Association analysis of indel variants and gene expression identifies MDM4 as a novel locus for skeletal muscle hypertrophy and power athlete status

Insertions and deletions (indels) are the second most common type of variation in the human genome. However, limited data on their associations with exercise-related phenotypes have been documented. The aim of the present study was to examine the association between 18,370 indel variants and power athlete status, followed by additional studies in 357,246 individuals. In the discovery phase, the D allele of the MDM4 gene rs35493922 I/D polymorphism was over-represented in power athletes compared with control subjects (P = 7.8 × 10-9) and endurance athletes (P = 0.0012). These findings were replicated in independent cohorts, showing a higher D allele frequency in power athletes compared with control subjects (P = 0.016) and endurance athletes (P = 0.031). Furthermore, the D allele was positively associated (P = 0.0013) with greater fat-free mass in the UK Biobank. MDM4 encodes a protein that inhibits the activity of p53, which induces muscle fibre atrophy. Accordingly, we found that MDM4 expression was significantly higher in the vastus lateralis of power athletes compared with endurance athletes (P = 0.0009) and was positively correlated with the percentage of fast-twitch muscle fibres (P = 0.0062) and the relative area occupied by fast-twitch muscle fibres (P = 0.0086). The association between MDM4 gene expression and an increased proportion of fast-twitch muscle fibres was confirmed in two additional cohorts. Finally, we found that the MDM4 DD genotype was associated with increased MDM4 gene expression in vastus lateralis and greater cross-sectional area of fast-twitch muscle fibres. In conclusion, MDM4 is suggested to be a potential regulator of muscle fibre specification and size, with its indel variant being associated with power athlete status. HIGHLIGHTS: What is the central question of this study? Which indel variants are functional and associated with sport- and exercise-related traits? What is the main finding and its importance? Out of 18,370 tested indels, the MDM4 gene rs35493922 I/D polymorphism was found to be the functional variant (affecting gene expression) and the most significant, with the deletion allele showing associations with power athlete status, fat-free mass and cross-sectional area of fast-twitch muscle fibres. Furthermore, the expression of MDM4 was positively correlated with the percentage of fast-twitch muscle fibres and the relative area occupied by fast-twitch muscle fibres.

Genomic predictors of physical activity and athletic performance

Physical activity and athletic performance are complex phenotypes influenced by environmental and genetic factors. Recent advances in lifestyle and behavioral genomics led to the discovery of dozens of DNA polymorphisms (variants) associated with physical activity and allowed to use them as genetic instruments in Mendelian randomization studies for identifying the causal links between physical activity and health outcomes. On the other hand, exercise and sports genomics studies are focused on the search for genetic variants associated with athlete status, sports injuries and individual responses to training and supplement use. In this review, the findings of studies investigating genetic markers and their associations with physical activity and athlete status are reported. As of the end of September 2023, a total of 149 variants have been associated with various physical activity traits (of which 42 variants are genome-wide significant) and 253 variants have been linked to athlete status (115 endurance-related, 96 power-related, and 42 strength-related).

Genes and Athletic Performance: The 2023 Update

Phenotypes of athletic performance and exercise capacity are complex traits influenced by both genetic and environmental factors. This update on the panel of genetic markers (DNA polymorphisms) associated with athlete status summarises recent advances in sports genomics research, including findings from candidate gene and genome-wide association (GWAS) studies, meta-analyses, and findings involving larger-scale initiatives such as the UK Biobank. As of the end of May 2023, a total of 251 DNA polymorphisms have been associated with athlete status, of which 128 genetic markers were positively associated with athlete status in at least two studies (41 endurance-related, 45 power-related, and 42 strength-related). The most promising genetic markers include the AMPD1 rs17602729 C, CDKN1A rs236448 A, HFE rs1799945 G, MYBPC3 rs1052373 G, NFIA-AS2 rs1572312 C, PPARA rs4253778 G, and PPARGC1A rs8192678 G alleles for endurance; ACTN3 rs1815739 C, AMPD1 rs17602729 C, CDKN1A rs236448 C, CPNE5 rs3213537 G, GALNTL6 rs558129 T, IGF2 rs680 G, IGSF3 rs699785 A, NOS3 rs2070744 T, and TRHR rs7832552 T alleles for power; and ACTN3 rs1815739 C, AR ≥21 CAG repeats, LRPPRC rs10186876 A, MMS22L rs9320823 T, PHACTR1 rs6905419 C, and PPARG rs1801282 G alleles for strength. It should be appreciated, however, that elite performance still cannot be predicted well using only genetic testing.

