Is there an association between ACTN3 R577X polymorphism and muscle power phenotypes in young, non-athletic adults?

A Systematic Review and Meta-analysis of the Association Between ACTN3 R577X Genotypes and Performance in Endurance Versus Power Athletes and Non-athletes

BACKGROUND

Previous studies reported differences in genotype frequency of the ACTN3 R577X polymorphisms (rs1815739; RR, RX and XX) in athletes and non-athletic populations. This systematic review with meta-analysis assessed ACTN3 R577X genotype frequencies in power versus endurance athletes and non-athletes.

METHODS

Five electronic databases (PubMed, Web of Science, Scopus, Science Direct, SPORTDiscus) were searched for research articles published until December 31st, 2022. Studies were included if they reported the frequency of the ACTN3 R577X genotypes in power athletes (e.g., weightlifters) and if they included a comparison with endurance athletes (e.g., long-distance runners) or non-athletic controls. A meta-analysis was then performed using either fixed or random-effects models. Pooled odds ratios (OR) were determined. Heterogeneity was detected using I2 and Cochran's Q tests. Publication bias and sensitivity analysis tests were computed.

RESULTS

After screening 476 initial registrations, 25 studies were included in the final analysis (13 different countries; 14,541 participants). In power athletes, the RX genotype was predominant over the two other genotypes: RR versus RX (OR 0.70; 95% CI 0.57-0.85, p = 0.0005), RR versus XX (OR 4.26; 95% CI 3.19-5.69, p < 0.00001), RX versus XX (OR 6.58; 95% CI 5.66-7.67, p < 0.00001). The R allele was higher than the X allele (OR 2.87; 95% CI 2.35-3.50, p < 0.00001) in power athletes. Additionally, the frequency of the RR genotype was higher in power athletes than in non-athletes (OR 1.48; 95% CI 1.25-1.75, p < 0.00001). The RX genotype was similar in both groups (OR 0.84; 95% CI 0.71-1.00, p = 0.06). The XX genotype was lower in power athletes than in controls (OR 0.73; 95% CI 0.64-0.84, p < 0.00001). Furthermore, the R allele frequency was higher in power athletes than in controls (OR 1.28; 95% CI 1.19-1.38, p < 0.00001). Conversely, a higher frequency of X allele was observed in the control group compared to power athletes (OR 0.78; 95% CI 0.73-0.84, p < 0.00001). On the other hand, the frequency of the RR genotype was higher in power athletes than in endurance athletes (OR 1.27; 95% CI 1.09-1.49, p = 0.003). The frequency of the RX genotype was similar in both groups (OR 1.07; 95% CI 0.93-1.24, p = 0.36). In contrast, the frequency of the XX genotype was lower in power athletes than in endurance athletes (OR 0.63; 95% CI 0.52-0.76, p < 0.00001). In addition, the R allele was higher in power athletes than in endurance athletes (OR 1.32; 95% CI 1.11-1.57, p = 0.002). However, the X allele was higher in endurance athletes compared to power athletes (OR 0.76; 95% CI 0.64-0.90, p = 0.002). Finally, the genotypic and allelic frequency of ACTN3 genes were similar in male and female power athletes.

CONCLUSIONS

The pattern of the frequencies of the ACTN3 R577X genotypes in power athletes was RX > RR > XX. However, the RR genotype and R allele were overrepresented in power athletes compared to non-athletes and endurance athletes. These data suggest that the RR genotype and R allele, which is associated with a normal expression of α-actinin-3 in fast-twitch muscle fibers, may offer some benefit in improving performance development in muscle strength and power.

