ACTN3 Research Articles

Effect of ACTN3 R577X Genotype on Injury Epidemiology in Elite Endurance Runners.

The p.R577X polymorphism (rs1815739) in the ACTN3 gene causes individuals with the ACTN3 XX genotype to be deficient in functional α-actinin-3. Previous investigations have found that XX athletes are more prone to suffer non-contact muscle injuries. This investigation aimed to determine the influence of the ACTN3 R577X polymorphism in the injury epidemiology of elite endurance athletes. Using a cross-sectional experiment, the epidemiology of running-related injuries was recorded for one season in a group of 89 Spanish elite endurance runners. ACTN3 R577X genotype was obtained for each athlete using genomic DNA samples. From the study sample, 42.7% of athletes had the RR genotype, 39.3% had the RX genotype, and 18.0% had the XX genotype. A total of 96 injuries were recorded in 57 athletes. Injury incidence was higher in RR runners (3.2 injuries/1000 h of running) than in RX (2.0 injuries/1000 h) and XX (2.2 injuries/1000 h; p = 0.030) runners. RR runners had a higher proportion of injuries located in the Achilles tendon, RX runners had a higher proportion of injuries located in the knee, and XX runners had a higher proportion of injuries located in the groin (p = 0.025). The ACTN3 genotype did not affect the mode of onset, the severity, or the type of injury. The ACTN3 genotype slightly affected the injury epidemiology of elite endurance athletes with a higher injury rate in RR athletes and differences in injury location. However, elite ACTN3 XX endurance runners were not more prone to muscle-type injuries.

The influence of the ACTN3 R577X polymorphism in the responsiveness to post-activation jump performance enhancement in untrained young men

ABSTRACT We aimed to investigate the influence of alpha-actinin-3 (ACTN3) R577X polymorphism on responsiveness to post-activation performance enhancement (PAPE) of countermovement jumps (CMJ) in untrained subjects. Sixteen untrained men were allocated into two groups according to their ACTN3 gene alleles: homozygous for the X allele (XX, n = 9) or homozygous for the R allele (RR, n = 7). CMJ height, mean power output and vertical force were determined twice (CMJ1 and CMJ2) in two conditions: control (CON) and potentiated (PAPE). In the CON condition, CMJ were performed before and after a 15-min rest. In the PAPE condition, CMJ were performed 15 min before and 4 min following five squats with a 5-repetition maximum (5RM) load. Different conditions were applied on separate days in a randomized order. Statistical analysis involved three-way ANOVAs to compare the differences between conditions (CON and PAPE), time (CMJ1 and CMJ2), and groups (XX and RR). Significance level considered was p < 0.05. Effect sizes were calculated as Cohen’s d. The effect sizes for changes in CMJ height for CON and following pre-activation for PAPE were 0.04 and 0.08, respectively. No significant differences were found for CMJ height between XX and RR at baseline (1.07 ± 2.54 cm e -0.82 ± 2.56 cm, respectively). No differences were found (p>0.05) in responsiveness to PAPE between the groups (XX = -0.20 ± 1.6 cm and RR = -0.81 ± 2.7 cm). We conclude that ACTN3 gene polymorphisms does not influence responsiveness to PAPE.

Effect of ACTN3 gene polymorphism on the pathogenic phenotype of related diseases and its treatment prospect

Effect of ACTN3 gene polymorphism on the pathogenic phenotype of related diseases and its treatment prospect

Genetic polymorphisms associated with high-altitude adaptation in a Baltí population

Genetic variants may play a crucial role in human adaptation to demanding environmental conditions, i.e. high altitude. Our aim was to analyze the genotypic and allelic distribution of four genetic polymorphisms in UCP2, HIF1A, BDNF and ACTN3·genes in 40 individuals from Hushé village, Pakistán, living at higher than 3400 m above sea level and 45 individuals from the Autonomous Community of Madrid, Spain, living at almost 700 m above sea level. There were no differences in the UCP2 polymorphism rs660339. The frequency distribution of the T allele in the rs11549465 polymorphism in HIF1A gene was higher in the Madrid population (14.4%) than in those from Hushé village (3.7%). Analysis of the rs1815739 polymorphism in ACTN3 gene showed statistical differences, being the CT and TT genotypes more frequent in Madrid than in Hushé village individuals. People from Hushé village showed a significant lower frequency of the T allele in the rs6265 BDNF gene polymorphism than people from Madrid. Hushé's women more frequently showed the CC genotype for rs11549465 (HIF1A) and for rs1815739 (ACTN3) as compared with women from Madrid. As conclusion, the genetic variants located in BDNF, HIF1A and ACTN3 genes coding for proteins involved in motor skill acquisition, hypoxic adaptation and muscle power, which may play a potential role in high-altitude adaptation in the Hushé village population, particularly in women.