Variability in oxidative stress-related genes (SOD2, CAT, GPX1, GSTP1, NOS3, NFE2L2, and UCP2) and susceptibility to migraine clinical phenotypes and features

Introduction

Migraine is a complex disorder with genetic and environmental inputs. Cumulative evidence implicates oxidative stress (OS) in migraine pathophysiology while genetic variability may influence an individuals' oxidative/antioxidant capacity. Aim of the current study was to investigate the impact of eight common OS-related genetic variants [rs4880 (SOD2), rs1001179 (CAT), rs1050450 (GPX1), rs1695 (GSTP1), rs1138272 (GSTP1), rs1799983 (NOS3), rs6721961 (NFE2L2), rs660339 (UCP2)] in migraine susceptibility and clinical features in a South-eastern European Caucasian population.

Methods

Genomic DNA samples from 221 unrelated migraineurs and 265 headache-free controls were genotyped for the selected genetic variants using real-time PCR (melting curve analysis).

Results

Although allelic and genotypic frequency distribution analysis did not support an association between migraine susceptibility and the examined variants in the overall population, subgroup analysis indicated significant correlation between NOS3 rs1799983 and migraine susceptibility in males. Furthermore, significant associations of CAT rs1001179 and GPX1 rs1050450 with disease age-at-onset and migraine attack duration, respectively, were revealed. Lastly, variability in the CAT, GSTP1 and UCP2 genes were associated with sleep/weather changes, alcohol consumption and physical exercise, respectively, as migraine triggers.

Discussion

Hence, the current findings possibly indicate an association of OS-related genetic variants with migraine susceptibility and clinical features, further supporting the involvement of OS and genetic susceptibility in migraine.

Advances in sports genomics

Sports genomics is the scientific discipline that focuses on the organization and function of the genome in elite athletes, and aims to develop molecular methods for talent identification, personalized exercise training, nutritional need and prevention of exercise-related diseases. It postulates that both genetic and environmental factors play a key role in athletic performance and related phenotypes. This update on the panel of genetic markers (DNA polymorphisms) associated with athlete status and soft-tissue injuries covers advances in research reported in recent years, including one whole genome sequencing (WGS) and four genome-wide association (GWAS) studies, as well as findings from collaborative projects and meta-analyses. At end of 2020, the total number of DNA polymorphisms associated with athlete status was 220, of which 97 markers have been found significant in at least two studies (35 endurance-related, 24 power-related, and 38 strength-related). Furthermore, 29 genetic markers have been linked to soft-tissue injuries in at least two studies. The most promising genetic markers include HFE rs1799945, MYBPC3 rs1052373, NFIA-AS2 rs1572312, PPARA rs4253778, and PPARGC1A rs8192678 for endurance; ACTN3 rs1815739, AMPD1 rs17602729, CPNE5 rs3213537, CKM rs8111989, and NOS3 rs2070744 for power; LRPPRC rs10186876, MMS22L rs9320823, PHACTR1 rs6905419, and PPARG rs1801282 for strength; and COL1A1 rs1800012, COL5A1 rs12722, COL12A1 rs970547, MMP1 rs1799750, MMP3 rs679620, and TIMP2 rs4789932 for soft-tissue injuries. It should be appreciated, however, that hundreds and even thousands of DNA polymorphisms are needed for the prediction of athletic performance and injury risk.