Muscle Work and Its Relationship with ACE and ACTN3 Polymorphisms Are Associated with the Improvement of Explosive Strength

Background: The potential influence of genetics in athletic performance allows the search for genetic profiles associated with muscular work for the orientation of strength training and sports selection. The purpose of the study was to analyze four muscular exercises for effectiveness in improving explosive strength variables, associated to the genetics in Angiotensin Converting Enzyme (ACE) and α-actinin-3 (ACTN3) polymorphisms. Methods: A randomized controlled trial was conducted on a sample of 80 subjects allocated into four groups: concentric muscle work (CMW), eccentric muscle work (EMW), concentric-eccentric muscle (C-EMW) work and isometric muscular work (IMW), by block and gender randomization. Vertical jump, long jump, power jump, and speed were measured to study explosive strength. Genotypic frequencies of ACE (rs4646994) and ACTN3 (rs1815739) were obtained by polymerase chain reaction. Results: ACE gen showed significant improvements regarding the DD genotype in the Sargent test (p = 0.003) and sprint velocity test (p = 0.017). In the ACTN3 gene, the RR variable obtained improvement results with regard to RX and XX variables in long jump (p < 0.001), Sargent test (p < 0.001) and power jump (p = 0.004). Conclusions: The selected genes demonstrated an influence on the muscle work and the improvement in explosive strength variables with a decisive role regarding the type of muscle work performed.

Association of the ACTN3 R577X (rs1815739) polymorphism with elite power sports: A meta-analysis

Objective

The special status accorded to elite athletes stems from their uncommon genetic potential to excel in world-class power sports (PS). Genetic polymorphisms have been reported to influence elite PS status. Reports of associations between the α-actinin-3 gene (ACTN3) R577X polymorphism and PS have been inconsistent. In light of new published studies, we perform a meta-analysis to further explore the roles of this polymorphism in PS performance among elite athletes.

Methods

Multi-database literature search yielded 44 studies from 38 articles. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used in estimating associations (significance threshold was set at P^a ≤ 0.05) using the allele-genotype model (R and X alleles, RX genotype). Outlier analysis was used to examine its impact on association and heterogeneity outcomes. Subgroup analysis was race (Western and Asian) and gender (male/female)-based. Interaction tests were applied to differential outcomes between the subgroups, P-values of which were Bonferroni corrected (P_{interaction BC}). Tests for sensitivity and publication bias were performed.

Results

Significant overall R allele effects (OR 1.21, 95% CI 1.07–1.37, P^a = 0.002) were confirmed in the Western subgroup (OR 1.11, 95% CI 1.01–1.22, P^a = 0.02) and with outlier treatment (ORs 1.12–1.20, 95% CIs 1.02–1.30, P^a < 10⁻⁵–0.01). This treatment resulted in acquired significance of the RX effect in Asian athletes (OR 1.91, 95% CI 1.25–2.92, P^a = 0.003). Gender analysis dichotomized the RX genotype and R allele effects as significantly higher in male (OR 1.14, 95% CI 1.02–1.28, P^a = 0.02) and female (OR 1.58, 95% CI 1.21–2.06, P^a = 0.0009) athletes, respectively, when compared with controls. Significant R female association was improved with a test of interaction (P_{interaction BC} = 0.03). The overall, Asian and female outcomes were robust. The R allele results were more robust than the RX genotype outcomes. No evidence of publication bias was found.

Conclusions

In this meta-analysis, we present clear associations between the R allele/RX genotype in the ACTN3 polymorphism and elite power athlete status. Significant effects of the R allele (overall analysis, Western and female subgroups) and RX genotype (Asians and males) were for the most part, results of outlier treatment. Interaction analysis improved the female outcome. These robust findings were free of publication bias.

Do ACE and CKMM gene variations have potent effects on physical performance in inactive male adolescents?