R577X OF THE ACTN3 GENE AS PREDICTOR OF PHYSICAL PERFORMANCE IN ULTRAMARATHON RUNNERS

ABSTRACT Introduction: Genetic factors appear to explain why some athletes perform better in competition and training than their peers. Objective: To determine the occurrence of R577X polymorphism of the ACTN3 gene in mountain runners. Methods: The sample consisted of 19 female mountain runners with a mean age of 41.2 ± 6.1 years. Genotyping of R577X polymorphism of the ACTN3 gene was performed by the polymerase chain reaction (PCR) method with DNA extracted from saliva. The genotypic and allelic frequencies of the athletes were evaluated and compared with data from the literature. Hardy-Weinberg equilibrium and Chi-square with Yates correction were used, with a significance level of p<0.05. Results: The genotypic distributions did not show any significant differences between the athletes and the control group, with RR = 15.8%, RX = 57.9%, XX = 26.3%. In regard to allelic distribution, the nonfunctional allele was higher in the study group than in the control group, with R = 44.7%, X = 55.3% for p = 0.0350. Conclusion: The data revealed a possible relationship between the ACTN3 X allele and athletic performance in Brazilian female mountain runners. Level of evidence II; Development of diagnostic criteria in consecutive patients (with “gold” reference standard applied).

The study of the prevalence and impact of polymorphism of the C/Т gene ACTN3 (RS1815739) in the physical development of children born with low birth weight

The work aims at studying the prevalence and influence of polymorphism of the C/T gene polymorphism of ACTN3 gene (rs1815739) on the physical development of children born with low body weight.Materials and methods of research. To study the C/T polymorphism of the ACTN3 gene (rs1815739), 170 newborns were examined. Newborns were divided into 4 groups depending on birth weight: Group I - 50 premature babies weighing 1500-1999 grams (1776.26 ±20.06 grams), Group II - 64 premature babies with birth weight 2000-2499 grams (2225.31±19.46 grams), group III - 25 children with normal gestational age at birth, but with intrauterine growth retardation (2105.00±56,41), group IV (control group) - 31 children with normal gestational age and birth weight more than2500 grams (3009.03±73.04 grams). Genotyping was performed by polymerase chain reaction according to the instructions (Applied Biosystems, USA) using total DNA samples isolated from whole venous blood using a set of reagents "SNP-Screen" (manufactured by "Syntol") on the CFXteTM Real-Time PCR amplifier (Bio-Rad Laboratories, Inc., USA).Results. In all studied children, the frequency of detection of C allele polymorphism of the C / T gene polymorphism of the ACTN3 gene (rs1815739) was 51.47%, T allele - 48.52%., The frequency of genotypes had the following distribution: CC-30.59%, TT- 26.65%, CT-41.76%. In this case, in group I was the following distribution of alleles and genotypes: alleles C and T were detected in the ratio of 46.67% to 53.93%, genotypes SS-32.00%, TT-28.00%, ST-40, 00%, in group II alleles - C-51,56%, T - 48,44%, genotypes - СС 28,13%, TT-25,00%, СT - 46,88%, in group III - allele C was significantly more often registered than T (68.00% vs. 32.00%, p <0.05) and genotype TT - more often than CC and CT (52.00% vs. 16.00% and 32.00%). In IV (control) group there was the following distribution of the frequency of alleles and genotypes of gene polymorphism: allele C - 40.00%, allele T - 60.00%, genotype CC - 38.71%, genotype TT - 19.35%, genotype CT -41.93%. The lowest monthly values of body weight and weight gain were associated with the TT genotype of the ACTN3 gene (rs1815739) in preterm infants and children with normal gestational age at birth, but with intrauterine growth retardation in the first half, and among children in the comparison group - in the second half, but the overall weight gain for 12 months had no genotypic dependence. Premature infants (observation groups I and II) with the TT genotype of the ACTN3 gene (rs1815739) had unevenly lower body lengths during the first year of life, while children with normal gestational age at birth, but with intrauterine growth retardation lagged behind in their growth in the first year, and children from the control group - in the second half. The total annual increase in body length for the first year of life in all children with the TT genotype was the lowest and amounted to in the first group - 28.50 ±1.03 cm, in the second - 24.03 ±0.93 cm, in the third - 25.50 ±1.04 cm, in IV - 23.00 ±0.98 cm. A probable positive correlation was found between the duration of breastfeeding and the monthly increase in body length in children with the TT genotype of the ACTN3 gene (rs1815739): γ = 0.58, γ = 0.76, γ = 0.61 from the I, II and III observation groups, respectively.Conclusions. It was found that the TT genotype of the ACTN3 gene (rs1815739) in children is associated with their uneven physical development in the first year of life and significantly lower rates of body length gain in 12 months, and long-term breastfeeding, especially premature babies and children with delayed fetal development, their normal growth.