ACE and ACTN3 Gene Polymorphisms and Genetic Traits of Rowing Athletes in the Northern Han Chinese Population

This investigation aimed to explore the effects of ACE I/D and ACTN3 R577X gene polymorphisms on specific quantitative variables, including height, weight, arm span, biacromial breadth, forced vital capacity (FVC), FVC/weight, maximal oxygen uptake (VO2max), prone bench pull (PBP), loaded barbell squat (LBS), and 3,000-m run, in 243 Chinese rowing athletes. The ACE and ACTN3 genotypes were obtained for each athlete via polymerase chain reaction on saliva samples, and the genotype frequency was analyzed. The ACE genotype frequency of rowing athletes were 45.8% II, 42.2% ID, and 12% DD for males and 33.6% II, 48% ID, and 18.4% DD for females. There were significant differences in weight in male athletes, PBP in female athletes, and ACE genotypes. A linear regression analysis using PBP and LBS as different dependent variables and ACE genotypes as independent variables based on the ACE I allele additive genetic effect showed a statistical significance in female athletes (p < 0.05). There was a significant difference in the distribution of the three genotypes among male athletes (36.7% XX, 38.5% RX, and 24.8% RR, χ2 = 5.191, df = 2, p = 0.022 < 0.05). There were no significant differences in the distribution of the three genotypes among female athletes (23.8% XX, 47.8% RX, 28.4% RR, χ 2 = 0.24, df = 2, p = 0.619 > 0.05). The ACTN3 gene polymorphism of male rowing athletes was dominated by the ACTN3 577X allele. There were significant differences in the χ 2 test between groups of male athletes. The ACTN3 R577 allele was dominant in female athletes. There were significant differences between PBP and FVC/body weight and ACTN3 genotypes in male athletes by ANOVA, respectively (p < 0.05). A linear regression analysis using FVC and FVC/body weight as dependent variables and ACTN3 genotypes as independent variables based on the ACTN3 577X allele recessive genetic effect showed statistical significance in male athletes (p < 0.05). These results suggested that ACE and ACTN3 gene polymorphisms may be used as biomarkers of genetic traits in Chinese rowing athletes.

The ACE and ACTN3 polymorphisms in female soccer athletes

OBJECTS

We investigated the association of ACE I/D and ACTN3 R577X polymorphisms with the performance of Chinese elite female soccer athletes for the first time.

MATERIAL AND METHODS

The genotype distributions of ACE I/D and ACTN3 R577X in the athlete group and the control group of Chinese females were evaluated via PCR and compared. VO2max value was tested as per standard protocol.

RESULTS

Regarding the distribution of ACE polymorphisms, the genotype frequency was indifferent between the athletes (II 40 %, ID 46.7 %, DD 13.3 %) and the controls (II 42 %, ID 48 %, DD 10 %). No difference in the I/D allele frequency was observed between the athlete group and the control group. Regarding the distribution of ACTN3 polymorphisms, the genotype frequency was significantly different between the athletes (XX 0 %, XR 53.3 %, RR 46.7 %) and the controls (XX 16 %, XR 44 %, RR 40 %). The allele frequency was observed no different between the athlete and the control group. The ACE ID and ACTN3 RR genotype combination was associated with higher VO2max values among defenders than among other players. According to VO2max values,The ACE and ACTN3 genotype combinations (II/ID/DD + RR/XR) significantly differed between the athletes and the controls (p < 0.05).

CONCLUSION

These results suggested that the Chinese elite female soccer athletes were more likely to harbor the I allele and the R allele and that the combination of ACE II/ID and ACTN3 RR/XR was a synergetic determinant of the athletic performance of females in soccer.

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).

Polygenic Study of Endurance-Associated Genetic Markers NOS3 (Glu298Asp), BDKRB2 (-9/+9), UCP2 (Ala55Val), AMPD1 (Gln45Ter) and ACE (I/D) in Polish Male Half Marathoners