We studied to ascertain whether the ACE and/or CKMM genotypes independently influence the baseline level of some sport performances in 613 inactive male adolescents (mean ± SD age: 13.24 ± 0.28 years). All DNA samples were extracted and genotyped for ACE I/D and CKMM A/G polymorphisms using a PCR based procedure. One-way analysis of covariance was used to examine the discrepancies in the research phenotypes among various ACE and CKMM polymorphisms. The comparisons of genotype and allele frequencies between adolescents with the best and the worst performances were calculated and analyzed by the Chi square test. All procedures were approved by Medical University Ethics Committee. Written informed consent signed and approved by all subject`s parents were obtained. We observed the effect of the ACE and CKMM polymorphisms on VO_2max (P = 0.001 & P = 0.001 respectively). ACE and CKMM genotypes differed between groups (< 90th vs. ≥ 90) in the multi-stage 20 m shuttle run (P = 0.001 and 0.001). ACE allele frequencies differed between groups (< 90th vs. ≥ 90) in the multi-stage 20-m shuttle run (P = 0.001). This study suggests that the ACE and CKMM polymorphisms influence the endurance performance phenotype in non-trained adolescent males.

Association between the PPARa and PPARGCA gene variations and physical performance in non-trained male adolescents

The purpose of the research was to examine if some genetic variations are associated with some endurance, power and speed performances (multi-stage 20-m shuttle run, standing broad jump, 20 m sprint test and Abalakov jump) in a group of 586 non-trained male adolescents (mean ± SD age: 13.20 ± 0.25 years). Polymorphisms in PPARa and PPARGC1A implicated in physical performance traits were analyzed. DNA was extracted and the samples were genotyped for PPARa and PPARGC1A polymorphisms by a PCR based method followed by gel electrophoresis. The discrepancies in the study phenotypes among variations of the PPARa and PPARGC1A polymorphisms were analyzed by one-way analysis of covariance (ANCOVA), after age, weight and height adjustment. To examine whether the genotype and allele frequencies between adolescents with high and low performances were different, we divided them into two groups: ≥ 90th and < 90th of the percentile. The genotype and allele frequencies between adolescents with high and low performances were compared with the Chi square test. Our analysis demonstrated the effects of the PPARa and PPARGC1A polymorphisms only on [Formula: see text] (p = 0.010 and p = 0.010 respectively). Also, we observed significant differences in PPARa and PPARGC1A genotypes (p = 0.034 and p = 0.024) or allele frequencies (p = 0.031 and p = 0.001) between groups for the multi-stage 20-m shuttle run test. Findings of this research suggest that both the PPARa and PPARGC1A polymorphisms are associated with estimating endurance-related phenotype and endurance capacity in male non-athletes adolescents.

More than a 'speed gene': ACTN3 R577X genotype, trainability, muscle damage, and the risk for injuries

A common null polymorphism (rs1815739; R577X) in the gene that codes for α-actinin-3 (ACTN3) has been related to different aspects of exercise performance. Individuals who are homozygous for the X allele are unable to express the α-actinin-3 protein in the muscle as opposed to those with the RX or RR genotype. α-actinin-3 deficiency in the muscle does not result in any disease. However, the different ACTN3 genotypes can modify the functioning of skeletal muscle during exercise through structural, metabolic or signaling changes, as shown in both humans and in the mouse model. Specifically, the ACTN3 RR genotype might favor the ability to generate powerful and forceful muscle contractions. Leading to an overall advantage of the RR genotype for enhanced performance in some speed and power-oriented sports. In addition, RR genotype might also favor the ability to withstand exercise-induced muscle damage, while the beneficial influence of the XX genotype on aerobic exercise performance needs to be validated in human studies. More information is required to unveil the association of ACTN3 genotype with trainability and injury risk during acute or chronic exercise.

Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers

Purpose

To examine the effect of α-actinin-3 deficiency due to homozygosity for the ACTN3 577X-allele on contractile and morphological properties of fast muscle fibers in non-athletic young men.

Methods

A biopsy was taken from the vastus lateralis of 4 RR and 4 XX individuals to test for differences in morphologic and contractile properties of single muscle fibers. The cross-sectional area of the fiber and muscle fiber composition was determined using standard immunohistochemistry analyses. Skinned single muscle fibers were subjected to active tests to determine peak normalized force (P₀), maximal unloading velocity (V₀) and peak power. A passive stretch test was performed to calculate Young’s Modulus and hysteresis to assess fiber visco-elasticity.

