Bradykinin type 2 receptor-9/-9 genotype is associated with triceps brachii muscle hypertrophy following strength training in young healthy men

Background: Bradykinin type 2 receptor (B2BRK) genotype was reported to be associated with changes in the left-ventricular mass as a response to aerobic training, as well as in the regulation of the skeletal muscle performance in both athletes and non-athletes. However, there are no reports on the effect of B2BRK 9-bp polymorphism on the response of the skeletal muscle to strength training, and our aim was to determine the relationship between the B2BRK SNP and triceps brachii functional and morphological adaptation to programmed physical activity in young adults. Methods: In this 6-week pretest-posttest exercise intervention study, twenty nine healthy young men (21.5 +/- 2.7 y, BMI 24.2 +/- 3.5 kg/m(2)) were put on a 6-week exercise protocol using an isoacceleration dynamometer (5 times a week, 5 daily sets with 10 maximal elbow extensions, 1 minute rest between sets). Triceps brachii muscle volumes were assessed by using magnetic resonance imaging before and after the strength training. Bradykinin type 2 receptor 9 base pair polymorphism was determined for all participants. Results: Following the elbow extensors training, an average increase in the volume of both triceps brachii was 5.4 +/- 3.4% (from 929.5 +/- 146.8 cm(3) pre-training to 977.6 +/- 140.9 cm3 after training, p<0.001). Triceps brachii volume increase was significantly larger in individuals homozygous for -9 allele compared to individuals with one or two +9 alleles (-9/-9, 8.5 +/- 3.8%; vs. -9/+9 and +9/+ 9 combined, 4.7 +/- 4.5%, p < 0.05). Mean increases in endurance strength in response to training were 48.4 +/- 20.2%, but the increases were not dependent on B2BRK genotype (-9/-9, 50.2 +/- 19.2%; vs. -9/+9 and +9/+ 9 combined, 46.8 +/- 20.7%, p > 0.05). Conclusions: We found that muscle morphological response to targeted training - hypertrophy - is related to polymorphisms of B2BRK. However, no significant influence of different B2BRK genotypes on functional muscle properties after strength training in young healthy non athletes was found. This finding could be relevant, not only in predicting individual muscle adaptation capacity to training or sarcopenia related to aging and inactivity, but also in determining new therapeutic strategies targeting genetic control of muscle function, especially for neuromuscular disorders that are characterized by progressive adverse changes in muscle quality, mass, strength and force production (e. g., muscular dystrophy, multiple sclerosis, Parkinson's disease).