Abstract
BACKGROUND: The monocarboxylate transporter 1 (MCT1) plays a crucial role in regulating lactate and pyruvate transport across cell membranes, which is essential for energy metabolism during exercise. The MCT1 A1470T (rs1049434) polymorphism has been suggested to influence lactate transport, with the T (major) allele associated with greater transport efficiency. This study aimed to investigate the effect of the MCT1 polymorphism on lactate and potassium (K(+)) concentrations in response to resistance exercise (RE) following caffeine (CAF) ingestion. METHODS: Thirty resistance-trained athletes were randomly selected to participate in a randomized, double-blind, placebo-controlled crossover study. Participants consumed either CAF (6 mg/kg of body weight) or a placebo (PL; 6 mg of maltodextrin per kg of body weight) one hour before performing RE. Serum lactate and potassium concentrations were measured before exercise (Pre), immediately after (Post), and 15 min post-exercise (15 min Post). The RE protocol consisted of three sets to failure at 85% of 1RM for each exercise, with 2 min rest intervals between sets. RESULTS: The findings indicate that under caffeine consumption, individuals carrying the A (minor) allele had significantly higher blood lactate levels before (p = 0.037) and immediately after (p = 0.0001) resistance exercise compared to those with the TT genotype. Additionally, caffeine consumption moderated the increase in plasma potassium levels in TT genotype carriers, while A allele carriers exhibited elevated potassium levels 15 min post-exercise, regardless of caffeine or placebo intake (p < 0.05). CONCLUSIONS: Our findings suggest that the MCT1 A1470T polymorphism may influence lactate metabolism and clearance under caffeine consumption, potentially impacting exercise performance and recovery.