Results

No differences were found in muscle fiber composition. The cross-sectional area of type II_a and II_x fibers was larger in RR compared to XX individuals (P<0.001). P₀ was similar in both groups over all fiber types. A higher V₀ was observed in type II_a fibers of RR genotypes (P<0.001) but not in type I fibers. The visco-elasticity as determined by Young’s Modulus and hysteresis was unaffected by fiber type or genotype.

Conclusion

The greater V₀ and the larger fast fiber CSA in RR compared to XX genotypes likely contribute to enhanced whole muscle performance during high velocity contractions.

Effective utilization of genetic information for athletes and coaches: focus on ACTN3 R577X polymorphism

Training variants (type, intensity, and duration of exercise) can be selected according to individual aims and fitness assessment. Recently, various methods of resistance and endurance training have been used for muscle hypertrophy and VO₂max improvement. Although several genetic variants are associated with elite athletic performance and muscle phenotypes, genetic background has not been used as variant for physical training. ACTN3 R577X is a well-studied genetic polymorphism. It is the only genotype associated with elite athletic performance in multiple cohorts. This association is strongly supported by mechanistic data from an Actn3-knockout mouse model. In this review, possible guidelines are discussed for effective utilization of ACTN3 R577X polymorphism for physical training.

Simple Method to Genotype the ACTN3 r577x Polymorphism

The alpha-actinin-3 r577x polymorphism (rs1815739) is one of the most important polymorphisms associated with athletic performance. This single-nucleotide mutation leads to a premature stop codon, resulting in a nonfunctional protein product. The presence of the dominant R allele is associated with full power skeletal muscle contraction. Homozygosity for the X allele is correlated with more efficient energy disposure. Restriction fragment length polymorphism and real-time polymerase chain reaction (PCR) are the standard methods used to genotype this polymorphism, but they are expensive and require special equipments. Here, we present a simple and cost-efficient method to genotype the ACTN3 r577x polymorphism by a single PCR. External primers yield a 690-bp product that indicates the template quality. Internal primers produce a 413-bp product if the R allele is present and a 318-bp product if the X allele is present. Our four-primer genotyping PCR was validated by the standard real-time PCR, generally used to genotype this single-nucleotide polymorphism, demonstrating the accuracy of this method. This protocol is perfect for small- or large-scale cohort genotyping of the ACTN3 r577x polymorphism.

ACTN3 R577X Polymorphism and Explosive Leg-Muscle Power in Elite Basketball Players

Purpose:

To determine the association of the ACTN3 R577X polymorphism with leg-muscle explosive power in Spanish (white) elite basketball players and controls.

Participants:

100 (60 men) elite basketball players (cases) and 283 nonathletic controls.

Methods:

The authors assessed power performance by means of the vertical-squat and countermovement-jump tests.

Results:

Genotype distributions did not differ between groups (cases: 37.0% [RR], 42.0% [RX], and 21.0% [XX]; controls: 31.8% [RR], 49.8% [RX], and 18.4% [XX]; P = .353). The authors did not observe any effect of the ACTN3 R577X polymorphism on study phenotypes in either group, including when they performed the analyses separately in men and women. They found no association between the ACTN3 R577X polymorphism and the likelihood of being an elite basketball player using the dominant or the recessive model, and the results remained unaltered when the analyses were adjusted for sex, weight, height, and age or when performed for men and women separately.

Conclusions:

Although the ACTN3 R577X is associated with explosive muscle performance and this phenotype is important in the sport of basketball (ie, during jumps), the authors found no association with leg explosive power in elite basket players or with the status of being this type of athlete.

The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power training

Background

We studied the influence of the ACE I/D and ACTN3 R577X polymorphisms (single or combined) on lower-extremity function in older women in response to high-speed power training.