Combination of ACTN3 R577X and ACE I/D polymorphisms as a tool for prediction of obesity risk in children.

The genetic influence in obesity prevalence is well described, but the role of genetic markers related to athletic strength/ endurance performance remains controversial. We investigated associations between obesity and the genetic polymorphisms alpha-actinin-3 (ACTN3) R577X and angiotensin-converting enzyme (ACE) I/D in schoolchildren aged 4-13 years from Southern Brazil. We collected sociodemographic data from parents through a questionnaire and conducted an anthropometric assessment. DNA was extracted from buccal cells and genotyping was performed by PCR. We found that 1.9% of the individuals were classified as low weight-for-age, 57.6% as normal weight and 40.5% as overweight/ obesity. Regarding allelic distribution, we found that 52.5% of individuals were DD, 30.8% ID, and 16.7% II for ACE; and 38.8% of individuals were RR, 40.2% RX and 21.0% XX for ACTN3. When both polymorphisms were combined, we observed a clear association between the composed genetic profile of these alleles and severe obesity in schoolchildren. Our data suggest that the combined analysis of ACTN3 R577X and ACE I/D polymorphisms may serve as a predictor for the risk of severe obesity in children. These data can contribute to a better understanding of the relationship between these polymorphisms and the body weight development of school-age children.

Genetics of Muscle Stiffness, Muscle Elasticity and Explosive Strength.

Muscle stiffness, muscle elasticity and explosive strength are the main components of athletes’ performance and they show a sex-based as well as ethnicity variation. Muscle stiffness is thought to be one of the risk factors associated with sports injuries and is less common in females than in males. These observations may be explained by circulating levels of sex hormones and their specific receptors. It has been shown that higher levels of estrogen are associated with lower muscle stiffness responsible for suppression of collagen synthesis. It is thought that these properties, at least in part, depend on genetic factors. Particularly, the gene encoding estrogen receptor 1 (ESR1) is one of the candidates that may be associated with muscle stiffness. Muscle elasticity increases with aging and there is evidence suggesting that titin (encoded by the TTN gene), a protein that is expressed in cardiac and skeletal muscles, is one of the factors responsible for elastic properties of the muscles. Mutations in the TTN gene result in some types of muscular dystrophy or cardiomyopathy. In this context, TTN may be regarded as a promising candidate for studying the elastic properties of muscles in athletes. The physiological background of explosive strength depends not only on the muscle architecture and muscle fiber composition, but also on the central nervous system and functionality of neuromuscular units. These properties are, at least partly, genetically determined. In this context, the ACTN3 gene code for α-actinin 3 has been widely researched.

