The () Genetic Variant Is Associated with Muscle Fiber Size and Strength Athlete Status.

BACKGROUND

Data on the genetic factors contributing to inter-individual variability in muscle fiber size are limited. Recent research has demonstrated that mice lacking the Arkadia (RNF111) N-terminal-like PKA signaling regulator 2N (; also known as ) gene exhibit reduced muscle fiber size, contraction force, and exercise capacity, along with defects in calcium handling within fast-twitch muscle fibers. However, the role of the gene in human muscle physiology, and particularly in athletic populations, remains poorly understood. The aim of this study was threefold: (a) to compare gene expression between power and endurance athletes; (b) to analyze the relationship between gene expression and muscle fiber composition; and (c) to investigate the association between the functional variant of the gene, muscle fiber size, and sport-related phenotypes.

RESULTS

We found that gene expression was significantly higher in power athletes compared to endurance athletes ( = 0.042) and was positively associated with the proportion of oxidative fast-twitch (type IIA) muscle fibers in untrained subjects ( = 0.017, adjusted for age and sex). Additionally, we observed that the rs6507691 T allele, which predicts high gene expression ( = 3.8 × 10), was associated with a greater cross-sectional area of fast-twitch muscle fibers in strength athletes ( = 0.015) and was over-represented in world-class strength athletes (38.6%; OR = 2.2, = 0.023) and wrestlers (33.8%; OR = 1.8, = 0.044) compared to controls (22.0%).

CONCLUSIONS

In conclusion, appears to be a gene specific to oxidative fast-twitch myofibers, with its functional variant being associated with muscle fiber size and strength-athlete status.