Methods

One hundred and thirty-nine healthy older Caucasian women participated in this study (age: 65.5 ± 8.2 years, body mass: 67.0 ± 10.0 kg and height: 1.57 ± 0.06 m). Walking speed (S10) performance and functional capacity assessed by the “get-up and go” (GUG) mobility test were measured at baseline (T1) and after a consecutive 12-week period of high-speed power training (40-75% of one repetition maximum in arm and leg extensor exercises; 3 sets 4–12 reps, and two power exercises for upper and lower extremity). Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR methods. Genotype distributions between groups were compared by Chi-Square test and the gains in physical performance were analyzed by two-way, repeated-measures ANOVA.

Results

There were no significant differences between genotype groups in men or women for adjusted baseline phenotypes (P > 0.05). ACE I/D and ACTN3 polymorphisms showed a significant interaction genotype-training only in S10 (P = 0.012 and P = 0.044, respectively) and not in the GUG test (P = 0.311 and P = 0.477, respectively). Analyses of the combined effects between genotypes showed no other significant differences in all phenotypes (P < 0.05) at baseline. However, in response to high-speed power training, a significant interaction on walking speed (P = 0.048) was observed between the “power” (ACTN3 RR + RX & ACE DD) versus “non-power” muscularity-oriented genotypes (ACTN3 XX & ACE II + ID)].

Conclusions

Thus, ACE I/D and ACTN3 R577X polymorphisms are likely candidates in the modulation of exercise-related gait speed phenotype in older women but not a significant influence in mobility traits.

Genetics of muscle strength and power: polygenic profile similarity limits skeletal muscle performance

Environmental and genetic factors influence muscle function, resulting in large variations in phenotype between individuals. Multiple genetic variants (polygenic in nature) are thought to influence exercise-related phenotypes, yet how the relevant polymorphisms combine to influence muscular strength in individuals and populations is unclear. In this analysis, 22 genetic polymorphisms were identified in the literature that have been associated with muscular strength and power phenotypes. Using typical genotype frequencies, the probability of any given individual possessing an "optimal" polygenic profile was calculated as 0.0003% for the world population. Future identification of additional polymorphisms associated with muscular strength phenotypes would most likely reduce that probability even further. To examine the genetic potential for muscular strength within a human population, a "total genotype score" was generated for each individual within a hypothetical population of one million. The population expressed high similarity in polygenic profile with no individual differing by more than seven genotypes from a typical profile. Therefore, skeletal muscle strength potential within humans appears to be limited by polygenic profile similarity. Future research should aim to replicate more genotype-phenotype associations for muscular strength, because only five common genetic polymorphisms identified to date have positive replicated findings.

ACTN3 genotype, athletic status, and life course physical capability: meta-analysis of the published literature and findings from nine studies

The ACTN3 R577X (rs1815739) genotype has been associated with athletic status and muscle phenotypes, although not consistently. Our objective was to conduct a meta-analysis of the published literature on athletic status and investigate its associations with physical capability in several new population-based studies. Relevant data were extracted from studies in the literature, comparing genotype frequencies between controls and sprint/power and endurance athletes. For life course physical capability, data were used from two studies of adolescents and seven studies in the Healthy Ageing across the Life Course (HALCyon) collaborative research program, involving individuals aged between 53 and 90+ years. We found evidence from the published literature to support the hypothesis that in Europeans the RR genotype is more common among sprint/power athletes compared with their controls. There is currently no evidence that the X allele is advantageous to endurance athleticism. We found no association between R577X and grip strength (P = 0.09, n = 7,672 in males; P = 0.90, n = 7,839 in females), standing balance, timed get up and go, or chair rises in our studies of physical capability. The ACTN3 R577X genotype is associated with sprint/power athletic status in Europeans, but does not appear to be associated with objective measures of physical capability in the general population. Hum Mutat 32:1–11, 2011. © 2011 Wiley-Liss, Inc.

