Exercise influence on monocarboxylate transporter 1 (MCT1) and 4 (MCT4) in the skeletal muscle: A systematic review.
Level 2 - randomized trial
Systematic review synthesizing human and animal physiological intervention trials.
PubMed 38240467 · doi:10.1111/apha.14083
What was done
Systematic review following PRISMA guidelines to examine the effects of acute exercise and chronic training programs (varying in intensity and duration) on skeletal muscle monocarboxylate transporter 1 (MCT1) and 4 (MCT4) protein and mRNA expression in humans and rodents. Literature was searched via PubMed and Web of Science, and study quality across 41 included studies was evaluated using the Cochrane risk of bias tool.
What was found
The abstract provides qualitative synthesis without numerical effect sizes: - Exercise stimulated an increase in human skeletal muscle MCT1 protein content. - Muscle MCT4 protein levels increased after exercise training programs, though responsiveness was lower compared to MCT1. - Both transporter protein adaptations appeared to occur independently of exercise intensity. - The effects of exercise on muscle MCT1 and MCT4 mRNA expression remained poorly characterized, particularly in humans. - Rodent data only matched human results regarding training-induced increases in MCT1 protein content, failing to align across other parameters.
Why it matters
It establishes that regular exercise upregulates key lactate transport proteins in human skeletal muscle while warning against direct translation of rodent exercise adaptations for MCT4 and transcriptomic responses to humans.
Limits
The abstract reports no quantitative summary metrics, pooled effect sizes, or confidence intervals. Human and rodent data were evaluated together despite notable species differences. Dose-response relationships regarding exercise intensity and duration could not be clearly defined, and human mRNA data remain sparse.
Cited by
- supports High-intensity exercise training leads to an upregulation of monocarboxylate transporters (MCTs) in skeletal muscle to facilitate lactate transport.