The ACTN3 577XX Null Genotype Is Associated with Low Left Ventricular Dilation-Free Survival Rate in Patients with Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a fatal progressive muscle-wasting disease caused by mutations in the DMD gene. Dilated cardiomyopathy is the leading cause of death in DMD; therefore, further understanding of this complication is essential to reduce morbidity and mortality. A common null variant (R577X) in the ACTN3 gene, which encodes α-actinin-3, has been studied in association with muscle function in healthy individuals; however it has not yet been examined in relationship to the cardiac phenotype in DMD. In this study, we determined the ACTN3 genotype in 163 patients with DMD and examined the correlation between ACTN3 genotypes and echocardiographic findings in 77 of the 163 patients. The genotypes 577RR(RR), 577RX(RX) and 577XX(XX) were identified in 13 (17%), 44 (57%) and 20 (26%) of 77 patients, respectively. We estimated cardiac involvement-free survival rate analyses using Kaplan-Meier curves. Remarkably, the left ventricular dilation (> 55 mm)-free survival rate was significantly lower in patients with the XX null genotype (P < 0.01). The XX null genotype showed a higher risk for LV dilation (hazard ratio 9.04). This study revealed that the ACTN3 XX null genotype was associated with a lower left ventricular dilation-free survival rate in patients with DMD. These results suggest that the ACTN3 genotype should be determined at the time of diagnosis of DMD to improve patients' cardiac outcomes.

Frequency analysis of the ACTN3 gene polymorphism in children with isolated or combined orthodontic pathology with allergic rhinitis

Purpose. Determination and frequency analysis of the ACTN3 gene (actinin, alpha 3) rs1815739 polymorphism, responsible for metabolism, strength and speed of muscle movement, including the maxillofacial apparatus, in children with distal occlusion and allergic rhinitis.Materials and Methods. To study the ACTN3 gene (rs1815739) polymorphism, the molecular and genetic study was conducted in 100 children aged 6 to 18 years. The 26 patients with distal bite and allergic rhinitis were included in the first study group; the second group consisted of 23 children with a distal bite; the third group included 30 children with allergic rhinitis and the fourth group was made up of 21 almost healthy children. All children did not have a statistically significant difference in sex and age. The molecular and genetic study was carried out in the Department of Molecular and Genetic Research of theTrainingMedicalLaboratoryCenter in the Department of Microbiology of theZaporizhiaStateMedicalUniversity, Zaporizhia. The obtained study results were analyzed using non-parametric methods of statistical analysis of the licensed software package «Statistica 6.1. RU». The population genetic analysis with the distribution of alleles and genotypes of the ACTN3 gene frequency is presented in accordance with the Hardy-Weinberg principle.Results. Studying the distribution of allelic genes and genotypes of the ACN3 polymorphism (actinin, alpha 3) rs1815739 showed that among all examined children, the alpha actinin-3 protein was synthesized sufficiently in 36% of children with the homozygous C / C genotype, while in case of European population it was equal to 31%; and insufficiently - in 11% of those examined with the homozygous T / T genotype (in the European population - in 17.9%); in a smaller amount - in 53% of children with the heterozygous C / T genotype, which frequency corresponded to the European population (51.1%). The genotypes had the following distribution in the study groups: in children with a combination of allergic and orthodontic pathology; with distal bite; with allergic rhinitis and in healthy children, respectively: homozygous C / C genotype - 38.46%; 56.52%; 33.33%; 14.3%; homozygous T / T genotype - 11.5%; 8.7%; 6.67%; 19.05%; heterozygous C / T genotype – 50%; 34.78%; 60%; 66.67%. In children with distal bite, the homozygous C / C genotype (rs1815739) of the gene coding alpha-actinin-3 protein synthesis was associated with the odds ratio OR = 7.80, CI [1.79 - 34.07], while in children with heterozygous genotype C / T the odds of being healthy was OR = 3.75, СІ [1.08 – 13.07].Conclusions. The dominant observation of the C / C genotype (rs1815739) of the gene coding alpha-actinin-3 protein synthesis in children with distal bite may indicate the role of muscle strength and their pressure on the dentition in the process of formation of children tooth-maxillary anomalies, which shall be taken into account when selecting individual treatment-and-preventive myogymnastics and apparatus treatment for such patients.

