Association between NOS3 intron 4 VNTR variant and sports performance

Aim: Evidence shows the involvement of Nitric oxide (NO) in glucose metabolism, which is glucose uptake in human skeletal muscle at the time of exercise, controlling function and structure of skeletal muscle, conversion of skeletal muscle fiber type, production of mitochondrial ATP, and uptake of oxygen in skeletal muscles, all necessary for anaerobic and aerobic performance. Endothelial nitric oxide synthase (NOS3) enzyme synthesizes NO. The main purpose of this study was to investigate whether the NOS3 gene variable number of tandem repeats (VNTR) variant affected athletic performance in the Turkish population. Material and Methods: This is a prospective single-center cross-sectional study. One hundred thirty-six Turkish athletes and 150 sedentary individuals as controls were included in the study. The intron-4 27-bp VNTR variant of NOS3 genotype and allele frequencies were analyzed with polymerase chain reaction (PCR) analysis. Results: There was a significant difference between the athletes and the control group in the genotype distribution of the NOS3 VNTR variant. We found that the NOS3 VNTR 4a/4a genotype significantly increased in athletes compared with controls (X2:10.862, p = 0.004). A statistically significant association was observed between the athletes and the controls in terms of 4b/4b + 4a/4b genotype vs 4a/4a genotypes (p = 0.011, 95% CI: 0.0366 -0.7915). There was no significant difference between the groups in the NOS3 VNTR allele distribution (p>0.05). Discussion: This study gives evidence of an association between the NOS3 variant and sports performance. More studies should focus on the genetic effect of increased performance to confirm these findings.