Genetic Polymorphisms Associated with Muscle Damage and Exertional RhabdomyolysisFady Hijji1, Courtney Sprouse, bachelors of science2, Trevor Slezak3, Alexandra D'Agostini, BS3, Chika Okafor3, Eric Hoffman4,Heather Gordish-Dressman5, Laura L. Tosi, M.D.5, Joseph Devaney5, Priscilla M. Clarkson, Ph.D.6.1George Washington University School of Medicine, Elkridge, MD, USA, 2Childrens National Medical Center, Washington, DC,USA, 3George Washington University School of Medicine, Washington, DC, USA, 42Center for Genetic Medicine, ChildrensResearch Institute, Washington, DC, USA, 5Center for Genetic Medicine, Childrens Research Institute, Washington, DC, USA,6University of Massachusetts, Amherst, MA, USA.Disclosures:F. Hijji: None. C. Sprouse: None. T. Slezak: None. A. D'Agostini: None. C. Okafor: None. E. Hoffman: None. H. Gordish-Dressman: None. L.L. Tosi: None. J.Devaney: None. P.M. Clarkson: None.

Introduction: Skeletal muscle breakdown is a normal process that occurs with exercise and exertion. However, after bouts ofintensive and/or prolonged exercise, excessive muscle breakdown can occur resulting in exertional rhabdomyolysis (ER). Whileits clinical significance is well understood there is still a search for genetic susceptibility to elucidate the cause of the inter-individual risk for development of ER.We sought to determine the influence of Single Nucleotide Polymorphisms (SNPs) within the Collagen Type 5 Alpha 1 gene(COL5A1), Tumor Necrosis Factor alpha gene (TNFa), Solute Carrier Organic Anion Transporter 1B1 gene (SLCO1B1), Interleukin15 gene (IL15), Interleukin 15 Receptor Alpha gene (IL15RA) and Adenosine Monophosphate Deaminase 1 gene (AMPD1) on anindividuals susceptibility to ER due to their known influence on muscle catabolism. We hypothesized that individuals possessingcertain alleles at these particular loci would be more likely to exhibit higher Creatine Kinase (CK) levels before and after exerciseand thus have an increased risk of developing ER.Methods: DNA was isolated from 156 individuals (78 men and 78 women) between the ages of 18 and 40 years with no historyof weightlifting or muscle disease. These individuals underwent an exercise regimen consisting of two sets of twenty-fiveeccentric bicep curls and were assessed for their CK levels, muscle strength, and muscle soreness. The DNA was genotyped usinga Taqman allelic discrimination assay from Life Technologies (Carlsbad, CA); the following SNPs were analyzed; rs12722(COL5A1), rs2229135 (IL15RA), rs108330 (IL15), rs176027290 (AMPD1), rs4149056 (SLCO1B1), and rs1800629 (TNF).Genotyping was performed with standard thermal cycling conditions, with genotypes determined with 7900HT Real-Time PCRsystem. Hardy- Weinberg equilibrium (HWE) was determined using a 2 frequencies to those expected. Normality of eachquantitative trait was tested using the Shipiro-Wilk normality test. Mean measurements were compared to SNP genotypes usinganalysis of covariance (ANCOVA) methods, followed by Sidak post hoc analysis to control for multiple comparisons, adjusting forweight, age, and gender.Results: Higher CK levels were associated with women carrying a copy of the T allele for rs1800629 (TNF) (CC (N=65; BaselineCK=4.33 U.l-1 0.05), CT/TT (N=12; Baseline CK=4.60 U.l-1 0.11) p=0.037) and two copies of the G allele for rs2229135(IL15RA1) (GG (N=59; 4.43 U.l-1 0.05), GA/AA (N=19; 4.21 U.l-1 0.09) p=0.040). In addition, a non-synonymous variant in theSLCO1B1 gene (rs41490560) with the C allele was associated with increased strength loss and muscle soreness post-exerciseover time for every time period recorded. (Strength loss p=0.030; Soreness p=0.045)Discussion: The significantly increased levels of muscle strength loss and soreness post-exercise with individuals carrying the Callele of the SLCO1B1 polymorphism suggests there is increased muscle damage from muscle exertion. Previously, individualswith this allele have been seen to suffer from ER when taking statin drugs due to the genes effect on drug metabolism.However, these results could potentially illustrate the role of the SLCO1B1 polymorphism in ER without the influence of statindrugs. In addition, the higher baseline levels of CK in individuals with at least one copy of the T allele (TT/CT) at rs1800629 in theTNF- gene may reflect the negative effect of TNF- in decreasing protein synthesis and increasing muscle turnover. This SNPmay be responsible for increasing levels of TNF- which induces an increased rate of muscle degradation, leading to higher thannormal CK levels. IL15RA polymorphisms also have an effect in muscle metabolism, explaining the observed levels of baselineCK. These receptors have been seen to have a role in preventing degradation of skeletal muscle through inhibition of apoptoticsignaling pathways. The current study suggests that this SNP may be responsible for a mutation inhibiting its normal function,causing increased muscle atrophy and thus higher CK levels. The TNF- and IL15RA polymorphisms exhibited sexualdimorphisms as well, possibly due to females expressing higher levels of the gene products as seen in previous studies. Throughthese results, SLCO1B1 could potentially be used as a preemptive measure to identify those more susceptible to developing ER,with TNF- and IL15RA adding more specificity to the analysis of risk in women. More studies however need to be performed todetermine this correlation.Significance: This is one of few studies that has attempted to discover the genetic basis behind an individual's susceptibility toexertional rhabdomyolysis. The correlations between these certain genetic polymorphisms and muscle damage could be used todevelop preemptive genetic screenings for those undergoing intense physical activity, such as those in military training camps.Acknowledgments: This study is funded in part by the National Institutes of Health National Center for Research Resources

(1K23 RR024467-01), the Childrens National Medical Center General Clinical Research Center (5-M01-RR-020359-02), the DC-Baltimore Research Center on Child Health Disparities (5P20MD00165), NICHD/NINDS 5R24HD050846-08: NCMRR-DC CoreMolecular and Functional Outcome Measures in Rehabilitation Medicine.References: Dixon, D., R. Golderberg, N. Schneiderman, A. Delamater. 2004. Gender Differences in TNF-a levels among obese vsnonobese Latino children. European Journal of Clinical Nutrition, 58(4) 696-99.Landau, ME, K. Kennedy, P. Deuster, WW. Campbell. 2012. Exertional rhabdomyolysis: a clinical review with a focus on geneticinfluences. Journal of Clinical Neuromuscular Disease, 13(3): 122-36.Liu, D., E. Metter, L. Ferrucci, S. Roth. 2008. TNF promoter polymorphisms associated with muscle phenotypes in humans.Journal of Applied Physiology, 105(3): 859-67.Pistilli E., P. Siu, S. Alway. 2007. Interleukin-15 responses to aging and unloading-induced skeletal muscle atrophy. Am J PhysiolCell Physiol.: 292(4):1298-1304.Yamin, C., JA. Duarte, JM. Oliveira, O. Amir, M. Sagiv, N. Eynon, RE. Amir. 2008. IL6 (-174) and TNFA (-308) promoterpolymorphisms are associated with systemic creatine kinase response to eccentric exercise. European Journal of AppliedPhysiology, 104(3): 579-86.

ORS 2014 Annual MeetingPoster No: 0205