Do Heat Shock Protein 70-2 and Interleukin-6 Genes Contribute to Exercise-Induced Increases in Creatine Kinase?

Abstract

Strenuous exercise can provoke a marked increase in creatine kinase (CK), an indicator of muscle damage. Why some persons develop extremely high levels of CK in response to exercise is unknown, but clearly genetics serves a role. Two genes postulated to be important in the CK response to exercise include heat shock protein 70-2 (HSP70-2) and interleukin-6 (IL-6). PURPOSE: To assess the influence of selected single nucleotide polymorphisms (SNP) in the IL-6 (-C174G) and HSP70-2 (+A1538G) genes on baseline and exerciseinduced increases in CK. METHODS: Healthy, physically active participants (n=138) underwent an exercise step test for 5 min. with a backpack weighted at 30% of their body weight, followed by 15 squats. Blood was taken before, immediately after, 48 and 72 hrs after the step test for assessment of serum CK and isolation of DNA. SNPs in the HSP70-2 and IL-6 genes were evaluated by standard polymerase chain reaction procedures in blood samples. RESULTS: Participants were categorized into two groups based on their CK response. High responders (HR) had = 230 μU/L increases in CK at 48 or 72 hours post exercise relative to baseline; all others were normal responders (NR): 19 of 138 (14.5%) were HR. The percent of persons with the GG genotype for the IL-6 SNP was significantly higher in HR (68.4%) relative to NR (42.0%; p = 0.03). In addition, serum CK levels at 48 and 72 hours were significantly higher in GG as compared to C+ genotypes (IL-6), and GG as compared to AG genotypes (HSP70-2), but baseline CK levels did not differ when analyzed by ANOVA.TableCONCLUSIONS: These data suggest that HSP70-2 and IL-6 genes may serve a role in individual susceptibility to exertional muscle injury, as judged by CK responses to exercise. Supported by USU Grant R091CE.