The purpose of this study was to investigate individually and in combination the association between the ACE (I/D), NOS3 (Glu298Asp), BDKRB2 (-9/+9), UCP2 (Ala55Val) and AMPD1 (Gln45Ter) variants with endurance performance in a large, performance-homogenous cohort of elite Polish half marathoners. The study group consisted of 180 elite half marathoners: 76 with time < 100 minutes and 104 with time > 100 minutes. DNA of the subjects was extracted from buccal cells donated by the runners and genotyping was carried out using an allelic discrimination assay with a C1000 Touch Thermal Cycler (Bio-Rad, Germany) instrument with TaqMan® probes (NOS3, UCP2, and AMPD1) and a T100™ Thermal Cycler (Bio-Rad, Germany) instrument (ACE and BDKRB2). We found that the UCP2 Ala55Val polymorphism was associated with running performance, with the subjects carrying the Val allele being overrepresented in the group of most successful runners (<100 min) compared to the >100 min group (84.2 vs. 55.8%; OR = 4.23, p < 0.0001). Next, to assess the combined impact of 4 gene polymorphisms, all athletes were classified according to the number of 'endurance' alleles (ACE I, NOS3 Glu, BDKRB2 -9, UCP2 Val) they possessed. The proportion of subjects with a high (4-7) number of 'endurance' alleles was greater in the better half marathoners group compared with the >100 min group (73.7 vs. 51.9%; OR = 2.6, p = 0.0034). These data suggest that the likelihood of becoming an elite half marathoner partly depends on the carriage of a high number of endurance-related alleles.

Angiotensin-converting enzyme (ACE-I/D) polymorphism frequency in Brazilian soccer players

This study aimed to analyze the angiotensin-converting enzyme (ACE-I/D) allelic and genotypic frequencies in Brazilian soccer players of different ages. The study group comprised 353 players from first-division clubs in the under (U)-14, U-15, U-17, U-20, and professional categories. The allelic and genotypic frequencies did not differ significantly in any of the categories between the group of players and the control group. This was the first study of ACE-I/D polymorphism in Brazilian soccer players.

Genetic polymorphisms to predict gains in maximal O2 uptake and knee peak torque after a high intensity training program in humans

PURPOSE

The study aimed to identify single nucleotide polymorphisms (SNPs) that significantly influenced the level of improvement of two kinds of training responses, including maximal O2 uptake (V'O2max) and knee peak torque of healthy adults participating in the high intensity training (HIT) program. The study also aimed to use these SNPs to develop prediction models for individual training responses.

METHODS

79 Healthy volunteers participated in the HIT program. A genome-wide association study, based on 2,391,739 SNPs, was performed to identify SNPs that were significantly associated with gains in V'O2max and knee peak torque, following 9 weeks of the HIT program. To predict two training responses, two independent SNPs sets were determined using linear regression and iterative binary logistic regression analysis. False discovery rate analysis and permutation tests were performed to avoid false-positive findings.

RESULTS

To predict gains in V'O2max, 7 SNPs were identified. These SNPs accounted for 26.0 % of the variance in the increment of V'O2max, and discriminated the subjects into three subgroups, non-responders, medium responders, and high responders, with prediction accuracy of 86.1 %. For the knee peak torque, 6 SNPs were identified, and accounted for 27.5 % of the variance in the increment of knee peak torque. The prediction accuracy discriminating the subjects into the three subgroups was estimated as 77.2 %.

CONCLUSIONS

Novel SNPs found in this study could explain, and predict inter-individual variability in gains of V'O2max, and knee peak torque. Furthermore, with these genetic markers, a methodology suggested in this study provides a sound approach for the personalized training program.

Current Progress in Sports Genomics

Understanding the genetic architecture of athletic performance is an important step in the development of methods for talent identification in sport. Research concerned with molecular predictors has highlighted a number of potentially important DNA polymorphisms contributing to predisposition to success in certain types of sport. This review summarizes the evidence and mechanistic insights on the associations between DNA polymorphisms and athletic performance. A literature search (period: 1997-2014) revealed that at least 120 genetic markers are linked to elite athlete status (77 endurance-related genetic markers and 43 power/strength-related genetic markers). Notably, 11 (9%) of these genetic markers (endurance markers: ACE I, ACTN3 577X, PPARA rs4253778 G, PPARGC1A Gly482; power/strength markers: ACE D, ACTN3 Arg577, AMPD1 Gln12, HIF1A 582Ser, MTHFR rs1801131 C, NOS3 rs2070744 T, PPARG 12Ala) have shown positive associations with athlete status in three or more studies, and six markers (CREM rs1531550 A, DMD rs939787 T, GALNT13 rs10196189 G, NFIA-AS1 rs1572312 C, RBFOX1 rs7191721 G, TSHR rs7144481 C) were identified after performing genome-wide association studies (GWAS) of African-American, Jamaican, Japanese, and Russian athletes. On the other hand, the significance of 29 (24%) markers was not replicated in at least one study. Future research including multicenter GWAS, whole-genome sequencing, epigenetic, transcriptomic, proteomic, and metabolomic profiling and performing meta-analyses in large cohorts of athletes is needed before these findings can be extended to practice in sport.