Frequency analysis of the ACTN3 gene polymorphism in children with isolated or combined orthodontic pathology with allergic rhinitis

Frequency analysis of the ACTN3 gene polymorphism in children with isolated or combined orthodontic pathology with allergic rhinitis

ACTN3’s R577X Single Nucleotide Polymorphism Allele Distribution Differs Significantly in Professional Football Players according to Their Field Position

Introduction: Football is characterised by intermittent high-intensity efforts varying according to the field position of a player. We aimed to ascertain whether polymorphisms in the ACTN3 gene are associated with different playing positions in elite professional football players. Subjects and Methods: Genotyping of the ACTN3 gene was conducted in 43 elite professional football players of a single team. Playing position was recorded based on the player’s most frequent position. Results: The genotype distribution was not significant between positions (p = 0.057), while the allele distribution differed significantly (p = 0.035). Goalkeepers (p = 0.04, p = 0.03), central defenders (p = 0.03, p = 0.01), and central midfielders (p = 0.01, p = 0.00) had a significantly different allele distribution compared with wide midfielders and forward players. Conclusions: Genetic biomarkers may be important when analysing performance capability in elite professional football. Identifying the genetic characteristics of a player to adapt his playing position may lead to orientation of positions based on physical capabilities and tissue quality in young football players, and also to performance enhancement in those who are already playing in professional teams.

Wild or farmed? A pilot study on determining origin of wildlife meat using methylation rate of ACTN3 gene and American mink

Commercial farming of endangered wildlife has potential to reduce poaching pressure on wild populations. However, poached products can be laundered as farmed products. A method for separating farmed from wild products is therefore essential for effective law enforcement. Meat (skeletal muscle) is a wildlife product whose origin cannot be correctly determined. This short communication reports an epigenetic approach to achieve the distinction using the methylation rate of the promoter of the α-actinin-3 (ACTN3) gene in gluteus maximus tissues of feral (n = 21) and farmed (n = 21) American mink, Neovison vison. Our results showed that the accuracy of assignment ranged from 59.5 to 76.2% on each of six CpG sites/site groups. Combination of the six CpG sites/site groups achieved 83.3% overall correct assignment, 90.5% for the farmed group and 76.2% for the wild group. These data suggest the methylation rate of promoters of selected genes could be an effective indicator to distinguish farmed meat from wild meat of wildlife species.

Молекулярно-генетический анализ генов ACTN3 и AMPD1 у дзюдоистов спортивной школы по самбо и дзюдо «Витязь» г. Перми

The analysis of ACTN3 and AMPD1 genes polymorphisms associated with the development of speed-strength qualities for judo athletes was carried out. Overall, 71 judokas of the sambo and judo sports school “Vityaz” in Perm were tested. The heterozygous R/X genotype of the ACTN3 gene prevails with a frequency of 0.9 in the studied group. The carriers of this genotype are characterized by the average functional activity of α-actin-3. The most favorable homozygous R/R genotype, associated with the high functional activity of α-actin-3, is significantly less common (frequency of 0.1). Homozygous X/X genotype was not found in the surveyed sample. The AMPD1 gene polymorphism analysis revealed that the homozygous C/C genotype prevails with a frequency of 0,83. The genotype is favorable for the development of speed-strength qualities of athletes. The C/T heterozygous genotype occurs with a frequency of 0,17. The T/T genotype was not identified in the studied selection. Allelic variants of the ACTN3 and AMPD1 genes were analyzed in two groups of judokas with high and low qualifications A comprehensive research data analysis showed that athletes with the ACTN3 R/R and AMPD1 C/C genotypes are able to achieve outstanding sports success and sports-life longevity. These genotypes can be used as markers for determining the development of physical qualities when choosing sports specialization. Moreover, they could be helpful in predicting performance, as well as in regulating loads during training. Individual reports were compiled, trainers and athletes were given recommendations on the correction of the training process, taking into account the genetic profiles of examined athletes.

Association Between rs1815739 Polymorphism of ACTN3 Gene and Athletic Ability in Chinese Sprinters

