA homozygotes) (n = 9). VT was determined using the V-slope method. The effects of caffeine (CAF) vs placebo (PL), genotype, and treatment x genotype were assessed using a two-factor ANOVA. RESULTS: At the VT, caffeine significantly augmented workload (CAF= 220 ± 43 Watts, PL= 211 ± 46 Watts), VO2 (CAF= 33.5 ± 8.2, PL= 32.2 ± 7.7 ml/kg/min), VO2 as a % of VO2max (CAF= 69.0 ± 8.2%, PL= 64.8 ± 9.6%), RER (CAF= 0.98 ± 0.06, PL= 0.95 ± 0.07), and HR (CAF= 155 ± 16, PL= 151 ± 16 bpm), compared to placebo (all p<0.05). A significant treatment x genotype interaction was observed for RER (AA group: CAF= 0.99 ± 0.07, PL= 0.91 ± 0.08; C allele: CAF= 0.97 ± 0.07, PL= 0.97 ± 0.09). A non-significant between group trend was observed for VO2 as a % of VO2max (AA group 62.5 ± 6.6%, C allele = 67.2 ± 9.6% p=0.10, eta2=0.17) and workload (AA group 196.4 ± 37.7, C allele = 214.1 ± 40.0 Watts, p=0.10, eta2=0.17). CONCLUSION: Caffeine enhances exercise performance at the VT. The CYP1A2 polymorphism likely modulates substrate utilization and exercise intensity at the VT. Additional research is needed to verify these preliminary findings.