Variation in the ACE, PPARGC1A and PPARA genes in Lithuanian football players

The aim of this study was to determine the impact of ACE (I/D), PPARGC1A (G/A) and PPARA (G/C) polymorphisms on footballers performance among 199 Lithuanian professional footballers and 167 sedentary, healthy men (controls). Genotyping was performed using polymerase chain reaction and restriction fragment length polymorphism methods on DNA from leucocytes. Results revealed that the angiotensin-1-coverting enzyme gene (ACE) genotype distribution was significantly different between total football players group (II 23.6%, ID 46.7% and DD 29.6%) and the controls (II 24.6%, ID 29.9% and DD 45.5%; P=0.002). Although investigating PPARGC1A (G/A) and PPARA (G/C) polymorphisms no significant results were obtained in the total football players group, however, significant differences were determined between forwards and controls [PPARGC1A: GG 54.6%, GA 29.5%, AA 15.9% vs. GG 49.7%, GA 44.3% and AA 6.0% (P = 0.044); PPARA: GG 52.3%, GC 40.9%, CC 6.8% vs. GG 72.4%, GC 24.6% and CC 3.0% (P = 0.034)]. In the whole cohort, the odds ratio of the genotype [ACE ID + PPARA GG] being a footballer was 1.69 (95% CI 1.04-2.74), and of [ACE ID + PPARGC1A GG] 1.93 (95% CI 1.10-3.37) and of [ACE II + PPARA GC] 2.83 (95% CI 1.02-7.91) compared to controls. It was revealed that ACE ID genotype together with PPARA GG and PPARGC1A GG as well as ACE II genotype with PPARA GC is probably the 'preferable genotype' for footballers. Summing up, the present study suggests that the ACE, PPARGC1A and PPARA polymorphisms genotypes are associated, separately and in combination, with Lithuanian footballers' performance.

Gene polymorphisms and sport attitude in Italian athletes

AIM

The aim of this study was to evaluate whether the distribution of polymorphisms in the ACE, ACTN3, NOS3, UCP2, and UCP3 genes, which has been reported to be correlated with different physiological parameters, played a role in sport performance. We focused on a cohort of 82 Italian athletes: first of all, athletes were divided according to type of sport: team (n=72) versus individual (n=10), and subsequently, according to the performance, into "power" sports (n=29; sprinters, short distance swimmers, and volleyball players) and "intermittent" sports (n=53; football, basketball, and hockey players).

RESULTS

All the populations studied were in Hardy-Weinberg equilibrium for the following polymorphisms: ACE (I/D), ACTN3 (R577X), NOS3 (-786 T/C), UCP2 (A55V), and UCP3 (-55 C/T). We observed that the frequency of NOS3-786 T and UCP2 C alleles was higher among power athletes compared with controls (p=0.011 and p=0.012, respectively); these alleles were also overrepresented in individual athletes (p=0.02 and p=0.045, respectively), although a small sample was analyzed. The frequency of NOS3 298G allele was higher among power athletes compared with controls (p=0.015); these data remained suggestive after correction for multiple testing.

CONCLUSION

We found a suggestive association between NOS3 (-786 T/C; G298A) and UCP2 (A55V) polymorphisms and power athletes, whereas no significant correlation was found with UCP3 (-55C/T), ACE (I/D), and ACTN3 (R577X) polymorphisms, in contrast to previous studies. Analysis of multiple performance-associated genetic polymorphisms needs further examination to explain the relationship between genetic background and potential success in sport performance.