The aim of this study was to investigate the prevalence of the ACTN3 rs1815739 polymorphism and to study its association with athletes’ level of competition and lower-extremity power. Time-of-flight mass spectrometry (TOFMS) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques were employed to identify the ACTN3 rs1815739 genotypes and allele frequencies in 108 elite sprinters and 206 untrained controls. Questionnaires were then used to assess subjects’ 100 m sprint, standing jump (SJ) and standing triple jump (STJ) personal best record. (1) The RR, RX and XX genotype distribution of the ACTN3 rs1815739 polymorphism is 42.6%, 49.1%, 8.3%, respectively. R and X alleles frequency is 67.1% and 32.9%, respectively, which comply with Hardy Weinberg equilibrium (HWE) through Chi-square (χ2) tests (χ2 = 0.661; df = 2; P = 0.718). (2) Significant differences were found in R allele frequency between the elite sprinter group and controls. (3) The athletes’ 100 m sprint, SJ, and STJ personal best records were better in those with RR and RX than XX genotype. A significant association was observed between the R alleles and 100 m sprint, SJ, and STJ results of male and female athletes. The present results indicate that ACTN3 rs1815739 polymorphism has a significant association with speed and lower-extremity power in sprint/power athletes.

Genetics and the Elite Athlete: Our Understanding in 2020.

Modern competitive sport has evolved so much that athletes would go to great extremes to develop themselves into champions; medicine has also evolved to the point that many genetic elements have been identified to be associated with specific athletic traits, and genetic alterations are also possible. The current review examines the published literature and looks at three important factors: genetic polymorphism influencing sporting ability, gene doping and genetic tendency to injury. The ACTN3 gene has an influence on type II muscle fibres, with the R allele being advantageous to power sports like sprinting and the XX genotype being associated with lower muscle strength and sprinting ability. The ACE gene polymorphisms are associated with cardio-respiratory efficiency and could influence endurance athletes. Many other genes are being looked at, with specific focus on those that are potentially related to enhancement of athletic ability. Recognition of these specific gene polymorphisms brings into play the concept of genetic engineering in athletes, which constitutes gene doping and is outlawed. This has the potential to develop into the next big threat in elite sports; gene doping could have dangerous and even fatal outcomes, as the knowledge of gene therapy is still in its infancy. Genetic predisposition to injury is also being identified; recent publications have increased the awareness of gene polymorphisms predisposing to injuries of ligaments and tendons due to influence on collagen structure and extracellular matrix. Ongoing work is looking at identifying the same genes from different races and different sexes to see if there are quantitative racial or sexual differences. All of the above have led to serious ethical concerns; in the twenty-first century some sports associations and some countries are looking at genetic testing for their players. Unfortunately, the science is still developing, and the experience of its application is limited worldwide. Nevertheless, this field has caught the imagination of both the public and the sportsperson, and hence the concerned doctors should be aware of the potential problems and current issues involved in understanding genetic traits and polymorphisms, genetic testing and genetic engineering.

A statistical model for ACTN3 genotype in elite power and speed athletes

The presence of R allele in R577X polymorphism of ACTN3 gene is responsible for expression of α-actinin-3 protein in fast glycolytic muscle fiber with a key role in structure and metabolism. The ACTN3 R577X gene polymorphism was found to be associated with strength and power performance. The aim of this study was to investigate the association between the ACTN3 R577X polymorphism and elite power/speed performance and to determine its relationship to the power/speed athletic status (elite athlete and nonathlete) in 48 subjects (23 power/speed athletes and 25 nonathletes) from Indian cohort. The association analysis did not show any significant association when conducted for all genotypes (RR vs RX vs XX) in athletes and nonathletes (p > 0.05). The association of R allele dominant (RR+XX) model and X allele dominant (RX+XX) model was also not significant (p > 0.05) when compared for athletic and nonathletic status, however, the frequency of RR genotype was higher in athletes than in nonathletes. The odds of becoming power/speed athlete with the possession of RR genotype and R allele carriage (RR+RX) was higher, although the prediction was not significant (p > 0.05). It can be inferred on the basis of selected samples that the possession of RR genotype or R allele does not provide any significant advantage for being power/speed athlete.

ACTN3 (R577X) Genotype Is Associated With Australian Football League Players.

