The association between COMT rs4680 and 5-HTTLPR genotypes and concussion history in South African rugby union players

Concussion-Associated Gene Variant COMT rs4680 Is Associated With Elite Rugby Athlete Status

OBJECTIVE

Concussions are common match injuries in elite rugby, and reports exist of reduced cognitive function and long-term health consequences that can interrupt or end a playing career and produce continued ill health. The aim of this study was to investigate the association between elite rugby status and 8 concussion-associated risk polymorphisms. We hypothesized that concussion-associated risk genotypes and alleles would be underrepresented in elite rugby athletes compared with nonathletes.

DESIGN

A case-control genetic association study.

SETTING

Institutional (university).

PARTICIPANTS

Elite White male rugby athletes [n = 668, mean (SD) height 1.85 (0.07) m, mass 102 (12) kg, and age 29 (7) years] and 1015 nonathlete White men and women (48% men).

INTERVENTIONS

Genotype was the independent variable, obtained by PCR of genomic DNA using TaqMan probes.

MAIN OUTCOME MEASURE

Elite athlete status with groups compared using χ 2 and odds ratio (OR).

RESULTS

The COMT rs4680 Met/Met (AA) genotype, Met allele possession, and Met allele frequency were lower in rugby athletes (24.8%, 74.6%, and 49.7%, respectively) than nonathletes (30.2%, 77.6%, and 54.0%; P < 0.05). The Val/Val (GG) genotype was more common in elite rugby athletes than nonathletes (OR 1.39, 95% confidence interval 1.04-1.86). No other polymorphism was associated with elite athlete status.

CONCLUSIONS

Elite rugby athlete status is associated with COMT rs4680 genotype that, acting pleiotropically, could affect stress resilience and behavioral traits during competition, concussion risk, and/or recovery from concussion. Consequently, assessing COMT rs4680 genotype might aid future individualized management of concussion risk among athletes.

Concussion-Associated Polygenic Profiles of Elite Male Rugby Athletes

Due to the high-velocity collision-based nature of elite rugby league and union, the risk of sustaining a concussion is high. Occurrence of and outcomes following a concussion are probably affected by the interaction of multiple genes in a polygenic manner. This study investigated whether suspected concussion-associated polygenic profiles of elite rugby athletes differed from non-athletes and between rugby union forwards and backs. We hypothesised that a total genotype score (TGS) using eight concussion-associated polymorphisms would be higher in elite rugby athletes than non-athletes, indicating selection for protection against incurring or suffering prolonged effects of, concussion in the relatively high-risk environment of competitive rugby. In addition, multifactor dimensionality reduction was used to identify genetic interactions. Contrary to our hypothesis, TGS did not differ between elite rugby athletes and non-athletes (p ≥ 0.065), nor between rugby union forwards and backs (p = 0.668). Accordingly, the TGS could not discriminate between elite rugby athletes and non-athletes (AUC ~0.5), suggesting that, for the eight polymorphisms investigated, elite rugby athletes do not have a more ‘preferable’ concussion-associated polygenic profile than non-athletes. However, the COMT (rs4680) and MAPT (rs10445337) GC allele combination was more common in rugby athletes (31.7%; p < 0.001) and rugby union athletes (31.8%; p < 0.001) than non-athletes (24.5%). Our results thus suggest a genetic interaction between COMT (rs4680) and MAPT (rs10445337) assists rugby athletes in achieving elite status. These findings need exploration vis-à-vis sport-related concussion injury data and could have implications for the management of inter-individual differences in concussion risk.

Sensation-Seeking and Impulsivity in Athletes with Sport-Related Concussion

PURPOSE OF REVIEW

Sport-related concussion (SRC) is a significant public health problem. Understanding the behavioral and personal factors that influence risk and incidence of SRC is critically important for appropriate care and management. Sensation-seeking and impulsivity have been posited to be two such factors that may be significantly associated with SRC. We performed a focused review of recent evidence of the relationships between sensation-seeking and impulsivity in athletes with SRC.

RECENT FINDINGS

While the research is relatively limited, extant findings demonstrate a significant relationship between sensation-seeking and contact sport participation and risk of prior and future SRC. Impulsivity appears to be common among athletes competing in high contact sports and may contribute to neural and functional brain changes following SRC; however, causal relationships between impulsivity, contact sport participation, and SRC have not been demonstrated. Both sensation-seeking and impulsivity are significantly associated with SRC in collegiate athletes. Interventions designed to ameliorate high levels of these constructs may prove to be beneficial avenues to reducing SRC risk and improving patient care and outcomes.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

Association of serotonin system-related genes with homicidal behavior and criminal aggression in a prison population of Pakistani Origin

