Genotype Distribution of the ACTN3 p.R577X Polymorphism in Elite Badminton Players: A Preliminary Study

Abstract

La α-actinina-3 es una proteína con un papel estructural en la línea Z sarcomérica en el músculo esquelético. Como solo está presente en las fibras musculares de tipo rápido, la α-actinina-3 se considera un componente mecánico clave para producir contracciones musculares de alta intensidad y para soportar la tensión externa aplicada al músculo esquelético. La α-actinina-3 está codificada por el gen ACTN3, que tiene un polimorfismo de un solo nucleótido (p.R577X; rs1815739) que afecta la expresión de α-actinina-3 debido a la presencia de un codón de parada. Los individuos homocigotos para el alelo 577R (es decir, genotipo RR) y heterocigotos RX expresan α-actinina-3 funcional, mientras que los homocigotos para el 577X (es decir, genotipo XX) expresan una proteína no funcional. Existe amplia evidencia que respalda las asociaciones entre el genotipo ACTN3 y el rendimiento deportivo, con frecuencias más altas del alelo 577R en atletas de élite y profesionales de velocidad y potencia que en las poblaciones de control. Esto sugiere una influencia beneficiosa de poseer α-actinina-3 funcional para convertirse en un atleta de élite en disciplinas basadas en la potencia. Sin embargo, ninguna investigación previa ha determinado la frecuencia de los genotipos ACTN3 en jugadores de bádminton de élite, a pesar de que este deporte se caracteriza por acciones de alta intensidad y carácter intermitente como cambios de dirección, aceleraciones, saltos y golpes.

α-Actinin-3 is a protein with a structural role at the sarcomeric Z-line in skeletal muscle. As it is only present in fast-type muscle fibers, α-actinin-3 is considered a key mechanical component to produce high-intensity muscle contractions and to withstand external tension applied to the skeletal muscle. α-Actinin-3 is encoded by the gene ACTN3, which has a single-nucleotide polymorphism (p.R577X; rs1815739) that affects the expression of α-actinin-3 due to the presence of a stop codon. Individuals homozygous for the 577R allele (i.e., RR genotype) and RX heterozygotes express functional α-actinin-3, while those homozygous for the 577X (i.e., XX genotype) express a non-functional protein. There is ample evidence to support the associations between the ACTN3 genotype and athletic performance, with higher frequencies of the 577R allele in elite and professional sprint and power athletes than in control populations. This suggests a beneficial influence of possessing functional α-actinin-3 to become an elite athlete in power-based disciplines. However, no previous investigation has determined the frequency of the ACTN3 genotypes in elite badminton players, despite this sport being characterized by high-intensity actions of intermittent nature such as changes of direction, accelerations, jumps and smashes. The purpose of this study was to analyze ACTN3 R577X genotype frequencies in professional badminton players to establish whether this polymorphism is associated with elite athlete status. A total of 53 European Caucasian professional badminton players competing in the 2018 European Badminton Championships volunteered to participate in the study. Thirty-one were men (26.2 ± 4.4 years) and twenty-two were women (23.4 ± 4.5 years). Chi-squared tests were used to analyze the differences in the distribution of ACTN3 genotypes (RR, RX and XX) between categories and sexes. The ACTN3 RR genotype was the most frequent in the sample of professional badminton players (RR = 49.1%, RX = 22.6% and XX = 28.3%). None of the badminton players ranked in the world’s top ten possessed the XX genotype (RX = 60%, RR = 40%). The distribution of the ACTN3 genotypes was similar between male and female professional badminton players (men: RR = 45.2%, RX = 25.8% and XX = 29.0%; women: RR = 54.5%, RX = 18.2% and XX = 27.3%; χ2 = 0.58; p = 0.750). The distribution of the ACTN3 genotypes in badminton players was different from the 1000 genome database for the European population (χ2 = 15.5; p < 0.001), with an overrepresentation of the RR genotype (p < 0.05) and an underrepresentation of the RX genotype (p < 0.01). In conclusion, the expression of functional α-actinin-3, associated with RR and RX genotypes in the ACTN3 gene may confer an advantage for reaching the status of elite athlete in badminton, and especially the world’s top-ten ranking. Large-scale studies with different ethnic backgrounds are needed to confirm the association of the R allele of ACTN3 with badminton performance.