Are 'endurance' alleles 'survival' alleles? Insights from the ACTN3 R577X polymorphism

Exercise phenotypes have played a key role for ensuring survival over human evolution. We speculated that some genetic variants that influence exercise phenotypes could be associated with exceptional survival (i.e. reaching ≥100years of age). Owing to its effects on muscle structure/function, a potential candidate is the Arg(R)577Ter(X) polymorphism (rs1815739) in ACTN3, the structural gene encoding the skeletal muscle protein α-actinin-3. We compared the ACTN3 R577X genotype/allele frequencies between the following groups of ethnically-matched (Spanish) individuals: centenarians (cases, n = 64; 57 female; age range: 100–108 years), young healthy controls (n = 283, 67 females, 216 males; 21±2 years), and humans who are at the two end-points of exercise capacity phenotypes, i.e. muscle endurance (50 male professional road cyclists) and muscle power (63 male jumpers/sprinters). Although there were no differences in genotype/allele frequencies between centenarians (RR:28.8%; RX:47.5%; XX:23.7%), and controls (RR:31.8%; RX:49.8%; XX:18.4%) or endurance athletes (RR:28.0%; RX:46%; XX:26.0%), we observed a significantly higher frequency of the X allele (P = 0.019) and XX genotype (P = 0.011) in centenarians compared with power athletes (RR:47.6%; RX:36.5%;XX:15.9%). Notably, the frequency of the null XX (α-actinin-3 deficient) genotype in centenarians was the highest ever reported in non-athletic Caucasian populations. In conclusion, despite there were no significant differences with the younger, control population, overall the ACTN3 genotype of centenarians resembles that of world-class elite endurance athletes and differs from that of elite power athletes. Our preliminary data would suggest a certain ‘survival’ advantage brought about by α-actinin-3 deficiency and the ‘endurance’/oxidative muscle phenotype that is commonly associated with this condition.

Is the ACE I/D polymorphism associated with extreme longevity? A study on a Spanish cohort

The 287 bp Ins(I)/Del(D) polymorphism [rs1799752] in intron 16 of the angiotensin-converting enzyme ( ACE) gene has been associated with extreme longevity (≥ 100 years) in some Caucasian and Asian cohorts, but this finding was not corroborated in other reports. We compared the allelic/genotypic frequency of the ACE I/D polymorphism among centenarians ( N = 64, 100—108 years, 89.1% female) and nonagenarians ( N = 47, 90—97 years, 76.6% female), and a control group of healthy young adults ( n = 434, age 20—40 years, 50% female). All participants were of the same Caucasian (Spanish) descent. The ACE I/D genotype met Hardy—Weinberg expectations in all the cohorts. Allelic and genotypic frequencies did not differ by sex in any of the study groups (all p > 0.2). There were no differences in allelic or genotypic frequencies between groups, for example the frequency of the D allele was 62.3% in controls vs. 65.3% in the elderly (64.8% in centenarians). In summary, the ACE I/D polymorphism is not significantly associated with extreme longevity in the Spanish population. Further research is, however, necessary using other approaches. It also remains to be determined if the interaction of ACE genotypes with some other genetic variants exerts a potential effect on longevity.

Does the ACE I/D polymorphism, alone or in combination with the ACTN3 R577X polymorphism, influence muscle power phenotypes in young, non-athletic adults?

We investigated the association of the angiotensin converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism, alone or in combination with the α-actinin-3 gene (ACTN3) R577X polymorphism, with jumping (vertical squat and counter-movement jump tests) and sprint ability (30 m dash) in non-athletic, healthy young adults [N = 281 (214 male), mean (SD) age 21 (2) years]. We did not observe any effect of the ACE I/D polymorphism on study phenotypes. We repeated the analyses separately in men and women and the results did not materially change. Likewise, the mean estimates of the study phenotypes were similar in subjects with the genotype combinations ACE II + ID and ACTN3 XX or ACE DD and ACTN3 RR + RX. We found no association between the ACE DD and ACTN3 RR + RX genotype combination and performance (≥90th of the sex-specific percentile). In summary, though the ACE I/D polymorphism is a strong candidate to modulate some exercise-related phenotypes or athletic performance status, this polymorphism, alone or in combination with the ACTN3 R577X polymorphism, does not seem to exert a major influence in the muscle 'explosive' power of young healthy adults, as assessed during multi-joint exercise tests.