Glutathione S-Transferase M1 and T1 genotypes in high-level swimmers : original research

Background : Variants genotypes of glutathione S-transferases (GSTs) lead to the inactive or less active form of the isoenzymes, which may alter protection against oxidative stress. Research question : Analyse the influence of GSTM1 and GSTT1 null polymorphisms on event expertise in high-level Portuguese swimmers. Methods : A group of high-level Portuguese swimmers (n=33, 20 males, 13 female; 18.84 ± 2.97 years), designated as Olympic candidates, were recruited and stratified into two groups, based on their current distance event of expertise: short distance swimmers, between 50 and 200 m and middle distance swimmers, between 400 and 1.500 m. A control group of healthy individuals (n=52, 38 males, 14 females; 20.5 ± 1.52 years) was also selected from the Portuguese population, with no background in swimming. Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR methods. Genotype distributions between groups were compared by Chi-Square test or Fisher's exact test where appropriate. Results : The genotype distribution of the GSTM1 of high-level swimmers is significantly different to the control group (X2=6.079, p=0.014). The distribution of the combined genotype M1-T1+, which reflects the presence of the GSTT1 protein in the absence of GSTM1 protein, is also statically different between high-level swimmers and controls (X2=4.664, p=0.0031). However, the analysis by race distance showed a significant higher frequency of the GSTM1 null genotype only on high-level short-distance swimmers when compared to controls (X2=6.180, p=0.013). Conclusions : The absence of GSTM1 protein production leads to a profile potentially more favourable to competitive swimming but particularly for swimming performance in shorter events.