Jacob, Y, Hart, NH, Cochrane, JL, Spiteri, T, Laws, SM, Jones, A, Rogalski, B, Kenna, J, and Anderton, RS. ACTN3 (R577X) genotype is associated with Australian Football League players. J Strength Cond Res 36(2): 573-576, 2022-Genetic variants in the angiotensin-converting enzyme (ACE) and alpha actinin-3 (ACTN3) genes have been associated with elite sport athletic performance. This study aimed to investigate the frequency of each polymorphism in a cohort of elite Australian football (AF) players. To achieve this, 47 players from an Australian Football League (AFL) club and 59 healthy age matched controls with no history of elite sporting competition were recruited for this study. Each subject provided saliva samples through buccal swab for DNA extraction and genotyping, with group comparisons made using χ2 and odds ratio analysis. There was no significant difference in ACE I/D genotype between healthy control and elite AF players. The ACTN3 XX genotype was significantly underrepresented in AFL players (4.3%) compared with healthy controls (28.8%, p = 0.003). In addition, there was a greater representation of the R allele in elite AF players (70.2%) when compared with healthy controls (50%; χ2 = 8.834, p = 0.002). This is the first study to investigate genetic variants in elite AF players, with results suggesting that the ACTN3 gene may play a significant role explaining aspects of athletic performance in AF.

Influence of the ACTN3 R577X genotype on the injury epidemiology of marathon runners.

A common single nucleotide polymorphism in the ACTN3 gene might result in the complete deficiency of α-actinin-3 (i.e., XX genotype). It has been found that ACTN3 XX individuals have several traits related to lessened muscle performance. This study aimed to determine the influence, if any, of ACTN3 genotypes on injury incidence of marathoners during the year preceding to participating in a competitive marathon race. Using a cross-sectional experimental design, the type and conditions of sports injuries were documented for one year in a group of 139 marathoners. Injuries were recorded following a consensus statement on injuries in Athletics. Afterward, ACTN3 genotyping was performed, and injury epidemiology was compared among RR, RX, and XX genotypes. The distribution of the RR/RX/XX genotypes was 28.8/42.8/23.5%, respectively. A total of 67 injuries were recorded. The frequency of marathoners that reported any injury during the previous year was not different across the genotypes (55.0/38.8/40.6%, P = 0.241). Although the overall injury incidence was not different among genotypes (2.78/1.65/1.94 injuries/1000 h of running, P = 0.084), the likelihood of suffering an injury was higher in RR than in RX (OR = 1.93: 95%CI = 0.87–4.30), and higher than in XX (OR = 1.79: 0.70–4.58). There was no difference in the conditions, severity, body location, time of year, or leading cause of injury among genotypes. However, XX presented a higher frequency of sudden-onset injuries (P = 0.024), and the OR for muscle-type injuries was 2.0 (0.51–7.79) times higher compared to RR runners. Although XX marathoners did not have a higher overall incidence of injury, the OR in these runners for muscle-type injuries was superior to RR and RX runners. The likelihood of suffering a muscle injury, especially with a sudden-onset, was twice in XX than in RR endurance runners.

&amp;lt;I&amp;gt;ACTN3&amp;lt;/I&amp;gt; R577X Polymorphism Impacts Glucose Consumption at Simulated High Altitude

Introduction: High altitude acclimatization is a process that involve several physiological adjustments, which may increase glucose metabolism because of acute hypoxic exposure. Native highlanders like Tibetans show an increased anaerobic glucose metabolism and a higher proportion of type I muscle fiber than lowlanders. Actin filaments are anchored to the Z line of the sarcomere by a protein called alpha-actinin that exist in two isoforms in the muscle (ACTN2 and ACTN3), however ACTN3 is present only in type II fibers, especially in type IIx. Homozygous individuals for a 577X polymorphism in the ACTN3 gene do not express ACTN3 and seem to be more type I muscle fiber than homozygous individuals 577R. The aim of this study was to compare the glucose consumption response of individuals with different ACTN3 genotypes at simulated 4,500 m altitude. Materials & Methods: Twenty-three volunteers spent four hours exposed to a simulated altitude of 4,500 m inside a normobaric hypoxia chamber. Lactate and glucose concentrations, SpO2 and heart rate were analyzed immediately before entering the chamber and at each hour during the exposure. Results: Glucose after four hours of exposure to hypoxia was different between groups, with RX (68.1 ± 11.7 mg/dl) and RR (71.7 ± 14.4 mg/dl) showing a decreased blood glucose compared to XX (88.7 ± 14.1 mg/dl), indicating an increased dependence on glucose metabolism in individuals with at least one R allele after exposure at 4,500 m simulated altitude. Conclusions: We concluded that individuals with at least one R allele of the ACTN3 R577X gene polymorphism consume more glucose than the ones with XX genotype.