The serotonin transporter (SLC6A4), 5-HT_2A (HTR2A) and 5-HT_2B (HTR2B) recepter genes, express proteins that are important regulators of serotonin reuptake and signaling, and thereby may contribute to the pathogenesis of aggressive criminal behavior. 370 sentenced murderers in Pakistani prisons and 359 men without any history of violence or criminal delinquency were genotyped for six candidate polymorphisms in SLC6A4, HTR2A and HTR2B genes. An association of higher expressing L/L and L_A/L_A variants of the 5-HTTLPR polymorphism was observed with homicidal behavior (bi-allelic: OR = 1.29, p = 0.016, tri-allelic: OR = 1.32, p = 0.015) and in the murderer group only with response to verbal abuse (OR = 2.11, p = 0.015), but not with other measures of self-reported aggression. L/L and L_A/L_A genotypes of the 5-HTTLPR polymorphism were associated with higher aggression scores on STAX1 scale of aggression compared to lower expressing genotypes (S/S, S/L_G, L_G/L_G) in prison inmates. No associations were apparent for other serotonergic gene polymorphisms analyzed. Using the Braineac and GTEx databases, we demonstrated significant eQTL based functional effects for rs25531 in HTTLPR and other serotonergic polymorphisms analyzed in different brain regions and peripheral tissues. In conclusion, these findings implicate SLC6A4* HTTLPR as a major genetic determinant associated with criminal aggression. Future studies are needed to replicate this finding and establish the biologic intermediate phenotypes mediating this relationship.

Can Genetic Testing Identify Talent for Sport?

Elite athlete status is a partially heritable trait, as are many of the underpinning physiological, anthropometrical, and psychological traits that contribute to elite performance. In recent years, our understanding of the specific genetic variants that contribute to these traits has grown, such that there is considerable interest in attempting to utilise genetic information as a tool to predict future elite athlete status. In this review, we explore the extent of the genetic influence on the making of a sporting champion and we describe issues which, at present, hamper the utility of genetic testing in identifying future elite performers. We build on this by exploring what further knowledge is required to enhance this process, including a reflection on the potential learnings from the use of genetics as a disease prediction tool. Finally, we discuss ways in which genetic information may hold utility within elite sport in the future, including guiding nutritional and training recommendations, and assisting in the prevention of injury. Whilst genetic testing has the potential to assist in the identification of future talented performers, genetic tests should be combined with other tools to obtain an accurate identification of those athletes predisposed to succeed in sport. The use of total genotype scores, composed of a high number of performance-enhancing polymorphisms, will likely be one of the best strategies in the utilisation of genetic information to identify talent in sport.

Age-specific associations among functional COMT Val158Met polymorphism, resting parasympathetic nervous control and generalized anxiety disorder

The functional Val¹⁵⁸Met polymorphism (rs4680) of the Catechol-O-Methyltransferase (COMT) gene has been implicated in generalized anxiety disorder (GAD); however, the underlying neural mechanisms remain unexamined. Recent evidence reveals that low resting parasympathetic (vagal) control is an endophenotypic predictor of anxiety, while the effect of COMT rs4680 differs at different ages. Thus, we examined whether the COMT Val¹⁵⁸Met variant could increase the risk of GAD through decreased resting parasympathetic nervous control in an age-specific manner. COMT rs4680 polymorphism was genotyped in 1,655 Han Chinese adults (1,142 healthy subjects and 513 patients with GAD; age: 20-65). High-frequency power (HF) of heart rate variability (HRV) was used to measure resting state parasympathetic nervous regulation. Non-genetic factors, such as gender, smoking status, medication use and comorbidity conditions, were treated as covariates. After adjusting for relevant covariates, there was a significant age x COMT genotype interaction on resting HF of HRV. In younger adults, Met allele carriers had a significantly lower HF index; however, older adults exhibited the opposite pattern, with Val/Val homozygotes exhibiting decreased HF values. Moreover, reduced HF-HRV is associated with increased risk of GAD. Finally, pathway analysis revealed a significant indirect effect of COMT on the risk of GAD via reduced resting HF-HRV, in the aforementioned age-dependent manner. Our findings are the first to demonstrate that COMT Val¹⁵⁸Met polymorphism is associated with risk of GAD via reduced resting parasympathetic nervous control, an age-specific risk pathway.

Association of serotoninergic pathway gene variants with elite athletic status in the Polish population

Genetic factors are known to influence sport performance. The aim of the present study was to assess genetic variants in genes coding for proteins potentially modulating activity of brain emotion centres in a group of 621 elite athletes (212 endurance, 183 power and 226 combat athletes) and 672 sedentary controls. Ten statistically significant variants were identified in genes encoding elements of serotoninergic, catecholaminergic and hypothalamic-pituitary-adrenal systems in different sport groups. Of those the rs860573 variant in the FEV gene coding for transcription factor exclusively expressed in neurons of the central serotonin system is the only one whose frequency significantly differentiates all the groups of athletes studied, regardless of discipline, from the controls (p = 0.000026). Our results support the hypothesis that genetic variants potentially affecting mental processes and emotions, particularly in the serotonergic pathway, also influence the predispositions to athletic performance.